Pfizer Handbook of Microbial Metabolites 



122 



C— O— H 



^ C-O-H 



I 



c=o 



1 



H 



CH3 O OCOCH3 



Proposed Precursor of the Proposed Glycol-aldehyde 



Lactone Portion of Corbomycin Rearrangement at 7,8-Positions 



Such a precursor is the more plausible because it would have an 

 1 8-membered carbon atom chain and a C-19 carbon skeleton, 

 the same as that of the known tuberculostearic acid, even in- 

 cluding the stereochemistry of the branching methyl group. 



Streptomyces species produce many antifungal antibiotics 

 which have in common chains of conjugated olefinic bonds. By 

 means of the ultraviolet absorption spectra it is possible to clas- 

 sify them according to the length of the conjugated chain. 

 Generally these substances are rather intractable with low solu- 

 bilities and indefinite melting points. 



A structure has been proposed for pimaricin, a tetraene. 

 Whether or not this structure proves to be entirely correct, there 

 is evidence from several sources that at least certain of these 

 substances are macrocyclic lactones. 



So many of these compounds have been reported lately that 

 any listing is likely to be incomplete. The following table must 

 include most of them, however, grouped by number of conju- 

 gated olefinic bonds. 



TABLE I 



