Regioselective Galactofuranosylation for the Synthesis of Disaccharide Patterns Found in Pathogenic Microorganisms

J Org Chem. 2017 Jul 21;82(14):7114-7122. doi: 10.1021/acs.joc.7b00565. Epub 2017 Jun 28.

Abstract

Koenigs-Knorr glycosylation of acceptors with more than one free hydroxyl group by 2,3,5,6-tetrabenzoyl galactofuranosyl bromide was performed using diphenylborinic acid 2-aminoethyl ester (DPBA) as inducer of regioselectivity. High regioselectivity for the glycosylation on the equatorial hydroxyl group of the acceptor was obtained thanks to the transient formation of a borinate adduct of the corresponding 1,2-cis diol. Nevertheless formation of orthoester byproducts hampered the efficiency of the method. Interestingly electron-withdrawing groups on O-6 or on C-1 of the acceptor displaced the reaction in favor of the desired galactofuranosyl containing disaccharide. The best yield was obtained for the furanosylation of p-nitrophenyl 6-O-acetyl mannopyranoside. Precursors of other disaccharides, found in the glycocalix of some pathogens, were synthesized according to the same protocol with yields ranging from 45 to 86%. This is a good alternative for the synthesis of biologically relevant glycoconjugates.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacteria / chemistry*
  • Disaccharides / chemical synthesis*
  • Disaccharides / chemistry
  • Fungi / chemistry*
  • Furans / chemistry*
  • Galactosides / chemistry*
  • Glycosylation
  • Molecular Structure
  • Quantum Theory
  • Stereoisomerism
  • Trypanosomatina / chemistry*

Substances

  • Disaccharides
  • Furans
  • Galactosides