Synthesis and crystal structure of methyl 4,6-dideoxy-4-(3-deoxy-l-glycero-tetronamido) - 2-O-methyl-α-d-mannopyranoside, the methyl α-glycoside of the terminal unit, and presumed antigenic determinant, of the O-specific polysaccharide of Vibrio cholerae

Methyl 4-azido-4,6-dideoxy-3-O-benzyl-α-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-α-d-mannopyranoside. 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-O-methyl-α-d-mannopyranose, 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-α-d-mannopyranoside is also described.