Direct regioselective enzymatic acylation of nucleosides: building-blocks for the solution phase synthesis of oligonucleotides.

The synthesis of 3'- and 5'-O-levulinyl nucleosidic monomers through enzymatic acylation with acetonoxime levulinate is demonstrated. The acylation process takes place in one-step and use of expensive reagents, such as DMTrCl is avoided. The regioselectivity of the procedure makes it very convenient for acylated monomers required for solution phase synthesis of oligonucleotides.