GB1591110A

GB1591110A - Lactam derivatives

Info

Publication number: GB1591110A
Application number: GB52882/77A
Authority: GB
Original assignee: Eli Lilly and Co
Current assignee: Eli Lilly and Co
Priority date: 1976-12-23
Filing date: 1977-12-20
Publication date: 1981-06-17
Also published as: IE46280L; NL7714157A; FR2375209B1; IL53663A0; FR2375209A1; ES465358A1; DE2757083A1; IE46280B1; CA1116618A; IL53663A; JPS5392756A

Description

(54) ss-LACTAM DERIVATIVES (71) We, ELI LILLY AND COMPANY, a corporation of the State of Indiana, United States of America, having a principal place of business at 307 East McCarty Street, City of Indianapolis, State of Indiana, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to ss-lactam derivatives, and more particularly it relates to novel 3amino or 3ss-acylamino-4a-acetoxyazetidinone compounds which are useful antibacte rials for controlling ss-lactamase producing gram-negative bacteria and other pathogens, or are useful intermediates in the preparation of said antibiotics, and to a novel process for the preparation of said compounds. In invention is particularly concerned with ss-lactam antibiotics. In particular, it relates to monocyclic ss-lactam antibiotics which are 3P-acylaminoazetidin-2-ones.

The penicillins and cephalosporins are well known ss-lactam antibiotics which are bicyclic compounds containing a fused ring system. The penicillins have the 4-membered ss-lactam ring fused to a thiazolidine ring while in the cephalosporins, the ss-lactam ring is fused to a dihydrothiazine ring. Monocyclic ss-lactam antibacterial compounds are less well known.

The monocyclic ss-lactam antibiotic, nocardicin, has been recently discovered and is described in Belgium Patent No. 830,934 and by H. Aoki, et al., 15th Interscience Conference on Antimicrobial Agents and Chemotherapy, Abst. No. 97, Sep. 1975.

Nocardicin has the following structural formula.

In view of the importance of ss-lactam antibiotics in the treatment of infectious diseases, considerable effort is directed by microbiologists and chemists to the discovery and development of other ss-lactam antibiotics which possess activity against a broader spectrum of microorganisms or which are more effective than the currently available antibiotics.

The present invention provides 4a-acetoxyazetidin-2-one compounds of the formula

wherein a and a' independently are hydrogen, halogen, hydroxy, protected hydroxy, Cl-C4 alkyl, C1 -C4 alkoxy, amino, protected amino, aminomethyl or protected aminomethyl; R is amino or an acylamino group; and R1 is hydrogen or a carboxylic acid protecting group; and when R1 is hydrogen the pharmaceutically acceptable non-toxic salts thereof.

The present invention also provides a process for preparing a 4a-acetoxyazetidin-2-one compound of the formula

wherein R is amino or an acylamino group; R, is hydrogen or a carboxylic acid protecting group; and a and a' independently are hydrogen, halogen, hydroxy, protected hydroxy, Cl-C4 alkyl, C1-C4 alkoxy, amino, protected amino, amino-methyl or protected amino methyl; which comprises heating a thiazolidine azetidinone compound of the formula

wherein Ra is C,-C3 alkyl, phenyl, benzyl or phenoxymethyl; and Rl, a and a' are as defined above; with mercuric acetate in the presence of acetic acid to form a N-propenyl 4aacetoxyazetidin-2-one amide of the formula

wherein Ra, R1, a and a' are as defined above; hydrolyzing the 4a-acetoxyazetidin-2-one amide to form a 4a-acetoxyazetidin-2-one of the formula

wherein Ra, R1, a and a' are as defined above; if desired cleaving by conventional methods the 3-position acyl group to provide a compound of formula I wherein R is amino; if desired reacylating the 3-amino-4a-azetidin2-one compound so obtained by conventional methods; and optionally removing the carboxy, hydroxy or amino protecting groups.

When in the above formula R is an acylamino group, it preferably is a group of the formula

wherein R' is Cl-C4 alkyl, cyanomethyl, bromomethyl, chloromethyl, phenyl, or a group of the formula

wherein R" is hydrogen, benzyl, diphenylmethyl or 4-methoxy-benzyl; Rb is hydrogen or an amino-protecting group of the formula

wherein RC is t-butyl, 2,2,2-trichloroethyl, benzyl, 4-nitrobenzyl, cyclopentyl, or cyclohexyl; Z is = O or = N-OZ', wherein Z' is hydrogen, acetyl, chloroacetyl, triphenylmethyl or p-methoxybenzyl; or R' is a group of the formula R"-CH2wherein R" is a phenyl group of the formula

wherein b and b' independently are hydrogen, halogen, hydroxy, C1-C4 alkyl, Cl-C4 alkoxy, amino or aminomethyl; or R" is thienyl, furyl, thiazolyl, oxazolyl, isothiazolyl, tetrazolyl, or an isoxazolyl group of the formula

wherein d is hydrogen, methyl, or a group of the formula

wherein b and b' have the same meanings defined above, and d' is hydrogen, methyl, or chloro; or R' is a phenoxymethyl group of the formula

wherein b and b' have the same meanings as defined above; or R is a group of the formula R"'-S-CH2- wherein R"'is a group of the formula

wherein b and b' are as defined above, 4-pyridyl, thiazolyl, thiadiazolyl, or oxadiazolyl; or R' is a group of the formula

wherein R"" is a phenyl group of the formula

wherein b and b' are as defined above, thienyl or furyl; and Q is amino, hydroxy, carboxy, -S0311, or -NH-SO3H, or any of these groups in protected form; or R' is a group of the formula

wherein R"" has the same meanings as defined above and Z" is hydrogen, acetyl or methyl; or R' is a group of the formula

wherein R"" is as defined above and Y is a dimethylureido group of the formula

an imidazolidin-2-one group

wherein Y' is hydrogen, C1-C4 alkyl, C2-C4 alkanoyl or methanesulfonyl; or an N-methylacyl group of the formula

wherein Y" is C1-C4 alkyl, or a group of the formula

wherein n = 0 or 1 and a" is hydrogen, nitro, or chloro.

The phenyl group represented in the above definition by the formula

typically represents phenyl, 4-hydroxyphenyl, 4-(tetrahydropyran-2-yloxy)phenyl, 4benzyloxyphenyl, 3-hydroxyphenyl, 3,4-dihydroxyphenyl, 4-chlorophenyl, 3,4dichlorophenyl, 2,6-dichlorophenyl, 3-bromophenyl, 3-chloro-4-hydroxyphenyl, 3-chloro4-methylphenyl, 4-t-butylphenyl, 3,4-dimethylphenyl, 2,4-dimethylphenyl, 4-ethylphenyl, 3-methyl-4-hydroxyphenyl, 4-aminophenyl, 3-aminophenyl, 3-amino-4-methylphenyl, 2aminomethylphenyl, 4-aminomethylphenyl, 4-methoxyphenyl, 2,6-dimethoxyphenyl, 3ethoxy-4-hydroxy-phenyl, 4-isopropoxyphenyl 4-chloro-2-aminomethylphenyl, 3-bromo-4methoxyphenyl or 3-methyl-4-ammophenyl.

The phenyl group represented in the above formula by

typically represents phenyl, 4-chlorophenyl, 3,4-dichlorophenyl, 3-bromophenyl, 3-chloro4-hydroxyphenyl, 4-hydroxyphenyl, 3-hydroxyphenyl, 3,4-dihydroxyphenyl, 4methylphenyl, 4-t-butylphenyl, 4-ethylphenyl, 4-methoxyphenyl, 3-ethoxy-4hydroxyphenyl, 4-aminophenyl, 4-aminomethylphenyl, 3-methyl-4-aminophenyl, 2,6dimethoxyphenyl or 3-bromo-4-methoxyphenyl.

Illustrative of the amino-protecting groups defined in the above formula I by the formula

are t-butyl-oxycarbonyl, 2,2,2-trichloroethoxycarbonyl, benzyloxycarbonyl, pnitrobenzyloxycarbonyl, cyclopentyloxycarbonyl and cyclohexyloxycarbonyl.

As used herein the term thienyl refers to both 2-thienyl and 3-thienyl; thiazolyl refers to 2-thiazolyl and 5-thiazolyl; tetrazolyl refers to 1- and 2-tetrazolyl; thiadiazolyl refers to 1,3,4-, 1,2,5- and 1,2,4-thiadiazol-5-yl; and oxadiazolyl refers to 1,3,4-oxadiazolyl.

Examples of isoxazolyl groups represented in the above formula I by

are 3-methylisoxazol-5-yl, 3,4-dimethylisoxazol-5-yl, 4-chloroisoxazol-5-yl, 3-phenyl-4 chloroisoxazol-5-yl, 3-(4-chlorophenyl)isoxazol-5-yl, 3-(2-chlorophenyl)isoxazol-5-yl, 3-(2 chlorophenyl)-4-methylisoxazol-5-yl, 3-(2,6-dichlorophenyl)isoxazol-5-yl, 3-(2,6dichlorophenyl)-4-methylisoxazol-5-yl, isoxazole-5-yl, 3-(2,4-dimethylphenyl)-4- methylisoxazol-5-yl, 3-(2,6-dimethylphenyl)-4-chloroisoxazol-5-yl, 3-(4methoxyphenyl)isoxazol-5-yl, 3-(2, 6-dimethoxyphenyl)-4-chloroisoxazol-5-yl, 3- (3-chloro- 4-hydroxyphenyl)-4-methylisoxazol-5-yl, 3-methyl-5-chloroisoxazol-4-yl, 3,5dimethylisoxazol-4-yl, 3-phenyl-isoxazol-4-yl, 3-(4-chlorophenyl)-5-methylisoxazol-4-yl, 3 (2-chlorophenyl)-5-chloroisoxazol-4-yl and 3-(2,6-dimethoxyphenyl)-5-methylisoxazol-4-yl.

The compounds of the formula I can be characterized as monocyclic p-lactam antibiotics or as azetidin-2-ones which are substituted in the 1-position with an a-carboxybenzyl or a-carboxy-substituted benzyl group and in the 3-position by a amino or ss-acylamino group and which also are substituted in the 4-position with an actoxy group.

The thiazolidine azetidinone starting material represented by the formula II may be prepared according to the following method. L-cysteine is reacted with dry acetone at the reflux temperature to provide 2,2,-dimethyl-4-thiazolidinecarboxylic acid. The product is acylated with an acyl chloride in the presence of propylene oxide to provide 3-acyl-2,2dimethyl-4-thiazolidinecarboxylic acid represented by the following formula.

wherein Ra is as defined above.

The thiazolidinecarboxylic acid is coupled with an ester of a phenylglycine represented by the formula,

wherein a, a', and R1 are as defined herein to form the amide represented by the following formula

The coupling reaction is carried out by first preparing the active ester of the thiazolidinecarboxylic acid formed with 1-hydroxybenzotriazole (HBT). The active ester then is reacted with the phenylglycine ester in the presence of dicyclohexylcarbodiimide.

Phenylglycine esters which can be used to form the above amides include for example, benzyl phenylglycinate, 4-methoxybenzyl phenylglycinate, benzyl 4methoxyphenylglycinate, benzyl 4-chlorophenylglycinate, benzyl 3,4dimethylphenylglycinate, benzyl 4-hydroxyphenylglycinate, 2,2 ,2-trichloroethyl phenylglycinate, 4-methoxybenzyl 3-chloro-4-hydroxyphenylglycinate, benzyl 4-t-butylphenylglycinate, benzyl 4-aminophenylglycinate, and 2,2,2-trichloroethyl 3,4dichlorophenylglycinate. When the phenylglycine ester is substituted with a reactive functional group which can interfere with the desired coupling reaction (N-acylation), for example, a phenolic OH group or an amino group, such groups are blocked during the amidation reaction and in subsequent reactions in the process. The amino group can be blocked with the t-butyloxycarbonyl (t-BOC) group or the benzyloxycarbonyl group. A phenolic hydroxy substituent is best blocked with the benzyl group or tetrahydropyran group.

The thiazolidine amide of the above formula is then heated at the reflux temperature in a hydrocarbon solvent such as benzene or toluene with benzoyl peroxide to form the Sa-benzoate derivative represented by the formula

The benzoate is reacted in methylene chloride at about 0 C. with hydrogen chloride to form the corresponding Sa-chloro compound by replacement of the benzoate function. The Sa-chloro amide is reacted with sodium hydride under anhydrous conditions in a halogenated hydrocarbon solvent, such as methylene chloride, at a temperature between about 0 C. and about 30"C. to effect an intramolecular cyclization and provide the substituted thiazolidine azetidin-2-one represented by the following formula.

For convenience the compounds of the above formula are referred to herein as thiazolidine azetidinone derivatives. These compounds formally are named 2-acyl-3,3dialkyl-7-oxo-a-[substituted phenyl]-4-thia-2,6-diazobicyclo-[3 .2. 0]heptane-6-acetic acid esters.

The compounds of formula I are prepared by the process outlined above. The reaction of the thiazolidine azetidinone with mercuric acetate is carried out in acetic acid or in an inert co-solvent with acetic acid. Co-solvents such as tetrahydrofuran, dioxane, dimethylformamide, or dimethylacetamide can be used. A large excess of acetic acid is employed while between 1 mole and 3 moles of mercuric acetate per mole of the thiazolidine azetidinone is used. Preferably, 1.5 to 2.0 moles of mercuric acetate per mole of starting material is employed.

The reaction preferably is carried out in acetic acid with heating at a temperature between 25 and 75"C. The reaction mixture is filtered after the reaction is complete to remove insoluble mercury compounds and the filtrate is evaporated. The product is then extracted from the residue with a water immiscible organic solvent such as ethyl acetate.

The product, a N-propenylamide of the foregoing formula III, need not be purified for its hydrolysis to the amide. The hydrolysis is best carried out between 15 and 55 C. in a water-miscible solvent, for example, tetrahydrofuran, with dilute hydrochloric acid, for example, between 2 percent and 10 percent hydrochloric acid. Dilute sulfuric or dilute phosphoric acid also can be used. Alternatively, the hydrolysis may be carried out in aqueous tetrahydrofuran, preferably 50% aqueous tetrahydrofuran, with mercuric acetate.

Preferably an amount of mercuric acetate equal in weight to the amount of Npropenylamine is employed. The hydrolysis can be carried out at a temperature between 15"C. and 45"C. and preferably at 20"C. to 250C.

After the hydrolysis of the N-propenylamide is complete, the reaction mixture is evaporated and the residue containing the product is dissolved in a water immiscible solvent such as ethyl acetate and the solution is washed with a dilute base such as sodium bicarbonate to remove traces of acid. The product, an ester of 1-[a-(carboxyl)-benzyl or substituted benzyl]-3ss-acylamido-4a-acetoxy-azetidin-2-one represented by the foregoing formula IV is recovered from the washed solution and can be further purified by chromatography over silica gel.

The 3ss-amino-4a-acetoxyazetidin-2-ones are readily prepared from the 3ss-acylamido-4a- acetoxy hydrolysis product via N-deacylation. by conventional methods; for example by reaction with phosphorous pentachloride in the presence of pyridine to form the intermediate acylimido chloride; reaction with methanol to form the acylimido ether; and hydrolysis of the ether.

The 3ss-acylaminoazetidin-2-ones represented by the formula I wherein R is an acylamino group of the formula

may be-prepared via the acylation of the 3amino nucleus compounds. The acylation is carried by methods which commonly are employed in the cephalospoTin and penicillin art.

The acylation is best carried out with an active derivative of the carboxylic acid R'-COOH.

Active derivatives of these acids include the acyl halides such as the acid chlorides or bromides, the acid azides, and the mixed anhydrides formed with methyl chloroformate, ethyl chloroformate, or iso-butyl chloroformate. Also, acylation can be carried out with the free carboxylic acid with a condensing agent such as dicyclohexylcarbodiimide as described in U.S. Patent No. 3,218,318. The acylation is preferably carried out via the acid halide method or via the mixed anhydride method. The acylation via acyl halides can be carried out in an aqueous or non-aqueous solvent in the presence of a hydrogen halide acceptor such as sodium bicarbonate, a tertiary amine such as triethylamine or pyridine or an alkylene oxide such as propylene oxide or butylene oxide. The mixed anhydride method of acylation is carried out under anhydrous conditions in the presence of triethylamine.

The carboxylic acids

employed in the synthesis of the compounds of the formula I are readily available either from commercial sources or via known preparative methods.

During the preparation of the compounds of formula I any reactive functional groups, such as the amino, hydroxy, or carboxy, groups, are protected with a suitable blocking group. Numerous carboxy, hydroxy, and amino-protecting groups which are employed in the penicillin and cephalosporin art for the protection of such groups during the chemical reactions can be employed in the preparation of the compounds described herein. For example, the amino group can be protected with the t-butyloxycarbonyl group or the 2,2,2-trichloroethoxycarbonyl group; the hydroxy group can be protected with the benzyloxycarbonyl group or a substituted benzyloxycarbonyl group, for example, 4nitrobenzyloxycarbonyl or the protecting group formed by reacting the hydroxy group with methyl vinyl ether; and the substituents which are acidic, such as the carboy, sulfo, or sulfamino groups, can be protected with a suitable carboxylic acid blocking group for example an ester such as benzyl, a substituted benzyl group, for example, 4-nitrobenzyl, 4-methoxybenzyl, or 2,4,6-trimethylbenzyl, the diphenylmethyl ester group, the trihaloethyl ester groups for example 2,2,2-trichlotoethyl, or other suitable carboxylic acid blocking group. These blocking groups for the above-defined functional groups are selected from those groups recognized as functional blocking groups which are readily cleaved following the reaction.

The azetidin-2-one compounds represented by the formula I wherein R is an acylamino group of the formula

may be prepared by acylating a 3ss-aminoazetidin-2-one nucleus compound with the amino-protected and esterified 4- (3-carboxy-3-aminopropoxy)phenylglyoxylic acid or the oxime or protected oxime thereof. This acid and the oxime or protected oxime may be prepared by the following method.

An amino protected salt of D-methionine of the formula

for example, the salt wherein M is dicyclohexylammonium and Rb is as previously defined herein, is converted to the trimethylsilyl ester and is alkylated on the sulfur atom with an alkyl or benzyl iodide, for example methyl iodide, and the alkylsulfonium iodide of the formula

is reacted in an inert solvent with potassium t-butoxide to form the cyclic amino-protected D-homoserine lactone of the formula

The lactone is hydrolyzed with an alkali metal hydroxide to the amino-protected D-homoserine alkali metal salt of the formula

wherein M' is sodium or potassium, and the latter is converted to an acid labile ester e.g., diphenylmethyl ester. The esterified D-homoserine is then coupled with 4-hydroxyphenylglyoxylic acid p-nitrobenzyl ester with a trialkyl or triaryl phosphine, preferably triphenylphosphine, and diethyl azodicarboxylate to form the amino-protected diester of the formula

The p-nitrobenzyl ester group is selectively de-esterified by reduction whereby the other ester RB, which is selected from among the acid-labile ester groups, remains substantially intact. For example, the p-nitrobenzyl ester group is removed via reduction with sodium sulfide while the ester group R", which can be an acid sensitive group such as the diphenylmethyl group, remains unaffected under the reduction conditions. The selective de-esterification product, the phenylglyoxylic acid,. is represented by the formula

The amino-protected and esterified phenylglyoxylic acid is converted to an active ester which is used to acylate a 3ss-aminoazetidin-2-one nucleus compound. After acylation the a-ketoacylamide intermediate is converted to the biologically active oxime. For example, 4-[3-(t-butyloxycarbamido)-3-(diphenylmethoxycarbonyl)propoxy]-phenylglyoxylic acid is converted to the active ester formed with 1-hydroxybenzotriazole by using dicyclohexylcarbodiimide as condensing agent and the ester is coupled with 1-[a-(benzyloxycarbonyl)-4 benzyloxybenzyl]-3B-amino-4a-acetoxyaze to provide 1-[α- (benzyloxycarbonyl)-4-benzyloxybenzyl]-3ss-[4-(3-t-butyloxycarbamido)-3-(di phenylmethoxyCarbonyl)propoxy]phenylglyoxylamido-4a-acetoxyazetidin-2-one represented by the following formula.

wherein DPM = diphenylmethyl; t-BOC = t-butyloxycarbonyl; and Bz = benzyl.

The above a-ketoamide is then converted to the oxime derivative with hydroxylamine hydrochloride in the presence of a weak base such as sodium bicarbonate, and the t-BOC group, the DPM and benzyl groups removed to provide the antibiotic of the formula I as shown below.

Alternatively, the nocardicin side chain can be synthesized by first forming the protected oxime of the 4-hydroxyphenylglyoxylic acid ester and then coupling the oxime ester with the amino-protected and and esterified D-homoserine fragment followed by selective de-esterification of the glyoxylic acid ester. For example p-nitrobenzyl 4hydroxyphenylglyoxylate is reacted with hydroxylamino hydrochloride and the oxime is reacted with potassium t-butoxide followed by p-methoxybenzyl bromide to form the O-(p-methoxybenzyl)oxime. The oxime fragment is then coupled by the above described method with D-3-(t-butyloxy-carbamido)-3-(diphenylmethoxycarbonyl)propanol (an amino protected and esterified D-homoserine) to form p-nitrobenzyl D-4-[3-(t butyloxycarbamido)-3-(diphenylmethoxycarbonyl)-propoxy]phenylglyoxylate O-(p-methoxybenzyl)oxime represented by the formula

wherein DPM = diphenylmethyl, t-BOC = t-butyloxycarbonyl, pMB = p-methoxybenzyl and pNB = p-nitrobenzyl.

The p-nitrobenzyl ester group is then removed by chemical reduction for example with zinc and acid or by electrolytic reduction to provide the free carboxylic acid for acylation of the 3amino nucleus.

Examples of the azetidin-2-ones of formula I wherein R is

are listed in the table below with reference to the following structural formula.

R"" phenyl phenyl 2-thienyl 2-furyl 4-hydroxyphenyl phenyl phenyl 2-thienyl 2-furyl phenyl

Examples of the antibiotic compounds of formula I wherein R is a group of the formula

are illustrated in the following table.

R"" Z" a phenyl H H H phenyl CH3 4-OH H phenyl CH3 H H phenyl H 4-OH H phenyl H 4-OH 3-Cl 2-thienyl CH3 H H 2-thienyl H 4-OH H 2-thienyl CH3 4-Cl H 2-thienyl CH3 4-CH3 H 2-thienyl CH3 4-nitro H 2-furyl H 4-OH H 2-furyl CH3 4-OH H 2-furyl CH3 H H 2-furyl CH3 4-OH 3-Cl 2-furyl H 4-Br H 2-furyl CH3 3-CH3 4-CH3 The a-oximino and a-methoximino substituted azetidin-2-ones can have either the syn or anti configuration and their preparation as described above can lead to mixtures of both configurations. The preferred configuration is the syn configuration.

Examples of the compounds of formula I wherein R is the group R"-CH2-C(O)-NH- are listed in the table below wherein reference is made to the following structural formula.

R" a phenyl H H 4-hydroxyphenyl 4-OH H phenyl 4-OH H phenyl 3-OH H 2-thienyl H H 2-thienyl 4-OH H 2-thienyl 4-OH 3-Cl 2-furyl H H 2-furyl 4-NH2 H thiazol-4-yl H H isothiazol-5-yl 3-Br H oxazol-5-yl H H oxazol-5-yl 4-CH3 3-CH3 oxazol-5-yl 4-OH H 1H-tetrazol-l-yl H H lH-tetrazol-1-yl 4-NH-CH3 H isoxazol-4-yl H H 3-methyl-4-chloro- 4-OH H isoxazol-5-yl 3-(2-chlorophenyl) isoxazol-4-yl- H H 3,4-dichloro isoxazol-5-yl 4-OH 3-Cl 3-chloro-4-methyl isoxazol-5-yl H H 3 ,5-dimethylisoxa- zol-4-yl 4-OCH3 3-OCH3 Examples of the compounds of formula I wherein R is the acylamino group R"'-S-CH2-C(O)-NH- are given in the table below with reference to the following structural formula.

R"' a phenyl H H phenyl 4-OH H phenyl 4-Cl H 3,4-dichloro phenyl 4-OH 3-OCH3 3,5-dichloro phenyl 4-OH 3-Cl 3-methyl-4 hydroxyphenyl 4-OH H 4-pyridyl H H 4-pyridyl H 3-OH 4-pyridyl 3-Cl H 4-pyridyl 4-Br H 4-pyridyl 3-OC2Hs 4-OH 2-thiazolyl 4-OH H 1,3 4-thiadia- zol-2-yl H H 1,3 ,4-thiadia- zolyl-2-yl 4-OH 3-Cl 1,3 4-oxadia- zol-2-yl H H 1,3 4-oxadia- zol-2-yl 3-CH3 4-CH3 Examples of the compounds represented by the formula I wherein R is a group of the formula

are listed below with reference to the following structural formula.

R"" Q a phenyl NH2 H H phenyl NH2 4-OH H phenyl NH2 4-OH 3-Cl phenyl NH2 4-C1 H 2-thienyl NH2 4-OH H 2-furyl NH2 4-OH H 2-thienyl NH2 4-OCH3 3-CH3 phenyl OH 4-OH H phenyl COOH H H phenyl SO3H 4-OH 3-OH 2-thienyl COOH H H 4-hydroxyphenyl NH2 H H 4-hydroxyphenyl COOH 4-OH 3-Cl 2-furyl SO3H H 2-OCH3 3-chloro-4 hydroxyphenyl OH 4-OH H 2-thienyl OH 4-Cl H 2-thienyl -SO3H 4-OC2Hs H 4-chlorophenyl OH 4-OH 3-CH3 The 3ss-acylaminoazetidin-2-ones represented by formula I wherein RI, R", Rb and Z' are hydrogen, a and a' are other than protected hydroxy, protected amino or protected aminomethyl, and Q is other than a protected moiety, are useful antibiotics which inhibit the growth of pathogenic microorganisms. These compounds are resistant to inactivation by the ss-lactamases and possess activity against the gram-negative bacteria which proliferate these enzymes, for example, proteus, pseudomonas, enterobacter sp., serratia and klebsiella.

The compounds are administered parenterally, for example subcutaneously, intramuscularly or intravenously, preferably in the form of a pharmaceutically acceptable non-toxic salt.

The esterified, amino-protected, oxime-protected and hydroxy-protected azetidinones represented by the formula I useful as intermediates in the synthesis of the antibiotic compounds.

The azetidin-2-one antibiotics represented by the formula I have an acidic carboxylic acid group which forms salts with suitable bases. Pharmaceutically acceptable salts include the alkali metal salts such as the sodium, potassium, or lithium salt; the calcium salt; and salts formed with pharmaceutically acceptable amines, for example, mono- and diethanol amine, procaine, cyclohexylamine, dicyclohexylamine, dibenzylamine, abietylamine, trimethylamine, or triethylamine.

3ss-Acylaminoazetidin-2-ones of the formula XI wherein Q is an amino group can form acid addition salts, for example, the hydrochloride or hydrobromide salts. Likewise, when a phenyl group substituent a or a' and b or b' is amino, acid addition salts of the antibiotics can be prepared.

Further, it will be appreciated that the 3amino and 3ss-acylamino which contain an a-amino substituent in the side chain (Q = NH2) can form intramolecular salts (zwitterions) where R1 is hydrogen.

The 3ss-aminoazetidin-2-one nucleus compounds represented by the formula I when R is an amino group are useful intermediates in the preparation of the 3ss-acylaminoazetidin-2- one antibiotics. As described previously herein when the phenyl group of a-carboxybenzyl substituent in the 1-position of the azetidin-2-one ring is substituted with hydroxy or amino groups, such groups are preferably blocked with a suitable blocking group during synthesis for example, during N-acylation or N-de-acylation. These nucleus compounds containing such blocked groups as well as esters of the nucleus compounds are also valuable intermediates. Examples of these nucleus compounds are listed below with reference to the following formula.

R1 a a' H H H H 4-OH H benzyl 4-benzyloxy H benzyl 4-Cl H DPM1 H 2-Cl pNB2 4-O-pNB 3-Cl pNB 4-benzyloxy 3-CH3 H 4-OH 3-Br pMB3 2-CH3O 4-CH3 The carboxylic acid'protecting groups-represented by R1 in the formula I are carbon esters commonly used to temporarily protect or block the carboxylic acid function in other ss-lactam antibiotics such as the penicillins and cephalosporins. Examples of these ester groups include the haloalkyl groups such as the trichloroethyl and tribrdmoethyl groups; the benzyl and substituted benzyl groups such as p-nitrobenzyl, p-methoxybenzyl, 3 ,5-dimethoxybenzyl, 2,4 ,6-trimethylbenzyl; diphenylmethyl (benzhydryl), 4methoxydiphenylmethyl; or t-butyl. Methods for the removal of these esters groups are well known and are described in the literature.

As previously described herein, the 3-amino or 3-acylamino substituent R in the formula I has the (3-configuration. The 4-acetoxy substituent group is provided in the aconfiguration by the process described herein.

The a-carboxybenzyl or a-carboxy-substituted benzyl group substituted on the nitrogen atom of the azetidin-2-one ring (1-position) can have either the D or L configuration and the D configuration is preferred. The process for preparing 3ss-amino-4a-acetoxyazetidin-2- one nucleus described herein provides the preferred D-configuration when the phenylglycine employed in the process has the D-configuration.

Likewise the compounds of the formula I wherein R is the acylamino group

can have either the D or L configuration. The described compounds having the D configuration are preferred.

Certain of the compounds of formula I are preferred over others. A preferred group is represented by the formula I when R is an acylamino group of the formula

Preferred among these compounds are those wherein R" and Rb are hydrogen, Z is the' hydroxyimino group, a is 4-hydroxy, and a' is hydrogen. An especially preferred compound is 4a-acetoxynocardicin represented by the formula

A preferred intermediate useful in the preparation of the above 4a-acetoxynocardicin is represented by the formula

Another preferred group of compounds of formula I are represented when R is benzoylamino, phenylacetylamino, or phenoxyacetylamino. These compounds are products of the process provided herein for the synthesis of the 4-acetoxy substituted azetidin-2-ones and can be used in the synthesis of the 3-amino-4-acetoxyazetidin-2-one nucleus as previously described.

The following examples are provided to further describe the compounds and process of this invention Preparation 1 Preparation of 2-benzoyl-3 ,3-dimethyl-7-oxo-a-(4-benzyl-oxyphenyl)-4-thia-2 6- diazabicyclo[3.2.0]heptane-6-acetic acid benzyl ester.

A slurry of 100 g. of L-cysteine in 2 1. of dry acetone was heated at the reflux temperature for about 17 hours. After the reaction mixture was allowed to cool to about 30"C. the unreacted cysteine was filtered and the reaction product, 2,2-dimethyl-4thiazolidinecarboxylic acid, crystallized from the filtrate. Three crops of the product were obtained via successive filtrations. The combined weight of product was 83 g.

To a suspension of 16 g. (100 mM) of the product in 300 ml. of dry acetone were added 21 ml. of propylene oxide. Next, 11.6 ml. (100 mM) of benzoyl chloride were added dropwise with vigorous stirring. The temperature of the reaction mixture slowly increased from about 25"C. to about 33"C. After an hour all of the thiazolidine had dissolved and the reaction solution began to cool. When the temperature had dropped to 300C. the reaction solution was evaporated to yield a white solid residue. The solid was dissolved in acetone and was diluted with hexane to crystallize the product. The product, 3-benzoyl-2,2-dimethyl-4thiazolidinecarboxylic acid, was filtered and dried. The dried product weighed 18.7 g.

To a solution of 48 g (181 mmole) of 3-benzoyl-2,2-dimethyl-4-thiazolidinecarboxylic acid, prepared by the procedure described above in 1.5 1. of tetrahydrofuran were added 27.8 g (181 mmole) of 1-hydroxybenzotriazole followed by 37.4 g (181 mmole) of dicyclohexylcarbodiimide. The mixture was stirred for 30 minutes at room temperature.

The reaction mixture developed into a thick slurry resulting from the precipitation of dicyclohexylurea. To the heavy slurry was added 63 g. (181 mmole) of benzyl D-4-benzyloxy-phenylglycinate and the reaction mixture was stirred at room temperature for about 2 hours. The reaction mixture was filtered to remove the dicyclohexylurea, the filtrate evaporated under reduced pressure, and the residue was dissolved in ethyl acetate.

The solution was washed successively with 5% hydrochloric acid, water, aqueous sodium bicarbonate, and finally with water. The washed solution was dried, treated with carbon, and evaporated to dryness under reduced pressure to yield 107 g. (99% yield) of N-[benzyl a-(D-4-benzyloxyphenyl)acetate]-3-benzoyl-2,2-dimethyl-4-thiazolidinecarboxamide .

The above thiazolidinecarboxamide ester (107 g.; 0.18 mole) was dissolved in 4 1. of benzene and 175 g. (0.72 mole) of benzoyl peroxide were added to the solution. The solution was then heated at the reflux temperature for 4.5 hours and thereafter was cooled to room temperature. The reaction mixture was poured over a column packed with silica gel and the column was eluted with benzene. Excess benzoyl peroxide passed off the column initially and on further elution with benzene, the product was collected. The eluate was evaporated under reduced pressure to provide the product, N-[benzyl a-(D-4 benzyloxyphenyl)acetate]-3-benzoyl-2 ,2-dimethyl-4-thiazolidinecarboxamide-5a-benzoate, as an oil. The product was obtained crystalline from diethyl ether.

The above product is represented by the following structural formula

NMR (T60, CDCl3): 2.16 (s, 2CH3), 5.08 and 5.16 (2s, 2CH2), 5.13 (s, CH), 5.54 (d, CH), 6.54 (s, CH) and 6.83-8.16 (m, aromatic H and NH) delta.

A solution of 25.5 g. (35.8 mmole) of the thiazolidine-4-carboxamide 5a-benzoate in 11.

of dry methylene chloride was cooled to a temperature of 0 C. and hydrogen chloride was bubbled through the cold solution for about 2 hours. After this time, a thin layer chromatogram developed with benzene:ethyl acetate, 7:3, v:v, showed complete reaction: The methylene chloride was evaporated under reduced pressure providing the product ds a foam. The foam was dissolved in ethyl acetate and the solution was washed with dilute aqueous solution of sodium bicarbonate and with brine, and after washing was dried over magnesium sulfate, treated with carbon, and evaporated to dryness under reduced pressure. The product, N-[benzyl a-(D-4-benzyloxyphenyl)acetate]-3-benzoyl-2,2- dimethyl-5a-chloro-4-thiazolidinecarboxamide, represented by the following formula was obtained as 22.4 g. of white foam.

NMR (T60, CDCl3): 2.12 (s, CH3), 2.26 (s, CH3), 5.08 and 5.16 (2s, 2CH2) 5.16 (s, CH), 5.44 (d, CH), 5.83 (s, CH) and 6.08-7.5 (m, 20H, aromatic H and NH) delta.

To a solution of 22.4 g. (35.8 mmole) of the 5a-chloro-4-thiazolidinecarboxamide in 800 ml. of methylene chloride and 200 ml. of dimethylformamide were added 1.72 g. of sodium hydride (50 percent in oil, 35.8 mmole). The reaction mixture was stirred at room temperature for approximately 50 minutes after which time TLC (benzene:ethyl acetate, 7:3) showed the reaction was complete. Two milliliters of acetic acid were added to the reaction mixture to destroy any excess sodium hydride, and the reaction mixture was poured into 5 percent hydrochloric acid. The organic phase was separated and was washed with 5 percent hydrochloric acid and with water before drying over magnesium sulfate. The dried extract was treated with carbon, filtered, and evaporated to dryness under reduced pressure. The residue was dissolved in about 30 ml. ethyl acetate. On standing, 10:1'g.

(crop 1 of product, 2-benzoyl-3,3-dimethyl-7-oxo-a-(4-benzyloxyphenyl)-4-thia-2,6-diàza- bicyclo 3,2.0]heptane-6-acetic acid benzyl ester, crystallized. The crystals were filtered and the filtrate was treated with petroleum ether to the cloud point. On standing and with agitation, 5.5 g. (crop 2) of additional product crystallized. The second crop material was filtered and the filtrate was evaporated to dryness to yield further product as a foam. The foam was treated with a mixture of ethyl acetate and ethyl alcohol which afforded 2.2 g. of additional crystalline product (crop 3).

An analysis of the nuclear magnetic resonance spectrum (T-60) of the above crops demonstrated that crop 1 was the D isomer of the cyclized product represented by the formula shown below, crop 2 was the L isomer, while crop 3 was a mixture of the two isomers.

NMR (T60, CDCl3): 1.70 (s, CR3), 1.91 (s, CR3), 5.08 and 5.16 (2s, 2CH2), 5.45 (s, CH), 5.52 (m, 2CH), and 6.83-7.67 (m, 19H, aromatic H) delta.

The above thiazolidine azetidinone was also prepared from the Sa-chlorothiazolidine carboxamide and the base diazabicyclo[5.4.0]undec-5-ene(DBU) in the following manner.

A solution of 1.01 g. (1.6 mmole)' of the 5a-chloro-4-thiazolidinecarboxamide having the D-configuration in 50 ml. of methylene chloride was cooled to a temperature of about 0 C.

To the cold solution was added 0.243 g. (1.6 mmole) of DBU. The reaction mixture was stirred for 2 hours at 0 C. and then was washed with 5 percent hydrochloric acid and with brine and was then dried over magnesium sulfate. The solution was evaporated to yield a crude reaction product mixture. The mixture was crystallized from benzene/petroleum ether and the crystals filtered. The infrared spectrum of the product showed an absorption peak at 1775 cm-' for the ss-lactam carbonyl, while the nuclear magnetic resonance spectrum and circular dichromism showed the material to be optically pure.

Example I Preparation of 1-[la-(benzyloxycarbonyl)-4-benzyloxybenzyl]-3ss-benzamido-4a- acetoxyazetidin-2-one.

A slurry of 300 mg (0.505 mmole) 2-benzoyl-3,3-dimethyl-7-oxo-a-(4-benzyloxyphenyl)- 4-thia-2,6-diazabicyclo[3.2.0]heptane6acetic acid benzyl ester in 25 ml. of acetic acid was stirred and treated with 240 mg. (0.75 mmole) of mercuric acetate. The reaction mixture was heated on the steam bath for 10 minutes, and an additional 100 mg. of mercuric acetate was added and heating was continued for 5 minutes. The reaction mixture was filtered to remove the insoluble mercurous acetate and was then evaporated to dryness. The residue was dissolved in ethyl acetate and the solution was washed with a dilute aqueous solution of sodium bicarbonate and with brine, was dried and then evaporated to dryness to yield 1-[a-(benzyloxyCarbonyl)-4-benzyloxy-benzyl]-3-(N-propenylbenzamido)-4-a- acetoxyazetidinone-2 represented by the following formula.

The product was dissolved in 50 ml. of tetrahydrofuran and 5 ml. of 5 percent hydrochloric acid were added. After stirring for 15 minutes at room temperature the solution was evaporated to dryness under reduced pressure and the residue was dissolved in ethyl acetate. The ethyl acetate solution was washed with a dilute aqueous solution of sodium bicarbonate, with water, and was dried and evaporated to dryness. The residue was chromatographed on a preparative silica gel thin layer plate using benzene: ethyl acetate, 7:3, v:v, for development to obtain 144 mg. of the hydrolysis product 1-[a (benzyloxyCarbonyl)-4-benzyloxybenzyl]-3ss-benzamido-4-a-acetoxyazetidinone-2.

Example 2 By following the procedures described by Example 1 1-[a-(benzyloxycarbonyl)-4benzyloxybenzyl]-3(3-phenoxy-acetamido-4a-acetoxyazetidin-2-one is prepared with the benzyl ester of 2-phenoxyacetyl-3,3-dimethyl-7-oxo-a-(4-benzyloxyphenyl)-4-thia-2,6- diazabicyclo[3.2.0]heptane-6-acetic acid.

Example 3 Preparation of 1-[a-(benzyloxycarbonyl)-4-benzyloxybenzyl]-3ss-amino-4a- acetoxyazetidin-2-one.

To a solution of 250 mg. (q.432 mmole) of 1-[a-(benzyloxycarbonyl)-4-benzyloxybenzyl] 3ss-benzamido-4-a-acetoxyazetidinone-2 prepared as described in the foregoing Example 1 in 50 ml. of dry benzene were added 132 mg. (0.64 mmole) of phosphorous pentachloride and 50 mg. (0.64 mmole) of pyridine. The mixture was heated to a temperature of about 65"C. for 2 hours with stirring. A thin layer chromatogram was then run on the reaction mixture and demonstrated the conversion of the starting material to the corresponding imido chloride.

The reaction mixture was evaporated under reduced pressure and 50 ml. of dry methyl alcohol were added to the residue. The methyl alcohol solution was stirred at room temperature for about 30 minutes. TLC of the solution showed a new spot.

The solution was evaporated under reduced pressure and 20 ml. of water and 20 ml. of tetrahydrofuran were added to the residue and the resultant solution was stirred at room temperature for about 20 minutes. The tetrahydrofuran was evaporated from the solution and the aqueous concentrate was slurried with ethyl acetate. The pH of the slurry was adjusted to pH 7 and the ethyl acetate layer was separated. The ethyl acetate layer was dried and then evaporated under reduced pressure to afford 210 mg. of a reduction product mixture. The nuclear magnetic resonance spectrum (T-60) of the product mixture showed it contained approximately 60 percent of the desired N-deacylation product, 1-[a-(benzyl oxycarbonyl)-4-benzyloxybenzyl]-3-ss-amino-4-a-acetoxy-azetidinone-2 represented by the following structural formula.

The crude product was purified via preparative thin layer chromatography on silica gel thick layer plates to yield 62 mg. of the product and 60 mg. of recovered starting material.

Example 4 Preparation of 1-[a-(carboxy)-4-hydroxybenzyl]-3ss-(D-mandelamido)-4a- acetoxyazetidin-2-one.

To a solution of 1-[a-(p-nitrobenzyloxycarbonyl)-4-benzyloxybenzyl]-3ss-amino-4a- acetoxyazetidin-2-one in tetrahydrofuran maintained at 0-5"C. are added pyridine and O-formyl mandeloyl chloride. The mixture is stirred in the cold for about 2 hours and is then evaporated. Water is added to the residue and the acylation product is extracted with ethyl acetate. The extract is washed with water, dilute acid, and again with water and is dried and then evaporated to yield the esterified N-acylation product, 1- a-(p- nitrobenzyloxycarbonyl)-4-benzyioxybenzy -4aacetoxyazetidin-2-one. The ester is de-esterified with zinc and acetic acid during which the 4-benzyloxy group is removed to provide the title compound.

Example 5 Preparation of 1-[a-(carboxy)-4-hydroxybenzyl]-3ss-[2-[4-(3-carboxy-3- aminopropoxy)phenyl]-2-hydroximinoacetamido] -4a-acetoxyazetidin-2-one .

To a solution of 32 mg. of 1-[a-(benzyloxycarbonyl)-4-benzyloxybenzyl]-3ss-amino-4a- acetoxyazetidin-2-one in about 5 ml. of dry methylene chloride were added 36 mg. of 4-(3-diphenylmethoxycarbonyl-3-t-butyloxycarbamidopropoxy)phenylglyoxylic acid. The mixture was stirred at room temperature under nitrogen and 14 mg. of dicyclohexylcarbodiimide were added. The solution immediately turned a dark yellow. After 10 minutes the solution became light yellow and dicyclohexylurea precipitafed. A thin layer chromatogram of the mixture run on silica gel plates with benzene:ethyl acetate, 7:3, v:v, showed complete reaction. The reaction mixture was filtered and the filtrate was evaporated to dryness.

The acylation product was purified on preparative thick layer plates (silica gel) to yield 41 mg. of the purified intermediate product.

The product was reacted with hydroxylamine hydrochloride in aqueous tetrahydrofuran containing pyridine to form the hydroximino derivative. The oxime was reacted with trifluoroacetic acid in anisole to cleave both the t-BOC amino-protecting group and the diphenylmethyl ester group of the side chain. After treatment with the acid, the reaction mixture was evaporated to dryness and the residue was vigorously triturated with diethyl ether. The insoluble product, 1[a(benzyloxycarbonyl)-4-benzyl6xybenzylj-3(3-[2-[4-(3- carboxy-3-aminopropoxy)phenyl]-2-hydroxyimino-acetamido]-4a-acetoxyazetidin-2-one trifluoroacetate salt, was filtered and dried.

The salt was dissolved in dry methylene chloride and was treated with a solution of excess aluminum chloride and anisole in nitromethane to effect the removal of both benzyl ester groups. The reaction mixture was quenched with water and the pH adjusted to about 8.0 with sodium bicarbonate. The solution was washed with ethyl acetate and was then chromatographed over Sephadex. The title compound was obtained as the disodium salt by evaporation of the eluate.

The course of the debenzylation reation is followed by thin layer chromatography over silica gel using acetic acid:acetone, 4:1, v:v, for development.

Example 6 Preparation of 1-[a-(diphenylmethoxycarbonyl)-4-hydroxybenzyl]-3ss-amino-4a- acetoxyazetidin-2-one.

A solution of 4 g. of 2-benzoyl-3,3-dimethyl-7-oxo-a-(4-hydroxyphenyl)-4-thia-2,6 diazabyciclo[3.2.0]-heptane-6-acetic acid and 5 g. of diphenyldiazomethane in 500 ml. of dry tetrahydrofuran was stirred at room temperature for about 18 hours. The reaction mixture was evaporated under reduced pressure to dryness and the residue was dissolved in ethyl acetate. The diphenylmethyl ester product, 2-benzoyl-3,3-dimethyl-7-oxo-a-(4 hydroxyphenyl)-4-thia-2 ,6-diazabyciclo[3 .2.0]heptane-6-acetic acid diphenylmethyl ester, crystallized from solution. 3.5 Grams of the diphenylmethyl ester were obtained.

To a suspension of 1 g. of the diphenylmethyl ester in approximately 100 ml. of acetic acid were added with stirring 1 g. of mercuric acetate. The reaction mixture was heated on the steam bath for approximately 10 minutes with continued stirring. The reaction mixture was filtered to remove the insolubles and was evaporated under reduced pressure to dryness. The reaction product mixture obtained as a residue was dissolved in ethyl acetate and the solution was washed with a dilute aqueous solution of sodium bicarbonate and with brine and was then dried and evaporated to dryness to yield 1.1 g of 1-[a diphenylmethoxyCarbonyl)-4-hydroxybenzyl]-3-(N-propenylbenzamido)-4a-acetoxy- azetidinone-2.

The propenyl 4a-acetoxyazetidin-2-one diphenyl-methyl ester, 650 mg. was dissolved in 50 ml. of water and 50 ml. of tetrahydrofuran and 650 mg. of mercuric acetate were added.

The reaction mixture was stirred at about room temperature for approximately 1 hour. The reaction mixture was evaporated to dryness under reduced pressure and the residue containing the hydrolysis product was dissolved in ethyl acetate. The ethyl acetate solution was washed with a dilute aqueous solution of sodium bicarbonate, water, and was then dried and evaporated to dryness. The nuclear magnetic resonance spectrum (T60) showed that complete hydrolysis of the N-propenyl group had taken place. The product, 600 mg., 1 -[a-(diphenylmethoxycarbonyl)-4-hydroxybenzyl]-3ss-benzamido-4a-acetoxyazetidinone- 2 was used without further purification as described hereinafter.

To a solution of 510 mg. of the 4a-acetoxyazetidinone-2-diphenylmethyl ester prepared as described above in 40 ml. of dry tetrahydrofuran were added 2 ml. of dihydropyran and a small catalytic amount of p-toluenesulfonic acid. The reaction mixture was stirred at about room temperature for approximately 17 hours. A silica gel thin layer chromatogram showed the presence of starting material and the desired product, the tetrahydropyranyl ether formed with the 4-hydroxybenzyl group. With continued stirring approximately 0.5 g. of sodium carbonate were added to the reaction mixture. After stirring for 15 minutes the solvent tetrahydrofuran was evaporated and the residue was dissolved in ethyl acetate. The ethyl acetate solution was washed with sodium bicarbonate and with water and was then dried and evaporated to dryness. The starting material and product contained in the residue were separated on a silica gel chromatographic plate employing 7:3, toluene:ethyl acetate, v:v, for elution. There were obtained 280 mg. of the product, 1-[a (diphenylmethoxycarbonyl)-4-tetrahydropyranyloxybenzyl]-3(3-benzamido-4a- acetoxyazetidinone-2 and 178 mg. of recovered starting material.

To a solution of 78.5 mg. (0.38 mmole) of phosphorus pentachloride and 29.9 mg. (0.38 mmole) of pyridine in approximately 20 ml. of dry methylene chloride were added with stirring at room temperature under nitrogen 168 mg. (0.26 mmole) of the 4aacetoxyazetidin-2-one tetrahydropyranyl ether diphenylmethyl ester. The reaction mixture was stirred at room temperature under nitrogen and periodically an aliquot was withdrawn from the reaction mixture and chromatographed on thin layer chromatography plates using benzene: ethyl acetate, 7:3 for elution. After approximately 1 hour the TLC showed only a trace of starting material and a new spot corresponding to the imino chloride. The methylene chloride was evaporated and 30 ml. of dry methyl alcohol were added to the concentrate. The methyl alcohol solution was stirred for approximately 2 hours at about room temperature. Thereafter, the methanol was evaporated and 20 ml. of water and 20 ml. of tetrahydrofuran were added to the residue. The aqueous solution was stirred for approximately 1 hour at about room temperature and thereafter the solution was evaporated to remove the tetrahydrofuran. The aqueous concentrate was extracted with ethyl acetate and the extract was dried and evaporated to dryness. The product obtained as a crude residue was purified via chromatography over silica gel to yield 81 mg. of 1 -[a-(diphenylmethoxycarbonyl) -4-hydroxybenzyl] -3ss-amino-4a-acetoxyazetidin-2-one .

Example 7 Preparation of 4a-acetoxynocardicin.

To a solution of 300 mg. (0.65 mmole) of the 4a-acetoxyazetidin-2-one nucleus diphenylmethyl ester prepared as described in the preceding example and 435 mg. (0.65 mmole of 4-[3-(diphenylmethoxycarbonyl)-3-(t- butyloxycarbamido)propoxy]phenylglyoxylic acid O-(4-methoxybenzyl)oxime in approximately 25 ml. of dry methylene chloride maintained at about room temperature under nitrogen were added 135 mg. (0.65 mmole) of dicyclohexlcarbodiimide. The reaction mixture was stirred at approximately room temperature under nitrogen for about' 2 hours.

The reaction mixture was filtered and the filtrate was evaporated to dryness. The residue was chromatographed on a preparative silica gel chromatographic plate employing toluene:ethyl acetate, 1:1, v:v for elution to obtain 391 mg. of the acylated product, the t-butyloxycarbonyl protected amino, bis-dibenzhydryl ester protected and 4-methoxybenzyl protected oxime derivative of 4a-acetoxynocardicin represented by the formula below. The NMR of the product (T60) showed a trace impurity. The product was further purified in the same chromatographic system affording 332 mg. of the purified product.

The protected bis-diphenylmethylester of 4a-acetoxynocardicin of the above formula was treated with 12 ml. of trifluoroacetic acid containing 24 drops of anisole at approximately room temperature for 3 minutes. The reaction mixture was evaporated to dryness and the residue was vigorously triturated with diethyl ether to yield 157 mg. of 4aacetoxynocardicin trifluoroacetate salt.

NMR: DMSO(D6), D2O (Trimethylsilane reference, 1.95 (s, -C(O)CR3), 2.31 (t, CR2), 4.15 (t, and d, -CH-CH,), 4.74 (d, -CH-), 5.20 (s, -CH-), 5.88 (d, -CH-) and 6.66-7.52 (aromatic H) delta.' WHAT' WE CLAIM IS: 1. A 4a-acetoxyazetidin-2-one compound of the formula

wherein a and a' independently are hydrogen, halogen, hydroxy, protected h'ydr'o*y", C1-C4 alkyl, C1-C4 alkoxy, amino, protected amino, aminomethyl, or protected aminomethyl; R is amino or an acylamino group; and Rl is hydrogen or a carboxylic acid protecting group; and when R1 is hydrogen the pharmaceutically acceptable non-toxic salts thereof.

2. A compound of claim 1 wherein R is an acylamino group of the formula

wherein R' is C1-C4 alkyl, cyanomethyl, bromomethyl, chloromethyl, phenyl, or a group of the formula

wherein Ra is hydrogen, benzyl, diphenylmethyl or 4-methoxybenzyl;

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

mixture was stirred at approximately room temperature under nitrogen for about' 2 hours.

The reaction mixture was filtered and the filtrate was evaporated to dryness. The residue was chromatographed on a preparative silica gel chromatographic plate employing toluene:ethyl acetate, 1:1, v:v for elution to obtain 391 mg. of the acylated product, the t-butyloxycarbonyl protected amino, bis-dibenzhydryl ester protected and 4-methoxybenzyl protected oxime derivative of 4a-acetoxynocardicin represented by the formula below. The NMR of the product (T60) showed a trace impurity. The product was further purified in the same chromatographic system affording 332 mg. of the purified product.

The protected bis-diphenylmethylester of 4a-acetoxynocardicin of the above formula was treated with 12 ml. of trifluoroacetic acid containing 24 drops of anisole at approximately room temperature for 3 minutes. The reaction mixture was evaporated to dryness and the residue was vigorously triturated with diethyl ether to yield 157 mg. of 4aacetoxynocardicin trifluoroacetate salt.

NMR: DMSO(D6), D2O (Trimethylsilane reference, 1.95 (s, -C(O)CR3), 2.31 (t, CR2),

4.15 (t, and d, -CH-CH,), 4.74 (d, -CH-), 5.20 (s, -CH-), 5.88 (d, -CH-) and 6.66-7.52 (aromatic H) delta.' WHAT' WE CLAIM IS: 1. A 4a-acetoxyazetidin-2-one compound of the formula

wherein a and a' independently are hydrogen, halogen, hydroxy, protected h'ydr'o*y", C1-C4 alkyl, C1-C4 alkoxy, amino, protected amino, aminomethyl, or protected aminomethyl; R is amino or an acylamino group; and Rl is hydrogen or a carboxylic acid protecting group; and when R1 is hydrogen the pharmaceutically acceptable non-toxic salts thereof.
2. A compound of claim 1 wherein R is an acylamino group of the formula

wherein R' is C1-C4 alkyl, cyanomethyl, bromomethyl, chloromethyl, phenyl, or a group of the formula

wherein Ra is hydrogen, benzyl, diphenylmethyl or 4-methoxybenzyl;

Rb is hydrogen or an amino-protecting group of the formula

wherein RC is t-butyl, 2,2,2-trichloroethyl, benzyl, 4-nitrobenzyl, cyclopentyl, or cyclohexyl; Z is =O or =N-OZ', wherein Z' is hydrogen, acetyl, chloroacetyl, triphenylmethyl or p-methoxybenzyl; or R is a group of the formula R" -CH2wherein R' is a phenyl group of the formula

wherein b and b' independently are hydrogen, halogen, hydroxy, C1-C4 alkyl, C1-C4 alkoxy, amino or aminomethyl; or R" is thienyl, furyl, thiazolyl, oxazolyl, isothiazolyl, tetrazolyl, or an isoxazolyl group of the formula

wherein d is hydrogen, methyl, or a group of the formula

wherein b and b' have the same meanings defined above, and d' is hydrogen, methyl, or chloro; or R' is a phenoxymethyl group of the formula

wherein b and b' have the same meanings as defined above; or R' is a group of the formula R"'-S- CH2- wherein R"' is a group of the formula

wherein b and b' are as defined above 4-pyridyl, thiazolyl, thiadiazolyl, or oxadiazolyl; or R' is a group of the formula

wherein R"" is a phenyl group of the formula

wherein b and b' are as defined above, thienyl or furyl; and Q is amino, hydroxy, carboxy, -SO3H, or -NH-SO3R, or any of' these groups in protected form; or R' is a proud of the formula

wherein R"" has the same meanings as defined above and Z" is hydrogen, acetyl or methyl; or R' is å group of the formula

wherein R"" is as defined above; and Y is a dimethylureido group of the formula

an imidazolidin-2-one group

wherein Y' is hydrogen, C1-C4 alkyl, C2-C4 alkanoyl, or methanesulfonyl; or an N-methylacyl group of the formula

wherein Y" is Cl-C4 alkyl, or a group of the formula

wherein n = 0 or 1 and a" hydrogen, nitro, or chloro.
3. A compound of Claim 1 or 2 wherein when R is an acylamino group it has the formula

as defined in Claim 2 provided that when Z is =N-OZ', Zl is hydrogen, and when R" is a group of formula

Q is amino, hydroxy, carboxy, -SOXH or -NH-SO3H.
4. A compound of claim 1, 2 or 3 wherein R' is a group of the formula

wherein Ra, Rb and Z are as defined in claim 2.
5. A compound of claim 4 wherein Z is =0.
6. A compound of claim 4 wherein Z is =N-OZ'.
7. A compound of claim 1, 2 or 3 wherein R' is a group of the formula

wherein R"" is as defined above and Q is amino, hydroxy, or carboxy,
8. A compound of claim 1, 2 or 3 wherein R' is phenyl, benzyl, or phenoxymethyl.
9. A compound of any of claims 1 to 3 or 8 wherein R' is phenyl.
10. A compound of claim 1, 2 or 3 wherein R' is a group 'of the formula R"-CH2wherein R" is as defined in claim 2.
11. A compound of claim 10 wherein R" is phenyl 2-thienyl, 2-furyl, or 1-tetrazolyl.
12. A compound of claim 1, 2 or 3 wherein R' is a group of the formula

wherein b and b' are as defined in claim 2
13. A compound of claim 1, 2 or 3 wherein R' is a group of the formula R"'-S-CH2- wherein "' is as defined in claim 2.
14. A compound of claim 1, 2 or 3 wherein R' is a group of the "formula

and R"" is phenyl, 2-furyl, or 2-thienyl; and Z" is as defined in'claim 2:
15. A compound of claim 1, 2 or 3 wherein R' is a group of the formula

wherein R"" and Y are as defined in claim 2.
16. A compound of claim 15 wherein Y is a dimethylureido group of the formula
17. A compound of claim 15 wherein Y is a group of the formula

wherein Y' is as defined in claim 2.
18. A compound of claim 15 wherein Y is an N-methylacyl group of the formula

wherein Y" is as defined in claim 2.
19. The compound of claim 1 wherein R is amino.
20. 1-[a-(Benzyloxycarbonyl)-4-benzyloxybenzyl]-3ss-benzamido-4a-acetoxyazetidin-2- one.
21. 1-[a-(Benzyloxycarbonyl)-4-benzyloxybenzylj-3(3-phenoxyacetamido-4-a- acetoxyazetidin-2-one.
22. 1- a-(Benzyloxcarbonyl)-4-benzyloxbenzyl]-3(3-amino-4a-acetoxyazetidin-2-one.
23. 1- a- ( Carboxy-4-hydroxybenzyl)-3-(D mandelamido)-4a-acetoxyazetidinon-2- one.
24. 1-[a-Benzyloxycarbonyl)-4-benzyloxybenzyl]-3ss-[2-[4-(3- diphenylmethoxycarbonyl-3-t-butyloxycarbamido-propoxy)phenyl]glyoxylamido]-4aacetoxyazetidin-2-one.
25. 1-[a-(Diphenylmethoxycarbonyl)-4-hydroxybenzylj-3(3-benzamido-4a- acetoxyazetidin-2-one.
26. 1-[a-(Diphenylmethoxycarbonyl)-4-hydroxybenzyl]-313-amino-4a-acetoxyazetidin- 2-one.
27. 1-[a-(Carboxy)-4-hydroxybenzyl]-3ss-[2-[4-(3-carboxy-3-aminopropoxy)phenyl]-2- hydroxyiminoacetamido]-4o-acetoxyazetidin-2-one.
28. 1-[a-Diphenylmethoxycarbonyl)-4-hydroxybenzyl -3ss-[2-[4-(3- diphenylmethoxycarbonyl-3-t-butyloxy-carbamidopropoxy p henyl-2-(4 methoxybenzyloxy)iminoacetamido]-4a-acetoxyazetidin-2-one .
29. A process for preparing a 4a-acetoxyazetidin-2-one compound of formula I as defined in any one of claims 1 to 28 which comprises heating a thiazolidine azetidinone compound of formula

wherein Ra is C1,-C3 alkyl, phenyl, benzyl or phenoxymethyl; and R1, a and a' are as defined in Claim 1; with mercuric acetate in the presence of acetic acid to form a N-propenyl 4aacetoxyazetidin-2-one amide of the formula

wherein Ra, R1, a and a' are as defined above; hydrolyzing the 4a-acetoxyazetidin-2-one amide to form a 4a-acetoxy-azetidin-2-one of the formula

wherein Ra, Rl, a and a' are as defined above; if desired cleaving by conventional methods the 3-position acyl group to provide a compound of formula I wherein R is amino; if desired reacylating the 3-amino-4a-azetidin2-one compound so obtained by conventional methods; and optionally removing the carboxy, hydroxy or amino protecting groups.
30. The process of claim 29 wherein the thiazolidine azetidinone is heated at a temperature of from 25 to 75"C.
31. The process of claim 29 or 30 wherein the thiazolidine azetidinorte is heated with' between 1.5 and 2.0 moles of mercuric acetate per mole of said- thiazolidine azetidinone.
32. The process of any of claims 29 to 31 wherein the N-propenyl 4å-acetoxyazetidin-2- one amide is hydrolyzed with mercuric acetate in an aqueous solvent.
33. The process of claim 29 for preparing 1-[a-(benzyloxycarbonyl)-4- benzyloxybenzyl]-3(3-benzamido-4a-'acetoxyazetidin-2-one which comprises heating 2 benzoyl-3,3-dimethyl-7-oxo-α-(4-benzyloxyphenyl)-4-thia-2,6-diazabicyclo[3.2.0]heptane- 6-acetic acid benzyl ester with mercuric acetate in the presence of acetic acid; followed by hydrolysis with aqueous hydrochloric acid.
34. The process of claim 29 for preparing 1-[a-(benzyloxycarbonyl)-4 benzyloxybenzyl]-3ss-phenoxyacetamido-4a-acetoxyazetidin-2-one which comprises heating 2-phenoxy-acetyl-3,3-dimethyl-7-oxo-α-(4-benzyloxyphenyl)-4-thia-2,6- diazabicyclo[3.2.0]heptane-6-acetic acid-benzyl ester with mercuric acetate in the presence of acetic acid; followed by hydrolysis with aqueous hydrochloric acid.
35. The process of claim 29 for preparing 1-[a-(benzyloxycarbonyl)-4 benzyloxybenzyl]-3ss-amino-4a-acetoxyazetidin-2-one which comprises heating 2-benzoyl 3 ,3-dimethyl-7-oxo-a-(4-benzyloxyphenyl)-4-thia-2,6-diazabicyclo[3 .2. 0]heptane-6-acetic acid benzyl ester with mercuric acetate in the presence of the acetic acid; followed by hydrolysis with aqueous hydrochloric acid; and reacting the resulting 3ss-benzamido-4α- acetoxyazetidin-2-one with phosphorous pentachloride in pyridine followed by hydrolysis.
36. The process of claim 29 for preparing 1-[α-(carboxy)-4-hydroxybenzyl]-3ss-(D- mandelamido)-4a-acetoxyazetidin-2-one which comprises heating 2-benzoyl-3,3-dimethyl 7-oxo-α-(4-benzyloxyphenyl)-4-thia-2,6-diazabicyclo[3.2.0]heptane-6-acetic acid pnitrobenzyl ester with mercuric acetate in the presence of acetic acid; followed by hydrolysis with aqueous hydrochloric acid; reacting the resulting 3ss-benzamido-4a-acetoxyazetidin-2- one with phosphorous pentachloride in pyridine followed by hydrolysis; reacting the 3ss-amino-4a-acetoxyazetidin-2-one so obtained with O-formyl mandeloyl chloride; and removing the carboxy and hydroxy protecting groups.
37. The process of claim 29 for preparing 1-[a-(benzyloxycarbonyl)-4 benzyloxybenzyl]-3ss-[2-[4-(3-diphenyl-methoxycarbonyl-3-t- butyloxycarbamidopropoxy)phenyl]-glyoxylamido]-4α-acetoxyazetidin-2-one which comprises heating 2-benzoyl-3,3-dimethyl-7-oxo-α-(4-benzyloxyphenyl)-4-thia-2,6- diazabicyclo[3,2.0]heptane-6-acetic acid benzyl ester with mercuric acetate in the presence of acetic acid; followed by hydrolysis with aqueous hydrochloric acid; reacting the resulting 3ss-benzamido-4α-acetoxyazetidin-2-one with phosphorous pentachloride followed by hydrolysis; and reacting the 3ss-amino-4a-acetoxyazetidinon-2-one so obtained with 4-(3-diphenylmethoxycarbonyl-3-t-butyloxy-carbamidopropoxy)phenylglyoxylic acid.
38. The process of claim 29 for preparing 1-[a-(diphenylmethoxycarbonyl)-4 hydroxybenzyl]-3ss-benzamido-4a-acetoxyazetidin-2-one which comprises heating 2 benzoyl-3 ,3-dimethyl-7-oxo-a-(4-hydroxyphenyl)-4-thia-2 ,6-diazabicyclo[3 .2 .0]heptane-6- acetic acid diphenylmethyl ester with mercuric acetate in the presence of acetic acid; followed by hydrolysis with aqueous mercuric acetate.
39. The process of claim 29 for preparing 1-[a-(diphenylmethoxycarbonyl)-4- hydroxybenzyl]-3ss-amino-4a-acetoxyazetidin-2-one which comprises heating 2-benzoyl 3 ,3-dimethyl-7-oxo-a- (4-hydroxyphenyl) -4-thia-2 ,6-diazabicyclo [3.2. 0]heptane-6-acetic acid diphenylmethyl ester with mercuric acetate in the presence of acetic acid; followed by hydrolysis with aqueous mercuric acetate; and reacting the resulting 3ss-benzamido-4a- acetoxy-azetidin-2-one with phosphorous pentachloride in pyridine followed by hydrolysis.
40. The process of claim 29 for prep aring 1-[α-(carboxy)-4-hydroxybenzyl]-3B- preparing carboxy-3-amino-propoxy)phenyl] -2-hydroxyiminoacetamido] -4a-acetoxyazetidin-2-one which comprises heating 2-benzoyl-3 ,3-dimethyl-7-oxo-a-(4-hydroxyphenyl)-4-thia-2,6- diazabicyclot3.2.0]heptane-6-acetic acid diphenylmethyl ester with mercuric acetate in the presence of acetic acid; followed by hydrolysis with aqueous mercuric acetate; reacting the resulting 3ss-benzamido-4α-acetoxyazetidin-2-one with phosphorous pentachloride in pyridine followed by hydrolysis; reacting the 3ss-amino-4a-acetoxyazetidin-2-one so obtained with 4-(3-diphenylmethoxycarbonyl-3- (t-butyloxycarbamido)-propoxy)phenylglyoxylic acid O-(4-methoxybenzyl)oxime; and removing the carboxy, hydroxy and amino protecting groups.
41. A process as claimed in claim 29 substantially as hereinbefore described with particular reference to any one of Examples 1 to 7.
42. A compound as claimed in claim 1 substantially as hereinbefore described with particular reference to any one of Examples 1 to 7.
43. A compound according to Claim 1 whenever prepared by a process according to any one of Claims 29 to 41.
44. A pharmaceutical formulation comprising a compound as defined in any one of Claims 1 to 28, 42 and 43 wherein R1, Rl, Rb and Zl are hydrogen, a and al are other than protected hydroxy, protected amino or protected aminomethyl and Q is other than a protected moiety; or a pharmaceutically acceptable non-toxic salt thereof; associated with a pharmaceutically acceptable carrier therefor.
45. A method of making a pharmaceutical formulation comprising bringing a compound as defined in one of Claims 1 to 28, 42 and 43 wherein R1, Ra, Rb and Z' are hydrogen, a and a' are other than protected hydroxy, protected amino or protected aminomethyl and Q is other than a protected moiety; or a pharmaceutically acceptable non-toxic salt thereof; into associated with a pharmaceutically acceptable carrier therefor.