The levulinyl-protected nucleosides are key building blocks for the solution-phase synthesis of oligonucleotides. Short and efficient syntheses of 3'- and 5'-O-levulinylated 2'-deoxyribonucleosides and 2'-O-methylribonucleosides have been developed from the corresponding nucleosides by enzyme-catalyzed regioselective acylation in organic solvents or from 3',5'-di-O-levulinyl derivatives by regioselective enzymatic hydrolysis. Lipase-mediated levulinylation of various nucleosides has been accomplished with acetonoxime levulinate as an acyl donor. Use of immobilized Pseudomonas cepacia lipase (PSL-C) has furnished 3'-O-levulinylated 2'-deoxyribonucleosides in excellent yields. Similarly, Candida antarctica lipase B (CAL-B) has provided 5'-O-levulinylated nucleosides in high yields. 3'-O-Levulinylated 2'-deoxyribonucleosides and 2'-O-methylribonucleosides were prepared via selective hydrolysis of 3',5'-di-O-levulinate esters using CAL-B.