Fluorination of protected mannose derivatives using diethylaminosulfur trifluoride

Abstract

3,4,6-Tri-O-benzyl-D-mannose and methyl 3,4,6-tri-O-benzyl-α-D-mannopyranoside were subjected to fluorination by diethylaminosulfur trifluoride and each produced two products. The former suffered fluorination at the anomeric centre to give the α-fluoride and, to a lesser extent, additionally at C-2 to give the 2-fluoro-2-deoxy-β-D-glucopyranosyl fluoride. The methyl mannoside underwent a methyl ether migration reaction to produce a 1:1 mixture of the α- and β-2-O-methyl glucosyl fluorides. A mechanism for this rearrangement is proposed and 1H and 19F nmr data are presented for all products.