Molybdic acid-catalysed isomerization of D-ribulose and D-xylulose to the corresponding 2-C-(hydroxymethyl)-D-tetroses

2-C-(Hydroxymethyl)-D-erythrose (2) and 2-C-(hydroxymethyl)-D-threose (4) have been stereospecifically synthesized in one-step by a molybdic acid-catalysed isomerization reaction from respective D-xylulose (1) and D-ribulose (3). In the case of interconversion of 1 to 2, the content of the 2-C-branched chain tetrose in the equilibrium mixture can be doubled if boric acid is present in the reaction mixture in addition to the catalyst.