The syntheses of 4,6-dideoxy-4,6-difluoro- and 4-deoxy-4-fluoro-α,α-trehalose

Abstract

Prolonged treatment of 2,3-di- O-benzyl-4,6-di- O-mesyl-α- d-glucopyranosyl 2,3-di- O-benzyl-4,6- O-benzylidene-α- d-glucopyranoside with tetrabutylammonium fluoride in acetonitrile gave the 4,6-difluoride (71 % yield), from which 4,6-dideoxy-4,6-difluoro-α- d-galactopyranosyl α- d-glucopyranoside was prepared. In a similar reaction with 2,3-di- O-benzyl-4,6-di- O-mesyl-α- d-galactopyranosyl 2,3-di- O-benzyl-4,6- O-benzylidene-α- d-glucopyranoside, two products were formed, as indicated by the 19F-n.m.r. spectrum of the reaction mixture, and tentatively identified as the required 4,6-difluoride and the 6-fluoro-4-ene. Fluoride displacement of the mesyloxy group of 2,3-di- O-benzyl-4- O-mesyl-6- O-trityl-α- d-glucopyranosyl 2,3-di- O-benzyl-4,6- O-benzylidene-α- d-glucopyranoside readily gave the 4-fluoride which, on deprotection, gave 4-deoxy-4-fluoro-α- d-galactopyranosyl α- d-glucopyranoside