Efficiently enhancing regioselective acylation of 5‐azacytidine catalysed by Candida antarctica lipase B with co‐solvent mixtures as the reaction media

• Published in: Biotechnology and Applied Biochemistry
• Main Authors: Wu, Hong, Zong, Minhua, Chen, Xiyu
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2009
• Subjects: Antarc*; Antarctica
• Online Access: http://dx.doi.org/10.1042/ba20080178; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1042%2FBA20080178; https://iubmb.onlinelibrary.wiley.com/doi/pdf/10.1042/BA20080178

A comparative study of regioselective acylation of 5‐azacytidine catalysed by CAL‐B ( Candida antarctica lipase B) in co‐solvent mixtures and in pure organic solvents was performed, to our knowledge for the first time, and it was shown that a remarkable enhancement in the initial rate and substrate conversion in the reaction could be achieved with co‐solvents as the reaction medium instead of pure organic solvents. For the CAL‐B‐catalysed regioselective synthesis of 5′‐ O ‐butyryl‐5‐azacytidine in co‐solvent mixtures, the optimal conditions were as follows: optimal co‐solvent mixture, hexane/pyridine (40/60, v/v); initial a w (water activity), 0.07; enzyme dosage, 50 units/ml; vinyl butyrate/5‐azacytidine molar ratio, 15:1; temperature, 60 °C. Under the optimal conditions, v 0 (the initial reaction rate), C (the substrate conversion) and the regioselectivity of the reaction were 0.75 mM/min, 99.0% and above 99% respectively. Similar phenomena were observed in the CAL‐B‐catalysed regioselective acylation of 5‐azacytidine with an extensive range of fatty acid vinyl esters (from C2 to C18). Compared with pure pyridine, the reactions were greatly accelerated in a hexane/pyridine (40/60, v/v) co‐solvent mixture and 5‐azacytidine could be biotransformed into its derivative 5′‐ O ‐acyl‐5‐azacytidine at a much higher conversion rate (91.4–99.0% as against 40.2–43.5%). Meanwhile, adoption of a co‐solvent mixture as the reaction medium could also greatly lower the enzyme dosage and the molar ratio of acyl donor to 5‐azacytidine.