Here we show the facile synthesis of 132-173-bacteriochlorophyllone a (12), with a distinct seven-membered exocyclic F-ring formed by 132-173-cyclization of bacteriopheophorbide a(16). This is the latest reported bacteriochlorin with such an exocyclic F-ring since 1975 (132-173 cyclobacteriopheophorbide a-enol, 11), and is an analog of previously described natural exocyclic F-ring-containing porphyrins (1–4) and chlorins (5–10). The structure of 12 was confirmed using a combination of 1D 1 H NMR, 2D COSY 1 H NMR, Jmod 13 C NMR and HRMS analysis. The biological activity of 12 was explored, and we found that this compound does not possess strong antioxidant activity like its natural product counterparts, but is a capable photosensitizer for photodynamic therapy.
