Cyclizations of dialdehydes with nitromethane. XIV. The isolation of four crystalline methyl 3,6-dideoxy-3-nitro-α-L-hexopyranosides

Abstract

Cyclization of L′-methoxy-L-methyldiglycolic aldehyde (1) with nitromethane and sodium methoxide in methanol (40 min at room temperature) furnished four crystalline methyl 3,6-dideoxy-3-nitro-α-L-hexopyranosides in a combined yield of 75%. Chromatographic separation gave the gluco (2), manno (3), talo (4), and galacto (5) isomers in an approximate ratio of 18:8:3:1. Shortening of the reaction time to 25 min decreased the total yield to 53% at the expense of 2, the ratio of isolated products being 8:8:2.3:1.7. The configurations of the new nitro glycosides 3, 4, and 5 were proven by catalytic hydrogenation followed by N-acetylation, which gave the known 3-acetamido derivatives.