Nucleosides and Nucleotides. Part 88. A New Method for Synthesizing the Antineoplastic Nucleosides 1-(2-Azido-2-deoxy-β-D-arabinofuranosyl)cytosine (Cytarazid) and 1-(2-Amino-2-deoxy-β-D-arabinofuranosyl)cytosine (Cytaramin) from Urid