AN EXPEDITIOUS ROUTE TO STREPTOCOCCI AND ENTEROCOCCI GLYCOLIPIDS VIA RING-OPENING OF 1,2-ANHYDROSUGARS WITH PROTIC ACIDS

1,2-Anhydroglucose 6 reacts smoothly and with a high degree of stereos electivity with a variety of carboxylic and phosphoric acids resulting in the formation of the predominantly beta-oriented 1-O-acyl and 1-O- phosphorylglucoses 7-17. This methodology has been successfully applie d in the construction of glycolipids 1a,b. Ring-opening of the 1,2-anh ydroglucose derivative 19 with benzoic acid furnished exclusively the beta-aligned key intermediate 20. Subsequent ICDT-assisted chemoselect ive alpha-glucosylation of 20 with thioethyl donor 21, followed by gly cosidation of kojibiosyl benzoate 22 with glycerol acceptor 23 gave th e fully protected alpha-diglucosyl glycerol derivative 25, which upon desilylation (-->28), acylation (-->29 or 30) and deprotection afforde d the target glycolipids 1a-b in high overall yield.