PORPHYRINS WITH FOUR COOH GROUPS 63 



One of these porphyrins, the spirographis porphyrin, was. isolated by 

 Fox from chlorocruorin, a hemoglobin-like blood pigment of some 

 polychete worms and snails {931,932). Its structure was investigated 

 by Warburg {2927 ,29 5 If-, 29 57) and finally cleared up by Fischer and 

 Seemann {880) as C2oH6N4(CH3)4(C2H3)(CHO)(CH2CH2C02H)2 

 (Fig. 8). 



Fig. 8. Spirographis porphyrin. 



In the resorcinol melt spirographis hemin is transformed into 

 deuterohemin IX, both the vinyl and formyl groups being removed. 

 This shows that it belongs to the isomeride type of the blood por- 

 phyrins. Spirographis porphyrin has also been synthesized {888) 

 and has been obtained from protoporphyrin by oxidation with osmium 

 tetroxide {806a). 



To the formyl-substituted porphyrins belong also porphyrins 

 derived from chlorophyll b, which have the formyl group in place 

 of one of the methyl groups. 



The simplest method of identifying the presence of a porphyrin 

 containing ^CO groups is the observation of the spectroscopic 

 changes which take place after the compound has been condensed 

 with hydroxylamine or a similar reagent {cf. Chapter VII). 



3.4. Porphyrins with Four and More Carboxylic Acid Groups. 



3.4.1. Coproporphyrins. C2oH6N4(CH3)4(CH2CH2C02H)4. Of the 



four possible isomerides two, coproporphyrin I and coproporphyrin 

 III (Fig. 9) are of special importance. The syntheses of these por- 

 phyrins were carried out by Fischer {801,827,862, cf. also 2872). 

 Coproporphyrin I was first found in feces, later in urine {780-782). 

 Coproporphyrin III was first isolated by van den Bergh and collab- 

 orators {235) from the urine of a patient with chronic porphyria. 

 The alkali salts of coproporphyrins are easily soluble in water. 



