Unsaturated carbohydrates. Part 31. Trichothecene-related and other branched C-pyranoside compounds

Abstract

The C-glycosidic alkene 21, on treatment with tributyltin hydride and a radical initiator, underwent intramolecular radical cyclisation to give the 2-oxabicyclo[3.2.1]octane derivative 23 which is structurally related to the sesquiterpenoid trichothecenes. The unsaturated acetals 27 and 29, formed using methods encountered in the first part of the work, permitted branch-point substituents to be introduced regio- and stereo-specifically at C-3 and at C-4 (carbohydrate numbering) of compounds of this type. Methods are thus available for the synthesis of pyranoid derivatives bearing several C-substituents.