A Chemoenzymatic Synthesis of Optically Active Aza Analogues of Quercus Lactones

The synthesis of optically active 4-methyl-5-n-butyl- and 5-n-pentylpyrrolidin-2-ones, aza analogues of the corresponding Quercus lactones, has been achieved by a chemoenzymatic procedure, involving in the enantiodifferentiating step the enzymatic kinetic resolution of the corresponding gamma-ketoester precursors, followed by reductive amination and subsequent cyclization of the enantiomerically pure hydrolysis products. The effect of the reaction conditions as well as the influence of the structure of the substrates on the enzymatic hydrolyses were also studied.