Studies into the preparation of 1-deoxy-1-thiocyanato-D-glycopyranosyl cyanides and the anomeric effect of the thiocyanate group

The reaction of per-O-acetylated 1-bromo-1-deoxy-alpha -D-arabinopyranosyl cyanide with thiocyanate ions gave the corresponding 1-deoxy-1-thiocyanato- alpha- and beta -D-arabinopyranosyl cyanides. In the reaction of the per-O- acetylated 1-bromo-1-deoxy-beta -D-xylopyranosyl cyanide and its per-O-benz oylated beta -D-glucopyranosyl analogue the corresponding 2-hydroxy-glycal esters formed in addition to the anomeric pair of thiocyanato-cyanides. The formation of 2,3,4,6-tetra-O-benzoyl-alpha -D-glycopyranosyl thiocyanate w as demonstrated in the reaction of benzobromoglucose with thiocyanate ions. The equilibrium constant between 2,3,4,6-tetra-O-acetyl-1-deoxyl-1-thiocya nato-alpha- and beta -D-galactopyranosyl cyanides was determined. Based on this value, the equilibrium ratio for the 2.3.4,6-tetra-O-acetyl-alpha- and beta -D-galactopyranosyl thiocyanates was calculated to be 94:6, and the a nomeric effect of the SCN group was estimated to exceed 3 kcal/mol. X-Ray c rystallographic data support endo- and exo-anomeric effects of the SCN moie ty. (C) 2001 Elsevier Science Ltd. All rights reserved.