Functionalized DMAP catalysts for regioselective acetylation of carbohydrates

New functionalized DMAPs having carboxylic acid functionality are developed for regioselective acylation of carbohydrates. In these catalysts, DMAP (4-(N, N-dimethylamino)pyridine) is linked with -COOH (-COOMe or -OSO3H in reference catalysts) via methylene spacers of different length at the dimethylamino moiety. Utilizing one of these catalysts, 3-[N-decyl-N-(4-pyridyl)amino]propionic acid (1), regioselectivity for the primary 6-OH group in acetylation of 1-O-octyl beta-D-glucopyranoside is increased from 16% to 89% with rather improved catalytic activity compared with the parent DMAP. Catalyst 1 regioselectively acetylates both anomers of 1-0-octyl glucopyranosides (89% and 88% regioselectivity for beta- and alpha-anomer, respectively) and 1-O-octyl galactopyranosides (100% regioselectivity for both anomers) at position 6 in CHCl3, but gives nearly 1:1 mixtures of 4- and 6-monoacetates in the case of 1-O-octyl mannopyranosides. Control experiments are done to investigate the mechanistic aspects of regiocontrol. (C) 2002 Elsevier Science Ltd. All rights reserved.