Enantioselective synthesis of (+)-(1R,2S)-allocoronamic acid

Article abstract of DOI:10.1016/S0040-4039(00)61159-0

The asymmetric synthesis of (+)-(1R,2S)-allocoronamic acid is reported. Diazomethane addition to (Z)-N-(tert-butoxycarbonyl)ethyldehydroalanyl-L-prolin-anhydride, easily prepared from (Z)-2-phenyl-4-propylidene-5(4H)-oxazolone and L-proline, gave in high diastereomeric excess the corresponding spiropyrazoline, which was transformed on photolysis and acid hydrolysis of the resulting spirocyclopropane, into (+)-(1R,2S)-1-amino-2-ethyl-cyclopropanecarboxylic acid.