Oxidative and reductive ring opening of endo‐3,4‐O‐(4‐methoxybenzylidene) acetals of 1, 6‐anhydro‐β‐D‐galactopyranoses

Cleavage of the endo‐3, 4‐O‐(4‐methoxybenzylidene) acetal rings of 1, 6‐anhydro‐β‐D‐galactopyranose derivatives with LiAlH4‐AlCl3, NaCNBH3‐HCl or NMe3‐AlCl3 gives predominantly axial 3‐O‐(4‐methoxybenzyl) ether derivatives. Oxidative opening of the same acetal functions with DDQ affords the corresponding 3‐O‐(4‐methoxybenzoyl) derivatives. The (4‐methoxybenzyl) group can be removed selectively with DDQ and survives acetolysis of the 1, 6‐anhydro bond.