Synthesis of 5′-C-branched thymidines and conversion to phosphoramidites

Thymidine was converted to its 5'-epoxy derivative, which was reacted with nucleophiles to give 5'-C-aminomethyl-, 5'-C-bromomethyl-, 5'-C-cyanomethyl, and 5'-C-methoxymethylthymidine derivatives with defined stereochemistry. 5'-C-ally-, 5'-C-hydroxymethyl-, 5'-C-hydroxypropyl-, and 5'-C-(imidazole-4-acetamido)metbylthymidine derivatives were also prepared. The 5'-C-branched thymidines were converted to the corresponding phosphoramidites.