Organofluorine compounds and fluorinating agents part 21: perfluoroalkylidene sugars by non-classical acetalation of pyranoses

Abstract

Acetalations of methyl α- d-mannopyranoside ( 1), methyl 6- O-trityl-α- d-mannopyranoside ( 5), benzyl α- d-mannopyranoside ( 14), and methyl β- d-galactopyranoside ( 17) with perfluoroaldehydes (C 4F 9CH=O, C 6F 13CH=O, and C 8F 17CH=O) in the presence of dicyclohexylcarbodiimide (DCC) lead, under epimerization at the C-atom 3 of the corresponding pyranose moiety, to perfluoroalkylidene derivatives of α- d-altrosides ( 2–4, 6/7, 15) and of β- d-gulosides ( 18–20), respectively. After partial deprotection of 3 (or 15) and 18–20, respectively, the liquid crystalline, amphiphilic 3,4- O-perfluorohexylidene- d-altropyranoside ( 13) and 2,3- O-perfiuoroalkylidene- d-gulopyranosides 24–26 were obtained.