Regioselective reductive ring opening of 4-methoxybenzylidene acetals of hexopyranosides. Access to a novel protective group strategy

Abstract

Reduction of fully protected 4,6,-O-(4-methoxybenzylidene)hexopyranosides with sodium cyanoborohydride-trifluoracetic acid in N,N-dimethylformamide, or with trimethylsilyl chloride in acetonitrile, gives the 6-and 4-O-(4-methoxybenzyl) ethers, respectively, in good yields and with good regioselectivity; the 4-methoxybenzyl ether linkage in products containing benzyl ethers or other protective groups is selectively cleaved upon treatment with cerium(IV) ammonium nitrate in aqueous acetonitrile.