Synthesis and crystal structure of methyl 4-6-dideoxy-4-(3-deoxy-L- glycero-tetronamido)-2-O-methyl-alpha-D-mannopyranoside, the methyl alpha-glycoside of the terminal unit, and presumed antigenic determinant, of the O-specific polysaccharide of Vibrio cholerae O:1, serotype Ogawa.

Methyl 4-azido-4,6-dideoxy-3-O-benzyl-alpha-D-mannopyranoside and its analogous 3-O-(4-methoxybenzyl) derivative were methylated and the 2-O-methyl derivatives formed were converted into methyl 4-amino-4,6-dideoxy-2-O-methyl-alpha-D- mannopyranoside [sequence: see text]. Reaction of the latter with 3-deoxy-L-glycero-tetronolactone gave the methyl glycoside of 4,6-dideoxy-4-(3-deoxy-L-glycero- tetronamido)-2-methyl-alpha-D-mannopyranose [sequence: see text], the monosaccharide that is reported to be the terminal moiety of the O-specific polysaccharide of Vibrio cholerae O:1, serotype Ogawa. The unit cell packing of the compound, which crystallized as a monohydrate, differs from that of the previously described crystalline compound lacking the 2-O-methyl group. The unmethylated sugar is the terminal moiety of the O-specific polysaccharide of Vibrio cholerae O:1, serotype Inaba. The crystal structure of methyl 4,6-dideoxy-2-O- methyl-4-trifluoroacetamido-alpha-D-mannopyranoside [sequence: see text] is also described.