Candida antarctica lipase B catalysed kinetic resolution of 1,2,3,4-tetrahydro-ß-carbolines: Substrate specificity

Abstract

In the frame of substrate specificity, CAL-B-catalysed asymmetric N-alkoxycarbonylations of 1-substituted tetrahydro-ß-carbolines (Me, Et, Pr, iPr) have been studied. High enantioselectivities (>200) were observed, when alkoxycarbonylation of racemic compounds (±)-1,3,5,7 were performed in DIPE in the presence of phenyl allyl carbonate and Et3N at 60 °C using ultrasound shaking method. The reaction time increased considerably with increasing substituent size on C1; however, the isopropyl-substituted compound proved to be too bulky for the optimum activity of CAL-B. The (R)-carbamate enantiomers were hydrolysed using Pd2(dba)3.CHCl3 and the enantiomers of the free amines were obtained with excellent ee (>99%).