First enantioselective synthesis of the antitumour alkaloid (+)-crispine A and determination of its enantiomeric purity by 1H NMR

A simple enantioselective synthesis of the pyrrolo[2, 1-a]]isoquinoline alkaloid (+)-crispine A, based on the use of an asymmetric transfer hydrogenation as the key step, is described. The enantiomeric excesses of the obtained alkaloid samples were determined from H-1 NMR spectra recorded in the presence of (+)-(R)-t-butylphenylphosphinothioic acid as a chiral solvating agent. (c) 2005 Elsevier Ltd. All rights reserved.