Starting from methyl pheophorbide-a, 3-formyl substituted compound was synthesized through oxidation of its vinyl at 3-position. The Wittig reaction of the formyl group at 3-position was carried out to yield the corresponding methyl 3-(2-substituted ethenyl)pheophorbide-a. In basic conditon, E-ring was converted into the six membered cyclic anhydride to form N-substituted imide ring. The title compound has both hydrophilic and hydrophobic regions to demonstrate a considerable bathochromic shift of the major absorp-tion band in the red region of the optical spectrum. The derivatives of purpurin-18 imide were potentially ideal photosensitizers. The structures of all new compounds were characterized by elemental analysis, UV, IR, and ¹H NMR spectra.

Key words: photosensitizer, photodynamic therapy, purpurin-18 imide, methyl pheophorbide-a