An efficient preparation of protected ribonucleosides for phosphoramidite RNA synthesis

An efficient synthesis of protected ribonucleosides useful for phosphoramidite RNA synthesis is described. Di-t-butylsilylene group was employed for simultaneous protection of 3′- and 5′-hydroxyl functions of nucleoside. Subsequent silylation of free 2′-OH group followed by introduction of suitable protection on the base moiety, removal of cyclic silyl protection and tritylation of 5′-OH gave target compounds in 60–66% overall yield.