in one embodiment , the present invention relates to a compound having the formula ( 1 ) x is a cation selected from the group consisting of an imidazolium cation which can be optionally substituted by one or more c 1 - 6 alkyl groups or a magnesium cation ; it is understood that the charge of the cation and the charge of the phosphate group will be chosen so that the compound having the general formula ( 1 ) will have a neutral net charge . for instance , if the cation is an imidazolium cation , then the phosphate group will typically be whereas if the cation is a magnesium cation , then the phosphate group will typically be in the second formula only one of the possible imidazolium cations which are substituted by one or more c 1 - 6 alkyl groups is shown . it is to be understood that the present invention does not only cover the 1 - methylimidazole cation which is shown but also the 2 - methylimidazole cation , 3 - methylimidazole cation , 4 - methylimidazole cation and 5 - methylimidazole cation as well as respective imidazole cations having more than one methyl group . furthermore , the present invention is not restricted to methyl as a c 1 - 6 alkyl group but also covers corresponding cations in which the imidazolium cation is substituted by other straight or branched c 1 - 6 alkyl groups including ethyl , propyl , butyl , pentyl and hexyl . ethyl and methyl are preferred and methyl is more preferred . the number of substituents is not particularly limited and can be , e . g ., 1 to 5 , preferably 1 or 2 , more preferably 1 c 1 - 6 alkyl group . the compounds of the present invention can be provided in the form of a pharmaceutically acceptable solvate . the scope of the present invention embraces the compounds in any solvated form , including , e . g ., solvates with water , for example hydrates , or with organic solvents such as methanol , ethanol , isopropanol or acetonitrile or with c 1 - 4 alkanoic acids such as acetic acid and propionic acid . the present invention refers to a process comprising the steps of : ( i ) reacting a compound having the formula ( 2 ) or a salt thereof ( ii ) adding a reagent selected from the group consisting of a magnesium salt , and an imidazole which can be optionally substituted by one or more c 1 - 6 alkyl groups ; the compound having the formula ( 2 ) and the compound having the formula ( 3 ) are known in the art and can be prepared , e . g ., as described in ep - a - 1 310 502 or pct / ep2012 / 067550 . the conditions for reacting the compound having the formula ( 2 ) and the compound having the formula ( 3 ) are not particularly restricted and any known reaction conditions can be chosen . in one possible embodiment , the compound having the formula ( 2 ) is first silylated and subsequently acylated . in an alternative embodiment , the compound having the formula ( 2 ) and the compound having the formula ( 3 ) are directly acylated . in a preferred embodiment the ratio of the compound having the formula ( 2 ) to the compound having the formula ( 3 ) is in the range of about ( 1 to 3 mol ): about ( 1 mol ), preferably about ( 1 to 1 . 2 mol ): about ( 1 mol ). the reaction will be typically conducted at about − 40 ° c . to about 40 ° c ., preferably about − 10 ° c . to about 10 ° c . the reaction duration is not particularly limited and can be , for instance , about 5 min to about 24 h , more preferably about 20 min to about 2 h . if the direct acylation is chosen , the reaction preferably takes place in the presence of an acid scavenger which captures the acid that is generated during the reaction . examples of suitable acid scavengers include salts ( e . g ., sodium hydrogen carbonate , sodium carbonate , potassium carbonate , sodium acetate , potassium acetate , and sodium phosphate ), tertiary amines ( e . g ., triethylamine , tripropylamine , tributylamine , ethyldiisopropylamine , pyridine , lutidine , n , n - dimethylaniline , n - methylpiperidine , n - methylpyrrolidine , and n - methylmorpholine ), alkylene oxides ( e . g ., propyleneoxide , and epichlorohydrin ) and mixtures thereof . of these , a combination of sodium hydrogen carbonate , sodium carbonate , sodium acetate , triethylamine or sodium acetate with triethylamine is preferable , and particularly a combination of sodium hydrogen carbonate , sodium acetate , triethylamine or sodium acetate with triethylamine is more preferable . in this embodiment the solvent is usually any suitable solvent that does not detrimentally effect the reaction . examples of possible solvents include solvents such as water , dimethylformamide , sulfolane , tetrahydrofran and mixtures thereof can be used . in the alternative embodiment in which a silylation is conducted a silane is used . the silane is not particularly restricted and can , for example , be a silane having the formula halsir 3 ( wherein hal is a halogen ; preferably cl , br , or i ; more preferably i ; and r is independently selected from a c 1 - 6 alkyl group ; preferably ch 3 ); a silazane having the formula r 3 si — nh — sir 3 ( wherein r is independently selected from a c 1 - 6 alkyl group ; preferably ch 3 ), a silylurea compound having the formula r 3 si — nh — c ( o )— nh — sir 3 ( wherein r is independently selected from a alkyl group ; preferably ch 3 ), a silylformamide having the formula h — c ( o )— n ( sir 3 ) 2 ( wherein r is independently selected from a c 1 - 6 alkyl group ; preferably ch 3 ), or a silylacetamide having the formula r 3 si — n ═ c ( ch 3 )— o — sir 3 or r 3 si — n ═ c ( cf 3 )— o — sir 3 ( wherein r is independently selected from a c 1 - 6 alkyl group ; preferably ch 3 ). the silane silylates the carboxylic acid group of the compound having the formula ( 2 ). examples of possible silanes include n , o - bistrimethylsilylacetamide , trimethylsilylacetamide , bistrimethylsilylformamide , bistrimethylsilyltrifluoroacetamide , n , n ′- bistrimethylsilylurea , trimethylsilyliodide , hexamethyldisilazane and mixtures thereof . the silylation reaction is typically conducted in a polar solvent such as a nitrile solvent ( including acetonitrile ) or an amide solvent ( including dimethylacetamide ). the reaction temperature is not particularly limited and can be , for instance , in the range of about − 40 ° c . to about 40 ° c ., preferably about − 10 ° c . to about 30 ° c . the silylated intermediate having the formula ( 5 ) can then be reacted with the compound having the formula ( 3 ). the reaction is usually carried out in the same solvent which was employed in the silylation reaction . the reaction temperature is not particularly limited and can be chosen , e . g ., in the range of about − 10 ° c . to about 10 ° c . an acid scavenger is typically not required if a silylated intermediate is reacted with the compound having the formula ( 3 ). after this reaction the silyl group — sir 3 is usually removed by hydrolysis . the hydrolysis reaction can be conducted with or without the presence of an acid scavenger . examples of suitable acid scavengers include salts ( e . g ., sodium hydrogen carbonate , sodium acetate , magnesium acetate ), tertiary amines ( e . g ., triethylamine , tripropylamine , tributylamine , ethyldiisopropylamine , pyridine , lutidine , n , n - dimethylaniline . n - methylpiperidine , n - methylpyrrolidine , and n - methylmorpholine ), amberlite la 2 ( n - dodecyl - n - isododecylamine ), alkylene oxides ( e . g ., propylene oxide , and epichlorohydrin ) and mixtures thereof . after the acylation , a reagent selected from the group consisting of a magnesium salt and an imidazole which can be optionally substituted by one or more c 1 - 6 alkyl groups is added to provide a compound having the formula ( 1 ) in the embodiment in which a magnesium salt of the compounds of the present invention is to be prepared , it is also possible to use a magnesium salt as an acid scavenger and to thus prepare the compounds of the present invention in situ . the magnesium salt is not particularly restricted and can , for example , be selected from the group consisting of magnesium salts of carboxylic acids such as magnesium acetate , magnesium formiate , magnesium lactate , magnesium aspartate and magnesium citrate ; magnesium salts of sulfonic acids such as magnesium methanesulfonate which can , for example , be used in combination with a tertiary amine ( e . g ., a c 1 - 4 alkyl amine like tributylamine ); as well as inorganic magnesium salts such as magnesium chloride which can , for example , be used in combination with a tertiary amine ( e . g ., a c 1 - 4 alkyl amine like tributylamine ). hydrates of these magnesium salts are also possible . the ratio of the magnesium salt to the compound having the formula ( 3 ) is preferably about ( 1 to 6 mol ):( 1 mol ), more preferably about ( 1 . 1 to 3 mol ):( 1 mol ). the reaction can be conducted in any suitable solvent that does not detrimentally effect the reaction . examples of possible solvents include polar solvents such as alcohols ( such as c 1 - 4 alcohols ), nitriles ( such as acetonitrile ), alcohols ( such as ethanol , isopropanol ), ethers ( such as tetrahydrofuran ), amides ( such as dimethylformamide , dimethylacetamide ), ketones ( such as acetone ) and esters ( such as ethyl acetate ). mixtures of these solvents can also be used . the reaction will be typically conducted at about − 40 ° c . to about 40 ° c ., preferably about − 30 ° c . to about − 10 ° c . the reaction duration is not particularly limited and can be , for instance , about 30 min to about 24 h , more preferably about 30 min to about 4 h . in an alternative embodiment , the reagent is an imidazole which can be optionally substituted by one or more c 1 - 6 alkyl groups . examples thereof include imidazole and methyl - imidazole . the ratio of the imidazole which can be optionally substituted by one or more c 1 - 6 alkyl groups to the compound having the formula ( 3 ) is preferably about ( 1 to 10 mol ):( 1 mol ), more preferably about ( 1 . 5 to 8 mol ):( 1 mol ). the reaction can be conducted in any suitable solvent that does not detrimentally effect the reaction . examples of possible solvents include polar solvents such as alcohols ( such as c 1 - 4 alcohols ), nitriles ( such as acetonitrile ), ethers ( such as tetrahydrofuran ), amides ( such as dimethylformamide , dimethylacetamide ), ketones ( such as acetone ) and esters ( such as ethyl acetate ). mixtures of these solvents can also be used . the reaction will be typically conducted at about − 40 ° c . to about 40 ° c ., preferably about − 10 ° c . to about 10 ° c . the reaction duration is not particularly limited and can be , for instance , about 10 min to about 24 h , more preferably about 30 min to about 4 h . the compound having the formula ( 1 ) can be crystallized and isolated from the reaction mixture . if desired , it can be isolated and , for example , washed and dried before it is subjected to further processing . if desired , the compound having the formula ( 1 ) can be transformed into a compound having the formula ( 4 ) y is preferably ch 3 cooh , ch 3 ch 2 cooh or ch 3 cn , more preferably ch 3 cooh . this transformation reaction is not particularly limited and any reaction previously employed with respect to the corresponding compounds in which x is a sodium cation can be employed . in one embodiment , the transformation reaction can be conducted by adding an acid . examples of acids include inorganic acids ( such as sulfuric acid , phosphoric acid , and hydrochloric acid ) as well as organic acids ( such as 4 - toluenesulfonic acid , methanesulfonic acid and oxalic acid ). the ph of the reaction mixture is , for example , in the range of about 2 to about 0 . 5 , preferably about 0 . 8 to about 0 . 6 . the transformation can be conducted , e . g ., at a temperature in the range of about 0 ° c . to about 40 ° c ., preferably about 0 ° c . to about 30 ° c . the solvent is not particularly limited and can be a polar solvent such as water , carboxylic acids ( such as acetic acid ) and nitrile solvents ( such as acetonitrile ). as well as mixtures thereof . the desired product can be obtained by removing the solvent . the procedures for solvent removal are well known in the art and include evaporation as well as crystallization from the solution . in a preferred embodiment the solvent is removed by crystallizing in a mixture of water and acetic acid . the acid which is formed in the reaction between the compound having the formula ( 1 ) and the compound having the formula ( 2 ) can be neutralized , for example , by a base such as a tri ( c 1 - 4 alkyl ) amine like triethylamine or ethyldiisopropylamine . if an imidazolium salt is to be prepared , it is possible to use the imidazole itself as a base for neutralizing the acid . if the magnesium salt is to be prepared , it is possible to use a magnesium acetate as a base for neutralizing the acid . the compounds having the formula ( 1 ) are soluble in water . if water is used as a solvent or for the hydrolysis , an anti - solvent , e . g . acetonitrile , isopropanol or tetrahydrofuran , can be used to improve the crystallization and isolation of the compound having the formula ( 1 ). previously , for example in ep - a - 1 310 502 and ep - a - 1 043 327 , a compound having the formula ( 1 ) in which x was sodium was used as an intermediate . this sodium compound was instable and degraded during processing , so that by - products were formed which had to be removed , e . g ., by column chromatography . the present inventors have surprisingly found that the compound having the formula ( 4 ) can be provided in the same purity level without having to conduct column chromatography if x is a cation selected from the group consisting of imidazolium cation which can be optionally substituted by one or more c 1 - 6 alkyl groups and a magnesium cation . without wishing to be bound by theory , it is assumed that the compounds of the present invention , particularly the imidazolium compounds , are more stable than the known ceftaroline disodium salt . therefore , the present process can be conducted without having to use column chromatography , or preferably other purification steps such as any type of chromatography . typically , the hplc - purity of the ceftaroline fosamil via imidazolium salt is up to 97 . 6 area %. to a mixture of 300 ml acetonitrile and 30 ml dimethylacetamide was added 15 . 0 g of 4 -[ 2 -[[( 6r , 7r )- 7 - amino - 2 - carboxy - 8 - oxo - 5 - thia - 1 - azabicyclo [ 4 . 2 . 0 ] oct - 2 - en - 3 - yl ] thio ]- 4 - thiazolyl ]- 1 - methyl - pyridinium , chloride , hydrochloride ( 31 . 3 mmol ) and 22 . 8 g of n , o - bistrimethylsilylacetamide ( 3 . 6 equi , 112 mmol ). after stirring for 45 minutes the resulting solution was cooled to 0 ° c . at this temperature 11 . 25 g of 2 -( 5 -( dichlorophosphinyl ) amino ]- 1 , 2 , 4 - thiadiazole - 3 - yl ]- 2 ( z )- ethoxyiminoacetyl chloride ( 1 . 02 equi , 32 . 0 mmol ) was added and stirring was continued for 30 minutes . then the reaction mixture was poured into 300 ml of ice water and stirred for 1 hour at 0 ° c . to the mixture was added 300 ml of tetrahydrofuran ( thf ). after stirring for 16 hours at 0 ° c ., 3 . 0 g of charcoal was added and after 5 minutes stirring charcoal was removed by filtration . the ph of the filtrate was adjusted to 3 . 0 by adding approx . 62 g of amberlite la 2 ( n - dodecyl - n - isododecylamine ). to the mixture was added 300 ml of heptane . after 5 minutes stirring the layers were separated and the organic layer was discarded . the aqueous layer was extracted once more with 150 ml of heptane . to the extracted aqueous layer were added 8 . 25 g of magnesium acetate tetrahydrate ( 1 . 2 equi , 38 . 5 mmol ) and 300 ml acetonitrile . after stirring for 30 minutes at ambient temperature the suspension was cooled to 0 ° c . and stirred at this temperature for 1 hour . the crystals were isolated by filtration , washed with 90 ml aqueous acetonitrile ( 1 / 1 ) and 270 ml of acetonitrile . after drying in vacuo at room temperature 21 . 3 g of ceftaroline fosamil magnesium salt were obtained in the form of a crystalline powder . to a mixture of 300 ml acetonitrile and 30 ml dimethylacetamide were added 15 . 0 g of 4 -[ 2 -[[( 6r , 7r )- 7 - amino - 2 - carboxy - 8 - oxo - 5 - thia - 1 - azabicyclo [ 4 . 2 . 0 ] oct - 2 - en - 3 - yl ] thio ]- 4 - thiazolyl ]- 1 - methyl - pyridinium , chloride , hydrochloride ( 31 . 3 mmol ) and 22 . 8 g of n , o - bistrimethylsilylacetamide ( 3 . 6 equi , 112 mmol ). after stirring for 45 minutes the resulting solution was cooled to 0 ° c . at this temperature 11 . 25 g of 2 -( 5 -( dichlorophosphinyl ) amino ]- 1 , 2 , 4 - thiadiazole - 3 - yl ]- 2 ( z )- ethoxyiminoacetyl chloride ( 1 . 02 equi , 32 . 0 mmol ) was added and stirring was continued for 30 minutes . then the reaction mixture was poured into 300 ml of ice water . to the solution were added 150 ml of tetrahydrofuran . after stirring for 16 hours at 0 ° c . to the mixture were added 3 . 0 g of charcoal and after 5 minutes stirring the charcoal was removed by filtration . to the filtrate were added 15 . 0 g of imidazole ( 7 . 0 equi , 220 mmol ) and then 450 ml of ethanol were added dropwise over 30 minutes . the resulting slurry was stirred for 2 hours at 0 ° c . the crystals were isolated by filtration and washed with 200 ml of ethanol . after drying in vacuo at room temperature 17 . 6 g ( 74 . 8 %) of the imidazolium salt were obtained in the form of a crystalline powder . to a mixture of 300 ml acetonitrile and 30 ml dimethylacetamide were added 15 . 0 g of 4 -[ 2 -[[( 6r , 7r )- 7 - amino - 2 - carboxy - 8 - oxo - 5 - thia - 1 - azabicyclo [ 4 . 2 . 0 ] oct - 2 - en - 3 - yl ] thio ]- 4 - thiazolyl ]- 1 - methyl - pyridinium , chloride , hydrochloride ( 31 . 3 mmol ) and 22 . 8 g of n , o - bistrimethylsilylacetamide ( 3 . 6 equi , 112 mmol ). after stirring for 45 minutes the resulting solution was cooled to 0 ° c . at this temperature 11 . 25 g of 2 -( 5 -( dichlorophosphinyl ) amino ]- 1 , 2 , 4 - thiadiazole - 3 - yl ]- 2 ( z )- ethoxyiminoacetyl chloride ( 1 . 02 equi , 32 . 0 mmol ) was added and stirring was continued for 30 minutes . then the reaction mixture was poured into 300 ml of ice water and stirred for 16 hours at 0 ° c . to the mixture were added 3 . 0 g of charcoal and after 5 minutes stirring charcoal was removed by filtration . to the filtrate were added 18 . 0 g of 1 - methyl - imidazole ( 7 . 0 equi , 219 mmol ) and then 900 ml of isopropanol were added dropwise over 30 minutes . the resulting slurry was stirred for 2 hours at 0 ° c . the crystals were isolated by filtration and washed with 300 ml of isopropanol . after drying in vacuo at room temperature 16 . 8 g ( 70 . 1 %) of the 1 - methylimidazolium salt were obtained in the form of a crystalline powder . to 24 ml deionized water was added 4 . 0 g of 4 -[ 2 -[[( 6r , 7r )- 7 - amino - 2 - carboxy - 8 - oxo - 5 - thia - 1 - azabicyclo [ 4 . 2 . 0 ] oct - 2 - en - 3 - yl ] thio ]- 4 - thiazolyl ]- 1 - methyl - pyridinium , chloride , hydrochloride ( 8 . 3 mmol ). the suspension was cooled to 10 ° c . at this temperature 5 . 5 ml of 3m sodium acetate were added and the ph of the mixture is adjusted to 8 . 5 by addition of approx . 2 . 3 ml of triethylamine . the resulting solution was cooled to 0 ° c . at this temperature 5 ml of triethylamine and a cold (− 40 ° c .) solution of 3 . 5 g of 2 -( 5 -( dichlorophosphinyl ) amino ]- 1 , 2 , 4 - thiadiazole - 3 - yl ]- 2 ( z )- ethoxyiminoacetyl chloride ( 1 . 02 equi , 32 . 0 mmol ) in 9 . 5 ml of tetrahydrofuran were added thereto immediately . then the reaction mixture was warmed to 22 ° c . and stirred at this temperature for 1 hour while keeping the ph to 5 . 0 by adding approx . 1 . 1 ml of triethylamine . after stirring for 1 hour 1 . 78 g of magnesium acetate tetrahydrate ( 1 . 0 equi , 8 . 3 mmol ) were added . to the mixture were added 92 ml of ethanol . the resulting suspension was cooled to 0 ° c . and stirred at this temperature for 1 hour . the crystals were isolated by filtration . the cake was washed with 20 ml of cooled ethanol / water ( 2 / 1 ), 40 ml of cooled ethanol and 40 ml of methyl t - butyl ether . the wet product was dried at ≦ 20 ° c . in vacuo yielding 5 . 98 g of a crystalline powder . to a solution of 2 . 6 g of d - mannitol in 36 . 7 g of water and 47 . 8 g of acetic acid were added 16 . 0 g of 4 -[ 2 -[[( 6r , 7r )- 2 - carboxy - 7 -[[( 2z )- 2 -( ethoxyimino )- 2 -[ 5 -( phosphonoamino )- 1 , 2 , 4 - thiadiazol - 3 - yl ] acetyl ] amino ]- 8 - oxo - 5 - thia - 1 - azabicyclo [ 4 . 2 . 0 ] oct - 2 - en - 3 - yl ] thio ]- 4 - thiazolyl ]- 1 - methyl - pyridinium , inner salt , magnesium salt ( 22 . 6 mmol ). to the slurry were added 7 . 6 ml of 2 . 5m sulfuric acid and 0 . 8 g of charcoal . after 5 minutes stirring charcoal was removed by filtration . the charcoal was washed with 5 ml of acetic acid / water ( 1 / 1 ). filtrate and wash liquid were combined , seeds were added and the mixture was stirred at room temperature for 2 hours . the suspension was cooled to 0 ° c . and stirred for 2 hours at this temperature . then the crystals were isolated by filtration , washed with 25 ml of acetic acid / water / 1 / 1 ), 25 ml acetic acid / water ( 1 / 4 ) and 25 ml of ethanol / acetic acid ( 1 / 1 ), and dried in vacuo give 7 . 5 g of the title compound . 1h nmr ( dmso - d6 ): d 1 . 24 ( 3h , t , j = 7 hz ), 1 . 91 ( 3h , s ), 3 . 58 , 3 . 95 ( 2h , abq , j = 17 hz ), 4 . 17 ( 2h , q , j = 7 hz ), 4 . 34 ( 3h , s ), 5 . 32 ( 1h , d , j = 5 hz ), 5 . 92 ( 1h , dd , j = 5 hz , 8 hz ), 8 . 51 ( 2h , d , j = 6 hz ), 8 . 99 ( 3h , m ), 9 . 30 ( 1h , m ), 9 . 70 ( 1h , d , j = 8 hz ) to 249 ml of water and 270 ml of acetonitrile were added 36 . 5 g of 4 -[ 2 -[[( 6r , 7r )- 2 - carboxy - 7 -[[( 2z )- 2 -( ethoxyimino )- 2 -[ 5 -( phosphonoamino )- 1 , 2 , 4 - thiadiazol - 3 - yl ] acetyl ] amino ]- 8 - oxo - 5 - thia - 1 - azabicyclo [ 4 . 2 . 0 ] oct - 2 - en - 3 - yl ] thio ]- 4 - thiazolyl ]- 1 - methyl - pyridinium , inner salt , magnesium salt ( 51 . 6 mmol ). to the solution were added at room temperature 7 . 1 ml acetic acid , 21 . 6 ml of conc . hydrochloric acid and 2 . 2 g of charcoal . after 5 minutes stirring the charcoal was removed by filtration . the charcoal was washed with 40 ml of acetonitrile / water ( 5 / 2 ). filtrate and wash liquid were combined and 274 ml of acetonitrile were added dropwise over 30 minutes at room temperature . the suspension was cooled to 0 ° c . and stirred for 1 hour at this temperature . then the crystals were isolated by filtration , washed with 25 ml of acetonitrile / water ( 2 / 1 ) and 50 ml of acetonitrile , and dried in vacuo to give 14 . 5 g of the title compound . 1h nmr ( dmso - d6 ): d 1 . 23 ( 3h , t , j = 7 hz ), 2 . 07 ( 3h , s ), 3 . 58 , 3 . 95 ( 2h , abq , j = 17 hz ), 4 . 17 ( 2h , q , j = 7 hz ), 4 . 33 ( 3h , s ), 5 . 32 ( 1h , d , j = 5 hz ), 5 . 91 ( 1h , dd , j = 5 hz , 8 hz ), 8 . 51 ( 2h , d , j = 6 hz ), 8 . 99 ( 3h , m ), 9 . 34 ( 1h , m ), 9 . 71 ( 1h , d , j = 8 hz ) to 88 ml of water and 154 ml of acetic acid were added 38 . 0 g of 4 -[ 2 -[[( 6r , 7r )- 2 - carboxy - 7 -[[( 2z )- 2 -( ethoxyimino )- 2 -[ 5 -( phosphonoamino )- 1 , 2 , 4 - thiadiazol - 3 - yl ] acetyl ] amino ]- 8 - oxo - 5 - thia - 1 - azabicyclo [ 4 . 2 . 0 ] oct - 2 - en - 3 - yl ] thio ]- 4 - thiazolyl ]- 1 - methyl - pyridinium , inner salt , imidazolium salt . to the resulting solution were added 3 g of charcoal . after 5 minutes stirring charcoal was removed by filtration . the charcoal was washed with 20 ml of water . filtrate and wash liquid were combined and after addition of 15 . 7 ml of 2 . 5m sulfuric acid and seeds the mixture was stirred at room temperature for 2 hours . the suspension was cooled to 0 ° c . and stirred for 2 hours at this temperature . then the crystals were isolated by filtration , washed with 290 ml of acetic acid / water ( 1 / 1 ), 150 ml acetic acid / water ( 1 / 4 ) and 150 ml of ethanol / acetic acid ( 1 / 1 ), and dried in vacuo to give 24 . 3 g of the title compound . 1h nmr ( dmso - d6 ): d 1 . 24 ( 3h , t , j = 7 hz ), 1 . 91 ( 3h , s ), 3 . 58 , 3 . 95 ( 2h , abq , j = 17 hz ), 4 . 17 ( 2h , q , j = 7 hz ), 4 . 34 ( 3h , s ), 5 . 32 ( 1h , d , j = 5 hz ), 5 . 92 ( 1h , dd , j = 5 hz , 8 hz ), 8 . 51 ( 2h , d , j = 6 hz ), 8 . 99 ( 3h , m ), 9 . 30 ( 1h , m ), 9 . 70 ( 1h , d , j = 8 hz ) 4 -[ 2 -[[( 6r , 7r )- 2 - carboxy - 7 -[[( 2z )- 2 -( ethoxyimino )- 2 -[ 5 -( phosphonoamino )- 1 , 2 , 4 - thiadiazol - 3 - yl ] acetyl ] amino ]- 8 - oxo - 5 - thia - 1 - azabicyclo [ 4 . 2 . 0 ] oct - 2 - en - 3 - yl ] thio ]- 4 - thiazolyl ]- 1 - methyl - pyridinium , inner salt , disodium salt was prepared according to the method described in working example 1 of ep 1 043 327 b1 . hplc - analysis of the isolated disodium salt showed formation of by - products during the drying process and storage at 20 ° c . this indicates that the isolated disodium salt was very unstable . the starting materials 2 -( 5 -( dichlorophosphinyl ) amino ]- 1 , 2 , 4 - thiadiazole - 3 - yl ]- 2 ( z )- ethoxyiminoacetyl chloride and 4 -[ 2 -[[( 6r , 7r )- 7 - amino - 2 - carboxy - 8 - oxo - 5 - thia - 1 - azabicyclo [ 4 . 2 . 0 ] oct - 2 - en - 3 - yl ] thio ]- 4 - thiazolyl ]- 1 - methyl - pyridinium , chloride , hydrochloride monohydrate were prepared according to the procedures described in ep - a - 1 310 502 .