CHEMICAL NATURE OF ANTIBIOTICS 



57 



has not been elucidated, but they are known 



to he formed of a large macrolide ring to 



which is attached mycaminose and my- 



caro.se, already found in the carbomycin 



molecule, and which in addition contains 



another amino sugar moiety of the following 



structure: 



CH3 



N- 



CH3 



CH3 



-OH 



Longisporin is an antibacterial antibiotic, 

 the complete structure of which is not 

 known. Preliminary data indicate the exist- 

 ence of a large multilactone ring (three 

 lactone groups) of 36 carbons. 



A compound which is somewhat similar 

 to the antibacterial macrocyclic lactones is 

 nocardamine. It has an odd molecular struc- 

 ture with a nine-membered ring with an ad- 

 jacent three-membered ring. It has one 

 weakly acidic and no basic center: 



OH 



It is active only against mycobacteria. 

 Streptomycins 



Streptomycin is active against gram-posi- 

 tive and gram-negative bacteria and myco- 

 bacteria. Its molecule is composed of three 

 moieties — .streptidine, streptose, and X- 

 methyl-L-glucosamine : 



C 

 CHO 



Streptidine is a diguanido derivative of 

 inositol. The hydrogenation of streptomycin 

 under pressure, in presence of platinum oxide 

 or palladium black, results in the reduction 

 of the aldehyde group in the pentose, 

 streptose. The resulting compound, which 

 is biologically active and is chemically more 

 stable than streptomycin, is called dihydro- 

 streptomycin and can also be produced di- 

 rectly by certain Strcptomyces. Another 

 chemical transformation is the removal of 

 an oxygen at the same site, with the forma- 

 tion of dihydrodcso.rystreptomycin: 



CHO— C— OH 



I 

 Streptomycin 



I 

 CH2OH— C— OH 



1 )ihy(ho8treptoniycin 



CH.OH— CH 



Dihydrodeso.xystreptomycin 



Streptomycin-producing strains of S. 

 griscus form not only streptomycin but 

 also a D-mannoside of streptomycin whicii 

 was at first called streptomycin B and is 

 now called manno.sidostreptomycin. The 

 mannose moiety is attached, in the pyranose 

 form, to the 4 position of the X-methyl-L- 

 glucosamine nucleus. Mannosidostreptomy- 

 cin is only about one third as active as 

 streptomycin. 



OH 

 Methylglucosamine 



Streptose 



OH Oh 



Streptidine 



