Enhanced Performance of Thermomyces lanuginosus Lipase-Catalyzed Regioselective Acylation of 6-Azauridine by a Co-Solvent Approach

A comparative study was made of lipozyme TL IM-catalyzed regioselective acylation of 6-azauridine with vinyl palmitate for the preparation of the 5'-O-monoester in co-solvent mixtures and pure polar solvents. Among the solvent systems investigated, a co-solvent mixture of anhydrous acetone/isooctane was found to be the best reaction medium, in which Lipozyme TL IM also exhibited good thermal and operational stability. It was also found that the acylation was dependent on the hydrophobic solvent content. The most suitable co-solvent was anhydrous acetone/isooctane (90:10, v/v). Under the optimal conditions, the initial rate, substrate conversion and 5'-regioselectivity were 20.6 mM/h, 99.0% and 99%, respectively.