Radical [3 + 2]-annulation of divinylcyclopropanes: rapid synthesis of complex meloscine analogs.

A radical [3 + 2]-divinylcyclopropane annulation cascade has been extended to encompass five D-ring variants of the meloscine/epimeloscine core structure. Representative ABCD tetracyclic intermediates were further elaborated with novel substituted E-rings through subsequent transformations of advanced intermediates that provided opportunities for late-stage variation of the B-ring (lactam) N-substituents which were also developed.