Towards the Synthesis of Dihydrooxepino[4,3‑b]pyrrole-Containing Natural Products via Cope Rearrangement of Vinyl Pyrrole Epoxides

An approach to the dihydrooxepino­[4,3-b]­pyrrole core of diketopiperazine natural products which utilizes a vinyl pyrrole epoxide Cope rearrangement was investigated. It was found that an ester substituent on the epoxide was essential for the [3,3]-rearrangement to occur. Density functional calculations with M06-2X provided explanations for the effects of the pyrrole and ester groups on these rearrangements.