PROCESS FOR PREPARING PENICILLANIC ACID DERIVATIVES

Abstract: The present invention provides a process for preparing a penicillanic acid derivative of the formula which comprises reacting lead with a halogenated penicillanic acid derivative of the formula wherein X, Y, Z and R¹ are defined in the specification. The reaction is conducted more advantageously in the presence of a metal having higher ionization tendency than lead.

Description: The present invention relates to a novel process for preparing a penicillanic acid derivative. The penicillanic acid derivative obtained in the present invention is useful, for example, as an intermediate of β-lactamase inhibitor. Conventionally, the following methods have been known to prepare a penicillanic acid derivative of the formula (II) from a halogenated penicillanic acid derivative of the formula (I), wherein X is Cl, Br or I, Y is Cl, Br, I or hydrogen atom, Z is hydrogen atom, Cl, N₃, or -SR⁵, R¹ is a protective group of carboxylic acid, R² is hydrogen or -COOR⁴, R³ is hydrogen or -COOR⁴, R⁴ is lower alkyl, R⁵ is -CN or aromatic heterocyclic ring, n is 0, 1 or 2. A method of catalytic reduction using a noble metal catalyst, method of using tin hydride compound in higher than stoichiometric amounts, method of using zinc in higher than stoichiometric amounts, electrolytic reduction method, etc. [Nature, 201 , 1124(1964), J. Chem. Soc., (C), 2123(1968), Japan Kokai Nos. 120588/1980, 169486/1982 and 63683/1986]. Further, a penicillanic acid 1,1-dioxide is known to be prepared with use of magnesium, but this method is not applicable to the preparation of an ester of the acid (Japan Kokai No. 120883/1985 and EP-A-138282. The catalytic reduction method requires a large amount of an expensive noble metal catalyst and application of hydrogen pressure, hence is not practical. Tin hydride compound is difficult to be used industrially. The method of using zinc affords the product in low purity and yield. The electrolytic reduction method uses a special apparatus and the product yield is at most 75 %. An object of the invention is to provide a process for preparing a penicillanic acid derivative of the above formula ( II ), which is free from the above defects, safe, simple, industrially advantageous and produces the derivative in a high yield. The above and other objects of the invention will become apparent from the following description. The present invention provides a process for preparing a penicillanic acid derivative of the formula which comprises reacting lead with a halogenated penicillanic acid derivative of the formula wherein X is Cl, Br or I, Y is Cl, Br, I or hydrogen atom, Z is hydrogen atom, Cl, N₃, or -SR⁵, R¹ is a protective group of carboxylic acid, R² is hydrogen or -COOR⁴, R³ is hydrogen or -COOR⁴, R⁴ is lower alkyl, R⁵ is -CN or aromatic heterocyclic ring, n is 0, 1 or 2; and the above process in which a catalytic amount of lead or lead compound is used in the presence of a metal having higher ionization tendency than lead. The present inventors have earnestly investigated to solve the above defects of the conventional methods and found lead is an excellent reducing agent for the reaction of the present invention, although lead is seldom used as a reducing agent. Further, pollution problem arising from the use of lead is obviated by use of a catalytic amount of lead or lead compound in the presence of a metal having higher ionization tendency than lead. Namely, in the present invention, the penicillanic acid derivative of the formula (II) is prepared in a high yield without accompanying side-products and with a simple procedure, by reacting the halogenated penicillanic acid derivative of the formula (I) with lead or a catalytic amount of lead or lead compound in the presence of a metal having higher ionization tendency than lead in an organic solvent or aqueous organic solvent, as required with addition of an acid. In the present invention, X is Cl, Br or I, Y is Cl, Br, I or hydrogen atom, Z is hydrogen atom, Cl, N₃, or -SR⁵. R² and R³ are the same or different and are each hydrogen atom or -COOR⁴, R⁴ is lower alkyl. Whenever used in the specification and in the claims, the term "lower alkyl" means straight-chain or branched alkyl having 1 to 8, preferably 1 to 4, carbon atoms, optionally substituted with one or more substituents, preferably from the group of halogen (e.g. Cl) and C₁-C₄-alkoxy. Examples of lower alkyls of R⁴ are methyl, ethyl, propyl, i-propyl, n-butyl and t-butyl. R⁵ is -CN or an aromatic heterocyclic ring selected from: Wherein R⁶ is methyl, ethyl, propyl, i-propyl, n-butyl, t-butyl or like lower alkyl, phenyl, -CH₂COOH or -CH₂SO₃H. In the present invention, R¹ is a protective group of carboxylic acid. Protective groups of carboxylic acid represented by R¹ are methyl, ethyl, propyl, isopropyl, butyl, t-butyl or like lower alkyl ; methyl - thiomethyl, phenacyl, p-bromophenacyl, α-methylphenacyl, p -methoxyphenacyl, N-phthalimidomethyl or like substituted methyl ; 2,2,2-trichloroethyl, 2-chloroethyl, 2-bromoethyl, 2-(trimethylsilyl)ethyl, 2-methylthioethyl, 2-(p-nitrophenylsulfenyl)ethyl, 2-(p-toluenesulfonyl)ethyl, cumyl or like substituted ethyl ; cyclopentyl, cyclohexyl or like lower (e.g. C₃-C₈) cycloalkyl; allyl, cinnamyl or like substituted allyl ; phenyl, p-methylthiophenyl or like substituted phenyl ; benzyl, triphenylmethyl, diphenylmethyl, bis(o-nitrophenyl)methyl, 9-anthrylmethyl, 2-(9,10-dioxo)anthrylmethyl, 5-dibenzosuberyl, 2,4,6-trimethylbenzyl, p-bromobenzyl, o-nitrobenzyl, p-nitrobenzyl, p-methoxybenzyl, piperonyl, 4-picolyl or like substituted benzyl ; trimethylsilyl, t-butyldimethylsilyl, triethylsilyl, i-propyldimethylsilyl, phenyldimethylsilyl or like substituted silyl. n is 0, 1 or 2. In the present invention, the halogenated penicillanic acid derivative of the above formula (I) is reacted with metallic lead. The lead metal is not limited in shape and may be selected from a wide range of forms such as powder, plate, bulk, wire or needle. Powdery metallic lead is preferably used in order to complete the reaction at lower temperature in shorter period. The particle size of powdery lead metal is selected from a wide range but is preferably about 10 to 500 mesh. The amount of the lead metal to be used is usually about 1.0 to 10 equivalent moles, preferably about 1.0 to 4.0 equivalent moles per halogen atom of the halogenated penicillanic acid derivative of the formula (I). In the invention, it is possible to extremely reduce the amount of the lead metal render the waste treatment easy and conduct the reduction at lower temperature and in shorter period, by the conjoint use of a metal or metals having higher ionization tendency than lead in the reaction system. Examples of these metals are aluminum, iron or magnesium. These metals can be used singly or in mixture of at least two of them. The metals to be used are not limited in shape and may be selected from a wide range or forms such as powder, plate, foil, bulk, wire or needle. Powdery metal is preferably used in order to proceed the reaction smoothly. The particle size of powdery metal is selected from a wide range but is preferably about 10 to 300 mesh. The amount of the metal to be used having higher ionization tendency than lead is usually about 1.0 to 50 equivalent moles, preferably about 1.0 to 5.0 equivalent moles per halogen atom of the halogenated penicillanic acid derivative of the formula (I). In case of using the metal having higher ionization tendency than lead, it is possible to use a lead compound in place of metallic lead. The above lead compound may be one containing lead having a valency of zero, two or four. Further, these compounds may be in the form of a hydrate. As the lead compound, conventionally known compounds are widely used. Examples thereof are lead fluoride, lead chloride, lead bromide, lead iodide or like lead halide, lead nitrate, lead sulfate, lead perchlorate, lead borate, lead carbonate, lead phosphate or like lead salt of inorganic acid, lead acetate, lead oxalate, lead stearate or like lead salt of aliphatic acid, lead oxide, lead hydroxide, or chelates of lead having a valency of zero, 2 or 4. Examples of ligands for the chelate are ethylenediamine tetraacetic acid, nitrilotriacetic acid or like chelating agent, ketone, ester, carboxylic acid, amine, oxime, ammonia, nitrile, organic phosphine or like compounds which coordinate with oxygen, nitrogen or phosphorus atom. These lead compounds can be used singly or in mixture of at least two of them. Although only one atom of lead or one molecule of lead compound is theoretically required, the amount thereof to be used is usually about 0.00001 to 0.5 equivalent mole, preferably about 0.0001 to 0.2 equivalent mole per halogen atom of the starting halogenated penicillanic acid derivative of the formula (I). The present reduction reaction is conducted in an organic solvent, in aqueous organic solvent, or in two phase system of water and water-insoluble organic solvent, optionally with addition of an acid. Organic solvents are selected from a wide range of compounds which dissolve the compound of the formula (I) and are inert under the reaction conditions. Examples thereof are methanol, ethanol, propanol, isopropanol, butanol, tert-butanol or like alcohol ; methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate or like lower alkyl esters of lower aliphatic acids ; acetone, methyl ethyl ketone, methyl propyl ketone, methyl butyl ketone, methyl isobutyl ketone, diethyl ketone or like ketones ; diethyl ether, ethyl propyl ether, ethyl butyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, methyl cellosolve, dimethoxyethane or like ethers ; tetrahydrofuran, dioxane or like cyclic ethers ; acetonitrile, propionitrile, butyronitrile, isobutyronitrile, valeronitrile or like nitriles ; benzene, toluene, xylene, chlorobenzene, anisole or like substituted or unsubstituted aromatic hydrocarbons ; dichloromethane, chloroform, dichloroethane, trichloroethane, dibromoethane, propylenedichloride, carbon tetrachloride, flons or like halogenated hydrocarbons ; pentane, hexane, heptane, octane or like hydrocarbons ; cyclopentane, cyclohexane, cycloheptane, cyclooctane or like cycloalkanes ; dimethyl formamide, dimethyl acetamide or like amides ; and dimethyl sulfoxide. These solvent can be used singly or in mixture of at least two of them, and may contain water as required. The amount of the solvent is usually about 0.5 to 200ℓ, preferably about 1 to 50ℓ per kg of the compound of the formula (I). Acids optionally used in the invention are inorganic acids and organic acids ranging from strong acid to weak acid. Examples thereof are hydrochloric acid, sulfuric acid, nitric acid, perchloric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid, bromous acid, bromic acid, hypochlorous acid, hypobromous acid, phosphoric acid, phosphorous acid, boric acid, silicic acid or like mineral acid, formic acid, acetic acid, propionic acid, oxalic acid, tartaric acid, benzoic acid, malic acid, malonic acid, monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, trifluoroacetic acid or like carboxylic acid, benzenesulfonic acid, toluene -sulfonic acid, naphthalenesulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, chlorosulfonic acid or like sulfonic acid, benzenesulfinic acid, toluenesulfinic acid or like sulfinic acid, ascorbic acid, Meldrum's acid, Squaric acid, pyromeconic acid, lower alkyl ester of malonic acid, lower alkyl ester of acetoacetic acid, phenol, cresol, barbituric acid or like acidic compound, etc., or a salt of the acid, aqueous solution of the salt being acidic. The reaction temperature depends on the kinds of the starting material, solvent, etc., but is usually about -20°C to 150°C, preferably about 0°C to 70°C. The present reaction sometimes proceeds more rapidly when conducted with irradiation by ultrasonic waves. After completion of the reaction, the reaction mixture is for example extracted to obtain the desired penicillanic acid derivative of the formula (II) in almost pure form. Further, the derivative can be purified as required by recrystallization, column chromatography or like usual means. The present invention has the following advantages by finding lead is an excellent reducing agent. 1. The penicillanic acid derivative can be prepared in extremely high selectivity and yield without requiring a further purification. 2. The present desired compound can be prepared with use of an easily available equipment and with a simple procedure without a special apparatus. 3. Generally, strict limitations are demanded in view of public pollution for conducting a reaction which uses a heavy metal as a reagent in industrial scale. In the present invention, it is possible to reduce the amount of lead or lead compound to an extremely small amount by conjoint use of a metal which has no pollution problem, and to make easy the treatment of the reaction waste. As stated above, the present invention provides an extremely advantageous method in industrial scale for preparing penicillanic acid derivative. The present invention will be described in greater detail with reference to examples. Example 1 In 4ml of tetrahydrofuran was dissolved Compound 1 (1080mg). Thereto was added a solution of 353mg of NH₄Cl in 1ml of water. To the mixture were added 162mg of aluminum powder, 56mg of PbCl₂ and 19mg of malic acid and reacted with stirring. The reaction was continued to 20 to 30°C of the inner temperature for 2 hours with cooling because the reaction was exothermic. After completion of the reaction, tetrahydrofuran was removed by a rotary evaporator. To the resulting concentrate was added dichloromethane and the insolubles were filtered off with use of celite. The filtrate was allowed to settle. The separated dichloromethane layer was dried over anhydrous MgSO₄ and concentrated at a reduced pressure to obtain Compound 2 in a yield of 90%. The NMR spectra were well consistent with the structure. In the above formulae, Ph is phenyl. NMR(CDCl₃, δppm) : 1.11(3H, s), 1.57(3H, s), 3.34(1H, dd, J=2Hz, 17Hz), 3.50(1H, dd, J=4Hz, 17Hz), 4.48(1H, s), 4.53(1H, dd, J=2Hz, 4Hz), 6.93(1H, s), 7.32(10H, bs) Example 2 In 4ml of dichloromethane was dissolved Compound 1 (1000mg). Thereto was added a solution of 350mg of NH₄Cl in 1ml of water. To the mixture were added 160mg of aluminum powder and 10mg of lead powder and reacted with stirring. The reaction was continued at 20 to 30°C of the inner temperature for 1.5 hours. After completion of the reaction, the mixture was allowed to settle, The separated dichloromethane layer was dried over anhydrous MgSO₄ and concentrated at a reduced pressure to obtain Compound 2 in a yield of 92%. The NMR spectra were well consistent with the structure. Example 3 In 40ml of dichloromethane was dissolved Compound 1 (10.8g). Thereto was added a solution of 2.4g of NH₄Cl in 10ml of water. To the mixture were added 1.2g of aluminum powder and 0.1g of PbCl₂ and reacted with stirring. The reaction was continued at 20 to 30°C of the inner temperature for 2 hours. After completion of the reaction, the mixture was allowed to settle. The separated dichloromethane layer was dried over anhydrous MgSO₄ and concentrated at a reduced pressure to obtain Compound 2 in a yield of 95%. The NMR spectra were well consistent with the structure. Example 4 Compound 2 was prepared from Compound 1 in the same manner as in Example 1 except that acetone was used in place of tetrahydrofuran. Example 5 In 0.9ml of methanol was dissolved Compound 3 (99mg). Thereto was added 0.1ml of 1% of hydrobromic acid. To the mixture were added 12mg of finely cut aluminum foil and 7.2mg of PbBr₂ and the mixture was reacted at room temperature with stirring. Upon consumption of all of aluminum foil, 2ml of 1N-HCl was added to the reaction mixture and the mixture was extracted with 5ml of ethyl acetate. The ethyl acetate layer was washed with saturated aqueous solution of each of sodium hydrogencarbonate and sodium chloride, dried over anhydrous sodium sulfate and concentrated at a reduced pressure to obtain Compound 4 in a yield of 92%. The NMR spectra were well consistent with the structure. NMR(CDCl₃, δppm) : 1.25(3H, s), 1.54(3H, s), 3.35(1H, dd, J=2Hz, 17Hz), 3.53(1H, dd, J=4Hz, 17Hz), 3.80(3H, s), 4.35(1H, sH), 4.55(1H, dd, J= 2Hz, 4Hz), 5.10 and 5.15(2H, ABq, J=12Hz), 6.87(2H, d, J=10Hz), 7.28(2H, d, J=10Hz) Example 6 In a solvent mixture of 1ml of dichloromethane and 0.8ml of methanol was dissolved Compound 5 (201mg). Thereto was added 0.2ml of 1% of hydrobromic acid. To the mixture were added 23.4mg of finely cut aluminum foil and 14.3mg of PbCl₂ and the mixture was reacted at room temperature with stirring. Upon consumption of all of aluminum foil, 2ml of 1N-HCl was added to the reaction mixture and the mixture was extracted with 20ml of ethyl acetate. The ethyl acetate layer was washed with saturated aqueous solution of each of sodium hydrogencarbonate and sodium chloride, dried over anhydrous sodium sulfate and concentrated at a reduced pressure to obtain Compound 6 in a yield of 90%. The NMR spectra were well consistent with the structure. NMR(CDCl₃, δppm) : 1.22(3H, s), 3.22(1H, dd, J=2Hz, 17Hz), 3.58(1H, dd, J=4Hz, 17Hz), 3.74(5H, s), 4.51(1H, dd, J=2Hz, 4Hz), 4.70(1H, s), 4.98 and 5.20(2H, ABq, J=11Hz), 6.79(2H, d, J=8Hz), 7.23(2H, d, J=8Hz) Example 7 Compound 4 was obtained in a yield of 90% in the same manner as in Example 5 with the exception of using Compound 7 as a starting material. Examples 8 to 15 The reactions were conducted in the same manner as in Example 5 with use of Compound (I) listed in Table 1. Products (II) listed in Table 1 were obtained in high yields and selectivities.

Claims: A process for preparing a penicillanic acid derivative of the formula which comprises reacting lead with a halogenated penicillanic acid derivative of the formula wherein X is Cl, Br or I, Y is Cl, Br, I or hydrogen atom, Z is hydrogen atom, Cl, N₃, or -SR⁵, R¹ is a protective group of carboxylic acid, R² is hydrogen or -COOR⁴, R³ is hydrogen or -COOR⁴, R⁴ is straight-chain or branched alkyl of 1 to 8 carbon atoms, R⁵ is -CN or an aromatic heterocyclic ring selected from: wherein R⁶ is straight-chain or branched alkyl of 1 to 8 carbon atoms, phenyl, -CH₂COOH or -CH₂SO₃H, and n is 0, 1 or 2. A process for preparing a penicillanic acid derivative of the formula ( II ) which comprises reacting a catalytic amount of lead or lead compound with a halogenated penicillanic acid derivative of the formula (I), in the presence of a metal having higher ionization tendency than lead. A process as defined in claim 2 wherein the metal having higher ionization tendency than lead is aluminum, iron, magnesium or a mixture thereof. A process as defined in claim 3 wherein the metal having higher ionization tendency than lead is aluminum.

Inventors: KASE, KENJI C/O OTSUKA KAGAKU K.K., KAWAHARA, ICHIRO C/O OTSUKA KAGAKU K.K., MATSUMURA, KIYOTOSHI C/O OTSUKA KAGAKU K.K., NAKAI, AKIRA, SASAOKA, MICHIO C/O OTSUKA KAGAKU K.K., SUSUKI, DAISUKE C/O OTSUKA KAGAKU K.K., TANAKA, HIDEO, TANAKA, MOTOAKI, TANIGUCHI, MASATOSHI C/O OTSUGA KAGAKU K.K., TORII, SHIGERU
Applicants: OTSUKA KAGAKU KABUSHIKI KAISHA, TAIHO PHARMACEUTICAL COMPANY LIMITED
Application year: 1988
Main classification: C07D499
IPC codes: C07D499, B01J27, C07B61, B01J23