Enantioselective synthesis of (+)-trypargine and (+)-crispine E

Asymmetric transfer hydrogenation was used as a key step in the synthesis of two guanidine-derived alkaloids (+)-trypargine and (+)-crispine E. The enantiomeric compositions of key intermediates were established on the basis of 1H NMR spectra with chiral solvating agents. The absolute stereochemistry was proven by X-ray crystallography.