PREPARATION OF ACETYLATED 1-FLUOROGLYCOPYRANOSYL CYANIDES

Reactions of acetylated 1-bromo-1-deoxy-glycopyranosyl cyanides of bet a-D-galacto (2) and alpha-D-arabino (12) configurations with silver fl uoride in acetonitrile at room temperature gave the corresponding 1-de oxy-1-fluoroglycopyranosyl cyanides (5 and 13. respectively) with inve rsion of the anomeric centre. Under similar conditions the beta-D-gluc o (1) and beta-D-xylo (3) compounds resulted in the corresponding inve rted 1-fluoroglycosyl cyanides (4 and 6, respectively) together with s ignificant amounts of 1-cyano-2-hydroxy-glycals (9 and 10, respectivel y). Silver tetrafluoroborate in toluene at room temperature converted 2 and 3 into the 1-fluoroglycosyl cyanides (7 and 8, respectively) of retained anomeric configuration. 1-Chloro-l-deoxy-alpha-D-galactopyran osyl cyanide (11) also gave 7 with silver fluoride in acetonitrile at reflux temperature. Conformational equilibria of the 1-deoxy-1-fluoro- pentopyranosyl cyanides 6, 8, and 13 reflect counteraction of the anom eric effects exerted by the fluorine and the cyano group. 1-Deoxy-1-fl uoro-alpha-D-galactopyranosyl cyanide proved to be a weak competitive inhibitor of E. coli beta-D-galactosidase (K-i = 2 mM). (C) 1998 Elsev ier Science Ltd. All rights reserved.