Cycloaddition reaction on 3-vinylemeraldins: Formation of unexpected porphyrins with seven-membered exocyclic ring systems

Reaction of 3-vinylemeraldin with dimethyl acetylenedicarboxylate (DMAD) produced a benzoporphyrin derivative via [4+2] Diels-Alder adduct and an unexpected porphyrin containing a seven-membered ring system (yield 15%) fused at the 3- and 5-positions of the macrocycle. The benzoporphyrin derivatives containing N-alkylated fused imide ring system exhibit long wavelength absorptions near λ(max) 725 nm. In preliminary in vivo screening some of these analogs were found to be more effective than the related protoporphyrin IX (PP-IX) based benzoporphyrin derivative (BPDMA).