20.23
[]. Caroline Roche, et al. New asymmetric approach to natural pyrrolizidines: synthesis of (+)-amphorogynine A, (+)-amphorogynine D, and (+)-retronecine. J Org Chem. 2005 Oct ;70(2):8352-63.
P26-P26-P270-P27-P280-P302+P352-P30+P30-P305+P35+P338-P330-P362+P36-P03+P233-P05-P50