Short, enantioselective, gram-scale synthesis of (-)-zephyranthine.

A reasonable synthesis design by strategically integrating functional group manipulation into the ring system construction resulted in a short, enantioselective, gram-scale total synthesis of (-)-zephyranthine. The concise route includes a catalytic Michael/Michael cascade for the asymmetric synthesis of a penta-substituted cyclohexane with three contiguous stereogenic centers, a remarkable 8-step one-pot operation to easily assemble the zephyranthine tetracyclic skeleton, the regioselective construction of a double bond in the C ring and an asymmetric dihydroxylation. This synthesis is also flexible and paves a potential path to a variety of cyclohexylamine-fused tricyclic or polycyclic alkaloids.

Highly regioselective ring-opening of epoxides with amines: a metal- and solvent-free protocol for the synthesis of β-amino alcohols.

We herein report a metal- and solvent-free acetic acid-mediated ring-opening reaction of epoxides with amines. This process provides β-amino alcohols in high yields with excellent regioselectivity. Importantly, this epoxide ring-opening protocol can be used for the introduction of amines in natural products during late-stage transformations.