A new and efficient synthesis of the pyrrolo [2, 1-c][1, 4] benzodiazepine ring system has been carried out using, as a key step, an intramolecular aza Wittig reaction of the appropriately substituted N-(2-azidobenzoyl) pyrrolidine-2-carboxaldehydes. The parent unsubstituted PBD 4 and the natural product DC-81 have been prepared in the imine form in good overall yields.
