Concise syntheses of (±)-protoemetinol and related alkaloids using radical cyclisation

Abstract

Both (±)-protoemetinol, its 3- epi-isomer and (±)-3-desmethyl protoemetinol have been prepared in five linear steps from a dihydroisoquinoline using a 6- exo- trig cyclisation of a vinyl radical in the key step. This novel and particularly short route has potential application in the synthesis of Alangium and Mitragyna alkaloids.