SYNTHESIS OF A HEXASACCHARIDE ACCEPTOR CORRESPONDING TO THE REDUCING TERMINUS OF MYCOBACTERIAL 3-O-METHYLMANNOSE POLYSACCHARIDE (MMP)

The title compound methyl di-O-benzyl-3-O-methyl-alpha-D-mannopyranosy l)-[(1 --> 4)- O-benzyl-3-O-methyl-alpha-D-mannopyranosyl)](4)-(1 --> 4)-2,6-di-O-benzyl-3-O-methyl-alpha-D- mannopyranoside (2) was synthes ized in a blockwise manner, employing trichloroacetimidate (11) and (2 0) as glycosyl donors. The strategy relies on the single-step preparat ion of the 3-O-methyl ethers (4) and (12) as starting materials. Since all intermediates contain one or more OCH3 groups, they are easily id entified by NMR spectroscopy using the methyl proton signals, Compound 2 corresponds to the reducing terminal hexasaccharide of mycobacteria l 3-O-methylmannose polysaccharide (MMP). MMP has the unusual property of stimulating the fatty acid synthetase multienzyme complex. Compoun d 2 can serve as a suitable glycosyl acceptor for the synthesis of ext ended fragments of MMP. (C) 1996 Elsevier Science-Ltd.