Simple Synthesis of Racemic Pyrrolo[2,3-b]indoles: Formal Total Synthesis of (±)-Physostigmine

Racemic pyrrolo[2,indoles were efficiently synthesized by the reaction of aromatic hydrazines with 4-chloro-2-methylbutanal.A formal total synthesis of physostigmine was achieved.Physostigmine (1), which is isolated from Physostigma venenosum (Balf.)seeds (Calabar beans), 1 is a highly potent acetylcholinesterase inhibitor.2