62 



NATURE, FORMATIOX, AND ACTIVITIES 



'Valine ■ 



a-hydroxyisovaleric acid 



valine 

 I 

 a-hydroxyisovaleric acid 



a-hydroxyisovaleric acid 



valine 

 a-hydroxyisovaleric acid 



Netropsin is active against both fungi and ^^'hcYeils anu'domtjcin (C40H68O12N4) is formed 

 bacteria. Its nitrogen content is very high of the following residues: 

 (CisHoeOaXio), and it contains two pyrrole 

 rings, a guanido group, two peptide grovips, 

 and a primary amino group as shown on the 

 facing page. 



A prodigiosin-likc substance which is not 

 so rich in nitrogen (C25H35()N3) also con- 

 tains two pyrrole rings. 



Eidicin is a basic antifungal antil)iotic 

 which contains two guanido groups and a 

 peptide linkage: 



NH OH 



valine - 



The only difference between the two anti- 

 l)iotics is thus four carbons and eight hy- 

 drogen atoms. Valinomycin was reported to 

 have some activity against bacteria, and 



NH.,— C— NH(CH2)8— CH— CH(CH2)3NH> 



NH ! CO(CH.,)sNHC— NH. 



1 II 



NH 



Acid hydrolysis of the base cleaves it, as amidomycin to be antifungal in nature, 

 indicated by the dotted line, and 9-guani- Taber (personal communication) reported, 

 dinononanoic acid and a base, eulicinine, however, that valinomycin also has anti- 

 are formed. ' fungal activity. 



Etamycin is a macrocyclic peptide lactone 

 Polypeptides which is active against gram-positive bac- 



We have already seen that some antibi- teria. Opening of the lactone ring results in 

 otics have molecules which are partly poly- the loss of antibiotic activity. In the follow- 

 peptidic in nature, such as the streptothri- ing formula, the amino acids marked with a 

 cins and the actinomycins. A large number of star had not been found previously in na- 

 antibiotics of actinomycetes are polypep- ture: 

 [3 -hydroxy picolinic acid]* 



[threonine 

 O 



c=o 



. I 



[a-phenylsurccsine]* — [L -alanine] — [/3, N -dimethyl leucine 



[D -leucine] — [D-allohydroxy proline] 

 [sarccsine] 



tides strido sensu. The exact struct vu-e of 

 only a few of them is known. 



Two rather simple polypeptides, amido- 

 mycin and valinomycin, have very similar 

 molecules. Valinomycin is a cyclic polypep- 

 tide (C36H60O12X4) formed of the following 

 units : 



, valine^ 



lactic acid 



I 



valine 



I 



a-hvdroxvisovaleric acid 



a-hydroxyisovaleric acid 

 valine 



lactic acid 



' valine 



Staphylomycin S and mikaiyiycin B are 

 very similar to etamycin. 



3-Hydroxypicolinic acid is also found in 

 the molecule of pyridomycin, a polypeptide 

 antibiotic which is active mainly against 

 mycobacteria. 



The complete structures of other poly- 

 peptide antibiotics of actinomycetes are not 

 known. In the case of some of them the 

 products of hydrolysis are known; of others, 

 nothing is known except that they are poly- 

 peptides. 



