The synthesis of 4-oxo-9-deoxy-9-azaprostaglandin I2 (23 a) and two ω-chain analogues thereof (23 c and 23 e) is described. The most salient features of the synthetic process used were (a) introduction of the nitrogen functionality at C-9 by [3, 3] sigmatropic rearrangement of the trichloroacetamidate 5 b to the trichloroacetamide 6,(b) transformation of 6 into the bicyclic lactam 7 with sodium borohydride,(c) stereospecific introduction of the 11α- ...