Method for Producing Rosaramicin (Rosamicin)

This invention relates to a novel composition of matter and to a process for the production thereof. More particularly, this invention relates to a new compound, hereinafter most often called rosaramicin, but sometimes referred to as rosaramicin, to its non-toxic pharmaceutically acceptable 2'-monoesters and 3,2'-diesters and to the non-toxic pharmaceutically acceptable acid addition salts of each. This invention also relates to a process for the production of said antibiotic by microbiological fermentation of an elaborating microorganism.

Rosaramicin is a biosynthetic elaborate obtained by cultivating a rosaramicin producing species of Micromonospora in an aqueous nutrient medium. The antibiotic is a basic substance. It and its 2'-monoesters, its 3,2'-diesters and the acid addition salts of each, have the property of adversely affecting the growth of microorganisms, and in particular, gram-positive bacteria.

The microorganism used according to this invention for the production of rosaramicin has been named Micromonospora rosaria (sometimes hereinafter referred to as M. rosaria). This species was isolated from a soil sample taken from a park (Little Thicket) in San Jacinto County, Texas. One of its strain characteristics is its ability to produce rosaramicin. A culture of the living organism has been made a part of the permanent collection of the Northern Utilization and Research Division. Agricultural Research Service, U.S. Department of Agriculture, Peoria, Illinois, where it has been assigned accession number NRRL 3718. Sub-cultures of M. rosaria NRRL 3718 are readily available to the public from the foregoing Agency upon request. M. rosaria is aerobic and grows well on a variety of solid and liquid nutrient media. It exhibits especially good growth and antibiotic production under submerged aerobic conditions.

M. rosaria may be distinguished from other species of Micromonospora by a variety of taxonomical parameters. For example, after 14 days of incubation at 24.degree.-26.degree. C. on an agar medium comprising 3% NZ Amine Type A (Sheffield Chemical Company, Norwich, New York), 1% dextrose and 1.5% agar, growth is observed to be fair. Macroscopically, there is no apparent aerial mycelium. Colonies are slightly raised and are granular to weakly folded. No diffusible pigment is observed. In describing the color formations for this observation and others, the following system and references are employed: The color designations consist of two designators. The first is a color name taken from the "Descriptive Color Name Dictionary" by Taylor, Knoche and Granville, published by The Container Corporation of America (1950) USA, with a color chip number corresponding to the color name, the chip number being taken from "The Color Harmony Manual", 4th Edition, 1958, published by The Container Corporation of America. The second designator consists of a color name and number which refers to the synonym or near synonym found in the National Bureau of Standards, Circular 553, Nov. 1, 1955 (USA).

When grown on the above-mentioned medium the colony surface color is chestnut brown g4ni; moderate brown 58. Although colony surface color and pigment formation on a particular medium are generally characteristic of microorganisms, both may be temporarily or permanently sub-cultured. Microscopically the mycelium is branched averaging 10 to 20.mu. in length. The mycelium has a diameter of approximately 0.6.mu.. Numerous chlamydospores are produced, the spores being up to 2.0.mu. in diameter. Conidia are not observed when the above-described medium is employed.

M. rosaria grows well at 27.degree.-37.degree. C.; no growth occurs at 50.degree. C. A growing colony of M. rosaria will hydrolyze gelatin, milk and starch but will not reduce nitrate to nitrite. The foregoing tests are applied as described by Gordon et al. J. Bacteriology 69:147 (1956) and 73:15 (1957).

Additional culture characteristics of M. rosaria are set forth in Table I:

M. rosaria is capable of utilizing a variety of carbon and nitrogen sources. In Table II there is set forth observations on carbohydrate utilization. A visual estimate of the degree of growth is observed in a medium consisting of 0.5% yeast extract, 1% of the indicated carbohydrate and 1.5% agar all in distilled water.

In Table III, nitrogen utilization is set forth as determined by visual estimate of growth on agar plates in a medium consisting of 1% glucose, 1.5% agar, and the specific nitrogen source in the amount indicated, all in distilled water.

Micromonospora rosaria grows well and elaborates an antimicrobial product when grown on a number of nitrient media. Exemplary of such media are the following:

In addition, many other media may be utilized for the growth of M. rosaria and for the production of rosaramicin those set forth above being only exemplary and in no way limiting.

Rosaramicin, is produced when the elaborating microorganism, M. rosaria is grown in an aqueous nutrient medium under submerged aerobic conditions. For small amounts of antibiotic, e.g., microgram to milligram quantities, surface culture in bottles or shake flasks may be employed. Typically, the nutrient medium is liquid, contains a carbon source such as an assimilable carbohydrate and an assimilable nitrogen source, such as a proteinaceous material. Preferred carbon sources include glucose, mannitol, levulose, sucrose, starch, ribose and the like. Preferred nitrogen sources include corn steep liquor, yeast extract, soybean meal, meat peptones, casein hydrolysate, beef extract and the like. It is advantageous to use combinations of these carbon and nitrogen sources to provide good growth and antibiotic production.

Production of rosaramicin may be effected at most temperatures conducive to satisfactory growth of the microorganism; e.g., between 20.degree. and 40.degree. C., preferably 27.degree.-35.degree. C. Ordinarily, optimum production is obtained in 2-7 days. The pH of the medium is maintained between 6.0 and 8.5 during the fermentation, a pH of between 7 to 8 being preferred. Prior to sterilization and inoculation, the fermentation medium is usually adjusted to pH 7.0, readjustments being made as required during the course of the fermentation. Alternatively, the pH may be maintained at about 7.0 by the use of buffering agents such as calcium carbonate. These buffering agents generally tend to persist throughout the course of the fermentation.

When growth is carried out in large vessels and tanks, it is desirable to produce a vegetative inoculum of about 5% of the volume of the tank in a nutrient broth by inoculating the broth culture with a slant culture or a lyophilized culture of the organism. This, the germination stage of the fermentation, usually requires from about 24 to about 120 hours with about 72 to 96 hours being preferred. When an active inoculum has been obtained, it is transferred aseptically to the larger vessel or tank containing sterile medium. During the course of the germination stage and the fermentation stage which follows, the tendency of the medium to foam is controlled by the addition of a suitable antifoaming agent, such as, Dow Corning B.RTM., The Dow Chemical Company, Midland, Mich.

The medium in which the vegetative inoculum is produced may be identical to that utilized for the production of antibiotic or it may differ so long as the medium is one in which good growth of the microorganism is obtained (e.g., similar to Media A, B or C above).

The fermentation stage usually requires from about 24 to about 100 hours. It is to be noted, however, that peak antibiotic production is often reached in less than 72 hours. The determination of peak antibiotic production is made by sampling the fermentation at various intervals and assaying the samples. When the production of antibiotic levels off, the whole broth is made alkaline, preferably to about pH 9.5 by the addition of base, such as, an alkali metal or an alkaline earth metal hydroxide, preferably sodium hydroxide. The antibiotic is extracted from the fermentation medium with a water immiscible organic solvent such as benzene, toluene, n-butanol, methylene chloride, chloroform, ethyl acetate, amyl acetate and the like, the preferred solvent being ethyl acetate. The extract is concentrated, preferably in vacuo, to about 1/50 of the volume of the fermentation medium. The biologically active material in the concentrate is then extracted into an aqueous solution of mineral acid, preferably 0.1 N sulfuric acid. In this manner, rosaramicin is partially separated from the plurality of minor components produced by the fermentation. In those cases wherein the rosaramicin solution still contains some of the co-produced minor components, the solution may be made basic (pH 9.5) and the above-described procedure repeated. The presence of the co-produced minor components may be determined by chromatographic procedures. The aqueous acid extract of rosaramicin obtained by the foregoing procedure is made basic (about pH 9.5) and is reextracted with a suitable immiscible organic solvent. The extract is concentrated, preferably in vacuo, to about 1/1000 of the original fermentation volume and is precipitated into about 10 volumes of a vigorously stirred solvent mixture comprising about 6 volumes of ether and about 4 volumes of hexane. The resulting precipitate is filtered and washed sparingly with a fresh portion of the ether-hexane mixture and set aside. The filtrate containing the antibiotic activity is evaporated to a residue and the residue dissolved in a suitable non-water miscible solvent, washed several times with water and dried over a suitable drying agent, such as anhydrous sodium sulfate. After filtration, the solution is concentrated to a residue, the residue dissolved in a minimal amount of ether, the solution filtered and added to petroleum ether (boiling point 30.degree.-60.degree. C.) with stirring. A precipitate is obtained which is usually off-white to buff colored. This precipitate is filtered, washed sparingly with petroleum ether and dried in vacuo at about 40.degree. C. Material obtained in this manner usually has a potency of about 70 mcg/mg as determined by the following assay procedure:

The assay technique employed in a cylinder cup assay using Bacillus subtilis ATCC 6633 as the test organism.

The physical conditions of the assay consist of a base layer of 21 ml and a seed layer of 4 ml of Antibiotic Medium No. 5. A standard curve is plotted using the following concentrations of antibiotic (mcg/mg) in 0.1 M phosphate buffer (pH 8.0): 0.64, 0.8, 1.0, 1.25 and 1.56. The reference standard has been assigned a potency of 1000 mcg/mg which means that one (1) mcg of the standard in 1.0 ml of 0.1 M phosphate buffer will give a zone of inhibition of 17.8.+-.1.0 mm against the test organism (B. Subtilis ATCC 6633). The test procedure and the test medium is substantially that described for erythromycin in Assay Methods for Antibiotics, D. C. Grove and W. A. Randall, Medical Encyclopedia Inc., New York, New York (1955) pages 96-103.

Purification may also be effected by preparing suitable derivatives such as hydrocarboncarboxylic acid esters and/or acid addition salts, purifying the derivative and regenerating the free antibiotic.

Alternatively, rosaramicin assaying about 700 mcg/mg may be purified by chromatographic techniques such as the following: Dissolve the antibiotic in about nine (9) parts of halogenated lower alkane containing about 1 part of an alcohol by volume (e.g., chloroform:methanol) and place atop a column containing a solid adsorbent such as silicic acid, alumina, magnesium silicate, diatomaceous earth, cellulose and the like, preferably silica gel. The column is eluted with a mixture comprising about 80% of a chlorinated lower alkane, preferably chloroform and 20% of a lower alcohol, preferably methanol. Fractions are collected and a sample of each fraction is disc tested against Staphylococcus aureus. Antibiotic containing fractions are chromatographed on silica gel thin-layer plates using the same solvent mixture used on the column. This chromatographic technique is also used to determine the effectiveness of the initial separation described above, (i.e., the distribution between water and an immiscible organic solvent). In general at least two plates per fraction are run. One plate is sprayed with a suitable spray such as methanol-sulfuric acid, and heated until the location of organic matter is discernible (dark spot). The second plate is used for bioautography against Sarcina lutea to detect the presence and location (R.sub.f) of biologically active material. When chloroform:methanol (4:1 by volume) is used and the chromatogram is run for about 1 hour, rosaramicin has and R.sub.f of about 0.75.

The fractions containing biologically active material of like mobility (R.sub.f) are combined and concentrated, preferably in vacuo, to a residue. The residue is dissolved in acetone and precipitated by the addition of ether. Substantially all of the antibiotic remains in the supernatant and may be isolated by filtration or by centrifugation and by evaporating the filtrate (supernatant) to a solid residue. This method generally affords rosaramicin assaying about 1000 mcg/mg. Alternatively, the antibiotic may be isolated by concentrating the original broth extract to a residue, chromatographing the residue and working-up the fractions by the procedure just described.

I. Chromatography

Table IV below sets forth the results obtained by chromatographing rosaramicin in several solvent systems. The chromatography is performed on silica gel GF plates, (thickness 250 microns) which are available commercially from Analtech Inc., Wilmington, Del. 19801, under the trade name Uniplate.RTM..

II. Elemental Analysis

III. Solubility

IV. Infrared Spectrum

The infrared spectrum of rosaramicin as a mineral oil mull is shown in FIG. 1. The major peaks and bands are set forth in Table VII below. The numerical designations are in microns: the peaks attributable to mineral oil have been omitted.

V. Nuclear Magnetic Resonance Spectrum

Rosaramicin has a characteristic nuclear magnetic resonance spectrum as shown by FIG. 2. The NMR spectrum was obtained by the use of a Varian A-60-A spectrometer (Varian Associates, 611 Hansen Way, Palo Alto, California). The antibiotic (40 mg) was dissolved in about 0.4 ml of deuterated chloroform containing a small quantity of deuterium oxide. The spectrum is recorded in parts per million (PPM) from tetramethyl silane (TMS), the internal standard. In FIG. 2, in addition to a full NMR spectrum running from 0 to 8 PPM, there is also shown a partial spectrum appearing at about 6.8 PPM. This peak normally would appear at about 9.8 PPM but would be outside the range of the spectrum normally recorded. In order to record this peak, the spectrometer was offset 180 Hz which is equivalent to about 3 PPM. In view of the intensity of the peak, it is deemed to be material to an accurate interpretation of the spectrum especially since it is indicative of the presence of an aldehyde function of the antibiotic molecule.

VII. Stability--(pH)

The activity of rosaramicin is not affected to a substantial degree upon being dissolved in ethanol, diluted with buffer and heated to a temperature of 100.degree. C. for 30 minutes throughout the pH range of 2-10.

VIII. Stability to Enzymes

Rosaramicin has been tested for stability against trypsin, chymotrypsin, pepsin, and .alpha.-amylase. Solutions of the enzymes were prepared at 1 mg/ml in McIlvaines buffers at the optimal pH for the enzyme (i.e., trypsin and chymotrypsin pH 8; pepsin, pH 2.2; and .alpha.-amylase pH 4). Two hundred (200) mcg of antibiotic was dissolved in 0.5 ml of water, mixed with 0.5 ml of enzyme solution and incubated at 37.degree. C. for 24 hours. The solutions were disc assayed against Escherichia coli and Staphylococcus aureus after 0, 1, 2.5 and 24 hours incubation. The enzymes caused no substantial loss in activity of the antibiotic over the 24 hour interval.

IX. Color Tests

Rosaramicin gives a positive color reaction in the Molisch, Starch -KI and Elson-Morgan tests; and a negative color reaction in the biuret, ninhydrin and Sakaguchi tests.

On the basis of the foregoing physiochemical data, it is believed that rosaramicin (rosamicin) has the following flat (planar) structure, no stereochemical assignments are being suggested by such structure: ##STR1##

It is evident from the foregoing physiochemical data that (rosaramicin) is the same antibiotic designated as Juvenimicin A.sub.3 in U.S. Pat. No. 3,767,793, the disclosure of which is incorporated by reference. That patent discloses the preparation of this antibiotic by culturing a Juvenimicin-producing microorganism belonging to the genus Micromonospora, e.,g., Micromonospora chalcea var. izumensis (Strain No. T1124; deposited at the Institute for Fermentation, Osaka, Osaka, Japan, accession number IFO-12988, and at the American Type Culture Collection, accession number ATCC 21561).

The antibiotic isolated from the culture of that microorganism had the following properties:

(1) Elementary analysis

C:62.97.+-.1.0; H:8.62.+-.0.5; N:3.00.+-.0.5

(2) Specific rotation:

[.alpha.].sub.D.sup.25 =17.6.degree. (c.=0.29% in CHCl.sub.3)

(3) Molecular weight:

(a) Vapor pressure osmosis method:

541.+-.60 (in C.sub.6 H.sub.6)

(b) Titration method: 562.+-.60

(c) Highest mass number: m/e=581

(4) pK.sub.a :

8.4 (in 66% dimethylformamide)

(5) Color reaction:

(a) Erythromycin test: negative

(b) Carbomycin test: negative

(c) Dragendorff reaction: positive

(6) Solubilities:

Soluble in benzene, chloroform, ethyl acetate, dimethylformamide, ethanol or an aqueous acid solution;

Insoluble in petroleum ether, n-hexane, or a neutral water

(7) R.sub.f values on thin layer chromatography on silica gel: Eluted with mixture of chloroform, methanol and 7% aqueous ammonia solution (40:12:20): R.sub.f =0.7.+-.0.05.

(8) Ultraviolet absorption:

(9) Infrared absorption spectrum:

The main absorption bands in wave number (cm.sup.-1) in KBr disc are as follows: 3450, 2960, 1725, 1695, 1625, 1458, 1383, 1314, 1276, 1250, 1180, 1167, 1111, 1072, 1047, 1027, 983, 966, 932, 896, 869, 846, 834, 792, 755, 713

The following ranges of physiochemical data embraces both those disclosed for Juvenimicin A.sub.3 in U.S. Pat. No. 3,767,793 and those disclosed in our prior applications Ser. No. 4916 and No. 303,833 for rosaramicin:

(1) Elementary analysis:

C:63.00.+-.1.0; H:8.62.+-.0.5; N:3.0.+-.0.8

(2) Specific rotation

[.alpha.].sub.D.sup.24 =-17.6.degree..+-.18.degree. (C=0.29% in CHCl.sub.3)

(3) Molecular weight:

(a) Vapors pressure osmosis method: 541.+-.60 (in C.sub.6 H.sub.6)

(b) Titration method: 562.+-.60

(c) Highest mass number: m/e=581

(4) pKa: 8.4.+-.1 (in 66% dimethylformamide)

(5) Color reaction:

Dragendorff reaction: positive

(6) Solubilities:

Soluble in benzene, chloroform, ethyl acetate, dimethylformamide, ethanol or an aqueous acid solution: Insoluble in petroleum ether, n-hexane or a neutral water.

(7) R.sub.f values on thin layer chromatography on silica gel:

Eluted with mixture of chloroform, methanol and 7% aqueous ammonia solution (40:12:20): R.sub.f =0.7.+-.0.1

(8) Ultraviolet absorption:

(9) Infrared absorption spectrum:

A main absorption band (cm.sup.-1) in KBr disc appears at a point in each of the following wave number ranges:

3450-3530, 2925-60, 1724-30, 1689-95, 1620-6, 1458-60, 1380-3, 1310-14, 1275-6, 1250, 1180-7, 1165-7, 1110-1, 1070-2, 1043-9, 1025-7, 980-4, 960-6, 930-2, 895-6, 860-6, 930-2, 895-6, 868-9, 934-42, 792, 712-3 plus one at 1400-6 or 755

Rosaramicin is capable of forming non-toxic pharmaceutically acceptable acid addition salts with inorganic and organic acids by virtue of the dimethylamino group at position 3'. By "non-toxic pharmaceutically acceptable acid addition salts" is meant those that do not exhibit toxic manifestations at normal therapeutic doses. Exemplary of such salts are those formed with such acids as hydrochloric, sulfuric, phosphoric, citric, acetic, propionic tartaric, maleic, benzoic, cyclopropylcarboxylic, adamantyl carboxylic and the like. Acid addition salts may be prepared by methods generally used in the art such as by adding a stoichiometric amount of acid to a solution of the antibiotic in a non-reactive organic solvent and isolating the salt by art known methods such as precipitation of the salt with a solvent wherein the salt is not appreciably soluble, e.g., diethyl ether. A non-reactive organic solvent is one which does not react with the antibiotic, the acid or the salt.

The hydroxyl groups at positions 3 and 2' are amenable to esterification to form non-toxic pharmaceutically acceptable esters such as, for example, those formed by reaction with typical acylating agents such as with anhydrides or chlorides of organic acids especially hydrocarbon carboxylic acids. Further, rosaramicin is susceptible to the formation of monoesters at positions 3 and 2' and is capable of being converted into 3,2'-diester. In general, the 2'-monoester may be prepared by selective esterification techniques generally known in the art, such as, for example, treating the free antibiotic with a stoichiometric quantity (or a slight excess) of an acylating agent, such as an acyl anhydride or acyl halide at about ambient temperatures from about 1 to about 20 hours until esterification is substantially complete and isolating the 2'-monoester from the reaction mixture.

In general, 3,2'-diesters may be prepared by treating the free antibiotic with an excess of acylating agent at about ambient temperature for from about 1 to about 7 days until esterification is substantially complete and isolating the 3,2'-diester from the reaction mixture.

Alternatively, 3,2'-diesters may be prepared by treating a 2'-monoester with an excess of acylating agent at about ambient temperature for from about 1 to about 7 days until esterification is complete and isolating the 3,2'-diester from the reaction mixture. The latter procedure is especially advantageous for preparing "mixed" esters (i.e., those having a different acyl group on each of positions 3 and 2').

A 3-monoester may generally be prepared by selective hydrolysis or solvolysis of a 3,2'-diester, the 2'-ester being more susceptible to hydrolytic or solvolytic removal. The preparation of 3-monoesters of rosaramicin is described in application Ser. No. 303,903, filed Nov. 15, 1972, bearing the title, "Novel Monoesters of Rosamicin".

It is to be noted that the 2'-monoesters, the 3,2'-diesters and the 3-monoesters of rosaramicin all have the further property of forming acid addition salts which usually have enhanced water solubility.

I. In Vitro Activity

The in vitro activity of rosaramicin is ascertained by conventional tube dilution procedures using yeast beef broth medium at pH 7.4. The tubes are incubated for 18 hours at 37.degree. C. prior to being observed. The results of a typical determination are set forth in Table IX and demonstrate that the antibiotic exhibits broad antibacterial spectrum in vitro with a greater effect upon gram-positive bacteria.

II. In Vivo Activity

The protective activity and the acute toxicity of rosaramicin is tested in male CF-1 (Carworth Farms) mice weighing approximately 20 gms. each. For protection, the antibiotic is given as a suspension or a solution in an aqueous vehicle containing 0.5% carboxy methyl cellulose (CMC) in two doses; one shortly before and one 4 hours after intraperitoneal infection with the bacteria. Infected and non-treated mice (controls) generally die within 18 hours. Survival rate in the treated group is determined 48 hours after infection.

The acute toxicity of rosaramicin is measured in the standard manner by administering the antibiotic by a variety of routes and determining the LD.sub.50 by standard procedures. The results of in vivo tests using a representative gram-positive and a representative gram negative organism are set forth in Tables X and XI below:

Acute Toxicity

The acute toxicity of rosaramicin is as follows:

Rosaramicin may be used alone or in combination with other antibacterial agents to prevent the growth of, or to reduce the number of susceptible organisms, especially the gram positive organisms set forth in Table IX above. Thus, rosaramicin is useful in wash solutions for sanitary purposes, as in the cleaning of laboratory glassware and equipment. Further, it may be used for laundering purposes such as a bacteriostatic rinse for laboratory uniforms. Additionally, rosaramicin maybe used to treat laboratory and domestic animals that are infected with susceptible organisms.

1. Germination Stage

Under aseptic conditions, inoculate a 300 ml flask containing 100 ml of sterile Medium A with a loopful of M. rosaria culture from an agar slant or add an equivalent quantity of lyophilized culture. Incubate the contents of the flask at about 35.degree. C. for about 72 hours with agitation, preferably on a rotary shaker.

2. Fermentation Stage

Transfer aseptically 5 ml of inoculum from the germination stage to each of a number of 500 ml Erlenmeyer flasks containing 100 ml of sterile Medium B and incubate at about 28.degree. C. for from about 72 to about 100 hours with agitation, preferably on a rotary shaker. After the first 24 hours, the fermentations are sampled periodically and the sample assayed to determine when peak production is attained. When the fermentations are complete, it is usually advantageous to pool them for workup.

Transfer aseptically 25 ml of inoculum (prepared as in the germination stage of Example 1) into a 2 liter Erlenmeyer flask containing 500 ml of sterile Medium A and incubate for about 72 hours at about 28.degree. C.; preferably on a rotary shaker.

2. Fermentation Stage

Transfer aseptically the entire 500 ml of the second germination stage for a 14 liter fermentor containing 9.5 liters of Medium B. Add 6 ml of antifoam (Dow-Corning B) and adjust the pH of the mixture to about 7.0 either with dilute (1.0 N) sodium hydroxide or with dilute (1.0 N) sulfuric acid as required. Ferment the mixture at about 28.degree. C. until peak activity is attained as determined by periodic assay of the fermentation medium. This usually requires from about 72 to about 100 hours.

Adjust the fermentation medium prepared as in Example 2 to about pH 9.5 with 1 N sodium hydroxide and extract the medium with ethyl acetate. Combine the ethyl acetate extracts and concentrate to about 200 ml in vacuo. Extract the concentrate containing biologically active material with about 200 ml of 0.1 N sulfuric acid. Adjust the pH of the aqueous layer to about pH 9.5 with 1.0 N sodium hydroxide solution and re-extract with ethyl acetate. Concentrate the ethyl acetate extracts to about 10 ml in vacuo and precipitate by pouring into about 10 volumes of a vigorously stirred solvent mixture comprising 6 volumes of ether and 4 volumes of hexane. Filter the solution, wash the precipitate sparingly with a fresh portion of the ether-hexane mixture and combine the filtrate and washings. Concentrate the filtrate to a residue; dissolve the residue in about 5 ml of ether and filter the solution. Add the solution to about 10 volumes of petroleum ether (boiling point 30.degree.-60.degree. C.) with stirring to obtain a precipitate. Filter the off-white to buff colored precipitate and wash sparingly with petroleum ether. Dry at about 40.degree. C. in vacuo. The material obtained in this manner usually assays about 700 mcg/mg.

Dissolve the precipitate obtained in Example 3 in a mixture of nine parts by volume chloroform and one part methanol. Add the solution to a column containing 250 gms of silicic acid, and elute the column with a mixture of chloroform (8 parts by volume) and methanol (2 parts by volume). Collect 5 ml fractions at the rate of about 0.5 ml/minute. Sample each fraction and disc test against S. aureus. Chromatograph a portion of each sample on a Uniplate.RTM.. Fractions containing rosaramicin will have an R.sub.f value of about 0.4 to about 0.5. Concentrate these fractions in vacuo to a residue. Dissolve the residue in acetone and add ether to form a precipitate. Remove the precipitate by filtration or by centrification and discard the precipitate. Evaporate the filtrate or supernatant to a solid residue and obtain thereby rosaramicin assaying about 1000 units per mg and having the following physical constants: m.p. 110.degree.-114.degree. C.

[.alpha.].sub.D.sup.25 =-33.4.degree. (C=0.3% ethanol)

E.sub.1 .spsb.cm.sup.1% =238 (240 m.mu.)

Adjust the fermentation medium prepared as in Example 2 to about pH 9.5 with one normal sodium hydroxide and extract the medium with ethyl acetate. Concentrate the ethyl acetate to a residue in vacuo. Dissolve the residue in a chloroform-methanol mixture (9 parts by volume to 1 part by volume) and add to a silicic acid column. Elute the column with a mixture of chloroform and methanol (8 parts by volume to 2 parts by volume). Collect 5 ml fractions and sample each fraction. Disc test a portion of each sample against S. aureus and chromatograph a second portion of each sample on a Uniplate.RTM.. Combine the fractions having similar R.sub.f values. Those containing rosaramicin have an R.sub.f of about 0.4 to about 0.5. Combine these fractions, concentrate to a residue in vacuo. Dissolve the residue consisting substantially of rosaramicin assaying about 1000 mcg/mg having the following constants:

[.alpha.].sub.D.sup.25 =-33.4.degree. (C=0.3% ethanol)

E.sub.1.spsb.cm.sup.1% =238 (240 m.mu.)

Add 500 mg of rosaramicin to 13 ml of water. Add 130 mg of potassium dihydrogen phosphate and stir at room temperature for 2 hours. Add about 50 mg of decolorizing charcoal and stir for an additional 15 minutes. Filter the solution and lyophilize to obtain the title product, m.p. 118.degree.-121.degree. [.alpha.].sub.D.sup.20 =-21.2.degree. (C=0.3% water).

By utilizing substantially the procedure of this example and by substituting equivalent quantities of acids having substantial solubility in water such as hydrochloric, sulfuric, phosphoric, acetic, succinic, citric, lactic, malic, malonic, maleic and the like, their respective (non-toxic) acid addition salts may be prepared. Generally, such salts exhibit in vitro and in vivo antibacterial spectra that are quite similar, if not identical, to that of the free nitrogen base. Where differences do appear, they are usually attributable to difference in solubility. For example, by virtue of their solubility in aqueous media, the foregoing salts are particularly well suited for utilization in aqueous preparations and solutions for oral and parenteral administration.

Dissolve 1 gm of rosaramicin in 50 ml of diethyl ether; add a solution of 250 mg of tartaric acid in 1.5 ml of ethanol. Stir the resulting mixture for about 15 minutes, then filter the precipitated salt. Wash the precipitate with diethyl ether; dry the precipitate and obtain thereby the title product, m.p. 129.degree.-134.degree. C., [.alpha.].sub.D.sup.20 =-12.degree. (C=0.3% water).

By utilizing substantially the procedure of this example and by substituting equivalent quantities of acids having substantial solubility in ether-alcohol mixtures such as glutaric, lauric, adamantoic, cinnamic, camphoric, palmitic, stearic, undecylenic and the like, their respective (non-toxic) acid addition salts may be prepared. Generally, due to their molecular weight and solubility characteristics, these salts are particularly well suited for utilization in topical preparations such as creams and ointments.

Dissolve 1.0 gm of rosaramicin in 10 ml of dry acetone and add 0.17 ml of acetic anhydride. Stir the mixture at room temperature for 4 hours, then slowly and with stirring add 1.2% ammonium hydroxide solution to precipitate the product. Filter the resulting precipitate, wash with dilute aqueous acetone, with water and dry. Crystallize from aqueous acetone to obtain the desired product, m.p. 112.degree.-116.degree. [.alpha.].sub.D.sup.20 =-25.degree. (C=0.3% ethanol).

Dissolve 2.0 gm of rosaramicin in 10.0 ml of dry acetone and add 0.65 ml of isovaleric anhydride. Stir the mixture at room temperature for 16 hours, then slowly and with stirring add 1.2% ammonium hydroxide solution to precipitate the product. Filter the resulting precipitate, wash with dilute aqueous acetone, with water and dry. Crystallize from aqueous acetone to obtain the title product.

Dissove 3.7 gm of rosaramicin in 20 ml of acetone and add 2.5 gm of stearoyl chloride and 1.7 gm of sodium bicarbonate. Stir the mixture at room temperature for four days, then filter and concentrate the filtrate to a residue under reduced pressure. Purify the residue comprising the crude desired product by chromatography on silica gel. Elute the product with chloroform, combine fractions containing the pure product and concentrate to a residue of rosaramicin 2'-stearate, [.alpha.].sub.D =-16.degree. (C=0.3% ethanol), .lambda..sub.max.sup.MeOH 235 nm (.epsilon. 14,700) bioassay 585 mcg/mg.

By substituting an equivalent quantity of other acylating agents for those used in Examples 8, 9 and 10 above and by following the procedures of said Examples, other monoesters of rosaramicin may be obtained.

Dissolve 50.0 gm of rosaramicin in 700 ml of acetone and add 13.1 gm of propionic anhydride (1.2 m/m). Stir at room temperature for 26 hours, then evaporate the solvent under reduced pressure and triturate the residue with dilute ammonium hydroxide solution for approximately 10 minutes. Collect the residue by filtration and wash with distilled water. Re-triturate the precipitate with distilled water for approximately 10 minutes and then collect the residue by filtration and wash with distilled water. Dry the product at 45.degree. C. and reduced pressure for 24 hours, m.p. 128.degree.-130.degree. C., [.alpha.].sub.D =-24.2.degree. (C=0.3% ethanol).

Dissolve 5.0 gm of rosaramicin in 50 ml of pyridine; add 2.5 ml of acetic anhydride and hold the resulting solution at room temperature for about 4 days. Concentrate the pyridine solution in vacuo to a residue, keeping the temperature at about 35.degree. C. Dissolve the residue in acetone and dilute the solution with 5% ammonium hydroxide to yield the product of this example as a suspension. Filter the suspension and wash with water. Crystallize the product from aqueous acetone to obtain the title product, m.p. 104.degree.-107.degree. C. [.alpha.].sub.D.sup.20 =-24.degree. (C=0.3% ethanol).

Dissolve 250 mg of rosaramicin in 5 ml of pyridine and add 0.25 ml of benzoyl chloride with stirring. Keep the solution at room temperature for 5 days, then concentrate in vacuo to about 1 ml and dilute with about 5 ml of acetone. Add 5% ammonium hydroxide until the product precipitates. Filter the suspension, wash the precipitate with water and dry to obtain rosaramicin dibenzoate.

By substituting an equivalent quantity of other acylating agents for those used in Examples 12 and 13 above and by following the procedures of said Examples, other 3,2'-diesters of rosaramicin may be obtained. Exemplary of such esters are those derived from acids such as propionic, butyric, valeric, hexanoic, stearic, cyclopropyl carboxylic, adamantane carboxylic, pivalic, phenylacetic, phenoxyacetic, phosphoric, alkyl, aryl and aralkyl sulfonic acids, the aryl and aralkyl sulfonic acids optionally bearing substituents such as halogeno, nitro, lower alkoxy and the like on the benzenoic moiety. Also included among such esters are hemi-esters derived from di-carboxylic acids such as succinic, maleic, fumaric, malonic and phthalic acids.

By preparing a particular monoester of rosaramicin and by subjecting the monoester to the action of a different acylating agent, one may prepare a mixed diester such as those set forth in Examples 14 and 16, which mixed diesters are within the scope of the term "3,2'-diesters" as used herein.

Preferred non-toxic pharmaceutically acceptable 2'-monoesters and 3,2'-diesters of rosaramicin are esters of hydrocarbon carboxylic acids of 2-18 carbon atoms, preferably alkanoic acids of 2-6 carbon atoms. Other esters, in addition to the above-identified preferred class of esters are those of inorganic acids such as, sulfuric and phosphoric acids; and of organic acids including alicyclic, cycloaliphatic, aryl and heterocyclic carboxylic sulfonic and carbonic acids of 2-18 carbon atoms.

Stir a solution in 623 mg of rosaramicin 2'-acetate and 0.5 ml of valeric anhydride in 10 ml of pyridine at room temperature for 24 hours. Concentrate to a residue under reduced pressure and triturate the residue with ammonium hydroxide. Extract the resulting mixture with ethyl acetate and wash the extracts with sodium bicarbonate and water. Concentrate the organic solution to a residue of the desired compound, m.p. 85.degree.-86.degree. C., mass spectrum M.sup.+ 707.

Dissolve 1.0 gm of rosaramicin in 12 ml of pyridine and add 1.7 ml of propionic anhydride. Stir the mixture at room temperature for 5 days, then concentrate to a residue under reduced pressure. Triturate the residue with 5% aqueous ammonium hydroxide and isolate the resulting solid by filtration. Purify by filtration through a column of silica gel, using chloroform as the solvent-eluant. Combine fractions containing the desired compound on the basis of thin layer chromatography, and concentrate to a solid comprising the desired dipropionate, m.p. 85.degree.-87.degree. C., [.alpha.].sub.D =-18.degree. (ethanol) .lambda..sub.max.sup.MeOH 240 m.mu. (.epsilon. 14,000).

Stir a solution of 300 mg of rosaramicin 2'-acetate and 0.5 ml of benzoyl chloride in 10 ml of pyridine at room temperature for 48 hours. Concentrate the solution to a residue under reduced pressure and triturate with ammonium hydroxide. Dissolve the solids in ethyl acetate, wash with sodium bicarbonate solution and with saturated sodium chloride and dry over sodium sulfate. Concentrate under reduced pressure to a residue of the desired compound, m.p. 76.degree.-78.degree. C., [.alpha.].sub.D =-12.degree. (C=0.3% ethanol).

The 3-monoesters of rosaramicin are prepared from the 3,2'-diesters substantially as set forth in Examples 17 through 20, inclusive.

Stir a solution of 625 mg of the product of Example 14 in 20 ml of 75% aqueous methanol at room temperature for 4 hours. Replace the solvent with ethyl acetate, wash with sodium bicarbonate and concentrate to a residue of the compound of this example, m.p. 104.degree.-105.degree., [.alpha.].sub.D =-39.degree. (C=0.3% ethanol).

Dissolve 35 mg of the product of Example 15 in 0.5 ml of 92% aqueous methanol and allow the solution to stand at room temperature for 18 hours. Concentrate the solution under reduced pressure to give a residue comprising the compound of this example, m.p. 93.degree.-95.degree..

Alternatively, dissolve 20 mg of the product of Example 15 in a mixture of 0.5 ml of methanol and 0.5 ml of 5% ammonium hydroxide solution. Allow to stand at room temperature for 3 hours, then concentrate under reduced pressure to a residue consisting substantially of the compound of this example.

Dissolve 185 mg of the product of Example 12 in 8.0 ml of 80% aqueous methanol and keep at room temperature for 4 hours. Concentrate to a residue, dissolve the latter in chloroform, filter through 1.5 gm of silica gel and concentrate to a residue under reduced pressure. Dissolve the residue in chloroform and crystallize from chloroform-hexane to obtain the compound of this example as a chloroform solvate, m.p. 108.degree.-110.degree.. Recrystallize from chloroform-hexane and dry in vacuo at 60.degree. to obtain the solvent-free compound, m.p. 145.degree.-147.degree., .lambda..sub.max.sup.MeOH 239 m.mu. (.epsilon. 14,000).

Keep a solution of 40 mg of the product of Example 13 in 1 ml of 80% aqueous methanol at room temperature for 40 hours. Concentrate to a residue under reduced pressure. Dissolve the residue in methanol and pour onto ice water. Isolate the resulting precipitate by filtration, wash with water and dry to obtain the compound of this example, m.p. 111.degree.-115.degree., mass spectrum M.sup.+ 685.

Alternatively, prepare the compound of this example in the following manner:

Stir a solution of 160 mg of the product of Example 16 in 10 ml of 75% aqueous methanol at room temperature for 4 hours. Replace the solvent with ethyl acetate, wash with water, dry and concentrate to obtain rosaramicin 3-benzoate identical to material prepared above.

The following examples set forth methods for preparing acid addition salts of rosaramicin esters. These compounds, like the esters from which they are prepared, exhibit substantial antibacterial activity.

Add 319 mg of rosaramicin 2'-propionate to a solution of 49 mg of phosphoric acid in 5 ml of water and stir the mixture at room temperature for five minutes. Filter the solution and lyophilize the filtrate to obtain a residue of the desired phosphate salt, [.alpha.].sub.D =-22.degree. (C=0.3% water), .lambda..sub.max.sup.MeOH 240 nm (.epsilon. 13,600), bioassay 915 mcg/mg.

Dissolve 4.0 gm of rosaramicin 2'-propionate in 40 ml of acetone and add a solution of 1.8 gm of sodium dodecylsulfate in 30 ml of water. Add 0.4 ml of acetic acid and stir the mixture for five minutes. Concentrate to about 20 ml under reduced pressure, add about 50 ml of water and refrigerate for 16 hours. Decant the supernatant liquid and triturate the residue with hexane. Remove the hexane by decantation, dissolve the residue in ethanol and concentrate the solution to dryness under reduced pressure, to obtain a residue of the desired salt, .lambda..sub.max.sup.MeOH 240 nm (.epsilon. 14,000), bioassay 721 mcg/mg.

The following examples are directed to some of the plurality of dosage forms wherein rosaramicin its non-toxic acid addition salts and esters may be employed. The formulations, excluding the topicals, are designed to permit the administration of from about 5 to about 50 mg of antibiotic (as the free base) per kilogram of body weight per day. It is expected that the medicaments be administered up to about 8 times in a 24 hour period. The topical formulations are generally applied to the infected area from about 2 to about 4 times daily. It should be noted, however, that the size of the dosage administered and the frequency thereof depend to a great extent upon the type of infection, its severity and the individual characteristics of the animal species being treated.

Dissolve 5.1 gm of rosaramicin in 70 ml of acetone and add 1.65 ml of butyric anhydride. Stir the reaction mixture at room temperature for 27 hours and isolate the product as described in Example 11 to obtain the compound of this example, m.p. 106.degree.-112.degree. C., [.alpha.].sub.D.sup.26 =-24.2.degree. (C=0.3% ethanol).

As previously indicated hereinabove, the antibiotics of this invention have in vitro and in vivo utility. And for in vivo application may be administered topically, orally or parenterally, preferably in admixture with suitable pharmaceutical excipients. Although the precise dose to be administered in any given dosage form depends upon many factors such as the stage and severity of the infection, the susceptibility of the infecting organism to the antibiotic and the individual characteristics of the mammalian species being treated, it is generally preferred that the antibiotic be administered at from about 5 mg to about 20 mg per kilogram of body weight per day divided into 2 to 4 equal doses. Where warranted larger or smaller doses may be administered, the precise regimen to be followed being left to the discretion of the practitioner.