A nitro sugar derivative route to 2-thioepisophorose and 2-thiosophorose and their remarkable facile epimerization.

The addition of 1-thio-D-glucose sodium salt to per-O-acetylated 1,2-dideoxy-1-nitro-D-arabino-hex-1-enitol, readily available from D-arabinose, afforded the corresponding 2-S-glycosylated 1-deoxy-1-nitro-D-mannitol and -D-glucitol peracetates. These, after deacetylation, were transformed by the Nef reaction to 2-thioepisophorose and 2-thiosophorose, respectively. The 2-thiodisaccharides easily epimerize in aqueous sodium bicarbonate at ambient temperature to a 1:4 equilibrium mixture. The predominant 2-thiosophorose was obtained crystalline. A 1H NMR study of the epimerization in deuterium oxide showed that the reaction involves an H-2 proton exchange mechanism.

Crystal and molecular structures of beta-cellobiosylnitromethane and of beta-maltosylnitromethane heptaacetate.

The structures of the title compounds have been determined by X-ray crystallography, using direct methods, and have been refined to conventional final residual factors of R = 0.063 and R = 0.046, respectively.