On Moffatt dehydration of glucose-derived nitro alcohols

Moffatt dehydration of 1,2:5,6-di-O-isopropylidene-α-d-glucofuranose derived nitro alcohols with a mixture of Ac2O and DMSO was reinvestigated. It was discovered that, regardless of the absolute configuration at C(3) of the sugar moiety, the dehydration provided exclusively the (3Z)-nitromethylene derivative. Slight modification of the workup conditions (pH ⩾ 8, temperature: 25–30 °C) gave exclusively a novel product, (3S)-3-deoxy-3-methylthio-3-C-nitromethyl-1,2:5,6-di-O-isopropylidene-α-d-glucofuranose. The latter was obtained by a Michael addition of thiomethylate anion to the previously reported nitromethylene derivative during the aqueous basic workup at ambient or slightly elevated temperature. The putative mechanism leading to the thiomethylate anion includes Pummerer rearrangement of DMSO and basic hydrolysis of thus formed methylsulfanylmethyl acetate.