Unexpected Products in the Lialh4/Alcl3-Reduction of 3-O-Substituted and N-Benzyloxycarbonyl-Protected 4,6-O-[2-Methoxybenzylidene]-α-D-Glucosamine Derivatives

Abstract

The reductive cleavage of benzyl 2-benzyloxycarbonylamino-2-deoxy-4,6-O-(2-methoxybenzylidene)-α-D-glucopyranoside 2 with LiAlH4-AlCl3 gave the corresponding 4-O-(2-methoxybenzyl) ether along with the 6-O-ether as expected. When, however, the 3-hydroxyl group was substituted, acetal cleavage was not the main reaction path. With a 3-O-allyl or a 3-O-methyl group, the unsymmetrical urea derivatives 8 resulted together with the formamido and N-methylamino derivatives 9 and 10, respectively, and no acetal cleavage was observed. Substitution at O-3 with a benzyl group allowed the formation of a small amount of 4-O-ether along with the formamido and N-methylamino derivatives with intact 2-methoxybenzylidene group. 1. Summer student 1996 from the Institut Universitaire Professionalisé Orléans, France. 2. Summer student 1995 from the Institut Universitaire Professionalisé Orléans, France.