UNEXPECTED PRODUCTS IN THE LIALH4 ALCL3-REDUCTION OF 3-O-SUBSTITUTED AND N-BENZYLOXYCARBONYL-PROTECTED 4,6-O-[2-METHOXYBENZYLIDENE]-ALPHA-D-GLUCOSAMINE DERIVATIVES/

The reductive cleavage of benzyl 6-O-(2-methoxybenzylidene)-alpha-D-gl ucopyranoside 2 with LiAlH4-AlCl3 gave the corresponding 4-O-(2-methox ybenzyl) ether along with the 6-O-ether as expected. When, however, th e 3-hydroxyl group was substituted, acetal cleavage was not the main r eaction path. With a 3-O-allyl or a 3-O-methyl group, the unsymmetrica l urea derivatives 8 resulted together with the formamido and N-methyl amino derivatives 9 and 10, respectively, and no acetal cleavage was o bserved. 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-methyla mino derivatives with intact 2-methoxybenzylidene group.