3,4-DISUBSTITUTED-2-AZETIDINONE DERIVATIVES AND PROCESSES FOR THE PREPARATION THEREOF

Abstract: 3,4-Disubstituted-2-azetidinone derivatives of the formula: in which R¹ is hydrogen or imino-protective group, R² is hydroxy(lower)alkyl or protected hydroxy(lower)alkyl R³ is lower alkyl, and R⁴ is 1-(lower)alkyl-1-hydroxy(C₂-C₆)alkyl, 1-(lower)alkyl-1-(protected hydroxy)­ (C₂-C₆)alkyl or 2-thioxothiazolidin-3-yl, and salts thereof and processes for the preparation therof.

Description: The present invention relates to novel 3,4-disubstituted-2-azetidinone derivatives and salts thereof, and to processes for the preparations thereof. More particularly, the present invention relates to novel 3,4-disubstituted-2-azetidinone derivatives and salts thereof, which are useful as intermediates for the production of antimicrobial agents, and to processes for the preparations thereof. Accordingly, one object of the present invention is to provide novel 3,4-disubstituted-2-azetidinone derivatives and salts thereof, which are useful intermediates for the production of 1-(lower)alkylcarbapenem compounds having high antimicrobial activities against a number of pathogenic microorganisms. Another object of the present invention is to provide processes for the preparations of 3,4-disubstituted-2-azetidinone derivatives and salts thereof. The 3,4-disubstituted-2-azetidinone derivatives of the present invention can be represented by the following general formula: in which R¹ is hydrogen or imino-protective group, R² is hydroxy(C₁-C₆)alkyl or protected hydroxy(C₁-C₆)alkyl, R³ is C₁-C₆ alkyl, and R⁴ is 1-(C₁-C₆)alkyl-1-hydroxy(C₂-C₆)alkyl, 1-(C₁-C₆)alkyl-1-(protected hydroxy)(C₂-C₆)alkyl or 2-thioxothiazolidin-3-yl. In the object compound (I) of the present invention, it is to be understood that there may be one or more stereoisomeric pair(s) such as optically active isomers due to asymmetric carbon atoms at the third and fourth positions of the 2-azetidinone ring and in the substituent of the fourth position thereof, and such isomers are also included within the scope of the present invention. However, among the object compound (I) of the present invention, the compound represented by the following chemical formula (I′) may be the most preferable and the preparation of the compound (I′) proceeded in a highly stereoselective manner. in which R¹, R², R³ and R⁴ are each as defined above, or salts thereof. Accordingly, the characteristics of the present invention consist mainly in the optically active compound of the above-identified formula (I′) and also in the novel process for the preparation thereof. Suitable salts of the object compounds (I) and (I′) may include conventional salts with a base such as an inorganic base salt, for example, an alkali metal salt (e.g. sodium salt, potassium salts According to the present invention, the object compound (I) and salts thereof can be prepared by the processes as illustrated by the following reaction schemes. (1) Process 1 : (2) Process 2 : (3) Process 3 : in which R¹, R², R³ and R⁴ are each as defined above, R 1 / a is imino-protective group, R 4 / a is 1-(C₁-C₆)alkyl-1-(protected hydroxy)(C₂-C₆)alkyl, R 4 / b is 1-(C₁-C₆)alkyl-1-hydroxy(C₂-C₆)alkyl, and R⁵ is acyl. The object compound (I) and salts thereof can be converted to the known key-intermediates for the production of antimicrobial 1-(lower)alkylcarbapenem compounds according to the following methods. (A) Method A : (B) Method B : (C) Method C : (D) Method D in which R¹, R 1 / a, R², R³ and R 4 / b are each as defined above, R 4 / c is 2-thioxothiazolidin-3-yl, R⁶ is hydrogen or C₁-C₆ alkyl, and R⁷ is protected carboxy. In the above and subsequent descriptions of the present specification, suitable examples and illustrations of the various definitions which the present invention includes within the scope thereof are explained in detail as follows. The term "lower" is intended to mean 1 to 6 carbon atoms, unless otherwise indicated. Suitable "imino-protective group" may include ar(C₁-C₆)alkyl such as mono- or di- or triphenyl(C₁-C₆)alkyl (e.g. benzyl, benzhydryl, trityl, etc.), acyl such as carbamoyl, aliphatic acyl, aromatic acyl, heterocylic acyl and aliphatic acyl substituted with aromatic or heterocyclic group(s) derived from carboxylic, carbonic, sulfonic and carbamic acids. The aliphatic acyl may include saturated or unsaturated, acyclic or cyclic ones, for example, alkanoyl such as lower alkanoyl (e.g. formyl, acetyl, propionyl, butyryl, isobutyryl, valeryl, isovaleryl, pivaroyl, hexanoyl, .), alkylsulfonyl such as lower alkylsulfonyl (e.g. mesyl, ethylsulfonyl, propylsulfonyl, isopropylsulfonyl, butylsulfonyl, isobutylsulfonyl, pentylsulfonyl, hexylsulfonyl, etc.), N-alkylcarbamoyl (e.g. methylcarbamoyl, ethylcarbamoyl..), alkoxycarbonyl such as lower alkoxycarbonyl (e.g. methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, tert-butoxycarbonyl.), alkoxyoxalyl such as lower alkoxyoxalyl (e.g. methoxalyl, ethoxalyl, propoxyoxalyl, butoxyoxalyl, etc.), alkenoyl such as lower alkenoyl (e.g. acryloyl, methacryloyl, crotonoyl.), cycloalkanecarbonyl such as cyclo(lower)alkanecarbonyl (e.g. cyclopropanecarbonyl, cyclopentanecarbonyl, cylohexanecarbonyl..).. The aromatic acyl may include aroyl (e.g. benzoyl, toluoyl, xyloyl, etc.), N-arylcarbamoyl (e.g. N-phenylcarbamoyl, N-tolylcarbamoyl, N-naphthylcarbamoyl, etc.), arenesulfonyl (e.g. benzenesulfonyl, tosyl.). The heterocyclic acyl may include heterocyclic carbonyl (e.g. furoyl, thenoyl, nicotinoyl, isonicotinoyl, thiazolylcarbonyl, thiadiazolylcarbonyl, tetrazolylcarbonyl,.). The aliphatic acyl substituted with aromatic group(s) may include aralkanoyl such as phenyl(C₁-C₆)alkanoyl (e.g. phenylacetyl, phenylpropionyl, phenylhexanoyl..), aralkoxycarbonyl such as phenyl(C₁-C₆)alkoxycarbonyl (e.g. benzyloxycarbonyl, phenethyloxycarbonyl.), aralkoxyoxalyl such as phenyl(C₁-C₆)alkoxyoxalyl (e.g. benzyloxyoxalyl.), aryloxyalkanoyl such as phenoxy(lower)alkanoyl (e.g. phenoxyacetyl, phenoxypropionyl.). The aliphatic acyl substituted with heterocyclic group(s) may include heterocyclic-alkanoyl such as heterocyclic-(C₁-C₆)alkanoyl (e.g. thienylacetyl, imidazolylacetyl, furylacetyl, tetrazolylacetyl, thiazolylacetyl, thiadiazolylacetyl, thienylpropionyl, thiadiazolylpropionyl.). These acyl groups may be further substituted with one or more suitable substituents such as C₁-C₆ alkyl (e.g. methyl, ethyl, propyl, isopropyl, butyl, pentyl, hexyl), halogen (e.g. chlorine, bromine, iodine, fluorine), C₁-C₆ alkoxy (e.g. methoxy, ethoxy, propoxy, isopropoxy, butoxy, pentyloxy, hexyloxy.), C₁-C₆ alkylthio (e.g. methylthio, ethylthio, propylthio, isopropylthio, butylthio, pentylthio, hexylthio.), nitro, and preferable acyl having such substituent(s) may be mono(or di or tri)haloalkanoyl (e.g. chloroacetyl, bromoacetyl, dichloroacetyl, trifluoroacetyl), mono(or di or tri)haloalkoxycarbonyl (e.g. chloromethoxycarbonyl, dichloromethoxycarbonyl, 2,2,2-trichloroethoxycarbonyl, etc.), nitro(or halo or C₁-C₆ alkoxy)aralkoxycarbonyl (e.g. nitrobenzyloxycarbonyl, chlorobenzyloxycarbonyl, methoxybenzyloxycarbonyl), nitro(or halo or C₁-C₆ alkoxy)aralkoxyoxalyl (e.g. nitrobenzyloxyoxalyl), mono(or di or tri)halo(C₁-C₆)alkylsulfonyl (e.g. fluoromethylsulfonyl, difluoromethylsulfonyl, trifluoromethylsulfonyl, trichloromethylsulfonyl). More preferable example of "imino-protective group" thus defined may be ar(C₁-C₄)alkyl, phenyl- or nitrophenyl(C₁-C₄)alkoxyoxalyl and (C₁-C₄)alkoxyoxalyl and the most preferable one may be ethoxalyl. Suitable hydroxy(C₁-C₆)alkyl may include straight or branched C₁-C₆ alkyl having hydroxy group such as hydroxymethyl, hydroxyethyl, hydroxypropyl, 1-(hydroxymethyl)ethyl, 1-hydroxy-1-methylethyl, hydroxybutyl, hydroxypentyl, hydroxyhexyl, in which more preferable example may be hydroxy(C₁-C₄)alkyl and the most preferable one may be 1-hydroxyethyl. Suitable "protected hydroxy(C₁-C₆)alkyl" means aforementioned hydroxy(C₁-C₆)alkyl, in which the hydroxy group is protected by a conventional hydroxy-protective group such as acyl mentioned in the explanation of imino-protective group; ar(C₁-C₆)alkyl, for example, mono- or di- or triphenyl(C₁-C₆)alkyl (e.g. benzyl, benzhydryl, trityl), trisubstituted silyl, for example, tri(lower)alkylsilyl (e.g. trimethylsilyl, triethylsilyl, isopropyldimethylsilyl, t-butyldimethylsilyl, diisopropylmethylsilyl), triarylsilyl (e.g. triphenylsilyl), triar(C₁-C₆)alkylsilyl, (e.g. tribenzylsilyl). More preferable example of the protected hydroxy(lower)alkyl thus defined may be tri(C₁-C₄)alkylsilyloxy(C₁-C₄)alkyl, phenyl- or nitrophenyl(C₁-C₄)alkoxycarbonyloxy(C₁-C₄)alkyl and the most preferable one may be 1-(t-butyldimethylsilyloxy)ethyl. Suitable C₁-C₆ alkyl may include straight or branched one such as methyl, ethyl, propyl, isopropyl, butyl, t-butyl, pentyl, hexyl, in which more preferable example may be C₁-C₄ alkyl and the most preferable one may be methyl. Suitable 1-(C₁-C₆)alkyl-1-hydroxy(C₂-C₆)alkyl may include 1-methyl-1-hydroxyethyl, 1-ethyl-1-hydroxyethyl, 1-propyl-1-hydroxypropyl, 1-butyl-1-hydroxybutyl, 1-isopropyl-1-hydroxy-2-methylpropyl, 1-methyl-1-hydroxypentyl, 1-ethyl-1-hydroxy-2-(or 3-)methylbutyl, 1-pentyl-1-hydroxy-2,2-dimethylpropyl, 1-hexyl-1-hydroxyhexyl, in which more preferable one may be 1-(C₁-C₄)alkyl-1-hydroxy(C₂-C₄)alkyl and the most preferable one may be 1-methyl-1-hydroxyethyl. Suitable "1-(C₁-C₆)alkyl-1-(protected hydroxy)(C₂-C₆)alkyl" means aforementioned 1-(C₁-C₆)alkyl-1-hydroxy(C₂-C₆)alkyl, in which the hydroxy group is protected by a conventional hydroxy-protective group as mentioned above, in which preferable example may be 1-(C₁-C₄)alkyl-1-[tri(C₁-C₄)alkylsilyloxy](C₂-C₄)alkyl and 1-(C₁-C₄)alkyl-1-[phenyl- or nitrophenyl(C₁-C₄)alkoxycarbonyloxy](C₂-C₄)alkyl, and the most preferable one may be 1-methyl-1-(trimethylsilyloxy)ethyl. Suitable "acyl" may be the aforementioned acyl as exemplified for the imino-protective group, in which more preferable example may be C₁-C₄ alkanoyl and the most preferable one may be acetyl. Suitable "protected carboxy" may include esterified carboxy such as lower alkoxycarbonyl (e.g. methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, isopropoxycarbonyl, butoxycarbonyl, tert-butoxycarbonyl), mono(or di or tri)phenyl(C₁-C₆)alkoxycarbonyl which may have a nitro group (e.g. benzyloxycarbonyl, 4-nitrobenzyloxycarbonyl, phenethyloxycarbonyl, benzhydryloxycarbonyl, trityloxycarbonyl), in which more preferable example may be phenyl- or nitrophenyl(C₁-C₄)alkoxycarbonyl and the most preferable one may be 4-nitrobenzyloxycarbonyl. The processes for the preparation of the object compound (I) of the present invention are explained in detail in the following. (1) Process 1 The compound (I) or salts thereof can be prepared by reacting the compound (II) or salts thereof with the compound (III) or salts thereof, in the presence of an enolizating agent. Suitable salts of compounds (II) and (III) may be the same as those for the compound (I). Suitable enolizating agent may include tin compound such as stannous (lower)alkylsulfonate which may have halogens such as stannous polyhalo(lower)alkylsulfonate, preferably stannous perhalo(C₁-C₄)alkylsulfonate (e.g. stannous trifluoromethanesulfonate. The reaction may also be carried out in the presence of an inorganic or organic base such as an alkali metal bicarbonate (e.g. sodium bicarbonate, potassium bicarbonate), alkali metal carbonate (e.g. sodium carbonate, potassium carbonate), alkaline earth metal carbonate (e.g. magnesium carbonate, calcium carbonate), tri(lower)alkylamine (e.g. trimethylamine, triethylamine, N,N-diisopropyl-N-ethylamine), pyridine compounds {e.g. pyridine, picoline, lutidine, N,N-di(lower)alkylaminopyridine such as N,N-dimethylaminopyridine}, quinoline, imidazole, N-(lower)alkylmorpholine (e.g. N-methylmorpholine), N-lower alkylpiperidine (e.g. N-ethylpiperidine), N,N-di(lower)alkylbenzylamine (e.g. N,N-dimethylbenzylamine,). This reaction is usually carried out in a conventional solvent which does not adversely influence the reaction such as dioxane, acetonitrile, chloroform, dichloromethane, hexamethylphosphoric triamide, dichloroethane, tetrahydrofuran, ethyl acetate, dimethylsulfoxide, N,N-dimethylformamide, pyridine, etc., or a mixture thereof. The reaction temperature of this reaction is not critical and the reaction is usually carried out under from cooling to warming. This reaction can be carried out in the presence of zinc halide (e.g. zinc chloride, zinc bromide, zinc iodide). (2) Process 2 The compound (I-b) or salts thereof can be prepared by subjecting the compound (I-a) or salts thereof to removal reaction of the hydroxy-protective group in R 4 / a. Suitable salts of the compounds (I-b) and (I-a) may be the same as those for the compound (I). This removal reaction is carried out by a conventional method such as hydrolysis, reduction, which can be selected according to the kind of hydroxy-protective group to be removed. (i) Hydrolysis : Hydrolysis is preferably carried out in the presence of a base or an acid. Suitable base may include an alkali metal hydroxide (e.g. sodium hydroxide, potassium hydroxide), an alkaline earth metal hydroxide (e.g. magnesium hydroxide, calcium hydroxide), alkali metal hydride (e.g. sodium hydride, potassium hydride), alkaline earth metal hydride (e.g. calcium hydride), alkalimetal alkoxide (e.g. sodium methoxide, sodium ethoxide, potassium t-butoxide), an alkali metal carbonate (e.g. sodium carbonate, potassium carbonate), an alkaline earth metal carbonate (e.g. magnesium carbonate, calcium carbonate), an alkali metal bicarbonate (e.g. sodium bicarbonate, potassium bicarbonate. Suitable acid may include an organic acid (e.g. formic acid, oxalic acid, acetic acid, propionic acid, trifluoroacetic acid, benzenesulfonic acid, p-toluenesulfonic acid) and an inorganic acid (e.g. hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid). The acidic hydrolysis using trifluoroacetic acid is usually accelerated by addition of cation trapping agent (e.g. phenol, anisole). In case that the hydroxy-protective group is tri(C₁-C₆)alkylsilyl, the hydrolysis can also be carried out in the presence of tetra(lower)alkylammonium halide (e.g. tetrabutylammonium fluoride). This reaction is usually carried out in a conventional solvent which does not adversely influence the reaction such as water, alcohol (e.g. methanol ethanol), tetrahydrofuran, dioxane, acetone, etc., or a mixture thereof. A liquid base or acid can also be used as the solvent. The reaction temperature is not critical and the reaction is usually carried out under from cooling to warming. (ii) Reduction : The reduction method applicable to this removal reaction may include, for example, reduction by using a combination of a metal (e.g. zinc, zinc amalgam) or a salt of chrome compound (e.g. chromous chloride, chromous acetate) and an organic or inorganic acid (e.g. acetic acid, propionic acid, hydrochloric acid, sulfuric acid,), and conventional catalytic reduction in the presence of a conventional metallic catalyst such as palladium catalysts (e.g. spongy palladium, palladium black, palladium oxide, palladium on carbon, colloidal palladium, palladium on barium sulfate, palladium on barium carbonate), nickel catalysts (e.g. reduced nickel, nickel oxide, Raney nickel), platinum catalysts (e.g. platinum plate, spongy platinum, platinum black, colloidal platinum, platinum oxide, platinum wire). In case that the catalytic reduction is applied, the reaction is preferably carried out around neutral condition. The reaction is usually carried out in a conventional solvent which does not adversely influence the reaction such as water, alcohol (e.g. methanol ethanol, propanol), dioxane, tetrahydrofuran, acetic acid, buffer solution (e.g. phosphate buffer, and the like, or a mixture thereof. The reaction temperature is not critical and the reaction is usually carried out under from cooling to warming. (3) Process 3 The compound (I-d) or salts thereof can be prepared by introducing the imino-protective group into the compound (I-c) or salts thereof. Suitable salts of the compounds (I-d) and (I-c) may be the same as those for the compound (I). Suitable introducing agent of the imino-protective group may be a conventional one which can introduce an imino-protective group such as acyl mentioned above, into the compound (I-c), in which more preferable example may be (C₁-C₄)alkyl oxalyl halide (e.g. ethyl oxalyl chloride). This reaction can be carried out in the presence of a base such as that exemplified in the explanation of Process 1. This reaction is usually carried out in a conventional solvent which does not adversely influence the reaction such as dichloromethane, chloroform, ethyl acetate, tetrahydrofuran, dioxane, acetone, etc., or a mixture thereof. The reaction temperature is not critical and the reaction is usually carried out under from cooling to warming. The methods A to D for the production of the known key intermediates for the 1-(lower)alkylcarbapenem compounds are explained in detail in the following. (A) Method A The compound (A-1) or salts thereof can be prepared by reacting the compound (I-b) or salts thereof with an oxidizing agent. Suitable salts of the compound (A-1) may be the same as those for the compound (I). Suitable oxidizing agent may include a conventional one such as perhalogenic acid (e.g. periodic acid) or a salt thereof, which can oxidize α-hydroxyketone into carboxylic acid (-COOH). Suitable salt of perhalogenic acid may be a salt with a base such as an inorganic base salt , for example, an alkali metal salt (e.g. sodium salt, potassium salt, lithium salt), and the like. This reaction is usually carried out in a conventional solvent which does not adversely influence the reaction such as tetrahydrofuran, dioxane, water, alcohol (e.g. methanol, ethanol), buffer solution (e.g. phosphate buffer, acetate buffer)., or a mixture thereof. The reaction temperature is not critical and the reaction is usually carried out under from cooling to warming. (B) Method B The compound (A-2) or salts thereof can be prepared by solvolysing the compound (I-e) or salts thereof. Suitable salts of the compounds (A-2) and (I-e) may be the same as those for the compound (I). The solvolysis may include hydrolysis, alcoholysis, and the like, and can be carried out in substantially the same manner as that of hydrolysis exemplified in the explanation of Process 2, and therefore, the reaction conditions (e.g. a base or an acid to be used, solvent, reaction temperature) are to be referred to the said explanation. The alcoholysis is usually carried out in a conventional lower alcohol such as methanol, ethanol, propanol. (C) Method C The compound (A-4) or salts thereof can be prepared by subjecting the compound (A-3) or salts thereof to removal reaction of the imino-protective group. Suitable salts of the compounds (A-4) and (A-3) may be the same as those for the compound (I). This reaction is usually carried out by a conventional method such as solvolysis, reduction. The method of solvolysis and reduction, and the reaction conditions (e.g. solvent, reaction temperature) are substantially the same as those illustrated for removal reaction of hydroxy-protective group of the compound (I-a) in Process 2 and the solvolysis of the compound (I-e) in Method B, and therefore are to be referred to the said explanation. (D) Method D The compound (A-5) or salts thereof can be prepared by reacting the compound (I-e) or salts thereof with compound (IV). Suitable salts of the compound (A-5) may be the same as those for the compound (I). This reaction can be carried out in the presence of an base as exemplified for the explanation of Process 1. This reaction is usually carried out in a conventional solvent which does not adversely influence the reaction such as water, dichloromethane, acetonitrile, alcohol (e.g. methanol, ethanol), tetrahydrofuran, dioxane, acetone, or a mixture thereof. The reaction temperature is not critical and the reaction is usually carried out under from cooling to heating. The compounds (A-1), (A-2), (A-4) and (A-5) produced in the above Methods A to D can be transformed by known methods into antimicrobial 1-(lower)alkylcarbapenem compounds. The object compound (I), especially the optically active compound (I′), of the present invention is useful intermediates for the preparation of the above known key intermediates, and further the process of the present invention is also useful for the preparation of such optically active compound. The following examples are given for the purpose of illustrating this invention in more detail. Example 1 To a suspension of stannous trifluoromethanesulfonate (8.35 g) and N-ethylpiperidine (3.79 ml) in dichloromethane (60 ml) was added dropwise a solution of 3-propionyl-2-thioxothiazolidine (4.12 g) in dichloromethane (35 ml) at -78°C under nitrogen atmosphere. After stirring at -78°C for 30 minutes, a solution of (3R,4R)-4-acetoxy-3-[(1R)-1-(t-butyldimethylsilyloxy)ethyl]-2-azetidinone (2.25 g) in dichloromethane (8 ml) was added to the reaction mixture, and the reation mixture was stirred at 0°C for 30 minutes and then at room temperature for 20 minutes. The reaction mixture was poured into aqueous sodium bicarbonate solution (100 ml) and the precipitated white mass was removed by passing through a layer of celite. The organic layer was separated and washed with 10% aqueous sodium chloride solution (100 ml x2). The organic solution was dried over magnesium sulfate and evaporated. The residue was chromatographed on silica gel (185 g) eluting with a mixture of acetone and dichloromethane (2:98, V/V) to give (3S,4R)-3-[(1R)-1-(t-butyldimethylsilyloxy)ethyl]-4-[(1RS)-1-methyl-2-oxo-2-(2-thioxothiazolidin-3-yl)ethyl]-2-azetidinone (2.39 g). IR (CH₂Cl₂) : 1760, 1690 cm⁻¹ NMR (CDCl₃, δ) : 0.07 (6H, s), 0.87 (9H, s), 1.17 (3H, d, J=4.5Hz), 1.27 (3H, d, J=4.5Hz), 2.77 (0.17H, dd, J=6.0, 3.0Hz) 3.00 (0.83H, dd, J=4.5, 3.0Hz), 3.26 (2H, t, J=6.5Hz), 3.92 (1H, dd, J=4.5, 3.0Hz), 4.16 (1H, dq, J=6.0, 4.5Hz), 4.53 (2H, t, J=6.5Hz), 4.93 (1H, dq, J=6.5, 4.5Hz), 6.20 (1H, br s) The above NMR data show the ratio of (1R)-1-methyl isomer to (1S)-1-methyl isomer is 4.9:1. Example 2 To a suspension of stannous trifluoromethanesulfonate (1.63 g) and N-ethylpiperidine (0.827 ml) in dichloromethane (12 ml) was added dropwise a solution of 3-propionyl-2-thioxothiazolidine (1.07 g) in dichloromethane (9 ml) at -78°C under nitrogen atmosphere. After stirring at -78°C for 30 minutes, a solution of (3R,4R)-4-acetoxy-3-[(1R)-1-(t-butyldimethylsilyloxy)ethyl]-2-azetidinone (0.876 g) and zinc bromide (1.37 g) in dichloromethane (3 ml) was added to the reaction mixture, and the reaction mixture was stirred at -20°C for 15 hours. The reaction mixture was poured into aqueous sodium bicarbonate solution (30 ml) and the precipitated white mass was removed by passing through a layer of Celite. The organic layer was separated and washed with 10% aqueous sodium chloride solution (30 ml x 2). The organic solution was dried over magnesium sulfate and evaporated. The residue was chromatographed on silica gel (21 g) eluting with a mixture of acetone and dichloromethane (2:98, V/V) to give (3S,4R)-3-[(1R)-1-(t-butyldimethylsilyloxy)ethyl]-4-[(1RS)-1-methyl-2-oxo-2-(2-thioxothiazolidin-3-yl)ethyl]-2-azetidinone (878 mg). NMR (CDCl₃, δ) : 0.07 (6H, s), 0.87 (9H, s), 1.17 (3H, d, J=4.5Hz), 1.27 (3H, d, J=4.5Hz), 2.77 (0.2H, dd, J=6.0, 3.0Hz) 3.00 (0.8H, dd, J=4.5, 3.0Hz), 3.26 (2H, t, J=6.5Hz), 3.92 (1H, dd, J=4.5, 3.0Hz), 4.16 (1H, dq, J=6.0, 4.5Hz), 4.53 (2H, t, J=6.5Hz), 4.93 (1H, dq, J=6.5, 4.5Hz), 6.20 (1H, br s) The above NMR data show the ratio of (1R)-1-methyl isomer to (1S)-1-methyl isomer is 4:1. Example 3 To a suspension of stannous trifluoromethanesulfonate (2.18 g) and N-ethylpiperidine (590 mg) in dichloromethane (15 ml) was added dropwise a solution of 2-methyl-2-(trimethylsilyloxy)-3-pentanone (785 mg) in dichloromethane (2 ml) at -78°C under argon atmosphere. After stirring for 30 minutes, a solution of (3R,4R)-4-acetoxy-3-[(1R)-1-(t-butyldimethylsilyloxy)ethyl]-2-azetidinone (300 mg) in dichloromethane (3 ml) was added dropwise to the mixture. The reaction mixture was allowed to warm to room temperature and stirred at the same temperature for 3 hours. The mixture was quenched with phosphate buffer (pH 7). The organic layer was filtered with celite, washed with dichloromethane, dried over magnesium sulfate and evaporated. The residue was chromatographed on silica gel (9 g) eluting with a mixture of ethyl acetate and hexane (1:10, V/V) to give (3S,4R)-3-[(1R)-1-(t-butyldimethylsilyloxy)ethyl]-4-[(1R)-1,3-dimethyl-3-(trimethylsilyloxy)-2-oxobutyl]-2-azetidinone (159 mg). mp : 162°C IR (CDCl₃): 3420, 1755, 1710, 1250 cm⁻¹ NMR (CDCl₃, δ) : 0.00 (6H, s), 0.13 (9H, s), 0.80 (9H, s), 1.10 (3H, d, J=6.0Hz), 1.15 (3H, d, J=6.0Hz), 1.23 (3H, s), 1.28 (3H, s), 2.85 (1H, dd, J=6.0, 3.0Hz), 2.97-3.20 (1H, m), 3.76 (1H, dd, J=6.0, 3.0Hz), 4.13 (1H, dq, J=6.0, 6.0), 5.88 (1H, br s) Example 4 To a solution of (3S,4R)-3-[(1R)-1-(t-butyldimethylsilyloxy)ethyl]-4-[(1RS)-1-methyl-2-oxo-2-(2-thioxothiazolidin-3-yl)ethyl]-2-azetidinone obtained in Example 1 (594 mg) in acetonitrile (18 ml) were added magnesium salt of mono 4-nitrobenzyl ester of malonic acid (636 mg) and imidazole (130 mg), and the mixture was stirred at 60°C for 2 hours under nitrogen atmosphere. The reaction mixture was evaporated and the residue was dissolved in ethyl acetate (10 ml). The solution was washed in turn with 0.5N hydrochloric acid (10 ml x 2), 5% aqueous potassium carbonate (10 ml x 2) and water (10 ml), and dried over magnesium sulfate and evaporated. The residue was chromatographed on silica gel (23 g) eluting with a mixture of hexane and ethyl acetate (3:2, V/V) to give 4-nitrobenzyl (4R)-4-[(2R,3S)-3-{(1R)-1-(t-butyldimethylsilyloxy)ethyl}-4-oxoazetidin-2-yl]-3-oxopentanoate (595 mg) containing a very small amount of (4S)-isomer. IR (CH₂Cl₂ : 1750 cm⁻¹ NMR (CDCl₃, δ) : 0.12 (6H, s), 0.92 (9H, s), 1.21 (3H, d, J=7.0Hz), 1.23 (3H, d, J=7.5Hz), 2.93 (1H, dd, J=5.0, 3.0Hz), 2.6-3.1 (1H, m), 3.65 (2H, s), 3.95 (1H, dd, J=4.5, 3.0Hz), 4.18 (1H, m), 5.27 (2H, s), 5.98 (1H, s), 7.48 (2H, d, J=8.4Hz), 8.21 (2H, d, J=8.4Hz) Example 5 To a solution of (3S,4R)-3-[(1R)-1-(t-butyldimethylsilyloxy)ethyl]-4-[(1RS)-1-methyl-2-oxo-2-(2-thioxothiazolidin-3-yl)ethyl]-2-azetidinone obtained in Example 2 (797 mg) in methanol (16 ml) was added potassium carbonate (410 mg) at 0°C and the mixture was stirred at room temperature for 10 minutes. The reaction mixture was poured into a mixture of ethyl acetate (40 ml), saturated aqueous sodium chloride (25 ml) and 1N hydrochloric acid (3 ml). The organic layer was separated, washed with saturated aqueous sodium chloride solution (30 ml x 2), dried over magnesium sulfate and evaporated. The residue was chromatographed on silica gel (21 g) eluting with a mixture of hexane and ethyl acetate (3:2, V/V) to give methyl (2R)-2-[(2S,3S)-3-{(1R)-1-(t-butyldimethylsilyloxy)ethyl}-4-oxoazetidin-2-yl]propionate (597 mg) containing a very small amount of methyl (2S)-2-[(2S,3S)-3-{(1R)-1-(t-butyldimethylsilyloxy)ethyl}-4-oxoazetidin-2-yl]propionate. IR (CH₂Cl₂) : 1760, 1740 cm⁻¹ NMR (CDCl₃, δ) : 0.07 (6H, s), 0.87 (9H, s), 1.15 (3H, d, J=7.0Hz), 1.24 (3H, d, J=7.0Hz), 2.4-2.9 (1H, m), 2.95 (1H, dd, J=2.5, 4.0Hz), 3.66 (3H, s), 3.83 (1H, dd, J=2.5, 5.0Hz), 4.0-4.4 (1H, m), 6.12 (1H, br s) Example 6 To a solution of (3S,4R)-3-[(1R)-1-(t-butyldimethylsilyloxy)ethyl]-4-[(1R)-1,3-dimethyl-3-(trimethylsilyloxy)-2-oxobutyl]-2-azetidinone (132 mg) in methanol (6 ml) was added oxalic acid dihydrate (200 mg) at room temperature and the mixture was stirred for 1 hour. The reaction mixture was evaporated, and diethyl ether (30 ml) and saturated aqueous sodium bicarbonate (10 ml) were slowly added to the residue. The solution was extracted twice with diethyl ether,and the extracts were combined and washed in turn with saturated aqueous sodium bicarbonate and brine. The organic layer was dried over magnesium sulfate and evaporated to give (3S,4R)-3-[(1R)-1-(t-butyldimethylsilyloxy)ethyl]-4-[(1R)-3-hydroxy-1,3-dimethyl-2-oxobutyl]-2-azetidinone (109 mg). mp : 103°C IR (CDCl₃): 3800-3200, 3430, 1760, 1740 cm⁻¹ NMR (CDCl₃, δ) : 0.08 (6H, s), 0.89 (9H, s), 1.20 (3H, d, J=7.5Hz), 1.26 (3H, d, J=6.0Hz), 2.70 (1H, m), 3.00 (1H, dd, J=2.0, 4.5Hz), 3.92 (1H, dd, J=2.0, 6.0Hz), 4.18 (1H, m), 6.32 (1H, br s) Example 7 To a solution of (3S,4R)-3-[(1R)-1-(t-butyldimethylsilyloxy)ethyl]-4-[(1R)-3-hydroxy-1,3-dimethyl-2-oxobutyl]-2-azetidinone (135 mg) in tetrahydrofuran (4 ml) was added 1M solution of sodium periodate buffered with acetic acid (mole ratio 1:1) (7.8 ml) at room temperature and the mixture was stirred for 1 day at the same temperature. The reaction mixture was evaporated, acidified, and extracted twice with dichloromethane. The organic layer was washed twice with brine, dried over magnesium sulfate and evaporated to give (2R)-2-[(2S,3S)-3-{(1R)-1-(t-butyldimethylsilyloxy)ethyl}-4-oxoazetidin-2-yl]propionic acid (85 mg). mp : 124°C (dec.) IR (CHCl₃): 3480, 3410, 1755, 1700 cm⁻¹ NMR (CDCl₃, δ) : 0.07 (6H, s), 0.87 (9H, s), 1.17 (6H, d, J=6.0Hz), 1.40 (6H, s), 2.90 (1H, dd, J=3.3, 2.4Hz), 3.32 (1H, dq, J=6.6, 7.2Hz), 3.73 (1H, br s), 3.77 (1H, dd, J=7.5, 2.4Hz), 4.08 (1H, dq, J=5.7, 7.5Hz), 6.60 (1H, br s) Example 8 To a solution of (3S,4R)-3-[(1R)-1-(t-butyldimethylsilyloxy)ethyl]-4-[(1R)-1,3-dimethyl-3-(trimethylsilyloxy)- 2-oxobutyl]-2-azetidinone (50 mg) in triethylamine (0.2 ml) and dichloromethane (1 ml) was added dropwise ethyl oxalyl chloride (26 µl) at 0°C. After stirring for 1 hour at room temperature, the reaction mixture was extracted with dichloromethane. The organic layer was washed with water, dried over magnesium sulfate and evaporated to give (3S,4R)-3-[(1R)-1-(t-butyldimethylsilyloxy)ethyl]-1-(ethoxalyl)-4-[(1R)-1,3-dimethyl-3-(trimethylsilyloxy)-2-oxobutyl]-2-azetidinone. To a solution of this product in methanol (2 ml) was added oxalic acid dihydrate (73 mg) at room temperature and the mixture was stirred for 1 hour. The reaction mixture was evaporated and extracted with ethyl acetate. The extract was washed in turn with brine and water, dried over magnesium sulfate and evaporated. The residue was chromatographed on silica gel (1 g) eluting with a mixture of ethyl acetate and hexane (1:2 - 1:3, V/V) to give (3S,4R)-3-[(1R)-1-(t-butyldimethylsilyloxy)ethyl]-1-(ethoxalyl)-4-[(1R)-3-hydroxy-1,3-dimethyl-2-oxobutyl]-2-azetidinone (76 mg). Example 9 To a solution of (3S,4R)-3-[(1R)-1-(t-butyldimethylsilyloxy)ethyl]-1-(ethoxalyl)-4-[(1R)-3-hydroxy-1,3-dimethyl-2-oxobutyl]-2-azetidinone (50 mg) in methanol (2 ml) was added 0.54M aqueous periodic acid solution (1.0 ml). After stirring at room temperature for 5 hours, the solvent was removed in vacuo and the residue was extracted with dichloromethane. The extract was dried over magnesium sulfate and evaporated to afford (2R)-2-[(2S,3S)-3-{(1R)-1-(t-butyldimethylsilyloxy)ethyl}-1-(ethoxalyl)-4-oxoazetidin-2-yl]propionic acid (93 mg). To a solution of the compound obtained above in diethyl ether (2 ml) was added a solution of diazomethane in diethyl ether at room temperature. The solvent was removed in vacuo and the residue was chromatographed on silica gel (1 g) eluting with a mixture of ethyl acetate and hexane (1:5, V/V) to give methyl (2R)-2-[(2S,3S)-3-{(1R)-1-(t-butyldimethylsilyloxy)ethyl}-1-(ethoxalyl)-4-oxoazetidin-2-yl]propionate (24 mg). IR (CDCl₃): 1810, 1750, 1730, 1700 cm⁻¹ NMR (CDCl₃, δ) : -0.02 (3H, s), 0.02 (3H, s). 0.80 (9H, s), 1.16 (3H, d, J=6.0Hz), 1.20 (3H, d, J=6.0Hz), 1.30 (3H, t, J=7.5Hz), 3.10-3.50 (2H, m), 3.67 (3H, s). 4.00-4.50 (2H, m), 4.33 (2H, q, J=7.5Hz) Example 10 To a solution of methyl (2R)-2-[(2S,3S)-3-{(1R)-1-(t-butyldimethylsilyloxy)ethyl}-1-(ethoxalyl)-4-oxoazetidin-2-yl]propionate (27 mg) in methanol (1 ml) was added triethylamine (27 µl) at room temperature. After stirring for 30 minutes, the reaction mixture was extracted with ethyl acetate. The organic layer was washed with brine (twice) and water, dried over magnesium sulfate and evaporated to give methyl (2R)-2-[(2S,3S)-3-{(1R)-1-(t-butyldimethylsilyloxy)ethyl}-4-oxoazetidin-2-yl]propionate (14 mg). IR (CH₂Cl₂) : 1760, 1740 cm⁻¹ Example 11 To a suspension of stannous trifluoromethanesulfonate (1.48 g) and N-ethylpiperidine (404 mg) in dichloromethane (15 ml) was added dropwise a solution of 2-methyl-2-trimethylsilyloxy-3-pentanone (819 mg) in dichloromethane (5 ml) at -60° ∼ -70°C under an argon atmosphere. After the mixture was stirred for 1 hour, a solution of (3R,4R)-4-acetoxy-3-[(1R)-1-t-butyldimethylsilyloxyethyl]-2-azetidinone (500 mg) in dichloromethane (5 ml) was added dropwise to the mixture. The reaction mixture was allowed to warm to room temperature and stirred at the same temperature for 2 hours. The mixture was quenched with phosphate buffer (pH 7) and filtered with celite. The filtrate was washed twice with water, dried over magnesium sulfate and evaporated. The residue was chromatographed on silica gel eluting with a mixture of ethyl acetate and hexane (1:4 - 1:5, V/V) to give (3S,4R)-3-[(1R)-1-t-butyldimethylsilyloxyethyl]-4-[(1R)-1,3-dimethyl-3-trimethylsilyloxy-2-oxobutyl]-2-azetidinone (650 mg). mp: 162°C IR (CHCl₃): 3420, 1755, 1710, 1250 cm⁻¹ NMR (CDCl₃, δ) : 0.00 (6H, s), 0.13 (9H, s), 0.80 (9H, s), 1.10 (3H, d, J=6.0Hz), 1.15 (3H, d, J=6.0Hz), 1.23 (3H, s), 1.28 (3H, s), 2.85 (1H, dd, J=6.0 and 3.0Hz), 2.97 - 3.20 (1H, m), 3.76 (1H, dd, J=6.0 and 3.0Hz), 4.13 (1H, dq, J=6.0 and 6.0Hz), 5.88 (1H, br s) [α] 17 / D - 3.8°(c 1.0, CHCl₃)

Claims: Claims for the following Contracting States : AT, BE, CH, DE, FR, GB, GR, IT, LI, LU, NL, SE 3,4-Disubstituted-2-azetidinone derivatives of the formula: in which R¹ is hydrogen or imino-protective group, R² is hydroxy(C₁-C₆)alkyl or protected hydroxy(C₁-C₆)alkyl R³ is C₁-C₆ alkyl, and R⁴ is 1-(C₁-C₆)alkyl-1-hydroxy(C₂-C₆)alkyl, 1-(C₁-C₆)alkyl-1-(protected hydroxy)(C₂-C₆)alkyl or 2-thioxothiazolidin-3-yl, and salts thereof. The compound of Claim 1, which is represented by the following configuration: wherein R¹, R², R³ and R⁴ leave the meaning as given in claim 1. A compound of Claim 1, which is represented by the following configuration: in which R¹ is hydrogen, ar(C₁-C₆)alkyl or acyl, R² is hydoxy(C₁-C₆)alkyl, acyloxy(C₁-C₆)alkyl ar(C₁-C₆)alkoxy(C₁-C₆)alkyl or trisubstituted silyloxy(C₁-C₆)alkyl, and R⁴ is 1-(C₁-C₆)alkyl-1-hydroxy(C₂-C₆)alkyl, 1-(C₁-C₆)alkyl-1-acyloxy(C₂-C₆)alkyl, 1-(C₁-C₆)alkyl-1-[ar(C₁-C₆)alkoxy](C₂-C₆)alkyl, 1-(C₁-C₆)alkyl-1-(trisubstitutedsilyloxy)(C₂-C₆)alkyl or 2-thioxothiazolidin-3-yl. A compound of Claim 3, wherein R¹ is hydrogen, ar(C₁-C₆)alkyl, phenyl- or nitrophenyl(C₁-C₆)alkoxyoxalyl, or (C₁-C₆)alkoxyoxalyl, R² is hydroxy(C₁-C₆)alkyl, tri(C₁-C₆)alkylsilyloxy(C₁-C₆)alkyl, or phenyl- or nitrophenyl(C₁-C₆)alkoxycarbonyloxy(C₁-C₆)alkyl, and R⁴ is 1-(C₁-C₆)alkyl-1-hydroxy(C₂-C₆)alkyl, 1-(C₁-C₆)alkyl-1-[tri(C₁-C₆)alkylsilyloxy](C₂-C₆)alkyl or 1-(C₁-C₆)alkyl-1-[phenyl- or nitrophenyl(C₁-C₆)alkoxycarbonyloxy](C₂-C₆)alkyl. A compound of Claim 4, wherein R¹ is hydrogen or (C₁-C₄)alkoxyoxalyl, R² is hydroxy(C₁-C₄)alkyl or tri(C₁-C₄)alkylsilyloxy(C₁-C₄)alkyl, and R⁴ is 1-(C₁-C₄)alkyl-1-hydroxy(C₂-C₄)alkyl or 1-(C₁-C₄)alkyl-1-[tri(C₁-C₄)alkylsilyloxy](C₂-C₄)alkyl. A compound of Claim 3, wherein R¹ is hydrogen, ar(C₁-C₆)alkyl, phenyl- or nitrophenyl(C₁-C₆)alkoxyoxalyl, or (C₁-C₆)alkoxyoxalyl, R² is hydroxy(C₁-C₆)alkyl, tri(C₁-C₆)alkylsilyloxy(C₁-C₆)alkyl, or phenyl- or nitrophenyl(C₁-C₆)alkoxycarbonyloxy(C₁-C₆)alkyl, and R⁴ is 2-thioxothiazolidin-3-yl. A compound of Claim 6, wherein R¹ is hydrogen or (C₁-C₄)alkoxyoxalyl, and R² is hydroxy(C₁-C₄)alkyl or tri(C₁-C₄)alkylsilyloxy(C₁-C₄)alkyl. A compound of Claim 7, which is (3S,4R)-3-[(1R)-1-t-butyldimethylsilyloxyethyl]-4-[(1R)-1-methyl-2-oxo-2-(2-thioxothiazolidin-3-yl)ethyl]-2-azetidinone. The compound of Claim 1, wherein R¹ is hydrogen, ar(C₁-C₆)alkyl or acyl. The compound of Claim 9, wherein R¹ is hydrogen, ar(C₁-C₆)alkyl, phenyl- or nitrophenyl(C₁-C₆)alkoxyoxalyl, or (C₁-C₆)alkoxyoxalyl. The compound of Claim 10, wherein R¹ is hydrogen or (C₁-C₄)alkoxyoxalyl. The compound of Claim 11, wherein R¹ is hydrogen. The compound of Claim 1, wherein R² is hydroxy(C₁-C₆)alkyl, acyloxy(C₁-C₆)alkyl, ar(C₁-C₆)alkoxy(C₁-C₆)alkyl or trisubstituted silyloxy(C₁-C₆)alkyl. The compound of Claim 13, wherein R² is hydroxy(C₁-C₆)alkyl, tri(C₁-C₆)alkylsilyloxy(C₁-C₆)alkyl, or phenyl- or nitrophenyl(C₁-C₆)alkoxycarbonyloxy(C₁-C₆)alkyl. The compound of Claim 14, wherein R² is hydroxy(C₁-C₄)alkyl or tri(C₁-C₄)alkylsilyloxy(C₁-C₄)alkyl. The compound of Claim 15, wherein R² is hydroxy(C₁-C₄)alkyl. The compound of Claim 1, wherein R⁴ is 1-(C₁-C₆)alkyl-1-hydroxy(C₂-C₆)alkyl, 1-(C₁-C₆)alkyl-1-acyloxy(C₂-C₆)alkyl, 1-(C₁-C₆)alkyl-1-[ar(C₁-C₆)alkoxy](C₂-C₆)alkyl, 1-(C₁-C₆)alkyl-1-(trisubstituted silyloxy)(C₂-C₆)alkyl or 2-thioxothiazolidin-3-yl. The compound of Claim 17, wherein R⁴ is 1-(C₁-C₆)alkyl-1-hydroxy(C₂-C₆)alkyl, 1-(C₁-C₆)alkyl-1-[tri(C₁-C₆)alkylsilyloxy](C₂-C₆)alkyl or 1-(C₁-C₆)alkyl-1-[phenyl- or nitrophenyl(C₁-C₆)alkoxycarbonyloxy](C₂-C₆)alkyl. The compound of Claim 18, wherein R⁴ is 1-(C₁-C₄)alkyl-1-hydroxy(C₂-C₄)alkyl or 1-(C₁-C₄)alkyl-1-[tri(C₁-C₄)alkylsilyloxy](C₂-C₄)alkyl. The compound of Claim 19, wherein R⁴ is 1-(C₁-C₄)alkyl-1-hydroxy(C₂-C₄)alkyl. The compound of Claim 17, wherein R⁴ is 2-thioxothiazolidin-3-yl. The compound of Claim 1, which is a mixture of (3S,4R)-3-[(1R)-1-t-butyldimethylsilyloxyethyl]-4-[(1R)-1-methyl-2-oxo-2-(2-thioxothiazolidin-3-yl)ethyl]-2-azetidinone and (3S,4R)-3-[(1R)-1-t-butyldimethylsilyloxyethyl]-4-[(1S)-1-methyl-2-oxo-2-(2-thioxothiazolidin-3-yl)ethyl]-2-azetidinone. The compound of Claim 1, which is (3S,4R)-3-[(1R)-1-t-butyldimethylsilyloxyethyl]-4-[(1R)-1-methyl-2-oxo-2-(2-thioxothiazolidin-3-yl) ethyl]-2-azetidinone containing a small amount of (3S,4R)-3-[(1R)-1-t-butyldimethylsilyloxyethyl]-4-[(1S)-1-methyl-2-oxo-2-(2-thioxothiazolidin-3-yl)ethyl]-2-azetidinone. A process for the preparation of 3,4-disubstituted-2-azetidinone derivatives of the formula: in which R¹ is hydrogen or imino-protective group, R² is hydroxy(C₁-C₆)alkyl or protected hydroxy(C₁-C₆)alkyl R³ is C₁-C₆-alkyl, and R⁴ is 1-(C₁-C₆)alkyl-1-hydroxy(C₂-C₆)alkyl, 1-(C₁-C₆)alkyl-1-(protected hydroxy)(C₂-C₆)alkyl or 2-thioxothiazolidin-3-yl, and salts thereof, which comprises (1) reacting a compound of the formula: in which R¹ and R² are each as defined above, and R⁵ is acyl, or salts thereof, with a compound of the formula: R³-CH₂CO-R⁴ in which R³ and R⁴ are each as defined above, or salts thereof, in the presence of an enolizating agent to give a compound of the formula: in which R¹, R², R³ and R⁴ are each as defined above, or salts thereof; and (2) subjecting a compound of the formula: in which R¹, R² and R³ are each as defined above, and R 4 / a is 1-(C₁-C₆)alkyl-1-(protected hydroxy)(C₂-C₆)alkyl, or salts thereof, to removal reaction of the hydroxy-protective group in R 4 / a to give a compound of the formula: in which R¹, R² and R³ are each as defined above, and R 4 / b is 1-(C₁-C₆)alkyl-1-hydroxy(C₂-C₆)alkyl, or salts thereof; and (3) introducing an imino-protective group into a compound of the formula: in which R², R³ and R⁴ are each as defined above, or salts thereof to give a compound of the formula: in which R², R³ and R⁴ are each as defined above, and R 1 / a is imino-protective group. A process for the preparation of a compound of the formula: in which R¹ is hydrogen or imino-protective group, R² is hydroxy(C₁-C₆)alkyl or protected hydroxy(C₁-C₆)alkyl, R³ is C₁-C₆-alkyl, and R⁷ is protected carboxy, and salts thereof, which comprises reacting a compound of the formula: in which R¹ and R² are each as defined above, and R⁵ is acyl, or salts thereof, with a compound of the formula: in which R³ is as defined above, and R 4 / c is 2-thioxothiazolidin-3-yl, or salts thereof, in the presence of an enolizating agent, and reacting the resultant compound of the formula: in which R¹, R², R³ and R 4 / c are each as defined above, or salts thereof, with a compound of the formula: Mg(OCOCH₂R⁷)₂ in which R⁷ is as defined above. Claims for the following Contracting State : ES A process for the preparation of 3,4-disubstituted-2-azetidinone derivatives of the formula: in which R¹ is hydrogen or imino-protective group, R² is hydroxy(C₁-C₆)alkyl or protected hydroxy(C₁-C₆)alkyl R³ is C₁-C₆-alkyl, and R⁴ is 1-(C₁-C₆)alkyl-1-hydroxy(C₂-C₆)alkyl, 1-(C₁-C₆)alkyl-1-(protected hydroxy)(C₂-C₆)alkyl or 2-thioxothiazolidin-3-yl, and salts thereof, which comprises (1) reacting a compound of the formula: in which R¹ and R² are each as defined above, and R⁵ is acyl, or salts thereof, with a compound of the formula: R³-CH₂CO-R⁴ in which R³ and R⁴ are each as defined above, or salts thereof, in the presence of an enolizating agent to give a compound of the formula: in which R¹, R², R³ and R⁴ are each as defined above, or salts thereof; and (2) subjecting a compound of the formula: in which R¹, R² and R³ are each as defined above, and R 4 / a is 1-(C₁-C₆)alkyl-1-(protected hydroxy)(C₂-C₆)alkyl, or salts thereof, to removal reaction of the hydroxy-protective group in R 4 / a to give a compound of the formula: in which R¹, R² and R³ are each as defined above, and R 4 / b is 1-(C₁-C₆)alkyl-1-hydroxy(C₂-C₆)alkyl, or salts thereof; and (3) introducing an imino-protective group into a compound of the formula: in which R², R³ and R⁴ are each as defined above, or salts thereof to give a compound of the formula: in which R², R³ and R⁴ are each as defined above, and R 1 / a is imino-protective group. A process for the preparation of a compound of the formula: in which R¹ is hydrogen or imino-protective group, R² is hydroxy(C₁-C₆)alkyl or protected hydroxy(C₁-C₆)alkyl, R³ is C₁-C₆-alkyl, and R⁷ is protected carboxy, and salts thereof, which comprises reacting a compound of the formula: in which R¹ and R² are each as defined above, and R⁵ is acyl, or salts thereof, with a compound of the formula: in which R³ is as defined above, and R 4 / c is 2-thioxothiazolidin-3-yl, or salts thereof, in the presence of an enolizating agent, and reacting the resultant compound of the formula: in which R¹, R², R³ and R 4 / c are each as defined above, or salts thereof, with a compound of the formula: Mg(OCOCH₂R⁷)₂ in which R⁷ is as defined above.

Inventors: CHIBA, TOSHIYUKI, NAKAI, TAKESHI, OHTAKE, HIROAKI, SHIRAI, FUMIYUKI
Applicants: FUJISAWA PHARMACEUTICAL CO., LTD.
Application year: 1987
Main classification: C07F7
IPC codes: C07D205, C07F7, C07D417