Synonyms: Purpurin 18;21H,23H-Porphine-2,20-dicarboxylic acid,18-(2-carboxyethyl)-12-ethenyl-7-ethyl-17,18-dihydro-3,8,13,17-tetramethyl-,cyclic 2,20-anhydride, (17S-trans)-;Purpurin a;(17S-trans)-18-(2-Carboxyethyl)-12-ethenyl-7-ethyl-17,18-dihydro-3,8,13,17-tetramethyl-21H,23H-porphine-2,20-dicarboxylic acid cyclic 2,20-anhydride;(17S,18S)-18-(2-Carboxyethyl)-12-vinyl-7-ethyl-17,18-dihydro-3,8,13,17-tetramethyl-21H,23H-porphyrin-2,20-dicarboxylic acid 2,20-anhydride;3,8,13,17β-Tetramethyl-7-ethyl-12-ethenyl-18α-(2-carboxyethyl)-17,18-dihydro-21H,23H-porphyrin-2,20-dicarboxylic acid 2,20-anhydride;PP-18;