Synthesis of Ethyl and Phenyl 1-Thio-1,2-trans-D-Glycopyranosides from the Corresponding Per-O-Acetylated Glycopyranoses having a 1,2-trans-Configuration using Anhydrous Ferric Chloride as a Promoter.

Abstract
The reaction between per-O-acetylated hexopyranoses and suitable thiols in the presence of anhydrous ferric chloride affords the corresponding thioglycosides. Thus, ethyl 1-thio-.beta.-D-glycopyranosides were prepared as per-O-acetates in gluco-, 2-acetamido-2-deoxy-gluco-, 2-deoxy-phthalimido-gluco-, and 2-chloroacetamido-2-deoxy-gluco-configurations. Ethyl 1-thio-.alpha.-D-mannopyranoside was prepared from a suitable per-O-acetate, as were phenyl tetra-O-acetyl-1-thio-.beta.-D-glucopyranoside, using thiophenol as the glycosylating agent. Prolonged reaction time adversely affects the yield. A reaction scheme is proposed that explains this observation.