Synthesis of 13a-methylphenanthroindolizidines using radical cascade cyclization: synthetic studies toward (±)-hypoestestatin 1

Abstract

A radical cascade involving 6- endo cyclization of aryl radicals generated from N-acryloyl- N-(1-methylethenyl)-9-bromophenanthren-10-ylmethylamines, followed by 5- endo- trig cyclization of the resulting α-amidoyl radicals afforded phenanthroindolizidines bearing a methyl substituent at the angular C13a position. 2,3,6-Trimethoxy derivative was synthesized by using this method, but its spectral data were not in accord with those of literature values reported for hypoestestatin 1. Further synthetic study toward hypoestestatin 1 is demonstrated.