Abstract
Novel meso-substituted cationic porphyrins have been synthesized as potential photodynamic agents. 5,10-bis(4-Acetamidophenyl)-15,20-bis(4-methylphenyl)porphyrin 1 was prepared using a modification of the Alder-Longo procedure. However, two different approaches were compared in the synthesis of 5-(4-trifluorophenyl)-10,15,20-tris(4-acetamidophenyl)porphyrin 2. One involved a condensation of binary mixture of aldehydes and pyrrole under equilibrium conditions and the other a binary mixture of aldehydes and meso-(4acetamidophenyl)dipyrromethane 3. The last synthetic pathway was advantageous mainly for an easier reaction work up and a higher yield. Both amido porphyrin 1 and 2 were hydrolyzed in basic media and treated with methyl iodide to form 5,10-di(4-methylphenyl)-15,20-di(4trimethylammonium phenyl)porphyrin iodide 4 and 5-(4-trifluorophenyl)-10,15,20-tris(4trimethyl ammoniumphenyl)porphyrin iodide 5, respectively. Porphyrin 5 bears a highly lipophilic trifluoromethyl group, which increases the amphiphilic character of the structure. On the other hand, the photodynamic properties of porphyrin 5 were changed forming metal complex with Pd(II), porphyrin 6. Absorption and fluorescence spectroscopic studies of these porphyrins were compared in different solvents. These amphiphilic cationic porphyrins are promising photosensitizers with potential applications in bacteria inactivation by photodynamic therapy.
Highlights
Tetrapyrrolic macrocycles occupy a central place in bioorganic chemistry.[1]
Porphyrin 5 bears a highly lipophilic trifluoromethyl group, which increases the amphiphilic character of the structure
This paper reports the synthesis of novel asymmetrically meso-substituted cationic porphyrins with AABB- and AB3-porphyrin symmetry pattern, 5,10-bis(4-methylphenyl)-15,20bis(4-trimethylammoniumphenyl)porphyrin iodide 4 and 5-(4-trifluorophenyl)-10,15,20-tris(4trimethylammoniumphenyl) porphyrin iodide 5
Summary
Tetrapyrrolic macrocycles occupy a central place in bioorganic chemistry.[1]. Meso-substituted porphyrins have recently found specific biomedical applications, in the field of detection and treatment of neoplastic tissues.[2,3] Photodynamic therapy (PDT) consists of the administration of a photosensitizer, which is selectively retained by the neoplastic tissue. 5,10-bis-(4-acetamidophenyl)-15,20bis(4-methylphenyl)porphyrin 1 was prepared from a binary mixture of aldehyde and pyrrole using a modification of the Alder-Longo procedure. These approaches involve the condensation of a binary mixture of aldehyde and, either pyrrole or dipyrromethane derivative, catalyzed by acid. Synthesis 5,10-bis(4-Acetamidophenyl)-15,20-bis(4-methylphenyl)porphyrin 1 was synthesized from a binary mixture of aldehydes and pyrrole using a modification of the Alder-Longo method as showed in Scheme 1.36
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