Comparing the use of 2-methylenenapthyl, 4-methoxybenzyl, 3,4-dimethoxybenzyl and 2,4,6-trimethoxybenzyl as N–H protecting groups for p-tolyl 2-acetamido-3,4,6-tri- O-acetyl-2-deoxy-1-thio-β- d-glucosides

Abstract

A hurdle in glycosylation reactions of 2-acetamido glycosyl donors is the formation of a stable and unreactive oxazoline that decreases the yield of these reactions significantly. As an effort to prevent oxazoline formation during glycosylation reactions, we protected the N–H of the acetamido group within a 2-acetamido-2-deoxy-1-thio-β- d-glucoside with one of four different protecting groups. These groups were either 2-methylenenapthyl, 4-methoxybenzyl, 3,4-dimethoxybenzyl or 2,4,6-trimethoxybenzyl. The resulting N-alkylacetamides were then used in glycosylation reactions with ethanol as a model acceptor. We observed that the ethyl glycosides obtained in each case were obtained with exclusive β-selectivity without the formation of oxazoline sideproducts. The resulting products were then used to screen conditions for protecting group removal.