Decarboxylation of uroporphyrin by heating at atmospheric pressure

Free uroporphyrin is decarboxylated by heating in the air to 150--200 degrees C. Complete decarboxylation occurs after heating to 200 degrees C for 5 min, with a yield of 66--75%. Heptacarboxylic porphyrin can be prepared with a yield of 40% by heating uroporphyrin to 150 degrees C for 60 min, and hexacarboxylic porphyrin with a yield of about 20% by heating to 150 degrees C for 2h.