1-Oxadethiacepham Compounds and Process for Producing Said Compounds

This invention relates to novel 1-dethia-1-oxacepham compounds. More specifically, it relates to Compounds I represented by the formula I given below, processes for preparing the same, and the use of Compounds I as new intermediates for preparing potent known antibacterials, 1-dethia-1-oxacephalosporins.

Antibacterial 1-dethia-1-oxacephalosporins of the following formula are described by Christensen in the Journal of American Chemical Society, 96, 7582 (1974): and by several firms in their patent publications. ##STR6## (X is hydrogen, acetoxy, or methyltetrazolylthio).

They have been prepared as following schemes by several synthetic routes. But, because the reaction proceeds through an intermediary carbonium ion at position 4 of the azetidinone, the introduction of the oxygen function there results in epimeric mixture. This mixture gives about a half of ineffective 6-epimer of desired 1-dethia-1-oxacephalosporin. ##STR7## (wherein

A is amino or substituted amino;

COB is carboxy or protected carboxy;

X is hydrogen or nucleophilic group;

Ph is phenyl; and

R' is aryl or alkyl.)

The first gist of this invention is based on the discovery that the starting material II, vide infra, cyclizes by the attack of oxygen from the reverse side of the ring juncture and results in favorable stereospecific formation of the carbon to oxygen bond. The formed .alpha.-RCONH group can be replaced by .beta.-RCONH by introduction of methoxy at position 7.alpha. or through a Schiff base formation, epimerization and hydrolysis, finally giving the desired 1-dethia-1-oxacephalosporin having favorable stereochemistry. Other aspects of this invention are the synthetic processes represented by either one of the following reaction schemes (1) through (5) and intermediate compounds I given in item (6) below: ##STR8## and

(5) Other modifications on the molecule

In the above reaction schemes:

A is amino or substituted amino;

E is hydrogen or methoxy;

Y is a divalent group of the following formula: ##STR9##

R is a monovalent group (minus the carbonyl function) of an acyl group derived from a carboxylic or carbonic acid;

Y.sup.1 is a divalent group Y or ##STR10##

COB is carboxy or protected carboxy;

X is a hydrogen or a nucleophilic group; and

Z is a leaving group.

(6) The compounds of the following formula: ##STR11## wherein A, E and Y are as defined above.

I. COMPOUNDS

The substances provided by this invention are Compounds I represented by the following formula I: ##STR12## wherein

A is amino or substituted amino;

E is .beta. hydrogen or .alpha.-methoxy; and

Y is a divalent group of the following formula: ##STR13## in which

COB is carboxy or protected carboxy;

X is hydrogen or a nucleophilic group; and

Z is a leaving group.

The amino substituent of the substituted amino group for A can be selected from known side chains of natural or synthetic penicillins or cephalosporins, or their equivalents (e.g. acyl, hydrocarbyl, hydrocarbylidene, organic silyl or sulfenyl groups, or similar amino substituent which are conventional in the field of cephalosporin or penicillin chemistry). There is a wide variation of possible groups A since they generally have little direct relationship to modification of the substituents at other parts of the nucleus.

Said acyl may contain up to 20 carbon atoms and include the following typical examples:

(1) C.sub.1 to C.sub.10 alkanoyl e.g. formyl, acetyl, propionyl, butyryl, isobutyryl, cyclopropylacetyl, trimethylacetyl, valeryl, t-butylacetyl, caproyl, octanoyl, cyclohexylacetyl, decanoyl, 2-ethylenanthoyl, or like alkanoyl;

(2) C.sub.1 to C.sub.7 haloalkanoyl e.g. chloroacetyl, chloropropionyl, chloroisovaleryl, dichloroacetyl, trichloroacetyl, trichloropropionyl, bromoacetyl, bromopropionyl, dibromocyclohexylcarbonyl, or the like haloalkanoyl;

(3) azidoacetyl, cyanoacetyl, trifluoromethylthioacetyl, cyanomethylthioacetyl, or (4-pyridon-1-yl)acetyl;

(4) acyl groups of the following formula:

wherein Ar is an aryl e.g. furyl, thienyl, pyrrolyl, oxazolyl, isoxazolyl, oxadiazolyl, oxatriazolyl, thiazolyl, isothiazolyl, thiadiazolyl, thiatriazolyl, pyrazolyl, imidazolyl, triazolyl, tetrazolyl, phenyl, pyridyl, pyrimidyl, pyrazinyl, pyridazinyl, triazinyl, dihydrophenyl, tetrahydrophenyl, tetrahydropyrimidyl, naphthyl, benzothiazolyl, indolyl, quinolyl, isoquinolyl, benzopyrimidyl, cinnolinyl, pyridopyrimidyl, indanyl, or the like aryl, and each is unsubstituted or substituted by a substituent e.g. methyl, ethyl, propyl, hydroxymethyl, chloromethyl, trifluoromethyl, cyano, carboxy, carboxymethyl, aminomethyl, phenyl, chlorophenyl, fluorophenyl, amino, formylamino, acetamido, propionamido, butyrylamino, valeramido, isovaleramido, imino, nitro, hydroxy, methoxy, ethoxy, propoxy, methylenedioxy, ethylenedioxy, formyloxy, acetoxy, propionyloxy, butyryloxy, valeryloxy, phenylacetoxy, benzoyloxy, methanesulfonyloxy, ethanesulfonyloxy, benzenesulfonyloxy, bromobenzenesulfonyloxy, methoxycarbonyloxy, ethoxycarbonyloxy t-butoxycarbonyloxy, benzyloxycarbonyloxy, carbamoyloxy, methylcarbamoyloxy, oxo, chloro, bromo, iodo, or the like substituent;

(5) acyl group of the following formula:

wherein Ar is as defined above and Q and Q' each is hydrogen or methyl;

(6) acyl group of the following formula:

wherein Ar, Q, and Q' are as defined above and G is oxygen, sulfur, or imino;

(7) acyl group of the following formula: ##STR14## wherein Ar is as defined above and T.sup.1 is hydrogen or C.sub.1 to C.sub.6 alkyl e.g. methyl, ethyl, propyl, isopropyl, butyl, isobutyl, secondary butyl, tertiary butyl, pentyl, isoamyl, t-pentyl, neopentyl, propylethyl, isopropylethyl, or cyclopentyl;

(8) acyl group of the following formula: ##STR15## wherein Ar is as defined above and T.sup.2 is one of (i), (ii), (iii) or (iv) below:

(i) hydroxy or C.sub.1 to C.sub.10 acyloxy e.g. formylxoy, acetoxy, propionyloxy, butyryloxy, valeryloxy, cyclopropylacetoxy, cyclopentylpropionyloxy, phenylacetoxy, thienylacetoxy, phenoxyacetoxy, glycolyloxy, glyoxalyloxy, glycyloxy, chloroacetoxy, bromoacetoxy, trifluoroacetoxy, benzoyloxy, methylbenzoyloxy, dimethylbenzoyloxy, nitrobenzoyloxy, methoxybenzoyloxy, cyanobenzoyloxy, methanesulfonylbenzyloxy, carbamoyloxy, methylcarbamoyloxy, ethylcarbamoyloxy, propylcarbamoyloxy, methoxycarbonyloxy, t-butoxycarbonyloxy, benzyloxycarbonyloxy, methoxybenzyloxycarbonyloxy, nitrobenzyloxycarbonyloxy, or like acyls;

(ii) carboxy or protected carboxy as is given later in the explanation of COB;

(iii) sulfo or C.sub.1 to C.sub.5 alkoxysulfonyl e.g. methoxysulfonyl, ethoxysulfonyl, propoxysulfonyl, butoxysulfonyl, cyclopropylmethoxysulfonyl, pentyloxysulfonyl, or cyclopropylethoxysulfonyl; or

(iv) a group of the following formula: ##STR16## in which W.sup.1 and W.sup.2 each is hydrogen or a C.sub.1 to C.sub.10 amino-substituent, for example, C.sub.2 to C.sub.7 alkoxycarbonyl e.g. methoxycarbonyl, ethoxycarbonyl, isopropoxycarbonyl, t-butoxycarbonyl, pentyloxycarbonyl, or methylhexylcarbonyl; C.sub.3 to C.sub.10 cycloalkyl-C.sub.2 to C.sub.3 alkoxycarbonyl e.g. cyclopropylmethoxycarbonyl, cyclopropylethoxycarbonyl, cyclopentylmethoxycarbonyl, cyclohexylethoxycarbonyl, or cycloheptylmethoxycarbonyl; C.sub.5 to C.sub.8 cycloalkoxycarbonyl e.g. cyclopentylcarbonyl, cyclohexylcarbonyl, cycloheptylcarbonyl, or cyclopropylcarbonyl; C.sub.1 to C.sub.4 -alkylsulfonyl-C.sub.1 to C.sub.4 -alkoxycarbonyl e.g. methanesulfonylethoxycarbonyl, ethanesulfonylethoxycarbonyl, methanesulfonylbutoxycarbonyl, or butanesulfonylbutoxycarbonyl; halo-C.sub.1 to C.sub.3 -alkoxycarbonyl e.g. chloromethoxycarbonyl, chloroethoxycarbonyl, bromoethoxycarbonyl, iodoethoxycarbonyl, dichloroethoxycarbonyl, trichloroethoxycarbonyl, or trichloropropoxycarbonyl; aralkoxycarbonyl e.g. benzyloxycarbonyl, methylbenzyloxycarbonyl, dimethylbenzyloxycarbonyl, aminobenzyloxycarbonyl, acetamidobenzyloxycarbonyl, nitrobenzyloxycarbonyl, methoxybenzyloxycarbonyl, chlorobenzyloxycarbonyl, bromobenzyloxycarbonyl, diphenylmethoxycarbonyl, diphenylethoxycarbonyl, thiazolylmethoxycarbonyl, pyridylmethoxycarbonyl, or other Ar--CH.sub.2 O--CO-- group (in which Ar is as defined above); C.sub.1 to C.sub.10 alkanoyl e.g. formyl, acetyl, propionyl, butyryl, isobutyryl, valeryl, isovaleryl, t-valeryl, hexanoyl, heptanoyl, cyclohexanecarbonyl, octanoyl, cyclopentanepropionyl, or decanoyl; aromatic acyl of the formula Ar--CO-- in which Ar is as given above; or other acyl group including pyronecarbonyl, thiopyronecarbonyl, pyridonecarbonyl, carbamoyl, guanidylcarbonyl, ureidocarbonyl, methylimidazolidonecarbonyl, methanesulfonylimidazolidonecarbonyl, methyldioxopiperazin-1-ylcarbonyl, ethyldioxopiperazin-1-ylcarbonyl, and butyldioxopiperazin-1-ylcarbonyl; ##STR17## combined together show an enamino or equivalent Schiff base group derived from the amine, having amino for T.sup.2 above, and an enolizable carbonyl compound, for example, C.sub.5 to C.sub.10 acetoacetates e.g. methyl, ethyl, propyl, butyl, isobutyl, or pentyl esters of acetoacetic acid, C.sub.5 to C.sub.10 acetoacetamides e.g. amide, methylamide, anilide, or methylanilide of acetoacetic acid, acetylacetone, acetoacetonitrile, .alpha.-acetylbutyrolactone, or 1,3-cyclopentanedione; or ##STR18## combined together show a diacrylamino derived from a C.sub.4 to C.sub.10 dibasic acid e.g. succinimido, maleimido, or phthalimido;

(9) 5-aminoadipoyl; 5-aminoadipoyl protected at the amino group with e.g. C.sub.1 to C.sub.10 alkanoyl, aroyl, aralkanoyl, haloalkanoyl, or alkoxycarbonyl as defined hereinabove; or 5-aminoadipoyl protected at the carboxy group wigh e.g. alkyl, aryl, aralkyl, or alkylsilyl as defined hereinbefore;

or

(10) acyl group of the following formula:

wherein L is an easily removable and optionally substituted C.sub.1 to C.sub.10 hydrocarbyl group e.g. t-butyl, 1,1-dimethylpropyl, cyclopropylmethyl, cyclopropylethyl, 1-methylcyclohexyl, isobornyl, 2-methoxy-t-butyl, 2,2,2-trichloroethyl, benzyl, naphthylmethyl, p-methoxybenzyl, p-nitrobenzyl, or pyridylmethyl.

Alternatively, the amino substituent in the group A can be a diacyl group derived from a C.sub.4 to C.sub.10 polybasic carboxylic acid e.g. succinyl, maleoyl, phthaloyl, or pyridine-2,3-dicarbonyl.

Other possible amino substituents in the group A can be a C.sub.1 to C.sub.20 optionally substituted hydrocarbyl e.g. methyl, ethyl, t-butyl, trityl, methylidene, benzylidene, hydroxybenzylidene, .alpha.-halobenzylidene, .alpha.-methoxybenzylidene, .alpha.-ethoxybenzylidene, 1-methoxy-2-phenylethylidene, 3,5-di-t-butyl-4-hydroxybenzylidene, or o-hydroxybenzylidene; C.sub.3 to C.sub.10 organic silyl e.g. trimethylsilyl, dimethylmethoxysilyl, chlorodimethylsilyl, methyldimethoxysilyl, or methyl ethylenedioxysilyl; or C.sub.1 to C.sub.10 sulfenyl e.g. methylthio, phenylthio, or o-nitrophenylthio.

Groups convertible into amino or amido e.g. anamino, amido, azido, isocyanato or isocyano are also included in the scope of group A.

Included in the said definition, the group A can be a cyclic group e.g. 4-phenyl-2,2-dimethyl-5-oxoimidazolidin-1-yl, 4-p-hydroxyphenyl-2,2,-dimethyl-3-nitroso-5-oxoimidazolidin-1-yl, 4-p-hydroxyphenyl-2-phenyl-5-oxoimidazolidin-1-yl, or 4-thienyl-5-oxoimidazolidin-1-yl.

The said group A, where possible, can be interrupted by a hetero atom in the skeleton or can be unsaturated, or can be substituted by, for example, halogen e.g. fluorine, chlorine, or bromine; a nitrogen function e.g. amino, hydrazinyl, azido, alkylamino, arylamino, acylamino, alkylideneamino, acylimino, imino, or nitro; oxygen function e.g. hydroxy, alkoxy, aralkoxy, aryloxy, acyloxy, or oxo; sulfur function e.g. mercapto, alkylthio, aralkylthio, arylthio, acylthio, thioxo, sulfo, sulfonyl, sulfinyl, alkoxysulfonyl, or aryloxysulfinyl; carbon function e.g. alkyl, alkenyl, aralkyl, aryl, carboxy, carbalkoxy, carbamoyl, alkanoyl, aroyl, aminoalkyl, aralkanoyl, or cyano; or phosphorus function e.g. phospho or phosphoroyl.

The group B is hydroxy when the group COB is a carboxy group.

Alternatively, the group B can be a carboxy-protecting group. Thus the group B can be an oxygen function, for example,

C.sub.1 to C.sub.10 alkoxy e.g. methoxy, ethoxy, propoxy, isopropoxy, butoxy, t-butoxy, monohydroxy-t-butoxy, methoxy-t-butoxy, cyclopropylmethoxy, pentyloxy, isopentyloxy, cyclopropylethoxy, cyclopentyloxy, hexyloxy, cyclohexyloxy, octyloxy, or decyloxy;

C.sub.1 to C.sub.6 haloalkoxy e.g. chloromethoxy, chloroethoxy, bromoethoxy, iodoethoxy, dichloropropoxy, trichloroethoxy, trichlorobutoxy, or dibromocyclohexyloxy;

C.sub.3 to C.sub.10 acylalkoxy e.g. acetonyloxy, acetylethoxy, propionylmethoxy, phenacyloxy, chlorophenacyloxy, bromophenacyloxy, nitrophenacyloxy, or methylphenacyloxy;

C.sub.3 to C.sub.10 alkoxyalkoxy e.g. methoxymethoxy, ethoxymethoxy, chloroethoxymethoxy, propoxyethoxy, butoxyethoxy, cyclohexyloxyethoxy, methoxyethoxymethoxy, butoxyethoxymethoxy, or octyloxyethoxy;

C.sub.2 to C.sub.10 aminoalkoxy e.g. aminomethoxy, aminoethoxy, dimethylaminoethoxy, or ethylaminomethoxy; aryloxy e.g. phenoxy, chlorophenoxy, nitrophenoxy, naphthyloxy, pyridyloxy, indolyloxy, indanyloxy, or pentachlorophenoxy; aralkoxy e.g. benzyloxy, methylbenzyloxy, xylylmethoxy, chlorobenzyloxy, bromobenzyloxy, methoxybenzyloxy, ethoxybenzyloxy, nitrobenzyloxy, dibromobenzyloxy, phenethyloxy, phthalidyloxy, p-hydroxy-di-t-butylbenzyloxy, diphenylmethoxy, or trityloxy;

C.sub.1 to C.sub.10 alkylsilyloxy e.g. trimethylsilyloxy, dimethylmethoxysilyloxy, chlorodimethylsilyloxy, or ethylenedioxymethylsilyloxy; or

C.sub.1 to C.sub.10 alkylstannyloxy e.g. trimethylstannyloxy; to form an ester group;

C.sub.1 to C.sub.10 organic or inorganic acyloxy e.g. acetoxy, propionyloxy, sulfonyloxy, sulfooxy, or chloratooxy; to form an anhydride group; or

metaloxy of a group I, II, or III metal in the periodical table e.g. lithiooxy, sodio-oxy, potassio-oxy, or magnesiooxy, or C.sub.1 to C.sub.15 hydrocarbylammoniooxy e.g. triethylammoniooxy, dicyclohexylammonio-oxy to form a salt group; a sulfur function, for example, C.sub.1 to C.sub.10 hydrocarbylthio or mercapto to form a thiol ester or thiocarboxylic acid group; a nitrogen function, for example,

C.sub.1 to C.sub.5 alkylamino e.g. methylamino, ethylamino, propylamino, butyramino, or pentylamino; or

di-C.sub.1 to C.sub.5 -alkylamino e.g. dimethylamino, diethylamino, piperidyl, morpholin-1-yl, or methylmorpholin-1-yl to form an amide group; or

hydrazinyl or azido group to form hydrazide or azide group.

Usually, the carboxy-protecting groups are removed during the synthesis to give the final objective compounds and wide variety of structure is feasible without affecting the final product and departing from this invention.

The nucleophilic group X can be every possible group being introduced at the methylene attached to the position 3 of cephem ring in place of the acetoxy group of cephalosporanic acid.

Typical examples of X include halo e.g. chloro or bromo; oxygen functions, for example, hydroxy, C.sub.1 to C.sub.4 alkanoyloxy e.g. formyloxy, acetoxy, propionyloxy, or butyryloxy; substituted C.sub.1 to C.sub.4 alkanoyloxy e.g. malonyloxy, succinoyloxy, cyanoacetoxy, glycyloxy, alanyloxy, glycolyloxy, glyoxylyloxy, phenoxyacetoxy, sulfopropionyloxy, chloroacetoxy, dichloroacetoxy, or trifluoroacetoxy; aroyloxy e.g. benzoyloxy or naphthoyloxy; carbonic acyloxy e.g. chloroformyloxy, methoxyformyloxy, trichloroethoxyformyloxy, cyclopropylmethoxyformyloxy, or methanesulfonylethoxyformyloxy; C.sub.1 to C.sub.6 alkoxy e.g. methoxy, ethoxy, butoxy, sec-butoxy, cyclopropylmethoxy, or cyclohexyloxy; aralkoxy of the formula Ar--CH.sub.2 O-- (in which Ar is as defined above) e.g. benzyloxy, furfuryloxy, or naphthylmethoxy; aryloxy of the formula Ar--O-- (in which Ar is as given above) e.g. phenoxy, naphthyloxy, or indanyloxy; sulfur functions, for example, mercapto, C.sub.1 to C.sub.5 alkanoylthio e.g. acetylthio, propionylthio, or butyrylthio; aroylthio e.g. benzoylthio or naphthoylthio; thiocarbamoylthio, methylthiocarbamoylthio; C.sub.1 to C.sub.6 alkylthio e.g. methylthio, ethylthio, propylthio, butylthio, cyclopropylmethylthio, or cyclopropylethylthio; aralkylthio e.g. benzylthio, picolylthio, or phenethylthio; or arylthio of the formula Ar--S-- (in which Ar is as defined above) e.g. phenylthio, triazolylthio, thiadiazolylthio, oxadiazolylthio, or tetrazolylthio, each being unsubstituted or substituted by e.g. methyl, ethyl, hydroxymethyl, hydroxyethyl, carboxyethyl, carboxymethyl, sulfoethyl, dimethylaminoethyl, dimethylaminopentyl, or morpholinoethyl; or nitrogen functions e.g. amino, azido, hydrazinyl, acetylamino, methylamino, pyridinium, picolinium, 4-carboxypyridinium, carbamoylpyridinium, hydroxymethylpyridinium, carboxymethylpyridinium, or chloropyridinium.

Said leaving group Z can be an anionic part of a nucleophilic reagent. Typical examples of them include halo e.g. chloro, bromo, or iodo; hydroxy; or C.sub.1 to C.sub.8 carboxylic acyloxy e.g. acetoxy or trifluoroacetoxy; sulfonic acyloxy e.g. methanesulfonyloxy, ethanesulfonyloxy, toluenesulfonyloxy, or bromobenzenesulfonyloxy, arylthio e.g. phenylthio, arylsulfenyl e.g. phenylsulfenyl, arylselenyl, arylsulfinyl, or alkylsulfinyl.

The leaving group is removed during the synthesis to give the final objective compounds, and wide variety of structure is feasible without affecting on the final product to be produced and without departing from this invention.

When R, COB or Y is likely to be affected from undesirable change during the reaction, it may be protected in advance and deprotected afterwards at an optional stage.

The compounds of this invention are shown by the following formula: ##STR19## wherein

A is amino or substituted amino;

E is hydrogen or methoxy; and

Y is a divalent group of the following formula: ##STR20## in which

COB is carboxy or protected carboxy;

X is hydrogen or nucleophilic group; and

Z is a leaving group.

They include compounds of the following formula: ##STR21## wherein A, E, COB, X, and Z are as defined above.

More specific compounds are those in which A is amino substituted by:

(1) C.sub.1 to C.sub.10 alkanoyl,

(2) C.sub.1 to C.sub.7 haloalkanoyl,

(3) azidoacetyl, cyanoacetyl, trifluoromethylthioacetyl, cyanomethylthioacetyl, or (4-pyridon-1-yl)acetyl;

(4) acyl group of the following formula:

wherein Ar is an aryl selected from furyl, thienyl, pyrrolyl, oxazolyl, isoxazolyl, oxadiazolyl, oxatriazolyl, thiazolyl, isothiazolyl, thiadiazolyl, thiatriazolyl, pyrazolyl, imidazolyl, triazolyl, tetrazolyl, phenyl, pyridyl, pyrimidyl, pyrazinyl, pyridazinyl, triazinyl, dihydrophenyl, tetrahydrophenyl, tetrahydropyrimidyl, naphthyl, benzothiazolyl, indolyl, quinolyl, isoquinolyl, benzopyrimidyl, cinnolinyl, pyridopyrimidyl, or indanyl ring group;

(5) acyl group of the following formula:

wherein Ar is as defined above and Q and Q' each is hydrogen or methyl;

(6) acyl group of the following formula:

wherein Ar, Q, and Q' each is as defined above and G is oxygen, sulfur, or imino;

(7) acyl group of the following formula: ##STR22## wherein Ar is as defined above and T.sup.1 is hydrogen or C.sub.1 to C.sub.6 alkyl;

(8) acyl group of the following formula: ##STR23## wherein Ar is as defined bove and T.sup.2 is one of (i) hydroxy or C.sub.1 to C.sub.10 acyloxy, (ii) carboxy or protected carboxy, (iii) sulfo or C.sub.1 to C.sub.5 alkoxysulfonyl, or a group of the formula: ##STR24## in which W.sup.1 and W.sup.2 each is hydrogen or a C.sub.1 to C.sub.15 amino-substituent;

(9) 5-aminoadipoyl, 5-aminoadipoyl protected at the amino or 5-aminoadipoyl protected at the carboxy;

(10) acyl group of the following formula:

wherein L is an easily removable and unsubstituted or substituted C.sub.1 to C.sub.10 hydrocarbyl group; or

(11) C.sub.1 to C.sub.20 optionally substituted hydrocarbyl, C.sub.3 to C.sub.10 organic silyl, or C.sub.1 to C.sub.10 sulfenyl, the group B in said COB is C.sub.1 to C.sub.10 alkoxy, C.sub.1 to C.sub.6 haloalkoxy, C.sub.3 to C.sub.10 acylalkoxy, C.sub.3 to C.sub.10 alkoxyalkoxy, C.sub.2 to C.sub.10 aminoalkoxy, aryloxy, aralkoxy, C.sub.1 to C.sub.10 alkylsilyloxy, C.sub.1 to C.sub.10 alkylstannyloxy, C.sub.1 to C.sub.10 acyloxy, inorganic acyloxy, metal-oxy of a group I, II, or III metal in the periodical table, C.sub.1 to C.sub.15 hydrocarbylammonio-oxy, C.sub.1 to C.sub.10 hydrocarbylthio, mercapto, C.sub.1 to C.sub.5 alkylamino, di-C.sub.1 to C.sub.5 alkylamino, hydrazinyl, or azido, E is .beta.-hydrogen or .alpha.-methoxy; the group X is halo, hydroxy, C.sub.1 to C.sub.4 alkanoyloxy, substituted C.sub.1 to C.sub.4 alkanoyloxy, aroyloxy, carbonic acyloxy, C.sub.1 to C.sub.6 alkoxy, aralkoxy of the formula Ar--CH.sub.2 O-- or aryloxy of the formula Ar--O-- (in which Ar is as defined above), mercapto, C.sub.1 to C.sub.5 alkanoylthio, aroylthio, C.sub.1 to C.sub.6 alkylthio, aralkylthio of the formula Ar--CH.sub.2 S-- or arylthio of the formula Ar--S-- (in which Ar is as defined above), amino, azido, hydrazinyl, acetylamino, methylamino, pyridinium, picolinium, 4-carboxypyridinium, carbamoylpyridinium, hydroxymethylpyridinium, carboxymethylpyridinium, or chloropyridinium, and the group Z is halo, hydroxy or C.sub.1 to C.sub.8 alkanoyloxy, sulfonyloxy, arylthio, arylsulfenyl, arylselenyl, arylsulfinyl, or alkylsulfinyl.

Further specific compounds (I) have benzoylamino, methylbenzoylamino, chlorobenzoylamino, nitrobenzoylamino, cyanobenzoylamino, phenoxyacetamido, phenylacetamido, diphenylmethoxycarbonylphenylacetamido, or amino for the A group; hydroxy, benzyloxy, tolylmethoxy, chlorobenzyloxy, diphenylmethoxy, naphthylmethoxy, t-butoxy, or trimethylsilyloxy for B in COB; chloro, bromo, hydroxy, acetoxy, methanesulfonyloxy, methylthio, 1-m ethyltetrazol-5-ylthio, or hydrogen for the X group; and chloro, bromo, hydroxy, or acetoxy for the Z group.

Some of the specific compounds I are given below:

(1) Compounds of the following formula: ##STR25## wherein

A=benzoylamino, COB=carboxy, E=.beta.-hydrogen, and X=Z=chloro;

A=benzamido, COB=carboxy, E=.beta.-hydrogen, and X=Z=bromine;

A=benzamido, COB=benzyloxycarbonyl, E=.beta.-hydrogen, and X=Z=chlorine;

A=benzamido, COB=benzyloxycarbonyl, E=.beta.-hydrogen, and X=Z=bromine;

A=benzamido, COB=diphenylmethoxycarbonyl, E=.beta.-hydrogen, and X=hydrogen, and Z=hydroxy;

A=benzamido, COB=diphenylmethoxycarbonyl, E=.beta.-hydrogen, X=hydrogen, and Z=.alpha.-acetoxy;

A=benzamido, COB=diphenylmethoxycarbonyl, E=.beta.-hydrogen, X=hydrogen, and Z=bromine;

A=benzamido, COB=diphenylmethoxycarbonyl, E=.beta.-hydrogen, and X=Z=hydroxy;

A=benzamido, COB=diphenylmethoxycarbonyl, E=.beta.-hydrogen, X=acetoxy, and Z=hydroxy;

A=benzamido, COB=diphenylmethoxycarbonyl, E=.beta.-hydrogen, X=hydroxy, and Z=methanesulfonyloxy,

A=benzamido, COB=diphenylmethoxycarbonyl, E=.beta.-hydrogen, X=chlorine, and Z=hydroxy;

A=benzamido, COB=diphenylmethoxycarbonyl, E=.beta.-hydrogen, and X=Z=chlorine;

A=benzamido, COB=diphenylmethoxycarbonyl, E=.beta.-hydrogen, X=methylthio, and Z=chlorine;

A=benzamido, COB=diphenylmethoxycarbonyl, E=.beta.-hydrogen, X=1-methyltetrazolylthio, and Z=hydroxy;

A=benzamido, COB=diphenylmethoxycarbonyl, E=.beta.-hydrogen, X=1-methyltetrazolylthio, and Z=chlorine;

A=benzamido, COB=diphenylmethoxycarbonyl, E=.beta.-hydrogen, X=bromine, and Z=hydroxy;

A=benzamido, COB=diphenylmethoxycarbonyl, E=.beta.-hydrogen, and X=Z=bromine;

A=p-methylbenzamido, COB=diphenylmethoxycarbonyl, E=.beta.-hydrogen and X=Z=chlorine;

A=p-chlorobenzamido, COB=diphenylmethoxycarbonyl, E=.beta.-hydrogen, and X=Z=chlorine;

A=p-cyanobenzamido, COB=diphenylmethoxycarbonyl, E=.beta.-hydrogen, and X=Z=chlorine,

A=p-nitrobenzamido, COB=diphenylmethoxycarbonyl, E=.beta.-hydrogen, and X=Z=chlorine;

A=phenoxyacetamido, COB=diphenylmethoxycarbonyl, E=.beta.-hydrogen, and X=Z=chlorine;

A=phenylacetamido, COB=t-butoxycarbonyl, E=.beta.-hydrogen, and X=Z=chlorine;

A=phenylacetamido, COB=benzyloxycarbonyl, E=.beta.-hydrogen, and X=Z=chlorine;

A=benzamido, COB=carboxy, E=.alpha.-methoxy, X=hydrogen, and Z=hydroxy;

A=benzamido, COB=carboxy, E=.alpha.-methoxy, X=hydrogen, and Z=acetoxy;

A=benzamido, COB=carboxy, E=.alpha.-methoxy, X=hydrogen, and Z=trifluoroacetoxy;

A=benzamido, COB=benzyloxycarbonyl, E=.alpha.-methoxy, and X=Z=chlorine;

A=benzamido, COB=benzyloxycarbonyl, E=.alpha.-methoxy, and X=Z=bromine;

A=benzamido, COB=diphenylmethoxycarbonyl, E=.alpha.-methoxy, X=hydrogen, and Z=hydroxy;

A=benzamido, COB=diphenylmethoxycarbonyl, E=.alpha.-methoxy, X=hydrogen, and Z=acetoxy;

A=benzamido, COB=diphenylmethoxycarbonyl, E=.alpha.-methoxy, X=hydrogen, and Z=trifluoroacetoxy;

A=benzamido, COB=diphenylmethoxycarbonyl, E=.alpha.-methoxy, and X=Z=chlorine;

A=benzamido, COB=diphenylmethoxycarbonyl, E=.alpha.-methoxy, and X=Z=bromine;

A=p-chlorobenzamido, COB=diphenylmethoxycarbonyl, E=.alpha.-methoxy, X=1-methyltetrazolylthio, and X=chlorine;

A=p-cyanobenzamido, COB=diphenylmethoxycarbonyl, E=.alpha.-methoxy, X=1-methyltetrazolylthio, and Z=chlorine;

A=p-nitrobenzamido, COB=diphenylmethoxycarbonyl, E=.alpha.-methoxy, X=1-methyltetrazolylthio, and X=chlorine;

A=p-methylbenzamido, COB=diphenylmethoxycarbonyl, E=.alpha.-methoxy, X=1-methyltetrazolylthio, and Z=chlorine;

A=p-chlorobenzamido, COB=diphenylmethoxycarbonyl, E=.alpha.-methoxy, and X=Z=chlorine,

A=p-cyanobenzamido, COB=diphenylmethoxycarbonyl, E=.alpha.-methoxy, and X=Z=chlorine,

A=p-nitrobenzamido, COB=diphenylmethoxycarbonyl, E=.alpha.-methoxy, and X=Z=chlorine;

A=p-methylbenzamido, COB=diphenylmethoxycarbonyl, E=.alpha.-methoxy, and X=Z=chlorine;

A=benzamido, COB=p-methylbenzyloxycarbonyl, E=.alpha.-methoxy, X=1-methyltetrazolylthio, and Z=chlorine;

A=benzamido, COB=p-chlorobenzyloxycarbonyl, E=.alpha.-methoxy, X=1-methyltetrazolylthio, and Z=chlorine;

A=benzamido, COB=naphthylmethoxycarbonyl, E=.alpha.-methoxy, X=1-methyltetrazolylthio, and Z=chlorine; or

A=.alpha.-diphenylmethoxycarbonyl-phenylacetamido, COB=diphenylmethoxycarbonyl, E=.alpha.-methoxy, and X=Z=chlorine.

(2) Compounds of the following formula: ##STR26## wherein

A=benzamido, COB=carboxy, E=.beta.-hydrogen;

A=benzamido, COB=diphenylmethoxycarbonyl, and E=.beta.-hydrogen;

A=p-methylbenzamido, COB=diphenylmethoxycarbonyl, and E=.beta.-hydrogen;

A=p-chlorobenzamido, COB=diphenylmethoxycarbonyl, and E=.beta.-hydrogen;

A=p-cyanobenzamido, COB=diphenylmethoxycarbonyl, and E=.beta.-hydrogen;

A=p-nitrobenzamido, COB=diphenylmethoxycarbonyl, and E=.beta.-hydrogen;

A=benzamido, COB=benzyloxycarbonyl, and E=.beta.-hydrogen;

A=phenoxyacetamido, COB=diphenylmethoxycarbonyl, and E=.beta.-hydrogen;

A=phenylacetamido, COB=t-butoxycarbonyl, and E=.beta.-hydrogen;

A=phenylacetamido, COB=benzyloxycarbonyl, and E=.beta.-hydrogen;

A=phenylacetamido, COB=diphenylmethoxycarbonyl, and E=.beta.-hydrogen;

A=amino, COB=diphenylmethoxycarbonyl, and E=.beta.-hydrogen;

A=benzamido, COB=diphenylmethoxycarbonyl, and E=.alpha.-methoxy;

A=phenylacetamide, COB=benzyloxycarbonyl, and E=.alpha.-methoxy;

A=amino, COB=diphenylmethoxycarbonyl, and E=.alpha.-methoxy; or

A=amino, COB=benzyloxycarbonyl, and E=.alpha.-methoxy.

(3) Compounds of the following formula: ##STR27## wherein

A=benzamido, COB=diphenylmethoxycarbonyl, and E=.beta.-hydrogen.

(4) Compounds of the following formula: ##STR28## wherein A=benzamido, COB=diphenylmethoxycarbonyl, E=.beta.-hydrogen, and X=hydrogen.

Compounds I can be used as starting materials for making known antibacterials e.g. 1-dethia-1-oxacephalosporins (Japanese Patent Publication (Unexamined) Nos. 49-133,594 and 51-149,295) in high yield by introducing or migrating a double bond to position 3, replacing A with an antibacterially preferable side chain, and/or deprotecting the protected carboxy in COB, if required after introduction of antibacterially suitable X at the methylene bound to position 3 of 1-dethia-1-oxacephem nucleus. Of course, said double bond, A, COB, and X may be replaced by antibacterially suitable ones prior to forming desired cephem ring system. Choice of said groups A, COB, and X in the starting materials and the intermediates depends mainly on easiness of reactions, stability under reaction conditions, and on the factors of waste, costs, or other practical and technical factors.

Compounds (1) can be, for example, subjected to (a) HZ-elimination to give a 1-dethia-1-oxacephalosporin (4) which can also be prepared by (b) double bond migration of Compound (2) with a base (e.g. triethylamine) at 0.degree. C. to 70.degree. C. for 5 hours to 3 days or by (c) cyclization of Compound (3) with a Lewis acid (e.g. boron trifluoride) at 0.degree. C. to 50.degree. C. for 0.1 to 1 hour. All of the processes (a), (b), and (c) can be effected under conditions analogous to the corresponding treatments given later in relation to the compounds of this invention. Some of illustrative examples are given below in the working examples. ##STR29## (wherein

A, COB, X and Z are as given above and

R means a group of acyl (minus the carbonyl function) when A is an .alpha.-amino function represented by RCONH). Compounds I (A=7.beta.-amido; COB.dbd.COOH) or pharmaceutically acceptable salts thereof are moderately active antibacterials. They can be injected with a conventional carrier to a patient suffering from bacterial infection caused by sensitive gram positive bacteria (e.g. Streptococcus pyogenes) or gram negative bacteria (e.g. Escherichia coli) at a dose of 0.1 to 10 g per day.

The said Compounds I are prepared in several synthetic routes as given below with reaction scheme: ##STR30## and

(5) Other modification on the molecule. In these reaction schemes, R, Y.sup.1, A, E, COB, X and Z are as defined hereinbefore.

Detailed explanation of these processes are given below.

(1) Cyclization

Compounds Ia (wherein A is an .alpha.-RCONH and E is .beta.-hydrogen) are preparable from the correspounding Oxazolinoazetidine II under the action of an acid according to the following reaction scheme: ##STR31## In the above formulas R is a monovalent group (minus the carbonyl function) from an acyl derived from a carboxylic or carbonic acid;

Y.sup.1 is a divalent group of the following formula: ##STR32## (in which

COB is carboxy or protected carboxy;

X is hydrogen or a nucleophilic group; and

Z is a leaving group.

The group R correspounds to the monovalent group of acyl (minus the carbonyl function) derived from carboxylic or carbonic acyls as defined in the Section I Compounds.

Compounds Ia may be prepared from the correspounding Oxazolinoazetidines II by treating with an acid. Typical examples of the acid include mineral acids (e.g. HCl, HBr, HNO.sub.3, H.sub.2 SO.sub.4, or H.sub.3 PO.sub.4), sulfonic acids (e.g. CH.sub.3 SO.sub.3 H, C.sub.2 H.sub.5 SO.sub.3 H, C.sub.6 H.sub.5 SO.sub.3 H, CH.sub.3 C.sub.6 H.sub.4 SO.sub.3 H, BrC.sub.6 H.sub.4 SO.sub.3 H, CF.sub.3 SO.sub.3 H, or naphthalenesulfonic acid) strong carboxylic acids (e.g. Cl.sub.3 CCOOH, CF.sub.3 COOH), Lewis acids (e.g. BF.sub.3, ZnCl.sub.2, SnCl.sub.2, SnCl.sub.4, SnBr.sub.2, SbCl.sub.3, SbCl.sub.5, or TiCl.sub.3), and similar acids.

The reaction is complete usually within 5 minutes to 10 hours, often 15 minutes to 3 hours at -30.degree. C. to +50.degree. C., especially at 15.degree. C. to 30.degree. C., to give Compounds Ia in high yield. If required, the reaction can be carried out with stirring or under an inert gas (e.g. nitrogen, argon, carbon dioxide) atmosphere.

The reaction is generally carried out in an inert solvent. Typical inert solvents include hydrocarbons (e.g. hexane, cyclohexane, benzene, toluene), halohydrocarbons (e.g. methylene chloride, chloroform, dichloroethane, carbon tetrachloride, chlorobenzene), ethers (e.g. diethyl ether, diisobutyl ether, dioxane, tetrahydrofuran), esters (e.g. ethyl acetate, butyl acetate, methyl benzoate), ketones (e.g. acetone, methyl ethyl ketone, cyclohexanone), sulfoxides (e.g. dimethyl sulfoxide), nitriles (e.g. acetonitrile, benzonitrile), and like solvents and mixtures thereof. Solvents having hydroxy function may react with the starting materials II to give by-products, but they also are available under controlled reaction conditions. Typical examples of such hydroxy-solvents are water, alcohols (e.g. methanol, ethanol, t-butanol, benzyl alcohols), acids (e.g. formic acid, acetic acid, propionic acid), and mixtures thereof.

The terminal hydroxy linked to Y.sup.1 on Oxazolinoazetidine II may be protected in advance by a hydroxy-protecting group (e.g. formyl, tetrahydropyranyl, or the like) readily removable under the reaction conditions.

Occasionally, double bond migration, introduction of a nucleophile, elimination or like side reaction takes place during the reaction, but the side reactions can be also used intentionally for better procedures to be included in this invention.

In a typical example, an Oxazolinoazetidine II (one part) is dissolved in a mixture of 5 to 10 parts of halohydrocarbon (e.g. chloroform, dichloromethane), and 0 to 10 parts of ether solvent (e.g. ether, dioxane), mixed with 1 to 0.001 molar equivalent of an acid (e.g. boron trifluoride etherate, toluenesulfonic acid, copper sulfate, zinc chloride, stannic chloride), and the solution is kept at 10.degree. to 60.degree. C. for 0.5 to 10 hours to give the correspounding Compound Ia in about 50 to 95% yield.

Said Oxazolinoazetidines II are prepared from 6-epi-penicillin 1-oxides, e.g. according to the following reaction sequences: ##STR33## (wherein R, COB, and X are as defined above)

(2) Methoxylation

Transformation of said group E from hydrogen to methoxy in compounds Ia can be done stepwise as follows: at first, the part --NH-- in the side chain A is oxidized to form an imino --N.dbd. on the corner at position 7, then equimolar methanol is added to the imino to reform another --NH-- linkage and a methoxy in place of the original hydrogen.

When the A group is amino or amido, starting Compound Ia is treated with an N-halogenating reagent, subjected to hydrogen halide elimination with a base to give corresponding imino compound, and then treated with methanol to give the objective Compound Ia (where E is .alpha.-methoxy). By such an N-halogenation, other part of the molecule may be partially halogenated, but the over-halogenated product may be reduced to remove excessively introduced halogen atom. The procedures may be one of the followings:

(1) reaction of amine or amide with an N-halogenating reagent (e.g. molecular halogen, t-butyl hypochlorite), followed by the action of alkali metal methoxide (e.g. lithium methylate, sodium methylate, potassium methylate) or alkaline earth metal methoxide [e.g. Mg (OCH.sub.3).sub.2, Ca(OCH.sub.3).sub.2, Ba(OCH.sub.3).sub.2 or like base] in methanol;

(2) reaction with t-butyl hypohalite and methanol in the presence of a base and phenyllithium, if required, with an additional solvent (e.g. tetrahydrofuran);

(3) the reaction with t-butyl hypohalite in the presence of sodium borate in methanol, and when an over-halogenated product if partially formed, the product is subjected to reduction with zinc, phosphite, or the like; and

(4) successive treatments with bromine-DBU, phosphorus pentachloride pyridine, base, methanolic base, and trialkylsilyl chloride or tetraalkylammonium chloride.

Alternatively, Compounds Ia (E.dbd.H, A.dbd.NH.sub.2) can be treated with a suitable aldehyde (e.g. benzaldehyde, p-hydroxybenzaldehyde, 3,5-di-t-butyl-4-hydroxybenzaldehyde) to form a Schiff base, oxidized to give an imino compound, treated with methanol, and then hydrolyzed to give other Compounds Ia (E.dbd.OCH.sub.3, A.dbd.NH.sub.2).

In a typical example, 1 part of the amide Ia is dissolved in 10 to 50 parts of an inert solvent (e.g. dichloromethane, dioxan, ether, dipropyl ether, tetrahydrofuran), stirred with 1 to 5 mole equivalents of N-halogenating reagent (e.g. molecular halogen in carbon tetrachloride or t-butyl hypochlorite) for 2 to 10 minutes at -70.degree. C. to -10.degree. C., mixed with 1 to 4 equivalents of a metal methoxide (e.g. lithium methoxide, magnesium methoxide) in methanol, and stirred at -50.degree. C. to 0.degree. C. for 5 to 70 minutes. The reaction mixture is neutralized with acetic acid or mineral acid, and the product is extracted with an organic solvent. Such a treatment gives usually up to 95% yield of objective compound Ia (E.dbd.OCH.sub.3).

(3) Addition

A compound I having an exomethylene group at position 3 reacts with an addition reagent XZ (e.g. molecular halogen, peracid, peroxide, hypohalite salt, hypohalite ester, heavy metal peroxide such as osmium tetroxide, sulfenyl halide) in an inert solvent (e.g. hydrocarbon, halohydrocarbon, ether, ester, or like solvents) to give Compounds I where Y is a divalent group of the formula: ##STR34## (in which COB, X, and Z are as defined above).

The addition may be accomplished smoothly even at low temperature of -70.degree. C. to 0.degree. C. for 5 minutes to 10 hours in an inert solvent (especially halohydrocarbon and ether solvents) giving up to 90% yield of the addition product owing to high reactivity of exomethylene-double bond at position 3. When the reagent is a molecular halogen, the halogenation can be accelerated under the irradiation of light or the addition of a catalyst (e.g. Cu, Cu.sub.2 S, Cu.sub.2 Cl.sub.2, Ph.sub.3 PO) to give a higher addition yield.

(4) Elimination to give 1-dethia-1-oxacephlosporins

This step is carried out by removing Z from the starting compound I along with a neighbouring hydrogen to give .DELTA..sup.2 - or .DELTA..sup.3 -cephem compounds. The double bond formation depends on the location of the eliminated hydrogen, but the isomerism may be also a result of migration of formerly formed double bond under the reaction condition or during work-up.

When the reactivity of Z is high enough, HZ is easily eliminated without any other reagent e.g. by keeping the Compund I at an elevated temperature.

When Z is halo (e.g. chloro, bromo, iodo) or acyloxy (e.g. mineral acid acyloxy, optionally substituted alkanoyloxy, carbamoyloxy, sulfonyloxy, phosphoryloxy), the elimination is accelerated by addition of an acid-acceptor (e.g. aliphatic amine, aromatic base; salt of weak organic acid and strong base; alkali metal hydroxide, bicarbonate, carbonate, mercaptide, or alcoholate; alkaline earth metal oxide, hydroxide, hydrogencarbonate, or carbonate; alumina, silica gel).

When Z is hydroxy, the elimination is accelerated by addition of a dehydrating reagent (e.g. phosphorus pentoxide, mineral acid, Lewis acid, strong carboxylic acid, aliphatic or aromatic sulfonic acid or phosphonic acid, inorganic or organic base, alumina, silica gel, amide), halogenating reagent (e.g. phosphorus pentahalide, phosphorus trihalide, phosphorus oxyhalide, thionyl halide, sulfuryl hlide), acylating reagent (e.g. acid anhydride, acid halide, acid isocyanide) or like reagent, if required in the presence of an acid-acceptor (e.g. said acid acceptor given above).

The reaction can be carried out at -50.degree. C. to 100.degree. C. with stirring under inert gas (e.g. nitrogen, argon, or carbon dioxide) in a solvent (e.g. said hydrocarbon, halohydrocarbon, ether, ester, ketone, alcohol, sulfoxide, or nitile solvent; base such as pyridine or quinoline; acid; acid anhydride such as acetic or trifluoroacetic anhydride; or like solvents or mixtures thereof).

(5) Other modifications

Compounds I are found to be the subject of other structural modifications conventional in the .beta.-lactam chemistry (e.g. double bond migration with a base, protection and deprotection at the carboxy group for COB, protection and deprotection at the amino group for group A, introduction or replacement of group X with a nucleophilic reagent, or transformation of group X or Z within the given definition including acylation, hydrolysis, oxidation, or reduction, and like modifications) to give another Compound I, as are evidenced by working Examples described later.

The said reactions can be carried out in a hydrocarbon solvent (e.g. hexane, toluene), halohydrocarbon (e.g. dichloromethane, chlorobenzene), ether (e.g. diethyl ether, dioxane), ketone (e.g. acetone, cyclohexanone, benzophenone), ester (e.g. ethyl acetate, methyl benzoate), alcohol (e.g. ethanol, t-butanol, benzyl alcohol), amide, carboxylic acid, or other conventional solvents for organic reactions.

(Utilizing side reactions)

When the original molecule contains reactive groups, it may be occationally attacked by the reagent or solvent during the said reaction or work-up. For example, addition of halogen to 3-exomethylene group accompanies N-halogenation in 7-amide chain; imino formation with a base for 7-methoxy introduction causes HZ elimination when Z is halo or acyloxy; and replacement of X being halo with basic nucleophilic reagent results in HZ elimination when Z is halo. These can be deemed usually as side-reactions, but when such side-reactions are used in the right direction more efficient synthesis can be done than conventional step-by-step reaction procedures.

Typical plans of such wise solutions are given in the working examples below. These multi-phase improvements should be included in the scope of this invention, allotting to each of the unit changes found in the molecule.

(Isolation and purification of the products)

Compounds I thus prepared by cyclization, methoxylation, addition, elimination, or other modifications can be isolated from the reaction mixture by removing the used solvent, unreacted materials, by-products, and like contaminants by concentration, extraction, washing, drying or like usual methods, and purified by reprecipitation, chromatography, crystallization, absorption, or like conventional purification. The stereoisomers at position 3 or 7 can be separated by careful chromatography, fractional recrystallization, or like conventional method. If desirable, stereoisomeric mixture may be subjected to reaction of next step of synthesis without separation.

The known method for preparing 1-dethia-1-oxacephalosporins starts from a penicillins (Japanese Patent Publication (Unexamined) No. 51-149295) by cleaving the thiazolidine ring, making azetidinone thiol naked, and rebinding new alcohol units to form azetidinooxazine bicycle. Another total synthesis (Japanese Patent Publication (Unexamined) No. 49-133594) requires more difficult intermolecular cyclization to form the dihydrooxazine ring. This invention aims at no carbon loss from starting penicillins, resulting in smoother intramolecular cyclization and less by-products, to give higher yield of expected Compound I and 1-dethia-1-oxacephalosporins.

Because of intermediacy of carbonium ion at position 4 in the starting azetidinone, prior art-methods result in the formation of an isomeric mixture of 4.alpha. and 4.beta. ethers in around 1:1 ratio, followed by undesired loss of about a half of the ether product. This invention relates to stereoselective synthesis and is accompanied by practically none of such stereoisomers being lost.

As a result of the stereospecific reactions in high yield, products are readily crystallizable after simpler purification.

The following examples illustrate details of this invention, but they are not intended to limit the scope thereof.

The common nuclei and their numbering of compounds in the examples are shown as follows: ##STR35##

The stereochemical relationship carbons 1 and 5 in the bicyclohept-2-ene is directly transfered to the configurations of carbons 6 and 5 in 6-epipenicillins or carbons 7 and 6 in oxacephams, respectively.

The stereochemistry around carbon 6 of 1-dethia-1-oxacepham ring system is identical with carbon 6 of cephalosporins at position 6.

Stereochemistry of COB in the formulae is preferably the same with that in penicillins (i.e. R configuration) but not necessarily restricted to it.

In The following Examples, experimental errors in IR-spectra are within .+-.10 cm.sup.-1 and those in NMR spectra are within .+-.0.2 ppm. Melting points are uncorrected. Anhydrous sodium sulfate was used for drying every solution.

Physical constants of the products are summarized in Table VI.

An Oxazolinoazetidine (II) is dissolved in a solvent and mixed with an acid to give an 1-dethia-1-oxacepham compound (I) under a condition shown in Table I.

Details of reaction No. 13 are given below to show typical experimental procedure of the cyclization. ##STR36##

(1) A solution of diphenylmethyl 2-[(1R,5S)-3-phenyl-7-oxo-4-oxa-2,6-diazabicyclo[3.2.0]hept-2-en-6-yl]-2-i sopropenylacetate (12.0 g), osmium tetroxide (1.0 g) and potassium chlorate (12.0 g) in a mixture of tetrahydrofuran (400 ml) and water (200 ml is stirred at 58.degree. C. for 3.5 hours. After cooling, the reaction mixture is poured into ice-water and extracted with ethyl acetate. The extract is washed with brine, aqueous 10% sodium thiosulfate and then aqueous sodium hydrogencarbonate, dried and evaporated to yield diphenylmethyl 2-[(1R,5S)-3-phenyl-7-oxo-4-oxa-2,6-diazabicyclo[3.2.0]hept-2-en-6-yl]-3,4 -dihydroxy-3-methylbutyrate (12.88 g).

IR: .nu..sub.max.sup.CHCl.sbsp.3 3500br, 1770br, 1742, 1636 cm.sup.-1.

(2) To a solution of the product (10.88 g) prepared above (1) in diethyl ether (300 ml) is added boron trifluoride etherate (75 .mu.l), and the mixture is stirred for 3.5 hours at room temperature under nitrogen atmosphere, poured into cold aqueous sodium hydrogencarbonate, and extracted with ethyl acetate. The extract is washed with brine and evaporated. The residue is washed with a mixture of dichloromethane and ether to yield a mixture (15 g) of isomers at position 3 of diphenylmethyl 7.alpha.-benzamido-3.xi.-methyl-3.xi.-hydroxy-1-dethia-1-oxacepham-4.alpha .-carboxylate.

IR: .nu..sub.max.sup.CHCl.sbsp.3 3560, 3445, 1774, 1739, 1670 cm.sup.-1.

The isomeric mixture is chromatographed on a column of silica gel deactivated with 10% water. Eluate with a mixture (4:1) of benzene and ethyl acetate is recrystallized from a mixture of acetone and ether and then a mixture of acetone and dichloromethane to give those respective two stereoisomers.

(a) To a solution of benzyl 2-[(1R,5S)-3-phenyl-7-oxo-4-oxa-2,6-diazabicyclo[3.2.0]hept-2-en-6-yl)]-3- formyloxymethyl-2-butenoate (54 mg) in methanol (2 ml) is added boron trifluoride etherate (19 .mu.l) under cooling at -20.degree. C., and the mixture stirred at -20.degree. C. to 0.degree. C. for 40 minutes, at 0.degree. C. for 2 hours, and then at room temperature for 1 hour, mixed with aqueous 5% sodium hydrogencarbonate and extracted with dichloromethane. The extract is washed with water, dried, and evaporated. The residue is crystallized from methanol to afford benzyl 7.alpha.-benzamido-3-methyl-1-dethia-1-oxa-3-cephem-4-carboxylate (10 mg=20% yield). mp. 208.degree.-212.degree. C.

(b) In a manner similar to the above but using trifluoromethanesulfonic acid (5 .mu.l) for 130 minutes under ice-cooling or 0.38 N hydrogen chloride in methanol (0.5 ml) for 3 hours, instead of boron trifluoride, the same product (14 mg or 5 mg) is also prepared (27.5% or 7% yield). mp. 208.degree.-212.degree. C.

A 7.beta.-unsubstituted-7.alpha.-amido-1-dethia-1-oxacepham compound (I) is dissolved in a solvent, and mixed with an N-halogenating reagent and a base in methanol under a condition given in Table II to give the corresponding 7.alpha.-methoxy-7.beta.-amido compound.

Details of reactions No. 5 and No. 9 are given below to show experimental procedure of the methoxylation.

(No. 5)

To a solution of diphenylmethyl 7.alpha.-benzamido-3.alpha.-hydroxy-3.beta.-methyl-1-dethia-1-oxacepham-4. alpha.-carboxylate (486 mg) in anhydrous dichloromethane (20 ml) are added t-butyl hypochlorite (0.15 ml) and 2 N solution of lithium methoxide in methanol (1.1 ml) at -50.degree. C., and the mixture is stirred for 15 minutes, mixed with acetic acid (1.2 ml), stirred for 5 minutes, diluted with ice-cooled aqueous sodium hydrogencarbonate and extracted with dichloro methane. The extract is washed with aqueous sodium hydrogencarbonate and water, dried, and evaporated. The colorless foamy residue is purified by chromatography on silica gel to give diphenylmethyl 7.beta.-benzamido-7.alpha.-methoxy-3.alpha.-hydroxy-3.beta.-methyl-1-dethi a-1-oxacepham-4.alpha.-carboxylate (250 mg=48% yield). ##STR38##

To a solution of diphenylmethyl 7.alpha.-benzamido-3.xi.-bromo-3.xi.-bromoethyl-1-dethia-1-oxacepham-4.alp ha.-carboxylate (187 mg) in anhydrous dichloromethane (1 ml) are added t-butyl hypochlorite (46 .mu.l) and 2 M solution of lithium methylate in methanol (0.17 ml) at -30.degree. C., and the mixture is stirred at the same temperature for 1 hour, mixed with a solution of sodium 1-methyltetrazol-5-ylmercaptide (100 mg) in acetone (1 ml) and stirred at room temperature for 1.5 hours. The reaction mixture is diluted with dichloromethane, washed with aqueous sodium hydrogencarbonate and brine, dried, and evaporated. The residue (180 mg) is chloromatographed on a column of silica gel. Eluates with a mixture (1:1) of benzene and ethyl acetate give diphenylmethyl 7.beta.-benzamido-7.alpha.-methoxy-3-(1-methyltetrazol-5-yl)thiomethyl-1-d ethia-1-oxa-3-cephem-4-carboxylate (108 mg).

A 3,3-methylene-1-dethia-1-oxacepham compound (I) is dissolved in a solvent, mixed with an addition reagent XZ under conditions shown in Table III to give an addition product.

Details of those reactions No. 3, No. 4, and No. 15 are given below to show experimental procedure of the addition. ##STR39##

(No. 3)

To a solution of diphenylmethyl 7.alpha.-benzamido-3-exomethylene -1-dethia-1-oxacepham-4.alpha.-carboxylate (519 mg) in dichloromethane (5 ml) is added 0.76 N solution of chlorine in carbon tetrachloride (1.6 ml), and the mixture is stirred under irradiation with a tungusten lamp at -20.degree. to -30.degree. C. for 40 minutes, mixed with 0.14 ml of cyclopentene, and stirred for 5 minutes.

The reaction mixture is stirred with 0.14 ml of 1,5-diazabicyclo[3.4.0]non-5-ene at -20.degree. C. for 10 minutes, washed with dilute hydrochloric acid and water, dried, and evaporated. The crystalline residue is recrystallized from methanol to give diphenylmethyl 7.alpha.-benzamido-3-chloromethyl-1-dethia-1-oxa-3-cephem-4-carboxylate (484 mg=86% yield).

mp. 120.degree.-128.degree. C.

(No. 4)

To a solution of diphenylmethyl 7.alpha.-benzamido-3-methylene-1-dethia-1-oxacepham-4.alpha.-carboxylate (103 mg) in methylene chloride (1 ml) is added 0.75 N solution of chlorine in carbon tetrachloride (0.3 ml), and the mixture is irradiated with tungusten lamp at -20.degree. to -30.degree. C. for 30 minutes, and evaporated under reduced pressure to give diphenylmethyl 7.alpha.-benzamido-3.xi.-chloro-3.xi.-chloromethyl-1-dethia-1-oxacepham-4. alpha.-carboxylate (120 mg).

(No. 15)

In a manner similar to the above, diphenylmethyl 7.alpha.-phenylacetamido-3-methylene-1-dethia-1-oxacepham-4.alpha.-carboxy late (705 mg) is reacted with 1.77 equivalents of chlorine in dichloromethane (7 ml) at a temperature below -25.degree. C. to give diphenylmethyl 7.alpha.-phenylacetamido-3.xi.-chloro-3.xi.-chloromethyl-1-dethia-1-oxacep ham-4.alpha.-carboxylate.

The latter is treated with piperidine (0.16 ml) at 15.degree. C. for 40 minutes to yield diphenylmethyl 7.alpha.-phenylacetamido-3-chloromethyl-1-dethia-1-oxa-3-cephem-4-carboxyl ate (583 mg=78.4% yield) mp. 179.degree.-182.degree. C. (decomposition).

To a solution of diphenylmethyl 7.alpha.-benzamido-3-methylene-1-dethia-1-oxacepham-4.alpha.-carboxylate (1.405 g=3.0 mmoles) in dry dichloromethane (28 ml) cooled at -26.degree. C. is added powdered copper (141 mg) with stirring under nitrogen atmosphere and the mixture is dropwise mixed with 1.2 M solution of chlorine in chloroform (6.3 ml=2.5 equivalents) during 10 minutes, and stirred at -22.degree. to -30.degree. C. for 3 hours. The reaction mixture is mixed with an aqueous solution of sodium thiosulfate pentahydrate (2.98 g=4 equivalents), extracted twice with dichloromethane, washed with aqueous sodium hydrogencarbonate, washed twice with aqueous sodium chloride, dried over magnesium sulfate and evaporated. The residue is chromatographed over 190 g of silica gel and eluted with a mixture of benzene and ethyl acetate (3:1) to give colorless foamy diphenylmethyl 7.alpha.-benzamido-3.alpha.-chloro-3.beta.-chloromethyl-1-dethia-1-oxaceph am-4.alpha.-carboxylate (1.541 g=95.2% yield).

A 1-dethia-1-oxacepham compound is dissolved in a solvent and mixed with an eliminating reagent under conditions shown in Table IV to give a 1-dethia-1-oxacephem compound (I).

Details of reaction No. 12 are given below to show experimental procedure of the elimination. ##STR41##

To a suspension of diphenylmethyl 7.alpha.-benzamido-3.xi.-hydroxy-3.xi.-methyl-1-oxadethiacepham-4.alpha.-c arboxylate (15.0 g) in dichloromethane (100 ml) are added pyridine (6.8 ml) and thionyl chloride (3 ml) with stirring under ice-cooling, and the mixture is stirred for 7.25 hours at the same temperature and for 2.25 hours at room temperature, and poured into ice-water. The organic layer is separated, washed with water, dried, and evaporated. The residue is chromatographed on silica gel (350 g) deactivated with 10% water. Eluate with a mixture (9:1) of benzene and ethyl acetate gives diphenylmethyl 7.alpha.-benzamido-3-methyl-1-dethia-1-oxa-3-cephem-4-carboxylate (2.65 g=25.2% yield) (mp. 144.degree.-146.degree. C.) and diphenylmethyl 7.alpha.-benzamido-3-methyl-1-dethia-1-oxa-2-cephem-4.alpha.-carboxylate (1.05 g=10.8% yield) (IR: .nu..sub.max.sup.CHCl.sbsp.3 3440, 1782, 1745, 1676 1663sh cm.sup.-1).

A 7.alpha.-amino-7.beta.-unsubstituted-3-exomethylene-1-dethia-1-oxacepham-4 -carboxylate is dissolved in dichloromethane, mixed with a halogenating reagent and a base in methanol to give a 3-halo-3-halomethyl-7.alpha.-methoxy-7.beta.-amino-1-dethia-1-oxa-3-cephem -4-carboxylate under conditions given in Table V. Occasionally, 3-halogenomethyl is replaced by another nucleophile.

Details of Example V-6 are given below to show experimental procedure of the continuous process of addition, methoxylation, and elimination. ##STR42##

To a solution of diphenylmethyl 7.alpha.-p-cyanobenzamido-3-exomethylene-1-dethia-1-oxacepham-4.alpha.-car boxylate (246 mg) in dichloromethane (8 ml) cooled at -50.degree. C. is added 1.2 M solution of chlorine in carbon tetrachloride (1.47 ml) and the mixture is stirred under irradiation with 300 W tungusten lamp for 7 minutes. To the reaction mixture containing thus formed diphenylmethyl 7.alpha.-(N-chloro-p-cyanobenzamido)-3-exomethylene-1-dethia-1-oxacepham-4 .alpha.-carboxylate 2 M solution of lithium methoxide in methanol (1.57 ml) is added, and, the whole mixture is cooled at -50.degree. C. to -60.degree. C. with stirring for 10 minutes, added acetic acid (0.2 ml), poured into ice-water, and extracted with dichloromethane. The extract is washed with dilute aqueous sodium hydrogen carbonate and water, dried, and evaporated to dryness. The residue contains diphenylmethyl 7.alpha.-cyanobenzamido-7.alpha.-methoxy-3-chloro-methyl-1-dethia-1-oxa-3- cephem-4-carboxylate. It is dissolved in dichloromethane (6 ml) with stirring with sodium 1-methyl-tetrazol-5-mercaptide (100 mg) and tetrabutylammonium bromide (20 mg) in water (3 ml) at room temperature for 1 hour. The reaction mixture is poured into ice-water, extracted with dichloromethane, washed with water, dried, and evaporated to leave 335 mg of residue which gives pure 7.beta.-p-cyanobenzamido-7.alpha.-methoxy-3-(1-methyltetrazol-5-ylthio)met hyl-1-dethia-1-oxa-3-cephem-4-carboxylate (251 mg) after silica gel-column chromatography.

To a solution of 7.beta.-benzamido-7.alpha.-methoxy-3-methyl-1-dethia-1-oxa-2-cephem-4-carb oxylic acid (100 mg) in acetone (10 ml) is added triethylamine (0.1 ml), and the mixture allowed to stand for 6 days. Spots of the reaction mixture on thin layer chromatogram correspond to those of 7.beta.-benzamido-7.alpha.-methoxy-3-methyl-1-dethia-1-oxa-3-cephem-4-carb oxylic acid and of the starting material.

To a solution of diphenylmethyl 7.alpha.-benzamido-3,3-methylene-1-dethia-1-oxacepham-4.alpha.-carboxylate (5.0 g) in dichloromethane (25 ml) is added triethylamine (0.5 ml), and the mixture is stirred at room temperature for 80 minutes, concentrated after addition of small amount of benzene, and diluted with ether to give crystals of diphenylmethyl 7.alpha.-benzamido-3-methyl-1-dethia-1-oxa-3-cephem-4-carboxylate (4.5 g=90% yield).

The mixture is kept in equilibrium at room temperature for 15 hours to give 50.8% of .DELTA..sup.2 -isomer, 4.1% of a mixture of .DELTA..sup.2 and .DELTA..sup.3 -isomers, and 38.3% of .DELTA..sup.3 -isomer after chromatographic separation.

To a solution of 7.alpha.-benzamido-3,3-methylene-1-dethia-1-oxacepham-4.alpha.-carboxylic acid (100 mg) in acetone (10 ml) is added triethylamine (0.1 ml), and the mixture is allowed to stand for 5 days. Spots of the reaction mixture correspond to those of 7.alpha.-benzamido-3-methyl-1-dethia-1-oxa-2-cephem-4-carboxylic acid, 7.alpha.-benzamido-3-methyl-1-dethia-1-oxa-3-cephem-4-carboxylic acid, and the starting material.

To a solution of diphenylmethyl 7.beta.-benzamido-7.alpha.-methoxy-3.alpha.-methyl-3.beta.-acetoxy-1-dethi a-1-oxacepham-4.alpha.-carboxylate (960 mg) in anisole (4 ml) is added trifluoroacetic acid (10 ml) at 0.degree. C., and the mixture is stirred for 15 minutes and evaporated under reduced pressure. The residue is solidified from a mixture of ether and n-hexane to yield 7.beta.-benzamido-7.alpha.-methoxy-3.alpha.-methyl-3.beta.-acetoxy-1-dethi a-1-oxacepham-4.alpha.-carboxylic acid (470 mg) as colorless powder (70% yield).

mp. 203.degree.-208.degree. C. (decomposition).

In a similar manner, the following free carboxylic acids at position 4 are prepared from the corresponding diphenylmethyl esters.

7.beta.-Benzamido-7.alpha.-methoxy-3.alpha.-hydroxy-3.beta.-methyl-1-dethia -1-oxacepham-4.alpha.-carboxylic acid, mp. 100.degree.-105.degree. C. (decomposition).

7.alpha.-Benzamido-7.alpha.-methoxy-3.alpha.-trifluoroacetoxy-3.beta.-methy l-1-dethia-1-oxacepham-4.alpha.-carboxylic acid, mp. 108.degree.-113.degree. C.

7.beta.-Benzamido-7.alpha.-methoxy-3-methyl-1-dethia-1-oxa-2-cephem-4-carbo xylic acid, mp. 195.degree.-198.degree. C.

IR: .nu..sub.max.sup.KBr 3250, 1766, 1742, 1642 cm.sup.-1.

7.alpha.-Benzamido-3.xi.-chloro-3.xi.-chloromethyl-1-dethia-1-oxa-cepham-4. alpha.-carboxylic acid, mp. 118.degree.-122.degree. C. (decomposition).

To a solution of diphenylmethyl 7.alpha.-benzamido-3-exomethylene-1-dethia-1-oxacepham-4.alpha.-carboxylat e (1.125 g) in a mixture of dichloromethane (15 ml) and anisole (3.5 ml) is added dropwise a solution of aluminum trichloride (625 mg) in nitromethane (20 ml) at -20.degree. C. with stirring, and the mixture is stirred at -10.degree. to -20.degree. C. for 30 minutes under nitrogen atmosphere. The reaction mixture is poured into ice-water containing hydrochloric acid and extracted with ethyl acetate. The extract solution is washed with saturated aqueous sodium hydrogen carbonate, and the washings are acidified with concentrated hydrochloric acid and reextracted with ethyl acetate. The organic layer is washed with water, dried and evaporated to leave 7.alpha.-benzamido-3-exomethylene-1-dethia-1-oxacepham-4.alpha.-carboxylic acid (623 mg).

Similarly, diphenylmethyl 7.alpha.-benzamido-3-methyl-1-dethia-1-oxa-2-cephem-4.alpha.-carboxylate (1.8 g) in dichloromethane (25 ml) is subjected to solvolysis with anisole (5.8 ml), aluminum trichloride (1.026 g), and nitromethane (36 ml) at -10.degree. C. for 30 minutes to give 7.alpha.-benzamido-3-methyl-1-dethia-1-oxa-2-cephem-4.alpha.-carboxylic acid (935 mg=72.6% yield).

To a solution of diphenylmethyl 7.alpha.-amino-3-methylene-1-dethia-1-oxacepham-4.alpha.-carboxylate (25 mg) in dichloromethane (0.5 ml) are added pyridine (7 .mu.l) and benzoyl chloride (10 .mu.l) at -20.degree. C. under nitrogen atmosphere, and the mixture is stirred for 1 hour, poured into ice-water, stirred for 5 minutes, and extracted with dichloromethane. The organic layer is separated, washed with water, aqueous sodium hydrogencarbonate and water, dried, and evaporated to give diphenylmethyl 7.alpha.-benzamido-3-methylene-1-dethia-1-oxacepham-4.alpha.-carboxylate (28 mg=86% yield). This product is identified with TLC and NMR techniques.

To a solution of diphenylmethyl 7.alpha.-benzamido-3-methylene-1-dethia-1-oxacepham-4.alpha.-carboxylate (94 mg) in dichloromethane (4 ml) are added pyridine (32 .mu.l) and a 0.37 M solution of phosphorus pentachloride in dichloromethane (1.08 ml) at -40.degree. C. under nitrogen atmosphere, and the mixture is warmed up to room temperature, stirred for 1 hour, cooled again to -40.degree. C., mixed with methanol (8 ml), warmed up to 0.degree. C., mixed with water (0.8 ml) and evaporated under reduced pressure. The residue is dissolved in ethyl acetate (20 ml) and washed with water. The solution is extracted with aqueous sodium hydrogencarbonate and water. The combined aqueous extract and washing are covered with ethyl acetate, adjusted to pH 7.0 and extracted with ethyl acetate. The organic layer is separated, washed with water, dried and evaporated to yield diphenylmethyl 7.alpha.-amino-3-methylene-1-dethia-1-oxacepham-4.alpha.-carboxylate (29 mg=40% yield).

IR: .nu..sub.max.sup.CHCl.sbsp.3 3000, 1770 sh, 1760, 1740 cm.sup.-1.

(1) To a solution of diphenylmethyl 7.alpha.-benzamido-3.xi.-hydroxy-3.xi.-bromomethyl-1-dethia-1-oxacepham-4. alpha.-carboxylate (108 mg) in acetone (5 ml) containing 10% water is added potassium carbonate (50 mg), and the mixture is stirred at room temperature for 1.5 hours, diluted with brine, and extracted with dichloromethane. The extract is dried over magnesium sulfate and evaporated. The residue (90 mg) is purified by thin-layer chromatography on silica gel plate (solvent system: benzene+ethyl acetate (2:1)) to afford diphenylmethyl 7.alpha.-benzamido-3,3-epoxymethano-1-dethia-1-oxacepham-4.alpha.-carboxyl ate (40 mg) (isomer A). Another stereoisomer B at position 3 (56 mg) is obtained from the stereoisomeric starting material (140 mg).

(2) To a solution of 1-methyltetrazol-5-ylthiol (20 mg) in tetrahydrofuran (2 ml) is added a 1.5 M-solution of n-butyl lithium in hexane (0.05 ml), and the mixture is stirred for 30 minutes, mixed with a solution of diphenylmethyl 7.alpha.-benzamido-3,3-epoxymethano-1-dethia-1-oxacepham-4.alpha.-carboxyl ate (56 mg) (epimer B) in tetrahydrofuran (1 ml), stirred for 1 hour, mixed with aqueous sodium hydrogencarbonate, and extracted with ethyl acetate. The extract is washed with brine, dried over magnesium sulfate, and evaporated. The residue is chromatographed on a column of silica gel (1 g) deactivated with 10% water. Eluate with a mixture (9:1) of benzene and ethyl acetate gives diphenylmethyl 7.alpha.-benzamido-3-(1-methyltetrazol-5-yl)thiomethyl-3-hydroxy-1-dethia- 1-oxacepham-4.alpha.-carboxylate (43 mg) (epimer B).

(1) To a solution of diphenylmethyl 7.alpha.-benzamido-3.alpha.-hydroxy-3.beta.-methyl-1-dethia-1-oxacepham-4- carboxylate (100 mg) in isopropenyl acetate (5 ml) is added p-toluenesulfonic acid-monohydrate (6 mg), and the mixture is heated at 60.degree. C. for 75 minutes. After cooling, the reaction mixture is poured into icy dilute aqueous sodium hydrogencarbonate and extracted with dichloromethane. The organic layer is separated, washed with water, dried and evaporated to give diphenylmethyl 7.alpha.-benzamido-3.alpha.-acetoxy-3.beta.-methyl-1-dethia-1-oxacepham-4. alpha.-carboxylate (30.5% yield).

(2) The same starting material as in (1) can be treated with a mixture of 1.1 equivalents of lithium diisopropylamide, 1.2 equivalents of acetyl chloride, and 20 parts by volume of tetrahydrofuran at -40.degree. C. for 45 minutes, at -20.degree. C. for 15 minutes, and then at 0.degree. C. for 20 minutes or with 1 equivalent of pyridine and 1.2 equivalents of acetyl chloride in dichloromethane to give the same product.

(3) To a solution of diphenylmethyl 7.beta.-benzamido-7.alpha.-methoxy-3.alpha.-hydroxy-3.beta.-methyl-1-dethi a-1-oxacepham-4.alpha.-carboxylate (52 mg) in dioxane (1 ml) is added trifluoroacetic acid anhydride (0.1 ml) under nitrogen atmosphere under ice-cooling, and the mixture is kept at room temperature for 2 hours, mixed with water (0.3 ml), stirred for 30 minutes, diluted with ice-water, and extracted with ethyl acetate. The extract is washed with water, dried, and evaporated to yield oily diphenylmethyl 7.beta.-benzamido-7.alpha.-methoxy-3.alpha.-trifluoroacetoxy-3.beta.-methy l-1-dethia-1-oxacepham-4.alpha.-carboxylate (64 mg).

(4) A solution of diphenylmethyl 7.alpha.-benzamido-3.xi.-hydroxy-3.xi.-hydroxymethyl-1-dethia-1-oxacepham- 4.alpha.-carboxylate (112 mg) in a mixture of pyridine (0.5 ml) and acetic anhydride (0.3 ml) is kept at 0.degree. C. overnight. The mixture is concentrated in vacuo, poured into ice water, and extracted with ethyl acetate. The extract is washed with water, dilute hydrochloric acid, aqueous sodium hydrogen carbonate, and water, dried, and concentrated to give diphenylmethyl 7.alpha.-benzamido-3.xi.-hydroxy-3.xi.-acetoxymethyl-1-dethia-1-oxacepham- 4.alpha.-carboxylate (54 mg) as crystals melting at 118.degree. to 120.degree. C.

(5) To a solution of diphenylmethyl 7.alpha.-benzamido-3.xi.-hydroxy-3.xi.-hydroxymethyl-1-dethia-1-oxacepham- 4.alpha.-carboxylate (350 mg) in dichloromethane (3 ml) are added pyridine (78 .mu.l) and methanesulfonyl chloride (75 .mu.l), and the mixture is stirred at 0.degree. C. for 1 hour at room temperature for 3 hours. The reaction mixture is poured into ice-water, and extracted with ethyl acetate. The extract is washed with water, aqueous sodium hydrogencarbonate, and water, dried, and evaporated to residue (370 mg) giving diphenylmethyl 7.alpha.-benzamido-3.xi.-hydroxy-3.xi.-methanesulfonyloxymethyl-1-dethia-1 -oxacepham-4.alpha.-carboxylate (145 mg) after silica gel chromatography.

To a solution of Compound (a) (512 mg) in a mixture of benzene (10 ml) and methanol (1 ml) is added triphenylphosphine (0.4 g), and the mixture stirred at 65.degree. C. for 1.5 hours. The residue is chromatographed on a column of silica gel (30 g) deactivated with 10% water. Eluate with benzene containing 20-30% acetic acid yields 202 mg of Compound (b).

IR: .nu..sub.max.sup.CHCl.sbsp.3 3370, 1782, 1755, 1635 cm.sup.-1.

NMR: .delta..sup.CDCl.sbsp.3 2.50-3.35m1H, 4.18s2H, 5.08s1H, 5.22s1H, 5.28d (3 Hz)1H, 5.50s1H, 6.08d(3 Hz)1H, 6.93s1H, 7.20-8.00m15H.

(Step 1) To a solution of diphenylmethyl 2-(3-benzyl-7-oxo-2,6-diaza-4-oxabicyclo[3.2.0]hept-2-en-6-yl)-3-methyl-3- butenoate (4.6 g) in ethyl acetate (70 ml) are added 2.74 M-solution of hydrochloric acid in ethyl acetate (3.8 ml) and 1.47 M-solution of chlorine in carbon tetrachloride (12 ml), and the mixture is stirred at room temperature for 15 minutes. Then, aqueous 5% sodium thiosulfate (80 ml), sodium hydrogencarbonate (3.4 g) and acetone (240 g) are added to the reaction mixture, and the combined solution is kept at room temperature for 2.5 hours. The product is isolated by extracting with ethyl acetate, drying over sodium sulfate, and evaporating to yield diphenylmethyl 2-(3-benzyl-7-oxo-2,6-diaza-4-oxabicyclo-[3.2.0]hept-2-en-6-yl)-3-chlorome thyl-3-butenoate (3.33 g), mp. 82.degree.-83.degree. C.

(Step 2) The butenoate above is dissolved in acetone (25 ml), mixed with sodium iodide (3.3 g) and kept at room temperature for 2 hours. The reaction mixture is concentrated to remove acetone and extracted with ethyl acetate. The extract is washed with aqueous 5% sodium thiosulfate and water, dried over sodium sulfate, and evaporated to leave the corresponding iodide (3.0 g).

(Step 3) To a solution of the iodide above (1.59 g) in a mixture of dimethyl sulfoxide (13 ml) and water (3 ml) is added cupric oxide (0.77 g), and the mixture is stirred at 39.degree. C. for 1 hour. The reaction mixture is filtered to remove solid part and extracted with ethyl acetate. The extract solution is washed with water, dried over sodium sulfate, and evaporated to give diphenylmethyl 2-(3-benzyl-7-oxo-2,6-diaza-4-oxabicyclo-[3.2.0]hept-2-en-6-yl)-3-hydroxym ethyl-3-butenoate (0.35 g), mp. 40.degree.-55.degree. C.