Novel domino cyclization of tryptophan-derived amino nitriles: Scope and stereoselectivity

The scope and stereoselectivity of the acid-promoted cyclization of new tryptophan-based alpha-amino nitriles derived from either ketones or aldehydes to novel hexahydropyrrolo[1',2',3':1,9a,9]imidazo-[1,2-a]indoles is described. The time and stereoselectivity of the reaction mostly depended on both the steric volume of the substituents at the amino nitrile and its stereochemistry.