Novozym 435-catalyzed regioselective benzoylation of 1-β-d-arabinofuranosylcytosine in a co-solvent mixture of C4MIm·PF6 and pyridine

Author： Tan Zi-Yang Wu Hong Zong Min-Hua

Publisher： Informa Healthcare

ISSN： 1024-2422

Source： Biocatalysis and Biotransformation, Vol.25, Iss.5, 2007-09, pp. : 408-413

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Abstract

Regioselective acylation of 1-β-d-arabinofuranosylcytosine (ara-C), using vinyl benzoate (VB) as acyl donor and Novozym 435 as catalyst, was carried out in various reaction media including pure organic solvents, organic solvent mixtures, and ionic liquid (IL)-containing systems. Although the reaction was highly regioselective in all the media assayed, remarkable enhancement of substrate conversion was achieved with a co-solvent mixture of 1-butyl-3-methylimidazolium hexafluorophosphate (C4MIm·PF6) and pyridine as the reaction medium, compared with other media tested. Additionally, the results demonstrated that the anions of ILs had a significant effect on the initial rate and substrate conversion. To better understand the reaction performed in IL-containing system, several variables were examined. The optimum molar ratio of VB to ara-C, initial water activity, temperature and shaking rate were 25:1, 0.11, 40°C and 250rpm, respectively. Under these optimum reaction conditions, the initial rate, substrate conversion, and regioselectivity were 0.49mMmin-1, 99.4 and 99%, respectively. The product of the lipase-catalyzed reaction was characterized by 13C NMR and was shown to be 5'-O-benzoyl ara-C.