Solid phase synthesis of a novel folate-conjugated 5-aminolevulinic acid methyl ester based photosensitizer for selective photodynamic therapy

The development of a novel tumor-targeting photosensitizer delivery system, with potential ability to selectively transport the photosensitizer prodrug 5-aminolevulinic acid methyl ester (MAL) into the tumor site has been herein described. Conjugation of MAL to folic acid (FA) via an unnatural ?-peptide linker has been carried out almost entirely by an efficient solid phase approach. This molecular system has been devised for possible applications in selective photodynamic diagnosis (PDD) and therapy (PDT).