Treatment of 1,2:5,6-di-O-isopropylidene-α-D-ribo-hexofuranos-3-ulose (1) with sodium cyanide in anhydrous ethanol followed by addition of an equimolar amount of methyl nitro-acetate gave 3-C-cyano-1,2:5,6-di-O-isopropylidene-α-D-glucofuranose (2) in 57% yield. When methyl nitroacetate was first added to sodium cyanide in alcohol followed by the addition of ketose 1 then the allo-cyanohydrin epimer 4 was produced in 85% yield. 3-C-(Carbomethoxy-R,S-nitromethyl)-1,2:5,6-di-O-isopropylidene-α-D-allofuranose (6) was produced in low yield in the latter reaction and was isolated and characterized as its 3-O-acetate derivative 7. Selective acetolysis of the 5,6-O-isopropylidene group of the branched-chain sugars was achieved using acetic anhydride and p-toluenesulfonic acid monohydrate. The proof of structure of the cyano-hydrins is described.
Unusual Reaction of Azoxybenzenes withp-Toluenesulfonic Acid in Acetic Anhydride