Stereospecific molybdic acid catalyzed isomerization of D-fructose to branched-chain aldose. The synthesis of D-hamamelose

One-step, stereospecific synthesis of D-hamamelose (2-C-(hydroxymethyl)-D-r ibose) by isomerization of D-fructose in mild acidic aqueous solution, unde r catalytic amount of molybdic acid, is described. The mechanism of this tr ansformation was proposed, studied, and confirmed. The data obtained with D -(2-C-13)fructose indicate that the rearrangement of 2-ketose to branched-c hain aldose is analogical to the mechanism of C-2-epimerization of aldoses catalyzed by molybdate ions. The structure of the branched-chain aldose, D- (2-C-13)hamamelose documents that the stereospecific reaction is accompanie d by the carbon skeletal rearrangement. The equilibrium mixture of D-fructo se and D-hamamelose is formed in the ratio of 14:1 regardless of the starti ng sugar, D-hamamelose or D-fructose.