52 



NATURE, FORMATION. AND ACTIVITIES 



CHs CH, 



\ / 



N 



N 



"^N^^N-" 



OH- 



-CH,OH 



NH— CO— CH(NH.O— CH, 



I 



OCH3 



Puromycin is active against bacteria (mainly 

 gram-positive), protozoa, and tumors. Re- 

 moval of the methyltyrosine moiety from 

 the molecule caused a loss in antibacterial 

 activity. The resulting aminonucleoside was, 

 however, acti\-e against protozoa and 

 tumors. 



Nudeocidin is another meml^er of this 

 group of purine-containing compounds. It is 

 active against bacteria and protozoa. It con- 

 tains a G-aminopurine moiety, a carbohy- 

 drate moiety, and sulfur. 



Three antibiotics, amicetin, amicetin B, 

 and bamicetin, are formed of four cyclic 

 moieties, one of which is a pyrimidine: (1) 

 p-aminobenzoic acid, (2) cytosine, (3) a 

 six-carbon sugar-like unit in the furan form, 

 and (4) a dimethylamino sugar, amosamine 

 (C8Hn04N): 



CH.-i CH3 



N 



OH 



OHCH, 



'CH, 



nw ^O' \ / \ 



^'^^ N />— NHCO 



/ \ 



O 



/ 



-N^' 



In the molecules of both amicetin and 

 bamicetin, 



CH, 



! 



R = XHCOC— CH.OH 



I 

 NHo 



The two antibiotics differ in that l)amicetin 

 has one less — CHo group in the glycosidic 

 moiety than does amicetin. In amicetin B, 

 R = XH2 . These three antibiotics are ac- 

 tive mainly against gram-positive bacteria 

 and mycobacteria. It is interesting to note 

 that bamicetin is more active against gram- 

 negative bacteria than are the amicetins. 

 It has been suggested that amicetin B might 

 be a precursor of amicetin. 



Tetracyclines 



The tetracyclines ha\'e in common a naph- 

 thacene nucleus; their range of biological 

 activity approximates that of chlor- 

 amphenicol; they are active against gram- 

 positive and gram-negative bacteria, ricket- 

 tsiae, and the psittacosis-lymphogranuloma 

 group of organisms. The three commonly 

 used antibiotics of this group are tetracycline, 

 chlortetracycline, and o.vytetracycline. They 

 have the following formulas: 



OH OH 



TetnifvcliiK': R, = R, = H 

 Oxytetiacvfline: Ri = H; R,. = OH 

 Chlortetracycline: Ri = CI; Ri = H 



When chlortetracycline-producing organ- 

 isms are grown in chlorine deficient media 

 that contain bromine, bromine is substituted 

 for chlorine and bromtetracycline is formed. 

 A slight drop in biological activity follows 

 this substitution. 



