Dynamic Kinetic Resolution of Ethyl 1,2,3,4-Tetrahydro-[beta]-carboline-1-carboxylate: Use of Different Hydrolases for Stereocomplementary Processes

Both enantiomers of 1,2,3,4-tetrahydro-[beta]-carboline-1-carboxylic acid have been prepared by dynamic kinetic resolution of the corresponding ethyl ester (±)-1. CAL-B-catalysed hydrolysis of (±)-1·HCl in NH4OAc buffer (pH 8.0, 30 °C) provided amino acid (R)-2·HCl with 98% ee and 90% yield in 20 min. The hydrolysis with Alcalase in borate buffer (pH 8.0, 30 °C) showed S selectivity and the product (S)-2·HCl was obtained with 60% ee and 66% yield in 45 h. The absolute configuration of (S)-2 was determined by TDDFT electronic circular dichroism and optical rotation calculations.