Employment of 2-oxo-3-(triphenylphosphoranylidene) tetrahydrofuran (7) gave a nucleoside lactone (8) which was converted in several steps to a C-6'carboxylic acid (1Oc). A Curtius rearrangement of this acid, quenching with benzyl alcohol, allowed the introduction of a C- 6'amino group, blocked as a urethane (lla). The chain-ending (C-8') alcohol was converted to a leaving group and displaced by azide ion and dibenzyl sodiomalonate.
