Synthesis of tetrasaccharides related to the antigenic determinants from the glycopeptidolipid antigens of serovars 9 and 25 in the Mycobacterium avium-M. intracellulare-M. scrofulaceum serocomplex

Abstract

The synthesis of the tetrasaccharides O-(2,3-di-O-methyl-alpha-L-fucopyranosyl)-(1----4)-O-(2,3- di-O-methyl-alpha-L-fucopyranosyl)-(1----3)-O-alpha-L-rhamnopyranosyl -(1----2)-6-deoxyl-L-talose (36) and O-(2-O-methyl-alpha-L-fucopyranosyl)-(1----4)-O-(2-O-methyl-alpha-L- fucopyranosyl)-(1----3)-O-alpha-L-rhamnopyranosyl-(1----2)-6-deoxy-L- talose (41) is described. The former and the latter structures, respectively, have been proposed as the carbohydrate chains in the polar glycopeptidolipid antigens of serovars 9 and 25 in the Mycobacterium avium-M. intracellulare-M. scrofulaceum serocomplex. Glycosylation of allyl 2,3-di-O-methyl-alpha-L-fucopyranoside with 4-O-benzoyl-2,3-di-O-methyl-alpha-L-fucopyranosyl chloride gave the alpha-linked disaccharide derivative, which was O-deallylated and converted into the corresponding disaccharide alpha-chloride. This was coupled with benzyl 3,4-di-O-benzyl-6-deoxy-2-O-(2,4-di-O-benzoyl-alpha-L-rhamnopyranosyl)- alpha-L-talopyranoside (32) to give a fully protected tetrasaccharide derivative, which was deprotected to furnish 36. Likewise, 3-O-benzyl-4-O-(3,4-di-O-acetyl-2-O-methyl-alpha-L- fucopyranosyl)-2-O-methyl-alpha-L-fucopyranosyl chloride, prepared by way of condensation of allyl 3-O-benzoyl-2-O-methyl-alpha-L-fucopyranoside with 2-O-methyl-3,4-di-O-(p-nitrobenzoyl)-alpha-L-fucopyranosyl bromide, reacted with 32, to provide, after removal of blocking groups, 41.