4 Essays in Biochemistry 



the illudins, has a free carbonyl group, but unlike them it also has a 

 free carboxyl group which can be esterified to yield a monoester. 



Larger Polycyclic Molecules 



This group includes ochracic acid and pleuromutilin. Ochracic acid 

 was isolated from culture liquids of Corticum ochraceum. It has not 

 yet been crystallized, but a pure freeze-dried preparation analyzed as 

 a dicarboxylic acid of molecular formula CssH^-^Ot and was active 

 against Staphylococcus aureus at a concentration of about 0.1 fxg. per 

 ml. (about one-tenth the activity of penicillin in our assays). 



Pleuromutilin, C22H34O5, was isolated from culture liquids of Pleu- 

 rotus mutilus, Pleurotus passeckerianus Pilat, 9 and Drosophila suba- 

 trata, 10 and its structure was partly elucidated as that of a polycyclic 

 compound containing two hydroxyl groups, a hindered carbonyl group, 

 and, possibly, a lactone ring. 11 



Halogenated Aromatic Compounds 



This group is represented only by p-methoxytetrachlorophenol (V) , 12 

 a rather effective antifungal agent 13 obtained from culture liquids of 

 Drosophila subatrata. 10 



OH 



!ci 

 0CH3 



v 



Halogenated aromatic compounds have been reported previously as 

 fungal products, but the mechanism of biological halogenation is still 

 obscure. 14 It is interesting, in this connection, that MacMillan 15 iso- 

 lated the bromine analog of griseofulvin from culture liquids (of 

 Penicillium griseofulvium and Penicillium nigricans) in which potas- 

 sium bromide had been substituted for the chloride. 



Polyacetylenes 



The term polyacetylenes, as used here, indicates compounds with 

 two or more triple bonds, in conjugation. This class of compounds 

 has proved to be the largest group and comprises about as many 

 compounds as are included in the other four groups combined. It 

 includes nemotin, nemotinic acid, 16 drosophilin C, drosophilin D, 10,1T 

 agrocybin, 16,18 biformyne 1, biformyne 2, 19,2 ° diatretyne amide, 16,21 



