A highly stereoselective intramolecular aldol condensation. Part II. Synthesis of D,L-hamamelose from 2,2′-O-methylene-bis-D-glycerose

D,L-Hamamelose (2-C-hydroxymethyl-D,L-ribose) has been synthesized from 2,2′-O-methylene-bis-D-glycerose by application of the sequential reactions aldol condensation, mercaptolysis, and demercaptalation. The structures of the intermediate thioglycosides of D,L-hamamelose have been established by use of 1 Hmr and 13 Cmr spectroscopy. The exact composition of the equilibrium mixture of D,L-hamamelose in aqueous solution has also been established by the concomitant use of 1 Hmr and 13 Cmr spectroscopy. D-Hamamelose has been obtained from the D,L-mixture by preferential crystallization.