Dr. Poul Erik Hansen, Dr. Science - Roskilde University - Professor emiritus

Dr. Poul Erik Hansen

Dr. Science

Roskilde University

Professor emiritus

Roskilde | Denmark

Main Specialties: Chemistry

Additional Specialties: NMR

ORCID logohttps://orcid.org/0000-0003-4751-9910


Top Author

Dr. Poul Erik Hansen, Dr. Science - Roskilde University - Professor emiritus

Dr. Poul Erik Hansen

Dr. Science
Introduction

Short CURRICULUM VITAE
Name: Poul Erik Hansen, Born October 30, 1945
Jan. 1970 Thesis, University of Århus: "Preparation of crowded PAH and in¬vestiga¬- tion thereof by means of NMR, IR, UV and MS spectroscopy."
Febr. 1970: Visit at Laboratoire Chimie Organique, Université Libre, Bruxelles, Belgium, Prof. R.H.Martin
1971-1973: Research Fellow, Danish Natural Science Research Council
1973-1974: Royal Society Exchange Fellow. Visit at Division of Molecular Phar¬ macology, NIMR, Mill Hill, England, Dr. J.Feeney.
Aug. 1974: Ph. D. Thesis:"13C, 19F and 1H NMR studies of some polycyclic aromatic hydrocarbons. Synthesis of 13C enriched compounds."
1974-1977: Senior Research Fellow
1976-1977: Visit at Department of Biochemistry, University of Alberta, Edmonton, Canada, Prof. B.D.Sykes.
Sept. 1977: Award from the Ole Rømer Foundation in recognition of contribution to the development of 13C NMR spectroscopy.
Febr. 1978: Assistant prof. of Chemistry, Department of Life Sciences and Chemi¬ stry, University of Roskilde
Aug. 1979: Associate professor of chemistry
June-Sept. 1984: Visiting professor, Department of Biochemistry , University of Alberta, Edmonton, Canada
Aug.88-June 1989: Visiting professor Department of Biochemistry, University of New and Jan.90 and 91 South Wales, Sydney, Australia
Jan. 1988-95: Chairman, Danish Society for Molecular Spectroscopy
Jan. 1992: Visiting professor, Department of Biochemistry, Sydney University, Sydney, Australia
Nov. 1995-98 President of the Danish Chemical Society
Jan. 1996 Full professor in Bio-organic Nuclear Magnetic Resonance Spectroscopy, Department of Life Sciences and Che¬mi¬stry, Roskilde Universi¬ty
Jan. 1997 Dr. Science , Roskilde University
Dec. 1997 Member of the Danish Academy for Natural Science
Sept. 1997 Member of International Advisory Board for Horizons H-bond meetings.
Sept. 2001 Member of the advisory board of Magnetic Resonance in Chemistry
Sept. 2001 Vice president International Advisory Board for H-bond meetings
Dec. 2002 Advisor For Centre of excellence ”Centre for Photoactive Materials”.
Sept. 2003-6 President International Board for Horizons H-bond Research
2004 Honorary guest professor Technical University of Shandong, Zibo, China
2005 Guest editor Current Organic Chemistry
2007 Honorary guest professor Three Gorges University, China
2007 Advisory Board member Open Spectroscopy Journal ,Open MR Journal
2008 Knight of Dannebrog
2008 Danish coordinator COST program SIBAE
2010 Danish member of NORDSIR committee
2012 Guest Editor Molecules
2014 Honorary member of the Polish Chemical Society
2015 Guest professor University of Copenhagen
2017 Knight of Dannebrog 1st order

Primary Affiliation: Roskilde University - Roskilde , Denmark

Specialties:

Additional Specialties:


View Dr. Poul Erik Hansen’s Resume / CV
Metrics

282

Publications

588

Profile Views

393

Reads

130

PubMed Central Citations

Education
Jan 1974
Aarhus Universitet
Ph.d. (Lic.scient)
Experience
Jan 1996
Roskilde Universitet
Professor
Roskilde University
Top co-authors
Fritz Duus
Fritz Duus

Roskilde University

6
Fadhil S Kamounah
Fadhil S Kamounah

Roskilde University

5
Jens Spanget-Larsen
Jens Spanget-Larsen

Roskilde University

4
Mike P Williamson
Mike P Williamson

University of Sheffield

3
Wei Zhang
Wei Zhang

University of Minnesota Twin Cities

3
Torben Lund
Torben Lund

Copenhagen University Hospital

3
Mariusz Pietrzak
Mariusz Pietrzak

Warsaw University of Technology

2

Publications

282Publications

393Reads

130PubMed Central Citations

Structure of a new usnic acid derivative from a deacylating Mannich reaction: NMR studies supported by theoretical calculations of chemical shifts.

Magn Reson Chem 2018 Nov 2;56(11):1094-1100. Epub 2018 Jul 2.

Department of Science and Environment, Roskilde University, Roskilde, Denmark.

View Article
November 2018
3 Reads
1.18 Impact Factor

NMR, MP2, and DFT study of thiophenoxyketenimines (o-thio-Schiff bases): Determination of the preferred form.

Magn Reson Chem 2018 Mar 29;56(3):172-182. Epub 2017 Nov 29.

Department of Science and Environment, Roskilde University, Roskilde, Denmark.

View Article
March 2018
7 Reads
1.18 Impact Factor

The possible tautomerism of the potential rotary switch 2-(2-(2-Hydroxy-4-nitrophenyl)hydrazono)-1-phenylbutane-1,3-dione

Dyes and Pigments

The title compound is potentially tautomeric and its tautomerism was studied by means of molecular spectroscopy (1H and 13C NMR and UV–Vis) in DMSO as well as by quantum chemical calculations (M06-2X/TZVP). The detailed assignment of the NMR signals supported by the theoretical calculations clearly shows that the previous interpretation, available in the literature, about the coexistence of two tautomeric forms is not correct. The compound exists as major and minor isomer of a single tautomeric form. In addition, a 2-methoxy derivative (the OH group replaced by a methoxy group) is also investigated and show similar trends.

https://forskning.ruc.dk/en/publications/33946c36-2643-462e-8661-8aa939dd741d

View Article
2017
2 Reads

Reappraisal of the genetic diversity and pharmacogenetic assessment of CES1

Pharmacogenomics

The CES1 gene encodes a hydrolase that metabolizes important drugs. Variants generated by exchange of segments with CES1P1 complicate genotyping of CES1. Using a highly specific procedure we examined DNA samples from 200 Caucasians and identified 46 single nucleotide variants (SNVs) in CES1 and 21 SNVs in CES1A2, a hybrid composed of CES1 and CES1P1. Several of these SNVs were novel. The frequencies of SNVs with a potential functional impact were below 0.02 suggesting limited pharmacogenetic potential for CES1 genotyping. In silico PCR revealed that the majority of the primer pairs for amplification of CES1 or CES1A2 in three previous studies lacked specificity, which partially explains a limited overlap with our findings.

https://forskning.ruc.dk/en/publications/3b7bde0e-d1b8-4de1-b863-d19005fd9b77

View Article
2017
2 Reads

Nomenclature for alleles of the human carboxylesterase 1 gene

Pharmacogenetics and Genomics

The carboxylesterase 1 gene (CES1) in humans encodes a hydrolase, which is implicated in the metabolism of several commonly used drugs 1. This gene is located on chromosome 16 with a highly homologous pseudogene, CES1P1, in its proximity. A duplicated segment of CES1 replaces most of CES1P1 in some individuals, thus leading to the formation of a hybrid gene, which has its 5′ end, exon 1, and a portion of intron 1 from CES1P1 and the rest from CES12. This hybrid gene has been referred to as CES1A2 to distinguish it from the original copy of CES1, which is also known as CES1A12,3. There are two structural haplotypes of CES1, probably reflecting a double overcrossing event 2. Each of them carries one copy of CES1A1 in addition to one copy of either CES1P1 or CES1A2. Hence, the presence of CES1A2 in some individuals defines a structural haplotype different from the haplotype carrying CES1P1. Several haplotypes of CES1A2 have been identified on the basis of single nucleotide variations in its promoter including one major haplotype and several minor haplotypes 4. One of the minor CES1A2 haplotypes has two overlapping Sp1 sites that confers significantly higher transcriptional activity compared with the major haplotype of CES1A24,5. A previous study reported two variants of CES1A1 in which exon 1, with or without its flanking sequences, has been replaced by the corresponding CES1P1 segments 6,7. These were named CES1A1c and CES1A1b, respectively, to distinguish them from the CES1 reference sequence, which was called CES1A1a. In recent studies, CES1A2 has been referred to as CES1P1VAR8,9, whereas CES1A1c and CES1A1b or a closely related CES1A1b variant were denoted CES1VAR and CES1SVAR, respectively 10. The designations CES1VAR and CES1SVAR have the advantage that they are based on the name approved by the HUGO Gene Nomenclature Committee, CES1, thus avoiding the use of CES1A1. However, since these two CES1 variants were deposited in GenBank under the names CES1A1b and CES1A1c, a search for CES1SVAR and CES1VAR in this database comes up without results. Further, we believe that the new nomenclature for CES1A2 raises concerns as it assumes that CES1A2 and CES1P1 are representatives of the same gene, an assumption that may lead to misconceptions. Indeed, several studies have genotyped the CES1P1 variant −816A>C without discriminating the A at this polymorphic site from the A at the corresponding position in CES1A29,11,12. This approach is questionable as the A at position −816 in CES1A2 appears to be nonpolymorphic and resides on a haplotype different from the haplotype, which carries CES1P16. For example, it may lead to an overestimation of the frequency of the CES1P1 −816A allele in populations with a high frequency of CES1A2 such as Asian populations 2. The lack of distinction between the A allele at position −816 in CES1P1 and the corresponding but nonpolymorphic A in CES1A2 may also be of concern from a functional point of view. One such concern is that the CES1A2 haplotype with the overlapping Sp1 sites and high transcriptional activity has the potential to produce large quantities of functional enzyme 4,5, whereas CES1P1 has no such potential 2. Moreover, evidence has been provided that CES1A2 influences the pharmacokinetics of irinotecan 6, although the impact of having CES1A2 generally appears to be low 8,13. The formation of hybrids consisting of a gene and a related pseudogene has been reported for other genes than CES1. This includes the hybrids of the gene encoding cytochrome P450 2D6 (CYP2D6) and pseudogene CYP2D7, that is, the so-called CYP2D7/D6 hybrids 14,15. These are categorized as CYP2D6 variants and not as variants of pseudogene CYP2D716.

https://forskning.ruc.dk/en/publications/8955df4a-04fe-40a7-9102-9ec13566ffeb

View Article
2017
2 Reads

Multi-step rearrangement mechanism for acetyl cedrene to the hydrocarbon follower

Chemistry of Natural Compounds

Conversion of acetyl cedrene (2) to its follower (3) using acetic anhydride and polyphosphoric acid involves a multi-step cationic molecular rearrangement, which is consistent with deuteriation and 1-13C labeling studies of acetyl cedrene. The key step involves cyclopropylcarbinyl cation-cyclopropylcarbinyl cation rearrangement.

https://forskning.ruc.dk/en/publications/d20c5712-ccf3-41db-98a0-885f48a215f4

View Article
2017
2 Reads

4-Carboxyl-2,6-dinitrophenylazohydroxynaphthalenes tautomerism NMR re-explained and other methods verified

Dyes and Pigments

In two consecutive studies the tautomerism in 4-((2-hydroxynaphthalen-1-yl)diazenyl)-3,5-dinitrobenzoic acid and the structurally similar 1-((2-nitrophenyl)diazenyl)naphthalen-2-ol has been considered from viewpoint of theoretical chemistry, UV–Vis spectroscopy and NMR. Although the theoretical data (at M062X level) show that both compounds exist only as a keto tautomer, the experiment proves existence of the enol form. The difference in the results obtained by UV–Vis spectroscopy and NMR requires a deeper consideration and verification of the NMR approach, which is based on using model compounds to provide the NMR signal pattern of individual tautomers.

https://forskning.ruc.dk/en/publications/d88d529a-1edf-463d-8fbb-753764149fbc

View Article
2017
2 Reads

Tautomerism and biological activity of beta-diketones, triketones, beta,ketoesters and beta-ketoamides. A Mini Review.

Wiadomosci Chem. 2017, 71, 428-446

Wiadomosci Chem.

The review deals with beta-diketones, beta-ketoester, beta-ketoamides, triketones, their tautomerism and biological activity. In addition, it covers briefly methods to detect tautomerism in particular NMR and deuterium isotope effects on chemical shifts, both primary and secondary. In addition, a number of typical systems are treated such as usnic acid, tetracyclines, piroxicam, curcurmines, humulones, acyltetramic acids and quinolone 3-esters.

View Article
December 2017
6 Reads

Dynamics of Excited State Proton Transfer in Nitro Substituted 10-Hydroxybenzo[h]quinolines

Physical Chemistry Chemical Physics

The ground state tautomerism and excited state intramolecular proton transfer (ESIPT) of 10-hydroxybenzo[h]quinoline (HBQ) and its nitro derivatives, 7-nitrobenzo[h]quinolin-10-ol (2) and 7,9-dinitrobenzo[h]quinolin-10-ol (3), have been studied in acetonitrile using steady state as well as time dependent spectroscopy and quantum-chemical calculations. In addition to the enol form absorbance in the range 360–390 nm, the absorption spectra of 2 and 3 exhibit a red shifted band at ∼450 nm. Chemometric data processing, based on individual band decomposition, allowed us to estimate the position of the ground state enol–keto tautomeric equilibrium (ΔG values of 1.03 and 0.62 kcal mol−1 respectively for 2 and 3). The fluorescence stems from the keto form even if the enol form is optically excited as proven by the shape of the excitation spectra indicating that ESIPT takes place. The Stokes shift of the substituted compounds is substantially lower compared to HBQ, which follows from the fact that the substitution occurs in the formal cyclohexa-2,4-dienone moiety and leads to a decrease of the HOMO level of the keto tautomer. The pump–probe experiments show that in the nitro substituted HBQs 2 and 3 ESIPT occurs with a time constant of 0.89 ps and 0.68 ps, respectively. In both cases a mixture of the enol and proton transfer forms is optically excited. The enol form exhibits then the ESIPT and subsequently both fractions take the same relaxation path. We propose that in 2 and 3 the ESIPT path exhibits a potential energy barrier resulting in an incoherent rate governed process while in HBQ the ESIPT proceeds as a ballistic wavepacket motion along a path without significant barriers. The theoretical calculations (M06-2X/TZVP) confirm the existence of a barrier in the ground and excited states as result of the substitution.

https://forskning.ruc.dk/en/publications/b6984d99-baad-4a12-992b-44a8d8d83c6f

View Article
October 2017
2 Reads

Greener Friedel-Crafts Acylation using Microwave-enhanced reactivity of Bismuth Triflate in the Friedel-Crafts Benzoylation of Aromatic Compounds with Benzoic Anhydride

Chemistry Select

An efficient and facile bismuth trifluoromethanesulfonate-catalyzed benzoylation of aromatic compounds using benzoic anhydride under solvent-free microwave irradiation has been developed. The microwave-assisted Friedel-Crafts benzoylation results in good yields within short reaction times. Bismuth triflate is easily recovered and reused for several times without significant loss of catalytic activity

https://forskning.ruc.dk/en/publications/2e6654dd-18c2-4013-acda-4a7c28ccd339

View Article
January 2017
2 Reads

Efficient Friedel-Crafts benzoylation of aniline derivatives with 4-fluorobenzoyl chloride using copper triflate in the synthesis of aminobenzophenones

Synthetic Communications

An efficient pathway for the synthesis of the aminobenzophenone
derivatives via Friedel–Crafts benzoylation using copper triflate as
catalyst is proposed. New derivatives are synthesized. The copper
triflate could be easily recovered and reused without loss of catalytic
activity. Both the use of ionic liquids and microwave heating turned
out to be fruitful.

https://forskning.ruc.dk/en/publications/9d37ff0f-6072-44e8-a363-7c2893363703

View Article
2016
2 Reads

A Reinvestigation of the Ionic Liquid Diisopropylethylammonium Formate by NMR and DFT Methods.

J Phys Chem B 2016 11 21;120(43):11279-11286. Epub 2016 Oct 21.

Department of Science and Environment, Roskilde University , DK-4000 Roskilde, Denmark.

View Article
November 2016
9 Reads

A Reinvestigation of the Ionic Liquid Diisopropylethylammonium Formate by NMR and DFT Methods

The Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical

The complex between diisopropylethylamine (DIPEA) and formic acid has been reinvestigated. Mixing the compounds in the ratio 1:1 leads to a phase separation in which the upper phase is DIPEA, the lower phase is the “ionic liquid” named DIPEF. A combined NMR and DFT study shows that the lower phase primarily is formic acid:formate and diisopropyl-ammonium ions in the ratio 2:1 (acid:base) plus the formic acid dimer. Addition of more acid leads to more and more of the acid dimer. The proton transfer in the system is 65-80%. The structural picture presented in this paper is very different from that presented elsewhere. However, the present picture should be considered using acids and bases with a pKa difference less than 8. The formic acid content in the DIPEF ionic liquid causes desorption of the dye-sensitized solar cell (DSC) dye N719 from the photo anode and DIPEF is therefore not a suitable electrolyte for DSCs.

https://forskning.ruc.dk/en/publications/2898af56-eefb-4f82-9ed6-0ee60550fbbd

View Article
October 2016
2 Reads

An efficient and green method for regio- and chemo-selective Friedel–Crafts acylations using a deep eutectic mixture ([CholineCl][ZnCl2]3)

RSC Advances

[CholineCl][ZnCl2]3, a deep eutectic solvent between choline chloride and ZnCl2, has been used as a dual function catalyst and green solvent for the Friedel–Crafts acylation of aromatic compounds instead of using the moisture-sensitive Lewis acids and volatile organic solvents. The reactions are performed with high yields under microwave irradiation with short reaction times for the synthesis of ketones. Interestingly, indole derivatives are regioselectively acylated in the 3-position under mild conditions with high yields without NH protection. Three new ketone products are synthesized. [CholineCl][ZnCl2]3 is easily synthesized from choline chloride and zinc chloride at a low cost, with easy purification and environmentally benign compounds. [CholineCl][ZnCl2]3 can be reused up to five times without loss of catalytic activity, making it ideal in industrial processes.

https://forskning.ruc.dk/en/publications/919274d8-b578-4468-8151-b38f3a6867bd

View Article
August 2016
2 Reads

Structural studies on Mannich bases of 2-Hydroxy-3,4,5,6-tetrachlorobenzene. An UV, IR, NMR and DFT study. A mini-review

Journal of Molecular Structure

Mannich bases of 2-Hydroxy-3,4,5,6-tetrachlorobenzene are chosen as an exemplary case for tautomeric Mannich bases. Molecular structures are calculated. OH stretching frequencies are rationalized based on DFT calculations. Intrinsic deuterium isotope effects on 13C chemical shifts in the M-form are estimated based on OH bond lengths. The observed deuterium isotope effects on 13C chemical shifts are demonstrated to be largely of equilibrium type except at ambient temperatures.

https://forskning.ruc.dk/en/publications/e93a4ee4-cfe5-4d49-b925-7d14fac72dcd

View Article
April 2016
2 Reads

Greener Friedel-Crafts Acylations

Green and Sustainable Chemistry Conference 2016, Berlin, Germany, 03/04/2016

https://forskning.ruc.dk/en/publications/e3ab195e-a672-4aae-92d6-a27941d2be1a

View Article
April 2016
4 Reads

Individualization of treatments with drugs metabolized by CES1: combining genetics and metabolomics.

Pharmacogenomics 2015 21;16(6):649-65. Epub 2015 Apr 21.

Institute of Biological Psychiatry, Mental Health Centre Sct. Hans, Copenhagen University Hospital, 2 Boserupvej, DK-4000 Roskilde, Denmark.

View Article
February 2016
6 Reads
6 PubMed Central Citations(source)
3.22 Impact Factor

10-hydroxybenzo[h]quinoline: Switching between single and double-well proton transfer through structural modifications

RSC Advances

Proton transfer in 10-hydroxybenzo[h]quinoline (HBQ) and structurally modified compounds was investigated experimentally (steady state UV-Vis absorption and emission spectroscopy, NMR and advanced chemometric techniques) and theoretically (DFT and TD-DFT M06-2X/TZVP calculations) in the ground and excited singlet state. We observed that the incorporation of electron acceptor substituents on position 7 of the HBQ backbone led to appearance of a keto tautomer in ground state and changes in the excited state potential energy surface. Both processes were strongly solvent dependent. In the ground state the equilibrium could be driven from the enol to the keto form by change of solvent. The theoretical calculations explain the substitution-determined transition from a single- to a double-well proton transfer mechanism

https://forskning.ruc.dk/en/publications/91cbeb1b-5458-4be1-a42b-74779b6f81db

View Article
2015
2 Reads

Tautomeric transformations of piroxicam in solution: a combined experimental and theoretical study

RSC Advances

Piroxicam tautomerism was studied in solution by using UV-Vis spectroscopy, NMR measurements and advanced chemometrics. It has been found that in ethanol and DMSO the enol-amide tautomer is present mainly as a sandwich type dimer. The addition of water leads to distortion of the aggregate and to gradual shift of the equilibrium towards the zwitterionic tautomer. Quantitative data for the aggregation and the tautomeric equilibria are presented. Quantum chemical calculations (M06-2X/TZVP) have been used to explain stability of the tautomers as a function of the solvent and concentration.

https://forskning.ruc.dk/en/publications/3fc1dd5d-fe95-44f8-8f4b-7e622020eb8e

View Article
2015
2 Reads

Individualization of treatments with drugs metabolized by CES1

Pharmacogenomics

CES1 is involved in the hydrolysis of ester group-containing xenobiotic and endobiotic compounds including several essential and commonly used drugs. The individual variation in the efficacy and tolerability of many drugs metabolized by CES1 is considerable. Hence, there is a large interest in individualizing the treatment with these drugs. The present review addresses the issue of individualized treatment with drugs metabolized by CES1. It describes the composition of the gene encoding CES1, reports variants of this gene with focus upon those with a potential effect on drug metabolism and provides an overview of the protein structure of this enzyme bringing notice to mechanisms involved in the regulation of enzyme activity. Subsequently, the review highlights drugs metabolized by CES1 and argues that individual differences in the pharmacokinetics of these drugs play an important role in determining drug response and tolerability suggesting prospects for individualized drug therapies. Our review also discusses endogenous substrates of CES1 and assesses the potential of using metabolomic profiling of blood to identify proxies for the hepatic activity of CES1 that predict the rate of drug metabolism. Finally, the combination of genetics and metabolomics to obtain an accurate prediction of the individual response to CES1-dependent drugs is discussed

https://forskning.ruc.dk/en/publications/d86e0f7c-4f80-41c8-a8cb-95ecf6f29bfa

View Article
2015
2 Reads

Indium triflate in 1-isobutyl-3-methylimidazolium dihydrogenphosphate: an efficient and green catalytic system for Friedel-Crafts acylation

Tetrahedron Letters

Indium triflate in the ionic liquid, 1-isobutyl-3-methylimidazolium dihydrogen phosphate ([i-BMIM]H2PO4), was found to show enhanced catalytic activity in the Friedel–Crafts acylation of various aromatic compounds with acid anhydrides. The catalytic system was easily recovered and reused without a significant loss of activity

https://forskning.ruc.dk/en/publications/f38b9de6-63d0-451b-b660-319964e0c439

View Article
2015
2 Reads

Determination of the Tautomeric Equilibria of Pyridoyl Benzoyl -Diketones in the Liquid and Solid State through the use of Deuterium Isotope Effects on 1H and 13C NMR Chemical Shifts and Spin Coupling Constants

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy

The tautomeric equilibria for 2-pyridoyl-, 3-pyridoyl-, and 4-pyridoyl-benzoyl methane have been investigated using deuterium isotope effects on 1H and 13C chemical shifts both in the liquid and the solid state. Equilibria are established both in the liquid and the solid state. In addition, in the solution state the 2-bond and 3-bond J(1H–13C) coupling constants have been used to confirm the equilibrium positions. The isotope effects due to deuteriation at the OH position are shown to be superior to chemical shift in determination of equilibrium positions of these almost symmetrical -pyridoyl-benzoyl methanes. The assignments of the NMR spectra are supported by calculations of the chemical shifts at the DFT level. The equilibrium positions are shown to be different in the liquid and the solid state. In the liquid state the 4-pyridoyl derivative is at the B-form (C-1 is OH), whereas the 2-and 3-pyridoyl derivatives are in the A-form. In the solid state all three compounds are on the B-form. The 4-pyridoyl derivative shows unusual deuterium isotope effects in the solid, which are ascribed to a change of the crystal structure of the deuteriated compound

https://forskning.ruc.dk/en/publications/75a329c5-b7c0-4e5b-b0ec-4b3a3ebf8fbb

View Article
2015
2 Reads

An efficient and green synthesis of 1-indanone and 1-tetralone via intramolecular Friedel-Crafts acylation reaction

Asian Journal of Organic Chemistry

Metal-triflate-catalyzed intramolecular Friedel–Crafts acylation of 3-arylpropanoic and 4-arylbutanoic acids in triflate-anion ionic liquids under monomodal microwave irradiation is reported. The environmentally benign synthetic procedure allows the formation of cyclic ketones in good yields within a short reaction time. The catalytic metal triflate in triflate-anion ionic liquids can be easily recovered and reused several times without significant loss of the catalytic performance.

https://forskning.ruc.dk/en/publications/f065289e-60e8-4f68-9d15-62b4d19183d2

View Article
2015
2 Reads

A simple, effective, green method for regioselective 3-acylation of unprotected indoles

Molecules

A fast and green method is developed for regioselective acylation of indoles in the 3-position without the need for protection of the NH position. The method is based on Friedel-Crafts acylation using acid anhydrides. The method has been optimized, and Y(OTf)3 in catalytic amounts is found to be the best catalyst together with the commercially available ionic liquid [BMI]BF4 (1-butyl-3-methylimidazolium tetrafluoro-borate) as solvent. The reaction is completed in a very short time using monomode microwave irradiation. The catalyst can be reused up to four times without significant loss of activity. A range of substituted indoles are investigated as substrates, and thirteen new compounds have been synthesized

https://forskning.ruc.dk/en/publications/d729dc4b-2875-43a9-93ee-b36719f0a41d

View Article
2015
2 Reads

4-Hydroxy-1-naphthaldehydes: proton transfer or deprotonation

Physical Chemistry Chemical Physics

A series of naphthaldehydes, including a Mannich base, have been investigated by UV-Vis spectroscopy, NMR and theoretical methods to explore their potential tautomerism. In the case of 4-hydroxy-1-naphthaldehyde concentration dependent deprotonation has been detected in methanol and acetonitrile. For 4-hydroxy-3-(piperidin-1-ylmethyl)-1-naphthaldehyde (a Mannich base) an intramolecular proton transfer involving the OH group and the piperidine nitrogen occurs. In acetonitrile the equilibrium is predominantly at the OH-form, whereas in methanol the proton transferred tautomer is the preferred form. In chloroform and toluene, the OH form is completely dominant. Both 4-hydroxy-1-naphthaldehyde and 4-methoxy-1-naphthaldehyde (fixed enol form) show dimerization in the investigated solvents and the crystallographic data, obtained for the latter, confirm the existence of a cyclic dimer

https://forskning.ruc.dk/en/publications/600e4de1-bcb8-4cef-b634-360a51c244b2

View Article
2015
2 Reads

A Simple, Effective, Green Method for the Regioselective 3-Acylation of Unprotected Indoles.

Molecules 2015 Oct 27;20(10):19605-19. Epub 2015 Oct 27.

Department of Organic Chemistry, Faculty of Chemistry, University of Science, Vietnam National University, Ho Chi Minh City 70000, Vietnam.

View Article
October 2015
5 Reads
2.42 Impact Factor

Comments on “Spectroscopic studies of keto–enol tautomeric equilibrium of azo dyes” by M. A. Rauf, S. Hisaindee and N. Saleh, published in RSC Advances 2015, 5, 18097-18110 as a Review Article

RSC Advances

The paper mentioned in the title contains inaccuracies and misleading interpretations that seriously misrepresent basic knowledge about tautomerism in azo dyes. Therefore, we aim in this Letter to correct the most obvious mistakes, to address the misrepresentation of the main issues of tautomerism, and to give a better understanding of the basic principles of the tautomerisation process

https://forskning.ruc.dk/en/publications/7c5701d4-b407-4d7e-8513-e1f205ab7d79

View Article
August 2015
2 Reads

Chemical constituents from Sonneratia ovata Backer and their in vitro cytotoxicity and acetylcholinesterase inhibitory activities.

Bioorg Med Chem Lett 2015 Jun 11;25(11):2366-71. Epub 2015 Apr 11.

Department of Organic Chemistry, VNUHCM-University of Science, 227 Nguyen Van Cu Str., Dist. 5, Ho Chi Minh City, Vietnam. Electronic address:

View Article
June 2015
11 Reads
2.42 Impact Factor

Chemical Constituents from Sonneratia ovata Backer and their in vitro Cytotoxicity and Acetylcholinesterase Inhibitory Activities

Bioorganic & Medicinal Chemistry Letters

Sonneratia ovata Backer, Sonneratiaceae, is a widespread plant in mangrove forests in Vietnam, Cambodia, Thailand, Indonesia. Sonneratia ovata’s chemical composition remains mostly unknown. Therefore, we now report on the structural elucidation of three new phenolics, sonnerphenolic A (1), sonnerphenolic B (2), and sonnerphenolic C (23), a new cerebroside, sonnercerebroside (3) together with nineteen known compounds, including nine lignans (5–13), two steroids (14, 15), two triterpenoids (16, 17), three gallic acid derivatives (18–20), two phenolic derivatives (4, 22) and a 1-O-benzyl-β-d-glucopyranose (21) isolated from the leaves of Sonneratia ovata. Their chemical structures were established by spectroscopic data, as well as high resolution mass spectra and comparison with literature data. The in vitro acetylcholinesterase (AChE) inhibition and cytotoxic activities against HeLa (human epithelial carcinoma), NCI-H460 (human lung cancer), MCF-7 (human breast cancer) cancer cell lines and PHF (primary human fibroblast) cell were evaluated on some extracts and purified compounds at a concentration of 100 μg/mL. Compounds (5, 6, 23) exhibited cytotoxicity against the MCF-7 cell line with the IC50 values of 146.9 ± 9.0, 114.5 ± 7.2, and 112.8 ± 9.4 μM, respectively, while they showed nontoxic with the normal cell (PHF) with IC50s >277 μM. Among 15 tested compounds, (S)-rhodolatouchol (22) showed inhibition against AChE with an IC50 value of 96.1 ± 14.5 μM

https://forskning.ruc.dk/en/publications/caf1494f-ecba-45d6-a68f-9f608422b903

View Article
March 2015
2 Reads

Determination of the tautomeric equilibria of pyridoyl benzoyl β-diketones in the liquid and solid state through the use of deuterium isotope effects on (1)H and (13)C NMR chemical shifts and spin coupling constants.

Spectrochim Acta A Mol Biomol Spectrosc 2015 Feb 6;136 Pt A:107-12. Epub 2013 Sep 6.

Computational and Systems Medicine, Department of Surgery and Cancer, Imperial College London, Sir Alexander Fleming Building, South Kensington, London SW7 2AZ, UK.

View Article
February 2015
16 Reads
2.35 Impact Factor

Pharmacological profile of Xanthohumol, a Prenylated Flavonoid from Hops (Humulus lupulus)

Molecules

The female inflorescences of hops (Humulus lupulus L.), a well-known bittering agent used in the brewing industry, have long been used in traditional medicines. Xanthohumol (XN) is one of the bioactive substances contributing to its medical applications. Among foodstuffs XN is found primarily in beer and its natural occurrence is surveyed. In recent years, XN has received much attention for its biological effects. The present review describes the pharmacological aspects of XN and summarizes the most interesting findings obtained in the preclinical research related to this compound, including the pharmacological activity, the pharmacokinetics, and the safety of XN. Furthermore, the potential use of XN as a food additive considering its many positive biological effects is discussed

https://forskning.ruc.dk/en/publications/b5bcbe14-7dba-4d24-b23a-78de586d549d

View Article
January 2015
2 Reads

Isotope effects on chemical shifts in the study of intramolecular hydrogen bonds

Molecules

The paper deals with the use of isotope effects on chemical shifts in characterizing intramolecular hydrogen bonds. Both so-called resonance-assisted (RAHB) and non-RAHB systems are treated. The importance of RAHB will be discussed. Another very important issue is the borderline between “static” and tautomeric systems. Isotope effects on chemical shifts are particularly useful in such studies. All kinds of intramolecular hydrogen bonded systems will be treated, typical hydrogen bond donors: OH, NH, SH and NH+, typical acceptors C=O, C=N, C=S C=N−. The paper will be deal with both secondary and primary isotope effects on chemical shifts. These two types of isotope effects monitor the same hydrogen bond, but from different angles

https://forskning.ruc.dk/en/publications/d76f8a29-1920-4f02-878f-1a01369a8807

View Article
January 2015
2 Reads

Erbium trifluoromethanesulfonate-catalyzed Friedel–Crafts acylation using aromatic carboxylic acids as acylating agents under monomode-microwave irradiation

Tetrahedron Letters

Erbium trifluoromethanesulfonate is found to be a good catalyst for the Friedel–Crafts acylation of arenes containing electron-donating substituents using aromatic carboxylic acids as the acylating agents under microwave irradiation. An effective, rapid and waste-free method allows the preparation of a wide range of aryl ketones in good yields and in short reaction times with minimum amounts of waste

https://forskning.ruc.dk/en/publications/b2c009f0-50ad-4245-9907-55fc671ca236

View Article
January 2015
2 Reads

Isotope effects on chemical shifts in the study of intramolecular hydrogen bonds.

Authors:
Poul Erik Hansen

Molecules 2015 Jan 30;20(2):2405-24. Epub 2015 Jan 30.

Department of Science, Systems and Models, Roskilde University, Universitetsvej 1, Roskilde DK-4000, Denmark.

View Article
January 2015
3 Reads
2.42 Impact Factor

Pharmacological profile of xanthohumol, a prenylated flavonoid from hops (Humulus lupulus).

Molecules 2015 Jan 7;20(1):754-79. Epub 2015 Jan 7.

State Key Laboratory of Biological Fermentation Engineering of Beer, Qingdao 266061, China.

View Article
January 2015
9 Reads
14 PubMed Central Citations(source)
2.42 Impact Factor

The Importance of Correct Tautomeric Structures for Biological Activity Molecules

JSM Chem 3 Jan 2015

JSM Chemistry

The structures of usnic acid and tetracycline are determined using deuterium isotope effects on 13C chemical shifts in a water environment. In case of usnic acid this is achieved by synthesizing a more water soluble usnic acid with a PEG linker. In the usnic acid case an enolic b-triketone (C-1, C-14 and C-3) tautomeric equilibrium is at hand below pH 5. At pH 7.4 it exists as a mono anion. In case of tetracycline equilibrium between a zwitter ion and a neutral form is found together with an amide functional group and a hydrogen bonded enolic b-diketone system shifted strongly towards one tautomer.

View Article
January 2015
5 Reads

Microwave-assisted facile and rapid Friedel-Crafts benzoylation of arenes catalysed by bismuth trifluoromethanesulfonate

Synthetic Communications

The catalytic activity of metal triflates was investigated in Friedel–Crafts benzoylation under microwave irradiation. Friedel–Crafts benzoylation with benzoyl chloride of a variety of arenes containing electron-rich and electron-poor rings using bismuth triflate under microwave irradiation is described. This method allows the preparation of aryl ketones under solventless conditions in good to excellent yields and short reaction time. Bismuth triflate was easily recovered and reused five times without significant loss of the catalytic activity.

https://forskning.ruc.dk/en/publications/c723b65a-63f6-41ec-9968-b2886d103500

View Article
2014
2 Reads

Arresting Consecutive Steps of a Photochromic Reaction: Studies of β-Thioxoketones Combining Laser Photolysis with NMR Detection

Physical Chemistry Chemical Physics

Photochromism of monothiodibenzoylmethane has been studied in a number of environments at different temperatures. Direct laser irradiation of a sample located in the NMR magnet allowed in situ monitoring of the phototransformation products, determining their structure, and measuring the kinetics of the back reaction. These observations, along with the data obtained using electronic and vibrational spectroscopies for rare gas matrix-isolated samples, glasses, polymers, and solutions, as well as the results of quantum-chemical calculations, provide insight into the stepwise mechanism of the photochromism in β-thioxoketones. At low temperature in rigid matrices the electronic excitation leads to the formation of the –SH exorotamer of the (Z)-enethiol tautomer. In solutions, further steps are possible, producing a mixture of two other non-chelated enethiol forms. Photoconversion efficiency strongly depends on the excitation wavelength. Analysis of the mechanisms of the photochromic processes indicates a state-specific precursor: chelated thione–enol form in the excited S2(ππ*) electronic state. The results show the potential of using laser photolysis coupled with NMR detection for the identification of phototransformation products

https://forskning.ruc.dk/en/publications/b3b73370-b59c-4a83-a323-154e3b54789f

View Article
2014
2 Reads

Structure elucidation of four new megastigmanes from Sonneratia ovata Backer.

Magn Reson Chem 2014 Dec 28;52(12):795-802. Epub 2014 Aug 28.

Department of Basic Science, University of Medicine and Pharmacy, Ho Chi Minh City, Vietnam.

View Article
December 2014
11 Reads
1 PubMed Central Citation(source)
1.18 Impact Factor

Czlonkostwo Honorowe PTChem 2014

57 Zjazd Naukow Polskiego Towarzystwa, Czestochowa, Poland, 14/09/2014

https://forskning.ruc.dk/en/publications/94748fed-91f0-440e-bcbe-8ba13db0742e

View Article
September 2014
4 Reads

Protic ionic liquids, their constitution, properties and use

Central European School on Physical Organic Chemistry : , Przesieka, Poland, 26/05/2014

https://forskning.ruc.dk/en/publications/37a5f385-f22a-4e7f-91b4-8d6b5f793d07

View Article
May 2014
2 Reads

Arresting consecutive steps of a photochromic reaction: studies of β-thioxoketones combining laser photolysis with NMR detection.

Phys Chem Chem Phys 2014 May;16(19):9128-37

Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland.

View Article
May 2014
11 Reads
4.49 Impact Factor

1,1´,1´´-(2,4,6-Trihydroxybenzene-1,3,5-triyl)triethanone tautomerism revisited.

Tetrahedron Letters

It has recently been suggested that 1,1′,1′′-(2,4,6-trihydroxybenzene-1,3,5-triyl)triethanone may be tautomeric. Using 13C NMR chemical shifts and deuterium isotope effects on 13C chemical shifts, it is demonstrated that this is not the case. This compound occurs as a strongly hydrogen bonded benzene structure with hydrogen bonds between OH groups and the acetyl groups in both non-polar and hydrogen donating solvents. Quantum-chemical calculations using MP2 and M06-2X methods show substantial preference for the phenol structure in both the gas phase, and in cyclohexane and methanol. In addition, conventional UV–vis spectroscopy data suggest not tautomeric, but aggregation behaviour of the molecule in methanol and acetonitrile.

https://forskning.ruc.dk/en/publications/ddaff24a-7391-4a88-afcc-840ad07d7945

View Article
January 2014
2 Reads

The effect of 4-tert-butylpyridine and Li+ on the thermal degradation of TiO2 - bound ruthenium dye N719

Solar Energy

Thermal stability experiments were performed at 100 °C of the dye-sensitized solar cell ruthenium dye N719. The experiments were performed as simple test-tube experiments carried out with colloidal solutions of N719-loaded TiO2 particles. The dye degradation was followed by the use of HPLC-coupled electrospray mass spectrometry. The longest half life of N719 of 84 h at 100 °C was obtained in 3-methoxypropionitrile based electrolytes containing 0.5 M 4-TBP, no Li+ ions and 0.25 M . If 4-TBP was removed from the solution the degradation rate of N719 increased up to 3–15 times depending on the concentration. If Li+ ions were added to the electrolyte the degradation increased by a factor of 4–16 times and the thermal degradation product mixture became more complex. It is suggested that an adsorbed layer of 4-TBP on the TiO2 protects the N719 dye against solvent substitution and oxidation processes. A complexation constant of Li+ ions with 4-TBP equal to 9 M−1 was obtained by 13C NMR. The Li+ complexation with 4-TBP is thought to destroy the adsorbed protection layer of 4-TBP on the TiO2 surface.

It is concluded that addition of 4-TBP or other N-additives to the DSC electrolyte is important to enhance the dye life time at elevated temperatures. However, addition of Li+ to the electrolyte should be avoided if the wish is to construct DSCs with high thermal stability.

https://forskning.ruc.dk/en/publications/f153e4fe-ff16-48d4-bae2-87d716e8fc51

View Article
2013
2 Reads

Structural studies of chemical constituents of Thithonia Tagetiflora Desv (Asteraceae)

Magnetic Resonance in Chemistry

Tithonia tagetiflora Desv. (Asteraceae) is a widespread plant in Vietnam, and the species of Tithonia are known as plants containing many biologically active compounds. However, T. tagetiflora's chemical composition remains mostly unknown. Therefore, we now report the structural elucidation of two new sesquiterpene lactones, 8-angeloyloxy-2,14-epoxygermacra-4,10(1),11(13)-trien-6,12-olide (1) and 6-angeloyloxy-1-hydroxy-3,4-epoxygermacra-9,11(13)-dien-8,12-olide (2), together with three known compounds, including two norisoprenoids, (6S,9S)-vomifoliol or (6R,9R)-vomifoliol (3) and (6S,9S)-roseoside (4), and one glutinane type triterpene, epi-glutinol (5), from the leaves of T. tagetiflora. Their structures are established by 1D and 2D NMR spectroscopy, as well as ESI-MS analysis and comparison with literature data

https://forskning.ruc.dk/en/publications/87394822-7c7c-457d-871b-6b44e3c20f96

View Article
2013
2 Reads

Secondary Isotope Effects on 13C and 15N Chemical Shifts of Schiff Bases revisited

Zeitschrift für Physikalische Chemie: International journal of research in physical chemistry and chemical physics

https://forskning.ruc.dk/en/publications/5de77bb2-f5b7-4fc6-bbe7-760067935efd

View Article
2013
2 Reads

Deuterium isotope effects on 13C chemical shifts of 10-Hydroxybenzo[h]quinolines

Molecules

Deuterium isotope effects on 13C-NMR chemical shifts are investigated in a series of 10-hydroxybenzo[h]quinolines (HBQ’s) The OH proton is deuteriated. The isotope effects on 13C chemical shifts in these hydrogen bonded systems are rather unusual. The formal four-bond effects are found to be negative, indicating transmission via the hydrogen bond. In addition unusual long-range effects are seen. Structures, NMR chemical shifts and changes in nuclear shieldings upon deuteriation are calculated using DFT methods. Two-bond deuterium isotope effects on 13C chemical shifts are correlated with calculated OH stretching frequencies. Isotope effects on chemical shifts are calculated for systems with OH exchanged by OD. Hydrogen bond potentials are discussed. New and more soluble nitro derivatives are synthesized.

https://forskning.ruc.dk/en/publications/ca852113-e58b-4d5f-b516-204ec6687920

View Article
2013
2 Reads

Detection of salt bridges to lysines in solution in barnase

Chemical Communications

We show that salt bridges involving lysines can be detected by deuterium isotope effects on NMR chemical shifts of the sidechain amine. Lys27 in the ribonuclease barnase is salt bridged, and mutation of Arg69 to Lys retains a partially buried salt bridge. The salt bridges are functionally important.

https://forskning.ruc.dk/en/publications/6a1310e7-6908-4272-baf4-56c93861965b

View Article
2013
2 Reads

Deuterium isotope effects on 13C chemical shifts of negatively charged NH…N systems.

Magn Reson Chem 2013 Nov 23;51(11):683-8. Epub 2013 Aug 23.

Institute of Physical Chemistry, Polish Academy of Sciences, 01-224, Warsaw, Poland.

View Article
November 2013
5 Reads
1.18 Impact Factor

Detection of salt bridges to lysines in solution in barnase.

Chem Commun (Camb) 2013 Oct;49(84):9824-6

Dept of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.

View Article
October 2013
10 Reads
4 PubMed Central Citations(source)
6.83 Impact Factor

Structural studies of the chemical constituents of Tithonia tagetiflora Desv. (Asteraceae).

Magn Reson Chem 2013 Jul 17;51(7):439-43. Epub 2013 May 17.

Department of Organic Chemistry, University of Science, Vietnam National University of Ho Chi Minh City, Ho Chi Minh City, Vietnam.

View Article
July 2013
7 Reads
1 PubMed Central Citation(source)
1.18 Impact Factor

Deuterium isotope effects on ¹³C-NMR chemical shifts of 10-hydroxybenzo[h]quinolines.

Molecules 2013 Apr 17;18(4):4544-60. Epub 2013 Apr 17.

Department of Science, Systems and Models, Roskilde University, P.O. Box 260, DK-4000 Roskilde, Denmark.

View Article
April 2013
7 Reads
1 PubMed Central Citation(source)
2.42 Impact Factor

Differences in the structure of anthocyanins from the two amphibious plants, Lobelia cardinalis and Nesaea crassicaulis.

Nat Prod Res 2013 Apr 13;27(7):654-64. Epub 2012 Jun 13.

Wine Research Centre, University of Nova Gorica, Vipavska c. 11c, Ajdovščina, Slovenia.

View Article
April 2013
9 Reads
0.92 Impact Factor

A new chromanone acid from the bark of Calophyllum dryobalanoides

Phytochemistry Letters

A new chromanone acid, calodryobalanoic acid, along with six known compounds, apetalic acid, isoblancoic acid, lupeol, 1-hydroxy-2-methoxyxanthone, 1,7-dihydroxy-3-methoxyxanthone, and 5,7,4′-trihydroxyflavanone, was isolated from the bark of Calophyllum dryobalanoides collected in Vietnam. The structure of the new compound was elucidated using mainly 1-D and 2-D NMR techniques (1H and 13C NMR, HSQC, HMBC, COSY, and NOESY) and IR spectroscopy. The stereochemistry was determined on the basis of NMR results and DFT calculations.

https://forskning.ruc.dk/en/publications/94563ba0-95ad-4993-99c3-3df6d3f19ef9

View Article
2012
2 Reads

Dye-sensitized solar cells and complexes between pyridines and iodines. A NMR, IR and DFT study.

Spectrochim Acta A Mol Biomol Spectrosc 2012 Dec 19;98:247-51. Epub 2012 Aug 19.

Department of Science, Systems and Models, Roskilde University, P.O. Box 260, DK-4000 Roskilde, Denmark.

View Article
December 2012
6 Reads
2.35 Impact Factor

On prediction of OH stretching frequencies in intramolecularly hydrogen bonded systems

Journal of Molecular Structure

OH stretching frequencies are investigated for a series of non-tautomerizing systems with intramolecular hydrogen bonds. Effective OH stretching wavenumbers are predicted by the application of empirical correlation procedures based on the results of B3LYP/6-31G(d) theoretical calculations in the harmonic and PT2 anharmonic approximations, as well as on experimental NMR parameters, i.e., proton chemical shifts (δH) and two-bond deuterium isotope effects on 13C chemical shifts (2ΔCOD). The procedures are applied in a discussion of the spectra of 2,6-dihydroxy-4-methylbenzaldehyde and 8-hydroxyquinoline N-oxide. The spectrum of the former displays a broad, composite band between 3500 and 2500 cm–1 which can be assigned to overlapping monomer and dimer contributions. In the latter case, the results support a reassignment of the OH stretching band of 8-hydroxyquinoline N-oxide; the reassignment is supported by correlation with the IR spectra of a series of substituted derivatives.

https://forskning.ruc.dk/en/publications/c60c926e-6935-4893-a24a-4bc4f44949b2

View Article
June 2012
2 Reads

Oliveridepsidones A-D, antioxidant depsidones from Garcinia oliveri.

Magn Reson Chem 2012 Mar 8;50(3):242-5. Epub 2012 Mar 8.

Department of Organic Chemistry, Faculty of Chemistry, HCM City University of Natural Sciences, HCM City, Vietnam.

View Article
March 2012
5 Reads
1.18 Impact Factor

Bromophenols in marine algae and their bioactivities.

Mar Drugs 2011 22;9(7):1273-92. Epub 2011 Jul 22.

Institute of Oceanology, Chinese Academy of Science, Qingdao 266071, China.

View Article
February 2012
10 Reads
19 PubMed Central Citations(source)
2.85 Impact Factor

Prototropic processes in benzaurins. 19F and 1H NMR spectra of fluoro- and methylsubstituted 4-hydroxyphenyl-diphenylcarbinols, related fuchsones and benzaurins

Central European Journal of Chemistry

Tautomerism of benzaurins and hydration are studied. 1H and 19F chemical shifts have been determined for a number of substituted 4-hydroxyphenyl-diphenyl carbinols containing fluorine in a 3-, 3*- or 4*-position, and for similar compounds containing additional methyl groups in a position of 3, 3** or 4**. The same data have been obtained for the fuchsones prepared by dehydration of the above carbinols. On this basis chemical shifts of fluorine in different positions have been evaluated as a monitor of the transformation of 4-hydroxyphenyl group to the semiquinone moiety. The 19F NMR can be used to monitor the transformation of 4**-fluorobenzaurin and the related 3,3*-disubstituted and 3,3*,5,5*-tetramethylsubstituted compounds to the corresponding carbinols due to the addition of a water molecule and to study the tautomerism of the two latter benzaurins as well as that of 3,3*,4**trifluorobenzaurin. Furthermore, fluorine and methyl group chemical shifts are sensitive to syn-anti-isomerism in substituted fuchsones.
The prototropic process of these compounds may be slow or fast on a 1H NMR time scale depending on the solvent and may be catalyzed by water or carbonic acids. On the basis of kinetic and thermodynamic data obtained by dynamic NMR studies, a mechanism for the process has been proposed.

https://forskning.ruc.dk/en/publications/79b40567-9b28-4835-b461-b5bf1950143e

View Article
2011
2 Reads

Photovoltaic performance and characteristics of dye sensitized solar cells prepared with the N719 thermal degradation products [Ru(L-H)2(NCS)(4-tert-butylpyridine)]-, +N(Bu)4 and [Ru(L-H)2(NCS)(1-methylbenzimidazole)]-, +N(Bu)4

European Journal of Inorganic Chemistry

The dye-sensitized solar cell N719 thermal degradation products [Ru(LH)2(NCS)(4-tert-butylpyridine)][N(Bu)4] (1) and [Ru(LH)2(NCS)(1-methylbenzimidazole)][N(Bu)4] (2) were synthesized from [Ru(LH)2(NCS)2][N(Bu)4]2 (N719), (L = 2,2′-bipyridyl-4,4′-dicarboxylic acid) and characterized by electrospray mass spectrometry and NMR spectroscopy. Dye-sensitized solar cells (DSCs or DSSCs) prepared with 1 and 2 have efficiencies that are three and two times lower than N719 cells, respectively. Analysis of the UV/Vis and incident-photon-to-current efficiency (IPCE) spectra indicates that the main reason for the reduced efficiencies is a reduced electron collection efficiency (ηcoll). The substituted dyes give rise to lower potentials and currents. When measured at open circuit voltage illumination, the impedance is very different for such cells relative to N719 cells. Furthermore, the lifetime (τeff) of the electrons in the TiO2 is reduced by a factor of around ten. The low τeff values may be related to the positive charge on dyes 1 and 2, which results in an enhanced local concentration of I3– near the photoanode and thereby a higher dark current. N719 cells at higher temperature result in slightly lower potentials, and this alone leads to a change in impedance response when measured at open circuit voltage. The same parts of the impedance spectrum are affected (i.e., the interface between the photoanode and the electrolyte is affected in the same way) when we compare data from N719 heated cells and DSCs prepared with 1 or 2 and not thermally treated.

https://forskning.ruc.dk/en/publications/95e55515-2682-4534-b823-1e5ad05a6e0c

View Article
2011
2 Reads

OH stretching frequencies in systems with intramolecular hydrogen bonds

Chemical Physics

OH stretching wavenumbers were investigated for 30 species with intramolecularly hydrogen bonded hydroxyl groups, covering the range from 3600 to ca. 1900 cm-1. Theoretical wavenumbers were predicted with B3LYP/6-31G(d) density functional theory using the standard harmonic approximation, as well as the second-order perturbation theoretical (PT2) anharmonic approximations available with the GAUSSIAN software package. The wavenumbers computed with the anharmonic procedures were found to be essentially linearly related to those obtained within the harmonic analysis. The theoretical wavenumbers were compared with experimental values taken from the literature, supplemented with values estimated from infrared (IR) absorption spectra recorded for the purpose of this study. An approximately linear relationship was established between the observed wavenumbers νOH and the results of the harmonic analysis. This is significant in view of the fact that the full anharmonic PT2 analysis requires orders-of-magnitude more computing time than the harmonic analysis. νOH also correlates with OH chemical shifts.

https://forskning.ruc.dk/en/publications/f9285247-db87-4928-91f8-7589985cc355

View Article
2011
2 Reads

Bromophenols in Marine Algae and Their Bioactivities

Marine Drugs

Marine algae contain various bromophenols that have been shown to possess a variety of biological activities, including antioxidant, antimicrobial, anticancer, anti-diabetic, and anti-thrombotic effects. Here, we briefly review the recent progress of these marine algal biomaterials, with respect to structure, bioactivities, and their potential application as pharmaceuticals.

https://forskning.ruc.dk/en/publications/c2602684-88c4-4183-9590-b491ae544648

View Article
2011
3 Reads

A 19F NMR study of C-I....pi- halogen bonding

Chemical Physics

The formation of halogen bonded complexes between toluene-d8 and the perfluoroiodopropanes 1-C3F7I and 2-C3F7I has been investigated using 19F NMR spectroscopy. For both Lewis acids, evidence was found for the formation of a C–I⋯π halogen bonded complex. The complex formed is a 1:1 type. Using spectra recorded at different temperatures, the complexation enthalpies and entropies for the complexes were determined to be −2.9(1) kJ mol−1 and −19.1(2) J K−1 mol−1 for the 2-C3F7I⋅toluene-d8 complex and −2.7(1) kJ mol−1 and −16.0(4) K−1 mol−1 for the 1-C3F7I⋅toluene-d8 complex. The experimental results are supported by ab initio calculations at the B3LYP-PCM/6-311++G(d,p) + LanL2DZ∗ level.

https://forskning.ruc.dk/en/publications/8b856185-b2c2-46c5-89ed-2273ec4f1509

View Article
2011
4 Reads

Ab initio calculations of deuterium isotope effects on chemical shifts of salt-bridged lysines.

J Phys Chem B 2011 Mar 9;115(12):3208-15. Epub 2011 Mar 9.

Department of Science, Systems and Models, Roskilde University, Roskilde, Denmark.

View Article
March 2011
5 Reads

Friedolanostane, friedocycloartane and benzophenone constituents of the bark and leaves of Garcinia benthami.

Phytochemistry 2011 Feb 16;72(2-3):290-5. Epub 2010 Dec 16.

Faculty of Chemistry, Ho Chi Minh City University of Science (HCMUS), Ho Chi Minh City, Viet Nam.

View Article
February 2011
14 Reads
1 PubMed Central Citation(source)
2.55 Impact Factor

Trichloromethyl compounds - natural background concentrations and fates within and

Science of the Total Environment

Pollution with organochlorines has received major attention due to various environmental effects, but it is now increasingly recognized, that they also take part in biogeochemical cycles and that natural background concentrations exist for several chlorinated compounds. We here report the natural occurrence and cycling of organic compounds with a trichloromethyl moiety in common. The study areas are temperate coniferous forests. Trichloromethyl compounds can be found in all compartments of the forests (groundwater, soil, vegetation and throughfall), but not all compounds in all compartments. The atmospheric input of trichloromethyl compounds is found to be minor, with significant contributions for trichloroacetic acid (TCAA), only.

In top soil, where the formation of the compounds is expected to occur, there is a clear positive relationship between chloroform and trichloroacetyl containing compounds. Other positive relations occur, which in combination with chlorination experiments performed in the laboratory, point to the fact that all the trichloromethyl compounds may be formed concurrently in the soil, and their subsequent fates then differ due to different physical, chemical and biological properties. TCAA cannot be detected in soil and groundwater, but sorption and mineralization experiments performed in the laboratory in combination with analyses of vegetation, show that TCAA is probably formed in the top soil and then partly taken up by the vegetation and partly mineralized in the soil. Based on this and previous studies, a conceptual model for the natural cycling of trichloromethyl compounds in forests is proposed

https://forskning.ruc.dk/en/publications/b6034094-d1ce-4e7f-8796-eca80b21b8e9

View Article
2010
2 Reads

Resonance assisted hydrogen bonding (RAHB).  What is the evidence using Isotopes?

2010 Gordon Conference on Isotopes in Biological and Chemical Sciences, Galveston, United States, 14/02/2010

https://forskning.ruc.dk/en/publications/40c4b3a0-3374-11df-8862-000ea68e967b

View Article
2010
2 Reads

13C-NMR chemical shift databases as a quick tool to evaluate structural models of humic substances

Open Magnetic Resonance Journal

Models for humic and fulvic acids are discussed based on 13C liquid state NMR spectra combined with results from elemental analysis and titration studies. The analysis of NMR spectra is based on a full reconstruction of the NMR spectrum done with help of 13C-NMR data bases by adding up chemical shifts of all substructures from the proposed models. A full reconstruction makes sure that all carbons are accounted for and enables on the negative side to discuss structural elements identified from recorded spectra of humic substances that cannot be observed in the simulated spectrum. On the positive side missing structural elements in the models can be suggested. A number of proposed structures for humic and fulvic acids are discussed based on the above analysis.

https://forskning.ruc.dk/en/publications/06db4230-4161-11df-8b90-000ea68e967b

View Article
2010
2 Reads

Trichloromethyl compounds--natural background concentrations and fates within and below coniferous forests.

Sci Total Environ 2010 Nov;408(24):6223-34

Dept. Geochemistry, Geological Survey of Denmark & Greenland, Ø. Voldgade 10, DK-1350, Copenhagen, Denmark.

View Article
November 2010
7 Reads
4.10 Impact Factor

Theoretical and NMR studies of deuterium isotopic perturbation of hydrogen bonding in symmetrical dihydroxy compounds.

J Org Chem 2010 Mar;75(5):1331-42

Department of Chemistry, Bowdoin College, 6600 College Station, Brunswick, Maine 04011, USA.

View Article
March 2010
10 Reads
1 PubMed Central Citation(source)
4.72 Impact Factor

Methodological problems in determining TCAA in soils-the discovery of novel natural trichloroacetyl containing compounds and their interference with a common method for determining TCAA in soil and vegetation.

J Environ Monit 2010 Mar 22;12(3):672-80. Epub 2009 Dec 22.

Dept. Geochemistry, Geological Survey of Denmark & Greenland, Ø. Voldgade 10, DK-1350, Copenhagen, Denmark.

View Article
March 2010
7 Reads
2.18 Impact Factor

Isolation and preparation of cytotoxic chromanone acids from the bark of Calophyllum dongnaiense

Journal of Chemistry

Three chromanone acids, blancoic acid (1), isoblancoic acid (2) and chapelieric acid (3), were isolated from the bark of Calophyllum dongnaiense Pierre collected in Dong Nai Province. Their structures were elucidated using spectroscopic techniques (1-D and 2-D NMR, UV, IR and MS) as well as chemical methods. Cytotoxicity of compounds 1-3 and their 5-O-acetylated and methylated derivatives against Hela cell line was examined.

https://forskning.ruc.dk/en/publications/f993af70-fa40-11de-89af-000ea68e967b

View Article
2009
2 Reads

Cytotoxic geranylated xanthones and O-alkylated derivatives of alpha-mangostin

Chemical & Pharmaceutical Bulletin

Two new geranylated xanthones, 6-O-methylcowanin (4) and oliverixanthone (5), along with five known
compounds, cowanin, rubraxanthone, cowaxanthone, cowanol, and β-mangostin, have been isolated from the
bark of Garcinia oliveri. For comparison of their biological activities, one mono- and seven di-O-alkylated
α-mangostin derivatives were synthesized from α-mangostin. The structures of all compounds were assigned by
spectroscopic methods (1D and 2D NMR and MS). Cytotoxicity of selected xanthones against MCF-7 and DLD-1
cell lines was examined. Evaluation of the structure–activity relationship showed that α-mangostin had the
strongest activity, and all the O-alkylated α-mangostin derivatives showed reduced activity compared to the naturally
occurring α-mangostin.

https://forskning.ruc.dk/en/publications/3ebca640-a106-11de-951d-000ea68e967b

View Article
2009
2 Reads

NMR of a series of novel hydroxyflavothiones.

Magn Reson Chem 2009 Dec;47(12):1043-54

Department of Science, Systems and Models, Roskilde University, PO Box 260, DK-4000 Roskilde, Denmark.

View Article
December 2009
9 Reads
1.18 Impact Factor

The influence of organic matter on sorption and fate of glyphosate in soil--comparing different soils and humic substances.

Environ Pollut 2009 Oct 17;157(10):2865-70. Epub 2009 May 17.

Dept. of Geochemistry, Geological Survey of Denmark and Greenland, DK-1350 Copenhagen, Denmark.

View Article
October 2009
9 Reads
2 PubMed Central Citations(source)
4.14 Impact Factor

Cytotoxic geranylated xanthones and O-alkylated derivatives of alpha-mangostin.

Chem Pharm Bull (Tokyo) 2009 Aug;57(8):830-4

Faculty of Chemistry, HCM City University of Natural Sciences, HCM City, Vietnam.

View Article
August 2009
7 Reads
1.38 Impact Factor

Deuterium isotope effects on 15N backbone chemical shifts in proteins.

J Biomol NMR 2009 Jul 20;44(3):119-26. Epub 2009 May 20.

Department of Science, Systems and Models, Roskilde University, Roskilde, Denmark.

View Article
July 2009
5 Reads
3 PubMed Central Citations(source)
3.14 Impact Factor

Characterization of salt bridges to lysines in the protein G B1 domain.

J Am Chem Soc 2009 Apr;131(13):4674-84

Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN UK.

View Article
April 2009
6 Reads
9 PubMed Central Citations(source)
12.11 Impact Factor

Bioactivities and chemical constituents of a Vietnamese medicinal plant Che Vang, Jasminum subtriplinerve Blume (Oleaceae).

Nat Prod Res 2008 ;22(11):942-9

Department of Chemistry, College of Natural Sciences, National University of Ho Chi Minh City, 227 Nguyen Van Cu St., Dist. 5, Ho Chi Minh City, Vietnam.

View Article
January 2009
20 Reads
0.92 Impact Factor

Effect of different humic substances on the fate of diuron and its main metabolite 3,4-dichloroaniline in soil.

Environ Sci Technol 2008 Dec;42(23):8687-91

Department of Geochemistry, Geological Survey of Denmark and Greenland, DK-1350, Copenhagen, Denmark.

View Article
December 2008
6 Reads
2 PubMed Central Citations(source)
5.33 Impact Factor

Deuterium isotope effects on 13C chemical shifts of nitromalonamide.

Authors:
Poul Erik Hansen

Magn Reson Chem 2008 Aug;46(8):726-9

Department of Science, Systems and Models, Roskilde University, Roskilde, Denmark.

View Article
August 2008
5 Reads
1.18 Impact Factor

Bioactivities and chemical constituents of a vietnamese medicinal plant Che Vang, Jasminum subtriplinerve Blume (Oleaceae)

Natural Product Research

Five crude extracts were made from leaves and stems of Jasminum subtriplinerve Blume (Oleaceae) and investigated for antimicrobial, antioxidant and cytotoxic activities. The extractions were done with petroleum ether, ethyl acetate, ethanol, methanol or water. All extracts exhibited anti-bacterial activity except the water fraction. On the other hand, all extracts exhibit antioxidant activity except the petroleum ether fraction using the DPPH radical scavenging assay. Only the petroleum ether fraction showed a cytotoxicity activity against tested cell-lines, Hep-G2 and RD with IC50 values of 19.2 and 20 μg/mL, respectively. From the petroleum ether and ethyl acetate extracts, two triterpenes namely 3-acetyl-oleanolic acid and lup-20-en-3-ol and a sterol, stigmast-5-en-3-ol were isolated. The structure of those compounds were elucidated by spectrometric methods IR, MS, 1D-NMR, 2D-NMR and 25 simulated ACD/NMR spectra. The data presented here indicate that J. subtriplinerve do contain compounds with interesting biological activity.

https://forskning.ruc.dk/en/publications/9ee25f70-cfdd-11dc-af2a-000ea68e967b

View Article
July 2008
2 Reads

Density functional theory study of intramolecular hydrogen bonding and proton transfer in o-hydroxyaryl ketimines.

J Phys Chem A 2008 Apr 22;112(15):3478-85. Epub 2008 Mar 22.

Faculty of Chemistry, University of Wrocław, F. Joliot-Curie 14, 50-383 Wrocław, Poland.

View Article
April 2008
8 Reads
2 PubMed Central Citations(source)
2.69 Impact Factor

Photochromism in p-methylbenzoylthioacetone and related β-thioxoketones

Chemical Physics

Irradiation of p-methylbenzoylthioacetone with UV or visible light brings about spectral changes characteristic for the photochromic behavior of β-thioxoketones. The nature of the initial species and of the photochromic product can be assigned based on spectral studies of the electronic and IR spectra in rare gas matrices combined with quantum chemical calculations. Additional arguments for the vibrational assignments are provided by using polarized light to induce the phototransformation, and by subsequent measurements of linear dichroism on partially aligned samples. Comparison with the results previously obtained for three related molecules: thioacetylacetone, p-methyl(thiobenzoyl)acetone, and monothiodibenzoylmethane reveals a common pattern of the photochromic reaction. In all four molecules, the initial species corresponds to an intramolecularly hydrogen-bonded enolic molecular structure, and the main photochromic product to an "open", nonchelated enethiolic counterpart. On the basis of a computational TD-DFT study of ground and excited electronic states, possible mechanisms of the photochromic transformation are discussed.

https://forskning.ruc.dk/en/publications/f3cc0e30-c32e-11db-b7d6-000ea68e967b

View Article
2007
2 Reads

Monothiodibenzoylmethane: Structural and vibrational assignments

Vibrational Spectroscopy

The vibrational structure of the title compound (1,3-diphenyl-3-thioxopropane-1-one, TDBM) was studied by a variety of experimental and theoretical methods. The stable ground state configuration of TDBM was investigated by IR absorption measurements in different media, by LD polarization spectroscopy of samples partially aligned in a stretched polymer matrix, and by Raman spectroscopy. The investigation of the metastable photoproduct of TDBM was based on the previously published spectrum of the product trapped in argon matrix (Posokhov et al., Chem. Phys. Lett. 350 (2001) 502). The observed vibrational spectra were compared with theoretical transitions obtained with B3LYP/cc-pVTZ density functional theory (DFT). The results leave no doubt that the stable ground state configuration of TDBM corresponds to the intramolecularly hydrogen bonded enol form (e-CCC), and that the photoproduct corresponds to an “open”, non-chelated enethiol form (t-TCC), thereby supporting the previous conclusions by Posokhov et al. No obvious indications of the contribution of other forms to the observed spectra could be found.

https://forskning.ruc.dk/en/publications/62a53020-9a6c-11db-86ab-000ea68e967b

View Article
2007
2 Reads

Conformational and tautomeric eccentricities of 2-acetyl-1,8-dihydroxynaphthalenes

Magnetic Resonance in Chemistry

Tautomerism in aromatic systems with oxygen substiuents is rare. This is investigated in 2-acetyl-1,8-dihydroxy-3,6-dimethylnaphthalene (1) and in 2,7-diacetyl-1,8-dihydroxy-3,6-dimethylnaphthalene (2). The tautomeric nature of 2-acetyl-1,8-dihydroxy-3,6-dimethylnaphthalene is supported by long-range hydrogen-hydrogen coupling between the OH-1 and the OH-8 and by the isotope effects on 13C caused by deuteration at the CH3C=O methyl group. Compound 2 participates in a degenerate equilibrium between two equivalent nonsymmetrical rotamers (2A and 2B) , each having two intramolecular O...HO hydrogen bonds: one involving an acetyl oxygen and the neighbouring hydroxyl group, and the other between the oxygen centers at positions 1 and 8. In addition, each rotamer is involved in a tautomeric equilibrium, with a structure having an OH-substituted exocyclic double bond (2AT or 2BT). - DFT calculations for a large set of compounds highlight the factors controlling the unusual rotational and tautomeric behaviors. A very important factor seems to be the repulsive interaction between the O-1 and O-8 centers, which is modulated by formation of an OH-1...O-8 or OH-8..O-1 hydrogen bond. Steric interactions, mesomeric release of electrons from the oxygen at position 8, and a strong OH...O=C hydrogen bond are other factors. - Solid-state 13C NMR spectra of 2,7-diacetyl-1,8-dihydroxy-3,6-dimethylnaphthalene at different temperatures demonstrated no averaging in the solid, whereas partially deuterated 2-acetyl-1,8-dihydroxy-3,6-dimethylnaphthalene showed an isotope effect at C-1 of 1.5 ppm, indicating tautomerism in the solid state.

https://forskning.ruc.dk/en/publications/879d3fb0-9f19-11db-9f01-000ea68e967b

View Article
2007
2 Reads

An evaluation of a model for the systematic documentation of hospital based health promotion activities: results from a multicentre study.

BMC Health Serv Res 2007 Sep 18;7:145. Epub 2007 Sep 18.

Clinical Unit of Health Promotion/WHO Collaborating Centre for Evidence Based Health Promotion in Hospitals, Bispebjerg Hospital, DK 2400 Copenhagen, Denmark.

View Article
September 2007
10 Reads
5 PubMed Central Citations(source)
1.66 Impact Factor

Ultrasound assisted synthesis of 5,9-dimethylpentadecane and 5,9-dimethylhexadecane--the sex pheromones of Leucoptera coffeella.

Molecules 2007 Aug 28;12(8):2080-8. Epub 2007 Aug 28.

Department of Science, Systems and Models, Roskilde University, P. O. Box 260, DK-4000 Roskilde, Denmark.

View Article
August 2007
7 Reads
2.42 Impact Factor

Long-range deuterium isotope effects on (13)C chemical shifts of intramolecularly hydrogen-bonded N-substituted 3-(cycloamine)thiopropionamides or amides: a case of electric field effects.

J Org Chem 2007 May 1;72(11):4108-16. Epub 2007 May 1.

Institute of Chemistry and Environmental Protection, Szczecin University of Technology, Aleja Piastów 42, 71065 Szczecin, Poland.

View Article
May 2007
8 Reads
3 PubMed Central Citations(source)
4.72 Impact Factor

Intramolecular hydrogen bonding of novel o-hydroxythioacetophenones and related compounds evaluated by deuterium isotope effects on 13C chemical shifts.

Magn Reson Chem 2007 Mar;45(3):245-52

Department of Organic Chemistry, University of Natural Sciences, National University of HoChiMinh City, 227 Nguyen Van Cu St, Dist 5, HoChiMinh City, Vietnam.

View Article
March 2007
7 Reads
1.18 Impact Factor

Conformational and tautomeric eccentricities of 2-acetyl-1,8-dihydroxynaphthalenes.

Magn Reson Chem 2007 Feb;45(2):106-17

Department of Science, Systems and Models, Roskilde University, P.O. Box 260, DK-4000 Roskilde, Denmark.

View Article
February 2007
7 Reads
1.18 Impact Factor

Photochromism and polarization spectroscopy of p-methylthiobenzoylacetone

Chemical Physics

Photochromism of p-methylthiobenzoylacetone (1) has been studied in argon and xenon cryogenic matrices. Application of linearly polarized light to induce the phototransformation resulted in partial alignment of both the initial structure and the photochromic product. Different orientations were achieved by using irradiation wavelengths corresponding to differently polarized electronic transitions. This was followed by measurements of linear dichroism (LD) in the IR region. The analysis of the IR spectra, combined with the results of DFT B3LYP/cc-pVDZ calculations enabled determining the structures of the most stable ground state species and of the photoproduct. Similarly to the recently reported cases of thioacetylacetone and monothiodibenzoylmethane, the initial structure of 1 corresponds to an intramolecularly hydrogen-bonded enol form, and the photochromic species to an “open”, nonchelated enethiolic form. Vibrational assignments have been made for both species, greatly helped by the analysis of the LD spectra. It is concluded that DFT calculations for 1 quite reliably predict not only vibrational frequencies and intensities, but also transition moment directions, in both IR and electronic spectra.

https://forskning.ruc.dk/en/publications/b9383430-9a6e-11db-86ab-000ea68e967b

View Article
2006
2 Reads

Variable-temperature NMR study of the enol forms of benzoylacetones

Magnetic Resonance in Chemistry

NMR, Enols, taomerism, hydrogen bonding, deuterium isotope effects, chemical shifts, OH coupling constants, diketones

https://forskning.ruc.dk/en/publications/361511e0-52cf-11db-8236-000ea68e967b

View Article
2005
2 Reads

Fast preparation of dihydrocyclocitral from citronellal under solventless microwave irradiation

Tetrahedron Letters

Dihydrocyclocitral, a useful reagent in organic synthesis, has been synthesized in high yield and with high stereoselectivity from citronellal under microwave irradiation in two steps, involving acetic anhydride under base catalysis, then p-toluene-sulfonic acid on silica gel under solventless conditions.

https://forskning.ruc.dk/en/publications/37c42170-52cf-11db-8236-000ea68e967b

View Article
2005
2 Reads

Variable-temperature NMR study of the enol forms of benzoylacetones.

Magn Reson Chem 2005 Dec;43(12):992-8

Institute of Bio-organic Chemistry, National Academy of Sciences of Belarus, ul. Kuprevicha, 5/2, 220141, Minsk, Belarus.

View Article
December 2005
5 Reads
1.18 Impact Factor

Factor analysis of deuterium isotope effects on 13C NMR chemical shifts in Schiff bases.

Chemistry 2005 Aug;11(16):4758-66

Chemistry Department, Warsaw University, Warszawa, Poland.

View Article
August 2005
5 Reads
5.73 Impact Factor

Schiff bases of gossypol: an NMR and DFT study.

Magn Reson Chem 2005 Apr;43(4):302-8

University of Natural Sciences, National University of HoChiMinh City, Vietnam.

View Article
April 2005
9 Reads
1.18 Impact Factor

NMR structure determination of a modified DNA oligonucleotide containing a new intercalating nucleic acid.

Bioconjug Chem 2004 Mar-Apr;15(2):260-9

Nucleic Acid Center, Department of Chemistry, University of Southern Denmark, DK-5230 Odense M, Denmark.

View Article
November 2004
4 Reads
7 PubMed Central Citations(source)
4.51 Impact Factor

Multiple binding modes of the camptothecin family to DNA oligomers.

Chemistry 2004 Nov;10(22):5776-87

National Institute of Public Health, 00-725 Warszawa, Chełmska 30/34, Poland.

View Article
November 2004
4 Reads
1 PubMed Central Citation(source)
5.73 Impact Factor

Thioacetylacetone: structural and vibrational assignments.

Chemphyschem 2004 Apr;5(4):495-502

Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44, 01-224 Warsaw, Poland.

View Article
April 2004
6 Reads
3.42 Impact Factor

Isolation, characterization, and quantitative analysis of Microviridin J, a new Microcystis metabolite toxic to Daphnia.

J Chem Ecol 2003 Aug;29(8):1757-70

Freshwater Biological Laboratory, University of Copenhagen, Helsingørsgade 51, 3400 Hillerød, Denmark.

View Article
August 2003
11 Reads
14 PubMed Central Citations(source)
2.75 Impact Factor

The application of high-performance liquid chromatography humic acid columns in determination of Koc of polycyclic aromatic compounds.

Environ Toxicol Chem 2003 Apr;22(4):741-5

Plant Research Department, Risø National Laboratory, PO Box 49, DK-4000 Roskilde, Denmark.

View Article
April 2003
7 Reads
3.23 Impact Factor

Exploring symbiotic nitrogen fixation and assimilation in pea root nodules by in vivo 15N nuclear magnetic resonance spectroscopy and liquid chromatography-mass spectrometry.

Plant Physiol 2003 Jan;131(1):367-78

Risoe National Laboratory, Plant Research Department, Roskilde University, Roskilde, Denmark DK-4000.

View Article
January 2003
6 Reads
6 PubMed Central Citations(source)
6.84 Impact Factor

Characterisation of humic materials of different origin: a multivariate approach for quantifying the latent properties of dissolved organic matter.

Chemosphere 2002 Dec;49(10):1327-37

Department of Policy Analysis and Environmental Science, National Environmental Research Institute, DK-4000 Roskilde, Denmark.

View Article
December 2002
6 Reads
2 PubMed Central Citations(source)
3.34 Impact Factor

Reverse quantitative structure-activity relationship for modelling the sorption of esfenvalerate to dissolved organic matter. A multivariate approach.

Chemosphere 2002 Dec;49(10):1317-25

Department of Policy Analysis, National Environmental Research Institute, P.O. Box 358, DK-4000 Roskilde, Denmark.

View Article
December 2002
7 Reads
3.34 Impact Factor

Solution structure of the eukaryotic pore-forming cytolysin equinatoxin II: implications for pore formation.

J Mol Biol 2002 Feb;315(5):1219-29

Biomolecular Research Institute, 343 Royal Parade, Parkville 3052, Australia.

View Article
February 2002
7 Reads
24 PubMed Central Citations(source)
4.33 Impact Factor

H-1 NMR of compounds with low water solubility in the presence of erythrocytes

European Biophysics Journal

When lipophilic compounds like diethyl phthalate (DEP) were added to water, two sets of resonances appeared in the 1H NMR spectrum, whereas when added in concentrations above ~3.5 mM to erythrocytes in a high haematocrit suspension, only one set of resonances was observed at the low-frequency position. The appearance of one set of resonances at lower frequency was found to be common to a series of lipophilic compounds in erythrocytes. The appearance of the NMR spectra is ascribed to the existence of an emulsion, meaning two different phases of a compound: a "droplet" (resonances to lower frequency) and aqueous dissolved phase (resonances to higher frequency). The absence of the resonances from the dissolved phase in erythrocyte solution is ascribed to exchange broadening. The absolute chemical shift of the compound in its "droplet" phase was also measured using a cylindrical/spherical microcell. This arrangement mimicked the geometry of the dissolved versus the phase-separated species and thus obviated the effect of a difference in magnetic susceptibility between the "droplet" solute and its aqueous solution. Factors influencing the formation of emulsion phases such as erythrocytes, haemoglobin and smaller proteins were investigated; they are found to be effective in the order given

https://forskning.ruc.dk/en/publications/92928ca0-52ce-11db-8236-000ea68e967b

View Article
2001
1 Read

Ibuprofen

Skrift / Roskilde universitetscenter, Institut for biologi og kemi

https://forskning.ruc.dk/en/publications/a001c272-017a-4938-a2ec-1e857c06ebac

View Article
1991
2 Reads

Deuterium Isotope Effects on 14,15N Chemical Shifts of Ammonium Ions. (2011)

doi:10.1155/2011/696497

International Journal of Inorganic Chemistry

Deuterium isotope effects on 14,15N chemical shifts are measured in ammonium halides in the solid state using both enriched 15N salts and 14N natural abundancematerials. The effects are correlated to 15N chemical shifts and to N···X distances. The deuterium isotope effects on 14,15N chemical shifts in the solid state are discussed in relation to effects observed in solution. No NH couplings are seen due to fast rotation in the solid, which leads to self-decoupling, whereas ND couplings are present.

View Article
12 Reads
Top co-authors
Fritz Duus
Fritz Duus

Roskilde University

6
Fadhil S Kamounah
Fadhil S Kamounah

Roskilde University

5
Jens Spanget-Larsen
Jens Spanget-Larsen

Roskilde University

4
Mike P Williamson
Mike P Williamson

University of Sheffield

3
Wei Zhang
Wei Zhang

University of Minnesota Twin Cities

3
Torben Lund
Torben Lund

Copenhagen University Hospital

3
Mariusz Pietrzak
Mariusz Pietrzak

Warsaw University of Technology

2
Followers
krishnaiah Damarla
krishnaiah Damarla

CSIR-CSMCRI