1,687 results match your criteria Tetrahedron Letters [Journal]


Imidazolidin-4-ones via (3+2) cycloadditions of aza-oxyallyl cations onto ()-arylideneanilines.

Tetrahedron Lett 2018 Oct 5;59(41):3674-3677. Epub 2018 Sep 5.

Department of Chemistry and Biochemistry, San Francisco State University, 1600 Holloway Avenue, San Francisco, Ca 94132, USA.

In the course of our studies on the chemistry of oxyallyl species we uncovered a new (3+2) cycloaddition of aza-oxyallyl systems, generated in situ from -benzyloxy-2-chloroamides in the presence of NEt, onto -arylimines yielding imidazolidin-4-ones in moderate to good yields. The cycloadditions are regioselective. Computational modelling using DFT at the M062×/6-311+G** level is in support the observed regioselectivities. Read More

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http://dx.doi.org/10.1016/j.tetlet.2018.08.056DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6236675PMC
October 2018
4 Reads

Copper-Mediated Nucleophilic Radiobromination of Aryl Boron Precursors: Convenient Preparation of a Radiobrominated PARP-1 Inhibitor.

Tetrahedron Lett 2018 May 11;59(20):1963-1967. Epub 2018 Apr 11.

Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801.

The copper-mediated nucleophilic radiobromination of aryl boron precursors with a radiobromide ion is a novel radiolabeling method that is efficient and robust. High radiochemical conversion (RCC) was observed using a variety of solvents, temperatures and catalysts. The reaction is also clean and is feasible for purification to obtain high chemical and radiochemical purity. Read More

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http://dx.doi.org/10.1016/j.tetlet.2018.04.024DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6195330PMC
May 2018
4 Reads

Lipidated cyclopropenes a stable 3- spirocyclopropene scaffold.

Tetrahedron Lett 2018 Sep 7;59(37):3435-3438. Epub 2018 Aug 7.

Department of Chemistry, Stony Brook University, Stony Brook, NY, 11790, United States.

Lipidated cyclopropenes serve as useful bioorthogonal reagents for imaging cell membranes due to the cyclopropene's small size and ability to ligate with pro-fluorescent tetrazines. Previously, the lipidation of cyclopropenes required modification at the C3 position because methods to append lipids at C1/C2 were not available. Herein, we describe C1/C2 lipidation with the biologically active lipid ceramide and a common phospholipid using a cyclopropene scaffold whose reactivity with 1,2,4,5-tetrazines has been caged. Read More

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https://linkinghub.elsevier.com/retrieve/pii/S00404039183098
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http://dx.doi.org/10.1016/j.tetlet.2018.08.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6190722PMC
September 2018
5 Reads

Ir(COD)Cl]/Tris(2,4-di--butylphenyl)phosphite-Catalyzed Addition Reactions of Arylboronic Acids with Aldehydes.

Tetrahedron Lett 2018 Apr 2;59(16):1548-1550. Epub 2018 Mar 2.

Department of Chemistry, College of Staten Island of the City University of New York, Staten Island, New York, 10314 and the Ph.D. Program in Chemistry, the Graduate Center of the City University of New York, New York, NY 10016, United States.

[Ir(COD)Cl]/tris(2,4-di--butylphenyl)phosphite-catalyzed addition reactions of arylboronic acids with aldehydes were described. The Ir(I) catalyst, generated from [Ir(COD)Cl] and tris(2,4-di--butylphenyl)phosphite, was an efficient catalyst system for the addition reactions of a variety of arylboronic acids with aromatic and aliphatic aldehydes. The easy availability of the catalyst and good yields make these reactions potentially useful in organic synthesis. Read More

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http://dx.doi.org/10.1016/j.tetlet.2018.02.071DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6186456PMC
April 2018
1 Read

dM-Dim for Carboxylic Acid Protection.

Tetrahedron Lett 2018 May 27;59(18):1763-1766. Epub 2018 Mar 27.

Department of Chemistry, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931 USA.

The 1,3-dithian-2-yl-methyl (Dim) and its analogous groups including dimethyl-Dim (dM-Dim) can provide a new dimension of orthogonality for carboxylic acid protection. They can be deprotected under nearly neutral oxidative conditions. In this paper, the protection of carboxylic acid with dM-Dim, deprotection of dM-Dim ester with sodium periodate, stability of dM-Dim protected carboxylic acid under acidic and basic conditions, and selective deprotection of dM-Dim protected carboxylic acids in the presence of tertiary butyl and methyl esters are presented. Read More

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https://linkinghub.elsevier.com/retrieve/pii/S00404039183040
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http://dx.doi.org/10.1016/j.tetlet.2018.03.076DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6161831PMC
May 2018
2 Reads

Direct Synthesis of α-Thio Aromatic Acids from Aromatic Amino Acids.

Tetrahedron Lett 2018 Mar 13;59(12):1140-1142. Epub 2018 Feb 13.

Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697-3900.

Modified amino acids are useful synthetic components in both chemistry and biology. Here we describe a simple, scalable two-step procedure to generate α-thio aromatic acids from aromatic amino acids with yields of up to 96%. Diazotization and α-lactone mediated bromination efficiently form the α-bromo acid with retention of configuration. Read More

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http://dx.doi.org/10.1016/j.tetlet.2018.02.030DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6101259PMC
March 2018
1 Read

Copper Mediated Coupling of 2-(Piperazine)-pyrimidine Iodides with Aryl Thiols using Cu(I)Thiophene-2-carboxylate.

Tetrahedron Lett 2017 Nov 23;58(48):4525-4531. Epub 2017 Oct 23.

Program in Chemical Biology, Sloan Kettering Institute, New York, NY 10065, USA.

A copper-mediated synthesis of diaryl sulfides utilizing Cu(I)-thiophene-2-carboxylate (CuTC) is described. We demonstrate the use of CuTC as a soluble, non-basic catalyst in the coupling of aryl iodides and aryl thiols in the synthesis of synthetically advanced diaryl sulfides. This method allows for the successful coupling of challenging substrates including -substituted and heteroaryl iodides and thiols. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.10.041DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6047360PMC
November 2017
3 Reads

One-step, stereoselective synthesis of octahydrochromanes the Prins reaction and their cannabinoid activities.

Tetrahedron Lett 2018 Feb 31;59(9):807-810. Epub 2018 Jan 31.

National Center for Natural Products Research, School of Pharmacy, The University of Mississippi, University, MS, 38677, USA.

Novel, functionalized octahydrochromene derivatives were synthesized in a single step the Prins reaction. Enantiomerically pure (+)-isopulegol was reacted with benzaldehyde to stereoselectively yield the corresponding octahydro-2-chromen-4-ol derivative containing five stereocenters. A total of 10 compounds were synthesized by altering the enantiomer of isopulegol and the substituted benzaldehyde, and the resulting enantiopure octahydrochromenes were screened against the cannabinoid receptor isoforms CB1 and CB2. Read More

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http://dx.doi.org/10.1016/j.tetlet.2018.01.040DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5986293PMC
February 2018
9 Reads

Thio acid-mediated conversion of azides to amides - exploratory studies en route to oroidin alkaloids.

Tetrahedron Lett 2017 Oct 24;58(41):3913-3918. Epub 2017 Aug 24.

Department of Chemistry and Biochemistry, 700 Planetarium Place, University of Texas at Arlington, TX 76019, USA.

The utility of the thio acid-azide coupling reaction to afford amides is explored in imidazole-containing substrates for application in the total synthesis of examples of oroidin alkaloids. Good yields of the expected amides are obtained in both monomeric and dimeric substrates. Bis azides react preferentially at the 2-azido position but hydrosulfenylation and reduction interfere. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.08.050DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969537PMC
October 2017
2 Reads

Sobralene, a new sex-aggregation pheromone and likely shunt metabolite of the taxadiene synthase cascade, produced by a member of the sand fly species complex.

Tetrahedron Lett 2018 May;59(20):1921-1923

School of Chemistry, The University of Nottingham, University Park, Nottingham NG7 2RD, UK.

A new sex-aggregation pheromone, sobralene, produced by the sand fly from Sobral (Ceará State, Brazil) is shown to have the novel 6,12-membered ring-fused diterpene structure It is proposed that sobralene is a likely shunt metabolite of the taxadiene synthase-catalysed cyclisation of geranygeranyl diphosphate. Read More

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http://dx.doi.org/10.1016/j.tetlet.2018.03.088DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5937913PMC
May 2018
3 Reads

An Expedient Synthesis of Murrayaquinone A via a Novel Oxidative Free Radical Reaction.

Tetrahedron Lett 2018 Feb 4;59(6):550-553. Epub 2018 Jan 4.

Department of Chemistry, University of Alabama at Birmingham, 901 14th Street South, Birmingham, AL 35294-1240, USA.

Murrayaquinones A-D is a group of four bioactive carbazole-1,4-dione natural products isolated from the root bark of the plant hayata. Murrayaquinone is synthesized in five steps starting from the commercially available 2,4,5-trimethoxybenzaldehyde with an overall yield of 45%. The novelty of this murrayaquinone synthesis is in the use of a Mn(OAc) mediated oxidative radical reaction of a N-benzylaminoquinone derivative with 2-cyclohexen-1-one for the late-stage indole ring construction. Read More

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http://dx.doi.org/10.1016/j.tetlet.2018.01.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5935454PMC
February 2018
2 Reads

A practical microwave method for the synthesis of fluoromethy 4-methylbenzenesulfonate in -amyl alcohol.

Tetrahedron Lett 2018 Apr;59(17):1635-1637

Division of Radiotherapy and Imaging, Institute of Cancer Research, London SW7 3RP, UK.

Fluorine substitution is an established tool in medicinal chemistry to favourably alter the molecular properties of a lead compound of interest. However, gaps still exist in the library of synthetic methods for accessing certain fluorine-substituted motifs. One such area is the fluoromethyl group, particularly when required in a fluoroalkylating capacity. Read More

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http://dx.doi.org/10.1016/j.tetlet.2018.03.039DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5896226PMC
April 2018
3 Reads

Isolation of amoenamide A and five antipodal prenylated alkaloids from NRRL 35600.

Tetrahedron Lett 2017 Jul 18;58(29):2797-2800. Epub 2017 May 18.

Graduate School of Pharmaceutical Sciences, Kumamoto University, Oe-honmachi 5-1, Kumamoto 862-0973, Kumamoto, Japan.

A new prenylated alkaloid, Amoenamide A (), was isolated from the fungus NRRL 35600. Previously, was postulated to be a precursor of Notoamide E4 () converted from Notoamide E (), which was a key precursor of the prenylated indole alkaloids in the fungi of the genus . We previously succeeded in the isolation of two pairs of antipodes, Stephacidin A () and Notoamide B (), from and MF297-2 and expected the presence of other antipodes in the culture of . Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.05.057DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5881583PMC
July 2017
3 Reads

Synthesis of a novel fused pyrrolodiazepine-based library with anti-cancer activity.

Tetrahedron Lett 2018 Apr 8;59(15):1513-1516. Epub 2018 Mar 8.

Center for Molecular Innovation and Drug Discovery, Northwestern University, Evanston, Illinois, 60208, United States.

Development of drugs for new and persistent diseases will increasingly rely on the expansion of accessible chemical space to allow exploration of novel molecular targets. Here we report the synthesis of a library of novel fused heterobicyclic small molecules based on the 1,4-diazepine and 2,4-pyrrolidinedione scaffolds. Key chemical transformations included a Mannich-type condensation and chemoselective N-acylation reactions. Read More

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http://dx.doi.org/10.1016/j.tetlet.2018.03.021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5877814PMC
April 2018
2 Reads

Tricine as a convenient scaffold for the synthesis of -terminally branched collagen-model peptides.

Tetrahedron Lett 2018 Jan 5;59(2):130-134. Epub 2017 Dec 5.

Department of Chemistry and Biochemistry, Florida Atlantic University, 777 Glades Rd, Boca Raton, FL 33431.

A novel and convenient method for the synthesis of -terminally branched collagen-model peptides has been achieved using tricine (-[tris(hydroxymethyl)methyl]glycine) as a branching scaffold and 1,2-diaminoethane or 1,4-diaminobutane as a linker. The peptide sequence was incorporated directly onto the linker and scaffold during solid-phase synthesis without additional manipulations. The resulting branched triple-helical peptides exhibited comparable thermal stabilities to the parent, unbranched sequence, and served as substrates for matrix metalloproteinase-1 (MMP-1). Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.12.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5846494PMC
January 2018
2 Reads

Absolute Configurations of Griseorhodins A and C.

Tetrahedron Lett 2017 Dec 7;58(50):4721-4723. Epub 2017 Nov 7.

Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, 14040-903, Ribeirão Preto, SP, Brazil.

The known antibiotic and cytotoxic compounds griseorhodin A () and griseorhodin C () were produced in solid culture by AB10, which was isolated from the leaf-cutter ant . Their absolute configurations were unambiguously established as 6,6a,7,8 and 6,6a,7,8, respectively, using vibrational circular dichroism (VCD) and density functional theory (DFT) calculations. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.11.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5828249PMC
December 2017
1 Read

Synthesis of -alkoxy-substituted 2-benzimidazoles.

Tetrahedron Lett 2017 Dec 6;58(50):4717-4720. Epub 2017 Nov 6.

C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506-6045, United States.

Treatment of 2-nitro--(2-methyl-1-propen-1-yl)benzenamines with potassium -butoxide in -butanol followed by the addition of an electrophile affords -alkoxy-2-benzimidazoles. Electrophiles including methyl iodide, allylic bromides, propargylic bromides, benzyl bromide, and acetyl chloride gave good to excellent yields of product while 1-iodo- and 2-iodo-butane afforded very low yields. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.11.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5830180PMC
December 2017
3 Reads

The synthesis of lactone-bridged 1,3,5-triphenylbenzene derivatives as pi-expanded coumarin triskelions.

Tetrahedron Lett 2017 Dec 6;58(50):4703-4708. Epub 2017 Nov 6.

Department of Chemistry, University of Wisconsin-Eau Claire, Eau Claire, WI, 54702, United States.

Two triply lactone-bridged 1,3,5-triphenylbenzene derivatives with solubilizing moieties have been synthesized in five and six steps from commercially available starting materials. Compounds containing the 1,3,5-triphenylbenzene core with two atom bridges are relatively unknown. This new class of pi-expanded coumarins contain triskelion architectures and X-ray crystallographic studies of one of the triskelions indicates that the 1,3,5-triphenylbenzene core adopts a near-planar geometry. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.11.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5804744PMC
December 2017
4 Reads

Tandem synthesis of 1-formyl-1,2,3-triazoles.

Tetrahedron Lett 2017 Nov 13;58(47):4450-4454. Epub 2017 Oct 13.

Department of Chemistry, Creighton University, 2500 California Plaza, Omaha, NE 68178, U.S.A.

A tandem method for preparing 4-formyl-1,2,3-triazoles via a two-step one-pot acetal cleavage/CuAAC reaction was developed. Using this method, 4-formyl-1,2,3-triazole analogs with both electron-withdrawing and electron-donating substituents were prepared in good yield and purity. Expansion of this method to a three-step tandem reaction that incorporates an additional step of azide substitution was also successful, circumventing the need for organic azide isolation. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.10.023DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5798646PMC
November 2017
2 Reads

A convergent, scalable and stereoselective synthesis of azole CYP51 inhibitors.

Tetrahedron Lett 2017 Nov 25;58(45):4248-4250. Epub 2017 Sep 25.

Departments of Chemistry and Biochemistry, Institute of Chemical Biology, Vanderbilt University, Nashville, TN 77842-3012, USA.

The study and development of azole-based CYP51 inhibitors is an active area of research across disciplines of biochemistry, pharmacology and infectious disease. Support of in vitro and in vivo studies require the development of robust asymmetric routes to single enantiomer products of this class of compounds. Herein, we describe a scalable and enantioselective synthesis to VNI and VFV, the two potent inhibitors of protozoan sterol 14α-demethylase (CYP51) that are currently under consideration for clinical trials for Chagas disease. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.09.070DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5777588PMC
November 2017
13 Reads

Highly Stereoselective Asymmetric Aldol Routes to -Butyl-2-(3,5-difluorophenyl)-1-oxiran-2-yl)ethyl)carbamates: Building Blocks for Novel Protease Inhibitors.

Tetrahedron Lett 2017 Oct 14;58(43):4062-4065. Epub 2017 Sep 14.

Department of Chemistry and Department of Medicinal Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, United States.

Enantioselective syntheses of -butyl (()-2-(3,5-difluorophenyl)-1-(()-oxiran-2-yl)ethyl)carbamate and (()-2-(3,5-difluorophenyl)-1-(()-oxiran-2-yl)ethyl)carbamate are described. We utilized asymmetric - and -aldol reactions to set both stereogenic centers. We investigated ester-derived Ti-enolate aldol reactions as well as Evans' diastereoselective -aldol reaction for these syntheses. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.09.025DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5765997PMC
October 2017
34 Reads

CH interconversions: two non-pyrolytic syntheses of tricyclo[5.3.2.0]dodeca-2,5,9,11-tetraene.

Tetrahedron Lett 2018 Jan 12;59(3):284-286. Epub 2017 Dec 12.

San Francisco State University, Department of Chemistry and Biochemistry, 1600 Holloway Avenue, San Francisco, CA 954132, USA.

Herein, we describe two independent and non-pyrolytic syntheses of an important C12H12 hydrocarbon which had been prepared previously by gas phase thermolysis of compound 6. The first method is based on an unusual dipolar cycloaddition of dichloroketene onto bullvalene. After reductive dechlorination, a Shapiro-Heath reaction of the tosylhydrazone gave the title compound. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.12.042DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5759350PMC
January 2018
5 Reads

Green Synthesis of Halogenated Thiophenes, Selenophenes and Benzo[]selenophenes Using Sodium Halides as a Source of Electrophilic Halogens.

Tetrahedron Lett 2017 Feb 7;58(7):638-641. Epub 2017 Jan 7.

Department of Chemistry, University of West Florida, Pensacola, FL 32514-5750.

Herein, we report the first synthesis of chlorinated benzo[]selenophenes via environmentally friendly electrophilic chlorocyclization reaction using "table salt" as a source of "electrophilic chlorine" and ethanol as a solvent. In addition, the synthesis of diverse halogenated heterocycles, including 3-chloro, 3-bromo and 3-iodo thiophenes, selenophenes, and benzo[]selenophenes was successfully accomplished under the same environmentally benign reaction conditions. This methodology has several advantages over other previously reported reactions as it employs simple starting compounds, an environmentally friendly solvent, ethanol, and non-toxic inorganic reagents under mild reaction conditions, resulting in the high product yields. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.01.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5741090PMC
February 2017
18 Reads

Stereochemistry and Reactivity of the HPA-Imine Mannich Intermediate.

Tetrahedron Lett 2017 Oct 31;58(40):3879-3883. Epub 2017 Aug 31.

Department of Chemistry and Chemical Biology, Rutgers - The State University of New Jersey, 610 Taylor Rd., Piscataway, NJ 08854, USA.

Homophthalic anhydride (HPA) typically reacts rapidly with benzalimines to afford the formal [4+2] adduct, a 1,2,3,4-tetrahydroisoquinolin-1-one-4-carboxylic acid. The stereochemical outcome of this reaction is consistent with an open transition state comprising an iminium species and enolized HPA, leading to a short-lived amino-anhydride intermediate. In the case of --butylbenzalimine, this Mannich-type intermediate, which would normally cyclize at low temperature to a single isomer of the -lactam, is intercepted by base treatment to afford -lactam products. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.08.070DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5737782PMC
October 2017
4 Reads

Iodine-mediated rearrangements of diallylsilanes.

Tetrahedron Lett 2017 Aug 11;58(35):3406-3409. Epub 2017 Jul 11.

Department of Chemistry, Western Washington University, Bellingham, WA, 98225, USA.

Diallylsilanes can be made to rearrange upon treatment with I. Of the silanes tested, diallyldiphenylsilane showed the greatest propensity to undergo this intramolecular carbocation allylation process. After etherification of the initially formed iodosilane, the products from this transformation represent useful synthetic intermediates, suitable for alkylation and cross-metathesis/annulation reactions. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.07.045DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5730080PMC
August 2017
2 Reads

Selective alkylation/oxidation of -substituted isoindolinone derivatives: synthesis of -phthaloylated natural and unnatural α-amino acid analogues.

Tetrahedron Lett 2017 Sep 17;58(38):3730-3733. Epub 2017 Aug 17.

Department of Chemistry, University of Louisville, 2320 South Brook Street, Louisville, Kentucky 40292 USA.

The interchangeability of the isoindolinone group as a nitrogen protecting group for amino acid intermediates is demonstrated by the preparation of several natural and unnatural α-amino acid derivatives using a two-carbon -isoindolinone (phthalimidine) scaffold. Using a selective benzylic oxidation, the -isoindolinone group is then converted to the -phthaloyl group for convenient removal (65-98%). For preparation of the isoindolinone products which were to be the substrates for benzylic oxidation, a range of side chains were installed on the isoindolinone-protected glycine equivalent on deprotonation to demonstrate the utility of the -protected isoindolinone synthon (51-93%). Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.08.032DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5722250PMC
September 2017
16 Reads

Synthesis of cananodine by intramolecular epoxide opening.

Tetrahedron Lett 2017 Aug 25;58(35):3478-3481. Epub 2017 Jul 25.

Department of Chemistry, Western Washington University, 516 High Street, Bellingham, WA 98225-9150.

Cananodine is a guaipyridine alkaloid with activity against liver cancer. Cananodine was synthesized using a remarkable intramolecular opening of a trisubstituted epoxide as the key step in construction of the seven-membered carbocycle of the target. The epoxide opening strategy allows all four stereoisomers of cananodine to be prepared. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.07.080DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5722248PMC
August 2017
6 Reads

An enantioselective enzymatic desymmetrization route to hexahydro-4-furopyranol, a high-affinity ligand for HIV-1 protease inhibitors.

Tetrahedron Lett 2017 Aug 3;58(33):3230-3233. Epub 2017 Jul 3.

Department of Chemistry and Department of Medicinal Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 479 07, United States.

An enantioselective synthesis of (a,,a)-hexahydro-4-furo[2,3-]pyran-4-ol, a high-affinity nonpeptide ligand for a variety of potent HIV-1 protease inhibitors is described. The key steps involved a highly enantioselective enzymatic desymmetrization of -diacetate, an efficient transacetalization, and a highly diastereoselective reduction of a ketone. This route is amenable to large-scale synthesis using readily available starting materials. Read More

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https://linkinghub.elsevier.com/retrieve/pii/S00404039173084
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http://dx.doi.org/10.1016/j.tetlet.2017.07.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5708567PMC
August 2017
11 Reads

Efficient route to pre-organized and linear polyaminopolycarboxylates: Cy-TTHA, Cy-DTPA and mono/di- reactive, -butyl protected TTHA/Cy-TTHA.

Tetrahedron Lett 2017 Apr 20;58(15):1441-1444. Epub 2017 Feb 20.

University of Illinois at Chicago, Department of Chemistry, 845 W. Taylor Street, MC 111, Chicago, IL 60607.

Pre-organized polyaminopolycarboxylate chelators Cy-TTHA and Cy-DTPA were synthesized via modular five-step syntheses from commercially available starting materials in ~ 62% and 47% overall yields, respectively. Furthermore, strategies are reported for the efficient preparation of mono- and di-reactive, -butyl-protected TTHA/Cy-TTHA to selectively functionalize central chelators' carboxylic acids. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.02.056DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5699510PMC
April 2017
6 Reads

Solid-phase synthesis of cyclic hexapeptides wollamides A, B and desotamide B.

Tetrahedron Lett 2017 Jul 25;58(27):2675-2680. Epub 2017 May 25.

Department of Pharmaceutical Sciences, The Daniel K. Inouye College of Pharmacy, University of Hawai'i at Hilo, 34 Rainbow Drive, Hilo, HI 96720, USA.

Solid-phase synthesis of antibacterial cyclohexapeptides including wollamides A, B and desotamide B has been developed. Briefly, the protected linear hexapeptides were assembled on 2-chlorotrityl chloride resin using standard Fmoc chemistry and diisopropylcarbodiimide/hydroxybenzotriazole coupling reagents, cleaved off-resin with hexafluoroisopropanol/dichloromethane to keep side-chain protecting groups intact, and cyclized in solution. Final global removal of all protecting groups using a cocktail of trifluoroacetic acid/triisopropylsilane/dichloromethane afforded the desired cyclic hexapeptides, which were characterized by H, C NMR, and HRMS. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.05.084DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5678967PMC
July 2017
2 Reads

Verbenanone, an octahydro-5H-chromen-5-one from a Hawaiian-Plant Associated Fungus FT431.

Tetrahedron Lett 2017 Jun 2;58(23):2290-2293. Epub 2017 May 2.

Department of Pharmaceutical Sciences, Daniel K. Inouye College of Pharmacy, University of Hawaii at Hilo, 200 West Kawili Street, Hilo, Hawai'i 96720, United States.

A new secondary metabolite verbenanone () with a unique (4a,8a)-octahydro-5H-chromen-5-one moiety has been obtained from the endophytic fungus FT431, which was isolated from the native Hawaiian plant sp. The structure of compound was characterized based on NMR and MS spectroscopic analysis. The absolute configuration (AC) of compound was determined by Mosher acids. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.04.096DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5676560PMC
June 2017
7 Reads

Asymmetric solution-phase mixture aldol reaction using oligomeric ethylene glycol tagged chiral oxazolidinones.

Tetrahedron Lett 2017 May 6;58(21):2031-2033. Epub 2017 Apr 6.

Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA.

Sorting tags are oligomeric structures that can be used as protecting groups or chiral auxiliaries enabling solution-phase mixture syntheses of multiple tagged compounds in one pot and allowing for facile and predictable chromatographic separation of products at the end of synthetic sequences. Perfluorinated hydrocarbon and oligomeric ethylene glycol (OEG) derivatives are known classes of sorting tags. Herein we describe the preparation of OEGylated chiral oxazolidinones and their use in asymmetric solution-phase mixture aldol reactions. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.04.026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5646709PMC
May 2017
4 Reads

Identification of an unexpected shunt pathway product provides new insights into tirandamycin biosynthesis.

Tetrahedron Lett 2016 Dec 19;57(52):5919-5923. Epub 2016 Nov 19.

Shandong Provincial Key Laboratory of Synthetic Biology, and CAS Key Laboratory of Biofuels at Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong 266101, China.

Tirandamycin K (), the first linear 7,13;9,13-diseco-tirandamycin derivative, was isolated from the (encoding the TamI P450 monooxygenase) disruption mutant strain () of marine sp. 307-9. Its chemical structure with relative and absolute configurations was elucidated by a combination of extensive spectroscopic analyses and biosynthetic inferences. Read More

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http://dx.doi.org/10.1016/j.tetlet.2016.11.080DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5628624PMC
December 2016
12 Reads

A Simple and Efficient Approach for the Synthesis of 2-Aminated Quinazoline Derivatives via Metal Free Oxidative Annulation.

Tetrahedron Lett 2017 Mar 12;58(13):1276-1279. Epub 2017 Feb 12.

Department of Pharmacy Sciences, School of Pharmacy and Health Professions, Creighton University, Omaha, Nebraska.

A simple and efficient approach for the synthesis of 2-aminoquinazoline derivatives in moderate to good yields. This reaction employs mild reaction conditions, is metal-free and utilizes readily available starting materials making it a more viable reaction for the scale up synthesis and ligand diversity. Notably, this methodology allows the synthesis of 2-aminoquinazolines using a free amine or cyclic amine enabling structural diversity and good atom economy. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.02.033DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5624717PMC
March 2017
6 Reads

-Chloroperbenzoic acid-oxchromium (VI)-mediated cleavage of 2,4,5-trisubstituted oxazoles.

Tetrahedron Lett 2017 Mar 14;58(13):1280-1282. Epub 2017 Feb 14.

Department of Chemistry, University of Louisville, 2320 South Brook Street, Louisville, Kentucky 40292 USA.

An array of 2-substituted-4,5-diphenyloxazoles were found to be cleaved to triacylamines and diacylamines (imides) using a reagent system composed of 3-chloroperbenzoic acid (MCPBA) and 2,2'-bipyridinium chlorochromate (BPCC). The 2-alkyl-4,5-diphenyloxazoles give imides (38-60%) as the predominant cleavage product while the 2-aryl-4,5-diphenyloxazoles give triacylamines (44-71%). Two mechanisms involving intermediates such as cyclic endoperoxides or oxachromacycles were proposed. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.02.027DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5621761PMC
March 2017
4 Reads

-β-Bromostyrene derivatives from cinnamic acids via a tandem substitutive bromination-decarboxylation sequence.

Tetrahedron Lett 2017 Oct 31;58(40):3894-3896. Epub 2017 Aug 31.

Department of Chemistry and Biochemistry, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132, USA.

-β-Bromostyrene derivatives were synthesized stereospecifically from cinnamic acids through β-lactone intermediates. The synthetic sequence did not require the purification of the β-lactone intermediates although they were found to be stable and readily purified in most cases. Read More

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https://linkinghub.elsevier.com/retrieve/pii/S00404039173109
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http://dx.doi.org/10.1016/j.tetlet.2017.08.069DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5619872PMC
October 2017
10 Reads

Competitive, substrate-dependent reductive debromination/dehydrobromination of 1,2-dibromides with triethylamine.

Tetrahedron Lett 2017 May 6;58(20):1973-1975. Epub 2017 Apr 6.

Department of Chemistry and Biochemistry, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132, USA.

The interaction of various 1,2-dibromides with NEt under various conditions (THF and DMF, respectively) at different temperatures was investigated. Our results from these reactions show that substrate dependent dehydrobrominations compete with reductive debrominations. A comprehensive discussion of these competitive pathways is offered. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.04.024DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5619868PMC
May 2017
9 Reads

Synthesis of highly substituted benzene ring systems through three-component coupling of enyne imines, Fischer carbene complexes, and electron-deficient alkynes.

Tetrahedron Lett 2017 Apr 24;58(14):1403-1407. Epub 2017 Feb 24.

Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, NM 88003 USA.

Three-component coupling of Fischer carbene complexes, enyne aldehyde hydrazones, and electron-deficient alkynes leads to simple benzoate derivatives in a process involving the formation of an N-aminopyrrole derivative, Diels-Alder reaction, and nitrene extrusion. The products are readily converted into isoquinolones through reaction with primary amines. The reaction proceeds best with highly substituted and electron-rich pyrroles even though these are the sterically least favorable substrates, and this reactivity trend is supported by a computational study. Read More

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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5619673PMC
April 2017
15 Reads

Syntheses of three naturally occurring polybrominated 3,3'-bi-1-indoles.

Tetrahedron Lett 2017 Mar 3;58(11):1053-1056. Epub 2017 Feb 3.

C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506-6045, United States.

The naturally occurring polybrominated indoles 2,2',5,5'-tetrabromo-3,3'-bi-1-indole, 2,2',6,6'-tetrabromo-3,3'-bi-1-indole, and 2,2',5,5',6,6'-hexabromo-3,3'-bi-1-indole were synthesized using a palladium catalyzed, carbon monoxide mediated, double reductive -heterocyclization of 2,3-bis(2-nitro-4(or 5)-bromophenyl)-1,4-butadienes as the key step. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.01.103DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5617639PMC
March 2017
8 Reads

Zinc Mediated Direct Transformation of Propargyl -hydroxylamines to α,β-Unsaturated Ketones and Mechanistic Insight.

Tetrahedron Lett 2017 Mar 7;58(12):1086-1089. Epub 2017 Feb 7.

Department of Chemistry & Biochemistry, Jackson State University 1400 J. R. Lynch St, PO Box 17910, Jackson, Ms 39217, USA.

A Lewis acid catalyzed direct transformation of propargyl -hydroxylamines to α,β-unsaturated ketones in the presence of aqueous Zn(II)-salts has been described. This investigation also provides a novel observation for the stoichiometric role of Zn-halides over what is known to date for catalytic processes. A thorough mechanistic study has been established based on the experiment using O-labeled water in optimized reaction conditions; the incorporation of O in the desired product was also substantiated by HRMS. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.01.045DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5612435PMC
March 2017
8 Reads

Acetone promoted 1,4-migration of an alkoxycarbonyl group on a syn-1,2-diamine.

Tetrahedron Lett 2017 Feb 3;58(7):597-601. Epub 2017 Jan 3.

John Jay College of Criminal Justice, New York, 524 west 59 Street, New York, NY, 10019, USA.

A 2-protected cis-amino mitosene undergoes an irreversible acetone promoted isomerization and converts to the 1-isomer. Kinetic studies and DFT calculations of the reaction are reported. An organocatalytic mechanism is proposed, involving a covalent intermediate formed by reaction of the mitosene and acetone. Read More

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http://dx.doi.org/10.1016/j.tetlet.2016.12.047DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5604470PMC
February 2017
2 Reads

Conversion of Methyl Ketones and Methyl Sulfones into α-Deutero-α,α-Difluoromethyl Ketones and α-Deutero-α,α-Difluoromethyl Sulfones in Three Synthetic Steps.

Tetrahedron Lett 2017 Feb 21;58(5):396-400. Epub 2016 Dec 21.

Department of BioMolecular Sciences, University of Mississippi, University, Mississippi, 38677, USA.

Deuterodifluoromethyl ketones and sulfones were assembled in three synthetic steps from methyl ketones and sulfones, respectively. The key synthetic transformation is the deuteration of the difluorocarbanion generated by the release of trifluoroacetate from highly α-fluorinated gem-diols. High levels of deuterium on the "CFD" group were routinely observed. Read More

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http://dx.doi.org/10.1016/j.tetlet.2016.12.018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5608106PMC
February 2017
16 Reads

Asymmetric Synthesis of All-Carbon Quaternary Spirocycles via a Catalytic Enantioselective Allylic Alkylation Strategy.

Tetrahedron Lett 2017 Aug 5;58(34):3341-3343. Epub 2017 Jul 5.

The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Blvd, MC 101-20, Pasadena, California 91125, United States.

Rapid access to enantioenriched spirocycles possessing a 1,4-dicarbonyl moiety spanning an all-carbon quaternary stereogenic spirocenter was achieved using a masked bromomethyl vinyl ketone reagent. The developed protocol entails an enantioselective palladium-catalyzed allylic alkylation reaction followed by a one-pot unmasking/RCM sequence that provides access to the spirocyclic compounds in good yields and selectivities. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.07.022DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5578629PMC
August 2017
5 Reads

Efficient synthesis of CN2097 using in situ activation of sulfhydryl group.

Tetrahedron Lett 2017 Aug 23;58(31):3053-3056. Epub 2017 Jun 23.

Center for Targeted Drug Delivery, Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Harry and Diane Rinker Health Science Campus, Irvine, California 92618, USA.

CN2097 (RCs-sCYK[KTE(β-Ala)]V) is a rationally designed peptidomimetic that shows effectiveness in preclinical models for the treatment of neurological disorders, such as Angelman syndrome, traumatic brain injury (TBI) and stroke. Because of its therapeutic activity for the treatment of human CNS disorders, there was an urgent need to develop an efficient strategy for large-scale synthesis of CN2097. The synthesis of CN2097 was accomplished using Fmoc/tBu solid phase chemistry in multiple steps. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.06.066DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5557301PMC
August 2017
22 Reads

Allenyl esters as quenching agents for ruthenium olefin metathesis catalysts.

Tetrahedron Lett 2017 Jan 30;58(1):106-108. Epub 2016 Nov 30.

Department of Chemistry and Biochemistry, Florida Atlantic University, Boca Raton, FL 33431.

In the attempt to synthesize substituted allenyl esters through a metathesis coupling of unsubstituted allenyl esters and alkenes using a variety of ruthenium catalysts, it was discovered that allenyl esters themselves cleanly arrested the activity of the catalysts. Further studies suggests possible utility of allene esters as general quenching agents for metathesis reactions. To explore this idea, several representative olefin metathesis reactions, including ring closing, were successfully terminated by the addition of simple allenyl esters for more convenient purification. Read More

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http://dx.doi.org/10.1016/j.tetlet.2016.11.121DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5475365PMC
January 2017
2 Reads

Multigram-scale Synthesis of Enantiopure 3,3-Difluoroproline.

Tetrahedron Lett 2016 Dec 3;57(50):5658-5660. Epub 2016 Nov 3.

Department of Molecular Therapeutics, The Scripps Research Institute, Scripps Florida, 130 Scripps Way #A2A, Jupiter, FL 33458, USA.

An efficient route for the synthesis of enantiopure 3,3-difluoroproline on multigram-scale is described herein. The deoxofluorination can be achieved with DAST on the corresponding racemic pyrrolidinone in good yield. Resolution of the racemate by crystallization with D- and L-tyrosine hydrazide provides both enantiomers of 3,3-difluoroproline in high yield and ee%. Read More

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http://dx.doi.org/10.1016/j.tetlet.2016.11.012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5456297PMC
December 2016
6 Reads

Synthesis and incorporation of a caged tyrosine amino acid possessing a bioorthogonal handle.

Tetrahedron Lett 2016 Oct 10;57(42):4709-4712. Epub 2016 Sep 10.

Department of Chemistry, College of William & Mary, P.O. Box 8795, Williamsburg, VA 23187, USA.

Reversing a bioconjugation in a spatial and temporal fashion has widespread applications, especially toward targeted drug delivery. We report the synthesis and incorporation of an unnatural amino acid with an alkyne modified dimethoxy--nitrobenzyl caging group. This unnatural amino acid can be utilized in a Glaser-Hay conjugation to generate a bioconjugate, but also is able to disrupt the bioconjugate when irradiated with light. Read More

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http://dx.doi.org/10.1016/j.tetlet.2016.09.033DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5438197PMC
October 2016
16 Reads

Synthesis of olefins via a Wittig reaction mediated by triphenylarsine.

Tetrahedron Lett 2017 Apr 22;58(14):1379-1381. Epub 2017 Feb 22.

University of Nevada, Reno 1664 N. Virginia Street, Reno, Nevada, 89557, United States.

An arsine-mediated Wittig reaction for the synthesis of olefins is described. After heating triphenylarsine in the presence of an activated alkyl bromide for 30 minutes, the resulting arsonium salt condensed with aldehydes in as little as 5 minutes at room temperature, yielding the olefins in high yields. Aromatic, heteroaromatic, and alkyl aldehydes were all suitable substrates for this process. Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.02.051DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5414584PMC
April 2017
4 Reads

An alternative synthesis of Vandetanib (Caprelsa™) a microwave accelerated Dimroth rearrangement.

Tetrahedron Lett 2017 Apr;58(15):1467-1469

Division of Radiotherapy and Imaging, Institute of Cancer Research, London SW7 3RP, UK.

Vandetanib is an orally available tyrosine kinase inhibitor used in the treatment of cancer. The current synthesis proceeds an unstable 4-chloroquinazoline, using harsh reagents, in addition to requiring sequential protection and deprotection steps. In the present work, use of the Dimroth rearrangement in the key quinazoline forming step enabled the synthesis of Vandetanib in nine steps (compared to the previously reported 12-14). Read More

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http://dx.doi.org/10.1016/j.tetlet.2017.02.082DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5381755PMC
April 2017
12 Reads

Synthesis of Site-Specifically C Labeled Linoleic Acids.

Tetrahedron Lett 2016 Oct 22;57(41):4537-4540. Epub 2016 Aug 22.

Department of Chemistry, University of California, Berkeley, Berkeley, California, 94720; Quantitative Institutes of Biosciences, University of California, Berkeley, Berkeley, California, 94720; Department of Molecular and Cellular Biology, University of California, Berkeley, Berkeley, California, 94720.

Soybean lipoxygenase-1 (SLO-1) catalyzes the C-H abstraction from the reactive carbon (C-11) in linoleic acid as the first and rate-determining step in the formation of alkylhydroperoxides. While previous labeling strategies have focused on deuterium labeling to ascertain the primary and secondary kinetic isotope effects for this reaction, there is an emerging interest and need for selectively enriched C isotopologues. In this report, we present synthetic strategies for site-specific C labeled linoleic acid substrates. Read More

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http://dx.doi.org/10.1016/j.tetlet.2016.08.071DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5333924PMC
October 2016
10 Reads