Asymmetric synthesis of (R)-antofine and (R)-cryptopleurine via proline-catalyzed sequential α-aminoxylation and Horner-Wadsworth-Emmons olefination of aldehyde.

Naturally occurring phenanthroindolizidine alkaloids (R)-antofine and phenanthroquinolizidine alkaloids (R)-cryptopleurine have been synthesized in high optical purity via proline-catalyzed sequential α-aminoxylation and Horner-Wadsworth-Emmons olefination of aldehyde. Both enantiopure forms of proline are commercially available, and thus, in principle, both isomers of antofine and cryptopleurine can be accessed with the new method.