314 



DESCRIPTIONS OF ANTIBIOTICS 



Biological activity: YinuaUy identical to that of 

 methymycin, except that neomethymycin is 4 

 times more active on B. subtilis (2). 



References: 



1. Djerassi, C. and Halpern, D. J. Am. Chem. 



Soc. 79: 2022-2023, 1957. 



2. Djerassi, C. and Halpern, I). Tetrahedron 



3: 255-268, 1958. 



Neomycin 



Produced by: Streptomyces fradiae, S. albogrise- 

 olus, Streptomyces sp. (2). 



Synonyms: Similar to or clo.sely related to strep- 

 tothricins BI and BII, flavomycin, framycetin, 

 catenulin, dextromycin, colimycin (7), miserin 

 (6), mycerin, and antibiotic 956 (5). 



Remarks: Among the various preparations com- 

 prising neomycin fractions, framycetin occupies 

 a prominent place. Since considerable literature 

 has accumulated concerning this preparation, it 

 is discussed separately. 



Method of extraction: I. Clarification of broth 

 at pH 2.0 with charcoal. Adsorption of neomycin 

 at alkaline pH on charcoal; elution with acidic 

 ethanol or acetone. II. Adsorption of neomycin 

 on IRC-50 (resin eciuilibrated at pH 7 to 8 with 

 alkali); elution with aciueous HCl, H2SO4 , or 

 ammonia. Freeze dried. III. Alkylbenzene or 

 alkylnaphthalene sulfonic acid added to broth at 

 pH 3 to 5; the resulting sulfonic acid salt of neo- 

 mycin extracted with butanol. Re-extracted into 

 dilute mineral acid. Neutralization and removal 

 of excess mineral acid with Ba(0H)2 or Ca(0H)2 

 or with suitable ion exchange resin. Purification 

 (a) by conversion of one salt to another; i.e., neo- 

 mycin sulfate to the p-hydroxyazobenzene-p'-sul- 

 fonate salt to the purified hydrochloride; (b) by 

 suitable ion exchange resins (Amberlite XE-89 

 and Dowex 50 X16); (c) by acetone precipitation 

 of ash from an aqueous neomycin solution at pH 

 10.1 and subsetiuent acetone precipitation of 

 purified neomycin sulfate from the neutralized 

 filtrate; (d) by carbon chromatography. Separa- 

 tion of neomycins B and C l)y chromatography on 

 carbon or alumina (2). 



Che7nical and physical properties: Neomycin is a 

 complex composed of two isomeric entities: neo- 

 mycin B and neomycin C. 



Neomycin B 



Free base: Colorless, amorphous solid, [a]^ = 

 +83° (c = 1 to 2 per cent in 0.2 A' HCl). Very sol- 

 uble in water; insoluble in ethanol or methanol. 

 Sulfate: Colorless, amorphous solid. [a]jj = +58° 

 (c = 0.5 per cent in water) or +56°. Same solu- 



bility as free base. Base content about 68 per 

 cent. Reineckate: Pink platelets from aqueous 

 acetone. Insoluble in water; soluble in hot water 

 and acetone. N-Acetate: Colorless needles from 

 aciueous acetone; m.p. 200-205°C (decomposition); 

 softens at 185-190°C. [a]l = +62° (c = 0.4 per 

 cent in water). Acetyl content 32 per cent. Bio- 

 logically imictive; cannot be converted to free 

 neomycin. 



Neomycin C 



Free base: Colorless amorphous solid, [a]^ = 

 + 121° (c = 1 to 2 per cent in 0.2 N H2SO4). Very 

 soluble in water; insoluble in ethanol or methanol. 

 Sulfate: Colorless, amorphous solid. [aJr, = +82° 

 (c = 0.5 per cent in water). Same solubility as free 

 base. Base content al)out 68 per cent. Helianthate: 

 Similar to neomycin B. N -Acetate: Colorless nee- 

 dles from aqueous acetone; melting point similar 

 to neomycin B N-acetate, but gives 10° depres- 

 sion in mixed melting point determination, [al^ = 

 -f90° (c = 0.4 per cent in water). Acetyl content 

 32%. Biologically inactive; cannot be converted 

 to free neomycin. 



Neomycin Complex 



Basic, white substance. Water-soluble; insoluble 

 in organic solvents. C2:iH46N60i3 . No typical 

 ultraviolet spectrum (2). Infrared spectrum given 

 in reference 1. Positive Molisch, carbazole, and 

 ninhydrin tests. Negative Elson-Morgan, Fehling, 

 and Tollen tests. No acidic, carbonyl, methoxyl, 

 guanidine, or free aldehyde groups. Crude neo- 

 mycin is stable from pH 2 to 9; highly purified 

 preparations stable to alkali only (1, 2). Acid 

 hydrolysis products include a nonreducing base, 

 neamine (neomycin A), C12H24-26N4O6 , and a 

 methylglycoside moiety. 



Nea))une 



Precipitates from alcoholic ammonia as fine 

 needles; m.p. 250-256°C (decomposition). [a]o = 

 + 123° (c = 0.7 per cent in water). Infrared spec- 

 trum given in reference 2. Tentative structure of 

 neamine : 



H H 



C6H903(NH2)2---0 



Diaminohexose 



NH2 



OH H 

 2- Desoxystreptamine 



