Antibiotic GE 2270 factors A1, A2, A3 and H

Abstract: The present invention is directed to new antibiotic substances denominated antibiotic GE 2270 factors A₁, A₂, A₃ and H, the addition salts thereof, the pharmaceutical compositions thereof and their use as medicaments, particularly in the treatment of infectious diseases involving microorganisms susceptible to them.

Description: The present invention is directed to new antibiotic substances denominated antibiotic GE 2270 factors A₁, A₂, A₃ and H, the addition salts thereof, the pharmaceutical compositions thereof and their use as medicaments, particularly in the treatment of infectious diseases involving microorganisms susceptible to them. The compounds of the invention are also active as growth promotant agents in animals, such as poultry, swine, ruminants, etc. Another object of this invention is a process for preparing antibiotic GE 2270 factors A₁, A₂, A₃ or H by selective transformation of antibiotic GE 2270 factor A. This substance is, in turn, prepared by culturing a sample of Planobispora rosea ATCC 53773 or a producing variant or mutant thereof and isolating the desired antibiotic substance from the mycelium and/or the fermentation broth. Planobispora rosea ATCC 53773 was isolated from a soil sample and deposited on June 14, 1988 with the American Type Culture Collection (ATCC), 12301 Parklawn Drive, Rockville, MD 20852 Maryland, U.S.A., under the provisions of the Budapest Treaty. The strain has been accorded accession number ATCC 53773. Antibiotic GE 2270 factor A and Planobispora rosea ATCC 53773 are described in European Patent application Publication No. 359062. In view of the similarities between the antimicrobial activity of antibiotic GE 2270 factor A₁, A₂, A₃ and H and the corresponding pharmaceutically acceptable salts, when available, in the present application when dealing with the biological properties of antibiotic GE 2270 factors A₁, A₂, A₃ or H, also the corresponding salts are included and vice versa, when dealing with the biological properties of a pharmaceutically acceptable addition salt of antibiotic GE 2270 factor A₁, A₂, A₃ or H, also the corresponding "non-addition salt" form is encompassed. In particular, antibiotic GE 2270 factor A₃ can form base addition salts according to the usual procedures. Representative examples of these bases are: alkali metal of alkaline-earth metal hydroxides such as sodium, potassium, calcium, magnesium, and barium hydroxide; ammonia and aliphatic, alicyclic or aromatic organic amines such as methylamine, dimethylamine, trimethylamine, and picoline. Also the salts with basic aminoacids or derivatives thereof such as arginine, lysine or ornithine are encompassed by the present definition of base addition salts. The transformation of the "non-salt" compounds of the invention into the corresponding addition salts, and the reverse, i.e. the transformation of an addition salt of a compound of the invention into the non-salt form, are within the ordinary technical skill and are encompassed by the present invention. A base addition salt of antibiotic GE 2270 factor A₃ can be prepared for instance by dissolving or suspending the non-salt form in an aqueous solvent and adding a slight molar excess of the selected base. The resulting solution or suspension is then lyophilized to recover the desired salt. In case the final salt is unsoluble in a solvent where the non-salt form is soluble, it is recovered by filtration from the organic solution of the non-salt form after addition of the stoichiometric amount or a slight molar excess of the selected base. The non-salt form can be prepared from a corresponding base salt dissolved in an aqueous solvent which is then neutralized to free the non-salt form. When following the neutralization the elimination of the excess of acid or base is necessary, a common desalting procedure may be employed. For example, column chromatography on silanized silica gel, non-functionalized polystyrene, acrylic and controlled pore polydextrane resins (such as Sephadex® LH 20) or activated carbon may be conveniently used. After eluting the undesired salts with an aqueous solution, the desired product is eluted by means of a linear gradient or a step-gradient of a mixture of water and a polar or apolar organic solvent, such as acetonitrile/water from 50:50 to about 100% acetonitrile. The compounds of the invention are prepared from antibiotic GE 2270 factor A under selective chemical transformation conditions. More particularly, antibiotic GE 2270 factors A₁, A₂ and A₃ are prepared from antibiotic GE 2270 factor A under selective hydrolytic conditions, while by selective cleavage under reducing conditions antibiotic GE 2270 factor H is obtained from antibiotic GE 2270 factor A. Generally, the above mentioned hydrolytic conditions involve the use of mixtures of buffered or unbuffered aqueous acid media and polar organic solvents. The reaction temperature varies depending on such factors as the strength and the concentration of the acid employed, and is generally comprised between -10°C and 90°C. Also the reaction time varies considerably depending on the other parameters such as temperature and acid strength and concentration; generally it may vary from a few minutes to several hours. In general, when milder hydrolysis conditions are employed, e.g. shorter time and lower temperature or lower acid strength or concentration, antibiotic GE 2270 factor A₁ is normally obtained, while under stronger conditions antibiotic GE 2270 factor A₂ is obtained. To obtain antibiotic GE 2270 factor A₃ under acid hydrolytic conditions still more drastic conditions are necessary. However, since the reaction course can be monitored according to the usual procedures, e.g. TLC or HPLC, by following the disappearance of the starting material and/or appearance of the final products, the skilled technician is capable of deciding when the reaction can be considered as complete and the recovery procedure may be started. Examples of buffered or unbuffered aqueous acidic media are aqueous solutions or suspensions of mineral or organic acids such as hydrogen halides, e.g. hydrogen chloride, bromide or iodide; phosphoric acids; sulfuric acid; (C₁-C₆)aliphatic, halogenated(C₂-C₅)aliphatic or arylic acids; (C₂-C₆)alkylsulfonic or arylsulfonic acids; cationic exchange resins in the acid form, and the products of partial salification of polyprotonic acids, i.e., salts having acidic reaction in water, e.g. an alkali-metal hydrogen phosphate or dihydrogen phosphate, alkali metal hydrogen sulfate and the like. Examples of alkali-metals are sodium and potassium. Representative examples of the (C₁-C₆)aliphatic acids mentioned above are formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, trimethylacetic acid, and the like. Representative examples of the halogenated(C₂-C₅)aliphatic acids mentioned above are mono- or poly- chloro, bromo or iodo aliphatic acids such as fluoroacetic acid, chloroacetic acid, difluoroacetic acid, dichloroacetic acid, trifluoroacetic acid, trichloroacetic acid, pentafluoropropionic acid, 2,2,3,4,4,4-hexafluorobutyric acid, heptafluorobutyric acid, and the like. Representative examples of arylic acids are benzoic acid and mono- or poly- substituted benzoic acids such as chlorobenzoic acid, methylbenzoic acid, phthalic acid, terephthalic acid, benzylacetic acid and the like. Representative examples of the sulfonic acids mentioned above are: methanesulfonic acid, trifluoromethanesulfonic acid, p-toluenesulfonic acid, cyclohexanesulfonic acid, camphorsulfonic acid, alpha- and beta-naphthalenesulfonic acid. The "cationic exchange resins" mentioned above are commonly known and commercially available resins such as sulfonated styrenic and styrene-divinyl benzenic resins in the acid form. Suitable organic solvents as mentioned above are such that : a) they may at least partially solubilize the starting materials; b) the products, once obtained, either separate or may be separated according to usual techniques, and c) in any case, they do not unfavorably interfere with the reaction course. Examples of said organic polar solvents are cyclic oxygen containing aliphatic solvents such as dioxane (i.e.diethylenedioxide), tetrahydrofuran and the like; lower alkanols; phenyl substituted lower alkanols; lower alkyl carboxamides; lower alkyl sulfoxamides; lower alkyl phosphoramides; lower alkyl sulfoxides and lower alkyl sulfones, and the like, and mixtures thereof. The term "lower alkyl" as used above, represents preferably alkyl groups of 1 to 6 carbon atoms. Examples of lower alkanols are C₁-C₆ alkanols such as methanol, ethanol, propanol, 1-methylethanol, butanol and 2-methylpropanol. Examples of phenyl substituted lower alkanols are the following: benzyl alcohol, m-chlorobenzyl alcohol, o-fluorobenzyl alcohol, m-fluorobenzyl alcohol, p-fluorobenzyl alcohol, m-methylbenzyl alcohol, m-methoxybenzyl alcohol, o-ethoxybenzyl alcohol, m-butoxybenzyl alcohol, p-tert.butoxybenzyl alcohol, p-tert.butylbenzyl alcohol, phenethyl alcohol, o-chlorophenethyl alcohol, m-chlorophenetyl alcohol, o-methoxyphenethyl alcohol, m-methoxyphenethyl alcohol, o-propylphenethyl alcohol, o-ethoxyphenethyl alcohol, p-fluorophenethyl alcohol, p-bromophenethyl alcohol, o-propoxyphenethyl alcohol, o-butoxyphenethyl alcohol, 1-(p-isopropylphenyl)ethanol, 3-phenyl-1-propanol, 2-phenyl-1-propanol, 4-phenyl-1-butanol and 3-phenyl-1-butanol. Examples of lower alkyl carboxamides are dimethylformamide, diethylformamide and the like. A preferred lower alkyl sulfoxide is dimethyl sulfoxide, a preferred lower alkyl sulfone is dimethylsulfone and a preferred lower alkyl phosphoramide is hexamethyl phosphoramide. A preferred embodiment of the invention is represented by a process for preparing antibiotic GE 2270 factor A₁ which comprises contacting antibiotic GE 2270 factor A with a buffered or unbuffered acid medium in the presence of a polar organic solvent at a temperature between -10°C and 50°C, and preferably between 4°C and 25°C. The reaction time, which varies considerably depending on the other specific reaction parameters, is, in this case, generally between 5 min and 16 h. Another preferred embodiment of the invention is represented by a process for preparing antibiotic GE 2270 factor A₂ which comprises contacting antibiotic GE 2270 factor A or factor A₁ with a buffered or unbuffered acid medium in the presence of a polar organic solvent at a temperature between 40°C and 90°C, and preferably between 50°C and 70°C. The reaction time, which varies considerably depending on the other specific reaction parameters, is, in this case, generally between 12 h and 24 h. In the case of the conversion of factor A₁ into factor A₂ under the above conditions, it appears that ammonia is lost by the molecule of the starting material. A further preferred embodiment of the invention is represented by a process for preparing antibiotic GE 2270 factor A₃ which comprises contacting antibiotic GE 2270 factor A with a buffered or unbuffered acid medium in the presence of a polar organic solvent at a temperature between 40°C and 90°C, and preferably between 65°C and 80°C. The reaction time, which varies considerably depending on the other specific reaction parameters, is, in this case, generally between 8 h and 48 h. In this case however, the conversion yields are generally low (5-15% molar yield) even by using strong reaction conditions. A preferred method for preparing antibiotic GE 2270 factor A₃ with acceptable yields and purity is represented by the treatment of antibiotic GE 2270 factor A₂ under basic hydrolytic conditions in the presence of polar organic solvents. Examples of polar organic solvents are as reported above, while the basic conditions can be imparted by any aqueous basic solution or suspension. Examples of base that can conveniently be employed are inorganic or organic bases such as alkali-metal or earth-metal hydroxides; salts having basic reaction in water such as alkali-metal carbonates or bicarbonates; ammonia and aliphatic or aromatic amines such as alkyl amines (e.g. dimethylamine, diethylamine, triethylamine, trimethylamine) and picolines. Examples of alkali-earth metals are calcium and magnesium. The following specific reaction conditions are given simply to further illustrate the process of the invention. In the following tables: "R.T." means "room temperature" i.e. approximately 15°C-25°C "EtOH" means "ethanol" "TFA" means "trifluoroacetic acid" "AcOH" means "acetic acid" "Dowex" 50Wx2 (H+) is a cation exchange resin in the acid form "TEA" means "triethylamine". Specifically preferred reaction conditions for the preparation of antibiotic GE 2270 factor A₁ from factor A are the following: Temperature °C Time Acid medium Polar solvent R.T. 5 min 0.2 M HCl EtOH/H₂O 9/1 R.T. 15 min TFA/H₂O/Dioxane 1/4/5 R.T. 15 min 0.5 N H₂SO₄ Dioxane/H₂O 1/1 R.T. 15 min 0.25 M H₃PO₄ Dioxane/H₂O 1/1 50 overnight 0.5 M NH₄Cl Dioxane/H₂O 1/1 Specifically preferred reaction conditions for the preparation of antibiotic GE 2270 factor A₂ from factor A or A₁ or a mixture thereof are the following: Temperature °C Time Acid medium Polar solvent 60°C 24 h AcOH/EtOH (95%) 80°C overnight AcOH/H₂O, 1,1 50°C overnight TFA/H₂O/Dioxane 1/4/5 50°C overnight 0.25 M H₃PO₄ Dioxane/H₂O 1/1 50°C overnight 0.5 M NH₄Cl Dioxane/H₂O 1/1 50°C overnight Dowex 50Wx2 (H+) Dioxane/H₂O 1/1 50°C overnight p.toluene-sulfonic acid Dioxane/H₂O 1/1 Specifically preferred reaction conditions for the preparation of antibiotic GE 2270 factor A₃ from factor A₂ are the following: Temperature °C Time Acid medium Polar solvent R.T. 15 min NaOH Dioxane/H₂O 1/1 R.T. 1 h 0.5 M Na₂CO₃ Dioxane/H₂O 1/1 R.T. overnight 0.5 M NaHCO₃ Dioxane/H₂O 1/1 R.T. overnight 0.5 M TEA Dioxane/H₂O 1/1 80°C 1 h 0.5 M NaHCO₃ Dioxane/H₂O 1/1 80°C 1 h 0.5 M TEA Dioxane/H₂O 1/1 Specifically preferred reaction conditions for the preparation of antibiotic GE 2270 factor A₃ from factor A are the following: Temperature °C Time Acid medium Polar solvent 50°C overnight TFA/H₂O/dioxane 70°C overnight Dowex 50Wx2 (H+) Dioxane/H₂O 1/1 70°C overnight 0.5 N H₂SO₄ Dioxane/H₂O 1/1 Antibiotic GE 2270 factor H is prepared from antibiotic GE 2270 factor A by controlled cleavage under reducing conditions. Preferred reducing conditions are given by alkali metal borohydrides, such as sodium or potassium borohydride, in a compatible polar organic solvent, such as one of those indicated above. A preferred solvent is aqueous tetrahydrofuran and a preferred borohydride is sodium borohydride. The compounds of the invention are recovered at the end of the preparation process according to known per se techniques which includes extraction with solvents, precipitation by means of precipitating agents, by changing the pH, and/or by concentration, and chromatographic techniques such as partition chromatography, reverse-phase partition chromatography, ion-exchange, molecular exclusion chromatography, preparative HPLC and the like. Physico-chemical characteristics of antibiotic GE 2270 factor A ₁: A) ultraviolet absorption spectrum, which is shown in Figure 1 of the accompanying drawings, and exhibits the following absorption maxima: Lambda max (nm) 0.1 M HCl about 240 (shoulder) 310 O.1 M KOH about 245 (shoulder) 311 Phosphate buffer pH 7.4 about 245 (shoulder) 310 Methanol about 215 (shoulder) about 240 (shoulder) 309 B) infrared absorption spectrum in nujol mull which is shown in Figure 2 of the accompanying drawings and exhibits the following absorption maxima (cm⁻¹): 3700-3000; 3000-2800 (nujol); 1650; 1535; 1505; 1460 (nujol); 1375 (nujol) ; 1310; 1240; 1190; 1165; 1130-1000; 980; 930; 840; 805; 750; 720 (nujol) ; 700; C) ¹H-NMR spectrum which is shown in Figure 3 and exhibits the following groups of signals at 500 MHz recorded in DMSO-d₆ (hexadeuterodimethylsulfoxide) using TMS as the internal standard (0.00 ppm); the multiplicity for each signal is also reported below (s=singlet; d=doublet; m=multiplet; dd=doublet of doublets; br s=broad singlet): 0.84, d; 0.87, d; 1.35, m; 1.91, m; 2.08, m; 2.16, m; 2.46, d; 2.58, s; 2.70, dd; 3.38, s; 3.76, m; 3.84, m; 4.26, dd; 4.33, m; 4.89, m; 4.97, s; 5.00, dd; 5.20, dd; 5.22, dd; 5.28 (2 protons), m; 6.01, d; 7.07, s; 7.2, s; 7.34, s; 7.22-7.38 (6 protons), m; 8.29, s; 8.39, d; 8.44, m; 8.45, d; 8.54, s; 8.60, s; 8.66, d; 9.69, d; 8.99, d; D) retention-time (R t ) of 13.4 min when analyzed by reverse phase HPLC under the following conditions: column: Ultrasphere ODS (reverse phase silanized silica gel; 5 micrometer) Altex (Beckman) 4.6 mm (i.d.) x 250 mm pre-column: Brownlee Labs RP 18 (octadecylsilane silica gel; 5 micrometer) eluent A: acetonitrile:18mM NaH₂PO₄, 70:30 (v/v), adjusted to pH 7.0 eluent B: acetonitrile:18mM NaH₂PO₄ 10:90 (v/v), adjusted to pH 7.0 elution mode: linear gradient of eluent A in eluent B from 45% to 70% in 20 min flow rate: 1.8 ml/min U.V. detector: 254 nm internal standard: Chloramphenicol (R t = 3.6 min) E) elemental analysis, after the sample has been previously dried at about 140°C under inert atmosphere, which indicated the following composition: carbon, hydrogen, nitrogen, sulfur; F) FAB-MS analysis showing the low mass isotope of the protonated molecular ion at m/z 1308 mass units; all the other peaks above 800 m/z mass units in the spectrum, not counting isotope peaks, were lower than 20% of the molecular ion, upon analysis with a Kratos MS-50 double focusing mass spectrometer under the following experimental conditions: Xe fast atom bombardment at 6 Kv; 0.6 mA discharge current; glycerol matrix; positive ionization mode Physico-chemical characteristics of antibiotic GE 2270 factor A ₂: A) ultraviolet absorption spectrum, which is shown in Figure 4 of the accompanying drawings, and exhibits the following absorption maxima: Lambda max (nm) 0.1 M HCl about 245 (shoulder) 309 O.1 M KOH about 245 (shoulder) 309 Phosphate buffer pH 7.4 about 245 (shoulder) 309 Methanol about 215 (shoulder) about 242 (shoulder) 306 B) infrared absorption spectrum in nujol mull which is shown in Figure 5 of the accompanying drawings and exhibits the following absorption maxima (cm⁻¹): 3700-3000; 3000-2800 (nujol); 1725; 1655; 1590-1480; 1460 (nujol); 1410; 1375 (nujol); 1335; 1305; 1265-1130; 1090; 1050; 1015; 980; 945; 930; 840; 805; 745; 720 (nujol); 700; C) ¹H-NMR spectrum which is shown in Figure 6 and exhibits the following groups of signals at 500 MHz recorded in DMSO-d₆(hexadeuterodimethylsulfoxide) using TMS as the internal standard (0.00 ppm); the multiplicity for each signal is reported below (s=singlet; d=doublet; m=multiplet; dd=doublet of doublets; br s=broad singlet): 0.83, d; 0.86, d; 1.30, m; 1.82, m;; 1.90, m; 2.17, m; 2.46, d; 2.57, s; 2.70, dd; 3.37, s; 3.40, m; 3.48, m; 3.77, dd; 4.24, m; 4.28, dd; 4.52, d; 4.53, br s; 4.67, d; 4.96, s; 4.98, dd; 5.19, m; 5.21, m; 5.28, m; 6.01, d; 7.34, s; 7.22-7.35, m; 8.26, d; 8.28, s; 8.42, d; 8.45, s; 8.59, s; 8.67 (2 protons), d; 8.73, s; 9.00, d; D) retention-time (R t ) of 17.0 min when analyzed by reverse phase HPLC under the following conditions: column: Ultrasphere ODS (reverse phase silanized silica gel; 5 micrometer) Altex (Beckman) 4.6 mm (i.d.) x 250 mm pre-column: Brownlee Labs RP 18 (octadecylsilane silica gel; 5 micrometer) eluent A: acetonitrile:18mM NaH₂PO₄, 70:30 (v/v), adjusted to pH 7.0 eluent B: acetonitrile:18mM NaH₂PO₄ 10:90 (v/v), adjusted to pH 7.0 elution mode: linear gradient of eluent A in eluent B from 45% to 70% in 20 min flow rate: 1.8 ml/min U.V. detector: 254 nm internal standard: Chloramphenicol (R t = 3.6 min) E) elemental analysis, after the sample has been previously dried at about 140°C under inert atmosphere, which indicated the following composition: carbon, hydrogen, nitrogen, sulfur; F) FAB-MS analysis showing the low mass isotope of the protonated molecular ion at m/z 1291 mass units; all the other peaks above 800 m/z mass units in the spectrum, not counting isotope peaks, were lower than 20% of the molecular ion, upon analysis with a Kratos MS-50 double focusing mass spectrometer under the following experimental conditions: Xe fast atom bombardment at 6 Kv; 0.6 mA discharge current; glycerol matrix; positive ionization mode Physico-chemical characteristics of antibiotic GE 2270 factor A ₃ A) ultraviolet absorption spectrum, which is shown in Figure 7 of the accompanying drawings, and exhibits the following absorption maxima: Lambda max (nm) O.1 M KOH 240 (shoulder) 309 330 (shoulder) Phosphate buffer pH 7.4 240 (shoulder) 309 330 shoulder Methanol 240 (shoulder) 309 340 (shoulder) B) infrared absorption spectrum in nujol mull which is shown in Figure 8 of the accompanying drawings and exhibits the following absorption maxima (cm⁻¹): 3700-3140; 3110; 3020-2750 (nujol); 1720; 1655; 1590-1520; 1500; 1460 (nujol); 1375 (nujol); 1270-1200; 1130-1030; 1020; 980; 930; 840; 805; 750; 720 (nujol); 700; C) ¹H-NMR spectrum which is shown in Figure 9 and exhibits the following groups of signals (in ppm) at 500 MHz recorded in DMSO-d₆ (hexadeuterodimethylsulfoxide) using TMS as the internal standard (0.00 ppm); the number of protons and multiplicity for each signal is also reported below (s=singlet; d=doublet; m=multiplet; dd=doublet of doublets; br s=broad singlet): 9.02,1H (d); 8.71,1H (d); 8.70,1H (d); 8.65,1H (s); 8.57,1H (s); 8.46,1H (m); 8.38,1H (d); 8.28,1H (d); 8.25,1H (s); 7.38,1H (m); 7.37,1H (s); 7.36-7.20,5H (m); 6.05,1H (br s); 5.31,1H (m); 5.27,1H (dd); 5.20,1H (dd); 5.03,1H (d); 4.99,2H (s); 4.32,1H (dd); 3.82,1H (dd); 3.38,3H (s); 2.74,1H (dd); 2.60,3H (s); 2.49,3H (d); 2.17,1H (m); 1.35,1H (m); 0.88,3H (d); 0.84,3H (d); D) retention-time (R t ) of 7.1 min when analyzed by reverse phase HPLC under the following conditions: column: Ultrasphere ODS (reverse phase silanized silica gel; 5 micrometer) Altex (Beckman) 4.6 mm (i.d.) x 250 mm pre-column: Brownlee Labs RP 18 (octadecylsilane silica gel; 5 micrometer) eluent A: acetonitrile:18mM NaH₂PO₄, 70:30 (v/v), adjusted to pH 7.0 eluent B: acetonitrile:18mM NaH₂PO₄ 10:90 (v/v), adjusted to pH 7.0 elution mode: linear gradient of eluent A in eluent B from 45% to 70% in 20 min flow rate: 1.8 ml/min U.V. detector: 254 nm internal standard: Chloramphenicol (R t = 3.6 min) E) elemental analysis, after the sample has been previously dried at about 140°C under inert atmosphere, which indicated the following composition: carbon 51.27%, hydrogen 4.02%, nitrogen 14.94%, sulfur; F) FAB-MS analysis showing the low mass isotope of the protonated molecular ion at m/z 1125 mass units; all the other peaks above 800 m/z mass units in the spectrum, not counting isotope peaks, were lower than 20% of the molecular ion, upon analysis with a Kratos MS-50 double focusing mass spectrometer under the following experimental conditions: Xe fast atom bombardment at 6 Kv; 0.6 mA discharge current; glycerol matrix; positive ionization mode G) ¹³C-NMR spectrum which is reported in Figure 10 of the accompanying drawings exhibiting the following groups of signals (ppm) at 125 MHz in DMSO-d₆ using TMS as the internal reference (0.00 ppm), 171.2; 169.9; 169.6; 168.5; 167.8; 165.7; 164.8; 162.2; 161.4; 161.3; 160.5; 160.4; 153.5; 150.4; 150.1; 149.5; 149.1; 147.0; 143.8; 142.1; 141.8; 141.4; 141.0; 139.6; 131.8; 128.0 (2 carbons); 127.7; 127.6; 126.9; 126.8 (2 carbons); 123.1; 118.7; 116.4; 73.9; 67.4; 58.7; 58.3; 55.5; 48.2; 41.2; 37.7; 34.1; 25.9; 18.5; 18.0; 12.0; H) a specific optical rotation [α] 20 / D of +182.5 in CHCl₃ + 10% CH₃OH Physico-chemical characteristics of antibiotic GE 2270 f act or H A) ultraviolet absorption spectrum, which is shown in Figure 11 of the accompanying drawings, and exhibits the following absorption maxima: Lambda max (nm) 0.1 M HCl 248 303 O.1 M KOH about 245 (shoulder) 310 Phosphate buffer pH 7.4 about 240 (shoulder) 312 Methanol about 215 (shoulder) about 240 (shoulder) 309 B) infrared absorption spectrum in nujol mull which is shown in Figure 12 of the accompanying drawings and exhibits the following absorption maxima (cm⁻¹): 3700-3000; 3000-2800 (nujol); 1655; 1590-1480; 1460 (nujol); 1375 (nujol); 1310; 1220; 1190; 1130-1000; 980; 930; 840; 820-680; 720 (nujol); 640; C) ¹H-NMR spectrum which is shown in Figure 13 and exhibits the following groups of signals (ppm) at 500 MHz recorded in DMSO-d₆ (hexadeuterodimethylsulfoxide) using TMS as the internal standard (0.00 ppm); the multiplicity for each signal is also reported below (s=singlet; d=doublet; m=multiplet; dd=doublet of doublets; br s=broad singlet): 0.83, d; 0.87 d; 1.30, m; 2.16, m; 2.46, d; 2.58, s; 2.70, dd; 3.38, s; 3.52, m; 3.61, m; 3.77, dd; 4.25, m; 4.30, m; 4.35, m; 4.47, m; 4.88, m; 4.97, s; 4.99, dd; 5.20, m; 5.23, m; 5.28, m; 6.02, d; 7.36, s; 7.22-7.40, m; 8.26, d; 8.28, s; 8.42, d; 8.43, m; 8.47, s; 8.60, s; 8.67, d; 9.02, d; D) retention-time (R t ) of 18.0 min when analyzed by reverse phase HPLC under the following conditions: column: Ultrasphere ODS (reverse phase silanized silica gel; 5 micrometer) Altex (Beckman) 4.6 mm (i.d.) x 250 mm pre-column: Brownlee Labs RP 18 (octadecylsilane silica gel; 5 micrometer) eluent A: acetonitrile:18mM NaH₂PO₄, 70:30 (v/v), adjusted to pH 7.0 eluent B: acetonitrile:18mM NaH₂PO₄ 10:90 (v/v), adjusted to pH 7.0 elution mode: linear gradient of eluent A in eluent B from 45% to 70% in 20 min flow rate: 1.8 ml/min U.V. detector: 254 nm internal standard: Chloramphenicol (R t = 3.6 min) E) elemental analysis, after the sample has been previously dried at about 140°C under inert atmosphere, which indicated the following composition: carbon, hydrogen, nitrogen, sulfur; F) FAB-MS analysis showing the low mass isotope of the protonated molecular ion at m/z 1180 mass units; all the other peaks above 800 m/z mass units (not counting isotope peaks) in the spectrum were lower than 20% of the molecular ion, upon analysis with a Kratos MS-50 double focusing mass spectrometer under the following experimental conditions: Xe fast atom bombardment at 6 Kv; 0.6 mA discharge current; glycerol matrix; positive ionization mode. The antimicrobial activity of the compounds of the invention can be demonstrated by a series of standard tests in vitro. MIC for Clostridium difficile , Propionibacterium acnes , and Bacteroides fragilis are determined by agar dilution (inocula 10⁴/10⁵ CFU/spot). MIC for other organisms are determined by microbroth dilution (inocula 10⁴ to 10⁵ CFU/ml). Incubation times are 18-24 h, except for Neisseria gonorrhoeae , Branhamella catarrhalis , Haemophilus influenzae , C . difficile , P . acnes , B . fragilis (48h). All organisms are incubated at 37°C. N . gonorrhoeae and H . influenzae are incubated in a 5% CO₂ atmosphere, anaerobes in an anaerobic gas mixture. Media used are: Iso-Sensitest broth (Oxoid) ( Staphylococci , Streptococcus faecalis , Escherichia coli , Pseudomonas aeruginosa , Proteus vulgaris , Klebsiella pneumoniae ); Todd-Hewitt broth (Difco) (other streptococci); Mueller Hinton broth (BBL) ( Branhamella catarrhalis ); GC base broth (Difco) + 1% IsoVitalex (BBL) ( N . gonorrhoeae ); brain heart infusion broth (Difco) + 1% Supplement C (Difco) ( H . influenzae ); AC medium (Difco) ( C . perfringens ); Wilkins-Chalgren agar (Difco) (other anaerobes) (T.D. Wilkins and S. Chalgren, Antimicrob. Ag. Chemother. 10, 926, 1976). Chlamydia trachomatis was cultivated in microtiter plates on cycloheximide treated McCoy cell monolayers, in Eagle's MEM medium (Gibco) with 10% fetal calf serum, in a 5% CO₂ atmosphere. Inocula were prepared so as to give 30 - 60 inclusions per 300X microscope field. After 48 h, chlamydial inclusions were stained with fluorescein-labeled monoclonal antibody to the major outer membrane protein (Syva) and counted by fluorescence microscopy. The MIC was taken as the concentration at which inclusions were no longer seen and cellular morphology was normal. The minimal inhibitory concentrations (MIC, microgram/ml) for some microorganisms are reported below in Table I. The antimicrobial activity of the compounds of the invention is confirmed also in experimental septicemia in mice. Groups of five CDl mice of both sexes (Charles River, average weight 18-22 g) were infected intraperitoneally with Staphylococcus aureus ATCC 19636. The bacterial challenge (10⁶ cells/mouse) was given suspended in 0.5 ml of 5% bacteriological mucin (Difco). The test compounds were administered intraveneously once immediately after infection in a sterile aqueous solution containing 5% dimethylformamide and 10% Cremophor® EL (polyethoxylated castor oil). The ED₅₀ was calculated on the seventh day from the percentage of surviving animals at each dose by the Spearman and Kaerber method; its value resulted 15.4 mg/kg for antibiotic GE 2270 factor A₃ and 3.2 mg/kg for antibiotic GE 2270 factor A₁. In a similar experiment, but using groups of eight mice and administering a single dose level of test compound (20 mg/kg), the ratio survivors/treated at the seventh day was 1/8 in the case of antibiotic GE 2270 factor A₂ and 6/8 in the case of antibiotic GE 2270 factor H. The test compounds were given i.v. as a milky suspension in 10% dimethylformamide in 5% aqueous glucose. In view of their properties, the compounds of the invention can be used as active ingredients in the preparation of medicaments for human or animal treatment. In particular, antibiotic GE 2270 factor A₁, A₂, A₃ and H are antimicrobial agents mainly active against gram positive bacteria and gram positive as well as gram negative anaerobes. The main therapeutic indication of the antibiotic substances of the invention is thus in the treatment of infections related to the presence of microorganisms susceptible to them. The term "treatment" is intended to encompass also prophylaxis, therapy and cure. The patient receiving this treatment is any animal in need, including primates, in particular humans, and other mammals such as equines, cattle, swine and sheep; and poultry and pets in general. The compounds of the invention can be administered as such or in admixture with pharmaceutically acceptable carriers and can also be administered in conjunction with other antimicrobial agents. Conjunctive therapy thus includes sequential,, simultaneous and separate administration of the active compounds in a way that the therapeutical effects of the first administered one are not entirely disappeared when the subsequent is administered. A preferred pharmaceutical formulation is represented by a formulation suitable for a topical application on an intact or damaged skin or mucous membrane. Examples of such formulations are powders, ointments, creams and lotions. The excipients in these formulations are the usual pharmaceutically acceptable vehicles such oleaginous ointment bases (e.g. cetyl esters wax, oleic acid, olive oil, paraffin, spermaceti, starch glycerite); absorbent ointment bases (e.g. anhydrous lanolin, hydrophilic petrolatum), emulsion ointment bases (e.g. cetyl alcohol, glyceryl monostearate, lanolin, stearic acid), water-soluble ointment bases (e.g. glycol ethers and their derivatives which include polyethylene glycols, poly(oxy-1,2-ethanediyl)-alpha-hydro-omega-hydroxy-octadecanoate, polysorbates, and polyethylene glycols mono-stearates). These formulations may contain other known excipients, such as preservatives and are prepared as known in the art and reported in reference handbooks such as Remington's Pharmaceutical Sciences, Seventeenth edition, 1985, Mack Publishing Co. The compounds of the invention can also be formulated into formulation suitable for parenteral administration according to procedures known per se in the art. For instance, a compound of the invention is formulated with polypropylene glycol or dimethylacetamide and a surface-active agent such as polyoxyethylene sorbitan mono-oleate or polyethoxylated castor oil. A preferred formulation for parenteral administration includes the following excipients: Cremophor® EL (polyoxyl 35 castor oil USP/NF) 20%, propylene glycol 5-10%. Preferably, this formulation is used for i.v. administration in the treatment of any infection involving a microorganism susceptible to an antibiotic of the invention. In the treatment of pseudomembranous colitis or other diseases attributable to the presence of anaerobes in the gastrointestinal tract, an effective dose of the compounds of the invention may be administered orally in suitable pharmaceutical form such as a capsule or an aqueous suspension. The dosage of the active ingredient depends on many factors which include type, age and conditions of the patient, specific active ingredient and formulation selected for administration, administration schedule, etc. In general, effective antimicrobial dosages are employed per single unit dosage form. Repeated applications of these dosage forms, e.g. from 2 to 6 times a day, are in general preferred. An effective dosage may be in general in the range 0.5-50 mg/kg body weight/day. A preferred topic preparation is an ointment containing from 1% to 10% of a compound of the present invention. Anyway, the prescribing physician will be able to determine the optimal dosage for a given patient in a given situation. Besides their use as medicaments in human and veterinary therapy, the compounds of the invention can also be used as animal growth promoters. For this purpose, a compound of the invention is administered orally in a suitable feed. The exact concentration employed is that which is required to provide for the active agent in a growth promotant effective amount when normal amounts of feed are consumed. The addition of the active compound of the invention to animal feed is preferably accomplished by preparing an appropriate feed premix containing the active compound in an effective amount and incorporating the premix into the complete ration. Alternatively, an intermediate concentrate or feed supplement containing the active ingredient can be blended into the feed. The way in which such feed premixes and complete rations can be prepared and administered are described in reference books (such as "Applied Animal Nutrition", W.H. Freedman and CO., S. Francisco, USA, 1969 or "Livestock Feeds and Feeding" O and B books, Corvallis, Oregon, USA, 1977). The following examples further illustrate the invention and should not be interpreted as limiting it in any way. EXAMPLE 1 PREPARATION OF ANTIBIOTIC GE 2270 FACTOR A₁ 1.1 1M Hydrochloric acid (3.3 ml) is added to a solution of 150 mg of antibiotic GE 2270 factor A in 16 ml of 95% ethanol. The mixture is kept at room temperature for 5 min, diluted with 0.1M sodium phosphate buffer pH 7.5 and then adjusted to pH 7.5 with sodium hydroxide. After concentration to aqueous phase under reduced pressure, this mixture is extracted twice with ethyl acetate. Then the organic phase (which contains mainly antibiotic GE 2270 factor A₁) is concentrated to a solid residue that is solubilized in 5 ml of tetrahydrofuran and then diluted with water to the solubility limit. This solution is purified in 10 subsequent HPLC runs using a column (250 x 20 mm) of Nucleosil® C 18 (5 micrometer) reverse phase silica gel packed by Stacroma R eluting with a linear gradient from 64% to 93% of phase B in phase A, in 20 min, at a flow rate of about 15 ml/min. In this system, phase A is a 90:10 (v/v) mixture of 18 mM sodium phosphate pH 7.2 and acetonitrile, while phase B is a 40:60 (v/v) mixture of 18 mM sodium phosphate pH 7.2 and acetonitrile. Fractions are collected and UV monitored at 330 nm; those fractions which contain substantial amounts of antibiotic GE 2270 factor A₁, which correspond to the peaks of the UV plot, are pooled and concentrated under reduced pressure to aqueous phase which is extracted twice with ethyl acetate. This organic layer is then washed with distilled water to remove the residual inorganic salts and concentrated to a solid residue that is then dissolved in tetrahydrofuran and re-precipitated with petroleum ether, thus giving pure antibiotic GE 2270 factor A₁ (64 mg). 1.2 Antibiotic GE 2270 factor A₁ is the main reaction product of antibiotic GE 2270 factor A when this antibiotic is incubated for 15 min at room temperature in a 5/4/1 (v/v) mixture of diethylenedioxide, water and trifluoroacetic acid. Antibiotic GE 2270 factor A₁ is also obtained when antibiotic GE 2270 factor A is incubated in 0.5 N sulfuric acid or 0.25M phosphoric acid in a 1/1 (v/v) mixture of diethylenedioxide and water at room temperature. After dilution with cold water and neutralization, the mixture is extracted with ethyl acetate, the organic phase is concentrated and a solid precipitated by adding petroleum ether. Pure antibiotic GE 2270 factor A₁ is obtained by preparative HPLC as described in Example 1.1. 1.3 Antibiotic GE 2270 factor A₁ is the main reaction product of antibiotic GE 2270 factor A when this antibiotic is incubated overnight at 50°C in 0.5M ammonium chloride in a 1:1 (v/v) mixture of diethylenedioxide/water. After dilution with cold water and neutralization, the mixture is extracted with ethyl acetate, the organic phase is concentrated and a solid precipitated by adding petroleum ether. Pure antibiotic GE 2270 factor A₁ is obtained by preparative HPLC as described in Example 1.1. EXAMPLE 2 PREPARATION OF ANTIBIOTIC GE 2270 FACTOR A₂ 2.1 Antibiotic GE 2270 factor A (86 mg) is dissolved in 17 ml of 95% ethanol and 1.7 ml of acetic acid. After incubation at 60°C for 24 h, the resulting solution is diluted with 0.1M sodium phosphate buffer pH 7.5 (100 ml) and adjusted to pH 7.5 with 1M sodium hydroxide. Ethanol is removed by evaporation under reduced pressure and the aqueous residue is extracted twice with ethyl acetate (100 ml). The organic phase is concentrated under reduced pressure to obtain a solid residue which is solubilized with tetrahydrofuran and then precipitated by adding petroleum ether. Antibiotic GE 2270 factor A₂ (62 mg) is obtained with minor amounts of antibiotic GE 2270 factors A and A₁. Pure antibiotic GE 2270 factor A₂ is obtained by preparative HPLC as follows: 10 mg of the above crude product is solubilized in tetrahydrofuran, diluted to the solubility limit with water and then injected into a HPLC system with a column (250 x 20 mm) packed with Nucleosil R C18 (5 micrometer) reverse phase silica gel by Stacroma R , eluting with a linear gradient from 64% to 93% of phase B in phase A, in 20 min, at a flow rate of about 15 ml/min. In this system, phase A is a 90:10 (v/v) mixture of 18 mM sodium phosphate pH 7.2 and acetonitrile, while phase B is a 40:60 (v/v) mixture of 18 mM sodium phosphate pB 7.2 and acetonitrile. Fractions of five consecutive runs are collected and UV monitored at 330 nm. Fractions which contain substantial amounts of antibiotic GE 2270 factor A₂, which correspond to the major peaks of the UV elution profile, are pooled and concentrated under reduced pressure to an aqueous phase which is extracted twice with ethyl acetate. This organic layer is then washed with distilled water to remove the residual inorganic salts and concentrated to precipitate a solid residue that is then dissolved in tetrahydrofuran and re-precipitated with petroleum ether, to obtain pure antibiotic GE 2270 factor A₂ (45 mg). 2.2 Antibiotic GE 2270 factor A₂ is the main reaction product of antibiotic GE 2270 factor A when this antibiotic is incubated overnight at 80°C in a 1/1 (v/v) mixture of acetic acid and water. After dilution with water and neutralization, antibiotic GE 2270 factor A₂ is extracted with ethyl acetate, concentrated under reduced pressure and precipitated by adding petroleum ether. Pure antibiotic GE 2270 factor A₂ derivative is obtained by preparative HPLC as described in Example 2.1. 2.3 Antibiotic GE 2270 factor A₂ is the main reaction product of antibiotic GE 2270 factor A when this antibiotic is incubated overnight at 50°C in a 5/4/1 mixture (v/v) of diethylenedioxide, water and trifluoroacetic acid. Alternatively, the reaction may be conducted in the presence of inorganic acids such as 0.5N sulfuric acid or 0.25M phosphoric acid in a 1/1 (v/v) mixture of diethylenedioxide and water. After dilution with water and neutralization, antibiotic GE 2270 factor A₂ is extracted with ethyl acetate, concentrated under reduced pressure and precipitated by adding petroleum ether. Pure antibiotic GE 2270 factor A₂ can be obtained by preparative HPLC as described in Example 2.1. 2.4 Antibiotic GE 2270 factor A₂ is the main reaction product of antibiotic GE 2270 factor A when this antibiotic, solubilized in a 1/1 (v/v) mixture of diethylenedioxide and water, is incubated overnight at 50°C in the presence of an acidic cation exchange resin such as Dowex® 50Wx2 in the acid ionic form. Then the resin is removed from the reaction mixture and the solution is diluted with cold water and neutralized. Antibiotic GE 2270 factor A₂ is extracted with ethyl acetate, concentrated under reduced pressure and precipitated by adding petroleum ether. Pure antibiotic GE 2270 factor A₂ can be obtained by preparative HPLC as described in Example 2.1. 2.5 Antibiotic GE 2270 factor A₂ is also obtained from antibiotic GE 2270 factor A₁ when this antibiotic is treated in the conditions described for GE 2270 factor A in Examples 2.1, 2.2, 2.3 or 2.4. Generally, a solar yield of 60-85% is obtained in this reaction. EXAMPLE 3 PREPARATION OF ANTIBIOTIC GE 2270 FACTOR A₃ 3.1 Antibiotic GE 2270 factor A₂ is incubated for 1 h at room temperature in a solution of 0.5 M sodium carbonate in dioxane/H₂O 1/1. The reaction mixture is then diluted with cold water and brought to pH 6.5 with hydrochloric acid. The neutralized solution contains antibiotic GE 2270 factor A₃ as the main reaction product. This antibiotic is extracted from the aqueous phase with ethyl acetate and then is precipitated from the concentrated organic phase by adding petroleum ether. Pure antibiotic GE 2270 factor A₃ is obtained by column chromatography as described below. 3.2 1.5 Grams of crude GE 2270 A₃ is dissolved in 60 ml of a 1/1 (v/v) mixture of methanol and dichloromethane and adsorbed on silica gel (75-230 mesh) by evaporation of the solvents under reduced pressure. The solid residue is then put on the top of a silica gel (75-230 mesh) column (bed height 40 cm) equilibrated with dichloromethane. The column is then eluted with mixtures of methanol in dichloromethane in the order: 1) 2% methanol (450 ml); 2) 5% methanol (500 ml); 3) 10% methanol (600 ml); 4) 15% methanol (500 ml); 5) 20% methanol (500 ml); 6) 30% methanol (250 ml). Fractions are collected and monitored by TLC and a microbiological assay on B . subtilis ATCC 6633. Antibiotic GE 2270 factor A₃ is normally present in the eluates which contain about 15-20% methanol. The fractions containing the desired product are pooled and concentrated under reduced pressure. Upon addition of petroleum ether to the residue, antibiotic GE 2270 factor A₃ precipitates (854 mg of pure product). 3.3 Antibiotic GE 2270 factor A solubilized in a 1/1 (v/v) mixture of diethylenedioxide and water is incubated for 40 at 70°C h in the presence of a cation exchange resin (Dowex R 50Wx2) in the H⁺ form. The resin is then removed and the reaction solution is diluted with cold water and brought to pH 6.5 with aqueous sodium hydroxide. This mixture is extracted with ethyl acetate and precipitated from the concentrated organic phase by adding petroleum ether. Antibiotic GE 2270 factor A₃ is then isolated and purified by column chromatography as described in Example 3.2. (Global molar yield: 15%). EXAMPLE 4 PREPARATION OF ANTIBIOTIC GE 2270 FACTOR H 4.1 500 mg of sodium borohydride and 250 mg of antibiotic GE 2270 factor A are dissolved in 100 ml of a 1/1 (v/v) mixture of tetrahydrofuran and water. After three days at room temperature, the solution is brought to about pH 7 with a 1M NaH₂PO₄ and then concentrated under reduced pressure. The water is extracted twice with ethyl acetate and the organic phase is concentrated to dryness. The solid residue, that contains mainly antibiotic GE 2270 factor H, is dissolved in tetrahydrofuran and then precipitated by adding petroleum ether thus yielding 213 mg of a white precipitate which is purified by preparative HPLC as follows: 10 mg of crude reaction product is solubilized in tetrahydrofuran, diluted to the solubility limit with water and then injected into a HPLC column (250x20 mm) of Nucleosil R C18 (5 micrometer) reverse phase silica gel packed by Stacroma eluting with a linear gradient from 64% to 93% of phase B in phase A, in 20 min, at a flow rate of about 15 ml/min. Then elution is continued for 5 min with phase B alone. In this system, phase A is a 90:10 (v/v) mixture of 18 mM sodium phosphate pH 7.2 and acetonitrile, while phase B is a 40:60 (v/v) mixture of 18 mM sodium phosphate pH 7.2 and acetonitrile. Fractions of ten consecutive runs are collected and UV monitored at 330 nm; those fractions which contain substantial amounts of antibiotic GE 2270 factor H, which correspond to the peaks of the UV elution profile, are pooled and concentrated under reduced pressure to an aqueous phase which is extracted twice with ethyl acetate. This organic layer is then washed with distilled water to remove the residual inorganic salts and concentrated to precipitate a solid residue. This is then dissolved in tetrahydrofuran and re-precipitated with petroleum ether, to obtain pure antibiotic GE 2270 factor H (55 mg). Preparation of the starting materials The starting materials are prepared by following the procedures outlined in European Patent Application Publication No. 359062. BRIEF DESCRIPTION OF THE DRAWINGS: The symbols used in the attached U.V. spectra have the following meanings:

Claims: Claims for the following Contracting States : AT, BE, CH, DE, DK, FR, GB, IT, LI, LU, NL, SE An antibiotic substance which is antibiotic GE 2270 factor A₁, or an acceptable salt thereof, which has the following features in the unsalified form: A) ultraviolet absorption spectrum which exhibits the following absorption maxima: Lambda max (nm) 0.1 M HCl about 240 (shoulder) 310 O.1 M KOH about 245 (shoulder) 311 Phosphate buffer pH 7.4 about 245 (shoulder) 310 Methanol about 215 (shoulder) about 240 (shoulder) 309 B) infrared absorption spectrum in nujol mull which exhibits the following absorption maxima (cm⁻¹): 3700-3000; 3000-2800 (nujol); 1650; 1535; 1505; 1460 (nujol); 1375 (nujol) ; 1310; 1240; 1190; 1165; 1130-1000; 980; 930; 840; 805; 750; 720 (nujol) ; 700; C) ¹H-NMR spectrum which exhibits the following groups of signals at 500 MHz recorded in DMSO-d₆ (hexadeuterodimethylsulfoxide) using TMS as the internal standard (0.00 ppm); the multiplicity for each signal is also reported below (s=singlet; d=doublet; m=multiplet; dd=doublet of doublets; br s=broad singlet): 0.84, d; 0.87, d; 1.35, m; 1.91, m; 2.08, m; 2.16, m; 2.46, d; 2.58, s; 2.70, dd; 3.38, s; 3.76, m; 3.84, m; 4.26, dd; 4.33, m; 4.89, m; 4.97, s; 5.00, dd; 5.20, dd; 5.22, dd; 5.28 (2 protons), m; 6.01, d; 7.07, s; 7.2, s; 7.34, s; 7.22-7.38 (6 protons), m; 8.29, s; 8.39, d; 8.44, m; 8.45, d; 8.54, s; 8.60, s; 8.66, d; 9.69, d; 8.99, d; D) retention-time (R t ) of 13.4 min when analyzed by reverse phase HPLC under the following conditions: column: Ultrasphere ODS (reverse phase silanized silica gel; 5 micrometer) Altex (Beckman) 4.6 mm (i.d.) x 250 mm pre-column: Brownlee Labs RP 18 (octadecylsilane silica gel; 5 micrometer) eluent A: acetonitrile:18mM NaH₂PO₄, 70:30 (v/v), adjusted to pH 7.0 eluent B: acetonitrile:18mM NaH₂PO₄ 10:90 (v/v), adjusted to pH 7.0 elution mode: linear gradient of eluent A in eluent B from 45% to 70% in 20 min flow rate: 1.8 ml/min U.V. detector: 254 nm internal standard: Chloramphenicol (R t = 3.6 min) E) elemental analysis, after the sample has been previously dried at about 140°C under inert atmosphere, which indicated the following composition: carbon, hydrogen, nitrogen, sulfur; F) FAB-MS analysis showing the low mass isotope of the protonated molecular ion at m/z 1308 mass units; all the other peaks above 800 m/z mass units in the spectrum, not counting isotope peaks, were lower than 20% of the molecular ion, upon analysis with a Kratos MS-50 double focusing mass spectrometer under the following experimental conditions: Xe fast atom bombardment at 6 Kv; 0.6 mA discharge current; glycerol matrix; positive ionization mode An antibiotic substance which is antibiotic GE 2270 factor A₂, or an acceptable salt thereof, which has the following features in the unsalified form: A) ultraviolet absorption spectrum which exhibits the following absorption maxima: Lambda max (nm) 0.1 M HCl about 245 (shoulder) 309 O.1 M KOH about 245 (shoulder) 309 Phosphate buffer pH 7.4 about 245 (shoulder) 309 Methanol about 215 (shoulder) about 242 (shoulder) 306 B) infrared absorption spectrum in nujol mull which exhibits the following absorption maxima (cm⁻¹): 3700-3000; 3000-2800 (nujol); 1725; 1655; 1590-1480; 1460 (nujol); 1410; 1375 (nujol); 1335; 1305; 1265-1130; 1090; 1050; 1015; 980; 945; 930; 840; 805; 745; 720 (nujol); 700; C) ¹H-NMR spectrum which exhibits the following groups of signals at 500 MHz recorded in DMSO-d₆ (hexadeuterodimethylsulfoxide) using TMS as the internal standard (0.00 ppm); the multiplicity for each signal is reported below (s=singlet; d=doublet; m=multiplet; dd=doublet of doublets; br s=broad singlet): 0.83, d; 0.86, d; 1.30, m; 1.82, m; 1.90, m; 2.17, m; 2.46, d; 2.57, s; 2.70, dd; 3.37, s; 3.40, m; 3.48, m; 3.77, dd; 4.24, m; 4.28, dd; 4.52, d; 4.53, br s; 4.67, d; 4.96, s; 4.98, dd; 5.19, m; 5.21, m; 5.28, m; 6.01, d; 7.34, s; 7.22-7.35, m; 8.26, d; 8.28, s; 8.42, d; 8.45, s; 8.59, s; 8.67 (2 protons), d; 8.73, s; 9.00, d; D) retention-time (R t ) of 17.0 min when analyzed by reverse phase HPLC under the following conditions: column: Ultrasphere ODS (reverse phase silanized silica gel; 5 micrometer) Altex (Beckman) 4.6 mm (i.d.) x 250 mm pro-column: Brownlee Labs RP 18 (octadecylsilane silica gel; 5 micrometer) eluent A: acetonitrile:18mM NaH₂PO₄, 70:30 (v/v), adjusted to pH 7.0 eluent B: acetonitrile:18mM NaH₂PO₄ 10:90 (v/v), adjusted to pH 7.0 elution mode: linear gradient of eluent A in eluent B from 45% to 70% in 20 min flow rate: 1.8 ml/min U.V. detector: 254 nm internal standard: Chloramphenicol (R t = 3.6 min) E) elemental analysis, after the sample has been previously dried at about 140°C under inert atmosphere, which indicated the following composition: carbon, hydrogen, nitrogen, sulfur; F) FAB-MS analysis showing the low mass isotope of the protonated molecular ion at m/z 1291 mass units; all the other peaks above 800 m/z mass units in the spectrum, not counting isotope peaks, were lower than 20% of the molecular ion, upon analysis with a Kratos MS-50 double focusing mass spectrometer under the following experimental conditions: Xe fast atom bombardment at 6 Kv; 0.6 mA discharge current; glycerol matrix; positive ionization mode An antibiotic substance which is antibiotic GE 2270 factor A₃, or an acceptable salt thereof, which has the following features in the unsalified form: A) ultraviolet absorption spectrum which exhibits the following absorption maxima: Lambda max (nm) O.1 M KOH 240 (shoulder) 309 330 (shoulder) Phosphate buffer pH 7.4 240 (shoulder) 309 330 shoulder Methanol 240 (shoulder) 309 340 (shoulder) B) infrared absorption spectrum in nujol mull which exhibits the following absorption maxima (cm⁻¹): 3700-3140; 3110; 3020-2750 (nujol); 1720; 1655; 1590-1520; 1500; 1460 (nujol); 1375 (nujol); 1270-1200; 1130-1030; 1020; 980; 930; 840; 805; 750; 720 (nujol); 700; C) ¹H-NMR spectrum which exhibits the following groups of signals (in ppm) at 500 MHz recorded in DMSO-d₆ (hexadeuterodimethylsulfoxide) using TMS as the internal standard (0.00 ppm); the number of protons and multiplicity for each signal is also reported below (s=singlet; d=doublet; m=multiplet; dd=doublet of doublets; br s=broad singlet): 9.02,1H (d); 8.71,1H (d); 8.70,1H (d); 8.65,1H (s); 8.57,1H (s); 8.46,1H (m); 8.38,1H (d); 8.28,1H (d); 8.25,1H (s); 7.38,1H (m); 7.37,1H (s); 7.36-7.20,5H (m); 6.05,1H (br s); 5.31,1H (m); 5.27,1H (dd); 5.20,1H (dd); 5.03,1H (d); 4.99,2H (s); 4.32,1H (dd); 3.82,1H (dd); 3.38,3H (s); 2.74,1H (dd); 2.60,3H(s); 2.49,3H (d); 2.17,1H (m); 1.35,1H (m); 0.88,3H (d); 0.84,3H (d); D) retention-time (R t ) of 7.1 min when analyzed by reverse phase HPLC under the following conditions: column: Ultrasphere ODS (reverse phase silanized silica gel; 5 micrometer) Altex (Beckman) 4.6 mm (i.d.) x 250 mm pre-column: Brownlee Labs RP 18 (octadecylsilane silica gel; 5 micrometer) eluent A: acetonitrile:18mM NaH₂PO₄, 70:30 (v/v), adjusted to pH 7.0 eluent B: acetonitrile:18mM NaH₂PO₄ 10:90 (v/v), adjusted to pH 7.0 elution mode: linear gradient of eluent A in eluent B from 45% to 70% in 20 min flow rite: 1.8 ml/min U.V. detector: 254 nm internal standard: Chloramphenicol (R t = 3.6 min) E) elemental analysis, after the sample has been previously dried it about 140°C under inert atmosphere, which indicated the following composition: carbon 51.27%, hydrogen 4.02%, nitrogen 14.94%, sulfur. F) FAB-MS analysis showing the low mass isotope of the protonated molecular ion it m/z 1125 mass units: all the other peaks above 800 m/z mass units in the spectrum, not counting isotope peaks, were lower than 20% of the molecular ion, upon analysis with a Kratos MS-50 double focusing mass spectrometer under the following experimental conditions: Xe fast atom bombardment at 6 Kv; 0.6 mA discharge current; glycerol matrix: positive ionization mode G) ¹³C-NMR spectrum exhibiting the following groups of signals (ppm) at 125 MHz in DMSO-d₆ using TMS as the internal reference (0.00 ppm), 171.2; 169.9; 169.6; 168.5; 167.8; 165.7; 164.8; 162.2; 161.4; 161.3; 160.5; 160.4; 153.5; 150.4; 150.1; 149.5; 149.1; 147.0; 143.8; 142.1; 141.8; 141.4; 141.0; 139.6; 131.8; 128.0 (2 carbons); 127.7; 127.6; 126.9; 126.8 (2 carbons); 123.1; 118.7; 116.4; 73.9; 67.4; 58.7; 58.3; 55.5; 48.2; 41.2; 37.7; 34.1; 25.9; 18.5; 18.0; 12.0; H) a specific optical rotation [α] 20 / D of +182.5 in CHCl₃ + 10% CH₃OH An antibiotic substance which is antibiotic GE 2270 factor H, or an acceptable salt thereof, which has the following features in the unsalified form: A) ultraviolet absorption spectrum which exhibits the following absorption maxima: Lambda max (nm) 0.1 M HCl 248 303 O.1 M KOH about 245 (shoulder) 310 Phosphate buffer pH 7.4 about 240 (shoulder) 312 Methanol about 215 (shoulder) about 240 (shoulder) 309 B) infrared absorption spectrum in nujol mull which exhibits the following absorption maxima (cm⁻¹): 3700-3000; 3000-2800 (nujol); 1655; 1590-1480; 1460 (nujol); 1375 (nujol); 1310; 1220; 1190; 1130-1000; 980; 930; 840; 820-680; 720 (nujol); 640; C) ¹H-NMR spectrum which exhibits the following groups of signals (ppm) at 500 MHz recorded in DMSO-d₆ (hexadeuterodimethylsulfoxide) using TMS as the internal standard (0.00 ppm); the multiplicity for each signal is also reported below (s=singlet; d=doublet; m=multiplet; dd=doublet of doublets; br s=broad singlet): 0.83, d; 0.87 d; 1.30, m; 2.16, m; 2.46, d; 2.58, s; 2.70, dd; 3.38, s; 3.52, m; 3.61, m; 3.77, dd; 4.25, m; 4.30, m; 4.35, m; 4.47, m; 4.88, m; 4.97, s; 4.99, dd; 5.20, m; 5.23, m; 5.28, m; 6.02, d; 7.36, s; 7.22-7.40, m; 8.26, d; 8.28, s; 8.42, d; 8.43, m; 8.47, s; 8.60, s; 8.67, d; 9.02, d; D) retention-time (R t ) of 18.0 min when analyzed by reverse phase HPLC under the following conditions: column: Ultrasphere ODS (reverse phase silanized silica gel; 5 micrometer) Altex (Beckman) 4.6 mm (i.d.) x 250 mm pre-column: Brownlee Labs RP 18 (octadecylsilane silica gel; 5 micrometer) eluent A: acetonitrile:18mM NaH₂PO₄, 70:30 (v/v), adjusted to pH 7.0 eluent B: acetonitrile:18mM NaH₂PO₄ 10:90 (v/v), adjusted to pH 7.0 elution mode: linear gradient of eluent A in eluent B from 45% to 70% in 20 min flow rate: 1.8 ml/min U.V. detector: 254 nm internal standard: Chloramphenicol (R t = 3.6 min) E) elemental analysis, after the sample has been previously dried at about 140°C under inert atmosphere, which indicated the following composition: carbon, hydrogen, nitrogen, sulfur; F) FAB-MS analysis showing the low mass isotope of the protonated molecular ion at m/z 1180 mass units; all the other peaks above 800 m/z mass units (not counting isotope peaks) in the spectrum were lower than 20% of the molecular ion, upon analysis with a Kratos MS-50 double focusing mass spectrometer under the following experimental conditions: Xe fast atom bombardment at 6 Kv; 0.6 mA discharge current; glycerol matrix; positive ionization mode A process for preparing a compound of claim 1 2, 3 or 4 which comprises: a) subjecting antibiotic GE 2270 factor A to selective hydrolytic conditions to obtain antibiotic GE 2270 factor A₁, A₂ or A₃ b) subjecting antibiotic GE 2270 factor A to selective cleavage under reducing conditions to obtain antibiotic GE 2270 factor H c) isolating and purifying the obtained products according to known per se techniques. A process according to claim 5 point a) wherein the selective hydrolytic conditions are represented by an aqueous acidic medium and a polar organic solvent. A process according to claim 6 for selectively obtaining antibiotic GE 2270 factor A₁ wherein the reaction temperature is between -10°C and 50°C. A process according to claim 5 for selectively obtaining antibiotic GE 2270 factor A₂ wherein the hydrolysis is conducted in an acid medium in the presence of a polar organic solvent at a temperature between 40°C and 90°C. A process according to claim 5 for selectively obtaining antibiotic GE 2270 factor A₃ wherein the hydrolysis is conducted in an acid medium in the presence of a polar organic solvent at a temperature between 65°C and 90°C. A process according to claim 5 for selectively obtaining antibiotic GE 2270 factor A₃ which comprises subjecting antibiotic GE 2270 factor A₂ to basic hydrolytic conditions in the presence of a polar organic solvent. A process according to claim 5 for selectively obtaining antibiotic GE 2270 factor H wherein the reducing conditions are given by alkali metal borohydrides in a compatible polar organic solvent. A pharmaceutical composition comprising a compound according to any one of claims 1 to 4 in admixture with a pharmaceutically acceptable carrier. A compound according to any one of claims 1 to 4 for use as a medicine. Use of a compound according to any one of claims 1 to 4 for preparing a medicament for antimicrobial use. Claims for the following Contracting States : ES, GR A process for preparing an antibiotic substance selected from antibiotic GE 2270 factors A₁, A₂, A₃ or H, and the acceptable salts thereof, which have the following features in the unsalified form: Physico-chemical characteristics of antibiotic GE 2270 factor A ₁: A) ultraviolet absorption spectrum which exhibits the following absorption maxima: Lambda max (nm) 0.1 M HCl about 240 (shoulder) 310 O.1 M KOH about 245 (shoulder) 311 Phosphate buffer pH 7.4 about 245 (shoulder) 310 Methanol about 215 (shoulder) about 240 (shoulder) 309 B) infrared absorption spectrum in nujol mull which exhibits the following absorption maxima (cm⁻¹): 3700-3000; 3000-2800 (nujol); 1650; 1535; 1505; 1460 (nujol); 1375 (nujol) ; 1310; 1240; 1190; 1165; 1130-1000; 980; 930; 840; 805; 750; 720 (nujol) ; 700; C) ¹H-NMR spectrum which exhibits the following groups of signals at 500 MHz recorded in DMSO-d₆ (hexadeuterodimethylsulfoxide) using TMS as the internal standard (0.00 ppm); the multiplicity for each signal is also reported below (s=singlet; d=doublet; m=multiplet; dd=doublet of doublets; br s=broad singlet): 0.84, d; 0.87, d; 1.35, m; 1.91, m; 2.08, m; 2.16, m; 2.46, d; 2.58, s; 2.70, dd; 3.38, s; 3.76, m; 3.84, m; 4.26, dd; 4.33, m; 4.89, m; 4.97, s; 5.00, dd; 5.20, dd; 5.22, dd; 5.28 (2 protons), m; 6.01, d; 7.07, s; 7.2, s; 7.34, s; 7.22-7.38 (6 protons), m; 8.29, s; 8.39, d; 8.44, m; 8.45, d; 8.54, s; 8.60, s; 8.66, d; 9.69, d; 8.99, d; D) retention-time (R t ) of 13.4 min when analyzed by reverse phase HPLC under the following conditions: column: Ultrasphere ODS (reverse phase silanized silica gel; 5 micrometer) Altex (Beckman) 4.6 mm (i.d.) x 250 mm pre-column: Brownlee Labs RP 18 (octadecylsilane silica gel; 5 micrometer) eluent A: acetonitrile:18mM NaH₂PO₄, 70:30 (v/v), adjusted to pH 7.0 eluent B: acetonitrile:18mM NaH₂PO₄ 10:90 (v/v), adjusted to pH 7.0 elution mode: linear gradient of eluent A in eluent B from 45% to 70% in 20 min flow rate: 1.8 ml/min U.V. detector: 254 nm internal standard: Chloramphenicol (R t = 3.6 min) E) elemental analysis, after the sample has been previously dried at about 140°C under inert atmosphere, which indicated the following composition: carbon, hydrogen, nitrogen, sulfur; F) FAB-MS analysis showing the low mass isotope of the protonated molecular ion at m/z 1308 mass units; all the other peaks above 800 m/z mass units in the spectrum, not counting isotope peaks, were lower than 20% of the molecular ion, upon analysis with a Kratos MS-50 double focusing mass spectrometer under the following experimental conditions: Xe fast atom bombardment at 6 Kv; 0.6 mA discharge current; glycerol matrix; positive ionization mode Physico-chemical characteristics of antibiotic GE 2270 factor A ₂: A) ultraviolet absorption spectrum which exhibits the following absorption maxima: Lambda max (nm) 0.1 M HCl about 245 (shoulder) 309 O.1 M KOH about 245 (shoulder) 309 Phosphate buffer pH 7.4 about 245 (shoulder) 309 Methanol about 215 (shoulder) about 242 (shoulder) 306 B) infrared absorption spectrum in nujol mull which exhibits the following absorption maxima (cm⁻¹): 3700-3000; 3000-2800 (nujol); 1725; 1655; 1590-1480; 1460 (nujol); 1410; 1375 (nujol); 1335; 1305; 1265-1130; 1090; 1050; 1015; 980; 945; 930; 840; 805; 745; 720 (nujol); 700; C) ¹H-NMR spectrum which exhibits the following groups of signals at 500 MHz recorded in DMSO-d₆ (hexadeuterodimethylsulfoxide) using TMS as the internal standard (0.00 ppm); the multiplicity for each signal is reported below (s=singlet; d=doublet; m=multiplet; dd=doublet of doublets; br s=broad singlet): 0.83, d; 0.86, d; 1.30, m; 1.82, m; 1.90, m; 2.17, m; 2.46, d; 2.57, s; 2.70, dd; 3.37, s; 3.40, m; 3.48, m; 3.77, dd; 4.24, m; 4.28, dd; 4.52, d; 4.53, br s; 4.67, d; 4.96, s; 4.98, dd; 5.19, m; 5.21, m; 5.28, m; 6.01, d; 7.34, s; 7.22-7.35, m; 8.26, d; 8.28, s; 8.42, d; 8.45, s; 8.59, s; 8.67 (2 protons), d; 8.73, s; 9.00, d; D) retention-time (R t ) of 17.0 min when analyzed by reverse phase HPLC under the following conditions: column: Ultrasphere ODS (reverse phase silanized silica gel; 5 micrometer) Altex (Beckman) 4.6 mm (i.d.) x 250 mm pre-column: Brownlee Labs RP 18 (octadecylsilane silica gel; 5 micrometer) eluent A: acetonitrile:18mM NaH₂PO₄, 70:30 (v/v), adjusted to pH 7.0 eluent B: acetonitrile:18mM NaH₂PO₄ 10:90 (v/v), adjusted to pH 7.0 elution mode: linear gradient of eluent A in eluent B from 45% to 70% in 20 min flow rate: 1.8 ml/min U.V. detector: 254 nm internal standard: Chloramphenicol (R t = 3.6 min) E) elemental analysis, after the sample has been previously dried at about 140°C under inert atmosphere, which indicated the following composition: carbon, hydrogen, nitrogen, sulfur; F) FAB-MS analysis showing the low mass isotope of the protonated molecular ion at m/z 1291 mass units; all the other peaks above 800 m/z mass units in the spectrum, not counting isotope peaks, were lower than 20% of the molecular ion, upon analysis with a Kratos MS-50 double focusing mass spectrometer under the following experimental conditions: Xe fast atom bombardment at 6 Kv; 0.6 mA discharge current; glycerol matrix; positive ionization mode Physico-chemical characteristics of antibiotic GE 2270 factor A ₃ A) ultraviolet absorption spectrum which exhibits the following absorption maxima: Lambda max (nm) O.1 M KOH 240 (shoulder) 309 330 (shoulder) Phosphate buffer pH 7.4 240 (shoulder) 309 330 shoulder Methanol 240 (shoulder) 309 340 (shoulder) B) infrared absorption spectrum in nujol mull which exhibits the following absorption maxima (cm⁻¹): 3700-3140; 3110; 3020-2750 (nujol); 1720; 1655; 1590-1520; 1500; 1460 (nujol); 1375 (nujol); 1270-1200; 1130-1030; 1020; 980; 930; 840; 805; 750; 720 (nujol); 700; C) ¹H-NMR spectrum which exhibits the following groups of signals (in ppm) at 500 MHz recorded in DMSO-d₆ (hexadeuterodimethylsulfoxide) using TMS as the internal standard (0.00 ppm); the number of protons and multiplicity for each signal is also reported below (s=singlet; d=doublet; m=multiplet; dd=doublet of doublets; br s=broad singlet): 9.02,1H (d); 8.71,1H (d); 8.70,1H (d); 8.65,1H (s); 8.57,1H (s); 8.46,1H (m); 8.38,1H (d); 8.28,1H (d); 8.25,1H (s); 7.38,1H (m); 7.37,1H (s); 7.36-7.20,5H (m); 6.05,1H (br s); 5.31,1H (m); 5.27,1H (dd); 5.20,1H (dd); 5.03,1H (d); 4.99,2H (s); 4.32,1H (dd); 3.82,1H (dd); 3.38,3H (s); 2.74,1H (dd); 2.60,3H (s); 2.49,3H (d); 2.17,1H (m); 1.35,1H (m); 0.88,3H (d); 0.84,3H (d); D) retention-time (R t ) of 7.1 min when analyzed by reverse phase HPLC under the following conditions: column: Ultrasphere ODS (reverse phase silanized silica gel; 5 micrometer) Altex (Beckman) 4.6 mm (i.d.) x 250 mm pre-column: Brownlee Labs RP 18 (octadecylsilane silica gel; 5 micrometer) eluent A: acetonitrile:18mM NaH₂PO₄, 70:30 (v/v), adjusted to pH 7.0 eluent B: acetonitrile:18mM NaH₂PO₄ 10:90 (v/v), adjusted to pH 7.0 elution mode: linear gradient of eluent A in eluent B from 45% to 70% in 20 min flow rate: 1.8 ml/min U.V. detector: 254 nm internal standard: Chloramphenicol (R t = 3.6 min) E) elemental analysis, after the sample has been previously dried at about 140°C under inert atmosphere, which indicated the following composition: carbon 51.27%, hydrogen 4.02%, nitrogen 14.94%, sulfur; F) FAB-MS analysis showing the low mass isotope of the protonated molecular ion at m/z 1125 mass units; all the other peaks above 800 m/z mass units in the spectrum, not counting isotope peaks, were lower than 20% of the molecular ion, upon analysis with a Kratos MS-50 double focusing mass spectrometer under the following experimental conditions: Xe fast atom bombardment at 6 Kv; 0.6 mA discharge current; glycerol matrix; positive ionization mode G) ¹³C-NMR spectrum exhibiting the following groups of signals (ppm) at 125 MHz in DMSO-d₆ using TMS as the internal reference (0.00 ppm), 171.2; 169.9; 169.6; 168.5; 167.8; 165.7; 164.8; 162.2; 161.4; 161.3; 160.5; 160.4; 153.5; 150.4; 150.1; 149.5; 149.1; 147.0; 143.8; 142.1; 141.8; 141.4; 141.0; 139.6; 131.8; 128.0 (2 carbons); 127.7; 127.6; 126.9; 126.8 (2 carbons); 123.1; 118.7; 116.4; 73.9; 67.4; 58.7; 58.3; 55.5; 48.2; 41.2; 37.7; 34.1; 25.9; 18.5; 18.0; 12.0; H) a specific optical rotation [α] 20 / D of +182.5 in CHCl₃ + 10% CH₃OH Physico-chemical characteristics of antibiotic GE 2270 factor H A) ultraviolet absorption spectrum which exhibits the following absorption maxima: Lambda max (nm) 0.1 M HCl 248 303 O.1 M KOH about 245 (shoulder) 310 Phosphate buffer pH 7.4 about 240 (shoulder) 312 Methanol about 215 (shoulder) about 240 (shoulder) 309 B) infrared absorption spectrum in nujol mull which exhibits the following absorption maxima (cm⁻¹): 3700-3000; 3000-2800 (nujol); 1655; 1590-1480; 1460 (nujol); 1375 (nujol); 1310; 1220; 1190; 1130-1000; 980; 930; 840; 820-680; 720 (nujol); 640; C) ¹H-NMR spectrum which exhibits the following groups of signals (ppm) at 500 MHz recorded in DMSO-d₆ (hexadeuterodimethylsulfoxide) using TMS as the internal standard (0.00 ppm); the multiplicity for each signal is also reported below (s=singlet; d=doublet; m=multiplet; dd=doublet of doublets; br s=broad singlet): 0.83, d; 0.87 d; 1.30, m; 2.16, m; 2.46, d; 2.58, s; 2.70, dd; 3.38, s; 3.52, m; 3.61, m; 3.77, dd; 4.25, m; 4.30, m; 4.35, m; 4.47, m; 4.88, m; 4.97, s; 4.99, dd; 5.20, m; 5.23, m; 5.28, m; 6.02, d; 7.36, s; 7.22-7.40, m; 8.26, d; 8.28, s; 8.42, d; 8.43, m; 8.47, s; 8.60, s; 8.67, d; 9.02, d; D) retention-time (R t ) of 18.0 min when analyzed by reverse phase HPLC under the following conditions: column: Ultrasphere ODS (reverse phase silanized silica gel; 5 micrometer) Altex (Beckman) 4.6 mm (i.d.) x 250 mm pre-column: Brownlee Labs RP 18 (octadecylsilane silica gel; 5 micrometer) eluent A: acetonitrile:18mM NaH₂PO₄, 70:30 (v/v), adjusted to pH 7.0 eluent B: acetonitrile:18mM NaH₂PO₄ 10:90 (v/v), adjusted to pH 7.0 elution mode: linear gradient of eluent A in eluent B from 45% to 70% in 20 min flow rate: 1.8 ml/min U.V. detector: 254 nm internal standard: Chloramphenicol (R t = 3.6 min) E) elemental analysis, after the sample has been previously dried at about 140°C under inert atmosphere, which indicated the following composition: carbon, hydrogen, nitrogen, sulfur; F) FAB-MS analysis showing the low mass isotope of the protonated molecular ion at m/z 1180 mass units; all the other peaks above 800 m/z mass units (not counting isotope peaks) in the spectrum were lower than 20% of the molecular ion, upon analysis with a Kratos MS-50 double focusing mass spectrometer under the following experimental conditions: Xe fast atom bombardment at 6 Kv; 0.6 mA discharge current; glycerol matrix; positive ionization mode which comprises: a) subjecting antibiotic GE 2270 factor A to selective hydrolytic conditions to obtain antibiotic GE 2270 factor A₁, A₂ or A₃ b) subjecting antibiotic GE 2270 factor A to selective cleavage under reducing conditions to obtain antibiotic GE 2270 factor H c) isolating and purifying the obtained products according to known per se techniques. A process according to claim 1 point a) wherein the selective hydrolytic conditions are represented by an aqueous acidic medium and a polar organic solvent. A process according to claim 2 for selectively obtaining antibiotic GE 2270 factor A₁ wherein the reaction temperature is between -10°C and 50°C. A process according to clam 1 for selectively obtaining antibiotic GE 2270 factor A₂ wherein the hydrolysis is conducted in an acid medium in the presence of a polar organic solvent at a temperature between 40°C and 90°C. A process according to claim 1 for selectively obtaining antibiotic GE 2270 factor A₃ wherein the hydrolysis is conducted in an acid medium in the presence of a polar organic solvent at a temperature between 65°C and 90°C. A process according to claim 1 for selectively obtaining antibiotic GE 2270 factor A₃ which comprises subjecting antibiotic GE 2270 factor A₂ to basic hydrolytic conditions in the presence of a polar organic solvent. A process according to claim 1 for selectively obtaining antibiotic GE 2270 factor H wherein the reducing conditions are given by alkali metal borohydrides in a compatible polar organic solvent. Use of a compound of claim 1 for preparing a medicament for antimicrobial use.

Inventors: SELVA ENRICO, TAVECCHIA PAOLO, SELVA, ENRICO, TAVECCHIA, PAOLO
Applicants: LEPETIT SPA, GRUPPO LEPETIT S.P.A.
Application year: 1990
Main classification: C12P1
IPC codes: A61K35, C07K5, C12P1, C12R1, C07G11, A61P31, A23K1, A61K38, A61P15