Pfizer Handbook of Microbial Metabolites 



434 



f. PYRROLES, PORPHYRINS AND RELATED COMPOUNDS 



Pyrroles occur rather frequently as microorganism me- 

 tabolites. They are constituents of porphyrins, of vitamin 

 B^o, of certain bacterial pigments, and of some compounds 

 which have been considered as antibiotics. 



More has been published concerning the biosynthesis 

 of the complex substances because of their more general 

 import in biological systems, but it is tempting to specu- 

 late on the origins of the simpler compounds even though 

 little evidence is yet available. 



Holomycin is the simplest of three similar substances 

 produced by streptomycetes, although the structures of 

 aureothricin and thiolutin were determined earlier. The 

 skeletons of glycine and cysteine are perceptible within 

 the holomycin molecule, and, superficially, it seems that 

 a biosynthetic route related to the following might take 

 place : 



NHo 



S C— OH CH,— NHzlCOCHs 



_ S CH C=0 



XH2^ ^NH^ 

 I 

 NH2 



I 

 HOOC— CH— CH2 O 



I II 



S C- CH— NH2(COCH3 



— H2O 



/ 



\CH2^ \n/ 



CH C=0 

 H 



II 



