CHEMICAL NATURE OF ANTIBIOTICS 



59 



( )tli('r ant ihioties of the "ncomyciii "iroup" 

 inchule catcnulin, paromomycin, ht/droxy- 

 myviii, and amminosidin. 



iMisceilaneous Sugar-containing Coni- 

 poiuids 



The simplest of the antibiotics of this 

 group is trchalosaminc. This antibiotic has 

 the basic skeleton of the disaccharide treha- 

 lose, but in one of the glucose moieties a 

 hydroxyl gi'oup is replaced by an amino 

 group. Its biological activity is slight. 



Novobiocin is an acidic antibiotic, the 

 molecule of which consists of three moieties: 

 (1) a sugar, (2) a substituted coumarin, and 

 (3) a substituted benzoic acid : 



Chartreusin is a \veakl3- acidic, glucosidic, 

 nonnitrogenous substance which is active 

 against gram-positive bacteria and the exact 

 structure of which is not yet known. Its 

 molecule is formed of an aromatic micleus 

 containing three benzene rings linked to a 

 disaccharide chain composed of D-fucose 

 and D-digitalose. 



Cclcsticctin is an amphoteric substance 

 also active against gram-positive bacteria. 

 Its acid hydrolysate yields a sulfur-contain- 

 ing base (desalicetin), salicylic acid, L-hygric 

 acid, and a reducing amino sugar (celestose). 



The ristocetins are mixtures of at least 

 two compounds which are active mainly 

 against gram-positive bacteria. Acid hy- 



CH3O 



NHCO 



CH2— CH=C(CH3)2 



The sugar, which is called noviose, includes 

 a methoxyl and a carbamate group. In dilute 

 alkali reaction, the carbamate group is 

 shifted to the carbon indicated l)y a star to 

 form an isomer of novobiocin, isonovol)io- 

 cin, which is biologically inactive. 



Hygromycin is a weakly acidic sul)stance 

 which is active against bacteria and is also 

 toxic to worms. Its molecule is formed of 

 three cyclic moieties: (1) an aminated inosi- 

 tol moiety which is believed to have a meth- 

 ylenedioxy group attached, (2) a hydrox- 

 ylated and methylated cinnamic acid moiety, 

 and (8) a hexose (5-keto-()-desoxyarabo- 

 hexose) : 



OH 



CH3— CO- 



O 



-/ N- 



drolysis of the mixture yields D-araljinose, 

 glucose, mannose, rhamnose, and a ninhy- 

 drin-positive sul)stance. 



Strcptothricins 



Strcptothricin was the first basic, water- 

 solui)le antibiotic with activity against 

 gram-positive and gram-negative bacteria 

 to be isolated. Because of its toxicity it was 

 never used clinically. 



As explained in greater detail in Part B 

 of this book, a large number of substances 

 closely related to strcptothricin have been 

 isolated. All the "streptothricin type" anti- 

 biotics yield on hydrolysis a mixtiu'c of 



OH 

 CH3 



-0- 



.CH=C— CO— NH/ 



OH 



OH OH 



OH 



O— CH. 



