Naturally-derived metallo-bacteriochlorophylls have attracted much attention since their clinical approval for cancer photodynamic treatment. Their therapeutic properties are rooted in the metal complexation of bacteriochlorophylls, which endows them with optical properties favourable for biophotonic and biomedical applications, including increased therapeutic reactive oxygen species (ROS) yield. Despite these advantages, the utility of these chromophores has been limited by synthetic challenges associated with bacteriochlorophyll metalation; specifically, a slow reaction rate and necessity of complex purification procedures. Herein, we overcome these limitations through the development of a new fast, facile, efficient, base-free microwave irradiation metalation method for the synthesis of a series of metallo (Pd, Cu, Zn, Cd, Sn, In, Mn, Co) bacteriopyropheophorbides. We present the preparation, structural and optical spectral characterization of these complexes. We then apply this microwave-enabled synthetic method to generate the clinical photosensitizer agent Pd-bacteriopheophorbide (TOOKAD) effectively and efficiently, and validate its metalation-enhanced ROS generation potency.

Fast, facile, base free microwave-assisted metalation of bacteriochlorophylls and corresponding high yield synthesis of TOOKAD

ACS Fall 2021

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