Benzylidene acetal fragmentation route to 6-deoxy sugars: direct reductive cleavage in the presence of ether protecting groups, permitting the efficient, highly stereocontrolled synthesis of beta-D-rhamnosides from D-mannosyl glycosyl donors. Total synthesis of alpha-D-Gal-(1-->3)-alpha-D-Rha-(1-->3)- beta-D-Rha-(1-->4)-beta-D-Glu-OMe, the repeating unit of the antigenic lipopolysaccharide from Escherichia hermannii ATCC 33650 and 33652

Journal of the American Chemical Society
David Crich, Qingjia Yao

Abstract

An approach to the stereocontrolled synthesis of beta-d-rhamnopyranosides is described in which 2,3-O-benzyl or related 4,6-O-[alpha-(2-(2-iodophenyl)ethylthiocarbonyl)benzylidene]-mannosyl thioglycosides are first used to introduce the beta-d-mannopyranoside linkage in high yield and stereoselectivity. Following glycosylation, treatment with tributyltin hydride in toluene at reflux brings about reductive radical fragmentation directly to the 6-deoxy sugar in high yield. A variation of these donors bearing a carboxylated donor on O3 is a highly alpha-selective mannosyl and, after radical fragmentation, alpha-d-rhamnosyl donor. Using this stereoselective glycosylation/radical-fragmentation approach, a concise synthesis of the title tetrasaccharide is realized in which both the beta-d- and alpha-d-rhamnopyranosyl units are obtained in a single step by a double radical fragmentation of the modified benzylidene acetals.

References

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Citations

Mar 23, 2007·The Journal of Organic Chemistry·David Crich, Olga Vinogradova
Aug 2, 2007·The Journal of Organic Chemistry·David CrichPrasanna Jayalath
Nov 21, 2009·The Journal of Organic Chemistry·David Crich, Sébastien Picard
Oct 7, 2006·Chemical Communications : Chem Comm·Carl H Schiesser
Jan 20, 2016·Journal of the American Chemical Society·Peng-Cheng GaoJin-Song Yang
Jan 21, 2017·Organic & Biomolecular Chemistry·Aritra Chaudhury, Rina Ghosh
Oct 23, 2010·Molecules : a Journal of Synthetic Chemistry and Natural Product Chemistry·Jian Guo, Xin-Shan Ye
Jan 29, 2009·Angewandte Chemie·Xiangming Zhu, Richard R Schmidt
Sep 5, 2009·Chemistry : a European Journal·Julien CoulombMax Malacria
Aug 8, 2015·Chemistry : a European Journal·Manishkumar A Chaube, Suvarn S Kulkarni
Mar 31, 2011·Organic & Biomolecular Chemistry·Sara H KyneLouis Fensterbank
Jul 6, 2013·Chemical Society Reviews·Fabrice DénèsPhilippe Renaud
Apr 25, 2008·Journal of the American Chemical Society·Yong Joo LeeYukishige Ito
Dec 10, 2008·The Journal of Organic Chemistry·Christabel T Tanifum, Cheng-Wei T Chang
May 26, 2010·Accounts of Chemical Research·David Crich
Apr 29, 2006·Carbohydrate Research·David Crich, Mitesh Patel
Sep 10, 2005·The Journal of Organic Chemistry·David CrichKrishnakumar Ranganathan
Aug 19, 2007·Journal of the American Chemical Society·Toshiki NokamiJun-ichi Yoshida

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