Penem derivatives

Abstract: There are provided compounds of formula I : wherein R¹ is hydrogen or a C₁-C₄ alkyl group either unsubstituted or substituted by one or more substituents chosen from a free or protected hydroxy or halogen atom; R² is a free or esterified carboxy group or carboxylate anion; R³ and R⁴ are each independently hydrogen or organic group, X is -O-, -O- -, -O--NH-, -O-O-, - , , -S-, Q is either (a″) free or protected hydroxy, or (b″) a C₁-C₄ acyloxy, or (c″) carbamoyloxy OCONH₂, or (d″) an optionally substituted heterocyclylthio group, or (e″) an optionally substituted imido group, or (f″) an optionally substituted quaternary ammonium group or (g″) a halogen atom, and the pharmaceutically or veterinarily acceptable salts thereof. There are provided also methods for preparing compounds of formula I. The compounds of formula I are useful as antibacterial agents.

Description: The present invention relates to new penem compounds, to processes for their preparation, and to pharmaceutical and veterinary compositions containing them. Compounds of the invention are penem derivatives of the following formula (I) : wherein R¹ is hydrogen or a C₁-C₄ alkyl group either unsubstituted or substituted by one or more substituents chosen from a free or protected hydroxy or halogen atom; R² is a free or esterified carboxy group or carboxylate anion wherein the ester group is of any known type which can be hydrolized "in vivo" R³ and R⁴ are each independently either hydrogen or hydroxy group; X is either (a') an oxygen atom, or (b') an oxycarbonyl group or (c') an oxycarbonylamino group or (d') an oxycarbonyloxy (carbonate) group or (e') a sulphinyl group or (f') a sulphonyl group (g') a sulphur atom ; Q is an optionally substituted quaternary ammonium group selected from the following. wherein the pyridinium, pyrrolidinium, piperidinium, morpholinium, quinuclidinium, quinolinium, isoquinolinium, pyrazinium, thieno|2,3-c|pyridinium, furo|2,3-c|pyridinium, furo|3,2-c|pyridinium, thieno|3,2-c|pyridinium, thieno|2,3-b|pyridinium, pyrazolinium, triazolinium, furo|2,3-b|pyridinium, thieno|3,4-c|pyridinium, and thiazolo|4,5-c|pyridinium rings are either unsubstituted or substituted by one or two substituents selected from C₁-C₄ alkoxy, cyano-C₁-C₄ alkyl, C₁-C₄ alkyl, hydroxy , sulpho-C₁-C₄ alkyl, hydroxy-C₁-C₄-alkyl, formylamino, formyl, hydroxyimino-C₁-C₄ alkyl, amino and carboxy-C₁-C₄ alkyl groups, and the pharmaceutically or veterinarily acceptable salts thereof. The present invention includes all the possible geometrical and optical isomers of the compounds of formula (I) either in the form of isomeric mixtures or in the form of the individual separated isomers. Preferably, the compounds of formula (I) have a (5R,6S) configuration. The preferred R¹ group is an (α-hydroxy)ethyl radical and has a (1R) configuration, i.e. a R configuration at the α -carbon atom of the ethyl group. As already said also the pharmaceutically or veterinarily acceptable salts of the compounds of formula (I) are included within the scope of the invention. The said salts may be salts with inorganic bases such as, e.g., alkali or alkaline-earth metal hydroxides, in particular sodium and potassium hydroxides, and salts with organic bases such as, e.g., triethylamine, pyridine, benzylamine or collidine, including aminoacids such as, e.g., lysine or procaine. The invention includes also internal salts, i.e. zwitterions. When R² is an esterified carboxy group it is a group COO-linked through the oxygen atom to an organic radical, such as a C₁-C₆ alkyl group, for instance methyl or ethyl; a halosubstituted C₁-C₆ alkyl group, for example 2,2,2-trichloroethyl; C₂-C₆ alkenyl group, for example allyl; an optionally substituted aryl group, for example phenyl and p-nitrophenyl; an optionally substituted aryl-C₁-C₆ alkyl group, for example benzyl, p-nitrobenzyl and p-methoxybenzyl; or groups such as benzhydryl, o-nitrobenzhydryl, acetonyl, trimethylsilyl, diphenyl-tert-butylsilyl, and dimethyl-tert-butylsilyl. The definition of R² as an esterified carboxy group includes also a carboxy group esterified with any residue, such as for instance acetoxymethyl, pivaloyloxymethyl or phthalidyl, which is known to be hydrolized "in vivo." A preferred class of compounds under this invention includes compounds of formula (I) wherein R¹ is a 1-(hydroxy)ethyl group; R² is sodium or potassium carboxylate COONa, COOK, or the carboxylate anion counterpart COO⁻ of the quaternary ammonium cation Q R³ and R⁴ are hydrogen, or each independently are hydrogen, hydroxy; X and Q are as defined above. Specific examples of preferred compounds of the invention are the acids listed in the following table, either as such or as the sodium, potassium or inner salt thereof. The compounds of formula (I) may be prepared, according to the processes of the present invention, either by cyclizing a compound of formula (II), wherein R¹, R², R³, R⁴, X and Q are as defined above, and R⁸ is either lower alkoxy, preferably methoxy or ethoxy, or aryl, preferably phenyl , or by reacting a compound of formula (III), or a protected derivative thereof, wherein R¹ and R² are as defined above and L is hydroxy group or a chlorine atom, with a compound of formula (IV), or a salt thereof, wherein R³, R⁴ and Q are as above defined and A represents HO, HS, or O=C=N. A resultant compound of formula (I) wherein Q represents hydroxy group or a halogen atom may be converted into another compound of formula I wherein Q is different by reaction with a suitable reagent, according to the individual meaning of the group Q encompassed by the present invention, i.e. with a reagent known in the art to be able to convert a benzylic alcohol or halide into a compound Ph-CH₂-Q, wherein Q is as defined above. A compound of formula (I) wherein X is sulphur atom may be converted into another compound of formula (I) wherein X is sulphinyl by reaction with an organic or inorganic oxidizing agent suitable for the conversion of a sulphide into a sulphoxide, such as, for example, m-chloroperoxybenzoic acid, peracetic acid, perphthalic acid, sodium periodate, osmium tetraoxide or hydrogen peroxide. Lastly, the optionally present protecting groups are removed, and/or an obtained compound of formula (I) is converted into a salt thereof, and/or a resultant mixture of isomers is separated into the single components. The cyclization of a compound of formula (II) into a compound of formula (I), or a protected derivative thereof, is carried out by heating the former in an inert solvent, such as toluene or xylene, preferably under nitrogen or argon, at temperatures ranging from approx. +40 °C to approx. + 140 °C. The reaction of a compound of formula (III) with a compound of formula (IV) to afford a compound of formula (I) may be carried out under known-per-se procedures, i.e. under conditions known to convert an allyl alcohol or an activated derivative thereof or an allyl chloride into a) an allyl phenyl ether, or b) an allyl benzoate, or c) an O-allyl N-phenyl carbamate, or d) an allyl phenyl carbonate, or e) an allyl phenyl sulphoxide, or f) an allyl phenyl sulphone, or g) an allyl phenyl sulphide, according to whether the X group in the compound of formula (I) is a) an oxygen atom, or b) an oxycarbonyl group, or c) an oxycarbonylamino group, or d) an oxycarbonyloxy group, or e) a sulphinyl group, or f) a sulphonyl group, or g) a sulphur atom. General procedures for the conversion of a compound of formula (I) wherein Q is hydroxy, or a protected derivative thereof, into a compound of formula (I) wherein Q, being as defined by the present invention is a quaternary ammonium group may be obtained from a compound of formula (I) wherein Q is hydroxy by converting such hydroxy group into a leaving group, preferably a triflate, which is then displaced, preferably in situ, by the parent amine to which the desired group Q corresponds. As already said , compounds of formula (I) can be prepared from compounds of formula (I) wherein Q represents halo, by reaction with the appropriate nucleophile to which the desired group Q corresponds, e.g. a tertiary or aromatic amine. The general conditions of such reactions, as well of the reaction said listed above, are those known in the art for the conversion of a benzyl halide or benzyl alcohol into a compound of formula Ph-CH₂-Q, wherein Q is as defined above. Intermediates of formula (II) are known or can be prepared starting from known compounds according to known methodologies, for example according to the methods described in J.Am.Chem.Soc. 1978, 8214 or Chem.Pharm.Bull. 1983, 768. Penem intermediates of formula (III) and reagents of formula (IV) are either known compounds or may be obtained from known compounds according to known-per-se procedures. The compounds of formula (I) provided by the present invention are broad-spectrum, potent antibacterial agents, or are useful intermediates thereof. When tested in vivo, they showed a particularly interesting pharmacokinetic profile, and a high degree of therapeutic effectiveness in treating infections caused by Gram-positive and -negative bacteria. Moreover, especially in the form of enzymatically labile esters, such as the acetoxymethyl esters, the compounds of formula (I) were found effective when administered orally. Included within the invention are therefore pharmaceutical or veterinary compositions containing the compounds of formula (I) and conventional carriers or diluents. The compounds of the formula I according to the invention are effective in vitro in the folllowing dosage ranges : against cocci (inclusive of penicillinase-formers), from 0.001 to 1 mcg/ml; against entero bacteria (inclusive of β-lactamase-formers), from 0.5 to50 mcg/ml : In vivo data for (5R,6S)-6-[(1R)-hydroxy ethyl]-2-[4-(1-pyridinio)methylphenyl]oxymethylpenem-3-carboxylate ( example 1, Compound 5,FCE 24386) Pharmacokinetios parameters A.U.C.(mcg/ml min.) t 1/2β % Absorption s.c. Mouse 3361 27' 100 Rat 6150 28' - Experimental infections in mice Strain ED₅₀(mg/kg, cumulative dose) Staphilococcus aureus Smith « 0.032 Escherichia coli G II 1.55 When tested in vivo after parenteral administration, the compounds of formuls I of the present invention showed a very high degree of therapeutic effectiveness in treating infections caused by both Gram-positive and Gram-negative bacteria, their toxicity being on the other hand quite negligible. Owing to their high antibacterial activity the compounds of the invention are thus useful, for example, in the treatment of respiratory tract infections, for example, bronchitis, bronchopneumonia, pleurisy; hepatobiliary and abdominal infections, for example, septicemia; urinary tract infections, for example, pyelonephritis, cystitis; obstetrical and gynecological infections, for instance, cervicitis, endometritis; ear, nose and throat infections, for instance otitis, sinusitis, parotitis. The compounds of the invention may be administered, either to humans or to animals, in a variety of dosage forms, e.g., orally in the form of tablets, capsules, drops or syrups; rectally in the form of suppositories; parenterally, e.g., intravenously or intramuscularly (as solutions or suspensions), with intravenous administration being preferred in emergency situation; by inhalation in the form of areosols or solutions for nebulizers; intravaginally in the form, e.g., of pessaries; or topically in the form of lotions, creams and ointments. The pharmaceutical or veterinary compostions containing the compounds of formula (I), which are too within the scope of the invention, may be prepared in a conventional way by employing the conventional carriers or diluents used for, e.g., cephalosporins. Conventional carriers or diluents are, for example, water, gelatine, lactose, starches, magnesium stearate, talc, vegetable oils, cellulose and the like. Daily doses in the range of about 0.5 to about 100 mg per kg of body weight may be used, in various animal species, the exact dose depending on the age, weight and condition of the subject to be treated and on the frequency and route of administration. A preferred way of administration of the compounds of the invention is the parenteral one: in this case the compounds may be administered, for example to adult humans, in an amount ranging from about 200 mg to about 800 mg pro dose , preferably about 400 mg pro dose , 1-4 times a day, dissolved in a suitable solvent, such as, for example, sterile water or lidocaine hydrochloride solution for intramuscular injections, and sterile water, physiological saline solution, dextrose solution or the conventional intravenous fluids or electrolytes, for intravenous injections. Furthermore, the compounds of the invention may be used as antibacterial agents in a prophylactic manner, e.g., in cleaning or as surface disinfecting compositions, for example, at a concentration of about 0.2 to 1% by weight of such compounds admixed with, suspended or dissolved in conventional inert dry or aqueous carriers for application by washing or spraying. They are also useful as nutritional supplements in animal feeds. The following examples illustrate but do not limit the present invention. Example 1 (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(1-pyridinio)methylphenyl]oxymethylpenem-3-carboxylate (Compound 5) A stirred solution of 4-hydroxymethylphenol (6,2 g) in dry dimethylformamide (100 ml) was treated sequentially with imidazole (9,5 g) and tert-butyldiphenylsilyl chloride (12.8 ml) at room temperature. The resulting solution was stirred 2 hours at room temperature, then poured into diisopropyl ether and washed twice with water. The organic layer was dried over Na₂SO₄ and the solvent removed in vacuo. Purification through a silica gel column (230-400 Mesh, n-hexane/ethyl acetate mixtures as eluant) yielded 4-tert-butyldiphenylsilyloxymethylphenol as an oil (12.0 g); NMR (60 MHz, CDCl₃)δ ppm: 1.13 (9H, s), 4.72 (2H, s), 5.53 (1H, br s, exch. D₂O), 6.73 (2H, d, J= 9.0 Hz), 7.17 (2H, d, J= 9.0 Hz), 7.3-7.7 (10H, m) A solution of diethylazodicarboxylate (4 mM) and triphenylphosphine (4 mM) in tetrahydrofuran (10 ml) was stirred at 0°C for 1 hour. This mixture was added to a solution of allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-hydroxymethylpenem-3-carboxylate (1.0 g) and 4-tert-butyldiphenylsilyloxymethylphenol (1.0 g) in dry tetrahydrofuran (20 ml) at 0°C. The resulting solution was stirred 30 minutes at room temperature, then concentrated in vacuo and purified by flash chromatography on silica gel to give allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-(4-tert-butyldiphenylsilyloxymethylphenyl)oxymethylpenem-3-carboxylate as a pale yellow syrup (600 mg). A solution of this product in tetrahydrofuran (20 ml) was stirred for 8 hours at room temperature in the presence of acetic acid (0.40 ml) and tetrabutylammonium fluoride trihydrate (0.40 g). The solvent was removed in vacuo and the residue fractionated through a silica gel column (Merck 60 HR 230 - 400 Mesh; n-hexane/ethyl acetate mixtures as eluant) to give allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-(4-hydroxymethylphenyl)oxymethylpenem-3-carboxylate (370 mg); IR (CHCl₃) ν max 1787, 1702, 1605, 1580 cm⁻¹; NMR (200 MHz, CDCl₃) δ ppm: 0.06 (6H, s), 0.86 (9H, s), 1.21 (3H, d, J= 6.4 Hz), 3.70 (1H, dd, J= 1.7 and 4.6 Hz), 4.22 (1H, dq, J= 4.6 and 6.4 Hz), 4.62 (2H, s), 4.70 (2H, m), 5.26 (1H, d, J= 10.3 Hz), 5.13 and 5.39 (2H, ABq, J= 15.6 Hz), 5.41 (1H, d, J= 17 Hz), 5.58 (1H, d, J= 1.7 Hz), 5.91 (1H, m), 6.91 and 7.29 (each 2H, d, J= 8.7 Hz). A solution of allyl (5R, 6S)-6-[(1R)-tert-butyldimethylsilyloxymethyl] -2-(4-hydroxymethylphenyl)oxymethylpenem-3-carboxylate (200 mg) in dry, ethanol-free dichloromethane (15 ml) was cooled under nitrogen to -70°C and then sequentially treated under stirring with pyridine (0.23 ml) and trifluoromethanesulphonic anhydride (0.22 ml). The reaction mixture was let rise to -5°C and then quenched with 0.1 M aqueous HCl. The organic layer was separated, washed with brine, dried and evaporated to give a gummy residue. This product was taken up in tetrahydrofuran (8 ml) and treated in sequence with acetic acid (0.55 ml) and tetrabutylammonium fluoride · 3H₂O (0.5 g). The clear solution was let stand for 20 hours at room temperature, then concentrated and passed through a silica gel column (230-400 Mesh, ⊘ 2 cm, h 8 cm). Elution with neat CH₂Cl₂, CH₂Cl₂/CH₃CN (70:30 and then 50:50) and neat acetonitrile was followed by a final washing with CH₃CN/H₂O (1:2). Addition of NaCl to the last fractions and extraction with CH₃CN, followed by concentration in vacuo, gave the crude allyl ester of the title product as a foam. This material in 5 ml of CH₂Cl₂ and 0.1 ml of acetic acid was stirred with triphenylphosphine (0.025 g) and tetrakis (triphenylphosphine) Pd (O) (0.025 g) for 30 min., after which time an additional amount of PPh₃ (0.02 g) and Pd(PPh₃)₄ (0.02 g was added to complete the reaction (further 15 min.). The reaction mixture was concentrated and the residue triturated with ethyl acetate. The obtained solid was dissolved in demineralized water and chromatographed on LiChroprep RP-18 eluting first with water and then with 10% CH₃CN in H₂O. The appropriate fractions were combined and freeze-dried to afford 30 mg of the title compound as a white powder; UV (H₂O) λ max 258 and 307 nm; IR (KBr) ν max 1765, 1600 cm⁻¹; NMR (200 MHz, D₂O)δppm: 1.22 (3H, d, J= 6.3 Hz), 3.72 (1H, dd, J= 1.5 and 6.0 Hz), 4.14 (1H, dq, J= 6.0 and 6.3 Hz), 5.02 and 5.34 (2H, each d, J= 14.4 Hz), 5.43 (1H, d, J= 1.5 Hz), 5.70 (2H, s). 6.95, 7.39 (2H, each d, J= 8.6 Hz), 8.01 (2H, dd, J= 5.6, 7.0 Hz), 8.50 (1H, t, J= 7.0 Hz), 8.87 (2H, d, J= 5.6 Hz). Example 2 By following the experimental procedure described in the above Example 1 and replacing pyridine with 2,3-cyclopentenopyridine, N-methylpyrrolidine, N-methylpiperidine, 3-methoxypyridine, 3-cyanomethylpyridine. N-methylmorpholine, quinuclidine, there were obtained, respectively: (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(2,3-cyclopenteno-1-pyridinio)methylphenyl]oxymethylpenem-3-carboxylate (Compound 8); (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4(1-methyl-1-pyrrolidinio)methylphenyl] oxymethylpenem-3-carboxylate (Compound 9); NMR (200MHz, D₂O) δ ppm 1.27 (3H, d, J = 6.3 Hz), 2.22 (4H, m), 2.93 (3H, s), 3.30-3.65 (4H, m), 3.84 (1H, d, J= 6.0 Hz), 4.23 (1H, m), 4.45 (2H, s), 5.19 and 5.51 (2H, two d, J = 14 Hz), 5.58 (1H; s), 6.95-7.55 (4H, m) UV (H₂O) λ max 308 nm IR (KBr) ν max 1760, 1605, 1580 nm (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(1-methyl-1-piperidinio)methylphenyl] oxymethylpenem-3-carboxylate (Compound 10); (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(3-methoxy-1-pyridinio)methylphenyl] oxymethylpenem-3-carboxylate (Compound 11); (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(3-cyanomethyl-1-pyridinio)methylphenyl]oxymethylpenem-3-carboxylate (Compound 12); (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-methyl-4-morpholinio)methylphenyl] oxymethylpenem-3-carboxylate (Compound 13); (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(1-quinuclidinio)methylphenyl]oxymethylpenem-3-carboxylate (Compound 14). Example 3 (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(1-pyridinio)methylphenyl]oxymethylpenem-3-carboxylate (Compound 5) A solution of 4-tert-butyldiphenylsilyloxymethylphenol (see Example 1, Step A) (13 g) and ethyl bromoacetate (4.0 ml) in acetone (50 ml) was refluxed for 40 h in the presence of sodium iodide (5.37 g) and potassium carbonate (4.69 g). The reaction mixture was partitioned between ethyl ether and water, and the dried (MgSO₄) organic phase was evaporated. Silica gel chromatography of the residue afforded ethyl 2-(4-tert-butyldiphenylsilyloxymethylphenyl)oxyacetate as a colourless syrup (8 g); IR ν max 1735 cm⁻¹; NMR (60 MHz, CDCl₃)δ 1.1 (9H, s), 1.3 (3H, t, J= 6 Hz), 4.2 (2H, q, J= 6 Hz), 4.55 and 4.65 (each 2H, s), 6.8-7.8 (10H, m). A solution of this material (7.7 g) in tetrahydrofuran (120 ml) was stirred for 30' with 10% aq. KOH (25 ml). The reaction mixture was made acidic with 10% H₂SO₄ and extracted with dichloromethane. The organic layer was washed with aq. NaCl, dried (MgSO₄) and evaporated to obtain 2-(4-tert-butyldiphenylsilyloxymethylphenyl)oxyacetic acid (7.2 g) as a yellowish oil; IR (film) ν max 3500-2500, 1725 cm⁻¹; NMR (60 MHz, CDCl₃)δ1.10 (9H, s), 4.55 and 4.60 (each 2H, s), 6.8-7.8 (10H, m), 8.2 br (1H, s). A solution of the above product (7.0 g) in dry, ethanol-free dichloromethane (120 ml) was treated at -40°C with triethylamine (2.5 ml) and ethyl chlorocarbonate (1.72 ml). After 20 minutes at the same temperature, a second amount of NEt₃ (2.5 ml) was added, and hydrogen sulfide was bubbled under stirring for 40 minutes at -20°C. The reaction mixture was let rise to room temperature and then washed with 4% aq. HCl, dried and evaporated to afford 2-(4-tert-butyldiphenylsilyloxymethylphenyl) oxyacetic S-acid (7.2 g) as a yellowish oil; IR (CHCl₃) ν max 2560, 1690 cm⁻¹ ; NMR (60 MHz, CDCl₃)δ 1.1 (9H, s), 4.2 (1H, br s), 4.4 and 4.6 (each 2H, s), 6.7-7.7 (10H, m). A solution of 2-(4-tert-butyldiphenylsilyloxymethylphenyl)oxyacetic S-acid (8.7 g) in acetone (50 ml) was sequentially treated at 10°C under stirring with 1N aq. NaOH (20 ml) and (3R)-[(1R)-tert-butyldimethylsilyloxyethyl]-(4R)-benzoyloxyazetidin-2-one (7 g). More 1N NaOH was added, as needed, to keep the pH at about 8.0 while stirring at 10°C for 15 minutes, after which time the reaction mixture was partitioned between isopropyl ether and water. The organic phase was dried, evaporated and purified by flash-chromatography, thereby obtaining (3S)-[(1R)-tert-butyldimethylsilyloxyethyl]-(4R)-(4-tert-butyldiphenylsilyloxymethylphenyl) oxyacetylthioazetidin-2-one (4.5 g); IR (CNCl₃) ν max 1760, 1680 cm⁻¹; NMR (60 MHz, CDCl₃)δ 0.05 (6H, s), 0.85 and 1.05 (each 9H, s), 1.15 (3H, d, J= 6.5 Hz), 3.15 (1H, dd, J= 2.5 and 4 Hz), 4.2 (1H, m), 4.6 (2H, s), 5.25 (1H, d, J= 2.5 Hz), 6.3 (1H, br s), 7.75-8.7 (10H, m). A solution of (3S)-[(1R)-tert-butyldimethylsilyloxyethyl]-(4R)-(4-tert-butyldiphenylsilyloxymethylphenyl)oxyacetylthioazetidin-2-one (2.5 g) and allyloxyoxalyl chloride (0.67 g) in dichloromethane was treated at 5°C with triethylamine (0.63 ml). After 45 min, the reaction mixture was washed with water, dried (MgSO₄) and evaporated, thereby obtaining crude 1-allyloxyoxalyl-(3S)-[(1R)-tert-butyldimethylsilyloxyethyl]-(4R)-(4-tert-butyldiphenylsilyloxymethylphenyl)oxyacetylthioazetidin-2-one (2.7 g); IR (CHCI₃) ν max 1810, 1755, 1710 cm⁻¹; NMR (60 MHz, CDCl₃)δ ppm: 0.03 (6H, s), 0.85 and 1.1 (each 9H, s), 1.2 (3H, d, J= 6.5 Hz), 3.4 (1H, dd), 4.3 (1H, m), 4.6-4.8 (6H, m), 5.2-5.5 (2H, m), 5.6-5.8 (1H, m), 6.02 (1H, d, J= 3.5 Hz), 6.8-7.7 (10H, m). The 1-allyloxyoxalylazetidin-2-one obtained in Step C above (2.7 g) was refluxed in toluene for 5 hours in the presence of triethyl phosphite (1.31 ml). The solvent was removed in vacuo and the crude product purified by silica gel chromatography, thereby obtaining allyl (5R,6S)-6[(1R)-tert-butyldimethylsilyloxyethyl]-2-(4-tert-butyldiphenylsilyloxymethylphenyl) oxymethylpenem-3-carboxylate (1.4 g). Selective desilylation of this material, as described in Example 1, Step B, afforded allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-(4-hydroxymethylphenoxy)methylpenem-3-carboxylate. Step E From the above material, the title product was obtained as described in Example 1, Step C. Example 4 By following the experimental procedure described in the Example 3 above, but starting from 3-tert-butyldiphenylsilyloxymethylphenol, there was obtained: (5R,6S)-6-[(1R)-hydroxyethyl]-2-[3-(1-pyridinio)methylphenoxy]methylpenem -3-carboxylate (Compound 6). Example 5 (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(1-pyridinio)methylphenoxy]methylpenem-3-carboxylate (Compound 5). Diethyl azodicarboxylate (0.992 ml) was dropped under stirring into a cold (0°C) solution of allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-hydroxymethylpenem-3-carboxylate (2.3 g), p -hydroxybenzaldehyde (702 mg) and triphenylphosphine (1.66 g) in dry THF (70 ml). The reaction mixture was let rise to room temperature while monitoring the depletion of the reagents by TLC. The solvent was removed in vacuo and the residue purified by flash-chromatography (SiO₂, cyclohexane-ethyl acetate from 9:1 to 1:2), thereby obtaining allyl(5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-(4-formylphenoxy)methylpenem-3-carboxylate (2.85 g) as a yellowish syrup; IR (CNCl₃) ν max 1790, 1695 br, 1600 cm⁻¹; NMR (CDCl₃, 200 MHz)δ ppm: 0.05 (6H, s), 0.86 (9H, s), 1.21 (3H, d, J= 6.3), 3.70 (1H, dd, J= 1.6 and 4.4 Hz), 4.23 (1H, dq, J= 4.4 and 6.3 Hz), 4.69 (2H, m), 5.21 and 5.50 (each 1H, d, J= 15.1 Hz), 5.26 (1H, d, J= 10 Hz), 5.40 (1H, d, J= 18 Hz), 5.61 (1H, d, J= 1.6 Hz), 5.92 (1H, m), 7.03 and 7.85 (each 2H, d, J= 8.9 Hz), 9.90 (1H, s). Acetic acid (1 ml) and sodium cyanoborohydride (1.2 g) were sequentially added to a solution of allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-(4-formylphenoxy)methylpenem-3-carboxylate (2.15 g) in dry tetrahydrofuran (55 ml). After 30 minutes more hydride (1.2 g) was added. The mixture was stirred for additional 20 minutes, then partitioned between water and ethyl acetate. Removal of the solvent from the dried (MgSO₄) organic layer, followed by flash-chromatography on silica, afforded allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-(4-hydroxymethylphenoxy)methylpenem-3-carboxylate (2.0 g), identical with the material described in Example 1, Step B. Step C From the above material, the title product was obtained as described in Example 1, Step C. Example 6 By following the experimental procedure described in the Example 5 above, but substituting salicylaldehyde for 4-hydroxybenzaldehyde, there was obtained: (5R,6S)-6-[(1R)-hydroxyethyl]-2-[2-(1-pyridinio)methylphenoxy]methylpenem-3-carboxylate (Compound 7). Example 7 Similarly, following the experimental procedure described in Example 5, but substituting 2,4-dihydroxybenzaldehyde for 4-hydroxybenzaldehyde, there was obtained: (5R,6S)-6-[(1R)-hydroxyethyl]-2-[2-hydroxy-4-(1-piridinio)methylphenoxy] methylpenem-3-carboxylate (Compound 17). Example 8 Sodium (5R,6S)-6-[(1R)-hydroxyethyl]-2-(4-hydroxymethylphenoxy)methylpenem-3-carboxylate (Compound 2) A solution of allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-(4-hydroxymethylphenoxy)methylpenem-3-carboxylate (0.5 g) in tetrahydrofuran (7 ml) was sequentialiy treated with acetic acid (0.25 ml) and tetrabutylammonium fluoride trihydrate (0.44 g). The mixture was stirred for 15 minutes, then let stand at room temperature for 6 hours. The solvent was removed in vacuo and the residue purified by SiO₂ chromatography to obtain the allyl ester of the title product (0.35 g). This material (0.28 g) in a mixture of tetrahydrofuran (5 ml) and dichloromethane (4 ml) was treated under stirring with triphenylphosphine (25 mg) and tetrakis(triphenylphosphine)palladium (O) (25 mg), followed by sodium 2-ethylhexanoate (0.11 g). After stirring for 30 minutes, ethyl ether was added and the precipitate separated by centrifugation. The obtained solid was dissolved in a small anount of water and passed through a reverse-phase column (Merck LiChroprep C-18) eluting with distilled water. Freeze-drying afforded the title product as a white powder (0.15 g); IR (KBr) ν max 1770, 1600 cm⁻¹. Example 9 Sodium (5R,6S)-6-[(1R)-hydroxyethyl]-2-(4-carbamoyloxymethylphenoxy) methylpenem-3-carboxylate (Compound 1) Trichloroacetyl isocyanate (0.15 ml) was added dropwise to a solution of allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-(4-hydroxymethylphenoxy)methylpenem-3-carboxylate (obtained as described in Example 1, Step B) (0.3 g) in cold (-40°C)dichloromethane. The mixture was let rise to room temperature and then concentrated in vacuo. The residue was dissolved in THF (8 ml) and treated with acetic acid (0.6 ml) and tetrabutylammonium fluoride trihydrate (0.75 g). After 20 hours at room temperature, the solvent was removed and the residue was purified by flash chromatography on silica, thus obtaining allyl (5R,6S)-6-[(1R)-hydroxyethyl]-2-(4-carbamoyloxymethylphenoxy)methylpenem-3-carboxylate (0.25 g) as an amorphous solid. Step B The above material (0.2 g) was deallylated with triphenylphosphine and tetrakis(triphenylphosphine)palladium (O) in the presence of sodium ethylhexanoate as described in Example 8. Reverse phase chromatography afforded the title product (0.13 g); IR(KBr) ν max 1760, 1715, 1605 cm⁻¹. NMR (200 MHz, D O) 1.26(3H,d,J=6.3 Hz), 3.79(1H,dd,J=1.6, 5.8 Hz), 4.19(1H,dq,J=5.8, 6.3 Hz), 4.98(2H,s), 5.44 and 5.12 (2H,ABq, J= 14.6 Hz), 5.52(1H,d,J=1.6 Hz), 6.97(2H,d,J=8.5 Hz), 7.31(2H,d, J=8.5 Hz) Example 10 Sodium (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(1-methyl-1,2,3,4-tetrazol-5-yl) thiomethylphenoxy]methylpenem-3-carboxylate (Compound 4) A mixture of triphenylphosphine (700 mg) and diethyl azodicarboxylate (0.42) in dry THF (15 ml), previously stirred at 0°C for 30 min, was added to a solution of allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-(4-hydroxymethylphenoxy)methylpenem-3-carboxylate (400 mg) and 1-methyl-5-mercapto-1,2,3,4-tetrazole (100 mg) in the same solvent (30 ml), while keeping the temperature below +10°C. After 15 min the solvent was removed in vacuo and the residue purified by chromatography on SiO₂ (cyclohexane-ethyl acetate), thus obtaining allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-[4-(1-methyl-1,2,3,4-tetrazol-5-yl)thiomethylphenoxy]methylpenem-3-carboxylate as a foam (405 mg); IR (CHCl₃) ν max 1790, 1705 cm⁻¹. Step B From the above material (0.4 g), sequential desilylation and deallylation, by the same methodology described in Example 8, provided the title compound (0.12 g), isolated as an amorphous solid after freeze-drying; IR (KBr) ν max 1765, 1605 cm⁻¹. Example 11 By following the experimental procedure described in Example 10, but replacing 1-methyl-5-mercapto-1,2,3,4-tetrazole with the appropriate nucleophile, i.e. acetic acid, succinimide, uracil, the intermediate allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-[4-(hydroxymethyl)phenoxy]methylpenem-3-carboxylate obtained as described in Example 5 was converted, respectively, into: Sodium (5R,6S)-6-[(1R)-hydroxyethyl]-2-(4-acetoxymethylphenoxy)methylpenem-3-carboxylate (Compound 3); Sodium (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(1-succinimido)methylphenoxy] methylpenem-3-carboxylate (Compound 15); Sodium (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(2,4-dioxo-3-pyrimidinyl)methylphenoxy]methylpenem-3-carboxylate (Compound 16). Example 12 (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(1-pyridiniomethyl)benzoyloxy]methylpenem-3-carboxylate (Compound 19) Diisopropyl azodicarboxylate (0.2 ml) was added to a cold (0°C) solution of ally] (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-hydroxymethylpenem-3-carboxylate (0.21 g), triphenylphosphine (0.26 g) and 4-(tert-butyldimethylsilyloxymethyl)benzoic acid (0.2 g) in dry tetrahydrofuran (10 ml). After stirring for 15 min, the reaction mixture was taken up ethyl acetate washed with a solution of acetic acid (1 ml) in water (50 ml). The organic layer was further washed with brine, dried (MgSO₄), and the solvent was evaporated. Silica gel chromatography afforded ally] (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-[4-(tert-butyldiphenylsilyloxymethyl)benzoyloxy]methylpenem-3-carboxylate in almost quantitative yield (400 mg); IR (CHCl₃) ν max 1790, 1720 cm⁻¹; NMR (60 MHz, COCl₃) δ ppm: 0.1 (6H, s), 0.9 (9H, s), 1.12 (9H, s), 1.20 (3H, d, J= 6 Hz), 3.70 (1H, dd, J= 2 and 4.5 Hz), 4.2 (1H, m), 4.6-4.8 (4H, m), 5.1-5.6 (2H, m), 5.55 (2H, ABq), 5.65 (1H, d, J= 2 Hz), 5.9 (1H, m), 7.3-8.2 (14H, m). A solution of the product from Step A (400 mg) in tetrahydrofuran (10 ml) was treated with acetic acid (0.1 ml) and tetrabutylammonium fluoride trihydrate (255 mg). After stirring for two hours, the solvent was removed in vacuo and the residue purified by flash-chromatography, thereby obtaining allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl] -2-[4-(hydroxymethyl)benzoyloxy]methylpenem-3-carboxylate as a pale yellowish, oil (250 mg); IR (CHCl₃) ν max 1790, 1720 cm⁻¹; NMR (60 MHz, CDCl₃) δ ppm: 0.05 (6H, s), 0.9 (9H, s), 1.2 (3H, d, J= 6 Hz), 2.35 5.1-5.5 (2H, m), 5.45 (2H, ABq, J= 15 Hz), 5.55 (1H, d, J= 2 Hz), 5.9 (1H, m), 7.2-8.1 (4H, m). A solution of allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-[4-(hydroxymethyl)benzoyloxy]methylpenem-3-carboxylate (250 mg) in dry, ethanol-free dichloromethane (10 ml), was sequentially treated at -40°C under nitrogen with pyridine (0.25 ml) and trifluoromethanesulphonic anhydride (0.125 ml). Work-up of the reaction mixture and sequential desilylation and deallylation, as described in Example 1, afforded the title compound (60 mg); UV (H₂O) λ max 236 and 307 nm; IR (KBr) ν max 1765, 1720, 1600 cm⁻¹; NMR (200 MHz, D₂O) δ ppm: 1.27 (3H, d, J= 6.3 Hz), 3.79 (1H, dd, J= 1.5 and 5.9 Hz), 4.21 (1H, m), 5.07 and 5.74 (2H, each d, J= 14.8), 5.51 (1H, d, J= 1.5 Hz), 5.92 (2H, s), 7.50 and 7.94 (4H, each d, J= 8.4 Hz), 8.14 (1H, dd, J= 6.5 and 7.7 Hz), 8.63 (1H, t, J= 7.7 Hz), 8.99 (1H, d, J= 6.5 Hz). Example 13 By following the experimental procedure described in the above Example 12, but substituting N-methylpyrrolidine for pyridine, there was obtained: (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(1-methyl-1-pyrrolidinio)methylbenzoyloxy]methylpenem-3-carboxylate (Compound 20). Example 14 The intermediate allyl (5R,6S)-6[(1R)-tert-butyldimethylsilyloxyethyl] -2-[4-(hydroxymethyl)benzoyloxy]methylpenem-3-carboxylate, obtained as described in Example 12, Step B, was treated with trichloroacetyl isocyanate according to the experimental procedure reported in Example 9, thereby obtaining, after removal of the protecting groups: Sodium (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(carbamoyloxymethyl)benzoyloxy] methylpenem-3-carboxylate (Compound 18). Example 15 Likewise, starting from allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-[4-(hydroxymethyl)benzoyloxy]methylpenem-3-carboxylate and 1-methyl-5-mercapto-1,2,3,4-tetrazole, and following the experimental procedure described in Example 10, there was obtained: Sodium (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(1-methyl-1,2,3,4-tetrazol-5-yl) thiomethylbenzoyloxy]methylpenem-3-carboxylate (Compound 21). Example 16 (5R,6S)-6-[(1R)-hydroxyethyl]-2-N{4-[(1-pyridinio)methyl]phenyl}carbamoyloxymethylpenem-3-carboxylate (Compound 23). A solution of 4-(tert-butyldiphenylsilyloxy)methylbenzoic acid (2 g) in dry dichloromethane (25 ml) was treated with thionyl chloride (1.1 ml) and dry DMF (3 drops). After stirring for 2 hours at room temperature, any volatile material was removed in vacuo. The crude acid chloride thus obtained was taken up in acetone (25 ml) and mixed under stirring at 0°C with a solution of sodium azide (0.97 g) in water (4 ml). After few minutes most of the acetone was removed in vacuo and the reaction mixture extracted with benzene. The organic extracts were washed with brine, dried and evaporated to small volume, leaving a concentrated solution of 4-(tert-butyldiphenylsilyloxy)methylbenzoyl azide, which was used as such for the following step; IR (film) 2155, 1705 cm⁻¹. The benzene solution of the acyl azide from the Step A above was refluxed for 4 hours. The solvent was removed in vacuo, thereby obtaining crude 4-(tert-butyldiphenylsilyloxymethyl)phenyl isocyanate; IR (film) ν max 2190 cm⁻¹. A solution of the crude 4-(tert-butyldiphenylsilyloxymethyl)phenyl isocyanate obtained from stop C above (2 g) in ethanol-free chloroform (80 ml) was sequentially treated with allyl (5R, 6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-hydroxymethylpenem-3-carboxylate (2 g) and 4-dimethylaminopyridine (0.06 g). The solution was refiuxed for 2 hours, then washed with dilute HCl and water. Removal of the solvent and chromatography afforded allyl (5R,6S)-6-[(1R)-tert-butyl dimethylsilyloxyethyl]-2-N-[4-(tert-butyldiphenylsilyloxymethyl) phenyl]carbamoyloxymethylpenem-3-carboxylate (1.9 g). A solution of the bis-silylated product from step C above (1.6 g) in THF (50 ml) was stirred with tetrabutylammonium fluoride trihydrate (0.95 g) and acetic acid (0.35 ml) until TLC (SiO₂, ethyl acetate/cyclohexane 1:2) showed almost complete depletion of the starting material. Flash chromatography of the crude product then afforded allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-N-[4-(hydroxymethyl)phenyl]carbamoyloxymethylpenem-3-carboxylate (0.6 g). Allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-N-[4-(hydroxymethyl)phenyl]carbamoyloxymethylpenem-3-carboxylate (0.1 g) in dry CH₂Cl₂ (10 ml) was sequentially treated with pyridine (0.1 ml) and triflic anhydride (0.05 ml) at -40°C under argon. After few minutes the reaction mixture was sequentially washed with diluted HCl and brine, and the solvent removed in vacuo. The residue was triturated with ether , and the intermediate pyridinium salt thereby collected (70 mg) was dissolved in THF (5 ml) and acetic acid (0.06 ml), and stirred for 30 h with tetrebutylammonium fluoride trihydrate (95 mg). The crude product obtained from removal of the solvent was poured onto a SiO₂ column, which was first eluted with CH₂Cl₂/MeCN, then with neat MeCN, then with MeCN/H₂O. The desilylated intermediate was extracted from the last fractions by washing with brine and evaporation of the organic layer. This material (50 mg) in THF/CH₂Cl₂(1 ml each) was treated with acetic acid (0.1 ml), triphenylphosphine (50 mg) and tetrakis (triphenylphosphine) Pd° (50 mg). After 15 min ethyl ether was added and the precipitate was collected, dissolved in water and passed through a LiChroprep RP-18 column, eluting with water and then with MeCN/water. Freeze-drying of the appropriate fractions afforded the title product, 25 mg ; NMR (200 MHz, D₂O) δ 1.24(3H,d,J=6.4 Hz), 3.82 (1H,dd,J=1.6 and 5.8 Hz), 4.18(1H,dq,J=5.8 and 6.4 Hz), 5.05 and 5.42(2H,ABq,J=14.6 Hz), 5.55(1H,d,J= 1.6 Hz), 5.75(2H,m), 7.43(4H,m), 8.05(2H,m), 8.53(1H,m), 8.89(2H,m). Example 17 Sodium ( 5R,6S)6-[(1R)-hydroxyethyl]-2-N-[4-(carbamoyloxymethyl) phenyl]carbamoyloxymethylpenem-3-carboxylate (Compound 22) The title product was obtained starting from allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-N-[4-(hydroxymethyl) phenyl]carbamoyloxymethylpenem-3-carboxylate, described in Example 16, stop D, and trichloroacetyl isocyanate, by following the procedure reported in Example 9. Example 18 (5R,6S)-6-[(1R)-hydroxyethyl]-2-N-{4-[(1-methylpyrrolidinio)methyl] pheny l} carbamoyloxymethylpenem-3-carboxylate (Compound 24) The title product was obtained as described in Example 16 by substituting N-methylpyrrolidine for pyridine. Example 19 (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(3,5-dimethyl-1-pyridinio)methyl phenyl]oxymethylpenem-3-carboxylate (Compound 31) A solution of allyl (5R,6S)-6-[(1R)-trimethylsilyloxyethyl]-2-[4-(bromomethyl)phenyl]oxymethylpenem-3-carboxylate (0.1 g) in dry DMF (2 ml) was stirred overnight with 3,5-dimethylpyridine (0.15 ml). The solvent was removed in vacuo and the residue triturated with ether to leave a yellowish solid (0.1 g), which was stirred for 30 min in THF/water/acetic acid (6:2:1, 9 ml). The mixture was evaporated to dryness to afford the crude allyl ester of the title product, which was then obtained by Pd-catalyzed deallylation, as described in Example 1; IR(KBr) ν max 1765, 1605 cm⁻¹ ; UV(H O)λ max 308 nm Example 20 By following the experimental procedure described in the above Example 19 and replacing 3,5-dimethylpyridine with 3-hydroxypyridine, sodium 4-pyridineethansulphonate, 3-hydroxymethylpyridine, 2-(2-hydroxyethyl)pyridine, 8-hydroxyquinoline, 8-hydroxyisoquinoline, 3-formylaminopyridine, isonicotinohydroxamic acid, 3-pyridinecarboxaldehyde, 3-pyridinealdoxime, 4-acetylpyridine oxime, 3-aminopyridine, pyrazine, 1-methyl-1,2,3-triazole, 1-methylpyrazole, thieno[2,3-c]pyridine, furo[2,3-c]pyridine, furo[3,2-c]pyridine, thieno[3,2-c)pyridine, thieno[2,3-b]pyridine, furo[2,3-b] pyridine, thieno[3,4-c]pyridine, and thiazolo[4,5-c]pyridine, there were obtained, respectively, (5R,6S)-6-[(1R)-hydroxyethyl)-2-[4-(3-hydroxy-1-pyridinio)methyl phenyl]oxymethylpenem-3-carboxylate (Compound 32); IR (KBr) ν max 1763 1600 cm⁻¹ UV (H₂O) λ max 256 and 307 nm (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(4-sulphoethyl-1-pyridinio) methylphenyl]oxymethylpenem-3-carboxylate (Compound 33); IR (KBr) ν max 1765 UV (H₂O) λ max 308 nm (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(3-hydroxymethyl-1-pyridinio) methylphenyl]oxymethylpenem-3-carboxylate (Compound 34); (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(2-hydroxyethyl-1-pyridino) methylphenyl]oxymethylpenem-3-carboxylate (Compound 35); (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(8-hydroxy-1-quinolinio)methyl phenyl]oxymethylpenem-3-carboxylate (Compound 36); (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(8-hydroxy-2-isoquinolinio) methylphenyl]oxymethylpenem-3-carboxylate (Compound 37); (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(3-formylamino-1-pyridinio) methylphenyl)oxymethylpenem-3-carboxylate (Compound 38); (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(4-hydroxyaminocarbonyl-1-pyridinio)methylphenyl]oxymethylpenem-3-carboxylate (Compound 39); (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(3-formyl-1-pyridinio)methyl phenyl)oxymethylpenem-3-carboxylate (Compound 40); (5R,6S)-6-[(1R)-hydroxyethyl)-2-[4-(3-hydroxyiminomethyl-1-pyridinio)methylphenyl)oxymethylpenem-3-carboxylate (Compound 41); (5R,6S)-6-[(1R)-hydroxyethyl]-2-{4-[4-(1-hydroxyiminoethyl)-1-pyridinio]methylphenyl}oxymethylpenem-3-carboxylate (Compound 42); (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(3-amino-1-pyridinio)methylphenyl]oxymethylpenem-3-carboxylate (Compound 43); (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(1-pyrazinio)methylphenyl]oxymethylpenem-3-carboxylate (Compound 44); (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(1-methyl-1-triazolio)methyl phenyl]oxymethylpenem-3-carboxylate (Compound 45); (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(2-methyl-1-pyrazolio)methyl phenyl]oxymethylpenem-3-carboxylate (Compound 46); (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(thieno[2,3-c]pyridinio)methyl phenyl]oxymethylpenem-3-carboxylate (Compound 47); (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(furo[2,3-c]pyridinio)methyl phenyl]oxymethylpenem-3-carboxylate (Compound 48); (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(furo[3,2-c]pyridinio)methyl phenyl]oxymethylpenem-3-carboxylate (Compound 49); (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(thieno[3,2-c]pyridinio)methyl phenyl]oxymethylpenem-3-carboxylate (Compound 50); (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(thieno[2,3-b]pyridinio)methyl phenyl]oxymethylpenem-3-carboxylate (Compound 51); (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(furo[2,3-b]pyridinio)methylphenyl]oxymethylpenem-3-carboxylate (Compound 52); (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(thieno[3,4-c]pyridinio)methyl phenyl]oxymethylpenem-3-carboxylate (Compound 53); and (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(thiazolo[4,5-c]pyridinio)methyl phenyl]oxymethylpenem-3-carborylate (Compound 54). Example 21 (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(1-pyridinio)methylphenoxy]carbonyloxymethylpenem-3-carboxylate (Compound 25) A solution of allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxy ethyl]-2-hydroxymethylpenem-3-carboxylate (400 mg) in dry dichloromethane (20 ml) was treated at -10°C under nitrogen with 4-(tert-butyldiphenylsilyloxymethyl)phenyl chlorocarbonate (500 mg) and triethylamine (0.2 ml). The reaction mixture was warmed up to room temperature, washed with aq. NaHCO₃ , dried and evaporated, Silica gel chromatography afforded allyl (5R,6S)-6-[(1R)-tert-butyl dimethylsilyloxyethyl]-2-[4-(tert-butyldiphenylsilyloxy)methylphenoxy]carbonyloxymethylpenem-3-carboxylate (0.6 g). A solution of this product in THF (20 ml) was stirred for 8 h in the presence of acetic acid (0.4 ml) and tetrabutylammonium fluoride trihydrate (0.4 g). The solvent was removed in vacuo and the residue fractionated through a silica gel column (n-hexane/ethyl acetate) to give allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-(4-hydroxymethylphenoxy)carbonyloxymethylpenem-3-carboxylate (0.35 g). The above material was sequentially reacted with pyridine/triflic anhydride, desilylated and deallylated, by following the experimental procedure described in Example 1, step C, thereby obtaining the title product as an amorphous solid (75 mg); IR(KBr) νmax 1765, 1750, 1600 cm⁻¹ ; UV(H₂O) λ max 307 nm. Example 22 (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(1-pyridinio)methylphenyl]thiomethylpenem-3-carboxylate (Compound 26) A solution of 4-methylthiobenzaldehyde (15.2 g) in methanol (200 ml) was treated at 0 °C with sodium borohydride (3.8 g). After neutralization with HCl, the reaction mixture was concentrated and partitioned between EtOAc and brine. Removal of the solvent afforded 4-methylthiobenzyl alcohol. This material (13.3 g) was treated with m-CPBA (15.5 g) in CHCl₃ (300 ml) at 0 °C. After 30 min, the solution was washed with aq. NaHCO₃ and evaporated, to afford 4-methylsulphinylbenzyl alcohol. This product (7.9 g) in dry dichloromethane (100 ml) was treated with trifluoromethanesulphonic anhydride (19.5 ml) and refluxed for 30 min. The reaction mixture was poured into ethanolic NaOH and then worked up to afford crude 4-mercaptobenzyl alcohol, a solution of which in chloroform was directly oxidized with an aqueous solution of KI (added dropwise until a persistent colour resulted). After washing with NaHSO₃ and brine, removal of the solvent afforded 4-hydroxymethylphenyl disulfide. This material (3 g) was treated with tert-butyldiphenyl silyl chloride (6.5 ml) and imidazole (5 g) in dry dimethylformamide. After 2 h at room temperature, work-up and chromatography afforded 4-tert-butyldiphenylsilyloxymethylphenyl disulfide (5.5 g) as a syrup. Immediately before use, the above disulfide (1 g) was reduced to 4-(tert-butyldiphenylsilyloxymethyl)thiophenol by brief treatment with Zn powder (1 g) in acetic acid - dichloromethane (20 ml each). The crude mercaptane thereby obtained was coupled with allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl] -2-hydroxymethylpenem-3-carboxylate, under the conditions described in Example 1, Step B. The resulting allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-(4-hydroxymethylphenyl)thiomethylpenem-3-carboxylate was treated with pyridine/triflic anhydride, desilylated and deallylated, according to the experimental procedure described in Example 1, thus obtaining the title product; IR ν max(KBr) 3300, 1765, 1600 cm⁻¹. Example 23 (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(1-pyridinio)methylphenyl]sulfinylmethylpenem-3-carboxylate (Compound 27) Allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-[4-(1-pyridinio)methylphenyl]thiomethylpenem-3-carboxylate, obtained (as the trifluoromethanesulfonate salt) as an intermediate in the process described in the previous Example 22, was dissolved in dichloromethane at -20°C and treated with 1 mol equiv. of 3-chloro peroxybenzoic acid. After depletion of the starting material, dimethylsulfide was added, the mixture was warmed up to room temperature and the solvent removed in vacuo. Sequential desilylation and deallylation, performed as described in Example 1, afforded the title product; IR νmax 1760, 1600 cm⁻¹. Example 24 (5R,6S)-6-[(1R)-hydroxyethyl]-2-[4-(1-pyridinio)methylphenyl] sulfonylmethylpenem-3-carboxylate (Compound 30) A solution of sodium 4-(hydroxymethyl)phenylsulfinate in dry THF was stirred overnight with 1 mol equiv. of allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-chloromethylpenem-3-carboxylate. The reaction mixture was partitioned between water and ethyl acetate, and the residue from the dried organic layer was purified by silica gel chromatography to obtain allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxyethyl]-2-(4-hydroxy methylphenyl)sufonylmethylpenem-3-carboxylate. Treatment of this material with pyridine / triflic anhydride, followed by sequential desilylation and deallylation, according to the procedure described in Example 1, afforded the title product; IR νmax 1765, 1605 cm⁻¹. Example 25 By sequential exposure to trichloroacetylisocyanate and deblocking of the protective groups, according to the procedure described in Example 9, allyl (5R,6S)-6-[(1R)-tert-butyldimethyl silyloxyethyl]-2-(4-hydroxymethylphenyl)sulfinylmethylpenem-3-carboxylate and allyl (5R,6S)-6-[(1R)-tert-butyldimethylsilyloxy ethyl]-2-(4-hydroxymethylphenyl)sulfonylmethylpenem-3-carboxylate were converted into, respectively, sodium (5R,6S)-6-[(1R)-hydroxyethyl]-2-(4-carbamoyloxymethyl phenyl)sulfinylmethylpenem-3-carboxylate (Compound 28), and sodium (5R,6S)-6-[(1R)-hydroxyethyl]-2-(4-carbamoyloxymethyl phenyl)sulfonylmethylpenem-3-carboxylate (Compound 29). Example 26 By following the experimental procedure described in Example 19 but replacing 3,5-dimethylpyridine with the appropriate pyridine sul phonic acids (as their sodium salts), there were obtained: Example 27 (5R, 6S)-6-[(1R)-hydroxyethyl]-2-[4-(4-carboxyl-1-pyridinio)methylphenyl]-oxymethylpenem-3-carboxylate (Compound 57) Step A: Protection of the carboxyl function present in the reactant. To a supsension of isonicotinic acid (6.15 g) in dry DMF (100 ml), triethylamine (8.4 ml) was added, and the resulting solution was stirred overnight in the presence of allyl bromide (5.1 ml). The reaction mixture was partitioned between water and ethyl acetate, and the organic layer was separated, washed with brine, dried over Na₂SO₄ and evaporated in vacuo to yield 4 allyloxycarbonylpiridine (3.1 g) as a colourless oil. NMR (90 MHz, CDCl₃)δ ppm 4.77 (2H, m), 5.24 (1H, d, J= 10 Hz), 5.37 (1H, d, J = 12 Hz), 5.94 (1H, m), 7.80 (2H, m), 8.70 (2H, m). Step B: Condensation with allyl (5R, 6S)-6-[(1R)-hydroxyethyl]-2-(4-bromomethylphenyl)oxymethylpenem-3-carboxylate. The title bromomethylphenyl intermediate (600 mg) was stirred overnight with 4-allyloxycarbonylpyridine (800 mg) in dry DMF. After removal of the solvent under hight vacuum, the residue was taken up in dichloromethane and dropped into ethyl ether. the precipitate was collected (560 mg) and used as such for the following step. Step C: Removal of the protecting groups. The crude allyl (5R, 6S)-6-[(1R)-hydroxyethyl]-2-[4-(4-allyloxycarbonyl-1-pyridinio)-methylphenyl]oxymethylpenem-3-carboxylate (bromide salt) obtained in the previous step was stirred for 30 minutes with triphenylphosphire (250 mg) and Pd(Ph₃P)₄ (250 mg) o, acetonitrile (50 mg) and acetic acid (5 ml). A further amount of PPh₃ and Pd (Ph₃P)₄ (250 mg each) was then added and the mixture was stirred for 30 minutes, after which time was diluted with ethyl ether (190 ml). The precipitated solid was collected by filtration, washed with ether, dissolved in aqueous NaHCO₃ and chromatographed on LiChroprep RP-18 eluting first with water and than with acetone-water. The appropriate fractions were combined and freeze-dried to afford 240 mg of the title compound as a white powder; NMR (200 MHz, D₂O) 1.31 (3H, d, J = 6.6 Hz), 3.98 (1H, d, J = 1.6 and 6.0 Hz), 4.26 (1H, dq, J = 6.0 and 6.6 Hz), 5.28 (2H, ABq), 5.77 (1H, d, J = 1.6 Hz), 5.84 (2H, s), 7.46 (4H, m), 8.25 (2H,m), 8.95 (2H,m); UV (H₂O) λ max 308 nm; IR (KBr) ν max 1765, 1630 cm⁻¹. Example 28 By following the experimental procedure described in Example 27, but replacing isonicotinic acid with the appropriately substituted pyridines or tertiary amines, there were obtained: Example 29 (5R, 6S)-6-[(1R)-hydroxyethyl]-2-[4-(4-dimethylamino-1-pyridinio)-methylphenyl]oxymethylpenem-3-carboxylate (Compound 70) A solution of 4-dimethylaminopyridine (1 g) and allyl (5R, 6S)-6-[(1R)-hydroxyethyl]-2-(4-bromomethylphenyl)oxymethylpenem-3-carboxyl a te (550 mg) in dry DMF (5 ml) was stirred at room temperature for 12 hours. The solvent was distilledoff under high vacuum and the residue was triturated with ethyl ether to obtain a gummy precipitate of the allyl ester (bromide salt) of the title product. Without further purification, this material was dissolved in 50 ml of dichloromethane, and acetic acid (1 ml), triphenylphosphine (0.25 g) and tetrakis (triphenylphosphine) Pd (0) (0.25 g) were added in that order. After stirring for 30 minutes, the reaction mixture was concentrated and the residue was triturated with ethyl acetate. the obtained solid was dissolved in demineralized water and chromatographed on LiChroprep RP-18 eluting first with water and then with 10% CH₃CN in water. Freeze-drying of the appropriate fractions afforded the title compound (270 mg) as a white powder. UV (H₂O) λ max 307 nm IR (KBr) λ max 1760, 1600 cm⁻¹ Example 30 By following the experimental procedure described in Example 29, but replacing 4-dimethylaminopyridine with the appropriately substituted pyridines, or with 1,4-dimethympiperazine, there were obtained: Example 31 (5R, 6S)-6-[(1R)-hydroxyethyl]-2-[4-(1-methyl-1-piperazinio) methylphenyl]oxymethylpenem-3-carboxylate (Compound 78) Step A : Protection of the NM functionality present in the reactant. A solution of allyl chloroformate (15 ml) in dry dichloromethane was added at -20°C under stirring to a solution of N-methylpiperazine (10 g) in the same solvent. After 30 minutes the temperature was let rise to + 15°C and the reaction mixture was powred into water. The organic layer was discarded, 1N NaOH was added to a pH ≧ 7, and the mixture was extracted with dichloromethane. The CH₂Cl₂ extracts were dried (MgSO₄), evaporated, and the resulting oil distilled 118°C (at 18 mmHg) to yield 4-allyloxycarbonyl-1-methylpiperazine (15.3 g). Step B : Condensation with allyl (5R, 6S)-6-[(1R)-hydroxyethyl]-2--(4-bromomethylphenyl)oxymethylpenem-3carboxylate. Condensation of the title intermediate with the above 4-allyloxycarbonyl-1-methylpiperazine was carried out as described in Example 27, step B. Step C: Removal of the protecting groups. The crude allyl (5R, 6S)-6-[ (1R)-hydroxyethyl]-2-[4-(4allyloxycarbonyl-1-methylpiperazinio)methylphenyl]oxymethylpenem-3-carboxylate bromide obtained in the previous step was treated with PPh₃/Pd(PPh₃)₄/HOAc under the conditions described in Example 27, step C. Purification by reverse-phase chromatography (Lichroprep RP-18) and freeze drying afforded the title compound: IR (KBr) ν max 1765, 1600 cm⁻¹; UV (H₂O) λ max 308 nm Example 32 By following the experimental procedure described in Example 31, but replacing 1-methylpiperazine with the appropriate (aminomethyl) pyridines, there were obtained:

Claims: Claims for the following Contracting States : AT, BE, CH, DE, FR, GB, GR, IT, LI, NL, SE An antibacterial compound of the following formula I: wherein R¹ is hydrogen or a C₁-C₄ alkyl group either unsubstituted or substituted by one or more substituents chosen from a free or protected hydroxy or halogen atom; R² is a free or esterified carboxy group or carboxylate anion, wherein the ester group is of any known type which can be hydrolized "in vivo"; R³ and R⁴ are each independently either hydrogen or hydroxy group X is either (a') an oxygen atom, or (b') an oxycarbonyl group or (c') an oxycarbonylamino group or (d') an oxycarbonyloxy (carbonate) group or (e') a sulphinyl group or (f') a sulphonyl group (g') a sulphur atom; Q is an optionally substituted quaternary ammonium group selected from the following: wherein the pyridinium, pyrrolidinium, piperidinium, morpholinium, quinuclidinium, quinolinium, isoquinolinium, pyrazinium, thieno|2,3-c|pyridinium, furo|2,3-c|pyridinium, furo|3,2-c|pyridinium, thieno|3,2-c|pyridinium, thieno|2,3-b|pyridinium, pyrazolinium, triazolinium, furo|2,3-b|pyridinium, thieno|3,4-c|pyridinium, and thiazolo|4,5-c|pyridinium rings are either unsubstituted or substituted by one or two substituents selected from C₁-C₄ alkoxy, cyano-C₁-C₄ alkyl, C₁-C₄ alkyl, hydroxy, sulpho-C₁-C₄ alkyl, hydroxy-C₁-C₄-alkyl, formylamino, formyl, hydroxyimino-C₁-C₄ alkyl, amino and carboxy-C₁-C₄ alkyl groups, and the pharmaceutically or veterinarily acceptable salts thereof. A compound of formula I as defined in claim 1 wherein R₁ is an α-hydroxyethyl group. A process for preparing a compound of formula I as defined in claim 1, which comprises: a thermal cyclizing of a compound of formula II: wherein R¹, R², R³, R⁴, X and Q are as defined in claim 1 and R⁸ is either alkoxy or aryl group; or by reacting a compound of formula (III), or a protected derivative thereof, wherein R₁ and R₂ are as defined in claim 1 and L is hydroxy group or a chlorine atom, with a compound of formula (IV) , or a salt thereof, wherein R³, R⁴ and Q are as defined in claim 1 and A represents: HO, HS, or O=C=N; optionally converting the resultant compound of formula I wherein Q represents halogen or a hydroxy group free or activated into a different compound of formula I wherein Q is different by reaction with a reagent known in the art to be able to convert a benzylic alcohol or halide into a compound of formula Ph-CH₂-Q, wherein 1 is as defined above; when necessary deprotecting the resultant compound and, if desired, salifying a free compound of formula I. A process according to claim 3, wherein said reagent for converting a benzylic alcohol or halide into a compound of formula Ph-CH₂-Q is selected from the group consisting of acyl chloride, anhydride, carboxylic acid, isocyanate, heterocyclylthiol, imide and amine. A process for preparing a compound of formula I as defined in claim 1 wherein X represents sulphinyl group, which comprises oxidation of a compound of formula: wherein R₁, R₂, R₃, R₄ and Q are as defined in claim 1, with an organic or inorganic oxidizing agent suitable for the conversion of a sulphide into a sulphoxide. A pharmaceutical or veterinary composition containing a suitable carrier and/or diluent and, as an active principle, a compound according to any one of claims 1 and 2 or a pharmaceutically or veterinarily acceptable salt thereof. Claims for the following Contracting State : ES A process for preparing an antibacterial compound of the following formula I: wherein R¹ is hydrogen or a C₁-C₄ alkyl group either unsubstituted or substituted by one or more substituents chosen from a free or protected hydroxy or halogen atom; R² is a free or esterified carboxy group or carboxylate anion, wherein the ester group is of any known type which can be hydrlized "in vivo"; R³ and R⁴ are each independently either hydrogen or hydroxy group X is either (a') an oxygen atom, or (b') an oxycarbonyl group or (c') an oxycarbonylamino group or (d') an oxycarbonyloxy (carbonate) group (e') a sulphynyl group or (f') a sulphonyl group (g') a sulphur atom; Q is an optionally substituted quaternary ammonium group selected from the following: wherein the pyridinium, pyrrolidinium, piperidinium, porpholinium, quinuclidinium, quinolinium, isoquinolinium, pyrazinium, thieno/2,3-c/pyridinium, furo/2,3-c/pyridinium, furo/3,2-c/pyridinium, thieno/3,2-c/pyridinium, thieno/2,3-b/pyridiniun, pyrazolinium, triazolinium, furo/2,3-b/pyridinium, thieno/3,4-c/pyridinium, and thiazolo/4,5-c/pyr i dinium rings are either unsubstituted or substituted by one or two substituents selected from C₁-C₄ alkoxy, cyano -C₁-C₄ alkyl, C₁-C₄ alkyl, hydroxy, sulpho-C₁-C₄ alkyl, hydroxy-C₁-C₄-alkyl, formylamino, formyl, hydroxyimino-C₁-C₄ alkyl, amino and carboxy-C₁-C₄ alkyl groups, and the phanmaceutically or veterinarily acceptable salts thereof, which comprises: a thermal cyclizing of a compound of formula II: wherein R¹, R², R³, R⁴, X and Q are as defined above and R⁸ is either alkoxy or aryl group; or reacting a compound of formula (III), or a protected derivative thereof, wherein R₁ and R₂ are as above defined and L is hydroxy group or a chloride atom with a compound of formula (IV), or a salt thereof wherein R³, R⁴ and Q are as above defined and A represents: HO, HS, or O=C=N; optionally converting the resultant compound of formula I wherein Q represents halogen or a hydroxy group free or activated into a different compound of formula I wherein Q is different by reaction with a reagent known in the art to be able to convert a bezylic alcohol or halide into a compound of formula Ph-CH₂-Q, wherein Q is as defined above; when necessary deprotecting the resultant compound and, if desired, salifying a free compound of formula I. A process according to claim 1, wherein said reagent for converting a bezylic alcohol or halide into a compound of formula Ph-CH₂-Q is selected from the group consisting of acyl chloride, anhydride, carboxylic acid, isocyanate, heterocyclylthiol, imide and amine. A process for preparing a compound of formula I as defined in claim 1 wherein X represents sulphinyl group, which comprises oxidation of a compound of formula: wherein R₁, R₂ R₃, R₄ and Q are as defined in claim 1, with an organic or inorganic oxidizing agent suitable for the conversion of a sulphide into a sulphoxide.

Inventors: ALPEGIANI MARCO, BEDESCHI ANGELO, DELLA BRUNA COSTANTINO, FRANCESCHI GIOVANNI, PERRONE ETTORE, ZARINI FRANCO, ALPEGIANI, MARCO, BEDESCHI, ANGELO, DELLA BRUNA, COSTANTINO, FRANCESCHI, GIOVANNI, PERRONE, ETTORE, ZARINI, FRANCO
Applicants: ERBA CARLO SPA, FARMITALIA CARLO ERBA S.R.L.
Application year: 1987
Main classification: C07D499
IPC codes: C07D499, A61K31, C07D519, C07D237, A61P31