A simple and straightforward assembly of the yohimban skeleton was achieved by condensation of an acyclic β-keto ester with tryptamine, followed by consecutive cross metathesis and tandem cyclization reactions, leading to the formation of three new rings. The whole process was readily carried out in the one-flask providing a rapid entry to the pentacyclic scaffold of yohimbine alkaloids.
Key words
tandem cyclization - yohimbine alkaloids - intramolecular Michael reaction - organocatalysis - one-pot synthesis