CA1180695A - Process for preparing 2-penem compounds - Google Patents

Abstract

A B S T R A C T

The present invention relates to compounds of the formula (I) wherein n is 0 to 4;
R is hydrogen, an alkali metal or quaternary ammonium cation or a metabolisable ester group;
R1 and R2 are independently hydrogen or lower alkyl;
R4 is hydrogen, lower alkyl or a group of the formula R5CHOH- with R5 being hydrogen, lower alkyl, aryl, aralkyl, heteroaryl or heteroaralkyl;
R6 is amino, loweralkylamino, an .alpha.-aminoacid residue bonded through the a-nitrogen atom or the group -OR8 with R8 being hydrogen, lower alkyl, allyl, aryl, aralkyl, an alkali metal or quaternary ammonium cation or a metabolisable ester group;
R7 is hydrogen, loweralkyl, loweralkoxycarbonyl, aryl, aralkyl, aralkoxycarbonyl, arylsulfonyl, acyl, or, together with the N-hydrogen, the grouping wherein either R9 is aryl and R10 is hydrogen, lower alkyl or aralkyl; or R9 is hydrogen, amino or mono- or dilower-alkylamino and R10 is amino, mono- or diloweralkyl amino, lower alkyl, aryl, aralkyl or lower alkoxycarbonyl; and 1,3-dicarbonyl adducts at the 2'-amino group when R7 is hydrogen;
to pharmaceutical compositions comprising such compounds and methods for preparing them.

Description

6~i , PROCESS FOR PREPARING ~-PENEM COMPOUNDS

.

The present invention relates to compounds of the formula 1\ / 2 N~

4 ~S ~C~)n C~ C 6 - CC~OR

S wherein n is 0 to 4;
R is hydrogen, an alkali metal or quaternary ammonium cation or a metabolisable ester group;

R and R are independently hydrogen or lower alkyl, R4 is hydrogen, lower alkyl or a group of the formula R5CHOH- with R5 being hydrogen, lower alkyl, aryl, aralkyl, heteroaryl or heteroaralkyl;
R6 is amino, loweralkylamino, an a-aminoacid xesidue bonded.through the a-nitrogen atom or the goup -OR8 with R8 being hydrogen, lower alkyl, allyl, aryl, aralkyl, an alkali metal or quaternary ammonium cation or a metabolisable ester group;
R7 is hydrogen, loweralkyl, loweralkoxycarbonyl, aryl; aralkyl, aralkoxycarbonyl, arylsulfonyl, acyl, or, 6~

together with the N-hydrogen, the grouping =C~R9 wherein either R9 is aryl and Rlo is hydrogen, lower alkyl or aralkyl; or Rg is amino or mono- or dilower alkylamino and Rlo is amino, mono- or diloweralkyl amino, lower -alkyl, aryl, aralkyl or lower alkoxycarbonyl; and 1,3-dicarbonyl adducts at the 2'-amino group when R7 is hydrogen.

The penems of this invention are named by re-ference to t~le following formula ( R7 R5 - IC ~ ~ S C - (CB2)~ - CU ~ R6 The lower alkyl yroups referred to above contain 1 to 6 carbon atoms and are exemplified by methyl, ethyl, propyl, butyl, pentyl, hexyl, and the corresponding branched chain isomers thereof.
The term "acyl" as used herein denotes groups of the formula ~1~- wherein ~1 is lower alkyl, aralkyl, alkenyl or alkynyl of 2-6 carbon atoms, cycloalkyl of 4-6 carbon atoms, heteroaryl, heteroaralkyl, optionally substituted by hydroxy, thiol, alkylthio, lower alkyl, lower alkoxy, halogen, cyano, carboxy, nitro, amino, aminoloweralkyl, or haloloweralkyl,such as trifluoromethyl, and other similar acyl groups found in conventional penicillin derivatives. Representative of such groups are those such as benzyl, p-hydroxybenzyl~ 4-amino-4-carboxybutyl, methyl, cyanomethyl, 2-pentenyl, n-amyl, p-heptyl, ethyl, 3-or 4-nitrobenzyl, phenethyl, a,~,-diphenylethyl, methyldiphenylmethyl, triphenylmethyl,2-methoxyphenyl, 2,6-dimethoxyphenyl, 2,4,6-trimethoxy-phenyl, 3~5-dimethyl-4-isoxazolyl, 3-butyl-5-methyl-4-isox~zolyl, 5-methyl-3-phenyl-4-isoxazolyl, 3-(2-~- chlorophenyl)-5-methyl-4-isoxazolyl, 3-(2,6-dichlorophenyl), S-methyl-4-isoxazolyl, D-4-amino-4-carbcxybutyl, D-4-N-benzoylamino-4-carboxy-n-butyl, p-aminobenzyl, o-amino-benzyl, m-aminobenzyl, p-dimethylaminobenzyl, (3-pyridyl) methyl, 2-ethoxy-1-napthyl, 3-carboxy-2-quinoxalinyl, 3--(2,6-dichlorophenyl)-5-(2-furyl)-4-isoxazolyl, 3-phenyl-4--isoxazolyl, p-carboxymethylbenzyl, m-fluorobenzyl, m-bromobenzyl, p-chlorobenzyl, p-methoxybenzyl, l-napthyl-methyl, 3-isothiazolylmeth~l, 4-isothiazolylmethyl, 5-isothiazolylmethyl, 4-pyridylmethyl, 5-isoxazolylmethyl, 4-methoxy-5-isoxazolylmethyl, 4-methyl-5-isoxazolylmethyl, . 20 2-imidazolylmethyl, 2-benzofuranylmethyl, 2-indolylmethyl,

2-phenylvinyl, 2-phenylethynyl, l-aminocylohexyl, 2- and

3-thienylaminomethyl, 2-(5-nitrofuranyl)vinyl, phenyl, o-methoxyphenyl, o-chlorophenyl, o-phenylphenyl, p-amino-methylbenzyl, l-(5-cyanotriazolyl)methyl, difluoromethyl, --dichloromethyl, dibromomethyl, 1-(3-methylimidazolyl) methyl, 2- or 3-(4-carboxymethylthienyl)methyl, 2- or 3-69~i

4 -(5-methylthienyl)methyl, 2- or 3-(methoxythienyl)methyl, 2- or 3-(4-chlorothienyl)methyl~ 2- or 3-(5-carboxy~hienyl) methyl, 3-~1,2,5-~hiadiazolyl)methyl, 3-(4-methoxy-1,2,5-thiadiazolyl)methyl, 2-filrylmethyl, 2-(5-nitrofuryl)methyl, 3-furylmethyl, 2-thienylmethyl, 3-thienylmethyl, tetrazol-ylmethyl and cyclohexylamidinomethyl. The term "acyl"
also denotes an acyl residue derived from an a-amino acid of the L or D configuration such as alanine, valine or ~- leucine. The term "an a-aminoacid residue bonded through the a-nitroge~ atom" as used in connection with substituent R6 also denotes resldues derived from an a-amino acid of the L or D coniguration.
The term aryl as used herein refers to phenyl optionally substituted by one to three lower alkyl, lower alkoxy or halogen groups, e.~. p-tolyl, o-tolyl, m-tolyl, p-chlorophenyl, o-methoxyphenyl, 2-methyl-3-fluorophe~yl, etc.
The term halogen as used herein refers to fluorine, chlorine, bromine and iodine.
Heteroaralkyl as used herein refers to lower alkyl groups substituted by a heteroaryl group.
As used herein, the term heteroaryl encompasses five- and six-membered heterocyclic groups containing from one to four nitrogen, oxygen or sulfur groups, optionally substituted by lower alkyl group. Representative hetero-aryl groups are those such as pyridyl, furanyl, thienyl, quinolinyl. The term is intended to cover all isomers, e.g., 2-pyridyl~ 3~pyridyl and 4-pyridyl.
The lower alkoxy groups referred to above contain 1 to 6 carbon atoms and are exemplified by methoxy, ethoxy, propoxy, butoxy, pentoxy, hexox~ and the corre-sponding branched chain isomers thereof.
The term aralkyl denotes a lower alkyl groupsubstituted by one or two aryl groups, e.g., benzyl, phenethyl, benzhydryl and the like, which each may be optionally substituted by one to three lower alkyl, lower alkoxy or halogen groups.
The term metabolisable ester group denotes an ester group which is metabolically removed in the body.
- Two particularly useful metabolisable ester groups are the phthalidyl group and the pivaloyloxymethyl ~roup.
15The term 1,3-dicarbonyl adduct as usea herein refers to the addition product between the amino group of the amino acid carbon and a 1,3-dicarbonyl compound of the formula O

wherein the R'groups can be alike or different and are selected from the group consisting of lower alkyl, lower alkoxy ox together may be part of a cyclic ring structure.
Representative 1,3-dicarbonyl compounds utilized are those such as methyl acetoacetate, dihydroresorcinol, dimedone and acetyl acetone.

, -- 6 The alkali metal salts may be derived from potassium, sodium, lithium, etc., with potassium and sodium being particularly preferred. The quarternary ammonium salts may ~e those such as pyridinium, procaine, N-methyl-glucamine, ethanolamine or diethanolamine.
The foregoing compounds possess several centersof chirality and are produced by thevariou~s processes as various isomeric mixtures. The present invention includes compounds of the preferred stereochemical configuration of formula I and mixtures of it together with its enantiomers.
With respect to the penem nucleus itself, the preferred configuration of the carbon atoms in positions

- 5 and 6 is R and S, respectively. The two hydrogen atoms attached to the 5 and 6 carbon atoms are thus trans to one another. The stereochemistr,y of the C-8 carbon atoms may be designated as either R or S depending on the exact ,, nature of the R5 substituent. For instance, the compounds wherein R5is methyl will have the 8R stereochemistry.
The most preferred stereochemical configuration for a compound of this invention whereln R5 is methyl is design-ated 5R,6S,8R, and has the following representative spatial configuration: - ' R~ ~ R2 ~ '' ~ e (Ia) 3_ Cll ,r ~S (CH2~n ~ CH ~ ~ 6 0~ CO

The prefer ed stexeochemical configuration of all the compo-lnas of formula I is that shown ln formula Ia; how-ever, the nomenclature may differ depending on the nature of the R5 substituent. ~herein the R5 group of formula I has a higher priority in the Cahn-Ingold-Prelog s~stem, e.~., a 2-pyridyl group, a compound having the most pre~erred stereochemical configuration will be designated 5R, 6S, 8S, but be of the same relative spatial configur-ation at C-5, C~6 and C-8 as the 5R, 6S, 8R compound of formula Ia. These compounds additionally possess an asymetric center at the carbon atom to which the -NHR7 an~ -COR6 substituents are attached ("amino acid carbon") depending on the configuration of the starting materials.

Most preferably this carbon atom will possess absolute ~tereochemistry of the R configuration when n > 0 and of the S configuration when n = 0. When naturally occurring amino acids other than cysteine are utilized as starting materials, the amino acid carbon will be of the "R" or "D" and the `'S" or "L" configurations. In the case of cysteine, when D-cysteine is the starting amino acid in the synthesis of Ia, the product is designated as having a 2`S configuration by the Cahn-Ingold-Prelog System, conversely, L-cysteine will lead to a product Ia designated as having a 2'R configuration. However, D-homocysteine and its homologs and L-homocysteine and its homologs lead to products Ia with a 2'R or 2 S configuration, respectively, according to the Cahn-Ingold-Prelog System.

~ 9~
- 7a --Certain of the processes of this invention produce these compounds as their racemic mixtures, e~q., a 5R,6S,8R
compound is produced with its enantiomer (mirror image), i.e., a 5S,6R98S compound in -the equal amounts when the starting compound is a racemic mixture~ The two enantiomers may be separated by conventîonal means, e~q., by resolution by fractional crystallizations of optically active salt forms, e.q., the salts derived from optically active amino acids, i-~-brucine, or ~ and (-)ephedrine.
Alternatively, the compounds may be produced in their pure enantiomeric forms by utilizing optically active intermediates in the synthetic procedure. These optically active intermediates may be produced by conventional resolution or by stereospecific synthesis according to the procedures discribed in European patent application having the publication number 13 662.
~_ Preferred compounds of formula I are those wherein R5 is a lower alkyl group. Varticularly p~eferred are those compounds of formula I wherein R5is a methyl group, n is zero and Rl and R2 are both hydrogen. Preferred R7 substituents are hydrogen, loweralkoxy carbonyl or acyl the latter being selected from a-aminoacid residues, and preferred R6 substituents are amino, an ~-amino acid residue bonded through the ~-nitrogen atom or the group -OR8 with R8 being hydrogen, lower alkyl or an alkali metal or `~ quaternary ammonium cation.
- A most particularly preferred group of compounds of formula I encompassed by this invention are those wherein R5 is methyl and the stereochemical configuration is designated 5R,6S,~R. Of these, the compounds wherein the amino acid carbon possesses the R configuration when n ~o and the S configura-tion when n = o are most highly preferred.

A particularly preferred compound is (5R,6S,8R,2'S)-2-~(2'-amino-2'-carboxyethyl3thio]-6-(l-hydroxyethyl)-2-penem-3-carboxylic acid, sodium saltO

The compounds of this invention possess antibac-terial activity of both the gram-positive and gram-neaa-tive type. Thlls, when tested in standardized microbio-log~cal assays, the compounds of this invention are active against such gram-positive organisms as Stap~ylococcus epidermidis, and Bacillus subtilis, and such gram-negative -oxganisms as E. coli, Pseudomonas and Salmonella at test levels of 0.1 to 100 ug/ml. ~dditionally, they show activity against such organisms in the presence of penicil-lanase indicating a resistance to this enzyme and are inhibitors of beta-lactamases. ~or instance, pyridinium 15R,6S,8R,2'S) 2-~(2'-amino-2'-carboxyethyl)thio~-6-~l-hydroxyethyl)-2-penem-3-carboxylate is active against Salmonella 76061701 at a test level of about 0.25 Jug/ml and against E. coli ATCC 10536 at a test level of 0.5 ~g/ml.
Thus, the present invention includes within its scope pharmaceutical compositions comprising a penem of formula I together with a pharmaceutically acceptable carrier or coating.
The dosage administered of the penems of this invention is dependent upon the age and weight of the animal species being treated t the mode of administration, and the type and severity o~ bacterial infection being prevented or reduced. Typically, the dosage administered per day will be in the range of 100-5000 mg, with 500-1000 mg being preferred.
- For oral administration, the compounds of this vention may be formulated in the form of tablets, capsules, elixirs or the like. Likewise, they may be admlxed with animal feed~ They may also be applied topically in the form of ointments, both hydrophilic and hydrophobic, in the ~orm of lotions which may be aqueous, non-aqueous or of the emulsion type, or in the form of creams.
The compounds of formula I may be utili,zed in liguid ~orm such as solutions, suspensions and the like ` for otic and optic use and may also be administered parenterally via intramuscular injections.
The compounds of this invention are preparable by cyclising a compound of the formula H H Rl~7 R4 ~ \ C / \ I - (CH2)n - CH C ~
l Z R2 6 , O~ \
f y . - O=C--OPg wherein Z is sulfur or oxygen and n, ~4, Rl and ~2 are as defined above any functional group therein being optionally protected; Pg is a carboxy protecting group, R'6 is protected amino or protected lower alkylamino or the group -OR8 with R8 being lower alkyl, allyl, aryl, aralkyl or a car~oxy protecting group; R'7 is loweralkyl, lo~Jeralkoxycarbony], aryl, aralkyl, aralkoxycarbonyl~
arylsulfonyl or an amino protecting group; and ~ is a phosphonio group being double bonded to the adjacent -carbon atom or a phosphonato group with a single bond to the adjacent carbon atom the negative charge of which is compensated by the presence of a cation;
if reguiredl separating a mixture of diastereo-isomers before or after removing any protecting group andthen subjecting a so-obtained compound to one or more of the facultative steps (i) to (vi):

~i) formation of a salt or of metabolisable ester group representing substituents R and R6;
(ii) introducing the xesidue of the a-aminoacid re-presenting substituent R6;
(III~ separation of a mixture of enantiomers;
(iv) introducing acyl representing substituent R7 at the 2'-amino group;
15 Iv) introducing the grouping =CRgRlo representing R7 together with the N-hydrogen; and f ~(vi) formation of a 1,3-dicarbonyl adduct at the 2'-amino group when R7 is hydrogen.

Compounds of formula II are preparable by a reaction sequenc~ starting wi~h a compound of the formula C~3 ~ N~ (IIIa~

wherein R4 is as hereinbefore deflned except that any free hydroxy group is protected by a suitable hydroxy - 12 ~ P~

protecting group. This starting material i5 treated with an anion of the formula ~ 2 Z / ~ . ~
S - C - 5 ~ ~n ~ 6 (IIIb) 1~ R2, R 6 , -R 7, Z and n are as hereinbefore defined, to afford the compound of formula IV

.

i \ / 2 NRR' `~

R ~ ~ C~23n ~ ( '~ - CO ~
o~N~ ~IV) 1~ 2~ R 6~ R 7~ Z and n are as hereinbefore defined and R4 is as hereinbefore defined except that any free hydroxy group is protected by a suitable hydroxy protecting group. Preferred amino and carboxy protecting ~roups are p-nitrobenzyl and allyl with the latter being particularly preferred. Generally, this reaction is conaucted by preparing the anion of formula (IIIb) in situ and then adding the compound of formula (IIIa~ to the aqueous reaction mixture. Ty ically, the reaction is conducted at room temperature or in the cold.
Alternatively, the intermediate of formula IV may be prepared in a reaction sequence which begins with treatment of an optically active compound o~ the formula V:

~4 ~ `f ~ c~3 IV~

~ -N ~CO~R~

wherein R8 is a lower alkyl or aralkyl group and R4 is as hereinbefore defined except that any free hydroxy group is protected by a suitable hydroxy protecting group, with _ elemental chlorine, to afford the intermediate of the formula:

R ~ ~-Cl ~ ~ CH (VI) ~`c ~0, ~ .

. _, wherein R8 is as hereinbefore defined and R4 is as herein-before defined except that any free hydroxy group is pro-tected by a suitable hydroxy protecting group. The step :

lS typically conducted in a suitable organic solvent at temperatures of about -30 to 0C. Particularly suitable solvents are those such as methylene chloride~ chloroform, carbon tetrachloride, toluene and xylene. Preferably, a nitrogen atmosphere is also used. The elemental chlorine is typically added as a solu~ion having a concentration of 0.5 to 5M in a suitable organic solvent, e.g~, carbon tetrachloride.
Ozonolysis of the intermediate of formula VI
then affords the intermediate of the fomula VII:
H ~:
~Cl IVII) wherein R8 is as hereinbefore defined and R4 is as herein-before defined except that any free hydroxy group is pro tected by a suitable hydroxy protecting group~ This ozono-lysis is typically conducted at low temperatures, e.~., about -80 to about -40C in a non-polar, organic solvent.
Most preferably, the same solvent is utili7ed for this step 10 as for the previous step of the instant process. A par-f ticularly suitable solvent is methylene chloride but others, such as chloroform, or xylene, may also be used.
Reaction of the intermediate of formula VII with a nucleophile:of the formula III results in the compound 15 of formula IV. Typically, this reaction is conduct~d at temperatures of about -78C to room temperatures, with the former being most particularly preferred.
The anion of formula (IIIb) i5 prepared in situ b~ treatment of the compound of the formula \ C / 2 17 VIII~
~S ~ 9~ ~ ~6 wherein Rl, R2, R'6~ R'~ and n are as hereinbefore defined with a s~rong ~ase such as sodium or potassium hydroxide and carbon disulfide or carbon oxysulfide, respectively Sui~able solvents are those su~h as methanol, ethanol, isopropanol, etc. Typically the reaction is conducted at room t~mperature. The thiol of formula VIII is pre-pared by reduction of the corresponding disulfide.
Typically, the reduction is conducted at 0C in methanol with zinc-hydrochloric acid.
The nitrogen of the lactam of formula IV is then reacted with an ester of glyoxylic acid to afford the compound of formula IX: ~ R
1 \ C / 2 NHR17 ( R ~ ~ ~ S (C~2) - ~ ~ - C~ ~'6 Z

\ / ~IX) '~

//\
~ \oP~
wherein Rl, R2, R'~, R'7, Z and n are as hereinbefore defined and R~ is as hereinbefore defined except that any 15 -free hydroxy group is protected by a suitable hydroxy --pxotecting group, and Pg is a suitable carboxy protecting group.
In a highly preferred embodiment, the carboxy and amino protecting groups will be allyl and an allyloxy-carbonyl group, respectively, so as to provide the inter-mediates of the formula \ C / 2 NHC-O

J ~ ~ 'S ~S (~2) n - ~ ~R4~
~ (IXa) wherein Rl~ R2, Z and n are as hereinbefore defined and R4 is as hereinbefore defined except that any free hydroxy group is protected by a suitable hydroxy protecting group.
10This reaction is usually preferably oonducted at reflux temperatures in a non-polar aprotic solvent ~ such as tetrahydrofuran or benzene. Reaction times of 2-10 hours are generally typical.
The compound of formula IX is then treated with a chlorinating or brominating agent9 e.g., thionyl chloride~

methanesulfonyl chloride, thionyl bromide, or phosphorus tribromide, in the presence of an equivalent vf an acid acceptor~ e.g., pyridine or triethylamine, so as to afford replacement of the hydroxy group in the l-glyoxylate function and to produce the compound of formula X:

6~

1 \ / R~ ~HR~7 ~ CH 9 - CH - CO R 6 R~ 2 ~ (X) Cl ~Br) Q ~q wherein Rl, R2, R'6, R'7~ Pg, Z and n are as hereinbefore defined and R4 is as hereinbefore defined except that any free hydroxy group is protected by a suitable hydrokypro-tecting group. Suitable solvents are those such as methyl-ene chloride, tetrahydrofuran or benzene. Temperatures ofabout 0-20C and reaction times of 10-60 minutes are generally preferred.
The chloride or bromide of formula X is then reacted with a suitable phosphine, e.q., tri-~-methoxy-phenyl phosphine, tributylphosphine or,most preferably,triphenylphosphine to afford a compound of the formula II.
Typically, the reaction is conducted at room temperature in a polar, aprotic solvent such as hexamethyl-phosphoramide or dimethylfoxmamide. Reaction times ~enerally vary from about 12-48 hours.
Alternatively, in this synthetic procedure, when trimethoxyphosphine or sodium diphenylphosphinate is used in place of e.~. triphenylphosphine the corresponding dimethoxyphosphonate or diphenylphosphonate is obtained.
Treatment of this phosphonate with a base such as sodium hydride in a polar solvent (dimethylformamide~
results in an unisolated intermediate of the structure \ Cl - ~CH2)n 6 ~ POPh2 . COOPy which is also embraced by formula (II).
The cyclization of a compound of formula II is generally conducted atreflux temperatures in an organic solvent such as benzene, toluene or xylene under an inert ( ~ atmosphere, e.~., nitrogen or argon. Reaction times generally vary from 12-48 hours.
Removal of the protecting groups from the so- -obtained compounds results in the products of formula I.
The conventional amino protecting groups, e.g~, benzyl-oxycarbonyl, ~-nitrobenzyloxycarbonyl and benzhydryloxy-carbonyl, and carboxy protecting groups, e.~/ benzyl, ~-nitrobenzyl and benzhydryl, can be removed by hydrogena-tion. Certain hydroxy protecting groups such as trichloro-- l g ~

ethoxycarbonyl may be removed by deprotection via zinc/
acPtic acid in a suitable aprotic solvent such as tetra-hydrofuran. Mos~ Dreferably, howev~r, the allyl and allyloxycarbonyl protecting groups will be utili7ed for carbo~ and amino groups. This group is most preferably removed by the procedure of Tsuji described in Tetrahedron letters, 7, 613 (1979). The Tsuji deprotection procedure utilizes an amine salt of formic acid and a mixture of a palladium compound and triphenyl phosphine as the catalyst.
This deprotection method is particularly suitable~for the sensitive beta-lactam carboxylates of this invention.
The amino group of the compounds of formula I
wherein R7is hydrogen may optionally be converted to their corresponding compounds wherein R7 is a Schiff's base, for instance, as in U.S. Patent No. 4,172,144, or to the compounds wherein R7 is an amidine or guanidine, NH
e.g., where the amino group is converted to the -NH-C=~H
group~ as described in ICAAC, 11th International Congress of Chemotherapy, l9th Interscience Conference on Antimi-crobial Agents and Chemotherapy, Boston, October 1-5, 1979, Papers 231 and 232 and Belgian Patent 848~545~
The compounds o~ formula (I) wherein R is a meta~olisable ester group such as phthalidyl or pivaloyl-oxymethyl are prepared by reaction of the corresponding compound wherein R is an alkali metal cation with the corresponding halide such as chlorophthalide or pivaloyl-ox~nethyl chloride in a solvent such as dimethylformamide.
Rreferabl~, a catalytic amount of sodium iodide is added.
Compounds preparable by the above reaction schemes include the following representative compounds of this invent.ion each together with its enantiomer when pre,ared from racemic starting materials, and alone when prepared from chiral intennediatesr The most h.ighly preferred stereochemical isomers, i.e., the 5R, 6S, 8R, 2tS isomers when n is zero and the 5R, 6S, 8R, 2'R isomers when n is 1 to 4, however, the corresponding isomers may be prepared by choice of suitable starting compounds:

2'S)-sodium 2-[(2~ ~ ino-2'-carboxyethyl2thio]-2-penem-3-carboxylate;
2'R~-soaium 2-[(2'-amino-2'~carboxypropyl)thio~-2-penem-3-carboxylate;
~2'S)-sodium 2-[(2'-amino-2'-carboxy-3',3'-dimethylethyl~
thio]-2-penem-3-carboxylate;
(Z'S)-sodium 2-~(2'-ace~ylamino-2'-carboxyethyl)thio)-2-penem-3-carboxylate;
(2'S)-sodium 2-[(2'-amino-2'-methoxycarbonylethyl)thio¦-2-penem-3-carboxylate;
(2's)-sodium 2-[(2~-amino-2lphenoxycarbonylethyl)thi 2-penem-3-carboxylate;
(2'S)-sodium 2-[(2'-amino-2'-benzyloxycarbonylethyl)-thioI-2-penem-3-carboxylate;
~2'R)-sodium 2-~(2'-amino-2'-carboxybutyl)thio I -2-penem-3-carboxylate;
c (5R,6S,8R,2'S)-2-[~2'-amino-2'-carboxyethyl)thio]-6-(l-hydroxy ethyI)-2-penem-3-carboxylic acld, pyridinium or.
sodium salt;
(5R,6S,8R,2'R)-2-1(2'-amino-2'-carboxypropyl)thio~-6-(l-hydroxyethyl)-2-penem-3-carboxyl.ic acid, pyridinium or sodlum salt;
(5R,6S,8R,2'S)-2-[(2'-acetylamino-2'-carboxyethyl)thio]-6-(l-hydroxyethyl)-2-penem-3-carboxylic acid, pyridinium or sodium salt;

- 22 ~

(5R,6S,8R,2'S)-2-[t2 9 -amino-2' methoxycarbonylethyl)thio]-6-(1-hydroxyethyl)-2-penem-3-car~oxylic acid, pyridinium or sodium salt, (5R,6S, 8P~J 7 's~-2-~(2'-amino-2'-phenoxycarbonylethyl)thio]-6-(1-hydroxyethyl~-2-penem-3-carboxylic acid, ~yridinium or sodium salt;
(5R,6S,8R,2's)-2-[(2'-amino-2'-benzyloxycarbonylethyl) r ~ thio]-6-(1-hydroxyethyl3-2-penem--3-carboxylic acid, pyridinium or sodium salt;
(5R~6sr`BR/2~s~-2-[(2~-amino~2~--carboxy-3~3~-dimethylethyl) thio]-6-(1-hydroxye~hyl)-2-penem-3-carboxylic acid, pyridinium or sodium salt;
(5P~,6S,8R,2'R)-2-[(2'-amino-2'-carboxy-4'-methylpronyl) thio]-6-(1-hy~r~xyethyl)-2-penem-3-carboxylic acid, pyridinium or sodium salt;
(5R,6S,PR.7^R)-2-[~2'-amino-2'-carboxybutyl)thio~-6-. ~l-hydroxyethyl)-2-penem-3-carboxylic acid~ pyridinium or sodium salt;
(5R,6S,8R,2'S)-2-[(2-'methylamino-2'-carboxyethyl)thlo]-2~ 6-(1-hydroxyethyl)-2-penem-3-carboxylic acid, pyridinium or sodium salt, (5R,6S,8R,21s)-2-[(2'-phenylamino-2'-carboxyethyl)thio3-6-~l-hydroxyethyl)-2-penem-3-carboxylic acid, pyridinium or sodium salt;
15R~6s~8R,2~s)-2-[(2i-benzylamino-2~-carboxyethyl) thio3-6 (l-hydroxyethyl)- -penem-3-carboxylic acid~ pyridinium or sodium salt;

- 23~

~5R,SS,8R,2's)-2-[~N-ethoxycarborlyl-2'-amino-2'-carboxy-ethyl)thio~-6-(1-hydroxyethyl~-2-penem-3-carboxylic acid,pyri.dinium or sodium salt l5R,6s~8R~2~s)-2-[(N-2~2i2-trifluoroacetyl-2~amino-2l-carhoxyethyl)thio]-6-(1-hydroxyethyl)-2-penem-3-carbox-ylic acid, pyridini~m or sodium salt;
15p~6sr8R,2's)-2-l(N-guanidino-2l-amino-2~-carboxyethyl) r thio]-6-(1-h~xyethyl)-2_penem-3-carboxylic acid, -. pyridinium or sodium salt;
.. . .
(5R,6S,8R,2's)-2-[(~--trichloroethoxycarbonyl-2'-a~ino-2'-car-boxyethyl~thiol-6-(1-hydroxyethyl)-2-penem-3-carboxylic acid, pyridinium or sodium salt;
(5R,6S,8R,2'S)-2-1(N-t-butoxycarbonyl-2'amino-2' carboxy-ethyl) thio]-6-~1-hydroxyethyl)-2-penem-3-carboxylic acid, pyridinium or sodium salt;
(5R,6S,8R,2'S)-2-[(N-p-nitrobenzoxycarbonyl-2'-amino-2'-carboxyethyl)thio]-6-(1-hydroxyethyl~-2-penem-3-carboxylic acid, pyridinium or soaium salt;
(5R,6S,8R,2'S)-2-[(N-benzyloxycarbonyl-2'-amino-~'-- carboxy ethyl) thio ]-6-(1-hydroxyethyl)-2-penem-3--carboxylic acid~ pyridini~ or sodium salt;
(5R,ÇS,8R,2'S) 2-[(N-ethoxycarbonyl-2'-amino-2'-methoxy-carbonylethyl3thio)-6-(1-hydroxyethyl)-2-penem-3-carboxylic acid,pyridinium or.sodium sal-t;
(5R,6S,8R,2's)-2-~tN-3"-methyl-2"-butenoatemethylester-2'-amino-2'-carboxyethyl)thio ]-6-(i-hy~roxvethyl)-2-penem 3-carboxylic acid, pyri~inium or sodium salt;

- 2~

t5R,65,8R,2~s~-2-[(N-1-(3-oxocyclohex-1-enyl)-2~-amino-2'-carboxyethyl)thio ]-6-~1-hydroxyethyl)-2-penem-3-carboxylic acidl pyridinium or sodium salt;
(5R,6S,8R,2's)-2-[(N-2-(4-oxopent-2-enyl)-2'-amino-2'-carboxyethyl)thio]-6-~1-hydroxyPthyl)-2-penem-3-carboxylic acid, pyridinium or sodium salt;
(5R,6S,2's)-sodium-2--[(2't~mino-2'--carboxyethylJthio]-6-hydroxymethyl-2-penem-3-carboxylate;
(5R,6S,8R,2'S)-sodium-2--[(2'-amino-2'-carboxyethyl)thio~-`- 10 6-(1-hydroxypropyl)-2-penem-3~carboxylate;
~ (5R,6S r 8R,2's)-sodium-2-[(2~-amino-2~-carboxyetnyl)thio~-6-[1-hydroxy-1-(4-pyridyl)methyl~-2-penem-3-carboxylate;
(5Rr6S,8Rr2'SJ-sodium-2-~(2'-amino-2'-carboxyethyl)thiol~-(~pha-hydrox~7benzyl)-2-pene~r3-carboxylate;
(5Rr6S,8R~21s3-sodi ~ 2-[(2'-am~K~2'-carboxyethyl)t~io]-6-~ rdroxy-2-~2-thienyl)eth~l]-2-~enem-3-carboxylate;
(5P~r6S r 8Rr2~R)-2-[(2~-acetylamino-2~-carboxypropyl)thio]-6-~1-hydroxyethylJ-2-penem-3-carboxylic acid, pyridinium (~' or sodium s~lt;
(5Rr6S r 8Rr2'R)-2-[(2'amino-2'-methoxycarbonylpropyl)thio]
6-(1-hydroxyethyl)-2-penem-3-carboxylic acid, pyriainium or sodium salt;
15R,6s~8R~2~sJ-2-[(2~-N-D-alanyl-2~mino-2~-carboxyethyl3 thio]-6-(1-hydroxyethyl)-2-penem-3-carboxylic acid, pyridinium or sodium salt;
(5R,6s~8R~2's)-2-[(2~-a~x~2~-(2"-carbo~yethyl~-carbam~yl~
ethyl)thio]-6-(1-hydroxyethyl)-2-penem-3-carboxylic acid,~yridinium or sodium salt; and - 2~

(5R,6S~8~,2's)-2-[(~'-amino-2'-carhamoylethyl)thio]-6-(l-hydroxyethyl)-2-penem-3-carboxyllc acid,pyridinium or sodiwn saltO

This same series can also be prepared in the following con-figurations (5R,6S,8S,2'R) when n=o or (5R,6S,8S,2'S) when n~o, (5R,6S,8S,2'S) when n=o or (5R,6S,8S,2'R) when n~o, or (5R,6S,8R,2'R) when n=o or (5R,6S,8R,2'S) when n>o.

The following Examples illustrate the invention. Through-out these examples, "~lR7' denotes nuclear magnetic reson~ -ance spectra; "rotationl' denotes optical rotation of thecompounds in a suitable solvent; "~1S" denotes mass spectra;
"W" denotes ultraviolet spectra; and "IR" denotes infrared spectra. Chromatography is performed on silica gel un-less otherwise denoted.

EXAMPLE I
A(i~ To a solution of 100 g 6-~-aminopenicillanic acid in 1200 ml 2.5 N sulfuric acid is added 150 g sodium bromide. To the stirred solution at 0C is added simultan-eously 40 g sodium nitrite in 150 ml water and 40 ml bxomine.
The addition is completed in 10 minutes, maintaining the temperature at 0 to 5 C. The mixture is then stirred rapidly for 1 hour, then filtered. The filter cake is washed with water and taken up in 600 ml ethyl acetate.
The ethyl acetate solution is washed with water, cold dilute sodium bisulfite solution and then again with - ~6 water. After drying over anhydrous sodium sulphate, the solvent is removed under vacuum to afford 67 g in 85:15 ra~io (by NMR data) of 6,6-dibromopenicill~nic acid and 6a-bromopenicillanic acid. ~R: 1728 cm 1 and 1800 cm 1 (chloroform solution) NMR: ~=5.7, lH, s; ~=4.5, lH, s;
~= 1.55-1.67, 6H (CDC13)~
(ii) To a solution of 67g in 85:15 ratio of 6,6-dibromopenicillanic acid to 6O-bromopenicillanic acid in 500 ml dimethylformamide at 0C is adaed 37.3 g finely powflered potassium carbonate. The solution is stirred 5-10 minutes and 38.3 g methyl iodide is added. The reaction mixture is then stirred or 2 hours allowing thP temperature to come to ambient. The reaction is followed by thin layer chromatography eluting with methylene chloride, When complete, the reaction is decanted and the solvent removed under high vacuum to r leave 100 ml o~ solution. To this is added 600 ml ethyl acetate. The solution is then washed with water, - dried over anhydrous sodium sulphate and concentrated 20 under vacuum to afford 63 g crude methyl ester. Sub-sequently, 48 o of pure methyl 6,6-dibromopenicillanate is isolated from this crude product by high pressure liquid chromatography eluting with methylene chlorideO
NMR: 6=5 7, lH, s; ~=4.48, lH, s; ~=3.73, 3H, s;
~=1.42, 3H, s; ~=1.59, 3H, s (CDC13).

~ 2~ -(iii) To a solution of 13.7 g methyl 6,6-dibromopenicil-lanate in 250 ml dry ~etrahydxo~uran at -78~ und~r nitrogen is added 14.7 ml of ~M methyl magnesium bromide in ethyl ether. After stirring for 30 minutes at -78C, 8 g of fresh~y distilled acetaldehyde is added and stirring continued for 45 minutes. The reaction mixture is warmed to -20C at which time 50 ml 1 M potassium phosphate monobasic is added and stirring continued for 5 minutes.
The reaction mixture is then poured into 1 liter cold ethyl acetate and washed once with 150 ml brine solution and twice with 150 ml water. The ethyl acetate layer is separated, dried over anhydxous sodium sulfate and evapor-ated under vacuum. The products, methyl 6 a-bromo-6 ~ hydroxyethyl)penicillanate and methyl 6 ~-bromo-6 a-(l-hydroxyethyl) penicillanate, are detected by thin layer chxomatog~y eluting with 10% ethyl acetate/
chloroform.
, (iv) ~o a solution of ~.0 g methyl 6-bromo-6-(1-hydroxyethyl)penicillanate -in 280 ml 95% ethanol is added 800 mg 10% palladium on calcium carbonate. The solution is shaken under 2 ats hydrogen pressure for 5 hours. Disappearance of starting material is followed by thin layer chromatography eluting with 20% ethyl acetate/chloroform. The catalyst is filtered and 100 ml 1 M potassium phosphate buffer at pH 7 is added. The - ~8 ~

precipitate formea is filtered and washed with ethanol.
The ethanol is removed under vacuum and 200 ml ethyl acetate added. ~fter washing twice with 50 ml water, and drying over anhydrous sodium sulfate, the ethyl acetate is removed under vacu-~ to afford a crude mixture oE methyl 6-(1-hydroxyethyl)penicillanate. Column chromatography of 1~ g of said mixture eluting with 20%
ethyl acetate affoxds 6.4 g methyl (5R,6S,8R)-6-tl-hydroxyethyl)-penicillanate.
NMR: ~ = 2O4-2.7~ lH, d; ~ = 4.41~ lH, s;
o = 3.74, 3H, s; 6 = 3.2-3.33, lH;
= 1.25-1.35, 3H, d; ~ = 1.44, 3H~ s;
~ = 1.61, 3H, s ~CDC133.

(v) ~o a solution of 6.2 g methyl (5R,6S~8R~-6-- 15 (l-hydroxyethyl)penicillanate in 60 ml. dry methylene ,-- chloride at O~C under nitrogen is added 3.8 ml pyridine then 3.3 ml ~ -trichloroethylchloroformate. The reaction is stirred 15 minutes until all starting material is reacted ~as determined by thin layer chromatography with 20% ethyl ace-tate/chloroform). The solution is poured into 250 ml cold methylene chloride and washed twice with cold 10~ phosphoric acid solution, once with cold dilu-te sodium bicarbonate, and then with water~
Aft~r drying over anhydrous sodium sulfate, the solvent is removed under vacuum to afford 10.0 g methyl 15R,6S/8R)-6~(1-trichloroethoxycarbonyloxye-thyl)penicillanateO

- ~9 -NMR: ~ = 5.13-5~16, 1~, d; ~ = 4.78, 2H~ s;
o - ~.43, lH, s; ~ = 3.76, 3H, s;
o = 3.38-3.58, lH; ~ = 1.45-1 63, 9H (CDC13).

~vi) a. To a solution of 9.1 g methyl ~5R,6S,8R)-6-(1-trichloroethoxycarbonyloxyethyl)penicillanate in 350 ml distilled methylene chloride at -20C under nitrogen , - is added 62.3 ml of 1 M chlorine/carbon tetrachloride solution~ The reaction is stirred for 15 minutes at about -20C ~until found to be complete by thin layer chromato-graphy eluting with chloroform). The solution is evaporatcd under vacuum to afford 10.0 g of product comprising (3S,4R,5R)~ (2-methyl-1-methoxycarbony])prop-1-enyl3-3-(1-trichloroethoxy carbonyloxyethyl)-4-chloroazetidin 2-one.
IR: 1720, 1770-1790 cm 1 (chloroform solution3 NMR: ~ = 5.79-5.81, lH, d; ~ = 4.75, 2H, s;
~ = 3.74, 3H, s; o = 2.27, 3H, s; ~ = 2.0, 3H, s, o = 1.45-1.54, 3H, d (CDC13).

b. Through a solution of 7.7 g crude (3S,4R,5R)-1-[2-methyl-1-methoxycarbonyl-prop-1-enyl]-3~ trichloro-ethoxycarbonyloxyethyl)-4-chloroazetidin-2-one in ~50 ml methylene chloride at about -78C is passed ozone for 45 minutes. (Disappearance of starting material is followed by thin layer chromatography eluting with chloroform).
The reaction is allowed to sit for 1 hour at -78C with excess ozone. Nitrogen is therl bubbled in for 3-5 minutes and then 3 ml dimethylsulfide is added. The solution is allowed to warm to ambient temperature and held for 2 hours. Nitrogen is bubbled ~hrough the solution to remove excess dimethylsulfide. Optionally, the s~lvent may be removed and the residue purified by chromatography to afford (3S,4~,5~)-[1-(2-methoxy-1,2-dio.xoethyl~]-3-(l-trichloroethoxycarbonyl-oxyethyl )-4-chloroazetidin-2-one.
NMR: ~ = 5.97-6.0, lH, d; ~ = 5.76, 2H, s;
= 4.93, 21l, s; J = 1 cps, ~ = 1.45-1.55, 3H, d.

B. By substantial repetition o~ the process described in Example lA, utilizing the appropriate starting materials, the following compounds o~ the formula are prepared: -- 4~ Cl B4 . B8 ~ _ N CH3 TCEO ¦ CH3 1H -C~3 R O ~
TCEO
' CH - - -C~3 TCEO

~ C 2 ~ TCE = trichloro-- ethoxycarbonyl - 31 ~
CH3CH2~ -~H3 TCEO
CH - ~H - -CH3 EXAMPLE
.
(~ A(i) Bis ~N-allyloxy arbonyl)-L-cystine bis-allyl ester A solution of L-cystine (12 g) in a 4N sodium hydroxide (25 ml) at ice bath temperature is stirred while allyl chloroformate (10.6 ml) and ~ N sodium hydroxide (25 ml) are added dropwiseO The mixture is stirred for 30 mins.
after the final addition and is then washed with 50 ml of ether. The aqueous phase is then acidified to pH 2 with lN hydrochloric acid and extracted with 3 x SO ml ether. The ether extracts are dried with sodium sulfate ~; 10 and evaporated. The residual colorless oil is dissolved in acetone 175 ml) containing triethylamine ~.6 ml) and stirred while allyl bromide ~6.0 ml) is added drop-wise. The mixture is stirred overnight, diluted with ethylacetate ~75 ml) and brine (75 ml). The aqueous phase is extracted three times with ethyl acetate. The organic extracts are washed with lN sodium hydroxide, lN hydrochloric acid, water, dried with sodium sulfate and evaporated. The title product is crystallized from ether-hexane as colorless needles~ with a m.p. of 47-48C

and an [a~D of ~55 (chloroform~.

(ii) _ llyloxycarbonyl-I.-cysteine allyl ester A suspension of zinc dust (8 q) in a solution of bis (N-allyloxylcarbonyl)-L-cystine bis allyl ester (7.56 g) in methanol (~0 ml) at O~C is stirred vigorously while adding concentrated hydrochloric acid (5 ml) in one portion. After 2 minutes the mixture is diluted with ice water and ~xtracted with 3 x 50 ml of chloroform. The extracts are dried over sodium sulfate and evaporated und~r reduced pressure to afford the title product.

B~i~ Bis (N-allyloxycarbonyl)-D-cystine bis allyl ester Following the procedure described in step A~i) utilizing D-cystine as starting ma~erial there is obtained the title produc$, having a melting point of 48-49C and an ~~, 15 ~]D = -55 (chloroform).

(ii) N-allylox~carbonyl-D-cysteineallyl ester A suspension of zinc dust (5~18 g) in a solution of bis (N-allyloxycarbonyl)-D-cystine bis-allyl ester ~5.18 g) in methanol (50 ml~ at 0C is stirred vigorously while adding concentrated hydrochloric acid ~3.5 ml) in one portion. Aft~r two minutes, the mixture is worked up as in the above step A~ to af~ord the title product.

C. _a ~ 1 ester A solution of D-cystlne (12 g) in 4N sodium hydroxide (25 ml) is stirred at 0 while N-allyloxycarbonylsulfanilyl chloride (30 g) and 4N sodium hydroxide (25 ml~ is added dropwise. The mixture is stirred for 30 minutes, acidified with lN hydrochloric acid, extrac~ed with ether and the extract evaporated. The residual oil is dissolved in acetone (75 ml) containlng triethylamine (9.6 ml) and stirred while allyl bromide (6.0 ml~ is added dropwise.
This mixture is stirred overnight, diluted with ethyl acetate and the oraanic layer is washed with lM sodium hydroxide, lN hydrochloric acid, brine, dried over sodium sulfate and evaporated to afford bis N-allyloxycarbonyl-sulfanyl-D-cystine bis allyl ester. Treatment of the bis compound with zinc dust according to the procedure of step A(ii) affords the title compound.

, D. ~N-methyl-N-allyoxycarbonyl)-D-cysteine allyl ester A solution of bis ~N-allyloxycarbonyl)-D-cystine bis allyl ester (~.8 g) in dimethyl sulfoxide ~40 ml) is added to a solution of sodium hydride (0.5 g) in dimethylsul~oxide ~40 ml). The reaction is stirred under nitrogen while adding methyliodide (5 ml). After 15 minutes the mixture is diluted with ice/water, extracted with ethylacetate and -extracts are washed with br-ine, dried over sodium sulfate and evaporated to afEord bis (N-methyl-N-allyloxycarbonyl~-D-cystine bis allyl ester. Treatment oE this bis compound - 3~ -according to the procedure of step A~ii) affords the title compound.

E. ~-acetyl-D-cysteine allyl es$er A solution of bis-N-acetyl D-cystine ~3.2 g) in acetone 130 ml) containing triethylamine (4,0 g) is stirred with allyl bromide (4 ml) for 24 hours. The mixture is -- diluted with water, washed with lN sodium hydroxide, lN
hydrochloric acid, brine, dried over sulfate and evapor-ated to afford bis N-acetyl-D-cystine bis allyl ester.
Treatment of this bis compound according to the procedure of step A(ii) affords the title compound.

A. The N-allyloxycarbonyl-L-cystei~ allyl ester ~~) (prepared as in Example 2. A~ii) is dissolved in ethanol (170 ml) and to this solution is added with stirring lN
sodium hydroxide ~30.9 ml) followed after 1 minute by carbon disulfide (30 ml). The resulting yellow solution is stirred for 1 mlnute and 4-acetoxyazetidin-2-one (3.00 g) is added in one portion. After 2 minutes the reaction mixture is diluted with ice-water and is extrac-ted with 4 x 50 ml chloroform~ The extract is dried over sodium sulfate and evaporated under reduced pressure.
The residue is crystallized from ethyl acetate hexane to 3~

afford 4-[(2~(R)-allyloxycarbonylamino-2'-carboxyethyl-thio allyl est~r)carbonothioylthio~azetidin-2-one as yellow needles (5 g~ m.p~ 107-108C with the following spectra.
IR: 5-62, 5.81, ~;
W: 235 m,~l (2900); 300 (11900);
NMR: 2.95 (lH,dd, J=15, 3 cps); 3.86 (l~',ddJ~=15, 5 cps) 3.86 (2H,m).

B. A solution of 4-[(2'lR)-allyloxycarbonylamino-2'-carboxyethylthio allyl ester)carbonothioylthio~aze,idin-2-one 15-7 g) and allylglyoxylate ~2.06 g~ in benzene (50 ml~ is refluxed for 90 minutes, cooled to room temperature, diluted with ether (50 ml), washed with water (2 x 25 ml~, dried over sodium sulfate and evaporated under reduced pressure. The resulting 1-(allyloxycarbonylhydroxymethyl)-4-1(2'- ~)-allyloxy-carbonylamino-2'-carboxyethylthio allyl ester)c2rbonothioyl-thio]azetidin-2-one is dissolved in methylene chloride (50 ml). The solution is cooled to 0C and chlorosulfonyl-chloride (1.68 ml) followed dropwise by triethylamine(3.01 ml) are added with stirring. After 15 minutes, the reaction mixture is diluted with ether (50 ml) and washed sucessively with dilute hydrochloric acid, water and brine. The organic layer is filtered through a silica gel column (30 g) and this column is washed with methylene chloride until the effluent is colorless. The column washings are evaporated under reduced pressure and the resulting l-(allyloxycarbonylchloromethyl)-4-[~2'(R)-2-allyloxycarbonylarnino-2'-carboxyethyl~hiO allyl ester) carbonothioylthio~azetidin-2-one is aissolved in dimethyl-formamide (30 ml) followed by addition of triphenyl-phosphine (5.7 g). The reaction mixture is allowed to stand 16 hours at r~om temperature under nitrogen~ and is then diluted with ethylacetate (100 ml), ether (100 ml) and 10~ sodi~m bicarbonate (50 ml). The organic layer is washed with 10% sodium bicar~onate, water, brine, dried over sodium sulfate an~ concentrated to 100 ml and chromatographed on 200 g silica gel. The column was eluted with ether~ Fractions that were homogeneous by t.l.c.
(40% ethylacetate-hexane) are combined to afford l-(allyl-oxycarbonyl-[triphenylphosphoranyl]methyl)-4-[~2'(R~-- allyloxycarbonylamino-2'-carboxyethylthio allyl ester) carbonothioylthio]a~etidin-2-one 15-7 g) as a yellow powder with the following spectra:
IR: 5 72, 5.82 ~
W: 301 m,~ (13300) C. A solution of phosphorane prepared in step B
(2 g) ln benzene (100 ml) if refluxed for 48 hrs. and then evaporated under reduc~d pressure. The product is chrornatographed on 60 g silica gel. Elution with 40~
ethylacetatehexane affords allyl 2-[~2'(R)-2'-allyloxy-; - ~7 -carbonylamino-2'-~arboxyethylthio allyl ester~-2-pen~m-3-carboxylate as a colorless oil with the following spectra:
IR: 5 55, 5.80 ~
~ W: 256 m,~ (4500~; 330 m,~ (5000) NMR: 3~9 (lH, dd, J-15, 2cps), 3.8 (lH,ad,J=l5, 4 cps) 3.5 t~Htm) MS M+ 454 D. To a solution of the allyl ester prepared in lO step C (o.2 g~ in methylene chloride (6 ml) and l ~
pyridinium formate in methylene chloride (5 ml) is add~d tetra (triphenylphosphine) palladium (lO0 mg) and triphenylphosphine (lO0 mg). The solution is stirred under nitrogen for ~ hours. The precipitate formed is collected by centrifugation and resuspended in methylene chloride centrifuged three times. The washed precipitate, 2-[(2'R)-(2'-amino-2'-carboxyethyl)thio]-2-penem-3-- carboxylate, pyridinium salt, is then stirred for 5 .. . . .
minutes in o.5 M sodium 2-ethylhexanoate (2 ml) and washed .. . ..
by centrifugation with ethylacetate, followed by e~her and dried to afford sodium 2-[(2'P~)-(21-amino-2'-carboxyethyl3thio-2-penem-3-car~oxy-late as a pale tan powder t having an IR: 5.62, 6~22 ~

- 3~ -E~AMPLE 4 A. (3S,4R,5R)-3-[1'-Trichloroethoxycarbonyloxyethyl~-.
4-[(2l(S)allylo~ycarbony__mi~ -2'-carbo~eth~lthio all~y~
ester)-carbonothioylthio]Azetidin-2--one N-Allyloxycarbonyl-D-cysteine allyl ester (prepared as in Example 2 B(ii) is dissol~ed in ethanol (130 ml) and to this solution is added with stirring lN NaOH (20O8 ml) followed after one minute by carbon disulfide (26 ml).
The,resulting yellow solution is stirred for two minutes, cooled to 78C and added in one lot to a precooled solution (-78C~ of (3S,5R)-3-(1'-trichloroethoxycarbonyl-o~yethyl)-4-chloro-1-methyloxalyl-azetidin-2-one (4.26 g) in ethanol t60 ml). The reaction mixture is stirred at -78~C until thin layer chromatography (40% ethylacetate/
- ' hexane)-indicates completion of reaction. The reaction -- 15 mixture is then diluted with ice/water, extracted with ethyl acetate several times and the extracts are washed with brine, dried over sodium sulfate and evaporated under reduced pressure. The crude product is chromatographed on silica gel (90 g). Elution with 20~ ethyl acetate/
hexane affords the title compound as a yellow resin, IR: (nujol) 5.6, 5.7, 5~8 ~;

la] ~ 139~ (chloroform) MMR (CDC13) 1.5 (d, 3H, J = 6cps~ , - 3.42 ldd, lH, J = 2.7 cps) 5-~5 Id, lH, J - 2 cps) B. Allyl-(3S,4~,5R)-3 ~ trichloroethoxycarbonyl-oxyethyl)-4-[2'(S)allyloxycarbonx~__ino-2'-carboxyethyl thioallyl ester car~onothioylthio]-2-a2etidion -1-yl-2"-triD~henylrJhosphine acetate Following the procedure of Example 3, the title compound is obtained as a yellow glass, [a3D + 100.3 (chloroform) IR: 5.68, 5.80 ~

C. Allyl-~5R,6S,8R)-2-[2'(S)allylox~carbon~lamino-2'-carboxyethylthio allyl ester]-6-(l'trichloroethoxy-carbonyloxyethyl)-2~penem-3~carboxylate Allyl-(3S,4R,5R~-3-~(1'-trichloroethoxycarbonyloxyethyl)-4-~2'(s)-allyloxycarbonylamino-2'-carboxyethyl thio allyl ester) carbono-thioylthio]-2-a~etidinon-1-yl-2"-triphenyl-phosphine acetate (18 g) in benzene (150 ml) is refluxed - for nine days, evaporate~-and chromatoqraphed on silica ---~ gel (30 g). Elution with 20~ ethylacetate~hexane affords the title compound (0.92 g) as colorless oil, having 1]D + 111.6~ (chloro~orm);
IR (nujol1 5.58, 5.70, 5.80 ~; and NMR ~CDC13) : 1.55 Id, 3H, J = 7 cps) 3.45 (d, 2H, J = 5 cps~ -3.90 (dd, 1~, J = 2.0 cps) 5.65 (d, lH, J = 2 cps~

D. Allyl-[5R,6S,8R) 2-[2'(s~allyloxycarbonylamino-2'-carboxyethylthio allyl ester]-6-(1-hydroxyethyl).2-penem-3-carboxylat _ ~o a solution of allyl-(5R~6s~8R)-2-[2~(s~allyloxycarbonyl-amino-2'carboxyethylthio allyl ester]-6-(1-trichloroethoxy-carbonyloxyet~yl)-2-penem-3-~carboxylate (0.82 g) in a mixture of tetrahydrofuran (8 ml), water (1 5 ml) and glacial acetic acid (4 ml) cooled to 20C, is added zinc dust in three lots (3 x 300 mg~ during 15 minute int~rvals.
The reaction mixture is stirred at -20C for 3 1/2 hours, diluted with ethyl acetate, filtered and washed with brine, then with brine and 10% sodium bicarbonate solution, again with brine, dried over sodium sulfate and evaporated.
The residue is crystallized from ether-hexane as color-less rosettes, (0.52 g) to give the title product having a m.p. of 107-109DC, an [u]D= ~102 (chloroform~, and NMR (CDC13): o 1.35 (d, 3H, J = 6 cps) 3.~6 ~d, 2H, J = 5 cps~
3.70 (dd, lH, J = 2.7 cps) 5.60 (d, lH, J = 2 cps) E. Pyridinium i5R,6S,8R,2'S)-2-[2'-amino-2'-carboxy-ethylthio]-6-.tl-hydroxyethyl)-2-pene~-3-carboxylate A sol~ltion of the title compound of paragraph D (100 mg) in 1 M pyridinium formate solution in dichloromethane J~

(3 ml~ and 1 M pyridine in dichloromethane (0~25 ml~ is stirred under nitrogen. To this solution is added triphenylpho~phine (85 my~ and ~etrabis(triphenylphos-phine)palladium (85 mg). The reaction mixture is stirred at room temperature for 1.5 hours and the precipitate of the title compound is isolated by centrifuging and washinq with methylene chloride, ether, as a light tan powder (75 mg), ha~ing la]D ~ 123 (84~ ethanol);
IR: (nujol) 5.60~ 6.1 ~; and NMR: (d6DMSO~: 1.15 (d, 3H, J = 6 cps) 3.75 (dd,lH, J = 1.5,7 cps) 5.68 td, lH, J = 1.5 cpsj F. Sodium (5R,6S,8R,2'S) 2-[2'-amino-2'-carboxy-. .
ethylthio]-6-(1-hydroxyethyl)-2-penem-3-carboxylate A suspension of the-title compound of para~raph E (75 mg) is stirred for five minutes in 0.5 M ethyl acetate solution of sodium 2-ethylhexanoate (2 ml) and washed by centri-fusation with ethyl acetate ~ollowed by ether and dried to afford the title compound as a pale tan powder, having;
IR: 5.60, S.2 ~.

.
EX~PLE 5 A. - Pyridinium (5R,6S,8R,2'R)-2-[t2'-amino-2'-car~oxy-_ eth~ thio]-6-(1-hydroxyethyl)-2-penem-3-carboxylate Following the procedures of paragraphs A-E of Example 4 - ~2 -and using N-allyloxycarbonyl-L-cysteine allyl ester, the title compound is obtained as a light tan powder~ having:
IR: 5.63, ~
la]D ~ 118~ (60~ ethanol) B. (5R,6S,8R,2'S3-2-~(2'-acetimidoyl-2'-carboxyethyl) thio_]-~-(l.-hydroxyeth~ 2-~enem-3-carboxylate disodium -salt `~- A solution of pyridinium (5R,6S,8R,2'R)-2-[~2'-amino-2'-carboxyethyl)thi~-6-(1-hyaroxyethyl)-2-penem-3-carboxylate 1~ (75 mg) in 0.5 M sodium 2-ethylhexano~te in water (2 ml) is treated with ethylacetimidate (100 mg) at 20C. The solution is chromatographed on Dowex 50 x 4 t~at form), eluted with water; and fractions containing title compound are lyophilized to give the ~itle compound with . IR: .5.60 ~. .

, C. (5R,6S,8R,2'S)-~-[(2'-guanidoyl-2'-carboxyethyl) thio]-6-~1-hydroxyethyl)-2-Denem-3-carboxvlate disodium salt A solution of pyridinium ~5R~6s~8R~2~s~-2-~l2~ ino-2~-carboxyethyl)thio]-6-~1-hydroxyethyl3-2-penem-3-carboxylate (75 mg) in o 5 M sodium 2-ethylhexanoate in water (2 ml) and S-benzylisothiourea hyarochloride ~50 mg) is stirred at room temperature. The solution was chromatographed on Amberlite 401-S ~sodium form), eluted with water and fractions containing title compound are lyophilized to give the title compound with IR: 5.60 ~. .

D. (5R,6S,8R,2'S)-2-~(2'-~ethyl-3n-aminoyl-but-2"-. _ enoate)-2'-carb x~e~hyl thio]-6-~1-hydroxyethyl)-2=penem-3-carboxylate disodium salt . .
A solution of pyridinium (5R,6S,8R,2'S)-2-[~2'-amino-2'-carboxyet}lyl)thio~-6-(1-hydroxyethyl)-2-penem-3-carboxy-late (100 mg) in 0.5 H sodium 2-ethyl hexanoate in water (0.5 ml) and ethyl acetoacetate (130 mg) is stirred at room temperature for several hours and then washed with ethyl acetate. The ayueous layer, upon lyophilization, affords the title compound having IR: 5.60 ~

E. ~5R,6S,8R,2'S)-2-[(2'-sulfanilamidoyl-2'-carboxy-ethyl)thio]~-(l-hydroxyethyl)-2-?enem-3-car~oxylate -sodium salt Using N-allyloxycarbonylsulfanyl-D-cysteine allyl ester, the procedures of paragraphs A-F of Example 4 are re-peated to afford the title compound.

F. (5R,6S,8R,2'S)-2-~2'-benzazamethinyl-2'-carbox~
2~ ethyl)thio]-6-(l-hydroxyethyl)-2-penem-3-carboxylate disodium salt A solution of pyridinium (5R,6S,8R,2'S)-2- L (2'-amino-2'-- 44 ~

carboxyethyl3thio~-6-~1-hydroxyethyl)-2-penem-3-carboxylate (100 mg) in o.5 ~1 sodiurn 2-ethylhexanoate in methanol (0.5 ml~ and benzyldehyde ~200 mg) is stirred at room temperature for several hours, diluted with water, washed with ethyl acetate and the aqueous layer is lyophilized to afford the ti-tle compound.

G. (5R,6S,8R,2'S)-2-[(2'-methylamino-2'-carboxy- `
ethyl)thio]-6-(1-~droxyethyl)-2-~enem-3-carboxylate sodium salt Repetition of the procedure detailed in paragraphs A-F
of Example 4 utilizing (N--methyl-N-allyloxycarbonyl)-D-cysteine allyl ester affords the title compound.

H. (SR,6S,8R,2'S)~2-[(N-carbobenzyloxy-2'-amino-2'-carboxyethyl)thio]-6-(1-hydroxyethyl)-2-penem-3-carboxylate disodium salt A solution of pyridinium (5R,6S,8R,2'S)-2-~(2'-amino-2'-carboxyethyl)thio]-6-~1-hydroxyethyl)-2-penem-3-carboxylate (100 mg) in o.5 M sodium 2-ethylhexanoate (2 ml) is stirred at 0C with benzylchloroforrnate (0 2 ml)~ The reaction is washed with ethyl acetate and aqueous solution is chromato-- graphed on-Amberlite 401-S (sodium form). Yractions containing the title cornpound are lyophilized to give the pure title compound.

_ ~5 ~

1. Sodium ~5R,65,8R,2'S)-2-[(2'-acetylamino-2'-carboxyethyl)thio]-6-(1-hydroxyethyl3-~-penem-3-carboxylate disodium salt . . . _ _ Substanti.al ~epeti~ion of -the procedure oE para~ra~hs A-F
of Example 4 utiliz.Lng N-acetyl~D-cystine allyl ester affords the title compound~

Claims (10)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. Process for preparing a compound of the formula:
(I) wherein n is 0 to 4;
R is hydrogen, an alkali metal or quaternary ammonium cation or a metabolisable ester group;
R1 and R2 are independently hydrogen or lower alkyl, R4 is hydrogen, lower alkyl or a group of the formula R5CHOH- with R5 being hydrogen, lower alkyl, aryl, aralkyl, heteroaryl or heteroaralkyl;
R6 is amino, lower alkylamino, an ?-aminoacid residue bonded through the ?-nitrogen atom or the group -OR8, with R8 being hydrogen, lower alkyl, allyl, aryl, aral-kyl, an alkali metal or quaternary ammonium cation or a metabolisable ester group;
R7 is hydrogen, lower alkyl, lower alkoxycarbonyl, aryl, aralkyl, araloxycarbonyl, arylsulfonyl, acyl, or, to-gether with the N-hydrogen, the grouping wherein either R9 is aryl and R10 is hydrogen, lower alkyl or aralkyl; or R9 is hydrogen, amino or mono-or dilower alkylamino and R10 is amino, mono- or di-loweralkyl amino, lower alkyl, aryl, aralkyl or lower alkoxycarbonyl; and 1,3-dicarbonyl adducts at the 2'-amino group when R7 is hydrogen, which comprises cyclising a compound of the formula (II)) wherein Z is sulfur or oxygen and n, R4, R1 and R2 are as defined above,any functional group therein being optionally protected; Pg is a carboxy-protecting group;
R'6 is protected amino or protected lower alkylamino or the group -OR8,with R8 being lower alkyl, allyl, aryl, aralkyl or a carboxy-protecting group; R'7 is loweralkyl, loweralkoxycarbonyl, aryl, aralkyl, aral-koxycarbonyl, arylsulfonyl or an amino-protecting group;
and Y is a phosphonio group being double bonded to the adjacent carbon atom or a phosphonato group with a single bond to the adjacent carbon atom,the negative charge of which is compensated by the presence of a cation;
if required, separating a mixture of diastereoisomers before or after removing any protecting group,and then subjecting a so-obtained compound to one or more of the facultative steps (i) to (vi)-(1) formation of a salt or a metabolisable ester group representing substituents R and R6;
(ii) introducing the residue of the ?-aminoacid representing substituent R6;
(iii) separation of a mixture of enantiomers (iv) introducing acyl representing substituent R7 at the 2'-amino group' (v) introducing the grouping =CR9R10 representing R7 together with the N-hydrogen; and (vi) formation of a 1,3-dicarbonyl adduct at the 2'-amino group when R7 is hydrogen.

2. A process as defined in claim 1, wherein in the compound of formula II R? is an amino protecting group or loweralkoxycarbonyl and R? is protected amino or the group -OR8 with R8 being loweralkyl, allyl, or a carboxy protecting group and wherein one or more of facultative steps (i) to (iv) are carried out if neces-sary, so as to produce a compound of formula I in which R7 is hydrogen, loweralkoxycarbonyl or acyl (the latter being selected from ?-amino residues) and R6 is amino, an ?-aminoacid residue bonded through the ?-nitrogen atom or the group -OR8, with R8 being hydrogen, lower-alkyl or an alkali metal. or quatenary atom.

3. A process as defined in claim 19 wherein in the compound of formula II R4 is optionally protected 1-hydroxyethyl and the stereochemistry is 3S, 4R, 5R, whereby there is produced a compound of formula I in which R4 is 1-hydroxyethyl and which has the stereo-chemistry 5R, 6S, 8R.

4. A process as defined in claim 1, 2 or 3, wherein in the compound of formula II n is zero and R1 and R2 are both hydrogen.

5. A process as defined in claim 1, 2 or 3, wherein in the compound of formula II the stereo-chemistry at the 3, 4 and 5 position is 3S, 4R, 5R
and the carbon atom to which the group R7 -NH- is attached, has the 'S' stereoconfiguration.

6. A process as defined in claim 1 or 2 wherein in the compound of formula II R4 is optionally protec-ted 1-hydroxyethyl, n is zero, R1 and R2 are both hydrogen, the stereochemistry at the 3, 4 and 5 posi-tion is 3S, 4R, 5R and the carbon atom to which the group R? -NH- is attached has the 'S' configuration.

7. A process as defined in claim 1, wherein in formula II R4 is optionally protected 1-hydroxyethyl, n is zero, R1 and R2 are both hydrogen, R7 is an amino protecting group and R6 is the group -OR8 in which R8 is a carboxy protecting group, said compound of formula II including the stereoisomer 3S, 4R, 5R, 2'S and optionally other stereoisomers, the process including the facultative step (i) and if necessary step (iii) whereby there is produced the compound (5R,6S,8R,2'S) -2-[(2'-amino-2'-carboxyethyl)thio]-6-(1-hydroxyethyl) -2-penem-3-carboxylic sodium salt.

8. A process according to claim 1 or 7, wherein the cyclisation of the compound of formula II is con-ducted at reflux temperatures in an inert organic sol-vent, preferably benzene, toluene or xylene, under an inert atmosphere.

9. A compound of formula I as defined in claim 1, or a 1,3 dicarbonyl adduct thereof, whenever prepared by the process of claim 1 or an obvious chemical equi-valent thereof.

10. The compound defined in claim 7, whenever produced by the process of claim 7, or an obvious chemical equivalent thereof.