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    Preparation of S-glycoside surfactants and cysteine thioglycosides using minimally competent Lewis acid catalysis.
    Carbohydr Res 2016 Mar 6;422:1-4. Epub 2016 Jan 6.
    Department of Chemistry and Biochemistry, BIO5, The University of Arizona, 1306 E. University Blvd., Tucson, AZ 85721, USA. Electronic address:
    Here we report a method for the preparation of anomerically pure β-S-glycopyranosides (1,2-trans-glycosides) from the corresponding peracetate donors. S-glycosylation was performed in CHCl3 at reflux in the presence of a catalytic amount of InBr3. Deacylation of the intermediate peracetates were achieved under Zemplén conditions. Five pyranose examples, monosaccharides D-glucose and D-galactose and disaccharides cellobiose, maltose, and lactose, were used as donors, and five thiols including an α/ω dithiol and Fmoc-L-cysteine were used as acceptors. Melting points, high res MS, [α]D and NMR data ((1)H and (13)C, including COSY, HSQC and HMBC) are reported for compounds not previously described.

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    Glycosylation of α-amino acids by sugar acetate donors with InBr3. Minimally competent Lewis acids.
    Carbohydr Res 2012 Apr 28;351:121-5. Epub 2012 Jan 28.
    Carl S. Marvel Laboratories, Department of Chemistry & Biochemistry, The University of Arizona, Tucson, AZ 85721, USA.
    A simplified method for the preparation of Fmoc-serine and Fmoc-threonine glycosides for use in O-linked glycopeptide synthesis is described. Lewis acids promote glycoside formation, but also promote undesired reactions of the glycoside products. Use of 'minimally competent' Lewis acids such as InBr(3) promotes the desired activation catalytically, and with greatly reduced side products from sugar peracetates. Read More
    In(III) triflate-mediated solvent-free synthesis and activation of thioglycosides by ball milling and structural analysis of long chain alkyl thioglycosides by TEM and quantum chemical methods.
    J Org Chem 2014 Apr 8;79(8):3427-39. Epub 2014 Apr 8.
    Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research , S.A.S. Nagar, Punjab 160062, India.
    Conventional solution-phase synthesis of thioglycosides from glycosyl acetates and thiols in the presence of In(III) triflate as reported for benzyl thioglucoside failed when applied to the synthesis of phenolic and alkyl thioglycosides. But, it was achieved in high efficiency and diastereospecificity with ease by solvent-free grinding in a ball mill. The acetates in turn were also obtained by the homogenization of free sugars with stoichiometric amounts of acetic anhydride and catalytic In(OTf)3 in the mill as neat products. Read More
    Lewis acids as α-directing additives in glycosylations by using 2,3-O-carbonate-protected glucose and galactose thioglycoside donors based on preactivation protocol.
    J Org Chem 2012 Jun 30;77(12):5255-70. Epub 2012 May 30.
    State Key Laboratory of Natural and Biomimetic Drugs and School of Pharmaceutical Sciences, Peking University, Xue Yuan Road No. 38, Beijing 100191, China.
    Catalytic or stoichiometric amounts of Lewis acids were found to be very effective α-directing additives in the stereoselective glycosylations of diverse 2,3-O-carbonate-protected glucose and galactose thioglycoside donors by preactivation protocol. The poor stereoselectivities of 4,6-di-O-acetyl-2,3-O-carbonate protected thioglycoside donors in glycosyl coupling reactions were greatly improved, and excellent α-stereoselectivities were achieved by the addition of 0.2 equiv of BF(3)·OEt(2). Read More
    FeCl3 mediated arylidenation of carbohydrates.
    Carbohydr Res 2011 Apr 21;346(5):534-9. Epub 2011 Jan 21.
    Department of Chemistry, Jadavpur University, Kolkata 700 032, India.
    Glycosides and thioglycosides based on monosaccharides in reaction with benzaldehyde dimethylacetal or p-methoxybenzaldehyde dimethyl acetal undergo FeCl(3)-catalyzed (20 mol%) regioselective 4,6-O-arylidenation producing the corresponding acetals in high yields. FeCl(3) also mediates acetalation of glycosides and thioglycosides of cellobiose, maltose, and lactose affording the corresponding 4',6'-O-benzylidene acetals, which were isolated after their acetylation in situ with acetic anhydride and pyridine. The combined yields (two steps) of these final products are also high (61-84%). Read More