Syntheses of methyl (4,6-dideoxy-alpha-L-lyxo-hexopyranosyl)-(1-->3)- and (4-deoxy-4-fluoro-alpha-L-rhamnopyranosyl)-(1-->3)- 2-acetamido-2-deoxy-alpha-D-glucopyranosides, analogs of the mycobacterial arabinogalactan linkage disaccharide

We have made thioglycoside donors for the 4,6-dideoxy-L-lyxo-hexopyranosyl ('4-deoxy-L-rhamnosyl') and 4-deoxy-4-fluoro-L-rhamnosyl monosaccharide residues. The preparation of the deoxyfluororhamnose was not straightforward, and revealed some unexpected behavior of the diethylaminosulfur trifluoride (DAST) reagent. The new glycosyl donors were used to synthesize two analogs of the mycobacterial arabinogalactan linkage disaccharide -->4)-alpha-L-Rha-(1-->3)-alpha-D-GlcNAc. These analogs are prototypes for a family of potential inhibitors of the enzymes involved in the early stages of cell-wall construction in mycobacteria.