NO170015B - INTERMEDIATES FOR THE MANUFACTURE OF ANTIBACTERIAL BETA LACTAMES. - Google Patents

Description

The present invention relates to intermediate products for use in a method for the production of a new family of β-lactam antibiotics.

It has been discovered that the /3-lactam nucleus can be biologically activated by a sulphonic acid salt substituent which is attached to the nitrogen atom in the nucleus.

/3-lactams with a sulfonic acid salt (including "inner salt") substituent in the 1-position and an acylamino substituent in the 3-position exhibit activity against a variety of gram-negative and gram-positive bacteria.

The preferred members of the new family of β-lactam antibiotics prepared according to the invention are those covered by the formula:

The invention encompasses the production of /3-lactams with a sulfonic acid salt (including "inner salt") substituent in the 1-position and an amino substituent in the 3-position.

The compounds of this type have the formula:

These compounds are intermediates that can be used for

preparation of corresponding 3-acylamino compounds.

As they are used in the formulas above throughout the description

are the symbols as described below.

R 1 is acyl;

R 2 is hydrogen or alkoxy of 1 to 4 carbon atoms;

R 3 and R 4 are the same or different and are each hydrogen or C -C alkyl.

M is hydrogen or a cation.

The /3-Lactam intermediates are usually prepared according to the invention by introducing a sulfonic acid substituent (a sulfo group -SO3~) on the nitrogen atom in the 1-position in the /3-lactam nucleus. This sulphonation reaction is easily carried out by treating the β-lactam with a sulfur trioxide complex or with an equivalent sulphonation reagent such as chlorosulfonate.

The most commonly used sulfur trioxide complexes are pyridine-sulfur trioxide; lutidine sulfur trioxide; dimethylformamide-sulfur trioxide; and picoline sulfur trioxide. Instead of using a preformed complex, the complex can be formed in1 situ, e.g. using chlorosulfonyl-trimethylsilyl ester and pyridine as reagents. Alternatively, the suphonation can be carried out via an intermediate compound such as e.g. by first silylating the nitrogen atom of the /3-lactam nucleus and then subjecting the silylated compound to a silyl exchange reaction with trimethylsilyl chlorosulfonate or a similar reagent. Examples of silylating agents are monosilyl trifluoroacetamide, trimethylsilyl chloride/triethylamine and bistrimethylsilyl trifluoroacetamide.

In general, the sulfonation reaction is carried out in the presence of an organic solvent such as e.g. pyridine or a mixture of organic solvents, preferably a mixture of a polar solvent such as e.g. dimethylformamide and a halogenated hydrocarbon such as e.g. dichloromethane.

The product which is formed first in the sulphonation reaction is a salt of the sulphonated β-lactam. When pyridine-sulfur trioxide is the sulfonating complex, the first product formed is the /3-lactam sulfonated pyridinium salt of the sulfonated /3-lactam where M<+> in the formula below is the pyridinium ion:

These complexes can be converted to other sulfonic acid salts using conventional techniques (eg ion exchange resins, crystallization or ion pair extraction). These conversion techniques are also applicable to the purification of the products. Conversion of the pyridine salt to the potassium salt using potassium phosphate or potassium ethyl hexanoate; to the tetrabutylammonium salt using tetrabutylammonium hydrogen sulfate; or to a zwitterion (M<+> = hydrogen) using formic acid; are particularly applicable.

It should be understood that the sulfonation reaction which introduces the sulfo group on the nitrogen atom of the j8-lactam core can be carried out in the presence of various stages of the synthesis, including introduction before formation of a /3 -1 act amkj erne, where such a procedure is followed as indicated below. The sulfonation reaction is carried out in the presence of solvents described earlier and usually at room temperature. When the amino function is present, it preferably takes place with a protected amino function.

Using a benzyloxycarbonyl protecting group as an example, the sulfonation reaction can be visualized as follows:

Other protecting groups can be used to protect the amine function, e.g. a t-butyloxycarbonyl group, a simple acyl group such as acetyl or benzoyl or phenylacetyl, a triphenylmethyl group, or by having the amino function in the form of an azide group.

Azetidine intermediates where R2 is hydrogen and at least one of R3 and R4 is hydrogen can also be prepared from amino acids with the formula:

(at least one of R3 and R4 is hydrogen). The amino group is first protected with a classical protecting group; e.g. t-butoxycarbonyl (hereafter referred to as "Boe"). The carboxyl group of the protected amino acid is then reacted with an amine salt of the formula: where Y is alkyl or benzyl, in the presence of a carbodiimide to give a compound of the formula:

(at least one of R3 and R4 is hydrogen). The hydroxyl group in a compound of formula XIV is converted to a leaving group (V) with a classical reagent, e.g. methanesulfonyl chloride (methanesulfonyl hereafter referred to as "Ms"). Other leaving groups (V) that can be used are benzenesulfonyl, toluenesulfonyl, chlorine, bromine and iodine.

The fully protected compound of the formula: (at least one of R3 and R4 is hydrogen) is ring-closed by treatment with a base, e.g. potassium carbonate. The reaction is preferably carried out in an organic solvent such as e.g. acetone, under reflux conditions, and gives a compound of the formula:

(at least one of R3 and R4 is hydrogen).

Alternatively, the cyclization of a compound of formula XIV can be carried out without first converting the hydroxyl group into a leaving group. The treatment of a compound of formula XIV with triphenylphosphine and diethyl azodicarboxylate gives a compound of formula XVI wherein at least one of R 3 and R 4 is hydrogen.

Removal of the protecting group from the 1-position in an azetidinone of formula XVI can be accomplished by reduction with sodium when Y is alkyl, giving an intermediate of formula:

(at least one of R 3 and R 4 is hydrogen) . If Y is benzyl, catalytic (e.g. palladium on charcoal) hydrogenation will first give the corresponding N-hydroxy compound, which on treatment with titanium trichloride gives an intermediate of formula XVII where at least one of R3 and R4 is hydrogen.

Synthesis involving cyclization of the type described above results in inversion of the stereochemical configuration of the R3~ and R4~ substituents.

As previously mentioned, the above azetidinone can be sulfonated to form a compound of the formula:

(at least one of R3 and R4 is hydrogen).

An alternative method for preparing a compound of formula I where R2 is hydrogen and at least one of R3 and R4 is hydrogen uses an amino acid amide with

the formula:

as starting material (at least one of R3 and R4 is hydrogen). Protection of the amino group with a classical protecting group, e.g. benzyloxycarbonyl (hereafter referred to as Z) or Boe, and conversion of the hydroxyl group to a leaving group (V) such as e.g. Ms, gives a compound with the formula:

(at least one of R3 and R4 is hydrogen), where A is a protecting group.

Sulfonation of a compound of formula XX gives a compound of formula:

(at least one of R3 and R4 is hydrogen).

Cyclization of a compound of formula XXI is carried out with a base, e.g. potassium carbonate. The reaction is preferably carried out in a mixture of water and an organic solvent

(e.g. a halogenated hydrocarbon such as 1,2-dichloroethane)

under reflux conditions and provides a connection with

the formula:

(at least one of R3 and R4 is hydrogen).

Removal of the protecting group from a sulfonated azetidinone of formula XXII, where A is a protecting group, as well as the corresponding compounds previously described with an alkoxy group as R , by catalytic hydrogenation, gives a

2

connection with the formula:

(at least one of R3 and R4 is hydrogen), where R2 is hydrogen or alkoxy which can be converted into the corresponding zwitterion with the formula:

(at least one of R3 and R4 is hydrogen) by treatment with an acid such as e.g. formic acid.

Removal of the protecting group from a sulfonated azetidinone of formula XXII where A is a Boc protecting group, using acidic conditions (eg, use of formic acid) gives the corresponding zwitterion of formula XXIV.

An excellent source for the β-lactam starting materials are the 6-amino-penicillanic acids and the 7-aminocephalosporin acids which may optionally have a 6-alkoxy or 7-alkoxy substituent, respectively. These compounds have the formulas:

respectively, where R 2 is hydrogen or alkoxy and R 1 is hydrogen or acyl. By using methods described in the literature, 3-amino-2-azetidinones can be prepared; see for example Chem. Soc. Special Publication No. 28, page 288

(1977); The Chemistry of Penicillins, Princeton Univ. Press, page 257, and Synthesis, 494 (1977).

First, sulfur is removed from the 6-amino-penicillanic acid or the 7-amino-cephalosporanic acid by reduction with Raney nickel. The reaction can be run in water under reflux conditions; the resulting compound has the structural formula:

Replacement of the carboxyl group in the compound of formula XXVI with an acetate group followed by hydrolysis gives a 3-amino-3-alkoxy-2-azetidinone of formula I where R^ is hydrogen or acyl, R^ is hydrogen or lower alkoxy and R^ and R4 is hydrogen. Treatment of a compound of formula XXVI with cupric acetate and lead acetate in an organic solvent (eg acetonitrile) replaces the carboxyl group with an acetate group. Hydrolysis of the resulting compound can be carried out using potassium carbonate in the presence of sodium borohydride.

Introduction of a sulfo group in the 1-position in the above 3-amino-3-alkoxy-2-azetidinone can be carried out by reacting the intermediate with a complex of dimethylformamide and sulfur trioxide.

A 3-azido-2-azetidinone starting material can be prepared by first reacting an olefin of the formula:

with a halosulphonyl isocyanate (preferably chlorosulphonyl isocyanate) of the formula: XXCIII o = C = N.-SO2 halogen to give an azetidinone of the formula:

Reductive hydrolysis of an azetidinone of formula XXIX yields an N-unsubstituted fi-lactam of the formula:

For a more detailed description of the above reaction sequence, reference can be made to the literature; see for example Chem. Soc. Rev., 5, 181, (1976) and J. Org. Chem., 35, (1970).

An azido group can be introduced into the 3-position of an azetidinone of formula XXX (or the sulfonated equivalent) by reaction between the compound and an arylsulfonyl azide (such as toluenesulfonyl azide) to obtain a starting azetidinone of the formula:

The reaction proceeds best by first protecting the azetidinone nitrogen with a silyl residue (e.g. t-butyldimethylsilyl or t-butylphenylsilyl), then generating the anion at the 3-position of the core with a strong organic base (e.g. lithium -diisopropylamine) at low temperature and then treat the anion with toluenesulfonylazide. The resulting intermediate is cooled with trimethylsilyl chloride, and subsequent acid hydrolysis or fluoride solvolysis of the N-protecting group gives the compound of formula XXXI.

Alternatively, the compound of formula XXXI can be obtained by first reacting a primary amine of the formula:

with an aldehyde of the formula R3CH=0 to give the corresponding Schiff base. A [2 + 2] cyclization addition with an activated form of -azidoacetic acid gives a 3-azido-2-azetidinone of the formula: where Q is:

Oxidative removal of the Q-substituent gives the compound of formula XXXI.

The 3-Acylamino-2-azetidinones can be obtained by first reducing a 3-azido-2-azetidinone of formula XXXI to obtain the corresponding 3-amino-2-azetidinone and then acylating the 3-amino-2-azetidinone.

As previously mentioned in the cases where R2 is lower alkoxy, the product can be prepared from the corresponding product where R2 is hydrogen. Chlorination of the amide nitrogen in a non-alkylated compound gives an intermediate with the formula:

Reagents and methods for N-chlorination of amides are known in the field. Examples of reagents are tert,-butyl hypochlorite, sodium hypochlorite and chlorine. The reaction can be carried out in an organic solvent (eg a lower alkanol such as methanol) or in a two-phase solvent system (eg water/methylene chloride) in the presence of a base such as sodium borate decahydrate. The reaction is preferably carried out at a reduced temperature.

The reaction between an intermediate of formula XXXI and an alkylating agent, e.g. alkali metal alkoxide, gives a product of formula I where R 2 is alkoxy, in combination with its enantiomer. The reaction can be carried out in an organic solvent, e.g. a polar organic solvent such as dimethylformamide, at reduced temperature.

An alternative synthesis for the preparation of the compounds of formula I where R 2 is alkoxy comprises first alkoxylating an intermediate of formula VI where R 2 NH is a carbamate (e.g. R 2 is benzyloxycarbonyl) and R 2 is hydrogen and then introducing a sulfo- group in the 1-position of the resulting compound. Chlorination of a compound of formula VI using the procedure described above (for chlorination of a non-alkylated compound of formula I to give a compound of formula XXXII) gives an intermediate of formula:

By using the alkoxylation procedure described above (for converting a compound of formula XXXII to a product of formula I), and then adding a reducing agent such as e.g. trimethylphosphite, the compound of formula XXXIII can be converted into an intermediate of the formula:

in a combination with its enantiomer.

The above processes give the products of formula I where R 2 is alkoxy as a racemic mixture. If desired, the enantiomer with the R configuration can be isolated from the racemic mixture using conventional techniques such as fractional crystallization of a suitable salt with an optically active amine or by ion-pair chromatography using an optically active cation.

The following examples are specific embodiments of the present invention.

Example 1

(S)-2-oxo-3-[[(phenylmethoxy)carbonyl]amino]-1-azetidine sulfonic acid- pyridine salt (1:1).

Method I:A) 1-[(1R)-Carboxy-2-methyl(propyl)]-2-oxo-(3S)-[[(phenylmethoxy)carbonyl]amino]azetidine.

A slurry of 6-aminopenicillanic acid (12.98 g, o.o6 mol)

in 14o ml of water containing 5.18 g of sodium bicarbonate (stirred for about lo minutes without complete dissolution) is added in one portion to a well-stirred (mechanical stirrer) suspension of Raney nickel (washed with water to pH 8.o, 26o ml slurry = 13o g) in an oil bath at 7o°C. After 15 minutes the slurry is cooled, filtered and the filtrate treated with 5.18 g of sodium bicarbonate and a solution of 11.94 g (0.07 mol) of benzyl chloroformate in 12 ml of acetone. After 30 minutes, the solution is acidified to pH 2.5

and extracted with methylene chloride. The organic layer is dried, evaporated and triturated with ether-hexane to give a total of 6.83 g of the title compound. B) 1-[(Acetyloxy)-2-methyl(propyl)]-2-oxo-(3S)-[[ ( Phenylmethoxy)carbonyl] amino] azetidine .

A solution of 6.83 g (0.0213 mol) of the above acid in 213 ml of acetonitrile is treated with 1.95 g (0.007 mol) cupric acetate and 9.5 g (0.0213 mol) lead tetraacetate. The slurry is immersed in an oil bath at 65°C and stirred using a stream of nitrogen that bubbles through the slurry until the starting materials are consumed. The slurry is filtered and the solids are washed with ethyl acetate. The combined filtrate and washing solutions are evaporated in vacuo and the residue is taken up in 10 ml each of ethyl acetate and water and adjusted to pH 7. The ethyl acetate layer is separated, dried and evaporated to give 6.235 g of the title compound.

C) ( S )-( 2- Oxo- 3- azetidinyl) carbamic acid phenyl methyl ester.

A solution of 3.12 g (o.oo93 mol) of the above acetate i

71 ml of methanol and 7 ml of water are cooled to -15°C and 1.33 g of potassium carbonate and 349 mg of sodium borohydride are added. The reaction mixture is stirred at -15 - 0°c. After the reaction is complete (approx. 2 hours), the mixture is neutralized to pH 7 with 2n HCl and concentrated in vacuo. The concentrate is adjusted to pH 5.8, saturated with salt and extracted with ethyl acetate (3 times). The organic layer is dried and evaporated in vacuo. The residue is combined with material from a similar experiment and triturated with ether to give 3.30 g of the title compound. D) (S)-2-Oxo-3-[[(phenylmethoxy)carbonyl]amino]-1-azetidine sulfonic acid pyridine salt.

Method I:

A solution of 44o mg (o.oo2 mol) of the above

azetidinone in 2 ml each of dry methylene chloride and dry dimethylformamide is stirred for 2 hours under nitrogen with 350 mg (0.oo22 mol) of pyridine sulfur trioxide complex. Most of the solvent is then removed in vacuo and the residue triturated with ethyl acetate to give 758 mg of solid, which is essentially the title compound. NMR (D20-CD30D) 3.63 (1H, d of d, ,=6.4), 3.9o (1H, t, j=6),

4.85 (1H d of d, y=6.4) , 5.lo (2H,S) 7.27 (5H,S) 8-o-9.oppm

(m's 5H);

Method II:

Chlorosulfonyltrimethylsilyl ester (18.87 g) is added dropwise at -20°C to 7.9 g of anhydrous pyridine with stirring under a nitrogen atmosphere. When the addition is complete, stirring is continued for 30 minutes at room temperature and the trimethylchlorosilane is then removed in vacuo. A solution of 2o g of the above azetidinone (Method I,

part C) in 12o ml of dimethylformamide and 12o ml of methylene chloride are added and stirring at ambient temperature is continued for 3.5 hours. The solvent is distilled off in vacuo and oil residues are crystallized by the addition of ethyl acetate, to give 31 g of the title compound. The NMR data are identical to data for the product from method I.

Example 2

(S)-2-Oxo-3-[[(phenylmethoxy)carbonyl]amino}-1-azetidine sulfonic acid potassium salt.

Method I:

(S)-2-Oxo-3-[[(phenylmethoxy)carbonyl]amino]-1-azetidine sulfonic acid pyridine salt (135 mg; see Example 2) is dissolved in 2 ml o.5m monobasic potassium phosphate (adjusted to pH 5, 5 with 2n potassium hydroxyc and applied to a 25 ml HP-2oAG column.The column is eluted with loo ml buffer, 200 ml water and 100 ml 1:1 acetone-water. Fractions (25 ml) 14-15 are highly Rydon-positive. Evaporation gives 80 mg of material

which is essentially the title compound (spectral data are identical to those obtained below).

Method II:

(S)-2-Oxo-3-[[ (phenylmethoxy)carbonyl]amino]-1-azetidine sulfonic acid pyridine salt (600 mg; see example 2) is dissolved in 2 ml of water and mixed with 15 ml of monobasic potassium phosphate buffer of pH 5, 5. A solid forms and the slurry is cooled to 0°C, filtered, washed with cold buffer, cold ethanol (50% strength), ethanol and ether to give 370 mg of the title compound (containing excess potassium ion by analysis). A solution of 280 mg of the salt in 10 ml water is applied to a 10 ml HP-20 column. The column is eluted with 2oo ml of water and then water-acetone (9:1). Fractions (50 ml ) are collected; evaporation of fraction 7 gives a solid. Trituration with acetone, filtration and drying in vacuo gives 164 mg of the title compound, m.p. 19 3-196°C.

Analysis: Calculated for 1H11N20gSK-1/2H0: C, 38.02;

H, 3.48; N, 8.06; S, 9.23; K, 11.25

Found: C, 38.19; H, 3.24: N, 8.15; S, 9.12; K, 11.53 NMR(D2q) 3.69 (1H, d, of d, , =6.4) ,3.91 (1H, t , , =6) ,

4.76(1H,m), 5.16(2H,S), 7.43 ppm (5H,S).

Method III:

(S)-(2-Oxo-3-azetidinyl)carbamic acid phenylmethyl ester (2o.o g see example 2C) is suspended in 2oo ml of acetonitrile, 21.6 ml of mono-trimethylsilyltrifluoroacetamide (25.3 g) is added and the mixture is heated to 5o° C with stirring for 1 hour. After cooling in an ice bath to 0°C, 17.2 g of trimethylsilyl chlorosulfonate are added dropwise and the solution is stirred at ambient temperature for 6 hours. 24.2 g of potassium ethyl hexanoate in 100 ml of butanol are added to the solution and stirring is continued for a further 1 hour. The slurry is poured into 1 liter of dry diethyl ether and the precipitate is filtered off and dried in a vacuum. The compound is dissolved in 500 ml of water, the pH is adjusted to 5.0 with potassium carbonate, insoluble material is filtered off and the mother liquor is freeze-dried. The yield of crude compound is 19.4 g. The compound contains small amounts of potassium chloride which is removed by chromatography. Spectral data are identical to those from method II.

Example 3

(S)-2-Oxo-3-[[(phenylmethoxy)carbonyl]amino]-1-azetidine sulfonic acid-tetrabutylammonium salt (1:1) .

Method I: (S)-2-Oxo-3-[[(phenylmethoxy)carbonyl]amino)-1-azetidine sulfonic acid pyridine salt (1:1) (34.3 g; see example 2) is dissolved in 800 ml of water. The solution is clarified with charcoal, 30.7 g of tetrabutylammonium hydrogen sulphate in 80 ml of water are added and the pH is adjusted to 5.5 with 1N potassium hydroxide. The solvent is removed under vacuum until a volume of approx. 2oo ml. The precipitated tetrabutylammonium salt is filtered off and dried in a vacuum. The compound can be recrystallized from water or dissolved in methylene chloride, filtered and precipitated by adding ether. Yield 34.3 g, m.p. 108-110°C.

Method II: (S)-2-Oxo-3-[[(phenylmethoxy)carbonyl]amino]-1-azetidine sulfonic acid potassium salt (1:1) (2o.2 g; see example 3) is dissolved in 5oo. ml of water, filtered and 20.3 g of tetrabutylammonium hydrogen sulphate in 100 ml of water are added. With ln potassium hydroxide, the pH is brought to 5.5. The volume is reduced in a vacuum to approx. loo ml and the precipitated tetra-butylammonium salt is filtered off. The compound is dissolved in 30 ml of methylene chloride, filtered and precipitated by the addition of ether, whereby 21 g of the title compound are obtained, m.p. 19-31°C.

Example 4

(S)-3-Amino-2-oxo-1-azetidine sulfonic acid tetrabutylammonium salt

(S)-2-Oxo-3-[[(phenylmethoxy)carbonyl]amino]-1-azetidinesulfonic acid tetrabutylammonium salt (2 g; see example 4) is dissolved in 10 ml of dimethylformamide and hydrogenated for approx. 31 minutes with 1 g palladium-on-charcoal (lo%) as catalyst. The catalyst is filtered off and the dimethylformamide is removed leaving the title compound as an oil. NMR (CDCl 3 ) 3.82 (1H, t, >=5.5),

4,o5 (d. 1H, d of d , y= 5.5, 2.5 eps).

Example 5

Method II:-

A) 3-Amino-3-methoxy-2-oxo-1-azetidine sulfonic acid tetrabutylammonium salt

A 4% solution of sodium borate decahydrate in methanol (100 µl) is added to a suspension of 10% palladium on charcoal (830 mg) in methanol (2 ml), and the mixture is stirred under a hydrogen atmosphere for 15 minutes. 3-Methoxy-2-opxo-3-[[(phenylmethoxy)carbonyl]amino]-1-azetidinesulfonic acid tetrabutylammonium salt (60 mg; see Example 7) in methanol (2 ml) is added and the mixture is stirred vigorously for 15 minutes under a hydrogen atmosphere . Catalyst is removed by filtration through "Celite" on a millipore filter (0.5 m/l), and solvent is removed from the filtrate in vacuo and the residue is extracted with methylene chloride. Removal of solvent under reduced pressure gives 35 mg of the title compound as an oil.

Example 6

3-Methoxy-2-oxo-3-[[(phenylmethoxy)carbonyl]amino]-1-azetidine sulfonic acid tetrabutylammonium salt.

Method I:

A) 2-Oxo-3-[N-chloro-N-[(phenylmethoxy)carbonyl]amino]-1-axzetidine sulfonic acid tetrabutylammonium salt. (S)-2-Oxo-3-[[(phenylmethoxy)carbonyl]amino]-1-azetidinesulfonic acid tetrabutylammonium salt (0.9g; see example 4) dissolved in 8 ml of methylene chloride is added to a mixture (cooled to 0-5° C) of 3.17 g of sodium borate decahydrate and 11.8 ml of a 5.15% sodium hypochlorite solution in 70 ml of water. The reaction mixture is stirred vigorously for 55 minutes while cooling in an ice bath. After diluting the mixture with 0.5 M monobasic potassium phosphate solution, the product is extracted with methylene chloride (three 150 ml portions). Combination of the extracts, drying (sodium sulfate) and removal of solvent in vacuo gives the title compound as an oil (0.94 g). B) 3-Methoxy-2-oxo-3-[[(phenylmethoxy)carbonyl]amino]-1-azetidine sulfonic acid tetrabutylammonium salt.

To a stirred solution of lithium methoxide (667 g) in anhydrous methanol (10 ml) at -78°C is added a solution of 2-oxo-3-[N-chloro-N-[(phenylmethoxy)carbonyl]amino]- 1-Azetidine sulfonic acid tetrabutylammonium salt (0.94 g) in dry dimethylformamide (10 mL). After stirring the solution at -78°C for 1 hour, it is poured into

0.5 M monobasic potassium phosphate solution and extracted with methylene chloride (three 150 ml portions). The combined extracts are dried (sodium sulfate) and solvent is removed in vacuo to

yield an oil (0.83 g). The desired product is obtained by chromatography of the oil on silica gel (100 g) and eluting with 4-5% methanol in methylene chloride to give an oil (513 mg): u max(pure)

1767, 172 cm"<1>; NMR (CDCl3) S 3.40 (S,0CH3), 3.03 (ABq, J=6.5

Hz, H4), 5.08 (S,CH2), 6.00 (S,NH), 7.27 (S, aromatic).

Method II:

To a solution of 3-benzyloxycarbonylamino-2-methoxy-2-oxo-1-azetidine sulfonic acid potassium salt (400 mg) in water is added 0.1 M tetrabutylammonium bisulfate solution (10.9 ml, adjusted to pH 4.3 with potassium hydroxide). The mixture is extracted three times with methylene chloride, the extracts combined, dried (Na 2 SO 4 ) and solvent removed in vacuo to give a foam (625 mg), with spectral characteristics similar to those of the product in method I.

Example 7

(--cis)-4-Methyo-2-oxo-3-[[(phenylmethoxy)carbonyl]-amino]-1-azetidine sulfonic acid potassium salt.

A) N-Benzyloxy-t-boc-allotreoninamide.

A solution of 6.9 g of d,1-t-boc-allotreonine and the free amine from 5.3 g of o-benzylhydroxylamine. HCl (~0.033 mol, ethyl acetate-sodium bicarbonate release) in 80 ml of tetrahydrofuran is treated with 4.82 g of N-hydroxybenzotriazole and 6.5 g of dicyclohexylcarbodiimide in 20 ml of tetrahydrofuran. After stirring for approx. After 16 hours at room temperature, the slurry is filtered, concentrated in vacuo and chromatographed on a 4oo ml silica gel column. Elution with 5-10% ethyl acetate in chloroform gives 6.8 g of the title compound in fractions (2oo ml each) 7-22. B) (--cis)-N-Benzyloxy-3-t-butoxycarbonylamino-4-methylazetidinone.

A solution of 6.8 g of N-benzyloxy-t-boc-allotreoninamide in 200 ml of tetrahydrofuran is stirred for approx. 16 hours with 5.25 g of triphenylphosphine and 3.2 ml of diethyl azodicarboxylate. The solvents are evaporated in vacuo and the residue is chromatographed on a 500 ml silica gel column. Elution with methylene chloride followed by crystallization from ether gives a total of 2.65 g of azetidinone. Rechromatography of the mother liquors and mixed fractions gives an additional 0.6 g. Crystallization of a portion twice from ether (-2o°C) gives the analytical sample of the title compound, mp 14o-142°C.

<*>"boc" is used to describe butoxycarbonyl. ;C) (--cis)-3-t-Butoxycarbonylamino-1-hydroxy-4-methylazet idinone. A solution of 3,2 cis-N-benzyloxy-3-t-butoxycarbonylamino-4-methylazetidinone in 200 ml of 95% ethanol is stirred in an atmosphere of hydrogen with 0.7 g of 10% palladium on charcoal. After 40 minutes, the slurry is filtered (intake 249 ml) and the filtrate is evaporated and triturated with ether to give in two yields, 2.05 g of solid, melting point 134-136°C. ;D) (-- cis)- 3- t- Butoxycarbonylamino- 4- methylazetidinone. ;A solution of 2.05 g of cis-3-t-butyloxycarbonylamino-1-hydroxy-4-methylazetidinone in 6o ml of methanol is treated with a total of ;9o ml of 4.5m ammonium acetate (4o, 2o and 3o ml portions) while the other and third additions are made after 15 and 12o minutes, respectively. After 135 minutes, the solution is diluted with an equal volume of 8% sodium chloride solution and extracted with three 300 ml portions of ethyl acetate. The combined organic layer is washed with a mixture of 10 ml each of 5% sodium bicarbonate and saturated salt solution, dried and evaporated. trituration with ether gives in two yields 1.65 g of solid. A portion of the first crop is recrystallized from ether to give an analytical sample, mp 176-178.5°C. ;E) (-- cis)- 3- Benzyloxycarbonylamino- 4- methylazetidinone. A solution of 1.55 g of cis-3-5-butoxycarbonylamino-4-methyl-azetidinone in 4 ml each of methylene chloride and anisole is cooled to 0°C and 50 ml of cold trifluoroacetic acid is added. After 90 minutes, the solvents are evaporated in vacuo (benzene is added and evaporated three times). The residue is dissolved in 25 ml of acetone, the original pH (2.5) is raised to 7 with a 5% sodium bicarbonate solution and 2 ml of benzyl chloroformate is added. The solution is kept at 0°C and pH 7 for 4 hours and the acetone is removed in vacuo to give a slurry which is filtered. The filtrate is saturated with salt and extracted with methylene chloride. The solid is dissolved in methylene chloride and dried. The organic layers are combined, concentrated and the residue chromatographed on a 200 ml silica gel column. Elution with 3:1 chloroform/ethyl acetate gives 850 mg of the title compound in fractions (100 ml each) 4-11. Crystallization of a small sample from ether gives an analytical sample, melting point 165-166°C. F) (--cis)-4-Methyl-2-oxo-3-[[(phenylmethoxy)- carbonyl] amino]- 1- azetidine sulfonic acid kaium salt. ;To a suspension of cis-3-benzyloxycarbonylamino-4-methylazetidinone (0.75 g) in 7 ml each of dimethylformamide (dried with 4a sieves activated at 32o°c for 15 hours under argon flow) and methylene chloride (dried with basic Al 2 O 3 ) is added 1.66 g of pyridine-sulfur trioxide complex. After stirring for 3 hours at room temperature under nitrogen, a further amount of pyridine-sulphur trioxide complex (1.66 g) is added. The reaction mixture is then stirred at room temperature under nitrogen for approx. 16 hours. The dimethylformamide is removed in vacuo to give 4.6 g of residue which is dissolved in 300 ml of 0.5 M monobasic potassium phosphate solution (40°C for 10-15 minutes). The solution is cooled, passed through a column of HP-2o resin (3 cm x 6o cm) with 4oo ml of o.5m potassium phosphate monobasic, 1 1 of distilled water and (14:1) water:acetone to give 28o mg of product in fractions 13 to 26 (loo ml each). Crystallization from MeOH:petroleum ether gives 757.5 mg of an analytical sample, m.p. 214-215.5°C, dec. ;Analysis calculated for 2H13N2S06K: C, 4o.9o; H, 3.72; N, 7.95; ;S , 9 /lo; K , 11 ,lo , ;Found: C, 4o,43; H, 3.6o; N, 7.89; ;S, 8.69; K, lo,82. ;Example 8;(3S-trans)-4-Methyl-2-oxo-3-[[(phenylmethoxy)carbonyl]-amino]-1-azetidine sulfonic acid potassium salt. By following the procedure from example 8, but replacing d,1-t-boc-allotreonine with 1-t-boc-threonine, the title compound is obtained, melting point 133-135°C. ;Analysis calculated for ^2Hi3N206SK: c' 4o'9°; H, 3.72; N, 7.95; ;S, 9,lo; K, 11,lo, ;Found: C, 4o,72; H, 3.6o; N, 7.99; ;S, 8.8o; K, lol, 82. ;Example 9 ;A) (3S)-3-Amino-4-methyl-2-oxo-1-azetidine sulfonic acid tetrabutylammonium salt. (4S-trans)-4-Methyl-2-oxo-3-[[(phenylmethoxy)carbonyl]amino]-1-azetidine sulfonic acid potassium salt (352.4 mg; see example 9) is dissolved in 20 ml of distilled water and treated with 373.5 mg (1 mmol) of tetrabutylammonium hydrogen sulfate. After stirring for 10 minutes at room temperature, the solution is extracted three times with 10 ml portions of methylene chloride after saturation with sodium chloride. The methylene chloride is dried over sodium sulfate and evaporated in vacuo to give 536 mg of the tetrabutylammonium salt, which is hydrogenated with 270 mg of 10% palladium on charcoal in 25 ml of dimethylformamide. The mixture is filtered through Celite and washed twice with 2.5 ml portions of dimethylformamide to give the title compound. Example 10 (3S-cis)-3-Amino-4-methyl-2-oxo-1-azetidine sulfonic acid. ;A) t- Boc- allothreonine. A suspension of 6.72 g of 1-allotreonine in 7 c ml of 50% aqueous dioxane is treated with 9.45 ml of triethylamine and 18.1 g of t-butyl pyrocarbonate. The resulting mixture is stirred at room temperature for 4 hours and then diluted with 70 ml of water and 140 ml of ethyl acetate. After thorough shaking, the layers are separated and the organic layer is washed with 30 ml of 2:1 water:salt solution. Combined, aqueous layers are back-extracted with 70 ml of ethyl acetate. The aqueous layer is cooled in an ice bath and 10% potassium bisulphite solution is added to pH 2.3. The acidified solution is extracted with ethyl acetate (four 150 ml portions). Combined organic layers are dried over anhydrous sodium sulfate and solvent is evaporated to give 9.13 g of the title compound. ;B) N-Methoxy-t-boc-l- allothreoninamide. t-Boc-l-allotreonine (9.13 g) is dissolved in 85 ml of water and 41 ml of potassium hydroxide solution. Methoxyamine hydrochloride (5.22 g) and 8.67 g of 1-ethyl-3,3-(dimethylaminopropyl)carbodiimide. HCl is added. The mixture is stirred at room temperature for 4 hours and then saturated with sodium-potassium tartrate. The resulting mixture is extracted with ethyl acetate (four 150 mL portions) and the organic layer is dried over anhydrous sodium sulfate and the solvent is evaporated to give 7.38 g of the title compound as a solid. C) O- Methanesulfonyl- N- methoxy- t- boc- l- allothreoninamide. ;N-Methoxy-t-boc-1-allotreoninamide (7.32 g) is dissolved in 4o ;ml of pyridine and cooled to -2o°C under nitrogen. Methanesulfonyl chloride (3 ml) is added dropwise with a syringe over a 5 minute period. The resulting mixture is slowly heated to 0°C and stirred at this temperature for 3 hours. Ethyl acetate (500 ml) is added and the solution is washed with 250 ml of ice-cold, 3N HCl solution, then with 100 ml of 5% NaHCO3 solution. The ethyl acetate layer was dried over anhydrous sodium sulfate and the solvent evaporated to give 8.64 g of the title compound as a white solid. ;D) (3S-cis)-3-t-Butoxycarbonylamino-l-methoxy-4-methylazetidino: O-Methanesulfonyl-N-methoxy-t-boc-l-allotreoninamide (8.64 g) is dissolved in 5 30 ml of acetone and 11 g of solid potassium carbonate are added. The mixture is slowly heated to 65°C under nitrogen and stirred at this temperature for one hour. The reaction mixture is then filtered through "Celite" and the filter cake is washed with ethyl acetate. The filtrate is concentrated and the residue taken up in 25o.ml of ethyl acetate. The ethyl acetate solution is washed with 10 ml of hydrochloric acid solution and 10 ml of 5% sodium bicarbonate solution. The ethyl acetate layer is dried over anhydrous sodium sulfate and the solvent is evaporated to give 6.63 g of crude product. E) (3s-cis)-3-t-Butoxycarbonylamino-4-methylazetidinone. Sodium (1.35 g is dissolved in approx. 3oo ml of liquid ammonia; at -5o C and 5.87 g of (3S-cis)-3-t-butoxycarbonylamino-1-methoxy-4-methylazetidinone in 35 ml of tetrahydrofuran is added dropwise by syringe. Additional lo ml of tetrahydrofuran is used for rinsing. Na: the end of the addition, a further approx. nitrogen stream and 250 ml of ethyl acetate are added to the residue. After filtering and washing the solid with ethyl acetate, the solvent is removed from the combined filtrate to give 4.82 g of the title compound. ;F) (3S-cis)-3-t-Butoxycarbonylamino-4- methyl-2-oxo-l-azetidine sulfonic acid tetrabutylammonium salt. [ 3S,4R]-3-t-Butoxycarbonylamino-4-methylazetidinone (4.98 g) is dissolved in 30 ml of dimethylformamide. Pyridine-sulphur trioxide complex (11.9g) is added and the mixture is stirred at room temperature under nitrogen. After 14 hours of stirring, a further 1.8 g of pyridine-sulphur trioxide complex is added and stirring is continued for 80 hours. The reaction mixture is poured into 7oo ml o.5m monobasic potassium phosphate solution and washed with methylene chloride (three 3oo ml portions). Tetra-n-Butylammonium bisulphate (8.45 g) is added to the aqueous solution and the mixture is extracted with methylene chloride (four 300 mL portions). The combined methylene chloride layers are dried over anhydrous sodium sulfate and the solvent is evaporated to give 10.76 g of the title compound. G) (3S-cis)-3-Amino-4-methyl-2-oxo-1-azetidine sulfonic acid. (3S-cis)-3-t-Butoxycarbonylamino-4-methyl-2-oxo-1-azetidinesulfonic acid tetrabutylammonium salt (10.76 g) is dissolved in 50 ml of 95-97% formic acid and stirred for 4 hours under nitrogen . A small amount of product from a previous reaction is added as seed and the mixture is stirred for another hour. The mixture is stored in the freezer for approx. 16 hours and the frozen mixture is warmed to room temperature and stirred for a further hour. The solid formed is filtered off and washed with methylene chloride to give 982 mg of the title compound. The filtrate is diluted with 1 liter of methylene chloride and kept at -2o°C for 4 hours. The precipitate that forms is recrystallized from water-methanol-acetone to give an additional 167 mg of the title compound. ;NMR(D2o) 1.63 (3H, d, ,=6.5 eps), IR (nu jol) 1775 cm"<1>. ;Example ] 1 ;( 3S- trans)- 3- Amino- 4- methyl- 2-oxo-l- azetidine sulfonic acid♦ ;A) Threonine- methyl ester- hydrochloride. ;Under a nitrogen atmosphere, a flask with 5oo ml of methanol is cooled to -5°C (ice/salt solution) and 13o ml (excess) of thionyl chloride is added at such a rate that the reaction temperature is kept between o and lo°C. After recooling to -5°C, 59.5 g of 1-threonine is added and the mixture is allowed to reach room temperature and stirred for 16 hours. The mixture is concentrated and evaporated at lo<-1> dry for 2 hours to give a viscous oil. This material is used directly in the following step. ;B) Threoninamide. ;The crude product from part A is dissolved in 2.5 L of methanol and cooled to -5°C (ice/saline), The solution is saturated with ammonia gas, the cooling bath is removed and the successful vessel is allowed to stand for 3 days. After removal of the main amount of unreacted ammonia via aspirator, loo g of sodium bicarbonate and 5o ml of water are added and the mixture is evaporated to a viscous oil . ;C) Benzyloxycarbonylthreoninamide. ;The raw product from part B (already containing the required amount of sodium bicarbonate) is diluted to a volume of 1 liter with water. To this rapidly stirred solution, 94 g (88 ml of 90% pure material) of benzyloxylcarbonyl chloride are added as a solution in 80 ml of tetrahydrofuran over the course of one hour. The reaction mixture is then stirred for a further 16 hours and extracted with ethyl acetate (one 500 ml portion, two 250 ml portions). The combined extracts are dried over magnesium sulfate and concentrated. The crystalline residue is then dissolved in 250 ml of hot ethyl acetate and 300 ml of hexane is added followed by boiling until a clear solution is obtained. Cooling and filtering the crystalline mass gives, after drying, 104 g of the title compound. ;D) Benzyloxycarbonylthreoninamide- O- mesylate. Under an argon atmosphere, 100 g of benzyloxycarbonyl-threoninamide is dissolved in 400 ml of anhydrous pyridine and cooled in an ice/salt bath. To this stirred solution, 36.8 ml (54.5 g) of methanesulfonyl chloride are added over the course of 15 minutes. After stirring for 2 hours, a further 0.3 equivalent of methanesulfonyl chloride is added. The reaction mixture is then stirred for 1 hour and poured into a mixture of 1.5 1 ice and 2 1 water. The resulting slurry is stirred for about 30 minutes and filtered. Drying the raw product at 6o°C for approx. 16 hours gives 109 g of the title compound. E) N-Sulfonyl-benzyloxycarbonylthreoninamide-O-mesylate-tetrabutylammonium salt. ;A solution of 2-picoline (17.8 ml) in 90 ml of methylene chloride is cooled to -5°C (ice-salt solution) and chlorosulfonic acid 5.97 ml is added at such a rate that the internal reaction temperature is kept below 5°C. The resulting solution is added via a cannula to a suspension of 7.56 g of benzyloxycarbonylthreoninamide O-mesylate in 120 ml of methylene chloride. The resulting heterogeneous mixture is refluxed for approx. 16 hours to provide a clear solution. The solution is poured into 5oo ml of phosphate buffer (0.5m) with pH 4.5 and further diluted with 12o ml of methylene chloride. The separated, organic* layer is then washed once with 100 ml of buffer solution and the combined aqueous phases are treated with 10.2 g of tetra-n-butylammonium hydrogen sulfate and extracted with methylene chloride (one 300 ml portion and two 150 ml portions ). After drying the combined extracts over sodium sulfate, the solution is concentrated to

yield 12.7 g of a foam

F) (3S-trans)-3-Amino-4-methyl-2-oxo-1-azetidine sulfonic acid.

A mixture consisting of 5.52 g of potassium carbonate in 20 ml

water and 160 ml of 1,2-dichloroethane are brought to reflux and 15.5 mmol of N-sulfonyl-benzyloxycarbonylthreoninamide-O-mesylate-tetrabutyl-ammonium salt are added in 20 ml of 1,2-dichloroethane (20 ml is used for rinsing). After reflux treatment for 30 minutes, the mixture is poured into a separatory funnel, diluted with 50 ml of water and 100 ml of methylene chloride and the phases are separated. The resulting organic phase.

dried over sodium sulfate and concentrated to give crude (3S-trans)-3-benzyloxycarbonylamino-4-methyl-2-oxo-1-azetidinesulfonic acid tetrabutylammonium salt. The crude azetidinone is treated in 250 ml of ethanol with 0.8 g of 5% palladium on charcoal catalyst and hydrogen is bubbled through "Celite" with 50 ml of ethanol as rinsing liquid. Addition of 1.2 ml of formic acid to this solution causes an immediate precipitation of the title zwitterion which is filtered after stirring for 1 hour to after drying for 1 hour at lo<-1> dry give 1.1 g of product. A second yield of product is obtained by concentrating the filtrate and adding more formic acid to give 1.3 g of the title zwitterion. Temp. 218°C, split

[a) D = -41 .1 (C=l , H2O.

NMR (D 20 ) 1.58 (3H, d, )=7), 4.8o (2H, M).

Example 1 2

(-)-3-Amino-4, 4- dimethyl- 2- oxo- l- azetidine sulfonic acid,

A) (-)- 4, 4- Dimethyl- 2- oxo- l- azetidine- tert- butyl- diphenylsilane.

A solution of 40.5 ml of t-butylchlorodiphenylsilane in 112 ml of dimethylformamide is cooled to 0°C. To this is added 22 ml of triethylamine. A solution of 12.87 g of 4,4-dimethyl-2-azetidinone in 25 ml of dimethylformamide is added dropwise over the course of 10 minutes to the cooled triethylamine solution. The resulting cloudy solution is stirred for 18 minutes at 5°C under argon. This mixture is poured into 400 ml of ice water and extracted with three 150 ml portions of 2:1 ether:ethyl acetate. The combined extracts are washed with four 100 ml portions of o.5m monobasic potassium phosphate buffer, one 150 ml portion of sodium bicarbonate solution, two 150 ml portions of water and one 150 ml portion of saturated sodium chloride solution. The solution is dried over sodium sulfate and concentrated in vacuo to give 33.03 g of the title compound as a solid. B) (-)-3-Azido-4,4-dimethyl-2-oxo-1-azetidine-tert-butyl-diphenylsilane.

A solution of 4.25 ml of l.6m (in hexane) n-butyllithium and

II ml of dry tetrahydrofuran is prepared at -5o°C under argon in a 10 ml three-necked flask. A solution of 0.083 g of triphenylmethane in 1 ml of tetrahydrofuran is added. The resulting solution is cooled to -6o°C and 1.0 ml of diisopropylamine is added dropwise with a syringe. The solution is stirred for 15 minutes and then cooled to -78°C. A solution of 2.3 g of (-)-4,4-dimethyl-2-oxo-1-azetidine-tert-butyl-diphenylsilane in 8 ml of tetrahydrofuran is added slowly with a syringe. The resulting solution is stirred for 20 minutes at -78°C during which time heavy precipitation occurs so that uniform stirring becomes difficult to achieve. A solution of 1.33 g of p-toluenesulfonyl azide in 5 ml of tetrahydrofuran is added dropwise. The resulting mixture is stirred at -78°C for 20 minutes and 2 ml of trimethylsilyl chloride is added dropwise. The reaction mixture is heated to ambient temperature and stirred for 1 hour. The mixture is then cooled

to 0°C and poured into 15o ml of ethyl acetate at 0°C. Enough o.5m monobasic potassium phosphate buffer is added to ferment both the aqueous and organic layers clearly. The two layers are separated and the organic layer is washed with three 15o ml portions of 0.5m monobasic potassium phosphate solution, one 15o ml portion of sodium chloride solution, one 15o ml portion of saturated sodium chloride solution and it is dried over sodium sulfate. The solution is concentrated in vacuo to 2.83 g of oil which, when triturated with hexane, gives 1.67 g of the title compound as a solid.

C) (-)-3-Azido-4,4-dimethyl-2-oxo-1-azetidine.

In a 50 ml three-necked flask, 1.52 g of (-)-3-azido-4,4-dimethyl-2-oxo-1-azetidine-tert-butyl-diphenylsilane are dissolved in 25 ml of acetonitrile. Add 0.25 ml of 48% hydrofluoric acid to this stirred solution. This solution is stirred at ambient temperature and 0.5 ml portions of 48% hydrofluoric acid are added every 60 minutes until after 6.5 hours 3.25 ml of hydrofluoric acid has been added. The reaction mixture is then cooled to 0°C, neutralized with saturated sodium bicarbonate and extracted with 120 ml of ethyl acetate. The organic layer is then washed with 10 ml of water, 10 ml of saturated sodium chloride solution and dried over sodium sulfate. The dry solution is concentrated in vacuo to give 1.34 g of oil. This crude oil is chromatographed on silica gel with hexane followed by 33% ethyl acetate in hexane to give 0.358 g of the title compound as a solid. D) (-)-3-Azido-4,4-dimethyl-2-oxo-1-azetidine sulfonic acid tetrabutylammonium salt.

To 0.10 g of (-)-3-azido-4,4-dimethyl-2-oxo-1-azetidine at 0°C, 2.8 ml of 0.5m dimethylformamide-sulfur trioxide complex is added under argon. This mixture is warmed up to ambient temperature and stirred for 45 minutes. The solution is then poured into 2o ml o.5m monobasic potassium phosphate buffer with pH 5.5. This solution is washed with three 20 ml portions of methylene chloride (discarded) and 0.237 g of tetrabutylammonium hydrogen sulfate is added to the aqueous solution. This is extracted with four 20 ml portions of methylene chloride and the combined organic extracts are washed with 20 ml of 8% sodium chloride solution. The methylene chloride solution is dried (sodium sulfate) and concentrated in vacuo to give 0.31 g of oil which, by nmr analysis, was found to consist of 5o% dimethylformamide and 5o% title compound.

E) (-)- 3- Amino- 4, 4- dimethyl- 2- oxo- azetidine sulfonic acid.

A solution of o.155 g of (-)-3-azido-4,4-dimethyl-2-oxo-1-azetidine sulfonic acid tetrabutylammonium salt in o.6 ml of methanol is hydrogenated over lo% palladium on charcoal for 20 minutes at 1 atmosphere. The catalyst is filtered off and rinsed with methylene chloride which is combined with the methanol solution. This clear solution is treated with about 123 ml of 97% formic acid. When the acid is added, the solution immediately becomes cloudy. After standing for 1 hour at 5°C, the solid is filtered off to give 0.0664 g of the title compound, m.p. 2oo-2o2°C, (splitn.).

NMR(D20) 1.64 (3H,S), 1.68(3H,S), 4.42(1H,S),

IR (KBr] 1765 cm<-1>).

Example 13"

(3S-trans)-3-Methoxy-4-methyl-2-oxo-[[(phenylmethoxy)-carbonyl] amino]- 1- azetidine sulfonic acid potassium salt. A) (3S-trans)-4-Methyl-3-methoxy-2-oxo-4-[[(phenylmethoxy)carbonyl]amino]azetidine.

A solution of 2.5 g of (.0,olo6 mol)(3R-trans)-4-methyl-2-oxo-3-[[(phenylmethoxy)carbonyl]amino]azetidine (prepared from d-threonine in 12.6 % yield essentially as described for the racemic cis-isomer in example 98C) in 112 ml of 4% borax in methanol is cooled to 0°C and 3.5 ml of t-butyl hypochlorite is added. After 20 minutes, the solution is poured into 1 liter of cold water and extracted with two 750 ml portions of cold ethyl acetate. The organic layer is washed with cold water (two 750 ml portions), brine, dried and evaporated to give 3.05 g of crude N , N '-dichloramide.

A solution of 426 mg of lithium methoxide in 20 ml of dry methanol is cooled to -78°C and diluted with 40 ml of dry tetrahydrofuran.

Within 3o seconds, a solution of the above chloramide in 2o ml of tetrahydrofuran (-78°C) is added by means of a syringe.

After 20 minutes at -7 8°C, 2 ml each of acetic acid and trimethylphosphite are added. After 40 minutes at room temperature, the solution is poured into 500 ml of water and extracted with ethyl acetate (two 300 ml portions). The organic layer is washed with water, dried and evaporated to give an oil. Chromatography on a 2oo ml silica gel column and elution with 3:1 chloroform-ethyl acetate gives a total of 1.25 g of the title compound. B) (3S-trans)-3-Methoxy-4-methyl-2-oxo-3-[[(phenyl-methoxy)carbonyl]amino]-1-azetidine sulfonic acid potassium salt.

A solution of 8oo mg (o,oo3o3 mol) (3S-trans)-4-methyl-3-methoxy-2-oxo-4-[[(phenylmethoxy)carbonyl]amino]azetidine in 2 ml of dimethylformamide is cooled to 0°C and 4 ml of dimethylformamide-sulfur trioxide complex is added. After 1 hour at 0°C and 4 hours at room temperature, the solution is poured into 8o ml o.5m monobasic potassium phosphate (adjusted to pH 5.5) and extracted with methylene chloride (two 5o ml portions, discarded). The aqueous layer is treated with 1.04 g of tetrabutylammonium sulfate and extracted with dichloromethane to give 1.42 g of oil. This is dissolved in acetone and treated with 1.04 g of potassium perfluorobutanesulfonate in 10 ml of acetone. Dilution with 25o ml of ether and extensive trituration of the oily solid gives 584 mg of crude product. Chromatography on HP-20 AG (2oo ml) gives 418 mg of purified product in fractions (loo ml) 13-16 (elution with 1 liter of water and then 9:1 water-acetone). Trituration of 114 mg of this material with ether gives 104 mg of an analytical sample.

Analysis calculated for C13<H>14<N>2<0>7SK-H2O: C, 39.06; H, 4,04; N, 7,ol;

S, 8,o3; K, 9.78.

Found: C, 38.91; H, 3.62; N, 6.91;

S , 8,o6; K, 9.51,

NMR(D2o) 1.33(3H, d, j=7), 3.46(3H,S), 4.22(2H, d of d, ;=6) , 5.18(2H,S), 7 .43ppm (5H ,S) .

Example 1-4

(3S-trans)-3-Methoxy-3-amino-4-methyl-2-oxo-1-azetidine sulfonic acid tetrabutylammonium salt.

(3S-trans-3-amino-3-methoxy-3-amino-4-methyl-2-oxo-1-azetidine sulfonic acid tetrabutylammonium salt is prepared by catalytic hydrogenation of (3S-trans)-3-methoxy-4-methyl-2 -oxo-3-[[(phenylmethoxy)carbonyl]amino]-1-azetidine sulfonic acid potassium salt (see example 14) after conversion to the tetrabutyl ammonium salt.

Example I5

( trans)- 3- Amino- 4- ethyl- 2- oxo- l- azetidine sulfonic acid.

A) t-Boc-methoxy-ff-threoethylserinamide.

threo-D,L-/?-Ethylserine (1.33 g) is dissolved in 10 ml of 2N potassium hydroxide and 5 ml of t-butanol." After adding 2.46 g of di-t-butyl pyrocarbonate, the two-phase the mixture for 4 hours at ambient temperature. O-Methylhydroxylammonium chloride (1.25 g) is added and the pH is adjusted to 4 with 1N hydrochloric acid. 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (1.92 g) is added and the pH adjusted again to 4. After stirring for 1 hour, the reaction mixture is saturated with sodium chloride and extracted with four 50 ml portions of ethyl acetate. The ethyl acetate extracts are combined and dried over MgSO^. Removal of the solvent in vacuo gives 1 g of the title compound. B) t- Boc- O- methanesulfonyl-N-methoxy-/3-threopropionamide.

t-Boc-N-methoxy-[3-threoethylserinamide (10.5 g) is dissolved in

65 ml of pyridine. Methanesulfonyl chloride (4.65 ml) is added dropwise at 0°C. After stirring for 3 hours at ambient temperature, the reaction mixture is poured into 2oo g of ice and 3oo ml of hydrochloric acid, then the pH is adjusted to 4 with concentrated hydrochloric acid. After extraction with three 85 ml portions of ethyl acetate, the combined extracts are dried over MgSO 4

and concentrated in vacuo. The residue is treated with carbon tetrachloride and concentrated again. Stirring with ether followed by filtration gives 6.9 g of the title compound. C) (trans)-3-t-Butoxycarbonylamino-4-ethyl-1-methoxy-2-azetidinone.

Anhydrous potassium carbonate (4.15 g) and 125 ml of dry acetone are brought to reflux and 3.4 g of t-boc-O-methanesulfonyl-N-methoxy-(3-threo-propionamide) in 25 ml of acetone are added. After 1 hour, the reaction mixture is cooled and filtered, and the filtrate is concentrated in vacuo. The oil residue is stirred with hexane to give 2.2 g of the title compound. c)• ( t rans)- 3- t- But oxycarbonylamino- 4- ethyl- 2- azet idinone. (trans)-3-t-Butoxycarbonylamino-4-ethyl-1-methoxy-2-azetidinone (3 g) is added to 170 ml of liquid ammonia at -78 C under nitrogen and 1.68 g of sodium is added in 5 portions with stirring in during a 5 minute period. Stirring is continued for 3o minutes. Ammonium chloride is added slowly until the blue color in the reaction mixture disappears. After removal of ammonia under nitrogen, the solid is extracted with two 100 ml portions of ethyl acetate. Removal of the solvent followed by drying in vacuo gives 2.7 g of the title compound. E) (trans)-3-t-Butoxycarbonylamino-4-ethyl-2-oxo-1-azetidine sulfonic acid tetrabutylammonium salt. To 2 ml of absolute pyridine in 20 ml of dry dichloromethane is added trimethylsilylsulfonyl chloride (3.7 ml) in 5 ml of dry dichloromethane. The addition is carried out at -3o°C under nitrogen over a period of 10 minutes. After stirring at ambient temperature for 30 minutes, the flask is evacuated to give a pyridine-sulfur trioxide complex. (trans)-3-t-Butoxycarbonylamino-4-ethyl-2-azetidinone (2.67 g) and 20 ml of dry pyridine are added to the flask which is then placed in an oil bath heated to 90°C. After 15 minutes, a clear solution is obtained which is poured into 200 ml of a lm solution of dibasic potassium phosphate. After adding 27 g of dibasic potassium phosphate and 10 ml of water, a clear solution is obtained. The solution is extracted with two 60 ml portions of ethyl acetate. Tetrabutylammonium hydrogen sulfate is added to the aqueous layer and the aqueous solution is extracted with three 100 ml portions of dichloromethane and the combined organic layers are dried over MgSO 4 . Concentration in vacuo gives 6.9 g of the title compound. F) ( trans)- 3- Amino- 4- ethyl- 2- oxo- l- azetidine sulfonic acid. (trans-3-t-Butoxycarbonylamino-4-ethyl-2-oxo-1-azetidine sulfonic acid tetrabutylammonium salt (6.75 g) in 40 ml of 98% formic acid is stirred for 3 hours at ambient temperature. Dichloromethane (60 ml) is added and the mixture is cooled for about 16 hours in a refrigerator. The resulting precipitate is separated by filtration and then dried in vacuo to give 0.85 g of the title compound, m.p. 185°C, c.p. Example 16 [ 3S- trans]- 3- Amino- 4- cyclohexyl- 2- oxo- 1- azetidine sulfonic acid. A) α-(t-Butoxycarbonylamino)-β-cyclohexyl-β-hydroxy-threo-propionic acid. /3-Cyclohexyl-α-amino-β-hydroxythreo-propionic acid (15 g) is suspended in 150 ml of acetonitrile and 70 ml of water. Triethylamine (17.8 g) is added and the mixture is heated with stirring to 60°C. At this temperature a clear solution is obtained and 21.0 g of di-t-butyl pyrocarbonate is added and stirring at 6o°C is continued for 1.5 hours. The solvent is removed in vacuo and 50 ml of water is added. The aqueous layer is extracted with ethyl acetate at pH 2, which is adjusted by adding 3n HCl. The organic layer is separated, dried over Na 2 SO 4 and evaporated to dryness. The remaining crystalline material is filtered with petol ether to give 20.4 g of the title compound, mp 113-115°C. B) α-(t-Butoxycarbonylamino)-/3-cyclohexyl-/3-hydroxy-N-methoxy-threo-propionamide. α-(t-Butoxycarbonylamino)-/3-cyclohexyl-/3-hydroxy-threo-propionic acid (20.2 g) and 7.6 g of O-methylhydroxylamine hydrochloride are suspended in 350 ml of water and 175 ml of t-butanol. The pH of the mixture is adjusted with potassium carbonate to 4, l-Ethyl-3-(3-dimethylamino-propylDcarbodiimide (16.4 g) is added and the pH is maintained at 4 with stirring for 1.5 hours. t-Butanol is removed in vacuo and the remaining , aqueous solution is saturated with sodium chloride and extracted twice with 10 ml portions of ethyl acetate. The organic layers are combined, dried with Na 2 SO 4 and evaporated to dryness. The remaining crystals are filtered off with petroleum ether to give 18.6 g of the title compound, m.p. 125-127° C. C) a-(t-Butoxycarbonylamino)-/3-cyclohexyl-/?-(methanesulfonyl-oxy)-N-methoxy-threoporpionamide. α-(t-Butoxycarbonylamino)-/J-cyclohexyl-Ø-hydroxy-N-methoxy-threo-propionamide (18.3 g) is dissolved with stirring in 10 ml of dry pyridine. The solution is cooled with stirring to 0°C and 9.3 g of methanesulfonyl chloride are added dropwise. After one hour at 0°C, a further 3.3 g of methanesulfonyl chloride is added and stirring is continued for another hour. The solution is poured into 3oo ml of ice water, 2oo ml of ethyl acetate is added and the pH is adjusted to 3 with dilute sulfuric acid. The organic layer is separated, dried with Na2SO4 and the solvent is removed in vacuo. The remaining solid is taken up with petroleum ether to give 19.0 g of the title compound, mp 150-152°C. D) [3S-trans]-3-(t-Butoxycarbonylamino)-4- cyclohexy1- 1- methoxy- 2- azet idinone. α-(t-Butoxycarbonylamino)-O-cyclohexyl-[3-(methanesulfonyloxy)-N-methoxy-threo-propionamide (18.7 g) is dissolved in 500 ml of dry acetone. Potassium carbonate (9.8 g) is added and the suspension is heated to reflux temperature with stirring for 5 hours. The insoluble inorganic material is filtered off and the solvent is removed in vacuo and the remaining oil is dissolved in 30 ml of ethyl acetate. On addition of petroleum ether, the title compound is precipitated and filtered off (12.9 g), melting point 110-112°C. E) [3s-trans]-3-(t-Butoxycarbonylamino)-4-cyclohexyl-2-azetidinone. [3S-trans]-3-(t-Butoxycarbonylamino)-4-cyclohexyl-1-methoxy-2-azetidinone (1 g) is added to 50 ml of liquid ammonia with stirring. Sodium (0.154 g) is added in 5 to 6 portions over 5 minutes. After this time, a further amount of 0.025 g of sodium is added and stirring is continued for 5 minutes. Ammonium chloride (.o89 g) is added and the ammonia is removed. The residue is extracted with hot ethyl acetate. The organic extract is evaporated to dryness and the remaining crystals of the title compound are filtered off with petroleum ether, and 0.5 g is obtained, melting point 13o-132°C. F) [3S-trans]-3-)t-Butoxycarbonylamino)-4-cyclohexyl-2-oxo-1-azetidine sulfonic acid pyridine salt. [3S-trans]-3-(t-Butoxycarbonylamino)-4-cyclohexyl-2-azetidinone (5.3 g) is dissolved in 20 ml of methylene chloride and 80 ml of dimethylformamide. After adding 60 mmol of pyridine-sulphur trioxide complex, the solution is stirred for 6 hours at room temperature. Removal of the solvent in vacuo gives 11.3 g of the title compound as an oil. G) [3S-trans]-3-(t-Butoxycarbonylamino)-4-cyclohexyl-2-oxo-1-azetidine sulfonic acid tetrabutylammonium salt.

C3S-trans]-3-(t-Butoxycarbonylamino)-4-cyclohexyl-2-oxo-1-azetidinesulfonic acid pyridine salt (11.3 g) is dissolved in 250 ml of water. Tetrabutylammonium hydrogen sulfate (9.0 g) is added with stirring

and the pH is adjusted to 6.5 with ln potassium hydroxide. The aqueous solution

ning is extracted twice with 2oo ml portions of methylene chloride.

The organic portions are dried with Na 2 SO 4 , filtered and the solvent is distilled off to give 8 g of the title compound, melting point 135-138°C. H) [3S-trans]-3-Amino-4-cyclohexyl-2- oxo-l-azetidine sulfonic acid.

[3S-trans]-3-(t-Butoxycarbonylamino)-4-cyclohexyl-2-oxo-1-azetidinesulfonic acid tetrabutylammonium salt (3.8 g) is stirred

in 2o ml of formic acid for 3 hours, followed by the addition of 2o ml of methylene chloride. The precipitated title compound (1.0 g) is filtered off, melting point 217-219°C.

Example 17

(-) -( trans)- 3- Amino- 2- oxo- 4- phenyl- 1- azetidine sulfonic acid.

A) (-)-(trans]-2-oxo-4-phenyl-1-azetidine-tert-butyldiphenyl-silane).

A solution of tert-butyl chloride phenylsilane (20.56 g) in dimethylformamide (45 ml) is cooled to 0°C under argon and treated with triethylamine (10.4 ml) and then (-)-2-oxo-4- phenyl-1-azetidine. After several hours at 0°C, the resulting mixture is treated with additional triethylamine (1 mL) and tert-butylchlorodiphenylsilane

(2.11 g) and stirred for 65 hours at 5°C. The reaction mixture is poured into ice water (3oo ml) and extracted with 3:1 ether-ethyl acetate (three 125 ml portions). The organic extracts are washed with phosphate buffer of pH 4.5 (three 50 ml portions), saturated sodium bicarbonate solution (50 ml), water (two 50 ml portions), saturated sodium chloride solution and dried (Na 2 SO 4 ). Filtration and concentration in vacuo gives a solid which is washed with hexane to give, after drying (high-vacuum), 15 g of the title compound as a solid. B) (-)-(trans)-3-Azido-2-oxo-4-phenyl-1-azetidine-tert-butyldiphenylsilane.

A 50 ml flask equipped with a magnetic stirrer, gas inlet and septum is flame-dried under argon and charged with n-butyl lithium (0.65 ml of a 1.6m solution in hexane) which is cooled to -4o°c and dissolved in tetra -hydrofuran (2 mL). Diisopropylamine (0.16 mL) is added dropwise and the resulting mixture is stirred for 30 minutes and cooled to -78° C. A solution of (-)-(trans)-2-oxo-4-phenyl -1-azetidine-tert-butyldi-phenylsilane (400 mg) in tetrahydrofuran (1.5 ml) is added dropwise over 5 minutes. After a further 20 minutes of stirring, the solution is treated with p-toluenesulfonylazide (204 mg) in tetrahydrofuran (o, 5 ml). The resulting mixture is stirred for 10 minutes at -78°C and treated dropwise with chlorotrimethylsilane (0.4 ml). After further stirring for 10 minutes, the cooling bath is removed and the reaction mixture is stirred at ambient temperature for 2.5 hours, then add while cooling to 0°C ethyl acetate (20 ml) followed by phosphate buffer of pH 4.5 (8 ml). The organic layer is washed with additional buffer (two 8 ml portions), 5% sodium bicarbonate solution (three 10 ml portions), 50% sodium chloride solution (10 ml), saturated sodium chloride solution (10 ml) and dried (Na2SO4). Filtration and concentration in vacuo gives 500 mg of oil which is flash chromatographed with 5% ethyl acetate hexane to give the title compound (253 mg).

C) (-)-(trans)-3-Azido-2-oxo-4-phenyl-1-azetidine.

A solution of 17 g of crude (-)-(trans)-3-azido-2-oxo-4-phenyl-1-azetidine-tert-butyldiphenylsilane is dissolved in methanol (24o ml) and treated dropwise with concentrated HCl (35 ml) at 0°C. The cooling bath is removed, the reaction mixture is stirred at ambient temperature for 1 hour and cooled again to 0°C, after which saturated sodium carbonate solution is added to neutralize the reaction. The resulting mixture is extracted with ethyl acetate (one 300 ml portion and four 100 ml portions) and the organic extracts are washed with 1:1 5% sodium bicarbonate-50% sodium chloride solution, saturated sodium chloride solution and dried (Na2SO4). Filtration and concentration in vacuo gives 15 g of a heavy oil which is chromatographed on loo g silica gel with 20% ethyl acetate-hexane to give 460 mg of the title compound. D) (-)-(trans)-3-Azido-4-phenyl-1-azetidine sulfonic acid tetrabutylammonium salt.

A solution of (-)-(trans]-3-azido-2-oxo-4-phenyl-1-azetidine (3oo mg) in dimethylformamide (3 ml) is cooled to 0°C under argon and treated dropwise with a complex of dimethylformamide and sulfur trioxide (4.78 ml of a 0.5m solution in dimethylformamide). The cooling bath is removed, the reaction mixture is stirred for 2 hours at ambient temperature and poured into 80 ml of 0.5m monobasic potassium phosphate (pH 5.5). The solution is extracted with dichloromethane ( is discarded) and 541 mg of tetra-butylammonium bisulfate is added. The resulting mixture is extracted with dichloromethane and the organic extracts are washed with 10% sodium chloride solution and dried (Na2SO4). Filtration and concentration in vacuo gives 800 mg of oil; about 40% is the desired product the residue is dimethylformamide This mixture is used without purification in the next step.

E) (-)-(trans)-3-Amino-4-phenyl-1-azetidine sulfonic acid.

A solution of (-)-(trans)-3-amino-4-phenyl-1-azetidinesulfonic acid tetrabutylammonium salt in 4 ml of methanol is hydrogenated over 30 mg of platinum oxide at 1 atmosphere and room temperature. After 15 minutes, the system is evacuated and new hydrogen is introduced. After a further 45 minutes, the reaction is complete and the system is purged with nitrogen. After several days at room temperature in dichloromethanemethanol (4:1, 2oo ml) the catalyst aggregation is complete and filtration is carried out. The filtrate is concentrated in vacuo to 18 ml and 0.2 ml of 97% formic acid is added. After cooling to 5°C for several hours, the resulting solid is filtered and washed with dichloromethane to give, after drying, 150 mg

of the title compound as a solid.

Analysis calcd for C 2 H 2 N 2 S: C, 44.62; H, 4.17; N, 11.57;

P. 13,23

Found: C, 43.36; H, 4.31; N,ll,o9;

S, 13,o2.

Example 1 8

(cis)-3-Amino-2-oxo-4-(2-phenylethenyl)-1-azetidine sulfonic acid.

A) N-(3-Phenyl-2-propenylidene)-4-methoxyaniline.

p-Anisidine (12.32 g) is dissolved in 160 ml of methylene chloride and 20 g of anhydrous magnesium sulfate is added. The mixture is cooled in an ice bath and 13.22 g of trans-cinnaldehyde is added. The mixture is stirred under nitrogen for 2 hours and then filtered. The filtrate is evaporated to give a solid. The crude product is recrystallized from methylene chloride-petroleum ether to give 20.96 g of the title compound as a solid. B) (-<+>)-(cis)-3-Azido-1-(4-methoxyphenyl)-2-osco-4-(2-phenylethenyl)azetidine.

2- Azidoacetic acid (024.26 g) is dissolved in 100 ml of methylene chloride and cooled in an ice bath. 48.57 g of triethylamine and 14.24 g of N-(3-phenyl-2-propenylidene)-4-methoxyaniline dissolved in 250 ml of methylene chloride are added to this solution. To the resulting solution, 50.41 g of trifluoroacetic anhydride are added dropwise over the course of one hour. After stirring for one hour in an ice bath, the mixture is warmed to room temperature and stirred for approx. 16 hours. The mixture is then diluted with 25o ml of methylene chloride and washed with water (75o ml), 5% sodium bicarbonate solution (two 75o ml portions) and ln HCl-

solution (75o ml). The organic layer is dried over anhydrous sodium sulfate and the solvent is evaporated to give a solid. The crude product is recrystallized from ethyl acetate to give 11.39 g of the title compound as a solid.

C) (-)-( cis )- 3- Azido- 2- oxo- 4-( 2- phenylethenyl) azetidine.

To a solution of lint, 22 g of cerium-ammonium nitrate in 13 ml of water at 0°C, 1.99 g of {-)-(cis)-3-azido-1-(4-methoxyphenyl)-2-oxo-4- (2-phenylethenyl)azetidine is dissolved in 65 ml of acetonitrile over a 15 minute period (an additional 10 ml of acetonitrile is used for rinsing). The mixture is stirred for a further 15 minutes at 0°C, diluted with 750 ml ethyl acetate, washed with water (six 600 ml portions), dried over anhydrous sodium sulfate and the solvent removed to give an oil. The crude product is chromatographed on 90 g of silica gel, eluted first with 250 ml of 30% ethyl acetate/petroleum ether, then 50% ethyl acetate/petroleum ether. Fractions (5o ml each) 11-16 are combined and evaporated to give 8o2 mg

of the title compound as an oil.

D) (-)-(cis)-3-Azido-2-oxo-4-(2-phenylethenyl)-1-azetidine sulfonic acid tetra-n-butylammonium salt. (-)-(cis)-3-Azido-2-oxo-4-(2-phenylethenyl)azetidine (334 mg) is dissolved in 3 ml of dimethylformamide and 868 mg of pyridine sulfur trioxide is added. The mixture is stirred at room temperature for 4o hours under nitrogen and then poured into 2oo ml o.5m monobasic potassium phosphate solution and washed with 3o ml methylene chloride. Tetra-n-Butylammonium bisulphate (530 mg) is added to the aqueous solution and the mixture is extracted with methylene chloride (four 50 ml portions). The combined organic layers are backwashed with water (two 100 ml portions), dried over anhydrous magnesium sulfate and the solvent evaporated to give 824 mg of the title compound as a gum. E) (-)-(cis)-3-Azido-2-oxo-4-(2-phenylethenyl)-1-azetidine sulfonic acid. (-)-(cis)-3-Azido-2-oxo-4-(2-phenylethenyl)-1-azetidine-sulfonic acid-tetra-n-butylammonium salt (300 mg) is dissolved in 4 ml of tetrahydrofuran and stirred rapidly. 600 mg of zinc dust is added to the mixture, followed by 0.8 ml of a basic potassium phosphate solution. The mixture is heated to 45°C and stirred at this temperature for 3 hours. The mixture is then filtered and the filtrate is taken up in 40 ml of methylene chloride and 10 ml of water. The aqueous layer is further extracted with methylene chloride (three 40 ml portions) and the combined methylene chloride layers are evaporated to give 256 mg of a foam. This raw product is dissolved in a small amount of approx. 30% acetone/water and applied to 7.5 ml "Dowex" (K<+>) resin (0.7 meq./vnl) and eluted with 40 ml water. The eluent is evaporated to give 151 mg of foam, which is dissolved in 2 ml of water and acidified with ln HCl solution to pH 2. A small amount of acetonitrile is added to dissolve the precipitate and the : resulting solution is applied to 15 ml of HP-2o resin, eluted with 150 ml of water and then with 10% acetone/water. Fractions (15 ml each) 2-13 are combined and evaporated to give 10 mg of the title compound as a foam.

Example 19

( cis )- 3- Amino- 4-( methoxycarbonyl)- 2- oxo- l- azetidinesulfony A) [( 4- Methoxyphenyl) imino] acetic acid methyl ester.

A dry three-necked 1 liter flask equipped with a nitrogen inlet and magnetic stirrer is charged with 56.88 g of M<g>SO 4 followed by a solution of recrystallized anisidine (19.43 g) in dichloromethane (250 mL). After cooling to 0°C, a solution of methylglyoxylate hemiacetal (19.92 g) in dichloromethane (250 ml) is added over 1.5 hours. After stirring for a further 20 minutes at 0°C, the reaction mixture is filtered with suction, dried over sodium sulfate, filtered and concentrated in vacuo to a quarter volume. Hexane (3oo ml) is added and the solution is concentrated to an oil which becomes semi-solid on standing under high vacuum at 5°C. B) (cis)-3-(1,3-Dihydro-1,3-dioxo-2H-isoindol-2-yl)-4-methoxycarbonyl-2-oxo-1-(4-methoxyphenyl)azetidine.

A dry 5oo ml 3-necked coupler equipped with magnetic stirrer, feed funnel, septum and nitrogen inlet is charged with a solution of [ (4-methoxyphenyl)imino]acetic acid methyl ester (21.o9 g) in dichloromethane (15o ml) and cooled to 0°C . Triethylamine (19.2 ml) o.14 g mol is added dropwise followed by a solution of (N-phthalimido)acetyl acid chloride (28.4 g) in dichloromethane (150 ml) over the course of 1 hour.

The resulting mixture is stirred for 1.5 hours at 0°C and diluted with 2.5 l of dichloromethane. The organic solution is washed with monobasic potassium phosphate solution of pH 4.5 (two 500 ml portions), 5% sodium bicarbonate solution (two 500 ml portions), saturated sodium chloride solution (500 ml), and dried over sodium sulfate. Filtration and concentration in vacuo gives a solid which is washed with ethyl acetate, cold acetone and hexane to give 18.65 g of product. C) (cis)-4-(Methoxycarbonyl)-1-(4-methoxyphenyl)-2-oxo-3-[[(phenylmethoxy)carbonyl]amino]azetidine.

A dry 5oo ml flask equipped with nitrogen inlet, magnetic stirrer and septum was charged with 18.65 g of (cis)-3-(1,3-dioxo-2H-isoindol-2-yl)-4-methoxycarbonyl-2-oxo- 1-(4-methoxyphenyl)azetidine and 325 ml of dichloromethane. The resulting suspension is cooled to

-3o°C, and methylhydrazine (3.52 ml) is added dropwise. The reaction mixture is heated to 0°C and stirred for 1 hour. A further 0.4 ml of methylhydrazine is added and the mixture is stirred for 10 minutes. This sequence is repeated so that a total amount of 2.9 equivalents of methylhydrazine (7.7 ml) has been added. The solvent is removed in vacuo, 2oo ml of new dichloromethane is added and the mixture is concentrated again. This sequence was repeated two more times, the resulting foam was dried under high vacuum for 20 minutes, redissolved in 225

ml dichloromethane and allowed to stand at ambient temperature for approx. 16

hours during which time a significant amount of solids precipitates. The mixture is filtered under nitrogen, the filtrate is cooled to 0°C (nitrogen atmosphere) and treated with diisopropylethylamine (17 ml) followed by benzyl chloroformate (7 ml) dropwise. The reaction mixture is stirred at 0°C for 30 minutes, then at ambient temperature for 1.5 hours. The mixture is washed with two 300 ml portions of monobasic potassium phosphate buffer (pH 4.5), 5% sodium bicarbonate solution (two 300 ml portions), saturated sodium chloride solution (300 ml), and dried (sodium sulfate) and filtered. Concentration in vacuo gives a foam which on trituration with ether gives 9.9 g of the title compound as a solid. D) (cis)-4-(Methoxycarbonyl)-2-oxo-3-[[(phenyl-methoxy)carbonyl]amino]-1-azetidine.

A solution of cerium ammonium nitrate (8.59 g) in 60 ml of 1:1 acetonitrile-water is treated with a slurry of 2 g of (cis)-4-(methoxy-carbonyl)-1-(4-methoxyphenyl)-2-oxo- 3-[[(phenylmethoxy)-carbonyl]amino]-azetidine in 50 ml of acetonitrile for 10 minutes. The reaction mixture is stirred for a further 10 minutes at ambient temperature and diluted with ethyl acetate (10 ml). The separated aqueous layer is washed with ethyl acetate (three 40 ml portions) and the combined organic extracts are washed with 50% sodium bicarbonate solution (three 10 ml portions). The basic washings are washed back with ethyl acetate (50 ml) and the combined organic extracts are washed with aqueous sodium sulphite, 5%, aqueous sodium carbonate (loo ml), 5% sodium chloride solution (two loo ml portions), saturated sodium chloride solution ( two 5o ml portions), and stirred over "Darco G-60" charcoal for 30 minutes. Sodium sulfate is added and the mixture is filtered and concentrated in vacuo to give an oil which on trituration with ether gives 685 mg of the title compound as a solid. E) (cis)-4-(Methoxycarbonyl)-2-oxo-3-[[(phenylmethoxy)-carbonyl] amino]- 1- azetidine sulfonic acid tetrabutylammonium salt♦

A mixture of (cis)-4-(methoxycarbonyl)-2-oxo-3-[[(phenyl-methoxy)carbonyl]amino]-1-azetidine (10 mg) and 172 mg of a pyridine-sulfur trioxide complex in 1 ml pyridine is stirred under argon for 3 hours at 8o°C. The reaction mixture is poured into 7o ml o.5m monobasic calcium phosphate (pH 5.5) and extracted with four 3o ml portions of dichloromethane (discarded). Tetrabutylammonium hydrogen sulfate (122 mg) is added to the aqueous layer which is then extracted with dichloromethane (four 30 mL portions). The organic extracts are washed with 8% sodium chloride solution, dried over sodium sulphate and filtered. Concentration in vacuo gives 186 mg of the title compound as a viscous oil. F) (cis)-3-Amino-4-(methoxycarbonyl)-2-oxo-1- azetidine sulfonic acid.

A solution of 186 mg of (cis)-4-(methoxycarbonyl)-2-oxo-3-[[(phenylmethoxy)carbonyl]amino]-1-azetidinesulfonic acid tetrabutylammonium salt in 2 ml of methanol is hydrogenated over lo% palladium on charcoal (95 mg ) for 1.5 hours at 1 atmosphere. The catalyst is filtered off

and rinsed with dichloromethane and the filtrate treated with 97% formic acid and cooled to -5o°C (the presence of seed crystals at this stage is necessary to induce crystallization). After the start of crystallization, the mixture is allowed to stand for approx. 16 hours at lo°C.

The resulting solid is washed with dichloromethane, hexane, and

dried in vacuo to give 50 mg of the title compound.

Example 20

( S )-( trans )- 3- Amino- 4- ethynyl- 2- oxo- 1- azetidine sulfonic acid.

A) 2-(Trimethylsilyl)ethynylmagnesium bromide.

2o ml of dry tetrahydrofuran, 2.2o ml of trimethylsilylacetylene and 5.o5 ml of a 3.o6m solution of methylmagnesium bromide in ether are added to a flame-dried 5o ml flask which is kept under positive nitrogen pressure. The mixture is stirred for 140 minutes to give the title compound. B) (S)-(trans)-4-[2-(trimethylsilyl)ethynyl]-2- oxo-3-[(triphenylmethyl)amino]azetidine.

To a flame-dried, 250 ml three-necked flask is added 6.00 g of (S)-(trans)-4-(methylsulfonyl)-2-oxo-3-[(triphenylmethyl)amino]-:azetidine. The flask is blown through with nitrogen and then kept under a positive nitrogen pressure. After the reaction mixture has been cooled in a dry ice/isopropanol bath, 4.65 ml of a 3.06m solution of methylmagnesium bromide in ether is added dropwise by means of a syringe with rapid stirring. The solution of 2-(trimethylsilyl)ethynylmagnesium bromide prepared in part A is added by means of a Teflon tube under positive nitrogen pressure (the flask containing the reactant is flushed with 7 ml of tetrahydrofuran). When the addition is finished, remove the cold bath. After 45 minutes, a solution of 3.5 g of potassium bisulphate in 20 ml of water is added. Most of the tetrahydrofuran is removed on a rotary evaporator. The rest is transferred ten. a separatory funnel with ether and water. The aqueous layer is separated and extracted twice with ether. The combined ether layers are washed once with saturated aqueous sodium chloride, dried over sodium sulfate and filtered. Removal of the solvent gives a foam which is chromatographed on a silica column. Elution with 2 liters of dichloromethane, 1 liter of 1% ether/dichloromethane (fraction 1 = looo ml; fractions 2 and 3 = 5oo ml; fraction 4-end = 25o ml) gives 1.3o g of the title compound in fractions 12-19. Fractions 9-11 contain 1.19 g of a mixture of cis- and trans-isomers.

C) (S)-(trans)-4-ethynyl-2-oxo-3-[(triphenylmethyl)amino]azetidine. (S)-(trans)-4-[2- (trimethylsilyl)ethynyl]-2-oxo-3-[ (triphenylmethyl) amino] azetidine (.97 g) is dissolved in 3o ml of dichloromethane and 33o mg of tetrabutylammonium fluoride (containing 2o- 25% water) is added. After 20 minutes, the solvent is removed in vacuo. The residue is taken up in ethyl acetate and water. The organic layer is separated, washed once with water and once with saturated, aqueous sodium chloride, dried over sodium sulfate and filtered. Removal of the solvent gives an oil which is stirred for 15 minutes with 60 ml of pentane to give 2.35 g of the title compound as a powder (after drying in vacuo). D) ( S )-( trans )- 3- Amino- 4- ethynyl- 2- oxo- 1- azetidine sulfonic acid.

(S)-(trans)-4-ethynyl-2-oxo-3-[(triphenylmethyl)amino]-azetidine (404 mg) and 560 mg of a complex of pyridine and sulfur trioxide are added to a 25 ml flask. After the flask has been blown through with nitrogen, 4.0 ml of dry pyridine is added and the mixture is heated to 80-85°C for 3 hours. The mixture is added to a rapidly stirred mixture of 4.0 ml of concentrated hydrochloric acid, 50 ml of water and 50 ml of ethyl acetate. The pH is adjusted to 3.15 with sodium carbonate. The aqueous layer is separated and extracted once with ethyl acetate. The combined organic layer is washed once with saturated aqueous sodium chloride, dried over sodium sulfate and filtered. Solvent removal in vacuo gives a foam which is taken up in 10 ml of dichloromethane. Formic acid (98%, 8 ml) is added and after 15 minutes the mixture is concentrated to 4 ml and Jo ml of dichloromethane is added to give a solid suspended in solution. Filtration gives 100 ml of the title compound as a solid (distinct discoloration with melting>18o°C.

Claims (3)

1. 2-acetidinone, characterized by the general formula I where R 2 is hydrogen or C 1 -C 2 , alkoxy, R 3 and R A are the same or different and are hydrogen or C 1 -C 4 alkyl, as well as salts thereof and stereoisomeric forms thereof. 2. Connection according to claim 1, characterized in that R 3 and R 4 are hydrogen and C 1 -C 4 alkyl, respectively. 3. Connection according to claim 1, characterized in that R2 is hydrogen, and R3 and RA respectively hydrogen and methyl.