Efficient synthesis of Guanfu base G via highly regioselective lipase-catalyzed acylation in non-aqueous phase.

Lipase-catalyzed acylation of Guanfu alcohol-amine (GFAA) with vinyl acetate (VA) was performed in non-aqueous system for the preparation of Guanfu base G (GFG), a plant-originated alkaloid with significant antiarrhythmic activity. Among the eight lipases from different origins, Novozym 435 was found to be the best biocatalyst. The most suitable molecular sieve amount, substrate concentration, molar ratio of VA to GFAA, enzyme amount and reaction temperature were proved to be 40 mg/mL, 6 μmol/mL, 10:1, 2mg/mL and 50 °C, respectively. A maximum GFG yield of 37.4% was achieved under the selected conditions with methanol served as the optimal reaction medium. The structure of the acetylated product was elucidated by (1)H NMR and (13)C NMR analysis.