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

Abstract

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 ‘benzoporphyrin derivatives’ 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-tetra-methyl-8-vinylporphyrin 22.