“…Numerous porphyrins were isolated, and their constitution determined, which cannot be discussed in more detail in a short lecture. The most important among them is pheoporphyrin (11,15) (XIII) which is obtainable from the pheophorbides, also from pheophytin and chlorophyl- culty. Pheoporphyrin a3 reacts with ketone reagents and can be split by hydrolysis to chloroporphyrin e«, which is likewise a monomethyl ester and possesses the following formula (XIV):…”