Enzymatic Ammonolysis Of Ethyl 4-chloro-3-hydroxybutanoate In Organic Solvents

Ethyl 4-chloro-3-hydroxybutanoate (CHBE) is an important chiral building block which is a useful intermediate to alkaloids and statins. It is reported that microbial, enzymes and BINAP- based Ru catalysists can be used to resolute CHBE. We focused on the resolution of CHBE catalyzed by enzymes. The scheme is:Through screening of lipases, we found that Novozym435 showed the highest activity and enantioselectivity toward the ammonolysis of CHBE. The effect of different solvents on the ammonolysis was investigated. And 1, 4-dioxane was found to be the best solvent. Further research was done to study the effects of various parameters. The optimal temperature was 40℃. When the concentration of enzyme is 10mg/ml and the concentration of substrate is 0.5mol/l, 99% (R)-CHBE e.e value and 65.2% CHBE conversion were achieved at 18h. The enantiomeric ratio E in enzymatic kinetic resolutions was often temperature dependent. Through the theory of temperature effects on the E, we got the racemic temperature of this reaction is 352K. The kinetics was found to obey the Ping-Pong bi-bi mechanism and the simulated values correspond to the experimental value quite well.