46 David Shemin and Jonathan Wittenberg 



A and B, and haematinic acid from Rings C and D. The 

 methylethylmaleimide represents fourteen carbon atoms of 

 the porphyrin, since it arises from both Rings A and B, and 

 the haematinic acid represents sixteen carbon atoms since it 

 arises from both Rings C and D, a total of thirty of the 

 original thirty-four carbon atoms. The remaining four 

 carbon atoms were the original four methene bridge carbon 

 atoms which, in this procedure, are oxidized to carbon dioxide. 

 Since side reactions may have taken place during the oxida- 

 tive cleavage, contaminating the carbon dioxide from the 

 methene bridge carbon atoms, the evolved carbon dioxide 

 was not collected. Nevertheless, as will be seen below, the 

 source of the methene bridge carbon atoms can be determined 

 by simple calculations. 



The haematinic acid was decarboxylated to methylethyl- 

 maleimide and carbon dioxide. This carbon dioxide repre- 

 sented carbon atoms ClO, DlO, i.e. the carboxyl groups of 

 the porphyrin. Both methylethylmaleimide samples were 

 then converted separately with osmium tetroxide to tartari- 

 mide derivatives, and the latter cleaved with periodic acid to 

 yield pyruvic acid and a-ketobutyric acid. The pyruvic acid 

 samples in each case represent the methyl side of the pyrrole 

 rings, i.e. carbon atoms A6, B6; A4, B4; A5, B5 from Rings 

 A and B and carbon atoms C6, D6; C4, D4; C5, Do from Rings 

 C and D. The a-ketobutyric acid samples represent the vinyl 

 side of pyrrole rings A and B and the propionic acid side, 

 minus the carboxyl groups, of pyrrole rings C and D; i.e. 

 carbon atoms A9, B9; A8, B8; A3, B3; A2, B2; from Rings 

 A and B, and carbon atoms C9, D9; C8, D8; C3, D3; C2, D2 

 from Rings C and D. The keto acids from each maleimide 

 sample were separated on a silica gel column and converted 

 to their respective 2:4-dinitrophenylhydrazones. The hydra- 

 zones were oxidatively decarboxylated to yield acetic acid 

 and carbon dioxide, and propionic acid and carbon dioxide, 

 from the pyruvic and ketobutyric acid hydrazones respective- 

 ly. The carbon dioxide samples from the pyruvic acid 

 hydrazone represented carbon atoms A5, B5 and C5, D5 while 



