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R. Lemberg, p. Clezy and J. Barrett 



and from 1-72 to 2-15 opposite to a ring-ketonyl. Since the rhodofying 

 effect of formyl is even stronger than that of ring-ketonyl (cf. 1 with 9, 

 Table 3), a high R III/IV would be expected for porphyrin a with a vinyl 

 opposite to formyl. The a-hydroxyalkyl group has practically no influence 

 on R III/IV (cf. 2 with 1, Table 3). Porphyrin a carboxylic acid has, indeed 

 R III/IV quite similar to pseudoverdoporphyrin (vinylrhodoporphyrin). 



Table 3. Effect of substituents on r ra/iv 



Porphyrin a cannot therefore have the formyl and alkyvinyl groups in the 

 positions at vicinal pyrroles as Warburg and Gewitz (1953) assumed. Lemberg 

 (1953) postulated that the two rhodofying groups must be on opposite 

 pyrroles and therefore one on a ring bearing the propionic acid side chains. 

 There remained the possibility that the two groups substituted one and the 

 same pyrrole ring, no porphyrins of this type being known. However, this 

 possibility was excluded by later work, particularly of MacDonald (see 

 below). 



By the Schumm resorcinol method, followed by removal of iron, Warburg 

 and Gewitz (1953) obtained from haemin a a crystalline porphyrin ester 

 which they called cytodeuteroporphyrin ester. It differed from deutero- 

 porphyrin ester obtained from protohaemin in its melting point. It has also 

 absorption bands slightly more towards the blue than those of deutero- 

 porphyrin ester (Barrett, unpubHshed). Chromic acid oxidation yielded 

 methylmaleimide and haematinic acid. A formula having two free /5-positions 

 in 2 and 3 was suggested, but bromination revealed the presence of three, 

 not two free ^-positions. Recently Marks, Dougall, Bullock and Mac- 

 Donald (1959) have succeeded in synthesizing cytodeuteroporphyrin. The 

 three free /^-positions are in 2, 4 and 8 (Fig. 2). 



