ANTIBACTERIAL PENEM ESTERS DERIVATIVES

Abstract: Antibiotic penem compounds are represented by formula (I), wherein R represents a group of general formulae (II), (III), or -CH2-Z, in which R1 is a linear or branched C1-C6 alkyl group, R2 is a particular substituted or unsubstituted alkyl, aryl or aralkyl group, n is an integer of 1-6, Y is a 5- or 6-membered heterocyclic aliphatic group having 1 or 2 oxygen atoms in the ring thereof, and Z is a specific 5-substituted 2-oxo-1,3-dioxolen-4-yl group. Antibiotic compositions for oral administration are also described.

Description: DESCRIPTION ANTIBACTERIAL PENEM ESTERS DERIVATIVES Technical Field The present invention relates to penem compounds, and more specifically to penem compounds which are ex¬ pected to find clinical utility as promising antibiotics. Background Art The present inventors previously found that a group of penem compounds represented by the following formula (V) : ( V ) wherein 3 is a hydrogen atom or allyl group, -A- represents an oxygen or methylene group, and -B- represents a methylene, ethylene or carbonyl group, and their salts have excellent antibacterial activities on both gram-positive and gram-negative, aerobic or anaerobic bacteria and have already filed patent ap- plication thereon (Japanese Patent Laid-Open No. 207387/1986) . High safety of these compounds has been confirmed by a safety test in which laboratory animals were used. Their development as medical drugs is now expected. In the meantime, it has been found by the study on the correlation between structure and antibacterial activities of these compounds [J. Antibiotics, 41, 1685 (1988)] that, among 2-substituents of penem, (R)-2- tetrahydrofuryl group provides the highest antibac¬ terial activities while (S) -2-tetrahydrofuryl group, a diastereomer at its 2-side chain group, and (R) or (s)- 3-tetrahydrofuryl group, a position isomer, provide weaker activities particularly against gram-negative bacteria. From these reasons, compounds represented by the following formula (VI) : ( VI ) wherein R 4 represents a hydrogen atom or a group capable of forming a pharmaceutically-acceptable salt, have drawn interests as antibiotics. These compounds are also interested in that they do not require any special chemical modification for oral absorption and they themselves can be developed as both injections and oral drugs. Namely, the bioavailability of the above- described compounds per se in laboratory animal (rats) has been found by no means inferior to commercial drugs which are used clinically. However, from the viewpoint of safety and econo- my, further enhancement of their bioavailability upon oral administration is apparently more advantageous. As far as the above compounds are concerned, there is yet room for further improvement in this regard. Regarding improvements on the absorption upon oral administration, active studies have been conducted on penicillin and cephalosporin antibiotics so that many of these antibiotics are used as curative medi¬ cines. There are, however, only a few study reports of this type on penem and carbapenem antibiotics [J. Anti- biotics, 36, 983, (1983); Japanese Patent Laid-Open No. 6728/1990]. It has therefore been interested in determining whether or not the approaches used for penicillin and cephalosporin antibiotics are equally applicable to penem compounds. Disclosure of Invention The present inventors have carried out an ex¬ tensive investigation on the compounds (VI) with a view toward making an improvement in their bioavailability. As a result, it has been found that protection of their carboxyl group with a particular ester-forming group can significantly improve their bioavailability, lead¬ ing to the completion of the present invention. Namely, the present invention provides a penem compound represented by the following formula (I) : ( 1 ) wherein R represents a group of the general formula (II), (III) or (IV): -CHOCO(CH 2 ) n COOR 2 (ID R l in which R- j _ is a linear or branched Cτ_-Cg alkyl group; R 2 is a C- j _-C 6 alkyl group, a Cg-C 10 aryl group or C 7 - ll a-»-" a lkyl group, each group being optionally sub¬ stituted by one or more C-^-C 8 alkyl groups, C 8 -C 10 aryl groups, C7-C11 aralkyl groups, hydroxyl groups, C- j _-Cg alkoxyl groups and/or halogen atoms, and n is an in¬ teger of 1-6, -CHOCO-Y I (III) R l in which R-^ has the same meaning as defined above; Y is a 5- or 6-membered heterocyclic aliphatic group having 1 or 2 oxygen atoms in the ring thereof, or -CH 2 -Z (IV) in which Z is a 5-substituted 2-oxo-l, 3-dioxolen-4-yl group, said 5-substituent being a -^-Cg alkyl group, a c 6 _c 10 ar yl gro p or a Cj-C±i aralkyl group, said 5- substituent being optionally substituted by one or more c l _c 6 al ^Yl groups, C -C 10 aryl groups, C-^-C-^^ aralkyl groups, hydroxyl groups, C-^-C alkoxyl groups and/or halogen atoms. Best Mode for Carrying Out the Invention The penem compound (I) of the present invention can be synthesized, for example, by reacting a halogenated alkyl compound (VII) to a penem compound (VI 1 ) in accordance with the following formula: ( I ) wherein X represents a halogen atom, R 4 represents a hydrogen or alkali metal atom or an amino residuum, and R has the same meaning as defined above. When R 4 in the compound (IV) is an alkali metal atom or an amino residuum in this invention, the target compound can be obtained by stirring the compound (VI ' ) and the halogenated alkyl compound (VII) in an organic solvent. When R 4 in the compound (VI 1 ) is a hydrogen atom, on the other hand, it is firstly reacted with an alkali metal hydroxide, an alkali metal salt or an a ine com¬ pound in an organic solvent to form a salt. The halogenated alkyl compound (VII) is then reacted to the reaction mixture, whereby the target compound is synthesized. The halogenated alkyl compound represented by the formula (VII) serves to efficiently esterify the car- boxyl group of the compound (VI') with the group R so that the target compound of the formula (I) is prepared. Examples of the compound (VII) include those containing, as the group R, a tetrahydrofuryl- carbonyloxymethyl group, tetrahydropyranylcarbonyloxy- methyl group, 1,3-dioxolanylcarbonyloxymethyl group, 2- oxo-1,3-dioxolanylcarbonyloxymethyl group, 1,4- dioxanylcarbonyloxymethyl group or the like or its op¬ tically active isomer such as an (R)-2-tetrahydrofuryl- carbonyloxymethyl group, (S)-2-tetrahydrofuryl- carbonyloxymethyl group or (5-methyl-2-oxo-l,3- dioxolen-4-yl)methyl group and, as a halogen X, a chlorine, bromine or iodine atom. No particular limitation is imposed on the alkali metal insofar as it forms a salt with the compound (VI 1 ). Examples of the alkali metal include lithium, sodium and potassium. Examples of their hydroxides and salts include sodium hydroxide, potassium hydroxide, sodium bicarbonate, sodium carboxylate, potassium bicarbonate and potassium carbonate. Exemplary a ine compounds include ammonia, triethylamine, and diisopropyl ethyl amine. No particular limitation is imposed on the reac- tion solvent. Examples of the reaction solvent include aromatic hydrocarbons such as toluene and xylene, aliphatic hydrocarbons such as pentane and hexane, halogenated alkyls such as methylene chloride and chloroform, halogenated aryls such as chlorobenzenes, ketones such as acetone and methyl ethyl ketone, nitriles such as acetonitrile and propionitrile, amides such as dimethylformamide, sulfoxides such as dimethyl sulfoxide, ethers such as diethyl ether and tetra- hydrofuran, and alcohols such as isopropanol and t- butanol. They can be used either singly or in combina¬ tion. The reaction may be carried out at room tempera¬ ture or, when desired, under heating at a temperature below 80°C. The reaction time is generally 1-48 hours although it varies depending on the halogenated alkyl compound to be used. As an alternative process for the preparation of the compound of this invention, the compound can also be synthesized by converting the compound of the for¬ mula (VI) into its chloromethyl or iodomethyl ester in accordance with the process proposed by B. Balzer et al. [J. Antibiotics, 33, 1183 (1980)] and then reacting it with a carboxylate salt represented by the following formula (VIII) : R 5 -COOM (VIII) wherein R5 has the same meaning as Y and M is an alkali metal or an amino residuum. This reaction is carried out at a temperature in the range of from -40°C to room temperature, and is normally completed in 1-48 hours. The penem compound (I) obtained as described above may be used as is but, in general, is purified, as needed, by a method such as column chromatography or recrystallization for use as a medicine. For oral, parenteral or external administration, the compounds according to the present invention can be formulated as antibiotics in a manner known per se in the art. Although the dosage of each penem derivative of the present invention varies depending on many factors, the typical daily dosage ranges from 50 mg to 3 g for standard adults with the administration of 100 mg to 2 g in divided portions being preferred. In general, the above dosage will be administered in the form of a dosage unit which contains an appropriate amount of the active ingredient and a suitable, physiologically- acceptable carrier or extender. For oral administration, tablets or capsules can be used. They may contain - together with the active ingredient - an extender, e.g., lactose, glucose, sucrose, mannitol, sorbitol or cellulose, and a lubricant, e.g. , talc, stearic acid or a stearate salt. Tablets may additionally contain a binder, for example, hydroxypropyl cellulose or starch. The compounds according to the present invention can be used not only for men but also for animals. The present invention will hereinafter be de¬ scribed more specifically by the following examples. It is however borne in mind that the present invention is not limited at all by these examples. Example 1 Chloromethyl (5R,6S)-6-[ (R)-1-hydroxyethyl]- 2-[ (B) -2-tetrahydrofuryl]penem-3-carboxylate (Compound 6) : To the mixture of sodium (5R, 6S) -6-[ (R) -1- hydroxyethyl]-2-[ (R) -2-tetrahydrofuryl]penera-3- carboxylate 2.5 hydrate (Compound 1, 24.7 g) , tetrabutylammonium sulfate (2.38 g) and potassium bicarbonate (21.0 g) , water (70 ml) and methylene chloride (70 ml) were added. Into the resultant mix¬ ture, a solution of chloromethyl chlorosulfate (11.5 g) diluted in methylene chloride (280 ml) was added drop- wise over about 10 minutes under ice cooling and stir- ring. After the reaction mixture was stirred for addi- tional 2.5 hours at room temperature, the organic layer was collected and washed with water. The organic layer was dried and then concentrated. The residue so ob¬ tained was purified by passing it through a silica gel column. The title compound was obtained in the amount of 9.92 g. Example 2 Iodomethyl (5R,6S)-6-[ (R)-1-hydroxyethyl]- 2-[ (R)-2-tetrahydrofuryl]penem-3-carboxylate (Compound 7) : The mixture of chloromethyl (5R,6S)-6-[ (R)-1- hydroxyethyl]-2-[ (R)-2-tetrahydrofuryl]penem-3- carboxylate (Compound 6, 334 mg) , sodium iodide (225 mg) and acetone (2 ml) was stirred over night at room temperature, and the reaction mixture was concentrated. Ethyl acetate was added to the residue. The resultant solution was washed with water, dried, and then con¬ centrated, whereby 359 mg of the title compound were obtained. Example 3 [5-(allyloxy)glutaryl]oxymethyl (5R,6S)-6-[ (R)-1- hydroxyethyl]-2-[ (R)-2-tetrahydrofuryl]penem-3- carboxylate (Compound 2) : The mixture of iodomethyl (5R,6S)-6-[ (R)-1- hydroxyethyl]-2-[ (R)-2-tetrahydrofuryl]penem-3- carboxylate (Compound 6, 3.4 g) , sodium monoallyl- glutarate (3.83 g) and N,N-dimethylformamide (20 ml) was allowed to stand overnight at -20°C. The reaction mixture was then diluted with ethyl ether and washed with water. The organic layer was dried and then con¬ centrated. The residue was purified by passing it through a silica gel column, whereby 0.553 g of the title compound was obtained. Example 4 ' (R)-2-tetrahydrofurylcarbonyloxymethyl (5R,6S)-6- [ (R) -1-hydroxyethyl]-2-[ (R) -2-tetrahydrofuryl]- penem-3-carboxylate (Compound 3) : The mixture of iodomethyl (5R, 6S) -6-[ (R) -1- hydroxyethyl]-2-[ (R)-2-tetrahydrofuryl]penem-3- carboxylate (Compound 6, 3.4 g) , (R) -tetrahydro-2- furoic acid sodium salt (1.38 g) and N,N-dimethyl- formamide (20 ml) was stirred for 2 hours at room temperature. The reaction mixture was diluted with ethyl ether and then washed with water. The organic layer was dried and concentrated. The residue was purified by passing it through a silica gel column, whereby 0.72 g of the title compound was obtained. Example 5 (S)-2-Tetrahydrofurylcarbonyloxymethyl (5R,6S)-6- [ (R)-1-hydroxyethyl]-2-[ (R)-2-tetrahydrofuryl]- penem-3-carboxylate (Compound 4) : The mixture of iodomethyl (5R,6S)-6-[ (R)-1- hydroxyethyl]-2-[ (R)-2-tetrahydrofuryl]penem-3- carboxylate (Compound 6, 3.4 g) , (S)-tetrahydro-2- furoic acid sodium salt (1.38 g) and N,N-dimethyl- ormamide (20 ml) was stirred for 2 hours at room temperature. The reaction mixture was diluted with ethyl ether, followed by washing with water. The organic layer was dried and then concentrated. The residue was purified by passing it through a silica gel column, whereby 0.92 g of the title compound was ob- tained. Example 6 (5-Methyl-2-oxo-l,3-dioxolen-4-yl) ethyl (5R, 6Sj - 6-[ (R)-1-hydroxyethyl]-2-[ (R)-2- tetrahydrofuryl]penem-3-carboxylate (Compound 5) : The mixture of sodium (5R,6S)-6-[ (R)-1-hydroxy¬ ethyl]-2-[ (R)-2-tetrahydrofuryl]penem-3-carboxylate 2.5 hydrate (Compound 6, 3.4 g) , 4-iodomethyl-5-methyl-2- oxo-l,3-dioxolane (1.38 g) and N,N-dimethylformamide (20 ml) was stirred for 5 hours at room temperature. Water was added to the reaction mixture, and the resultant mixture was extracted with ethyl acetate. The ethyl acetate layer was washed with water, dried and then concentrated. The residue was purified by passing it through a silica gel column whereby 1.75 g of the title compound were obtained. Physical properties of the compounds synthesized in Examples 2-7 are summarized in Table 1. Table 1 (1) Table 1 (2) Example 7 The bioavailability of certain compounds (I) of the present invention was tested relying upon their recovery rates in urine. Each test compound (30 μmole/ g) was orally ad¬ ministered to SD strain rats (three male rats per group) . Urine was collected over 6 hours from the ad¬ ministration, and the recovery rate of the correspond¬ ing compound present in the urine was determined by bioassay. The results are shown below. Table 2 As is apparent from the results, the compounds (I) of the present invention showed the higher urinaly recovery rate, in other words, a higher bioavailability compared with the penem compound (VI) . Preparation Examples In each of the following preparation examples, the active ingredient may be, for example, Compound 5 or an equivalent amount of any one of the other com¬ pounds of the present invention. Preparation 1 Capsules Ingredient No. Ingredient 1 Invention compound 2 Lactose 3 Magnesium stearate (Total) (Production procedures) Ingredients 1 and 2 were combined together in a suitable mixer, to which Ingredient 3 was added, followed by further mixing. The resultant mixture was filled by a capsule filling machine. Preparation 2 Tablets Ingredient No. Ingredient mg/tablet 1 Invention compound 150 2 Crystalline cellulose 50 3 Calcium carboxymethylcellulose 10 4 Magnesium stearate 4 (Total) 214 mg (Production procedures) Ingredients 1-3 were combined together in a suitable mixer, to which Ingredient 4 was added, followed by mixing for additional several minutes. The resultant mixture was compressed into a predetermined size and weight by a tablet machine. Industrial Applicability As has been described above, the compounds of the present invention exhibit an excellent bioavailability so that they can be advantageously used as oral anti¬ biotics.

Claims: CLAIMS 1. A penem compound represented by the following formula (I) : ( I ) wherein R represents a group of the general formula (II) , (III) or (IV) : -CHOCO(CH 2 ) n COOR 2 (II) in which R-^ is a linear or branched C- ] _-C 6 alkyl group; R 2 is a C 1 -C 6 alkyl group, a C 6 -C 10 aryl group or Cη- C-^ aralkyl group, each group being optionally sub¬ stituted by one or more C-^-Cg alkyl groups, C 6 -C 10 aryl groups, C 7 -C 1L aralkyl groups, hydroxyl groups, C- j _-Cg alkoxyl groups and/or halogen atoms, and n is an in¬ teger of 1-6, -CHOCO-Y I (III) R l in which R- j _ has the same meaning as defined above; Y is a 5- or 6-membered heterocyclic aliphatic group having 1 or 2 oxygen atoms in the ring thereof, or -CH 2 -Z (IV) in which Z is a 5-substituted 2-oxo-l,3-dioxolen-4-yl group, said 5-substituent being a C- j^ -Cg alkyl group, a 6~ c 1 0 ar yl roup or a Cy-C-^ aralkyl group, said 5- substituent being optionally substituted by one or more c l*~ c 6 alk yi groups, C 6 -C 10 aryl groups, C7-C ι:L aralkyl groups, hydroxyl groups, C-^-C alkoxyl groups and/or halogen atoms. 2. A compound according to claim 1, wherein Y represents a tetrahydrofuryl group. 3. A compound according to claim 1, wherein Y represents a tetrahydropyranyl group. 4. A compound according to claim 1, wherein Y represents * a 1,3-dioxolanyl group. 5 5. A compound according to claim 1, wherein Y represents a 2-oxo-l,3-dioxolanyl group. 6. A compound according to claim 1, wherein Y represents a 1,4-dioxanyl group. 7. A compound according to claim 1, wherein Y o represents an (R) -2-tetrahydrofuryl group. 8. A compound according to claim 1, wherein Y represents a (S) -2-tetrahydrofuryl group. 9. A compound according to claim 1, wherein R represents a (5-methyl-2-oxo-l,3-doioxolen-4-yl)methyl 5 group. 10. A compound according to any one of claims 1, 2, 3, 5, 6, 7, 8, and 9 wherein R is an optically ac¬ tive group. 11. An antibiotic composition for oral adminis- tration, comprising an effective amount of a compound of the following formula (I) : ( I ) wherein R represents a group of the general formula (II), (III) or (IV): -CHOCO(CH 2 ) n COOR 2 I (II) in which R-^ is a linear or branched C- j^ -C alkyl group; R 2 is a C-^-Cg alkyl group, a C 6 -C 10 aryl group or C 7 - aralkyl group, each group being optionally sub¬ stituted by one or more C-^-C 8 alkyl groups, C 6 -C 10 aryl groups, C 7 -C 1;L aralkyl groups, hydroxyl groups, C^-Cg alkoxyl groups and/or halogen atoms, and n is an in¬ teger of 1-6, -CHOCO-Y I (HI) R l in which R^ has the same meaning as defined above; Y is a 5- or 6-membered heterocyclic aliphatic group having 1 or 2 oxygen atoms in the ring thereof, or -CH 2 -Z (IV) in which Z is a 5-substituted 2-oxo-l,3-dioxolen-4-yl group, said 5-substituent being a C^ ^ -C alkyl group, a C 6 -C 10 aryl group or a Cη- -^-^ aralkyl group, said 5- substituent being optionally substituted by one or more c l ~ c 6 slky 1 groups, C 6 -C 10 aryl groups, C 7 -C 1;L aralkyl groups, hydroxyl groups, ^-C 8 alkoxyl groups and/or halogen atoms, and a pharmaceutically-acceptable car¬ rier.

Inventors: ISHIGURO MASAJI, IWATA HIROMITSU, NAKATSUKA TAKASHI, TANAKA RIE, ISHIGURO, MASAJI, IWATA, HIROMITSU, NAKATSUKA, TAKASHI, TANAKA, RIE
Applicants: SUNTORY LTD, SUNTORY LIMITED
Application year: 1991
Main classification: A61K31
IPC codes: A61K31, A61P31, C07D499