2,18-Porphinedipropionic acid, 3,7,12,17-tetramethyl-8,13-divinyl-, dimethyl ester 21H,23H-Porphine-2,18-dipropanoic acid, 7,12-diethenyl-3,8,13,17-tetramethyl-, dimethyl ester 5522-66-7 NSC19666 Protoporphyrin IX dimethyl ester