Streptomycin, structure determination

The widespread interest in fundamental information regarding the molecular structure of such an important antibiotic facilitated the rapid elaboration of the structure of streptomycin. The substance has been well characterized with regard to its antibacterial activity, protective and toxic effects and other biological properties. The investigations which led to the elucidation of the chemical structure of streptomycin form a noteworthy display of the more modern methods for structural determination and comprise a valuable contribution to carbohydrate chemistry. 

Hygromycin A [1] is classified chemically as a member of the aminocyclitols antibiotic family represented by streptomycin and kanamycin. Its structure determined by degradation and spectral analyses, (72, 13) revealed that it consists of three unusual moieties, namely S-dehydro-a-L-fucofuranose, ( )-3-(3,4-dihydroxyphenyl)-2-methylacrylic acid, and an aminocyclitol (2L-2-amino-2-deoxy-4,5-0-methylene- eo-inositol). The 5-dehydro-a-L-fucofuranose moiety is attached by a glycosidic linkage of the 4-hydroxy position of ( )-3-... 

The anti-bacterial activity of the penicillins stimulated a major search for other antibiotics. Many compounds were isolated from amongst the metabolites of Streptomycetes obtained from soil. These included therapeutically useful antibiotics such as chloramphenicol, the tetracyclines, erythromycin and streptomycin. Several fungi yielded useful compounds. One of these was Cephalosporium acremonium. A biologically-active strain was obtained by Brotzu from a sewage outfall near Cagliari in Sardinia in 1945 and described in 1946. The p-lactam cephalosporin C (1.23) was isolated from this organism in 1954 and its structure determined in 1961 by Abraham and Newton. 

The complete structure of the inactivated streptomycin was determined by Umezawa and coworkers" and Davies and coworkers." Methanolysis of the inactivated streptomycin in 0.5 M hydrogen chloride in methanol for 24 hours at 30° gave methyl adenylylstreptobiosaminide dimethyl... 

Similar prolonged ethanethiolysis of D-mannopyranosylstreptomycin 46) produced ethyl 1-thio-a- and -jS-D-mannopyranosides, isolated as acetates. Likewise, streptomycin was cleaved with ethanethiol and hydrochloric acid 47) to produce ethyl 1-thiostreptobiosaminide diethyl dithioacetal hydrochloride. This type of cleavage is useful in structure determination since the carbonyls are protected with thioacetal groups as they are released 4S). It was by means of this reaction that the nature of the acid-sensitive strep-tose portion of streptomycin was elucidated. (See Chapter X.)... 

The absolute configuration of the streptidine moiety was determined by Dyer and A. W. Todd by applying Reeves s copper-complexing method to N,N -diacetyl-4-deoxystreptamine, derived from streptomycin by degradation. Moreover, the same conclusion was reached by Tatsuoka and coworkers on applying the Reeves method to 2,6-di-O-methylstreptamine derived from dihydrostreptomycin this revealed that the streptobiosamine moiety is attached to C-4 in the R configuration. The absolute structure of streptomycin was confirmed by an X-ray analysis of streptomycin oxime selenate. ... 

Streptomycin and dihydrostreptomycin have very similar chemical structures and so many of the chemical methods which are available are equally applicable to both antibiotics. Certain procedures have a measure of specificity however and may be used for the determination of one of the substances in the presence of the other. The B.P. relies upon microbiological assay (see p. 813) for determination of the potency of both these antibiotics, which are official in the form of their sulphates. 

Studies of laboratory-derived (single-step) resistant mutants have proved to be of considerable biochemical utility. For example, streptomycin-resistant mutants have an altered receptor site due to a change in a protein of the small ribosomal subunit, while erythromycin-resistant mutants have a change in a protein of the large ribosomal subunit 7. Altered RNA polymerases are found in mutants resistant to rifampicin and streptol-ydigin 9. Fusidic acid resistance occurs as a result of mutations which alter a factor required in protein synthesis O. Such forms of antibiotic resistance have been useful in determining the mode of action of the antibiotic and in studies of macromolecular structure and function. By contrast, in "natural" resistance, the resistance mechanism is, in most cases, unrelated to the biochemical mode of action of the drug. The antibiotics with known plasmid-determined resistance are listed in Table 2. 

---