Nucleosides. 132. Synthesis of 5-(2'-substituted-2'-deoxy-.beta.-D-arabinofuranosyl)-1-methyluracils from 1-methyl-.psi.-uridine. The first direct introduction of the 2'-substituent to C-2' in the "up" configuration by nucleophilic reactions. Studies directed toward the synthesis of 2'-deoxy-2'-subs