Synthesis of a hexasaccharide acceptor corresponding to the reducing terminus of mycobacterial 3- O-methylmannose polysaccharide (MMP)

Abstract

The title compound methyl O-(2,6-di- O-benzyl-3- O-methyl- α-d-mannopyranosyl)-[(1 → 4)- O-(2,6-di- O-benzyl-3- O-methyl- α-d- mannopyranosyl)] 4-(1 → 4)-2,6-di- O-benzyl-3- O-methyl- α-d-mannopyranoside ( 2) was synthesized in a blockwise manner, employing trichloroacetimidate ( 11) and ( 20) as glycosyl donors. The strategy relies on the single-step preparation of the 3- O-methyl ethers ( 4) and ( 12) as starting materials. Since all intermediates contain one or more OCH 3 groups, they are easily identified by NMR spectroscopy using the methyl proton signals. Compound 2 corresponds to the reducing terminal hexasaccharide of mycobacterial 3- O-methylmannose polysaccharide (MMP). MMP has the unusual property of stimulating the fatty acid synthetase multienzyme complex. Compound 2 can serve as a suitable glycosyl acceptor for the synthesis of extended fragments of MMP.