Synthesis of the oligosaccharide segment of a novel phenolic glycolipid antigen from Mycobacterium haemophilum

Abstract

The synthesis of the trisaccharide segment from Mycobacterium haemophilum phenolic glucolipid has been described. The synthesis of the disaccharide derivative 12 containing a free hydroxy group at C-2′ was first examined by using 2-O-acetyl-4-O-benzyl-3-O-methyl-L-rhamnopyranosyltrichloroacetimidate 9 as a glycosyl donor and 10 as an aglycone followed by Zemplen deacetylation. The same glycosyl donor 9 was utilised for second coupling reaction with 12 to give the requisite trisaccharide 3 isolated after deacetylation, methylation and debenzylation. The high degrees of α-selectivity in both the coupling reactions were substantiated by using ¹H NMR, ¹³C NMR and partially decoupled ¹³C NMR spectral studies.