Long wavelength photosensitizers related to chlorins and bacteriochlorins for use in photodynamic therapy

A series of long wavelength photosensitizers related to chlorins and bacteriochlorins has been synthesized from the Diels-Alder reaction of protoporphyrin III dimethyl ester 6, or protoporphyrin II dimethyl ester 29. These porphyrins were prepared either by copper(II)-promoted cyclization of the corresponding a,c-biladienes or by following the modified MacDonald dipyrromethane approach. To eliminate the possibility of isomer formation in synthesis of so-called \u27benzoporphyrin derivatives\u27 and also to understand structure-activity relationships among various photosensitizers, Diels-Alder reactions were also performed on 13,17-bis(2-methoxycarbonylethyl)-2,3,8,12,18- pentamethyl-7-vinylporphyrin 21 and 3-(1-hydroxyethyl)-13,17-bis(2- methoxycarbonylethyl)-2,7,12,18-tetramethyl-8-vinylporphyrin 22