The Structure of Porphyrin a, Cryptoporphyrin a and Chlorin a^ 349 



The two rhodofying groups must therefore occupy the positions 4 and 8 

 on rings II and IV. The structure of cytodeuteroporphyrin with two propionic 

 acid groups disproves the assumption (Lemberg, 1953; Dixon and Webb, 



H, H H^ M 



/2 3\ y/z i\ 



M/T 4\E M.A 4\H 



M\^ VM H\8 5/M 



V ^^ V 6/ 



P P F P 



Fig. 2. Cytodeuteroporphyrin. 



1958) that the excess carbon and hydrogen in porphyrin a (see below) is 

 present in the form of a long fatty acid side chain. 



The oi- Hydroxy alky I Side Chain 



These studies raised the problem of the third substituent removed from 

 position 2 in ring I in the resorcinol melt. As shown above, there was 

 evidence against this being another carbonyl or vinyl side chain. In fact any 

 of these groups in position 2 would have a strong anti-rhodofying effect, not 

 in harmony with the oxorhodotype spectrum of porphyrin a. We have, e.g. 

 recently obtained a porphyrin a derivative having a carbonyl group in this 

 position. This had a rhodotype spectrum with R III/IV 1-21. Of groups 

 known to be removed in the resorcinol melt only a-hydroxyalkyl remained; 

 haematohaemin is known to yield deuterohaemin. The low Ry of porphyrin 

 a ester in chloroform-kerosene (0-10) or propanol-kerosene (0-26) was in 

 agreement with such an assumption (Barrett, 1959) and also the analyses of 

 haemin a (Table IV) which indicated the presence of at least 6 atoms of 

 oxygen. Barrett (1959) has been able to acetylate the hydroxyl groups by 

 acetic anhydride in pyridine with the increase of Rp from OTO to 0-56 and 

 from 0-26 to 0-62 respectively. This hydroxyl group is present in the form of 

 an a-hydroxyalkyl group (Clezy and Barrett, 1959). In this work the use of 

 the porphyrin a carboxylic acid (CO2H replacing CHO) was found useful, 

 since it abolished by-reactions due to the sensitivity of the formyl group to 

 oxidation. This compound had been obtained by mild chromic acid oxidation 

 of the acetate of porphyrin a, followed by hydrolysis of the acetate of the 

 oxidation product. As expected, oxidation of the a-hydroxyalkyl to ketonyl 

 by chromic acid-H2S04 in acetone decreased R III/IV (see above) from 

 1-75 to 0-78. If the reaction was carried out with porphyrin a itself (R III/IV 

 2-3), a compound of R III/IV 1-27 with intact formyl group was obtained in 

 addition to the carboxylic acid compound with R III/IV 0-78. The resulting 

 porphyrins resembled acetylporphyrins spectroscopically. Confirmatory 

 evidence was obtained by dehydration. Using either porphyrin a carboxylic 

 acid or porphyrin a alcohol (CH.jOH replacing CHO), the a-hydroxyalkyl 

 side chain could be demonstrated by the band shift (2-3 m.[i towards the red) 



