Reaction of methyl β-d-glycero-l-manno-heptopyranoside with cyclohexanone: Synthesis of the 4- and 6-methyl ethers of d-glycero-l-manno-heptitol

Acid-catalysed condensation of methyl β-d-glycero-l-manno-heptopyranoside with cyclohexanone yielded an approximately 3:1 mixture of the 2,3:6,7- and 2,3:4,7-di-O-cyclohexylideneheptosides (1 and 2), which could be separated either as their benzoates (3 and 4) or as their methyl ethers (5 and 6). The latter compounds afforded the 4- and 6-methyl ethers (7 and 8) of d-glycero-l-manno-heptitol.