Synthesis of 6-O-unsaturated acyl L-ascorbates by immobilized lipase in acetone in the presence of molecular sieve

6-O-Unsaturated acyl L-ascorbates were synthesized through immobilized-lipase-catalyzed condensation of ascorbic acid and various unsaturated fatty acids. The equilibrium conversion was higher at a higher molar ratio of a fatty acid to ascorbic acid for the synthesis of every acyl L-ascorbate in the absence of a molecular sieve. For the synthesis of oleoyl L-ascorbate, the addition of molecular sieve 4 Angstrom into the reaction system increased both the initial reaction rate and the conversion. However, the conversion gradually decreased on prolonged reaction time. When an excess amount of molecular sieve was added into the system, the conversion was lowered. Furthermore, the molecular sieve adsorbed and degraded the oleoyl ascorbate, and these rate processes were also analyzed. (C) 2003 Elsevier Science B.V.. All rights reserved.