Toward the synthesis of fine chemicals from lactose: preparation of D-xylo and L-lyxo-aldohexos-5-ulose derivatives.

The transformation of (5R)-2,6-di-O-benzyl-5-C-methoxy-beta-D-galactopyranosyl-(1-->4)-2,3:5,6-di-O-isopropylidene-aldehydo-D-glucose dimethyl acetal (8) into partially protected derivatives of D-xylo- and L-lyxo-aldohexos-5-ulose has been reported, applying appropriate epimerisation methods to its 3'-O- and 4'-O-protected alcoholic derivatives.