Polyenes and Polyynes, 



Excluding Polyene Macrolides 



The polyenes of this section somewhat resemble crocetin, 

 bixin and the carotenes in their long systems of conjugated 

 double bonds with the resultant color and other physical prop- 

 erties, but they lack the isoprenoid structure. 



The acetylenic compounds often occur in low yields and in 

 complex mixtures. While generally colorless, they are conspic- 

 uous by their strong and characteristic ultraviolet absorption 

 spectra. Many of them are unstable. 



From the examples reported to date it seems that basidiomy- 

 cetes are the principal producers of such metabolites among 

 microorganisms, although such substances occur widely in 

 higher plants. That lower fungi are capable of forming poly- 

 enes is demonstrated, however, by the side-chains of metabolites 

 classified elsewhere, for example fumagillin, sorbicillin and 

 auroglaucin : 



C— (CH=CH)o— CHs 



C— (CH=CH)4— COOH 



II 

 O 



Fumagillin Sorbicillin 



