Enzymatic alcoholysis of 3′,5′-di-O-acetyl-2′-deoxynucleosides

Candida antarctica-B (CAL-B) lipase-catalysed alcoholysis of a set of 3′,5′-di-O-acetyl-2′-deoxynucleosides (1a–e) gave the corresponding 3′-O-acetyl-2′-deoxy-nucleosides (2a–e) in yields ranging from 50 to 96%. The alcohol employed in the biotransformation affected the rate of the enzymatic reaction and the yield of the 3′-O-acetylated product, but in all cases only this regioisomer was formed. The obtained results are in agreement with the regioselectivity displayed by CAL-B lipase in previously reported biotransformations of nucleosides. CAL-B catalysed alcoholysis of 2′,3′,5′-tri-O-acetyl-cytidine and 4-N-acetyl-2′,3′,5′-tri-O-acetylcytidine was also studied, affording with the same regioselectivity the corresponding free 5′-hydroxyl nucleosides.