Asymmetric synthesis of a tetracyclic model for the aziridinomitosenes

The conversion of (−)-2,3-O-isopropylidene-d-erythronolactone (9) into the N-phosphorylated aziridine 20, a model for the fundamental structure of aziridinomitosenes, has been accomplished in 11 steps by way of the vinylogous urethane 13. Key steps include the preparation of 13 by a Reformatsky reaction on a thiolactam precursor, Heck cyclisation of 13 to form the indole ring, and aziridine synthesis via a cyclic sulfite.