It is known that the wide use of antimicrobial agents in the infection treatment has caused the development of strains resistant to these drugs, for example the case of antiviral, antifungal and antibacterial agents can be mentioned.

This resistance generally arises when microorganisms develop growth and reproduction mechanisms on which the antimicrobial therapy is ineffective, or when the microorganisms produce enzymes which neutralize the drug. The resistant microbial strain is then able to multiply, causing the illness prolongation and worsening, with possible diffusion of the infection in the communities. This fact, as known, can determine notable consequences at a social- economic and sanitary level.

A method to solve this problem is to increase the dosage of the antimicrobial drugs. In this way there is the drawback of an increased incidence of side effects both local and systemic. Besides, cases of microbial superinfection deriving from the antimicrobial agent itself due to the inbalance between pathogen and non pathogen microbial flora often occur. It is well known that antimicrobial agents must act on the pathogen agents which are responsible of the unhealthy process and leave unaltered the non pathogen microbes useful for the organism.

A widely followed approach for solving the problem of the microbial resistance, and/or of the diffusion of pharmaco-resistant strains, has been to introduce in therapy new molecules to be used as antimicrobial agents. The results so far obtained are not satisfactory.

The need was therefore felt to have available drugs able not only to be active on the microorganism but also to prevent and/or reduce the microbial resistance and therefore to allow a complete and effective antimicrobial therapy, said drugs being effective at the conventional minimum dosages to avoid the side toxic effects. Among the latter skin rash and the effects on the stomach, liver and kidney can for example be mentioned.

It has been surprisingly and unexpectedly found by the Applicant that it is possible to solve the above technical problem by using compounds which have shown to be able to effectively interact with microbes and to prevent or reduce the microbial resistance.

An object of the present invention is the use of nitrate salts of antimicrobial agents, or their pharmaceutical compositions, for the preparation of medicaments usable in the treatment of infectious diseases. Preferably the invention relates to the use of nitrate salts of antiviral, antifungal and antibacterial agents, or their pharmaceutical compositions ; the antimicrobial agents usable for preparing the nitrate salts of the present invention must satisfy the following test : in the culture of specific pathogen microbes responsible for the single pathologies, the antimicrobial agent is inoculated at a concentration such as to result effective as antimicrobial agent and such as not to produce cytotoxicity in mammalian cells.

See for example the test of the dilution in vitro on medium reported in the Examples for the antibacterial agents.

More specifically the present invention relates to the use of nitrate salts of compounds, or their pharmaceutical compositions, for preparing medicaments usable in the treatment of infectious diseases as antimicrobial agents, said compounds preferably being selected from the following classes : class I) wherein : R1 = H, C1 or dimethylamino, R2 = H, OH, or free valence, R3 = H, CH3, when R2 is free valence with the doublet of the C-R3 bond it forms a double bond and R3 is methylene, R4 = H, OH, RS = H, CH20H, or one of the following substituents : class II) wherein : X and Y, different the one from the other, are C or N, R6 = ciclopropyl, CzHs, 4-fluorophenyl, 2, 4-difluorophenyl, 2- fluoroethyl, R, = H, amino, CH3, Ra = H or F, when Y = N, Ra is free valence and it is the free doublet on the nitrogen atom, R9 = H, CH3 or one of the following substituents : (IIA) wherein M = H, CH3, C2Hs, OH, (IIB) (IIC) (IID) (IIE) wherein T1 is H, OH Ra and Rg taken together form the bivalent radical having <BR> <BR> <BR> <BR> O-CH-O-<BR> <BR> formula: @ (IIP), Rio = H, Cl, F, when X = N, Rio is free valence and it is the free doublet on the nitrogen atom, R6 and Rio taken together form the following bivalent radicals : -S-CH2-CH2- (IIQ) when X in the formula (II) = N, R10 is free valence and it forms a double bond with the carbon atom adjacent to the nitrogen ; class IIIa) : (IIIa) wherein : Z = S, C, R11 = H, pivaloyloxymethylene of formula (IIIaF) wherein T2 is the tert-butyl group, R12 = C1, CH3, acetyloxymethylene of formula (IIIaF) wherein T2 is CH3, 2-propenyl or one of the following substituents : R13 = amino, OH, or the substituent (IIIaD) : (IIIaD) (IIIaE) R14 is phenyl, 4-hydroxyphenyl, or the radical (IIIaE) ; class IIIb) (IIIb) wherein : X = CH, N, Y = C, N, Ris = COOH, COO-, (CH3) 3CCOOCH20CO-or (CH3) ZCHOCOOCH (CH3) OCO-, R16 = H, CH3, C2H5, -CH=CH2, NH2COOCH2-, CH3COOCH2-, or one of the following substituents : (IIIbA) (IIIbC) (IIIbD) (IIIbE) (IIIbF) (IIIbG) (IIIbH) (IIIbL) (IIIbM) (IIIbN) when Ri. is carboxylated anion R16 is a radical selected from the following : (IIIbL), (IIIbM) or (IIIbN) R17 = OH, OCH3, C2H5, -OCH2COOH, -CH2COOH ; class IIIc) (IIIc) wherein : Ri. is one of the following substituents : (IIIcA) (IIIcB) (IIIcD) (IIIcE) (IIIcF) (IIIcG) R19 = H, CH3COOCH2-, or one of the following groups : (IIICH) (IIIcL) (IIIcM) (IIIcN) class IVa : (IVa) wherein : R20 is one of the following substituents : NH2 NH2 NH2 , , , (IVaA) (IVaB) (IVaC) (IVaD) (IVaE) (IVaF) (IVaG) (IVaH) (IVaL) (IVaM) (IVaN) (IVaP) R21= H, the radical (IIIaF) with T2 = tert-butyl, CH (CH3)OCOOC2H5 or one of the following substituents : -CH2CH2N(CH2CH3)2.HI (IVaR), (IVaS) (IVaT) (IVaU) class IVb) (IVb) wherein : R22 = H, CH3, R23 is selected from the following groups : -CH2 CH2NHCH=NH (IVbD), (IVbA) (IVbC) class IVc) (IVc) wherein : R33, R34, Reg, equal to or different from each other, are H, CH3 ; R35 = H,-CH20CONH,, class V) (V) wherein R24 = H, Br, OCH3, CH30CH2CH20- class VI) wherein : R25 is one of the following substituents : (VIA) (VIB) (VIC) (VID) (VIE) class VII) (VII) wherein R. 6 H, or one of the following substituents : benzoyl, acetyl, 3-methyl-2-butenoyl, carbamoyl, aminothioxo NH2C (S)- 2-pyridinyl, pyrazinyl, 2-pyrimidinyl, 2-thiazolyl, salicyl-4-yl, 6-chloro-pyridazine-3-yl, 1-ethyl-1, 2-dihydro-2- oxo-pyrimidin-4-yl, 5, 6-dimethoxy-pyrimidin-4-yl, 2, 6-dime- thoxy-Pyrimidin-4-yl, 4-methyl-pyrimidin-2-yl, 5-methoxy-pyri- midin-2-yl, 4, 6-dimethyl-pyrimidin-2-yl, 6-methoxy-2-methyl- pyrimidin-4-yl, 5-methyl-pyrimidin-2-yl, 2, 6-dimethyl pyrimi- din-4-yl, 3-methoxy-pyrazine-2-yl, 6-methoxy-pyridazin-3-yl, 4, 6-diethyl-1, 3, 5-triazin-2-yl, 5-ethyl-1, 3, 4-thiadiazol-2-yl, 5-methyl-1, 3, 4-thiadiazol-2-yl, 4-methoxy-1, 2, 5-thiadiazol-3- yl, 4-methyl-thiazol-2-yl, 3-methyl-isothiazol-5-yl, 4, 5-dime- thyl-oxazol-2-yl, 3, 4-dimethyl-isooxazol-5-yl, 4, 5-dimethyl-2- oxazolylaminoiminomethyl, 5-methyl-isooxazol-3-yl, l-phenyl- lH-pyrazol-5-yl, 4-methylamino sulphonylphenyl, 4-aminosul- phonylphenyl, 3, 4-dimethylbenzoyl, 4-isopropoxy benzoyl ; class VIII) wherein : R27 = H, 4, 6-dimethyl-pyrimidin-2-yl ; R2a = 2, 4-diamino-6-carboxyphenyl, 2, 4-diaminophenyl, 3-car- boxy-4-hydroxyphenyl ; class IX) wherein : R29 = H, OH, R30 = COOH, phenoxycarbonyl, 4- (amino) phenylsulphinyl, hydra- zinecarbonyl ; class X) (X) wherein : Ruz = amino, NH2-CH2-, benzylamino, R32 = amino, 4- (hydroxyethylamino) phenyl,-N=C (NH2) 2, 4- (amino) phenyl, 4- (aminomethyl) phenyl, 4- (carboxymethyl amino) phenyl, 4- (carboxypropionyl amino) phenyl, 2-amino- thiazol-5-yl ; class XI) (XI) wherein : M = 0, S, R52 = H, C2H5, C3H7, Rgg = amino, - NHNH2, or one of the following substituents : (XIC) (XID) (XIE) (XIF) class XII) (XII) wherein : R3, = Cl, OH ; class XIIIa) (XIIIa) wherein : R38 = H, acetyl, COC2Hs (propionyl), R39 = H, propionyl, COC3H7 (butyryl), COCH2CH(CH3)2 (isovaleryl), R40 = H, propionyl, R41 = H, or : (XIIIaB) class XIIIb) (XIIIb) wherein : R47 = H, CH3, W = CO (carbonyl),-N (CH3) CH2-, R48= H, or R48 together with W forms the bivalent radical : (XIIIbA) class XIVa) (XIVa) wherein : R42 = OH, amino, R43 = H, (R)-4-amino-2-hydroxybutyryl, (S)-4-amino-2-hydroxy- butyryl, R44 = H, OH, R45 = H, OH ; class XIVb) (XIVb) wherein : R46 =-CH20H ;-CHO Class XIVc) (XIVc) wherein : R49 = CH3, C4H9 ; class XIVd) (XIVd) wherein : R50 = H, C2H5, R51 = 3-amino-6-(aminomethyl)-3, 4-dihydro-2H-pyran-2-yl : (XIVdA) Class XIVe) (XIVe) wherein : R60 = OH, amino, RGI = H or one of the following substituents : Class XV) wherein R,, = CH3, cyclopentyl ; Class XVIa) (XVIa) wherein : Xb = N, C, R55 = H, amino, R56 = H, OH, amino, Rgy e (3-D-ribofuranosyl or 4-acetoxy-3- (acetoxymethyl) l-bu-tyl ; Class XIVb) (XVIb) wherein : R58 = H, amino, R59 = CH2OCH2CH2OH, CH2OCH(CH2OH) CH2OH, CH2OCH2CH2OCOCH (NH2)CH(CH3)2, -D-(2, 3-dideoxy) ribofura- nosyl ; Class XVII) : the following compounds : <BR> <BR> <BR> <BR> O-2-amino-2-deoxy-α-D-glucopyranosyl-(1#4)-O-[3-deoxy-3-(me -<BR> <BR> <BR> <BR> <BR> <BR> <BR> thylamino)-a-D-xylopyranosyl-(1X6)]-2-deoxy-D-streptamine (Gentamycin A), 1- (2-hydroxyethyl)-2-methyl-5-nitroimidazol (Metronidazole), (S)-2-amino-5-[(aminoiminomethyl) amino] pen- tanoic acid (Arginine), (+)-2, 2'-(ethylendiimino)di-1-buta- nol (Ethambutol), l-aminoadamantane (Amantadine), 2t, 3'-di- deoxycytidine (zalcitabine), Pyrazinamide, Morfazinamide, Acetylsulfamethoxypyrazine, Clofazimine, Cycloserine, Streptonicizid, Deoxydihydrostreptomycin, Mikamycin, Rosara- micin, Carbomycin, Alexidine, Ambazone, Cloxiquin, Nega- mycin, Nitroxoline, Porfiromycin, Taurolidine, Tibezonium iodide, Apramycin, Teicoplanin, Vancomycin, Thiabendazole, Mebendazole, Albendazole, Acranil, Anisomycin, Dimetridazole, Diminazene, Aceturate, Eflornithine, Halofuginone, Homidium, Hydroxystilbamidine, Imidocarb, Ipronidazole, Lauroguadine, Nimorazole, Oxophenarsine, Pentamidine, Phenamidine, Propamidine, Puromycin, Pyrimethamine, Quinacrine, Quinapyramine, Quintine, Secnidazole, Stilbamidine, Tinidazole.

In class I : when Rl = H, R2 OH, R3 = CH3, R4 = H, R, = (IA), the compound is known as Apicycline, when R1 = Cl, R2 = OH, R3 = CH3, R4 = H, R5 = H, the compound is known as Chlortetracycline, when Ri = Cl, R2 = OH, R3 = CH3, R4 = H, R5 = CHOH, the compound is known as Clomocycline, when Rl-Cl, R2 = OH, R3= H, R4 H, R, = H, the compound is known as Demeclocycline, when R1 = H, R2 2 = H, R3 = CH3, R4 = OH, R5 = H, the compound is known as Doxycycline, when Rl = H, R2 = OH, R3 = CH3, R4 = H, Rs = (IB), the compound is known as Guamecycline, when R1 = H, R2 = OH, R3 = CH3, R4 = H, Rs = (ID), the compound is known as Lymecycline, when Ri = Cl, R2 = free valence and with the doublet of the C-R3 bond it forms a double bond, and R3 is methylene, R4 = OH, R5= H, the compound is known as Meclocycline, when R1 = H, R2 = free valence and with the doublet of the C-R3 bond it forms a double bond, and R3 is methylene, R4 = OH, Rs= H, the compound is known as Methacycline, when R1 = dimethylamino, R2 = H, R3 = H, R4 = H, R5 = H, the compound is known as Minocycline, when R1 = H, R2 = OH, R3 = H, R4 = OH, R5 = H, the compound is known as Oxytetracycline, when R1 = H, R2 = OH, R3 = CH3, R4 = H, R5 = (IC), the compound is known as Pipacycline, when R1 = H, R2 = OH, R3 = CH3, R4 = H, Rs = H, the compound is known as Tetracycline ; when R1 = H, R2 = H, R3 = H, R4 = H, R5 = H, the compound is known as Sancycline.

In class II : when R6 = cyclopropyl, R7= H, Ra= F, R9 = (IIA) with M = H, Rlo = H, X = Y = C, the compound is known as Ciprofloxacin, when R6 = cyclopropyl, R7= H, R8= F, R9 = (IIF), R10 = Cl, X = Y = C, the compound is known as Clinaloxacin, when R6 = 4-fluorophenyl, R7= H, R8= F, R9 = (IID), R10 = H, X = Y = C, then compound is known as Difloxacin, when R6 = C2H5, R7= H, R8= F, R9 = (IIA) with M = H, Rlo = free valence, X = N, Y = C, the compound is known as Enoxacin, when R6 = cyclopropyl, R7= H, R8= F, R9 = (IIA) with M = C2H5, Rlo = H, X = Y = C, the compound is known as Enrofloxacin, when R6 = fluoroethyl, R7= H, RB= F, R9 = (IIA) with M = CH3, Rlo = F, X = Y = C, the compound is known as Fleroxacin, when R6 with Rlo forms the bivalent radical (IIM), R7 = H, R8= F, R9 = H, X = Y = C, the compound is known as Flumequine, when R6 = cyclopropyl, R7= CH3, R8= F, R9 = (IIB), R1o = H, X = Y = C, the compound is known as Grepafloxacin, when R6 = ethyl, R7= H, Ra= F, R9 = (IIB), R10 = F, X = Y = C, the compound is known as Lomefloxacin, when R6 with Rio forms the bivalent radical (IIM), R7= H, R8= F, R9 = (IIE) with Tl = OH, X = Y = C, the compound is known as Nadifloxacin, when R6 = C2H5, R7= H, R8= H, R9 = CH3, R10 = free valence, X = N, Y = C, the compound is known as Nalidixic acid, when R6 = C2H5, R, = H, R8= F, R, = (IIA) with M = H, Rlo = H, X = Y = C, the compound is known as Norfloxacin, when R6 with Rio forms the bivalent radical (IIN), R7= H, R8= F, R9 = (IIA) with M = CH3, X = Y = C, the compound is known as Ofloxacin, when R6 = C2H5, R, = H, R8 and Rg form the bivalent radical (IIP), R10 = H, X = Y = C, the compound is known as Oxolinic acid, when R6 with Rio forms the bivalent radical (IIO), R7 H, Ra= F, R9 = (IIH), X = Y = C, the compound is known as Pazufloxacin, when R6 = ethyl, R7= H, R8= F, R9 = (IIA) with M = CH3, R1o = H, X = Y = C, the compound is known as Pefloxacin, when R6 = C2Hs, R7= H, R8= free valence, R9 = (IIA) with M = H, Rio = free valence, X = Y = N, the compound is known as Pipemidic acid, when R6 = C2H5, R7 = H, R8= free valence, Rg = (IIE) with T = H, R10 = fre valence, X = Y = N, the compound is known as Piromidic acid, when R6 with Rlo forms the bivalent radical (IIQ), R7= H, R8 = F, R9 = (IIA) with M = CH3, X = Y = C, the compound is known as Rufloxacin, when R6 = cyclopropyl, R7= amino, R8= F, Rg = (IIC), Rio F, X = Y = C, the compound is known as Sparfloxacin, when R6 = 2, 4-difluorophenyl, R7= H, R8= F, R9 (IIF), Rio = free valence, X = N, Y = C, the compound is known as Tosufloxacin, when R6 = 2, 4-difluorophenyl, R7= H, R8= F, Rg = (IIG), Rio = free valence, X = N, Y = C, the compound is known as Trovafloxacin, when R6 = cyclopropyl, R7= H, Re = F, R9 = (IID), Rlo = H, X = Y = C, the compound is known as Danofloxacin, when R6 = 4-fluorophenyl, R7 = H, R8 = F, Rg = (IIA) with M = H, R10 = H, X = Y = C, the compound is known as Sarafloxacin.

In class IIIa : when R11 = H, R12= Cl, R13 = amino, R14 = phenyl, Z = S, the compound is known as Cefaclor, when R11 = H, R12 = CH3, R13 = amino, R14 = 4-hydroxyphenyl, Z = S, the compound is known as Cefafroxil, when Rii = (IIIaB), R13 = amino, R14 = 4- hydroxyphenyl, Z = S, the compound is known as Cefatrizine, when R11 = H, R12=(IIIaC), R13 = (IIIaD), R14 = 4-hy- droxyphenyl, Z = S, the compound is known as Cefpiramide, when Rll = H, R12 = 2-propenyl, Rl3 = amino, Rl4 = 4-hy- droxyphenyl, Z = S, the compound is known as Cefprozil, when Rll = H, R12 = CH3, R13 = amino, R14 = (IIIaE), Z = S, the compound is known as Cefroxadine, when R11 = H, R12 = CH3, R13 = amino, R14 = phenyl, Z = S, the compound is known as Cephalexin, when R11 = H, R12 = CH3, R13 = (IIIaF) with T2 = CH3, R14 = phenyl, Z = S, the compound is known as Cephaloglycin, when Ri. = H, R12 = CH3, R. = amino, R = (IIIaE), Z = S, the compound is known as Cephadrine, when R11 = H, R12 = Cl, R13 = amino, R14 = phenyl, Z = C, the compound is known as Loracarbef, when Rll = (IIIaF) with T2 = tert-butyl, R12 = CH3, R13 = amino, R14 = phenyl, Z = S, the compound is known as Pivcefalexin, when Rll = H, R12 = (IIIaC), Rl3 = OH, R14 = phenyl, Z = S, the compound is known as Cefamandole.

In class IIIb : when R1s = (CH3) 3CCOOCH2OCO-, R16= NH2COOCH2-, R17 = C2H5, X = CH, Y = C, the compound is known as Cefcapene Pivoxil, when R15 = COO@, R16 = (IIIbL), R17 = methoxyl, X = Y = N, the compound is known as Cefclidin, when R,, = COOH, R16 = -CH=CH2, R17 = OH, X = N, Y = C, the compound is known as Cefdinir, when R15 = COOH, R16 = (IIIbA), R17 = OCH3, X = N, Y = C, the compound is known as Cefditoren, when Rls = COO-, R16 = (IIIbM), R17 = OCH3, X = N, Y = C, the compound is known as Cefepime, when Rls = COOH, Rls = CH3, R17 = OCH3, X = N, Y = C, the compound is known as Cefetamet, when Rls = COOH, Rls =-CH=CH2, Rl., =-OCH2OCOOH, X = N, Y = C, the compound is known as Cefixime, when R15 = COOH, R16 = (IIIbC), R17 = OCH3, X = N, Y = C, the compound is known as Cefmenoxime, when R15 = COO@, R16 = (IIIbN), R17 = OCH3, X = Y = N, the compound is known as Cefozopran, when R15 = (CH3)2CHOCOOCH(CH3)OCO-, R16 = C2H5, R17 = OCH3, X = N, Y = C, the compound is known as Cefpodoxime Proxetil, when R15 = COOH, R16 = (IIIbD), Rl7 = OCH3, X = N, Y = C, the compound is known as Cefteram, when Rls = COOH, R16 = H, R17 = -CH2COOH, X = CH, Y = C, the compound is known as Ceftibuten, when R15 = COOH, R16 = (IIIbH), R17 = OCH3, X = N, Y = C, the compound is known as Ceftriaxone, when Rls = COOH, Rl, = (IIIbE), R17 = OCH3, X = N, Y = C, the compound is known as Cefuzonam, when R15 = COOH, R16 = (IIIbF), R17 = OCH3, X = N, Y = C, the compound is known as Cefodizime, when Ris = COOH, R16 = CH3COOCH2-, R17 = OCH3, X = N, Y = C, the compound is known as Cefotaxime, when Rls COOH, R16 = (IIIbG), R17 = OCH3, X = N, Y = C, the compound is known as Ceftiofur.

In class IIIc : when R13 = (IIIcD), RI, = (IIIcH), the compound is known as Cefotiam, when R18 = (IIIcE), R19 = H, the compound is known as Ceftizoxime, when Rig = (IIIcF), Rl9 = (IIIcN), the compound is known as Cefazolin, when Rl, = (IIIcG), Rl9 = (IIIcM), the compound is known as Ceforanide, when Rig = (IIIcA), Rl9 = (IIIcL), the compound is known as Cefminox, when Rla = (IIIcB), Rl9 = CH3COOCH2-, the compound is known as Cephalosporin C.

In Class IVa : when R20 = (IVaF) and R21 = H, the compound is known as Amdinocillin, when R20 = (IVaF) and Ri = (IIIaF) with T2 = tert-butyl, the compound is known as Amdinocillin Pivoxil, when R20 = (IVaA) and R21 = H, the compound is known as Amoxicillin, when R20 = (IVaB) and R21 = H, the compound is known as Ampicillin, when R20 = (IVaM) and R2, H, the compound is known as Apalcillin, when R20 = (IVaG) and R21 = H, the compound is known as Aspoxicillin, when R20 = (IVaB) and R21 = -CH(CH3)OCOOC2H5, the compound ia known as Bacampicillin, when R20 = (IVaE) and R21 = H, the compound is known as Cyclacillin, when R2o = (IVaC) and R21 = H, the compound is known as Epicillin, when R2o = (IVaC) and R,, = H, the compound is known as Hetacillin, when R2o- (IVaC) and R2, = (IVaS), the compound is known as Lenampicillin, when R20 (IVa) and R21 H, the compound is known as Mezlocillin, when R20 = (IVaD) and R2, = (IVaR), the compound is known as Penethamate Hydroiodide, when R20 = (IVaP) and R21 = H, the compound is known as Penicillin N, when R20 = (IVaB) and R21 = (IIIaF) with T2 = tert-butyl, the compound is known as Pivampicillin, when R20 = (IVaN) and R21 = H, the compound is known as Quinacillin, when R20 = (IVaB) and R,, = (IVaU), the compound is known as Sultamicillin, when R20 = (IVaB) and R,, = (IVaT), the compound is known as Talampicillin.

In class IVb : when R22 = CH3, R23 = (IVbA), the compound is known as Meropenem, when R22 = H, R23 = (IVbC), the compound is known as Panipenem, when Rgs 22 = H, R23 = (IVbD), the compound is known as Imipenem.

In class IVc : when R33 = CH3 , R34 = CH3, R35 = H, R36 = CH3, the compound is known as Aztreonam, when R33 = H, R34 = H, R35 = -CH2OCONH2, R36 = H, the compound is known as Carumonam.

In class V : when R24 = Br, the compound is known as Brodimoprim, when R24 = OCH3, the compound is known as Trimethoprim, when R24 CH30CH2CH20-, the compound is known as Tetroxoprim.

In class VI : when R25 = (VID) the compound is known as Furaltadone, when R2s = (VIC) the compound is known as Furazolium chloride, when R21 = (VIE) the compound is known as Nifurfoline, when R25 = (VIA) the compound is known as Nifurpirinol, when R21 = (VIE) the compound is known as Nifurprazine.

In class VII : when R26 = H, the compound is known as Sulfanilamide, when R26 benzoyl, the compound is known as Sulfa- benzamide, when R26 acetyl, the compound is known as Sulfa- cetamide, when R26 3-methyl-2-butenoyl, the compound is known as Sulfadicramide, when R26 carbamoyl, the compound is known as Sulfa- nilylurea, when R26 NH2C (S)-, the compound is known as Sulfa- thiourea, when R26 2-pyridinyl, the compound is known as Sulfa- pyridine, when R26 pyrazinyl, the compound is known as Sulfa- pyrazin, when R26 2-pyrimidinyl, the compound is known as Sulfa- diazine, when R26 = 2-thiazolyl, the compound is known as Sulfa- thiazole, when Rz = salicyl-4-yl, the compound is known as 4- sulphanilamido salicylic acid, when R26 = 6-chloro-pyridazinyl-3-yl, the compound is known as Sulfachlorpyridazine, when R26 = 1-ethyl-1, 2-dihydro-2-oxo-pyrimidin-4-yl, the compound is known as Sulfacytine, when R26 = 5, 6-dimethoxy-pyrimidin-4-yl, the compound is known as Sulfadoxine, when R26-2, 6-dimethoxy-pyrimidin-4-yl, the compound is known as Sulfadimethoxine, when R26 4-methyl-pyrimidin-2-yl, the compound is known as Sulfamerazine,. when R26 = 5-methoxy-pyrimidin-2-yl, the compound is known as Sulfameter, when R26 = 4, 6-dimethyl-pyrimidin-2-yl., the compound is known as Sulfamethazine when R26 = 6-methoxy-2-methyl-pyrimidin-4-yl, the compound is known as Sulfamethomidine, when R26 = 5-methyl-pyrimidin-2-yl, the compound is known as Sulfaperine, when R26 = 2, 6-dimethylpyrimidin-4-yl, the compound is known as Sulfisomidine, when R26 3-methoxy-pyrazin-2-yl, the compound is known as Sulfalene, when R26 = 6-methoxy-pyridazin-3-yl, the compound is known as Sulfamethoxypyridazine, when R26 = 4, 6-diethyl-1, 3, 5-triazin-2-yl, the compound is known as Sulfasymazine, when R26 = 5-ethyl-1, 3, 4-thiadiazol-2-yl, the compound is known as Sulfaethidole, when R26 = 5-methyl-1, 3, 4-thiadiazol-2-yl, the compound is known as Sulfamethizole, when R26 = 4-methoxy-1, 2, 5-thiadiazol-3-yl, the compound is known as Sulfametrole, when R26 = 4-methyl-thiazol-2-yl, the compound is known as Sulfamethylthiazole, when R26 = 3-methyl-isothiazol-5-yl, the compound is known as Sulfasomizole, when R26 = 4, 5-dimethyl-oxazol-2-yl, the compound is known as Sulfamoxole, when R,, = 3, 4-dimethy-isoxazol-5-yl, the compound is known as Sulfisoxazole, when R26 = 4, 5-dimethyl-2-oxazolylaminoiminomethyl, the compound is known as Sulfaguanol, when R26 = 5-methyl-isoxazol-3-yl, the compound is known as Sulfamethoxazole, when R26 = 1-phenyl-1H-pyrazol-5-yl, the compound is known as Sulfaphenazole, when R26 = 4-methylamino sulphonylphenyl, the compound is known as 4'-(methylsulfamoyl) sulfanilanilide, when R26 = 4-aminosulphonylphenyl, the compound is known as N4 sulfanilylsulfanilamide, when R26 = 3, 4-dimethylbenzoyl, the compound is known as N-sulfanyl-3, 4-xylamide, when R26 = 4-isopropoxybenzoyl, the compound is known as Sulfaproxyline.

In class VIII : when R27 = H, R28 = 2, 4-diamino-6-carboxyphenyl, the compound is known as Sulfachrysoidine, when R27 = H, R28 = 2, 4-diaminophenyl, the compound is known as Sulfamidochrysoidine, when R27 = 4, 6-dimethyl-pyrimidin-2-yl, R23 = 3-carboxy-4- hydroxyphenyl, the compound is known as Salazo sulfadimidine.

In class IX : when R29 = OH, R30 = COOH, the compound is known as p- Aminosalicylic acid, when R29 = OH, R30 = hydrazinecarbonyl, the compound is known as p-Aminosalicylhydrazide, when R29 = OH, R30 = phenoxycarbonyl, the compound is known as Phenylaminosalicylate, when R29 = H, R30 = 4- (amino) phenylsulphinyl, the compound is known as 4, 4'-Sulphinyldianiline.

In class X : when R31 = amino, R32 = 4-(hydroxyethylamino) phenyl, the compound is known as 2-p-Sulfanilylanilino ethanol, when R31 = amino, R32 = -N=C(NH2)2, the compound is known as Sulfaguanidine, when R31 = NH2-CH2-, R32 = amino, the compound is known as Mafenide, when R31 = benzylamino, R32 = amino, the compound is known as Benzylsulfamide, when R31 = amino, R32 = 4-(carboxymethylamino) phenyl, the compound is known as Acediasulfone, when R31 = amino, R32 = 4-(amino) phenyl, the compound is known as Dapsone, when R31 = amino, R32 = 4-(carboxypropionylamino) phenyl, the compound is known as Succisulfone, when R31 = amino, R32 = 4-(aminomethyl) phenyl, the compound is known as p-Sulfanilylbenzylamine, when R3 = amino, R32 = 2-amino-thiazol-5-yl, the compound is known as Thiazolsulfone.

In class XI : when R52 = C2H5, R53 = amino, M = S, the compound is known as Ethionamide, when R52 H, R53--NHNH2, M = O, the compound is known as Isoniazid, when R52 = C3H7, R53 = amino, M = S, the compound is known as Protionamide, when R52 = H, R53 = (XIA), M = O, the compound is known as Sulfoniazide, when R52 = H, R53 = (XIB), M = O, the compound is known as Verazide, when R52 = H, R53 = (XIC), M = O, the compound is known as Opiniazide, when R52 = H, R53 = (XID), M = O, the compound is known as Salinazid, when R52 = H, R53 = (XIE), M = O, the compound is known as Furonazide, when R52 = H, R53 = (XIF), M = O, the compound is known as Glyconiazide.

In class XII : when R37 = Cl, the compound is known as Clindamycin, when R37 = OH, the compound is known as Lincomycin.

In class XIIIa : when R38 = acetyl, R39 = isovaleryl, R40 = H, R41 = H, the compound is known as Josamycin, when R311 = propionyl, R39 = propionyl, R40 = H, R41 = H, the compound is known as Midecamycin A1, when R38 = H, R39 = butyryl, R40 = propionyl, R41 = H, the compound is known as Rokitamycin, when R38 = H, R39 = H, R40 = H, R41 = (XIIIaB), the compound is known as Spiramycin I, when R38 = acetyl, R39 = H, R40 = H, R41 = (XIIIaB), the compound is known as Spiramycin II, when R38 = propionyl, R39 = H, R40 = H, R41 = (XIIIaB), the compound is known as Spiramycin III, when R38 = H, R39 = isovaleryl, R40 = H, R41 = H, the compound is known as Leucomycin.

In class XIIIb : when R47 = H, R48 = H, W =-N (CH3) CH2-, the compound is known as Azithromycin, when R47 = CH3, R48 = H, W = carbonyl, the compound is known as Clarithromycin, when R47 = H, R48 = H, W = carbonyl, the compound is known as Erythromycin, when R47 = H, R48 and W form together (XIIIbA), the compound is known as Dirithromycin.

In class XIVa : when R42 = OH, R43 = (S)-4-amino-2-hydroxybutyryl, R44 = OH, R4, = OH, the compound is known as Amikacin, when R42 = amino, R43 = (R)-4-amino-2-hydroxy butyryl, R44 = H, R45 = H, the compound is known as Arbekacin, when R42 = amino, , R43 = H, R44 = H, R45 = H, the compound is known as Dibekacin, when R42. = amino, R43 = H, R44 = OH, R45 = H, the compound is known as Tobramycin.

In class XIVb : when R46-CH, OH, the compound is known as Dihydrostreptomycin, when R46 =-CHO, the compound is known as Streptomycin.

In class XIVc : when R49 = CH3, the compound is known as Spectinomycin, when R49 = C4Hg, the compound is known as Trospectomycin.

In class XIVd : when R50 = H, R51 = (XIVdA), the compound is known as Micronomicin, when R50 = C2H5, R51 = 3-amino-6-(aminomethyl)-3, 4-dihydro- 2H-pyran-2-yl, the compound is known as Netilmicin, when R50 = H, R51 = 3-amino-6- (aminomethyl)-3, 4-dihydro-2H- pyran-2-yl, the compound is known as Sisomicin.

In class XIVe : when R60 = amino, R61 = (XIVeA) the compound is known as Neomycin, when R60 = OH, R61 = (XIVeB) the compound is known as Paromycin, when R60 = amino, R61 = H, the compound is known as Ribostamycin.

In class XV : when R,, = CH3, the compound is known as Rifampin, when Rs4 = cyclopentyl, the compound is known as Rifapentine.

In class XVIa : when Xb = N, R55 = H, R56 = OH, R57 = -D-ribofuranosyl, the compound is known as Inosine, when Xb = N, R55 = amino, R56 = H, R57 = 4-acetoxy-3- (acetoxymethyl) 1-butyil, the compound is known as Famcy- clovir, when Xb = C, R55 = H, R56 = amino, R57 = -D-ribo- furanosyl, the compound is known as Tubercidin.

In class XVIb : when R58 = H, R59 = -D-(2, 3-dideoxy) ribo furanosyl, the compound is known as Didanosine, when Rs8 = amino, Rsg = CH20CH2CH20H, the compound is known as Acyclovir, when R58 = amino, R59 = CH2OCH2CH2OCOCH(NH2) CH (CH3) 2, the compound is known as Valacyclovir, when R58 = amino, R59 = CH2OCH(CH2OH)CH2OH, the compound is known as Gancyclovir.

The following compounds are preferred : In class I : when R1 = H, R2 = H, R3 = CH3, R4 = OH, Rs = H, the compound is known as Doxycycline, when R1 = H, R2 = OH, R3 = H, R4 OH, Rg = H, the compound is known as Oxytetracycline, when R1 = H, R2 2 = OH, R3 = CH3, R4 = H, R5 = H, the compound is known as Tetracycline.

In class II : when R6 = cyclopropyl, R7= H, R8= F, R9 = (IIA) with M = H, Rio = H, X = Y = C, the compound is known as Ciprofloxacin, when R6 = C2Hs, R7= H, Re= H, Rg = CH3, Rlo = free valence, X = N, Y = C, the compound is known as Nalidixic acid, when R6 = C2H5, R, = H, R8= F, R, = (IIA) with M = H, Rlo = H, X = Y = C, the compound is known as Norfloxacin, when R6 with R10 form the bivalent radical (IIN), R. H, R, = F, R9 = (IIA) with M = CH3, X = Y = C, the compound is known as Ofloxacin.

In class IIIa : when Ri. = H, R12= Cl, R13 = amino, R14 = phenyl, Z = S, the compound is known as Cefaclor, when R11 = H, R12= CH3, R13 = amino, R14 = phenyl, Z = S, the compound is known as Cephalexin, when Ril = H, R12= (IIIaC), R13 = OH, R14 = phenyl, Z = S, the compound is known as Cefamandole.

In class IIIb : when Ri. = COOH, R16= ethenyl, RI, = -OCH2OCOOH, X = N, Y = C, the compound is known as Cefixime, when R1s = (CH3) 2CHOCOOCH (CH3)OCO-, R16= C2H5, R17 = OCH3, X = N, Y = C, the compound is known as Cefpodoxime Proxetil, when Rls = COOH, R16= (IIIbF), RI, = OCH3, X = N, Y = C, the compound is known as Cefodizime.

In class IIIc : when Ri. = (IIIcF), R19 = (IIIcN), the compound is known as Cefazolin.

In class IVa : when R20 = (IVaA) and R21 = H, the compound is known as Amoxicillin, when R20 = (IVaB) and R21 = H, the compound is known as Ampicillin, when R20 (IVaM) and R21 = H, the compound is known as Apalcillin.

In class IVb : when R22 = H, R23 = (IVbD), the compound is known as Imipenem.

In class IVc : when R33 = CH3, R34 = CH3, R35 = H, R36 = CH3, the compound is known as Aztreonam.

In class V : when R24 = OCH3, the compound is known as Trimethoprim.

In class VI : when R25 = (VIE) the compound is known as Nifurfoline.

In class VII : when R26 = 5-methyl-isoxazol-3-yl, the compound is known as Sulfamethoxazole.

In class X : when R31 = amino, R32 = 4-(amino) phenyl, the compound is known as Dapsone.

In class XI : when R52 = C2H5, R53 = amino, M = S, the compound is known as Ethionamide ; when R52 = H, R53 = -NHNH2, M 0, the compound is known as Isoniazid.

In class XIIIb : when R47 = H, R48 = H, W = -N(CH3)CH2-, the compound is known as Azithromycin, when R47 = H, R48 = H, W = carbonyl, the compound is known as Erythromycin, when R47 = CH3, R48 = H, W = carbonyl, the compound is known as Clarithromycin.

In class XIVa : when R42 = OH, R43 = (S)-4-amino-2-hydroxybutyryl, R44 = OH, R45 = OH, the compound is known as Amikacin, when R42 = amino, R43 = H, R44 = OH, R45 = H, the compound is known as Tobramycin.

In class XIVb : when R46 =-CHO, the compound is known as Streptomycin.

In class XIVc : when R49 = CH3, the compound is known as Spectinomycin.

In class XIVd : when R50 = C2H5, R51 = 3-amino-6-(aminomethyl)-3, 4-dihydro- 2H-pyran-2-yl, the compound is known as Netilmicin.

In class XIVe : when R60 = amino, R6l = (XIVeA) the compound is known as Neomycin.

In class XV : when R. 4 = CH3, the compound is known as Rifampin.

In class XVIa : when Xb = N, Rss = H, RSG = OH, R17 = (3-D-ribofuranosyl, the compound is known as Inosine, when Xb = N, R55 = amino, R56 = H, R57 = 4-acetoxy-3- Cacetoxymethyl) 1-butyl, the compound is known as Famcyclovir.

In class XVIb : when Rs8 = H, Rsg = -D-(2, 3-dideoxy) ribo furanosyl, the compound is known as Didanosine, when Rs8 = amino, Rsg = CH20CH2CHzOH, the compound is known as Acyclovir, when R58 = amino, R59 = CH2OCH2CH2OCOCH(NH2) CH (CH3) the compound is known as Valacyclovir, when RS = amino, Rsg = CH20CH (CHzOH) CH2OH, the compound is known as Gancyclovir.

In class XVII : <BR> <BR> <BR> <BR> 0-2-amino-2-deoxy-a-D-glucopyranosyl- (1-44)-0- 3-deoxy-3-<BR> <BR> <BR> <BR> <BR> <BR> (methylamino)-α-D-xylopyranosyl-(1#6)]-2-deoxy-D-streptamin e (Gentamycin A), (S)-2-amino-5-[(aminoiminomethyl) amino] pen- tanoic acid (Arginine), (+)-2, 2l-(ethylendiimino) di-l-butanol (Ethambutol), 1-amino adamantan (Amantadine), 2', 3'-dideoxy- cytidine (zalcitabine), Pyrazinamide, Morphazinamide, Teico- planin, Vancomycin, Metronidazole.

A further object of the invention are also the nitrate salts compounds of antimicrobial, preferably antiviral, antifungal and antibacterial agents, or their pharmaceutical compositions, for the preparation of medicaments, excluding the nitrate salts of Erythromycin, Isoniazid, Pyrazinamide, Metronidazole, Acyclovir.

In the present invention can be used also the nitrate salts of the corresponding nitrooxy derivatives of the above listed antimicrobic agents, said nitrooxy derivatives characterized in that in their molecules there are one or more, preferably one, substituents having the general formula (I-N) <BR> <BR> <BR> <BR> -B-(W) p-ONO2<BR> <BR> <BR> <BR> <BR> (I-N) wherein : p is 1 or 0 ; B =-TB-Y-TBI-wherein TB e TBI are same or different ; TB is a chemical function covalently linked to the chemical or reactive function of the drug molecule and is (CO) or X, wherein X = O, S, NH, with the condition that X = (CO) when the reacting function of the drug is OH or NH2 or SH ; TB is X when the reacting function of the drug is a carboxyl group ; TBI = (CO) tX or (X) t., wherein tx and txx are 0 or 1 ; with the condition that tx = 1 when txx = 0, tx = 0 when txx = 1 ; X is as above defined ; Y is a bivalent linking bridge chosen between the following structures : (II-Y) wherein : nIX is an integer comprised between 0 and 3, preferably is 1 ; nIIX is an integer comprised between 0 and 3, preferably is 1 ; RTIX@, RTIIX, RTIIX', same or different each from the other, are H or linear or branched Cl-C4 alkyl ; preferably RTIX' RTIX', RTIIX, RTIIX' are H.

Y3 is a ring containing at least one salifiable nitrogen atom ; preferably Y is an heterocyclic ring containing one or two nitrogen atoms, the ring saturated, unsaturated or aromatic, having preferably 5 or 6 atoms.

An alkylene group R'wherein R'is a linear or branched C1-C20 alkyl, preferably a C2-C6 alkyl, optionally substituted with one or more of the following groups : -NHCOR3y, wherein R3Y is a linear or branched Ci-Cg alkyl, ~NH2,-OH ; A cycloalkylene ring C5-C7, optionally substituted with R', being R'as above defined, wherein one or more C atoms of the cycloalkylene can be optionally substituted with heteroatoms ; (III-Y) wherein n3 is an integer from 0 to 3 and n3'is an integer from 1 to 3 ; (IV-Y) wherein n3 and n3'have the meanings above indicated ; (V-Y) wherein : R4y is OH, H, alcoxy R5YO- wherein R5Y is a linear or branched or cyclo Ci-Cn, alkyl, preferably R, y is methyl ; R, y is a linear or branched alkenylene C2-C10 containing one or more double bonds, preferably R2Y is an ethenylene group (-CH=CH-) ; wherein Rlf = H, CH3 and nf is an integer from 0 to 6 ; preferably from 0 to 4 ; W of formula (I-N) is the bivalent radical-Tc-YT-wherein : Tc = (CO) when tx = 0, Tc = X when txx= 0 ; with the proviso that in formula (I-N) when p = 1 YT is different from Y and in the bivalent radical B : -Y is R' as above defined having a substituent NHCOR3Y, preferably R'is a C2 saturated alkyl and R3y is CH3 ; TB = S ; TB1 is-CO- ; preferably Y is -CH2-CH (NHCOCH3) - and B in formula (I-N) preferably has the following structure : (X-Y) Y is a bivalent radical of formula (V-Y), wherein R4y is OR, y and R, y is preferably CH3, R2y is the group-CH=CH- ; preferably Y has the following formula (XI-Y) Preferably Y3 in formula (II-Y) is selected from the following bivalent radicals : (Y7) (Y8) (Y9) (Y10) (Y11) (Y12) (Y13) (Y14) (Y15) Preferably Y3 is a 6-membered aromatic ring containing one nitrogen atom, said ring having the two free valences in the following positions : 2, 6 ; 2, 3 ; 2, 5.

The preferred of Y3 is Y12 (pirydil) substituted at positions 2 and 6.

Y1 (pyrazole) can be 3, 5-disubstituted.

A further object of the present invention are the nitrate salts of the nitrooxy derivatives of the antimicrobial above listed compounds, preferably having antiviral, antifungal and antibacterial activity, or their pharmaceutical compositions, for the preparation of medicaments, excluding the nitrate salts of the nitrooxy derivatives of Erythromycin, Isoniazid, Pyrazinamide, Metronidazole, Acyclovir when in formula (I-N) p = 0.

The derivatives of antibacterial agents having in their molecules one or more of the substituents of formula (I-N) can be prepared according to methods known in the art.

In general, if in the molecule of the drug, or in the bivalent radicals B or W of formula (I-N) there are more than one reactive groups COOH and/or HX, X being as above defined, said reactive groups must be protected before the reaction according to the methods known in the art ; for example as described in the volume by Th. W. Greene :"Protective groups in organic synthesis", Harward University Press, 1980.

Acyl halides are prepared according to the methods known in the prior art, for example by thionyl or oxalyl chloride, pIII or pv halides in inert solvents under the reaction conditions, such as for example toluene, chloroform, DMF, etc.

1) When the reactive chemical function of the drug is a carboxyl group and p = 0 in formula (I-N), the corresponding nitrooxy derivatives can be prepared by the following methods : l. a) The acid RCOOH (wherein R is the drug radical) and an halogen alcohol derivative of formula HO-Y-Hal, wherein Y is as above defined and Hal is an halogen atom, for example Cl, Br, Iodine, may be coupled to produce the ester of formula (1/C) by treatment with a de-hydrating agent such as N, NI-carbonyldiimidazol (CDI), N-hydroxy- benzotriazol, and dicyclohexylcarbodiimide (DCC) in the presence of a condensation catalyst such as 4- dimethylaminopyridine (DMAP), in a solvent such as for example DMF, THF, chloroform etc. at a temperature in the range from-5°C to 50°C.

CDI, HO-Y-Hal l. b) Alternatively the acid RCOOH may first be converted into an alkali metal salt such as sodium or potassium salt and reacted with a dihalogenated derivative of general formula Y (Hal) 2, wherein Y and Hal are as above defined.

R-COONa + Hal-Y-Hal--------> R-CO-O-Y-Hal (1/B) l. c) Alternatively the acid may first be converted to the acyl chloride of formula R-CO-C1 (wherein R is the drug radical) and then is reacted with an halogeno alcohol of formula HO-Y-Hal or a diol of formula HO-Y-OH, wherein Y is as above defined and Hal is halogen (Cl, Br, I) : 1. d) The acid RCOOH and a dihalogenide compound of formula Hal-Y-Hal, wherein Y and Hal are as above defined, may be coupled to form an ester in the presence of a base, in an organic solvent inert in the reaction conditions according to the following scheme : l. e) When the compounds obtained in the herein above described reactions have formula R-COO-Y-Hal, the corresponding nitrooxyderivatives are obtained by reacting the compound R-CO-O-Y-Hal with AgNO3 in an organic solvent such as acetonitrile, tetrahydrofuran according to the following scheme : l. f) When the compounds obtained in the herein above described reactions have the formula R-COO-Y-OH, the hydroxy group is firstly halogenated, for instance by means of PBrs, PCls, SOC12, PPh3 + I2, then reacted with AgNO3 in an organic solvent such as acetonitrile, tetrahydrofuran.

2) When in formula (I-N) p = 0, and the free valence of R is saturated with an hydroxy group, the methods of synthesis of the corresponding nitrooxy derivatives are the following : 2. a) The drug of formula R-OH and an halogenoacid of formula Hal-Y-COOH or an hydroxyacid of formula HO-Y-COOH, wherein Y and Hal are as above defined, may be coupled according to the reactions known in the art to produce the esters of formula (2/A) or (2/B), according to the following schemes : R-OH + Hal-Y-COC1 R-OCO-Y-Hal (2/A) R-OH + Hal-Y-COC1-----+ R-OCO-Y-OH (2/B) 2. b) When the compounds obtained in the herein above described reactions have the formula R-OCO-Y-Hal or R-OCO-Y-OH, the corrresponding nitrooxy derivatives are obtained as described in l. f and l. e respectively.

3. When in formula (I-N) p = 1 and the reactive group of the drug molecule is a carboxyl group, the methods of synthesis for obtaining the corresponding nitrooxy derivatives are the following ones : 3. a) The drug of formula RCOOH may first be converted to the acyl chloride of formula R-CO-Cl (wherein R is the drug radical) and then is reacted with a compound of formula HX-Y-COOH according to the methods known in the art, to obtain a compound of formula R-CO-X-Y-COOH, that it is converted into the corresponding sodium salt and then reacted with a compound of formula Hal-YT-R8y wherein Hal e YT are as above defined and REY is Cl, Br, Iodine, OH : When Rgy = OH, the compound of formula (3. A') is halogenated as above described in l. f) ; when Ray = Hal the compound of formula (3. A') is reacted with AgNO3 in an organic solvent such as acetonitrile, tetrahydrofuran : 3. b) When YT is a linear alkylene C4, the acid compound of formula (3. A) is reacted with triphenylphosphine in the presence of an halogenating agent such as CBr4 or N-bro- mosuccinimide in tetrahydrofuran to give directlythe compound of formula (3. A') wherein R8y = Br, said compound is then converted into the corresponding nitrooxy derivative as described under l. e.

4) When in formula (I-N) p = 1 and the reactive group of the antibacterian drug is an hydroxy group, the methods of synthesis for obtaining the corresponding nitrooxy derivatives are the following ones : 4. a) The drug of formula R-OH and an acyl halogenide of formula HX-Y-COHal wherein Y, X and Hal are as above defined, may be coupled according to the methods known in the art to produce the ester of formula of formula R-O- CO-Y-XH (4/A), that is then reacted with a compound of formula Rey-YT-COHal wherein RaY and YT are as above defined.

4. b) Alternatively, the drug R-OH is reacted with a compound of formula HX-Y-COOH, wherein X and Y are as above defined, in the presence of dicyclohexylcarbodiimide as described under l. a, to obtain a compound of formula R-O- CO-Y-XH, that is then reacted with a compound of formula ReY-YT-COC1 wherein R8y and YT are as above defined, to give the following compound : R-O-CO-Y-X-CO-YT-RSy (4/B) When R8y = OH the compound corresponding to the formula (4/B) or (4a') is halogenated as above described under l. f) ; when R8 = Hal the compound of formula (4/B) is reacted with AgNO3 in an organic solvent such as acetonitrile, tetrahydrofuran.

The nitrooxy derivatives of the antibacterian agent can also by prepared according to the synthetic methods described in WO 95/30641 herein incorporated by reference.

In the salts or their compositions according to the present invention also one or more isomers, including optical isomers, when possible, of the above described antimicrobial compounds can be used.

The nitrate salts according to the present invention contain at least one nitrate ion mole/compound mole.

Preferably the ratio nitrate ion moles/precursor moles is unitary. Salts having a higher molar ratio are obtained when in the molecule more aminic groups, sufficiently basic to be able to be salified, are present.

The salts of the present invention are formulated in the corresponding pharmaceutical compositions according to well known techniques in the prior art, together with the usual excipients ; see for example the volume"Remington's Pharmaceutical Sciences 15a Ed." The precursors of the salts belonging to the above mentioned classes are prepared according to the methods described in the Merck Index 14a Ed., herein incorporated by reference.

The nitrate salts of the antibacterial compounds are prepared by the following methods.

When the compound to be salified is available as free base soluble in an organic solvent, which preferably does not contain hydroxyl groups, for example acetonitrile, ethyl acetate, tetrahydrofuran, etc., the salt is prepared by dissolving the compound in the solvent at a concentration preferably equal to or higher than 10% w/v, adding the amount of concentrated nitric acid corresponding to the moles of salifiable aminic groups present in the compound. The nitric acid is preferably diluted in the same solvent. Preferably during and after the addition it is cooled at temperatures in the range 0°C-20°C.

The product is generally recovered by filtration and washed with the solvent.

When the compound is not very soluble, or it is available under the form of a not very soluble salt in the above mentioned solvents, the corresponding mixtures with hydroxylated solvents can be used. Examples of such solvents are methyl alcohol, ethyl alcohol and water. The precipitation of the nitrate salt can be accelerated by diluting then the so obtained mixture, after the addition of nitric acid, with an apolar solvent.

When the starting compound is salified with hydrochloric acid, it is possible to prepare the nitrate salt by directly adding silver nitrate to the compound solution. After having filtered the silver chloride, the solution is concentrated and cooled for recovering the nitrate salt.

When the starting compound is a salt, the corresponding base can also be released by treatment with a saturated solution of sodium or potassium bicarbonate or carbonate, or with a diluted solution of sodium or potassium hydroxide. The base is then extracted with a suitable organic solvent (for example halogenated solvents, esters, ethers), which is then dried. The organic solution is evaporated and one proceeds according to the previous preparation methods, by dissolving the base in acetonitrile or in the other above mentioned solvents.

The compounds and compositions of the present invention can be used for systemic applications, for example they can be administered by os with formulations known in the prior art such as for example tablets or capsules, or by parenteral route, such as for example by intravenous or intramuscular administration in formulations in sterile apyrogenic physiological solution, optionally additioned with other excipients known in the prior art.

It is possible to use the nitrate salts of the present invention for topical applications, under the form of gels or creams, or by aerosol (by inhalation).

As said, the compounds of the invention are used in the therapy of the same pathologies for which the precursor antimicrobial agents ar used. However since the products of the invention show an improved activity, they can be used even at lower doses. This is advantageous since it allows to avoid the side effects mentioned above for precursors.

The following Examples are given with the only purpose to illustrate the invention and they are not limitative of the same.

EXAMPLES Preparation Examples EXAMPLE 1 Preparation of the Cefalexine nitrate salt A solution of Cefalexine hydrochloride (3 g, 13. 02 mmoles) in a mixture of acetonitrile (150 ml) and tetra- hydrofuran (150 ml) is treated with silver nitrate (2. 22 g, 13. 06 mmoles) sheltered from the light. It is left under stirring for 30 minutes at room temperature, then the silver chloride is filtered and the solution is concentrated at a reduced pressure up to the half of the initial volume. Ethyl ether (100 ml) is added and, after cooling at 5°C, the obtained solid is filtered. After drying 4. 3 g of Cefalexine nitrate salt as amorphous solid are obtained. Yield 80as.

Elementary analysis for C16HlaN407s Calculated % : C 46. 83 ; H 4. 42 ; N 13. 65 ; S 7. 81 Found : C 46. 81 ; H 4. 44 ; N 13. 63 ; S 7. 80 EXAMPLE 2 Preparation of the Clindamycin nitrate salt The compound is prepared by starting from a solution of Clindamycin hydrochloride (3 g, 6. 5 mmoles) in ethanol (100 ml) by addition of silver nitrate (1. 12 g, 6. 59 mmoles) and following the procedure reported in Example 1. Clindamycin nitrate salt as amorphous solid is obtained. Yield 70%.

Elementary analysis for C18H34C1N3O8S : Calculated % : C 44. 30 ; H 7. 02 ; Cl 7. 26 ; N 8. 61 ; S 6. 57 Found % : C 44. 32 ; H 7. 03 ; Cl 7. 23 ; N 8. 62 ; S 6. 55 EXAMPLE 3 Preparation of the Amoxicillin nitrate salt The compound is prepared starting from a solution of Amoxicillin hydrochloride (2 g, 4. 98 mmoles) in a mixture of acetonitrile (80 ml)/tetrahydrofuran (80 ml) by addition of silver nitrate (0. 850 g, 5. 0 mmoles), following then the procedure reported in Example 1. Amoxicillin nitrate as amorphous solid is obtained. Yield 78%.

Elementary analysis for C16H20N4°8S Calculated % : C 44. 86 ; H 4. 71 ; N 13. 08 ; S 7. 48 Found % : C 44. 89 ; H 4. 74 ; N 13. 11 ; S 7. 45 EXAMPLE 4 Preparation of the Tetracycline nitrate salt The compound is prepared by starting from a solution of Tetracycline hydrochloride (2 g, 4. 16 mmoles) in methanol (100 ml) by adding silver nitrate (0. 71 g, 4. 17 mmoles), and following then the procedure reported in Example 1.

Tetracycline nitrate salt as amorphous solid is obtained.

Yield 60%.

Elementary analysis for C22H2, N303. 1 : Calculated % : C 52. 07 H 4. 97 N 8. 28 Found % : C 52. 05 H 4. 99 N 8. 30 EXAMPLE 5 Preparation of the Clarithromycin nitrate salt To a solution of Clarithromycin (2 g, 2. 67 mmoles) in a mixture of acetonitrile (50 ml) and chloroform (80 ml), cooled at 0°C, a 65% HNO3 solution (0. 2 ml) in acetonitrile (5 ml) is added. After the addition the mixture is let reach the room temperature and it is maintained under stirring for two hours. The solvent is evaporated at a reduced pressure.

The residue is dissolved in chloroform (50 ml) and ethyl ether (50 ml) is added. It is cooled at 5°C and the precipitate which separates is filtered. After drying 1. 83 g (2. 26 mmoles) of Clarithromycin nitrate salt as amorphous solid are obtained. Yield 80%.

Elementary analysis for C38H, BNzOls Calculated % C 56. 28 H 8. 70 N 3. 45 Found % : C 56. 25 H 8. 72 N 3. 46 EXAMPLE 6 Preparation of the Ciprofloxacin nitrate salt Triethylamine (0. 9 ml, 6. 5 mmoles) is added to a suspension of Ciprofloxacin hydrochloride (2g, 5. 4 mmoles) in 200 ml of methylene chloride. The solution is maintained under stirring for 30 minutes. The solution is washed with water (100 ml), the organic phase is dried by sodium sulphate and then evporated under vacuum obtaining the corresponding Ciprofloxacin base (1. 03 g). The substance is dissolved in a mixture of acetonitrile (60 ml)/tetra-hydrofuran (50 ml). The solution is cooled with ice and treated with a solution (0. 220 ml) of 65% nitric acid in acetonitrile (5 ml). After 30 minutes under cold stirring it is treated with ethyl ether. A solid is separated which is filtered, washed with ethyl ether and dried under vacuum. 1. 2 g of Ciprofloxacin nitrate salt as amorphous solid are obtained. Yield 45%.

Elementary analysis for Cl7Hl9N406F : Calculated % : C 51. 78 ; H 4. 86 ; N 14. 21 ; F 4. 82 Found % : C 51. 75 ; H 4. 84 ; N 14. 25 ; F 4. 80 EXAMPLE 7 Preparation of the Sulfamethoxazole nitrate salt The compound is prepared by starting from a Sulfamethoxazole solution (2 g, 7. 9 mmoli) in methanol (100 ml), addition of a 65% nitric acid solution (0. 500 ml) in acetonitrile (5 ml), following the procedure reported in Example 5. Sulfamethoxazole nitrate as amorphous solid is obtained. Yield 60as.

Elementary analysis for CloHl2N406S Calculated % : C 37. 97 ; H 3. 82 ; N 17. 71 ; S 10. 15 Found % : C 37. 99 ; H 3. 83 ; N 17. 73 ; S 10. 13 EXAMPLE 8 Preparation of the Trimethoprim nitrate salt The compound is synthetized starting from a solution of Trimethoprim (1. 5 g, 5. 17 mmoles) in chloroform (80 ml), by adding a 65% nitric acid solution (0. 360 ml) in acetonitrile (5 ml) and following then the procedure described in Example 5. Trimethoprim nitrate salt as amorphous solid is obtained.

Yield 60%.

Elementary analysis for C14HlgNsO6 : Calculated % : C 47. 59 H 5. 42 N 19. 82 Found % : C 47. 57 H 5. 44 N 19. 83 EXAMPLE 9 Preparation of the Pyrazinamide nitrate salt The compound is prepared starting from a solution of Pyrazinamide (2g, 16. 24 mmoles) in a mixture of acetonitrile (30 ml)/tetrahydrofuran (30 ml), by adding a 65% nitric acid solution (1. 2 ml) in acetonitrile (5 ml), following then the procedure described in Example 5. Pyrazinamide nitrate salt as amorphous solid is obtained. Yield 74%.

Elementary Analysis for C5H6N4O4 : Calculated % : C 32. 27 H 3. 25 N 30. 10 Found % : C 32. 29 H 3. 24 N 30. 13 EXAMPLE 10 Preparation of the Nifurfoline nitrate salt The compound is prepared starting from a Nifurfoline solution (1 g, 2. 96 mmoles) in a mixture of tetrahydrofuran (20 ml)/acetonitrile (20 ml), by adding a 65% nitric acid solution (0. 210 ml) in acetonitrile (3 ml), and following then the procedure described in Example 5. Nifurfoline nitrate salt as amorphous solid is obtained. Yield 55%.

Elementary analysis for C13Hl6N609 : Calculated % : C 39. 01 H 4. 03 N 20. 99 Found % : C 39. 03 H 4. 05 N 21. 01 EXAMPLE 11 Preparation of Acyclovir nitrate salt The compound is prepared starting from an Acyclovir solution (1 g, 4. 44 mmoles) in a mixture of tetrahydrofuran (20 ml)/acetonitrile (20 ml), by adding a 65% nitric acid solution (0. 310 ml) in acetonitrile (5 ml), and following then the procedure described in Example 5. Acyclovir nitrate salt as amorphous solid is obtained. Yield 60%.

Elementary analysis for C, H,, N606 : Calculated % : C 33. 34 H 4. 20 N 29. 17 Found % : C 33. 31 H 4. 22 N 29. 19 EXAMPLE 12 Preparation of Metronidazole nitrate salt The compound is prepared starting from a metronidazole solution (1 g, 5. 84 mmoles) in a mixture of tetrahydrofuran (10 ml)/acetonitrile (15 ml) and by adding a 65% nitric acid solution (0. 410 ml) in acetonitrile (3 ml), following then the procedure described in Example 5. Metronidazole nitrate salt as amorphous solid is obtained. Yield 70%.

Elementary analysis for C6HloN406 Calculated % : C 30. 77 H 4. 30 N 24. 03 Found % : C 30. 74 H 4. 28 N 24. 01 EXAMPLE 13 Preparation of Erythromycin nitrate salt The compound is prepared starting from an erythromycin solution (2 g, 2. 72 mmoles) dissolved in a mixture of chloroform (30 ml)/acetonitrile (20 ml), by adding a 65% nitric acid solution (0. 200 ml) in acetonitrile (5 ml), following then the procedure described in Example 5.

Erythromycin nitrate as amorphous solid is obtained. Yield 83%.

Elementary analysis : Calculated % C 55. 76 H 8. 59 N 3. 51 Found % : C 55. 79 H 8. 60 N 3. 53 EXAMPLE 14 Preparation of the Cefazolin nitrate salt The compound is prepared by adding to a Cefazolin solution (1. 5 g, 3. 3 mmoles) in methanol (50 ml) a 65% nitric acid solution (0. 250 ml) in acetonitrile (5 ml) and following then the procedure reported in Example 5. Cefazolin nitrate as amorphous solid is obtained. Yield 60%.

Elementary Analysis for Cl4Hl5NgO7S3 : Calculated : C 32. 49 ; H 2. 92 ; N 24. 36 ; S 18. 59 Found : C 32. 48 ; H 2. 94 ; N 24. 37 ; S 18. 57 EXAMPLE 15 Preparation of the Ampicillin nitrate salt The compound is prepared startaing from an Ampicillin solution (2 g, 5. 72 mmoles) in a mixture formed by acetonitrile (30 ml) and tetrahydrofuran (20ml), by adding a 65% nitric acid solution (0. 450 ml) in acetonitrile (5 ml) and following the procedure reported in Example 5. Ampicillin nitrate as amorphous solid is obtained. Yield 55%.

Elementary analysis for Cl6H2oN407s : Calculated : C 46. 60 ; H 4. 89 ; N 13. 58 ; S 7. 77 Found : C 46. 56 ; H 5. 91 ; N 13. 59 ; S 7. 76 PHARMACOLOGICAL EXAMPLES Dilution test in vitro on medium for antibacterial agents The capability to antagonize the arising of the microbial resistance of the nitrate salts of the antimicrobial compounds in comparison with that of the respective precursors has been evaluated.

Such activity has been determined by using the dilution method in vitro on culture medium as described by Sahm et al.

(S. D. Sahm, J. A. Washington"Antibacterial susceptibility tests : dilution methods"in : Manual Manual Clinical Microbiology, ed. A. Balows, W. J. Hausler, Jr, K. L. Hermann, H. D. Isenberg, H. J. Shadomy, 1991, American Society for Microbiology).

According to this method a concentration in aqueous solution of substance having antimicrobial activity able to inhibit the growth of some bacterial strains is determined. For the precursor the maximum concentration of the substance at which the microbial growth is still observed under the adopted experimental conditions is selected and the same concentration is used for the corresponding nitrate salt. The solvents and the necessary dilutions for preparing the strain substances of the antibiotics to be tested are prepared according to procedures standard and well known to the man skilled in the field (National Committee for Clinical Laboratory Standards, 1990"Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically. Approved standard M7-A2. National Committee for Clinical Laboratory Standards, Villanova, Pa). Also the preparation of the culture medium is carried out according to standard procedures and the CAMH broth is used (Cation- adjusted Mueller-Hinton broth) (National Committee for Clinical Laboratory Standards, 1990"Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically. Approved standard M7-A2. National Committee for Clinical Laboratory Standards, Villanova, Pa).

The inoculation procedure is carried out according to standard procedures and the final concentration of the inocolum is of 5 x 105 CFU (colony forming unit)/ml. The used microorganisms have been Escherichia Coli (ATCC25922) and Staphylococcus Aureus (ATCC29213).

The test tubes are incubated at 35°C for 20 hr before reading. The microbial growth, or the absence of the same, is determined in a qualitative way, with the naked eye and it indicates the microbial resistance or, respectively, the sensitivity to the antimicrobial agent. The results of the tests are reported in Tables 1 and 2, which show that the nitrate salt has an antimicrobial activity higher than that of the precursor.

EXAMPLE 16 Synthesis of 1-Ethyl-6, 8-difluoro-1, 4-dihydro-7- (3-methyl-1- piperazinyl)-4-oxo-3-quinolincarboxylic acid 4-nitrooxybutyl ester nitrate salt A) Synthesis of 1-Ethyl-6, 8-difluoro-1, 4-dihydro-7- (3-methyl- N-tert-butoxycarbonyl-1-piperazinyl)-4-oxo-3- quinolincarboxylic acid 4-bromobutyl ester To a stirred solution of 1-Ethyl-6, 8-difluoro-1, 4- <BR> <BR> dihydro-7- (3-methyl-1-piperazinyl)-4-oxo-3-quinolincarboxylic acid hydro chloride (504. 14 mg, 1. 3 mmoles) in 1, 4-dioxane (2. 6 ml) and NaOH 2M (1, 3 ml), was added di-tert-butyl dicarbonate (306 mg, 1. 4 mmoles) at 0 °C. After stirring for 2 hours the suspension was filtered and the precipitate washed with 1, 4-dioxane, dried to afford 1-Ethyl-6, 8-difluoro-1, 4- dihydro-7- (3-methyl-N-tert-butoxycarbonyl-1-piperazinyl)-4- oxo-3-quinolincarboxylic acid that was used without further purification.

To a suspension of 1-Ethyl-6, 8-difluoro-1, 4-dihydro-7- (3- methyl-N-tert-butoxycarbonyl-1-piperazinyl)-4-oxo-3-quinolin carboxylic acid and NaHCO3 (11 mg, 1. 3 mmoles) in DMF (10 ml) was added 1, 4-dibromobutane (1. 4 g, 6. 5 mmoles).

The mixture was refluxed for 1 hour and, after cooling, were added in the order water and ethyl acetate. After separation of the phases the organic layer was washed with water, dried with sodium sulphate and evaporated under reduced pressure. The residue was purified by chromatography on silica gel eluting with ethyl acetate/n-hexane (v/v 2/1) to afford 1-Ethyl-6, 8-difluoro-1, 4-dihydro-7- (3-methyl-N-tert- butoxy carbonyl-1-piperazinyl)-4-oxo-3-quinolineecarboxylic acid 4-bromobutyl ester (380 mg, 0. 65 mmoles) as an amorphous solid. Yield 50%.

B) Synthesis of l-Ethyl-6, 8-difluoro-1, 4-dihydro-7- (3-methyl- l-piperazinyl)-4-oxo-3-quinolincarboxylic acid 4-nitrooxybutyl ester To a solution of l-Ethyl-6, 8-difluoro-1, 4-dihydro-7- (3- methyl-N-tert-butoxycarbonyl-l-piperazinyl)-4-oxo-3-quinolin carboxylic acid 4-nitrooxybutyl ester (300 mg, 0. 51 mmoles) in anhydrous acetonitrile (5 ml) was added silver nitrate (170 mg, 1 mmoles). The mixture was refluxed for 4 hours in the darkness.

The suspension was filtered and the filtrate washed with water (3X8 ml) and dried with sodium sulphate, then evaporated in vacuo.

The compound was deprotected by treating with trifluoroacetic acid (1 ml) at room temperature, in an inert atmosphere (N2), for 1 hour. Trifluoroacetic acid was removed by evaporation under a reduced pressure and the residue was purified by chromatography on a weakly basic ion-exchange resin (Amberlysto A-21) eluting with ethyl acetate to afford l-ethyl-6, 8-difluoro-1, 4-dihydro-7- (3-methyl-1-piperazinyl)-4- oxo-3-quinolin carboxylic acid 4-nitrooxybutyl ester (150 mg, 0. 32 mmoles) as an amorphous solid.

1H NMR (ppm) : 8. 25 (1H, s) ; 7. 85 (1H, d) ; 4. 52 (2H, t) ; 4. 5- 4. 2 (4H, m) ; 3. 4-2. 8 (7H, m) ; 1. 94-1. 83 (4H, m) ; 1. 48 (3H, m) ; 1. 06 (3H, d).

C) Synthesis of l-Ethyl-6, 8-difluoro-1, 4-dihydro-7- (3-methyl- l-piperazinyl)-4-oxo-3-quinolincarboxylic acid 4-nitrooxybutyl ester nitrate salt To a solution of l-ethyl-6, 8-difluoro-1, 4-dihydro-7- (3- methyl-l-piperazinyl)-4-oxo-3-quinolincarboxylic acid 4- nitrooxy butyl ester (150 mg, 0. 32 mmoles) in CH2Cl2 (2 ml) was added HCl-AcOEt 1 M (0. 5 ml). After stirring for 1 hours at room temperature, the solvent was evaporated under reduced pressure and the residue dissolved in THF (4 ml) and silver nitrate (55 mg, 3. 03 mmoles) was added. The mixture was stirred for 1 hour at room temperature, the suspension was filtered and the precipitate washed with THF, dried to afford l-Ethyl-6, 8-difluoro-1, 4-dihydro-7- (3-methyl-1-piperazinyl)-4- oxo-3-quinolin carboxylic acid 4-nitrooxybutyl ester nitrate salt (150 mg) as an amorphous solid. Yield 88%.

Elementary Analysis : WC WH kN WF calculated : 47. 46 5. 12 13. 18 7. 15 found : 47. 50 5. 10 13. 10 7. 20 EXAMPLE 17 Synthesis of 1-Ethyl-6-fluoro-1, 4-dihydro-4-oxo -7-(1-pipera zinyl)-3-quinolinecarboxylic acid 4-nitrooxybutyl ester nitrate salt A) Synthesis of 1-Ethyl-6-fluoro-1, 4-dihydro-4-oxo-7- (N-tert- butoxy carbonyl-1-piperazinyl-)-3-quinolinecarboxylic acid 4- bromobutyl ester To a solution of 1-Ethyl-6-fluoro-1, 4-dihydro-7-(3- methyl-1-piperazinyl)-4-oxo-3-quinolincarboxylic acid hydro chloride (2. 5 g, 7. 8 mmoles) and KOH 2M (11. 7 ml) in 1, 4- dioxane (15 ml) was added di-tert-butyl dicarbonate (1, 75 g, 8 mmoles), at-4 °C. The mixture was stirred for 1 hour at 0 °C , thereafter the cooling bath was removed and stirred until the temperature was risen to room temperature (about 1 hour).

Water (15 ml) was added and, after cooling, the mixture was filtered and the precipitate was dried to afford 1-Ethyl-6- fluor-1, 4-dihydro-4-oxo-7- (N-tert-butoxycarbonyl-l- piperazinyl-)-3-quinoline carboxylic acid, that was used without further purification.

To a suspension of 1-Ethyl-6-fluoro-1, 4-dihydro-4-oxo-7- (N-tert-butoxycarbonyl-1-piperazinyl-)-3-quinolinecarboxylic acid and 18-crown-6 (1, 4, 7, 10, 13-pentaoxacyclopentadecane) in anhydrous THF (20 ml) was added 1, 4-dibromobutane (1. 4 g, 6. 5 mmoles) in an inert atmosphere (N2).

The mixture was refluxed for 1 hour and, after cooling, water and ethyl acetate were added in the order.

After separation of the phases, the organic layer was washed with water, dried with sodium sulphate and evaporated under reduced pressure.

The residue was purified by chromatography on silica gel eluting with ethyl acetate/n-hexane (v/v 2/1) to afford 1- <BR> <BR> <BR> Ethyl-6-fluoro-1, 4-dihydro-7- (3-methyl-N-tert-butoxycarbonyl- 1-pipera zinyl)-4-oxo-3-quinolinecarboxylic acid 4-bromobutyl ester (380 mg, 0. 65 mmoles) as an amorphous solid. Yield 66%.

B) Synthesis of 1-Ethyl-6-fluoro-1, 4-dihydro-4-oxo-7- (1- pipera zinyl)-3-quinolinecarboxylic acid 4-nitrooxybutyl ester nitrate salt To a solution of 1-Ethyl-6-fluoro-1, 4-dihydro-4-oxo-7- (N- tert-butoxycarbonyl-1-piperazinyl-)-3-quinolincarboxylic acid 4-nitrooxybutyl ester (443. 5 mg, 0. 8 mmoles) in anhydrous acetonitrile (7 ml) was added silver nitrate (406 mg, 0. 8 mmoles). The mixture was refluxed for 5 hours in the darkness, in an inert atmosphere (N2). The suspension was filtered, the filtrate was evaporate in vacuo. The residue was dissolved in CH2Cl2 (10 ml) and the mixture was washed with water (5X10 ml) and anhydrified with sodium sulphate, the solvent was then evaporated under reduced pressure.

The compound was deprotected with trifluoroacetic acid (1. 6 ml) at room temperature, in an inert atmosphere (N2) for 1 hour. Trifluoroacetic acid was evaporated under reduced pressure and the residue was purified by chromatography on a weakly basic ion-exchange resin (Amberlysto A-21) eluting with methanol to afford 1-Ethyl-6-fluoro-1, 4-dihydro-4-oxo-7- (1- piperazinyl)-3-quinolinecarboxylic acid 4-nitrooxybutyl ester nitrate (306 mg, 0. 7 mmoles) as a yellow amorphous solid.

'H NMR (DMSO) ppm : 7. 39 (5H, d) ; 7. 03 (8H, d) ; 5. 96 (2H, s) ; 4. 58 (2H, m) ; 4. 38 (2H, m) ; 4. 18 (2H, m) ; 3. 33 (4H, m) ; 3. 16 (4H, m) ; 1. 94-1. 83 (4H, m) ; 1. 8-1. 86 (4H, m) ; 1. 35 (3H, t).

C) Synthesis of 1-Ethyl-6-fluoro-1, 4-dihydro-4-oxo-7- (1- pipera zinyl)-3-quinolinecarboxylic acid 4-nitrooxybutyl ester nitrate salt To a solution of 1-Ethyl-6-fluoro-1, 4-dihydro-4-oxo-7- (1-piperazinyl)-3-quinolinecarboxylic acid 4-nitrooxybutyl ester (300 mg, 0. 68 mmoles) in CH, CL, (5 ml) was added HC1- AcOEt 1 M (0. 8 ml). After stirring for 1 hour at room temperature, the solvent was evaporated under a reduced pressure. The residue was dissolved in THF (10 ml) and silver nitrate (120 mg, 0. 70 mmoles) was added. The mixture was stirred for 1 hour at room temperature, the suspension was filtered and the precipitate washed with THF and dried to afford 1-Ethyl-6-fluoro-1, 4-di hydro-4-oxo-7-(1-piperazinyl)- 3-quinolinecarboxylic acid 4-nitrooxybutyl ester nitrate salt (300 mg) as an amorphous solid. Yield 85%.

Elementary Analysis : %C %H %N %F calculated : 48. 10 5. 25 14. 02 3. 80 found : 48. 05 5. 30 14. 11 3. 75 EXAMPLE 18 Synthesis of 3- [ [4- [l-Cyclopropyl-6-fluoro-1, 4-dihydro-4-oxo- <BR> <BR> 7- (1-piperazinyl)-3-quinolinecarbonyloxy]-3-methoxy] phenyl]-2- propenoic acid 4- (nitrooxybutyl) butyl ester nitrate salt.

A) Synthesis of 1-Cyclopropyl-6-fluoro-1, 4-dihydro-4-oxo-7- (N- tert-butoxycarbonyl-l-piperazinyl-)-3-quinolinecarboxylic acid To a suspension of 1-cyclopropyl-6-fluoro-1, 4-dihydro-4- oxo-7- (l-piperazinyl-)-3-quinolinecarboxylic acid (3. 31 g, 10 mmoles) in CH2Cl2 (120 ml) were added at room temperature TEA (4. 21 ml, 30 mmoles) and di-tert-butyl dicarbonate (4. 4 g, 30 mmoles). The mixture was stirred for 12 hours at room temperature. After cooling at-5°C the suspension was filtered, the collected precipitate dissolved in CH2C12 (200 ml) and the resulting solution washed with aq AcOH 0. 3 M (100 ml).

The organic phase was dried with sodium sulphate and the solvent was evaporated in vacuo. The residue was crystallized from a mixture CH2C12 (10 ml)/n-hexane (100 ml) to afford 1- Cyclopropyl-6-fluoro-1, 4-dihydro-4-oxo-7- (N-tert-butoxy carbonyl-1-piperazinyl-)-3-quinolinecarboxylic acid (3. 93 g).

Yield 91%. m. p. 248-249°C (dec.) B) Synthesis of 3-[[4-[1-Cyclopropyl-6-fluoro-1, 4-dihydro-4- oxo-7-(N-tert-butoxycarbonyl-1-piperazinyl)-3- quinolinecarbonyloxy]-3-methoxy] phenyl]-2-propenoic acid 4- (nitrooxybutyl) butyl ester To a solution of 1-cyclopropyl-6-fluoro-1, 4-dihydro-4- oxo-7-(N-tert-butoxycarbonyl-1-piperazinyl-)-3- quinolinecarboxylic acid (5. 36 g, 12. 43 mmoles) and of 3- [ (3- methoxy-4-hydroxy) phenyl]-2-propenoic acid 4-nitrooxybutyl ester (3. 78 g, 12. 43 mmoles) in CH2Cl2 (100 ml) Ph3P (4. 89 g, 18. 64 mmoli) and DEAP (2. 94 ml, 18. 64 mmoli) were added in the order. The mixture was stirred for 2 hours at room temperature, then the solvent was evaporated under reduced pressure. The residue was purified by chromatography on silica gel eluting with CH2Cl2/acetone (v/v 30/1) to afford 3- [4- [1- Cyclopropyl-6-fluoro-1, 4-dihydro-4-oxo-7- (N-tert- butoxycarbonyl-1-piperazinyl)-3-quinolinecarbonyloxy]-3- methoxy] 2-propenoic acid 4- (nitrooxybutyl) butyl ester (3. 5 g).

Yield 40%.

C) Synthesis of 3- [4- [l-Cyclopropyl-6-fluoro-1, 4-dihydro-4- oxo-7- (l-piperazinyl)-3-quinolinecarbonyloxy]-3-methoxy] 2- propenoic acid 4- (nitrooxybutyl) butyl ester hydrochloride To a solution of 3- [4- [l-Cyclopropyl-6-fluoro-1, 4- dihydro-4-oxo-7-(N-tert-butoxycarbonyl-l-piperazinyl)-3- quinoline carbonyloxy]-3-methoxy] 2-propenoic acid 4- (nitrooxybutyl) butyl ester (3. 5 g) in CH2C12 (50 ml) was added HCl-AcOEt 20% (5 ml). After stirring for 2 hours at room temperature, the solvent was evaporated under a reduced pressure and the residue was dissolved in acetone (40 ml).

After cooling at 0°C for 30 minutes, the suspension was filtered and the collected precipitate washed with diethyl ether to afford 3- [4- [l-Cyclopropyl-6-fluoro-1, 4-dihydro-4- oxo-7- (1-piperazinyl)-3-quino linecarbonyloxy]-3-methoxy] 2- propenoic acid 4- (nitrooxy butyl) butyl ester hydrochloride (2 g) as a yellow solid, m. p. 207-209°C.

H NMR (DMSO) ppm : 9. 26 (1H, s), 8. 68 (1H, s), 7. 85 (1H, d), 7. 68 (1H, d), 7. 53 (2H, dd), 7. 35 (1H, dd), 7. 20 (1H, d), 6. 74 (lH, d), 4. 6 (2H, t), 4. 2 (2H, t), 3. 83 (3H, s), 3. 76 (1H, m), 5. 52 (4H, m), 3. 33 (4H, s), 1. 78 (4H, m), 1-32-1. 16 (4H, m).

D) Synthesis of 3-[[4-[1-Cyclopropyl-6-fluoro-1, 4-dihydro-4- oxo-7- (l-piperazinyl)-3-quinolinecarbonyloxy]-3- methoxy] phenyl]-2-propenoic acid 4- (nitrooxybutyl) butyl ester nitrate salt.

To a solution of 3-[[4-[1-Cyclopropyl-6-fluoro-1, 4- dihydro-4-oxo-7- (1-piperazinyl)-3-quinolinecarbonyloxy]-3- methoxy] phenyl]-2-propenoic acid 4- (nitrooxybutyl) butyl ester hydro chloride (2 g, 3. 03 mmoles) in THF (20 ml) was added silver nitrate (514 mg, 3. 03 mmoles). After stirring for 1 hours at room temperature, the mixture was filtered and the precipitate washed with THF and dried to afford 3- [4- [l- Cyclopropyl-6-fluoro-1, 4-dihydro-4-oxo-7- (1-piperazinyl)-3- quinolinecarbonyl oxy]-3-methoxy] 2-propenoic acid 4- (nitrooxybutyl) butyl ester nitrate salt (2g) as an amorphous solid. Yield 96%.

Elementary Analysis : %C@ %H %N %F Calculated : 54. 78 5. 17 9. 98 2. 71 Found : 54. 69 5. 15 9. 99 2. 69 EXAMPLE 19 Synthesis of 4- (nitrooxy) butanoic acid 2-methyl-5-nitro imidazole-1-ethyl ester nitrate salt A) Synthesis of 4-bromobutanoic acid 2-methyl-5-nitro imidazole-l-ethyl ester.

To a solution of metronidazole (7. 5 g, 43. 82 mmoles) in CHCl3 (75 ml) and DMF (93 ml) 4-bromobutyrric acid (6. 1 g, 36. 51 mmoli) was added. After stirring the mixture for 24 hours at room temperature, the organic phase was washed with water, dried with sodium sulphate and evaporated under a reduced pressure.

The residue was purified by chromatography on a silica gel column eluted with metilene chlorid/acetone (v/v 9/1) to afford 4-Bromobutanoic acid 2-methyl-5-nitroimidazole-1-ethyl ester (6. 5 g, 20. 3 mmoles). Yield 55%.

B) Synthesis of 4- (nitrooxy) butanoic acid 2-methyl-5-nitro imidazole-1-ethyl ester To a solution of 4-bromobutanoic acid 2-methyl-5-nitro imidazole-1-ethyl ester (6. 4 g, 20. 05 mmoles) in anhydrous acetonitrile (170 ml) silver nitrate (5. 11 g, 30. 07 mmoles) was added. The mixture was heated at 40°C for 48 hours in the darkness. The mixture was filtered and the filtrate was washed with water, dried with sodium sulphate and evaporated in vacuo.

The residue was purified by chromatography on a silica gel column by eluting with metilene chloride/acetone (v/v 9/1) to afford 4- (nitrooxy) butanoic acid 2-methyl-5-nitroimidazole- 1-ethyl ester (3. 68 g, 12. 17 mmoli) as an oil. Yield 60%.

'H NMR (DMSO) ppm : 8. 08 (1H, s) ; 4. 55 (2H, t) ; 4. 53 (2H, t) ; 4. 43 (2H, t) ; 2. 51 (2H, s) ; 2. 40 (2H, t) ; 1. 91 (2H, tt).

C) Synthesis of 4- (nitrooxy) butanoic acid 2-methyl-5-nitro imidazole-1-ethyl ester nitrate salt To a solution of 4- (nitrooxy) butanoic acid 2-methyl-5- nitroimidazole-1-ethyl ester (3. 68 g, 12. 17 mmoles) in CH2C12 (80 ml) was added HCl-AcOEt 1M (12. 2 ml). After stirring for 1 hour at room temperature, the solvent was evaporated under a reduced pressure and the residue was dissolved in THF (75 ml).

Silver nitrate (2 g, 12. 17 mmoles) was added. The mixture was stirred for 1 hour at room temperature, the suspension filtered and the precipitate washed with THF and dried to afford 4- (nitrooxy) butanoic acid 2-methyl-5-nitroimidazole-1- ethyl ester nitrate salt (4. 2 g) solid. Yield 90%.

Elementary Analisys : %C %H %N Calculated : 31. 50 3. 96 18. 37 Found : 31. 45 3. 90 18. 29 EXAMPLE 20 Synthesis of 4- (nitrooxy) butanoic acid 5-nitro-8-quinolinol es. ter nitrate salt A) Synthesis of 4-bromobutanoic acid 5-nitro-8-quinolinol ester To a solution of nitroxoline (4. 32 g, 22. 72 mmoles) and triethylamine (2. 75g, 27. 26 mmol) in CHCl3 (100 ml) and DMF (69 ml) 4-bromobutyrrilchloride (5. 05 g, 27. 26 mmoles) was added at 0°C. After stirring at room temperature for 24 hours, another portions of triethylamine (0. 46 g, 4. 5 mmol) and 4- bromobutyrril chloride (0. 83 g, 4. 5 mmoles) were added. The mixture was stirred for 48 hours at room temperature. Water and metilene chloride were added and, after separation of the two phases, the organic layer was washed with water, dried with sodium sulphate and evaporated under a reduced pressure.

The residue was purified by chromatography on silica gel column eluted with ethyl acetate/n-hexane (v/v 2/8) to afford 4-bromobutanoic acid 5-nitro-8-quinolinol ester (6. 86 g, 20. 22 mmoles) as an oil. Yield 90%.

H NMR (CDCl3) ppm : 9. 06 (2H, m) ; 8. 44 (1H, d) ; 7. 65 (1H, m) ; 7. 5 (1H, d) ; 3. 66 (2H, m) ; 3. 03 (2H, m) ; 2. 42 (2H, m).

B) Synthesis of 4- (nitrooxy) butanoic acid 5-nitro-8-quinolinol ester To a solution of 4-bromobutanoic acid 5-nitro-8- quinolinol ester (6. 86 g, 20. 2 mmoles) in anhydrous acetonitrile (100 ml) silver nitrate (13. 65 g, 80. 3 mmoles) was added. The mixture was heated at 40°C for 64 hours in the darkness. The mixture was then filtered, the filtrate dried with sodium sulphate and evaporated under reduced pressure.

The residue was purified by chromatography on a silica gel column eluted with ethyl acetate/. n-hexane (v/v 3/7) to afford 4- (nitrooxy) butanoic acid 5-nitro-8-quinolinol ester (2. 05 g, 6. 38 mmoles) as an yellow amorphous solid. Yield 31%. (m. p. = 68°C).

'H NMR (DMSO) ppm : 9. 02 (1H, dd) ; 8. 97 (1H, d) ; 8. 45 (1H, dd) ; 7. 65 (1H, m) ; 7. 54 (1H, dd) ; 4. 74 (2H, t) ; 2. 97 (2H, t) ; 2. 03 (2H, m).

C) Synthesis of 4- (nitrooxy) butanoic acid 5-nitro-8-quinolinol ester nitrate salt To a solution of 4- (nitrooxy) butanoic acid 5-nitro-8- quinolinol ester (2. 05 g, 6. 38 mmoles) in ethyl acetate (40 ml) was added HCl-AcOEt 1M (6. 4 ml). After stirring for 1 hour at room temperature, the solvent was evaporated under a reduced pressure and the residue was dissolved in THF (50 ml) and added of silver nitrate (1. 08 g, 6. 38 mmoles). The mixture was stirred for 1 hour at room temperature, the suspension was filtered and the precipitate was washed with THF, dried to afford 4- (nitro oxy) butanoic acid 2-methyl-5-nitroimidazole-l- ethyl ester nitrate salt (2. 2 g) solid. Yield 89%.

Elementary Analisys : % C % H % N Calculated : 39. 01 3. 22 13. 99 Found : 38. 94 3. 14 13. 91 EXAMPLE 21 Synthesis of 6- (D- (-)-alfa-aminophenylacetamido) pennicillanic acid 4- (nitrooxy) butyl ester nitrate salt A) Synthesis of 6- (D- (-)-alfa-aminophenylacetamido) pennicillanic sodium salt To a solution of ampicillin (5. 09 g, 14. 6 mmoles) in absolute ethanol (120 ml) sodium ethylate (0. 99 g, 14. 6 mmoles) was added. The mixture was stirred for 1 hour at room temperature and then for at 60°C 30 minutes. The mixture was evaporated under a reduced pressure to afford 6- (D- (-)-alfa- aminophenylacetamido) pennicillanic sodium salt (5. 4 g, 14. 5 mmoles) as a white solid. Yield 99%.

B) Synthesis of 6- (D- (-)-alfa-tert-butoxycarbonylaminophenyl acetamido) pennicillanic acid To a solution of 6- (D- (-)-alfa-aminophenylacetamido) pennicillanic sodium salt (5. 4 g, 14. 57 mmoles) in 1, 4-dioxan (166 ml) and water (121 ml), at a temperature of 0°C a solution of di-tert-butyl dicarbonate (5. 08 g, 23. 31 mmoles) in 1, 4-dioxane (45 ml) was added. When the addition was ended, the temperature was raised at room temperature and stirring was continued for 48 hours. The mixture was then evaporated under a reduced pressure. The residue was dissolved in aqueous NaHCO3 5%, washed with diethyl ether ; the pH value of the aqueous phase was adjusted to the value of 2 by adding at a temperature of 0°C H3PO4 50% (11 ml). After extraction of the aqueous phase with ethyl acetate, the combined organic phases were dried and evaporated under a reduced pressure to afford 6- (D- (-)-a-tert-butoxycarbonylaminophenylacetamido) pennicillanic acid, that was used without further purification.

1H NMR (CDC13) ppm : 7. 34 (5H, s) ; 6. 85 (1H, bs) ; 5. 8 (1H, bs) ; 5. 6 (lH, dd) ; 5. 45 (1H, d) ; 5. 22 (1H, bs) ; 4. 38 (1H, s) ; 1. 4 (15H, m).

B) Synthesis of 6- (D- (-)-alfa-aminophenylacetamido) pennicillanic acid 4-bromobutyl ester To a solution of 6- (D- (-)-alfa-tert-butoxycarbonyl aminophenylacetamido) pennicillanic acid (6. 36 g, 14. 15 mmoles) in DMF (60 ml) triethylamine (2. 76 ml, 19. 81 mmoles) was added. After stirring for 30 minutes, 1, 4-dibromobutane (6. 11 g, 28. 30 mmoles) was added and the mixture stirred for 12 hours.

Diethyl ether was then added at the suspension and Et3N. HBr was filtered off. The organic phase was washed with water, dried with sodium sulphate and evaporated under a reduced pressure.

The residue was purified by chromatography on silica gel column eluted with ethyl acetate/n-hexane (v/v 15/85) to afford 6- (D- (-)-alfa-aminophenylacetamido) pennicillanic acid 4-bromo butyl ester (3. 2 g) as a white solid.

1H NMR (CDC13) ppm : 7. 35 (5H, m) ; 6. 6 (1H, bs) ; 5. 6 (1H, m) ; 5. 4 (1H, d) ; 5. 2 (1H, bs) ; 4. 39 (1H, s), 4. 18 (2H, m) ; 3. 42 (2H, t) ; 1. 9 (4H, m) ; 1. 4 (15H, m).

C) 6- (D- (-)-alfa-aminophenylacetamido) pennicillanic acid 4- nitrooxy butyl ester To a solution of 6- (D- (-)-alfa-aminophenylacetamido) pennicillanic acid 4-bromobutyl ester (3. 12 g, 5. 34 mmoles) in acetonitrile (50 ml) silver nitrate (1. 27 g, 7. 48 mmoles) was added. The mixture was heated at 40°C for 10 hours in the darkness. Then mixture was filtered and evaporated under a reduced pressure. The residue was purified by chromatography on a silica gel column by eluting with ethyl acetate/n-hexane (v/v 3/7) to afford 6- (D- (-)-alfa-aminophenylacetamido) pennicillanic acid 4-nitrooxybutyl ester (0. 9 g) as a yellow amorphous solid.

1H NMR (CDC13) ppm : 7. 35 (5H, m) ; 6. 6 (1H, bs) ; 5. 6 (1H, m) ; 5. 4 (1H, m) ; 5. 2 (1H, bs) ; 4. 5 (2H, m) ; 4. 4 (1H, s) ; 4. 2 (2H, m) ; 1. 8 (4H, bs) ; 1. 4 (15H, m).

D) 6- (D- (-)-alfa-aminophenylacetamido) pennicillanic acid 4- nitro oxy butyl ester nitrate salt To a solution of 6- (D- (-)-alfa-aminophenylacetamido) pennicillanic acid 4-nitrooxybutyl ester (0. 9 g, 1. 58 mmoles) in ethyl acetate (10 ml) a solution HC1 1M in AcOEt (1. 5 ml) was added at 0 °C. The mixture was stirred at 0°C for 20 minutes and for 1 hour at room temperature. The solvent was evaporated under a reduced pressure, the residue dissolved in THF (5 ml) and the solution added of silver nitrate (268 mg, 1. 58 mmoles). The mixture was stirred for 1 hour at room temperature, then filtered, and the precipitate washed with THF and dried to afford 6- (D- (-)-alfa- aminophenylacetamido) pennicillanic acid 4-nitrooxybutyl ester nitrate salt (736 mg) solid. Yield 88%.

Elementary Analisys : WC % H WN WS Calculated : 45. 36 5. 14 13. 22 6. 05 Found : 45. 28 5. 08 13. 16 5. 97 Table 1 Strain E. Coli (ATCC25922) : Antimicrobial activity of Cefazolin and Cefazolin nitrate salt, Ampicillin and Ampicillin nitrate salt. COMPOUND CONCENTRATION RESPONSE (Fig/ml) Cefazolin 0.5 Growth # Cefazolin.HNO3 0.5 No growth Ampicillin 1. 0 Growth Ampicillin. HNO3 1. 0 No growth Table 2 Strain S. Aureus (ATCC29213) : Antimicrobial activity of Clindamycin and Clindamycin nitrate salt, Ciprofloxacin and Ciprofloxacin nitrate salt, Sulfamethoxazole and Sulfamethoxazole nitrate salt, Trimethoprim and Trimethoprim nitrate salt, Erythromycin and Erythromycin nitrate salt. COMPOUND CONCENTRATION RESPONSE (µg/ml) Clindamycin 0. 03 Growth Clindamycin. HNO3 0. 0 3 No growth Ciprofloxacin 0.05 Growth Ciprofloxacin.HNO3 1.0 No growth Sulfamethoxazole 20 Growth Sulfamethoxazole. HNO3 20 No growth Trimethoprim 0. 5 Growth Trimethoprim. HNO3lS 0. 5 No growth Erythromycin 0. 06 Growth Erythromycin. HNO3 0. 06 No growth