Abstract
The synthesis of the blocked nucleoside 3′,5′-di-O-p-toluoyl-4-O-methyl-5-formyl-methyl-2′- deoxyuridine (19) was accomplishied in eleven steps from gamma-butyrolactone. This aldehyde, which should facilitate the synthesis of nucleosides containing 18 F, was converted to the corresponding blocked dithianyl nucleoside (21), and also to 5-(2,2-difluoroethyl)-substituted derivatives of 2′-deoxyuridine and 2′-deoxycytidine.