Photochemical synthesis of [1,4]-benzodiazepines and pyrrolo-[1,4]-benzodiazepines

Coupling of anthranilic acid with phthalic anhydride and a series of alpha -amino acids gave photoactive substrates which were cyclized by irradiation in water/acetone mixtures (1:1) in the presence of potassium carbonate. The photodecarboxylation and subsequent radical combination resulted in [1,4]-benzodiazepines und pyrrolo-[1,4]-benzodiazepines in moderate yields and high diastereoselectivities. For enantiomerically pure starting materials it was shown that the cyclization step occures with high enantioselectivity.