Stereoselective synthesis of thymine polyoxin C using an allylic trifluoroacetimidate-trifluoroacetamide rearrangement

A stereoselective synthesis of thymine polyoxin C 3 is described in which t he key step is the [3,3] sigmatropic rearrangement of the trifluoroacetimid ate 12 to the trifluoroacetamide 13. Exchange of the protecting groups foll owed by ozonolysis and further oxidation then gave the methyl ester 20 whic h was converted into thymine polyoxin C 3 by introduction of the pyrimidine followed by final deprotection.