Kinetic and Thermodynamic Investigation of Lipase-Catalyzed Hydrolysis of (<i>R</i>,<i>S</i>)-3-Phenylbutyl Azolides

Water-saturated cyclohexane at 25 °C is selected as the best reaction condition for Novozym 435-catalyzed hydrolytic resolution of (<i>R</i>,<i>S</i>)-3-phenylbutyl 4-methylpyazolide (<b>1</b>). The kinetic constants and enantiomeric ratio of 36 are then estimated from the kinetic analysis and successfully employed for simulating the time-course conversions of both enantiomers. A feed-batch operation with water added during the reaction is proposed for converting the fast-reacting enantiomer of high concentrations to the product. A linear enthalpy–entropy compensation relationship of −ΔΔ<i>S</i> = −38.84 + 3.29­(−ΔΔ<i>H</i>) with <i>R</i><sup>2</sup> = 0.98 for the lipase-catalyzed hydrolysis or alcoholysis of several (<i>R</i>,<i>S</i>)-azolides in anhydrous or water-saturated solvents is addressed. The resolution platform is further extended to (<i>R</i>,<i>S</i>)-3-(Boc-amino)-3-phenylpropionyl 4-methylpyrazolide (<b>10</b>), leading to improved enzyme activity and enantioselectivity if anhydrous methyl <i>tert</i>-butyl ether or isopropanyl ether is selected as the reaction medium.