CHEMICAL SYNTHESIS OF THE PYRUVIC ACETAL-CONTAINING TRISACCHARIDE UNIT OF THE SPECIES-SPECIFIC GLYCOPEPTIDOLIPID FROM MYCOBACTERIUM-AVIUM SEROVARIANT-8

The functionalized, pyruvic acetal-containing haptenic trisaccharide, p-trifluoroacetamidophenyl l]-alpha-L-rhamnopyranosyl}-alpha-L-talopyr anoside (19), a component of the glycolipid from Mycobacterium avium s erovar 8 was synthesized. For the preparation of the terminal pyruvic acetal-containing unit, benzyl 2-O-benzyl-3-O-methyl-beta-D-glucopyran oside (6) was condensed with methyl 2,2-di(ethylthio)propionate (1) in the presence of SO2Cl2-CF3SO3H catalyst to yield benzyl bonylethylide ne)-3-O-methyl-beta-D-glucopyranoside (7S), which was then converted i nto the suitably substituted glycosyl donor bonylethylidene)-3-O-methy l-alpha-D-glucopyranosyl trichloroacetimidate (11). The disaccharide g lycosyl acceptor p-nitrophenyl endo-3,4-O-benzylidene- yl-alpha-L-rham nopyranosyl)-alpha-L-talopyranoside (15) was glycosylated with 11 in t he presence of trimethyl trifluoromethanesulfonate to furnish the prot ected trisaccharide p-nitrophenyl bonylethylidene)-3-O-methyl-beta-D-g lucopyranosyl] -endo-3,4-O-benzylidene-6-deoxy-alpha-L-talopyrano side (16). After deprotection, this gave the spacer-armed unprotected hapt enic trisaccharide 19.