GENERAL PREPARATIVE SYNTHESIS OF 2'-O-METHYLPYRIMIDINE RIBONUCLEOSIDES

A convergent and general approach to synthesizing 2'-O-methylpyrimidin e ribonucleosides 4a-e, 6, 7 on a multigram scale is described which b egins with an improved procedure for making larger quantities of 2-O-m ethyl-1,3,5-tri-O-benzoyl-alpha-D-ribose. The sugar was reacted with t he desired silylated pyrimidines at room temperature under Vorbruggen conditions. The crude products contained less than 10% of the alpha an omers and the desired beta anomers were isolated by crystallization. T he blocked nucleosides were then deprotected and isolated by standard methods.