IE83796B1 - Antibacterial penem esters derivatives - Google Patents

Description

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 (IV); wherein R3 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 (Japanese Patent Laid—Open No. /1986, corresponding to EP—A—Ol99446).

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 (l988)] that, among 2—substituents of penem, lR)—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 (V): following formula wherein R4 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.

The bioavailability of the above- described compounds pane 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- only a few study reports of this type on penem and carbapenem antibiotics [J. Anti- biotics, 36, 938 (1983); Japanese Patent Laid-Open No. 67287/1990]. There has therefore been interest in cines. There are, however, determining whether or not the approaches used for penicillin and cephalosporin antibiotics are equally applicable to penem compounds.

GB-A-2206578 discloses the preparation of the penem compounds of formula (V) in which R4 is hydrogen (and salts thereof) by enzymic hydrolysis of a compound corresponding to formula (V) in which R4 is CHR’3OOCR’4, wherein R’3 is hydrogen or CH; alkyl and R’.«, is hydrogen or C148 alkyl, alkenyl, phenyl or phenylalkyl.

EP-A-0295100 discloses that certain esters of [5R,6S][(R) hydroxyethyl)methoxymethyl]-penemcarboxylic acid are prodrugs which are tract after subsequently hydrolysed in the bloodstream by aspecific serum esterases. Said absorbed from the gastro-intestinal oral administration and esters include the 2-oxo-1,3-dioxolanyl, (2-oxo—1,3-dioxolen—4—yl)methyl and 2- oxotetrahydrofuranyl esters in which said dioxolanyl or dioxolenyl ring can be substituted in the 5-position by C14 alkyl or phenyl and said tetrahydrofuryl ring can be substituted at the 4-position by C1-C4 alkyl. The only two exemplified esters tested were the acetoxymethyl and 5-rnethyloxo-1,3-di-oxolen yl)methyl esters and they are reported to have substantially the same oral bioavailability.

Hans Bundgaard in Chapter 2 of “Bioreversib|e Carriers in Drug Design, Theory and Application (Ed. E.B. Roche, Pergamon Press, 1987, 13-16) discusses the use of esters as prodrugs for drugs having carboxyl, hydroxyl or thiol groups. Reference is made to acyloxyalkyl esters of B—lactam antibiotics, cromoglycic acid, isoguvacine, methyldopa and tyrosine. Reference also is made to the 5-methyloxo-1,3-dioxolenyl)methyl esters of methyldopa and “a similar ester type of ampicillin”.

Disclosure of Invention The present inventors have carried out an ex- tensive investigation on the compounds (V) 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.

The present invention provides a penem compound represented by the following formula (I) wherein R represents a group of the general formula (II) -CH OCO—Y (II) in which Y represents a tetrahydrofuryl group.

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 (VI) with a penem compound (V') in accordance with the following formula: wherein X represents a halogen atom, R4 represents a hydrogen or alkali metal atom or an amino residuum, and R has the same meaning as defined above. when R4 in the compound (V') is an alkali metal atom or an amino residuum in this invention, the target compound can be obtained by stirring the compound (V') and the halogenated alkyl compound (VI) in an organic solvent. when R4 in the compound (V') is a hydrogen atom, on the other hand, it is first reacted with an alkali metal hydroxide, an alkali metal salt or an amine com- pound in an organic solvent to form a salt. The halogenated alkyl compound (VI) is then reacted with the reaction mixture, whereby the target compound is synthesized.

The halogenated alkyl compound represented by the formula (VI) serves to efficiently esterify the carboxyl group of the compound (V’) with the group R so that the target compound of the formula (l) is prepared. Compound (VI) includes those containing, as the group R, a tetrahydrofuryl-carbonyloxymethyl group, or its optically active isomer such as an (R)tetrahydrofuryl-carbonyloxymethyl group or an (S)tetrahydrofuryl—carbonyloxymethyi 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 (V’). 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 amine 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 (V) accordance with the process proposed by B. Balzer et al. [J. Antibiotics, 33, 1183 (l980)l it with a carboxylate salt represented by the following (VII):' into its chloromethyl or iodomethyl ester in and then reacting formula Y —COOM (VII) wherein Y is as defined above 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 pwse 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.

Example 1 (Intermediate Compound Preparation) Chloromethyl (5R,6S)—6—[(R)—l—hydroxyethyl]- 2-[(R)~2-tetrahydrofuryl]penemcarboxylate (Compound 5) To the mixture of sodium (5R,6S)—6—[(R)—l- hydroxyethyl]—2—[(R)—2—tetrahydrofuryl]penem—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 (70 ml) were added. Into the resultant mix- (ll.5 g) diluted in methylene chloride (280 ml) was added drop- chloride ture, a solution of Chloromethyl chlorosulfate 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 (Intermediate Compound Preparation) iodomethyl (5R,6S)—6—[(R)—1—hydroxyethyl]— 2-[(R)—2—tetrahydrofuryl]penemcarboxylate (Compound 5) (5R,6S)-6—[(R)—1- hydroxyethyl][(R)—2—tetrahydrofuryl] penem—3— The mixture of chloromethyl (225 (2 ml) was stirred over night at room carboxylate (Compound 5, 334 mg), sodium iodide mg) and acetone 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 (Comparative Compound Preparation) (5R,65)-6—[(R)—1— hydroxyethyl]—2—[(R)tetrahydrofuryl]penem—3— [5- (Compound 2): carboxylate (SR,6S)~6—[(R)—1~ hydroxyethyl][(R)—2—tetrahydrofuryl]penem—3— The mixture of iodomethyl carboxylate (Compound 6, (3.83 g) was allowed to stand overnight at —20°C. .4 g), and N,N—dimethylformamide sodium monoallyl— glutarate (20 ml) 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 (SR! '6‘ [(R)—l~hydroxyethyl][(R)—2—tetrahydrofuryl]- (R)-2~tetrahydrofurylcarbonyloxymethyl penem—3—carboxylate (Compound 3): The mixture of iodomethyl (SR,6S)~6—[(R)—l— hydroxyethyl]—2—[(R)-2—tetrahydrofuryl]penem—3— .4 g), (R)—tetrahydro—2— (1.38 g) and N,N—dimethyl— carboxylate (Compound 6, furoic acid sodium salt 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)—l—hydroxyethyl]a2-[(R)—2—tetrahydrofuryl]- penem—3—carboxylate (Compound 4): The mixture of iodomethyl (5R,6S)—6-[(R)—l— hydroXyethyl]~2—[(R)—2—tetrahydrofuryl]penem—3~ (S)—tetrahydro—2— furoic acid sodium salt (1.38 g) and N,N—dimethyl— carboxylate (Compound 6, 3.4 g), formamide (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.

Physical properties of the compounds synthesized in Examplex 2-6 are summarized in Table 1. .~:n.._.~:m wnn.=u.:~_mm_n u.e_xxoL.cu.m,Eu:oa ..~:~,n.u.:_.on.m ..~=m.~na._.:_._n.a ..e.:_.¢n.. m~n_.m_~_ ..__..=_o.ux;~..o..~-.a._-~...»;.. .o... ._s.:._c~...n_.. ..e.:..go.«._n.m ..~:o.o en~_.m~am ..o :c._a» .».o.cx;._..x__.o._mu.xw. _»;.ue q .~:m._.a.:u.:___~.n ..s.:_.~m.~.mn.~ ..e.:_..n.~ m~m~.m¢.m .xxo_>:oa.~u_xu:.o.nxLe..u.-~.Am. .m..~ ..e.:o.¢_.~.~n._ ..~:m.wuw.u_:m.vn__ .n.:~.cm m .A~:n‘_ufi u.n_xxon.au.n.Eu:on .n.:_._m n ..~:m.~”w._.=_.~n.m ..s.:_.om.. n~m_.c_._ .—_».:_o~ux;n..u..~..m._-m.—_x:_o .~... ..a.:..c~...n_.. ..e_:..mo...~a A ..~:o.o oe~_.-m~ _.c :o._c» .».o_n»;._..¢__.o-.mm.¢m. _x;.oe m ..:n...n.:c_:_._~.n _.a.:_.mn ~.on.~ ._a.:_._n.~ m~c~.aoqn ‘x.e_»:o;..u_».:_o.n»;...u..~..¢. .: ~ ...__.__.::.~.3_ .?__o...I..:.__2:._ . _.a. . .v _. . e. _ . . ..~_ . w.~_.eo~_ _o :o__=, ,__x.:_o.ux;a..u.,~,.¢.__-~.._x;.u _ . . . . V . . . w~m~_mmqm ._».o__»_..=_a.»xo_»__...m__ mo ~.om _ .5 :_.wa ..~~ _ _~:m gas 2 :m_.n _ .m_uou. «:2 x. uc:c.ccaa< ucaoaeou .o= c.;eo. .uu: A: H mfifim _ 15 _ COHHCm>EH asp we mwczomaou uo: % .w.:N._o 9 ..~:m._ua.:.:_.~m m ..~:n.~ua...:_.mm.m ._e.:___m_.,m_.. ..s.=N. .o_v._c n ..~:m m. :.n._"n.:n..__.m~.n ..E.:_. _c.ux.u xc__o» m~u—xxon.¢u .m.Eu:ua~_>.:.o.nxcag.u. -~-~z__‘m‘~_xz.u>xo.u>L nnc om.~.mv.~ ..e.:m.~_.~.n~._ ..~:¢.oua.n.:n.am._ ._ _a._.o-.mm.mm..x;.~eono_ . ~ . . . _ . e. .~:a.m~_~:m.mm=.un.:~.oa m 0.”_»xog_.u.n.eu=~;_.»_=_ . =n _.a n :_.nn n . =_.~n n,c~ m . :_.on ..~_ . w=o;;.ose zo__c. ~_1; ,o.n»;e..~..~..m..,~,__>;-»;o.nx; Mam . e. . . . . N . .~ . N . . . . s. . :~..o V an m A :m 0 :9 N a nu :_.m~.m . :_. ._,.«._,o..m¢.¢m. _»;_ueo.o_;u mm.~-m._~ .2 =w.mo.~,mm._ .A~=o.o"n n.=m.wm _ A:oQoVm2z r:bva2m_ mo:N5maQ< c::oaEoO .oz.yqEoO .m. H mflnme Example 6 The bioavailability of Compounds 3 and 4 of the present invention was compared with that of Compound 2 and with sodium [5R,6S]—6—[(R)—1— hydroxyethyl][(R)tetrahydrofury|]penemcarboxylate (Compound 1) relying upon their recovery rates in urine.

Each test compound (30 umole/kg) was orally administered to SD strain rats (three male rats per group). Urine was collected over 6 hours from the administration, and the recovery rate of the corresponding compound present in the urine was determined by bioassay. The results are shown below.

Table 2 C°E::d R in the compound (I) re::3::;Y(%) Ratio 1 Na 4.38 1 (Con:rol)A 2* -CH2OCO(CH2) 3COOCH2Ci-{CH2 7.53 1 7 3 -CH2OCO:\O] lO.9O 2.5 H 4 -CH2OCOJ:OJ ll.57 2.5 H * not compound of the invention _ 18 _ As is apparent from the results, the compounds 3 and of the present invention showed the higher urinaly recovery rate, in other words, a higher bioavailability compared with the Compounds 1 and 2.

Preparation Examples Preparation 1 Capsules Ingredient No.

Ingredient Invention compound Lactose Magnesium stearate (Total) (Production procedures) mggcaosule I74 mg Ingredients 1 and 2 were combined together in a suitable mixer, to which Ingredient 3 was added, followed by further mixing. resultant mixture was filled by a capsule filling machine.

Preparation 2 Tablets Ingredient No. Ingredient mgftablet Invention compound 150 Crystalline cellulose 50 Calcium carboxymethylcellulose 10 Magnesium stearate 4 (Total) ' 214 mg (Production procedures) Ingredients 1-3 were combined together in a suitable mixer, to which Ingredient 4 was added, several minutes. followed by mixing for additional The resultant mixture was compressed into tablets of a predetermined size and weight by a tableting machine.

Claims (16)

1. -. A penem compound represented by the following formula wherein R represents a group of the general formula (II) —cH2oco-Y (II) in which Y represents a tetrahydrofuryl group.

2. A compound according to Claim 1, wherein Y represents an (R)—2-tetrahydrofuryl group.

3. A compound according to Claim 1, wherein Y represents a (S)—2—tetrahydrofuryl group.

4. A compound according to Claim 1, wherein R is an optically active group. U1

5. The compound of Claim 1, which is (R)-2—tetrahydrO_ furylcarbonyloxymethyl (ER,6S){(R)hydroXyethy1}_2_ [(R)tetrahydrofuryl]-penem—3—carboxylate.

6. The compound of Claim 1, which is (S)—2-tetrahydro— furylcarbonyloxymethyl (5R,6S}—6—[(R)-l—hydroxyethyl]~2- [(R)tetrahydrofuryl]—penem—3—carboxylate.

7. An antibiotic composition, comprising an effective amount of a compound of formula (I) as defined in Claim 1 and a pharmaceutically~acceptable carrier.

8. A composition according to Claim 7, wherein said compound is as defined in any one of Claims 2 to 6.

9. A composition according to Claim 7 or Claim 8 for oral administration.

10. A penem compound according to any one of Claims 1 to 6 for use in the treatment of bacterial infections in the human or animal body.

11. The use of a penem compound according to any one of Claims 1 to 6 in the manufacture of an antibiotic medicament.

12. A method of preparing a penem compound as defined in Claim 1 which comprises: (a) reacting a penem compound of the following formula (V’) HO wherein R4 represents an alkali metal atom or an amino residuum with an halogenated compound of the following formula (VI) RX (VI) wherein R is as defined in Claim 1 and X is halogen, OI (b) reacting a penem compound of the following formula (V”) HO s I7 I59’ COOR} (V") wherein R4’ represents ~CH2X’in which X’ is chloride or iodine L with a salt of the following formula (VII) Y - COOM (VII) wherein Y is as defined in Claim 1 and M is an alkali metal atom or an amino residuum.

13. A penem compound of the formula (I) of Claim 1, substantially as herein described.

14. An antibiotic composition according to Claim 7 9 substantially as herein described.

15. The use of a penem compound according to Claim 11, substantially as herein described.

16. A method of preparing a penem compound according to Claim 12, substantiaily as herein described. MACLACHLAN & DONALDSON, Applicants’ Agents, 47 Merrion Square, DUBLIN 2.