De Martino G, Massa S, Giuliano R
Farmaco Sci. 1976 Nov;31(11):785-90.
The synthesis of 5,11-dioxo-1,2,3,10,11,11a-hexahydro-5H-pyrrolo (2,1-c) (1,4)benzodiazepine and 2-bromo-5,11-dioxo-1,10,11,11a-tetrahydro-5H-pyrrolo (2,1-c) (1,4)benzodiazepin-11a-ethylcarboxylate, structurally related to anthramycin and tomaymycin, was achieved by forming in situ the pyrrolidine nucleus instead of using proline or its derivatives. The most important intermediate was 1-(2-nitrobenzoyl)-delta4-pyrrolin-2,2-dicarboxylate which was then easily transformed into the above-mentioned tricyclic systems, starting with catalytic reduction or bromination.