Synthesis of a Tetra- and a Hexasaccharide Donor Corresponding to the Non-Reducing Termini of Mycobacterial 3-O-Methylmannose Polysaccharide (MMP)

Abstract

The blockwise synthesis of the title compounds, namely the tetra- and the hexasaccharide trichloroacetimidates (20) and (23), is described. Both acetates and imidates were employed as glycosyl donors in most of the coupling reactions. As nearly all of the synthetic intermediates contain one or more OCH₃ groups, they are easily identified by NMR spectroscopy the methyl signals. The fully functionalized compounds 20 and 23 correspond to the non-reducing terminal fragments of mycobacterial 3-O-methylmannose polysaccharide (MMP), and can serve as suitable building blocks for the synthesis of higher-order structures of MMP.