The Structure of Porphyrin a, Cryptoporphyrin a and Chlorin a^ 357 



ADDENDUM 

 Piattelli in the laboratory of Nicolaus has recently obtained a 2 : 5-pyrrole 

 dicarboxylic acid with propionic and nitrile side chains in the /5-positions by 

 permanaganate oxidation of porphyrin a nitrile (private information). This 

 estabhshes the formyl group in position 8 on ring IV (formula II of Fig. 3). 

 Porphyrin a is thus 1:3: 5-trimethyl-2-a-hydroxyalkyl-4-/3-alkylvinyl-8- 

 formyl-6 : 7-di(/^-carboxyethyl)-porphyrin. No ethyl-methyl-2 : 5-pyrrole-dicar- 

 boxylic acid could be discovered among the oxidation products of hydro- 

 genated porphyrin a. This lends further support to the vinyl group of 

 porphyrin a in position 4 carrying an alkyl substituent. Piattelli and Nicolaus 

 {R.C. Accad., Napoli, Ser. 4a, 26, p. 44, 1959) have now obtained the 2:5- 

 pyrrole-dicarboxylic acid with methyl and carboxylic acid groups in the 

 /^-positions; the carboxyl is here derived by oxidation of the unsaturated side 

 chain in 4 and probably also the a-hydroxyalkyl side chain in 2 of porphyrin 

 a (cf. also R. A. Nicolaus, Rassegna di Medicina sperimentale, 7, suppl. 2 

 (I960)). 



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