Enhancing the activity and regioselectivity of lipases for 3′-benzoylation of floxuridine and its analogs by using ionic liquid-containing systems

Ionic liquid-containing systems offered new opportunities to enzymatic acylation of nucleosides. In Pseudomonas cepacia lipase-mediated benzoylation of floxuridine (FUdR), the enzyme performances, including enzyme activity and 3′-regioselectivity, were significantly enhanced by using [C4MIm]PF6-containing systems. It was observed that the enzyme performances not only depended on the anion of IL, but also on the cation, and that a proper combination between the cation and anion was critical to allow the enzyme to exhibit excellent performances. The optimal IL content in IL-containing systems is 5% (v/v). To gain a deeper insight into enzyme recognition, we extended benzoylation of FUdR catalyzed by P. cepacia lipase to its analogs. FUdR and its analogs could be biotransformed to the desired product by P. cepacia lipase in excellent conversion (>99%) and good to excellent 3′-regioselectivity (81–99%). Furthermore, the 3′-regioselectivity of P. cepacia lipase was enhanced with the increase of hydrophobicity of 5-substituent of the substrates, due to better hydrophobic interactions with Leu287 present in the active site.