Ready Preparation of Furanosyl n-Pentenyi Orthoesters from Corresponding Methyl Furanosides

The 3,5-di-O-benzoyl n-pentenyl orthoesters of the four pentofuranoses have been prepared. The first key intermediate in each case is the methyl pentofuranoside(s), and a user-friendly procedure for the pre.Daration of each, based on the Callam Lowary precedent, is described, whereby formation of the crucial alpha/beta anomeric mixture is optimized. The mixture is used directly to prepare the corresponding perbenzoylated pentofuranosyl bromide(s) and then the title compounds.