On the Reaction of Tryptophan Derivatives with N-Phenylselenyl Phthalimide:  The Nature of the Kinetic and Thermodynamic Hexahydropyrrolo[2,3-b]indole Products. Alkylation of Tryptophan with Inversion of Configuration

The cyclization of a range of tryptophan derivatives with N-phenylselenyl phthalimide leading to 3a-phenylselenyl-1,2,3,3a,8,8a-hexahydro[2,3-b]pyrroloindoles has been studied. It is established that in each case the kinetic diastereomer has the C-2 substituent on the exo face of the diazabicyclo[3.3.0]octane skeleton, whereas the thermodynamic isomers have the C-2 substituent endo. A simple protocol for the alkylation of tryptophan, leading to α-substituted tryptophans with clean inversion of configuration, is presented.