Abstract:
A compound represented by Formula I, wherein M represents Na + , K + , NH4 + , or Cs + ; and 1) when Y represents SO 4   2− : when m=1, then n=1; and when m=0.5, then n=1.5; and 2) when Y represents PO 4   2− , when m=1, then n=2. The compound has good solubility and high bioavailability and can be formulated into oral pharmaceutical preparations and pharmaceutical preparations for injections.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of International Patent Application No. PCT/CN2009/076164 with an international filing date of Dec. 29, 2009, designating the United States, now pending, and further claims priority benefits to Chinese Patent Application No. 200810164211.3 filed Dec. 31, 2008. The contents of all of the aforementioned applications, including any intervening amendments thereto, are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a compound and method for producing the same, and more particularly to a cefdinir acid double salt, a preparation method, and use thereof. 
         [0004]    2. Description of the Related Art 
         [0005]    Cefdinir was first synthesized by Fujisawa Company, Japan, in 1988 by modifying the structure of cefixime. It is the third generation of oral cephalosporin. The vinyl group linked to a mother ring carbon of cephalosporin improves the oral absorption rate thereof. The hydroxyl amino group and ammonia thiophene group at the side chain not only enhance the antibacterial activity against gram-negative bacteria and the stability of β-lactamase, but also improve the antibacterial activity against gram-positive bacteria, particularly against  Staphylococcus aureus.  The cefdinir preparations were first approved for sale in Japan in December, 1991, with a brand name of Cefzon, and then were sold in USA in December, 1997, with a brand name of Omnicef, and in Korea in 1999. Tianjin Centralpharm Co., Ltd. and Tianjin Institute of Pharmaceutical Research have cooperatively developed the production and synthesis of cefdinir and the dosage form of capsules and granules are obtained. The capsules have a brand name of Cefdinir Capsules, approved for sale in 2001 in China. 
         [0006]    With a broad antimicrobial spectrum, high activity, good drug resistance, cefdinir is very excellent in the third generation of cephalosporin. However, it has obvious disadvantages such as low solubility and low bioavailability. Study shows that capsule cefdinir has a bioavailability of 16-20%, and for a liquid suspension, the bioavailability is merely 25%. Low bioavailability wastes drug resources, and the antibiotic residues easily cause side effect, e.g., intestinal flora disturbance and diarrhea. Furthermore, cefdinir is insoluble in water, and thus it cannot be prepared into an injection directly. 
         [0007]    To solve the above disadvantages, a large number of researches have been conducted. Since the chemical structure of cefdinir includes carboxylic acids and amino group, a basic salt or acid salt thereof has been disclosed. 
         [0008]    Chinese Pat. CN 1,415,615 discloses sodium cefdinir and a preparation method thereof. Chinese Pat. CN 1,251,590 discloses a salt synthesized by cefdinir and dicyclohexylamine. Chinese Pat. CN 1,512,996 discloses sulfate or mesylate cefdinir. U.S. Pat. No. 4,559,334 discloses the following cefdinir salt: sodium, potassium, calcium, magnesium, ammonium, organic ammonium, hydrochloric acid, sulfuric acid, bromated, phosphoric acid, formic acid, acetic acid, trifluoroacetic acid, maleic acid, tartaric acid, methanesulfonic acid, benzoic acid, arginine, aspartic acid, glutamic acid. KR20070088757 discloses a method for producing cesium cefdinir to purify cefdinir. DE60311869 discloses a method for producing phosphate cefdinir to purify cefdinir. 
         [0009]    Cefdinir basic salts have poor stability. 
         [0010]    The cefdinir salts recited in the above patents mainly target the purification of cefdinir. Prior to this disclosure, no cefidinir acid double salts or the benefits thereof have been reported. 
       SUMMARY OF THE INVENTION 
       [0011]    In view of the above-described problems, it is one objective of the invention to provide a cefdinir acid double salt. 
         [0012]    It is another objective of the invention to provide a method for producing a cefdinir acid double salt. 
         [0013]    To achieve the above objectives, in accordance with one embodiment of the invention, there is provided a cefdinir acid double salt represented by Formula I: 
         [0000]    
       
                 
         
             
             
         
       
     
         [0014]    wherein M represents Na + , K + , NH4 + , or Cs + ; and 1) when Y represents SO 4   2−  and m=1, n=1; when m=0.5, n=1.5; 2) when Y represents PO 4   2− , m=1, n=2. 
         [0015]    In accordance with another embodiment of the invention, there is provided a method for producing the cefdinir acid double salt. The method comprises contacting cefdinir with an acid and an alkali or ammonium compound, or contacting cefdinir with an acid salt. When the acid or acid salt comprises a sulfate group, the product is a cefdinir sulfate double salt. When the acid or acid salt comprises a phosphate group, the product is a cefdinir phosphate double salt. 
         [0016]    In a class of this embodiment, the cefdinir sulfate double salt is prepared as follows. 1) Cefdinir and equimolar sulfuric acid is mixed, and then an alkali compound with a molar ratio to cefdinir of 0.5:1 or 1:1 is added. The resultant product is concentrated, crystallized with ether, filtered, and dried to yield cefdinir sodium hydrogen (1 or 0.5) sulfate (1 or 1.5), cefdinir potassium hydrogen (1 or 0.5) sulfate (1 or 1.5), or cefdinir cesium hydrogen (1 or 0.5) sulfate (1 or 1.5). 2) Cefdinir and equimolar sulfuric acid is mixed, and then ammonium acetate, ammonia gas, or ammonia water with a molar ratio to cefdinir of 0.5:1 or 1:1 is added. The resultant product is concentrated, crystallized with ether, filtered, and dried to yield cefdinir ammonium hydrogen (1 or 0.5) sulfate (1 or 1.5). 3) Cefdinir and equimolar sodium hydrogen sulfate, potassium hydrogen sulfate, or ammonium hydrogen sulfate is mixed. The resultant product is concentrated, crystallized with ether, filtered, and dried to yield a cefdinir sulfate double salt. 
         [0017]    In a class of this embodiment, the cefdinir sulfate double salt is represented by the following formulas: 
         [0000]    
       
                 
         
             
             
         
       
       
                 
         
             
             
         
       
     
         [0018]    In a class of this embodiment, the cefdinir phosphate double salt is prepared as follows. 1) Cefdinir and equimolar phosphoric acid is mixed, and then an alkali compound with a molar ratio to cefdinir of 1:1 is added. The resultant product is concentrated, crystallized with ether, filtered, and dried to yield cefdinir sodium dihydrogen phosphate, cefdinir potassium dihydrogen phosphate, or cefdinir cesium dihydrogen phosphate. 2) Cefdinir and equimolar phosphoric acid is mixed, and then ammonium acetate, ammonia gas, or ammonia water with a molar ratio to cefdinir of 1:1 is added. The resultant product is concentrated, crystallized with ether, filtered, and dried to yield cefdinir ammonium dihydrogen phosphate. 3) Cefdinir and equimolar sodium dihydrogen phosphate, potassium dihydrogen phosphate, or ammonium dihydrogen phosphate is mixed. The resultant product is concentrated, crystallized with ether, filtered, and dried to yield cefdinir sodium dihydrogen phosphate, cefdinir potassium dihydrogen phosphate, or cefdinir ammonium dihydrogen phosphate. 
         [0019]    In a class of this embodiment, the cefdinir phosphate double salt is represented by the following formulas: 
         [0000]    
       
                 
         
             
             
         
       
     
         [0020]    In a class of this embodiment, the alkali compound is selected from the group consisting of sodium methoxide, potassium methoxide, cesium methoxide, sodium ethoxide, potassium ethoxide, cesium ethoxide, sodium propoxide, potassium propoxide, cesium propoxide, sodium butoxide, potassium butoxide, cesium butoxide, sodium isopropoxide, potassium isopropoxide, cesium isopropoxide, sodium tert-butoxide, potassium tert-butoxide, cesium tert-butoxide, sodium acetate, potassium acetate, cesium acetate, sodium propionate, potassium propionate, cesium propionate, sodium butyrate, potassium butyrate, cesium butyrate, sodium hydroxide, potassium hydroxide, and cesium hydroxide. 
         [0021]    In a class of this embodiment, the ammonium compound is selected from the group consisting of ammonia, ammonia water, ammonium acetate, ammonium propionate, and ammonium butyrate. 
         [0022]    In a class of this embodiment, the cefdinir sulfate double salt comprises (−)-(6R,7R)-7-((Z)-2-(2-aminothiazole-4-yl)-2-hydroxyimino-acetylamino)-8-oxo-3-vinyl-5-thia-1-azabicyclo(4.2.0)oct-2-ene-2-carboxylic acid sodium hydrogen sulfate, (−)-(6R,7R)-7-((Z)-2-(2-aminothiazole-4-yl)-2-hydroxyimino-acetylamino)-8-oxo-3-vinyl-5-thia-1-azabicyclo(4.2.0)oct-2-ene-2-carboxylic acid potassium hydrogen sulfate, (−)-(6R,7R)-7-((Z)-2-(2-aminothiazole-4-yl)-2-hydroxyimino-acetylamino)-8-oxo-3-vinyl-5-thia-1-azabicyclo(4.2.0)oct-2-ene-2-carboxylic acid ammonium hydrogen sulfate, and (−)-(6R,7R)-7-((Z)-2-(2-aminothiazole-4-yl)-2-hydroxyimino-acetylamino)-8-oxo-3-vinyl-5-thia-1-azabicyclo(4.2.0)oct-2-ene-2-carboxylic acid cesium hydrogen sulfate. The cefdinir sulfate double salt further comprises(−)-(6R, 7R)-7-((Z)-2-(2-aminothiazole-4-yl)-2-hydroxyimino-acetylamino)-8-oxo-3-vinyl-5-thia-1-azabicyclo(4.2.0)oct-2-ene-2-carboxylic acid sodium hydrogen (0.5) sulfate (1.5), (−)-(6R, 7R)-7-((Z)-2-(2-aminothiazole-4-yl)-2-hydroxyimino-acetylamino)-8-oxo-3-vinyl-5-thia-1-azabicyclo(4.2.0)oct-2-ene-2-carboxylic acid potassium hydrogen (0.5) sulfate (1.5), (−)-(6R,7R)-7-((Z)-2-(2-aminothiazole-4-yl) -2-hydroxyimino-acetylamio)-8-oxo-3-vinyl-5-thia-1-azabicyclo(4.2.0)oct-2-ene-2-carboxylic acid ammonium hydrogen (0.5) sulfate (1.5), and (−)-(6R,7R)-7-((Z)-2-(2-aminothiazole-4-yl)-2-hydroxyimino-acetylamino)-8-oxo-3-vinyl-5-thia-1-azabicyclo(4.2.0)oct-2-ene-2-carboxylic acid cesium hydrogen (0.5) sulfate (1.5). 
         [0023]    In a class of this embodiment, the cefdinir phosphate double salt comprises (−)-(6R, 7R)-7-((Z)-2-(2-aminothiazole-4-yl)-2-hydroxyimino-acetylamino)-8-oxo-3-vinyl-5-thia-1-azabicyclo(4.2.0)oct-2-ene-2-carboxylic acid sodium dihydrogen phosphate, (−)-(6R, 7R)-7-((Z)-2-(2-aminothiazole-4-yl)-2-hydroxyimino-acetylamino) 8-oxo-3-vinyl-5-thia-1-azabicyclo(4.2.0)oct-2-ene-2-carboxylic acid potassium dihydrogen phosphate, and (−)-(6R,7R)-7-((Z)-2-(2-aminothiazole-4-yl)-2-hydroxyimino-acetylamino)-8-oxo-3-vinyl-5-thia-1-azabicyclo(4.2.0)oct-2-ene-2-carboxylic acid ammonium dihydrogen phosphate, and (−)-(6R,7R)-7-((Z)-2-(2-aminothiazole-4-yl)-2-hydroxyimino-acetylamino)-8-oxo-3-vinyl-5-thia-1-azabicyclo (4.2.0)oct-2-ene-2-carboxylic acid cesium dihydrogen phosphate. 
         [0024]    Advantages of the invention are summarized below. 
         [0025]    The cefdinir sulfate double salt and cefdinir phosphate double salt have good stability, good solubility, and thus the bioavailability thereof have been enhanced greatly. The double salts can be administered orally or by injection. 
         [0026]    The melting point of the double salts is still under study. Above 203° C., the double salts turn yellow, above 270° C., turn brown, and at 303° C., the salts don&#39;t disappear. The sodium cefdinir disclosed in CN 1,415,615A turns yellow at about 160° C., and turns black at 190° C. and finally disappear. Obviously, in contrast to the prior art, the double salts of the invention have better stability. 
         [0027]    Cefdinir has a broad antimicrobial spectrum and good antibacterial activity against gram-positive and -negative bacteria, e.g.,  Moraxella catarrhalis, Klebsiella pneumoniae,  proteobacteria, and  Escherichia coli.  Furthermore, cefdinir is stable to β-lactamoase and can kill some bacteria capable of synthesizing enzyme. With good water solubility, the double salts can be prepared into solid formulations or injections. 
         [0028]    The method for producing the double salts has a stable process and high manufacturing feasibility. The compound (double salts) has good solubility and high bioavailability, and exhibits high activity and high efficiency in clinical practice. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0029]    For further illustrating the invention, experiments detailing a cefdinir double salt and preparation method thereof are described below. It should be noted that the following examples are intended to describe and not to limit the invention. 
       EXAMPLE 1 
       [0030]    To a 100 mL reaction flask, 2.0 g of cefdinir and 20 mL of anhydrous methanol were added and stirred to yield a uniform mixture. 0.496 g of sulfuric acid was diluted with 10 mL of anhydrous methanol, and the resulting solution was dripped slowly into the uniform mixture under an ice bath condition. After the solution was clear, 0.273 g of sodium methoxide was added and allowed to react for 15 min. Subsequently, methanol was distilled off at 35° C. under reduced pressure. The solution was concentrated, crystallized with ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir sodium hydrogen sulfate obtained. The yield was 99%, with a content of 98.7% and purity greater than or equal to 99%. 
       EXAMPLE 2 
       [0031]    To a 100 mL reaction flask, 2.0 g of cefdinir and 20 mL of anhydrous ethanol were added and stirred to yield a uniform mixture. 0.496 g of sulfuric acid was diluted with 10 mL of anhydrous ethanol, and the resulting solution was dripped slowly into the uniform mixture under an ice bath condition. After the solution was clear, 0.1365 g of sodium methoxide was added and allowed to react for 15 min. Subsequently, ethanol was distilled off at 35° C. under reduced pressure. The solution was concentrated, crystallized with ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir sodium hydrogen (0.5) sulfate (1.5) obtained. The yield was 98.1%, with a content of 98.4% and purity greater than or equal to 99%. 
       EXAMPLE 3 
       [0032]    To a 100 mL reaction flask, 2.0 g of cefdinir and 20 mL of anhydrous methanol were added and stirred to yield a uniform mixture. 0.496 g of sulfuric acid was diluted with 10 mL of anhydrous methanol, and the resulting solution was dripped slowly into the uniform mixture under an ice bath condition. After the solution was clear, 0.355 g of potassium methoxide was added and allowed to react for 15 min. Subsequently, methanol was distilled off at 40° C. under reduced pressure. The solution was concentrated, crystallized with ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir potassium hydrogen sulfate obtained. The yield was 98%, with a content of 98.3% and purity greater than or equal to 99%. 
       EXAMPLE 4 
       [0033]    To a 100 mL reaction flask, 2.0 g of cefdinir and 20 mL of anhydrous acetone were added and stirred to yield a uniform mixture. 0.496 g of sulfuric acid was diluted with 10 mL of anhydrous acetone, and the resulting solution was dripped slowly into the uniform mixture under an ice bath condition. After the solution was clear, 0.1775 g of potassium methoxide was added and allowed to react for 15 min. Subsequently, acetone was distilled off at 40° C. under reduced pressure. The solution was concentrated, crystallized with ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir potassium hydrogen (0.5) sulfate (1.5) obtained. The yield was 96.5%, with a content of 97.1% and purity greater than or equal to 99%. 
       EXAMPLE 5 
       [0034]    To a 100 mL reaction flask, 2.0 g of cefdinir and 20 mL of anhydrous methanol were added and stirred to yield a uniform mixture. 0.496 g of sulfuric acid was diluted with 10 mL of anhydrous methanol, and the resulting solution was dripped slowly into the uniform mixture under an ice bath condition. After the solution was clear, 0.086 g of ammonia gas was inflated and allowed to react under sealing condition for 15 min. Subsequently, methanol was distilled off at 30° C. under reduced pressure. The solution was concentrated, crystallized with hexane using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir ammonium hydrogen sulfate obtained. The yield was 96.4%, with a content of 98.6% and purity greater than or equal to 99%. 
       EXAMPLE 6 
       [0035]    To a 100 mL reaction flask, 2.0 g of cefdinir and 20 mL of anhydrous ethanol were added and stirred to yield a uniform mixture. 0.496 g of sulfuric acid was diluted with 10 mL of anhydrous ethanol, and the resulting solution was dripped slowly into the uniform mixture under an ice bath condition. After the solution was clear, 0.043 g of ammonia gas was inflated and allowed to react under sealing condition for 15 min. Subsequently, ethanol was distilled off at 30° C. under reduced pressure. The solution was concentrated, crystallized with petroleum ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir ammonium hydrogen (0.5) sulfate (1.5) obtained. The yield was 96.7%, with a content of 97.7% and purity greater than or equal to 99%. 
       EXAMPLE 7 
       [0036]    To a 100 mL reaction flask, 2.0 g of cefdinir and 20 mL of anhydrous ethanol were added and stirred to yield a uniform mixture. 0.516 g of sodium hydrogen sulfate was mixed with 30 mL of anhydrous ethanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, ethanol was distilled off at 35° C. under reduced pressure. The solution was concentrated, crystallized with ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir sodium hydrogen sulfate obtained. The yield was 97%, with a content of 98.4% and purity greater than or equal to 99%. 
       EXAMPLE 8 
       [0037]    To a 100 mL reaction flask, 2.0 g of cefdinir and 20 mL of anhydrous methanol were added and stirred to yield a uniform mixture. 0.689 g of potassium hydrogen sulfate was mixed with 30 mL of anhydrous methanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, methanol was distilled off at 35° C. under reduced pressure. The solution was concentrated, crystallized with petroleum ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir potassium hydrogen sulfate obtained. The yield was 97%, with a content of 98% and purity greater than or equal to 99%. 
       EXAMPLE 9 
       [0038]    To a 100 mL reaction flask, 2.0 g of cefdinir and 20 mL of anhydrous methanol were added and stirred to yield a uniform mixture. 0.582 g of ammonium hydrogen sulfate was mixed with 30 mL of anhydrous methanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, methanol was distilled off at 35° C. under reduced pressure. The solution was concentrated, crystallized with ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir ammonium hydrogen sulfate obtained. The yield was 98%, with a content of 98.7% and purity greater than or equal to 99%. 
       EXAMPLE 10 
       [0039]    To a 100 mL reaction flask, 2.0 g of cefdinir and 20 mL of anhydrous ethanol were added and stirred to yield a uniform mixture. 0.496 g of phosphoric acid was diluted with 10 mL of anhydrous ethanol, and the resulting solution was dripped slowly into the uniform mixture under an ice bath condition. After the solution was clear, 0.273 g of sodium methoxide was added and allowed to react for 15 min. Subsequently, ethanol was distilled off at 35° C. under reduced pressure. The solution was concentrated, crystallized with ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir sodium dihydrogen phosphate obtained. The yield was 96%, with a content of 98.5% and purity greater than or equal to 99%. 
       EXAMPLE 11 
       [0040]    To a 100 mL reaction flask, 2.0 g of cefdinir and 20 mL of anhydrous methanol were added and stirred to yield a uniform mixture. 0.4966 g of phosphoric acid was diluted with 10 mL of anhydrous methanol, and the resulting solution was dripped slowly into the uniform mixture under an ice bath condition. After the solution was clear, 0.355 g of potassium methoxide was added and allowed to react for 15 min. Subsequently, methanol was distilled off at 40° C. under reduced pressure. The solution was concentrated, crystallized with petroleum ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir potassium dihydrogen phosphate obtained. The yield was 96.8%, with a content of 98.7% and purity greater than or equal to 99%. 
       EXAMPLE 12 
       [0041]    To a 100 mL reaction flask, 2.0 g of cefdinir and 20 mL of anhydrous acetone were added and stirred to yield a uniform mixture. 0.4966 g of phosphoric acid was diluted with 10 mL of anhydrous acetone, and the resulting solution was dripped slowly into the uniform mixture under an ice bath condition. After the solution was clear, 0.086 g of ammonia gas was inflated and allowed to react for 25 min under sealing condition. Subsequently, acetone was distilled off at 30° C. under reduced pressure. The solution was concentrated, crystallized with ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir ammonium dihydrogen phosphate obtained. The yield was 92.4%, with a content of 98.6% and purity greater than or equal to 99%. 
       EXAMPLE 13 
       [0042]    To a 100 mL reaction flask, 2.0 g of cefdinir and 20 mL of anhydrous methanol were added and stirred to yield a uniform mixture. 0.607 g of sodium dihydrogen phosphate was mixed with 40 mL of anhydrous methanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, methanol was distilled off at 35° C. under reduced pressure. The solution was concentrated, crystallized with hexane using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir sodium dihydrogen phosphate obtained. The yield was 96.8%, with a content of 98.7% and purity greater than or equal to 99%. 
       EXAMPLE 14 
       [0043]    To a 100 mL reaction flask, 2.0 g of cefdinir and 20 mL of dimethylformamide (DMF) were added and stirred to yield a uniform mixture. 0.607 g of sodium dihydrogen phosphate was mixed with 40 mL of DMF, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, DMF was distilled off at 35° C. under reduced pressure. The solution was concentrated, crystallized with hexane using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir sodium dihydrogen phosphate obtained. The yield was 96.7%, with a content of 97.5% and purity greater than or equal to 99%. 
       EXAMPLE 15 
       [0044]    To a 100 mL reaction flask, 2.0 g of cefdinir and 20 mL of anhydrous ethanol were added and stirred to yield a uniform mixture. 0.688 g of potassium dihydrogen phosphate was mixed with 30 mL of anhydrous ethanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, ethanol was distilled off at 35° C. under reduced pressure. The solution was concentrated, crystallized with petroleum ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir potassium dihydrogen phosphate obtained. The yield was 93.6%, with a content of 98.7% and purity greater than or equal to 99%. 
       EXAMPLE 16 
       [0045]    To a 100 mL reaction flask, 2.0 g of cefdinir and 20 mL of dimethylsulfoxide (DMSO) were added and stirred to yield a uniform mixture. 0.688 g of potassium dihydrogen phosphate was mixed with 30 mL of DMSO, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, DMSO was distilled off at 35° C. under reduced pressure. The solution was concentrated, crystallized with petroleum ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir potassium dihydrogen phosphate obtained. The yield was 95.4%, with a content of 97.2% and purity greater than or equal to 99%. 
       EXAMPLE 17 
       [0046]    To a 100 mL reaction flask, 2.0 g of cefdinir and 20 mL of anhydrous ethanol were added and stirred to yield a uniform mixture. 0.582 g of ammonium dihydrogen phosphate was mixed with 30 mL of anhydrous ethanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, ethanol was distilled off at 35° C. under reduced pressure. The solution was concentrated, crystallized with ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir ammonium dihydrogen phosphate obtained. The yield was 96.4%, with a content of 98.7% and purity greater than or equal to 99%. 
       EXAMPLE 18 
       [0047]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous ethanol were added and stirred to yield a uniform mixture. 0.496 g of sulfuric acid was mixed with 10 mL of anhydrous ethanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of sodium ethoxide was added and allowed to react for 15 min. Subsequently, ethanol was distilled off at 35° C. under reduced pressure. The solution was concentrated, crystallized with ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir sodium hydrogen sulfate obtained. The yield was 98.2%, with a content of 98.3% and purity greater than or equal to 99%. 
       EXAMPLE 19 
       [0048]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous ethanol were added and stirred to yield a uniform mixture. 0.496 g of sulfuric acid was mixed with 10 mL of anhydrous ethanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 2.53 mmol of potassium propoxide was added and allowed to react for 15 min. Subsequently, ethanol was distilled off at 35° C. under reduced pressure. The solution was concentrated, crystallized with ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir potassium hydrogen (0.5) sulfate (1.5) obtained. The yield was 98.3%, with a content of 98.8% and purity greater than or equal to 99%. 
       EXAMPLE 20 
       [0049]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous acetone were added and stirred to yield a uniform mixture. 0.496 g of sulfuric acid was mixed with 10 mL of anhydrous acetone, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of cesium butoxide was added and allowed to react for 15 min. Subsequently, acetone was distilled off at 40° C. under reduced pressure. The solution was concentrated, crystallized with ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir cesium hydrogen sulfate obtained. The yield was 97.3%, with a content of 98.5% and purity greater than or equal to 99%. 
       EXAMPLE 21 
       [0050]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous acetone were added and stirred to yield a uniform mixture. 0.496 g of sulfuric acid was mixed with 10 mL of anhydrous acetone, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 2.53 mmol of potassium isopropoxide was added and allowed to react for 15 min. Subsequently, acetone was distilled off at 40° C. under reduced pressure. The solution was concentrated, crystallized with ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir potassium hydrogen (0.5) sulfate (1.5) obtained. The yield was 96.5%, with a content of 97.1% and purity greater than or equal to 99%. 
       EXAMPLE 22 
       [0051]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous methanol were added and stirred to yield a uniform mixture. 0.496 g of sulfuric acid was mixed with 10 mL of anhydrous methanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 2.53 mmol of ammonia water was added and allowed to react for 15 min. Subsequently, methanol was distilled off at 30° C. under reduced pressure. The solution was concentrated, crystallized with hexane using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir ammonium hydrogen sulfate obtained. The yield was 96.4%, with a content of 98.6% and purity greater than or equal to 99%. 
       EXAMPLE 23 
       [0052]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous ethanol were added and stirred to yield a uniform mixture. 0.496 g of sulfuric acid was mixed with 10 mL of anhydrous ethanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of sodium tert-butoxide was added and allowed to react for 15 min. Subsequently, ethanol was distilled off at 35° C. under reduced pressure. The solution was concentrated, crystallized with ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir sodium hydrogen sulfate obtained. The yield was 98.6%, with a content of 97.3% and purity greater than or equal to 99%. 
       EXAMPLE 24 
       [0053]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous ethanol were added and stirred to yield a uniform mixture. 0.496 g of sulfuric acid was mixed with 10 mL of anhydrous ethanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 2.53 mmol of potassium acetate was added and allowed to react for 15 min. Subsequently, ethanol was distilled off at 35° C. under reduced pressure. The solution was concentrated, crystallized with ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir potassium hydrogen (0.5) sulfate (1.5) obtained. The yield was 95.3%, with a content of 97.8% and purity greater than or equal to 99%. 
       EXAMPLE 25 
       [0054]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous acetone were added and stirred to yield a uniform mixture. 0.496 g of sulfuric acid was mixed with 10 mL of anhydrous acetone, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of cesium propionate was added and allowed to react for 15 min. Subsequently, acetone was distilled off at 40° C. under reduced pressure. The solution was concentrated, crystallized with ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir cesium hydrogen sulfate obtained. The yield was 96.3%, with a content of 98.4% and purity greater than or equal to 99%. 
       EXAMPLE 26 
       [0055]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous acetone were added and stirred to yield a uniform mixture. 0.496 g of sulfuric acid was mixed with 10 mL of anhydrous acetone, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 2.53 mmol of sodium isopropoxide was added and allowed to react for 15 min. Subsequently, acetone was distilled off at 40° C. under reduced pressure. The solution was concentrated, crystallized with ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir sodium hydrogen (0.5) sulfate (1.5) obtained. The yield was 96.5%, with a content of 97.1% and purity greater than or equal to 99%. 
       EXAMPLE 27 
       [0056]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous ethanol were added and stirred to yield a uniform mixture. 0.496 g of sulfuric acid was mixed with 10 mL of anhydrous ethanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of sodium tert-butyrate was added and allowed to react for 15 min. Subsequently, ethanol was distilled off at 35° C. under reduced pressure. The solution was concentrated, crystallized with ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir sodium hydrogen sulfate obtained. The yield was 96.6%, with a content of 96.7% and purity greater than or equal to 99%. 
       EXAMPLE 28 
       [0057]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous ethanol were added and stirred to yield a uniform mixture. 0.496 g of phosphoric acid was mixed with 10 mL of anhydrous ethanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of sodium ethoxide was added and allowed to react for 15 min. Subsequently, ethanol was distilled off at 35° C. under reduced pressure. The solution was concentrated, crystallized with ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir sodium dihydrogen phosphate obtained. The yield was 96.8%, with a content of 97.5% and purity greater than or equal to 99%. 
       EXAMPLE 29 
       [0058]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous methanol were added and stirred to yield a uniform mixture. 0.4966 g of phosphoric acid was mixed with 10 mL of anhydrous methanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of potassium propoxide was added and allowed to react for 15 min. Subsequently, methanol was distilled off at 40° C. under reduced pressure. The solution was concentrated, crystallized with petroleum ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir potassium dihydrogen sulfate obtained. The yield was 97.3%, with a content of 96.5% and purity greater than or equal to 99%. 
       EXAMPLE 30 
       [0059]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous acetone were added and stirred to yield a uniform mixture. 0.4966 g of phosphoric acid was mixed with 10 mL of anhydrous acetone, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of ammonia water was added and allowed to react for 25 min. Subsequently, acetone was distilled off at 30° C. under reduced pressure. The solution was concentrated, crystallized with ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir ammonium dihydrogen phosphate obtained. The yield was 95.4%, with a content of 96.6% and purity greater than or equal to 99%. 
       EXAMPLE 31 
       [0060]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous ethanol were added and stirred to yield a uniform mixture. 0.496 g of phosphoric acid was mixed with 10 mL of anhydrous ethanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of cesium butoxide was added and allowed to react for 15 min. Subsequently, ethanol was distilled off at 35° C. under reduced pressure. The solution was concentrated, crystallized with ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir cesium dihydrogen phosphate obtained. The yield was 96.8%, with a content of 97.5% and purity greater than or equal to 99%. 
       EXAMPLE 32 
       [0061]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous methanol were added and stirred to yield a uniform mixture. 0.4966 g of phosphoric acid was mixed with 10 mL of anhydrous methanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of potassium isopropoxide was added and allowed to react for 15 min. Subsequently, methanol was distilled off at 40° C. under reduced pressure. The solution was concentrated, crystallized with petroleum ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir potassium dihydrogen phosphate obtained. The yield was 97.5%, with a content of 97.3% and purity greater than or equal to 99%. 
       EXAMPLE 33 
       [0062]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous ethanol were added and stirred to yield a uniform mixture. 0.496 g of phosphoric acid was mixed with 10 mL of anhydrous ethanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of sodium tert-butoxide was added and allowed to react for 15 min. Subsequently, ethanol was distilled off at 35° C. under reduced pressure. The solution was concentrated, crystallized with petroleum ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir sodium dihydrogen phosphate obtained. The yield was 98.1%, with a content of 97.6% and purity greater than or equal to 99%. 
       EXAMPLE 34 
       [0063]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous methanol were added and stirred to yield a uniform mixture. 0.4966 g of phosphoric acid was mixed with 10 mL of anhydrous methanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of potassium acetate was added and allowed to react for 15 min. Subsequently, methanol was distilled off at 40° C. under reduced pressure. The solution was concentrated, crystallized with petroleum ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir potassium dihydrogen phosphate obtained. The yield was 93.6%, with a content of 96.3% and purity greater than or equal to 99%. 
       EXAMPLE 35 
       [0064]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous methanol were added and stirred to yield a uniform mixture. 0.4966 g of phosphoric acid was mixed with 10 mL of anhydrous methanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of sodium acetate was added and allowed to react for 15 min. Subsequently, methanol was distilled off at 40° C. under reduced pressure. The solution was concentrated, crystallized with petroleum ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir sodium dihydrogen phosphate obtained. The yield was 92.6%, with a content of 97.3% and purity greater than or equal to 99%. 
       EXAMPLE 36 
       [0065]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous ethanol were added and stirred to yield a uniform mixture. 0.496 g of phosphoric acid was mixed with 10 mL of anhydrous ethanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of sodium tert-propionate was added and allowed to react for 15 min. Subsequently, ethanol was distilled off at 35° C. under reduced pressure. The solution was concentrated, crystallized with petroleum ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir sodium dihydrogen phosphate obtained. The yield was 95.2%, with a content of 98.6% and purity greater than or equal to 99%. 
       EXAMPLE 37 
       [0066]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous methanol were added and stirred to yield a uniform mixture. 0.4966 g of phosphoric acid was mixed with 10 mL of anhydrous methanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of potassium butyrate was added and allowed to react for 15 min. Subsequently, methanol was distilled off at 40° C. under reduced pressure. The solution was concentrated, crystallized with petroleum ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir potassium dihydrogen phosphate obtained. The yield was 92.6%, with a content of 98.3% and purity greater than or equal to 99%. 
       EXAMPLE 38 
       [0067]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous methanol were added and stirred to yield a uniform mixture. 0.4966 g of phosphoric acid was mixed with 10 mL of anhydrous methanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of cesium butyrate was added and allowed to react for 15 min. Subsequently, methanol was distilled off at 40° C. under reduced pressure. The solution was concentrated, crystallized with petroleum ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir potassium dihydrogen phosphate obtained. The yield was 92.6%, with a content of 97.3% and purity greater than or equal to 99%. 
       EXAMPLE 39 
       [0068]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous ethanol were added and stirred to yield a uniform mixture. 0.496 g of phosphoric acid was mixed with 10 mL of anhydrous ethanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of sodium tert-hydroxide was added and allowed to react for 15 min. Subsequently, ethanol was distilled off at 35° C. under reduced pressure. The solution was concentrated, crystallized with ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir sodium dihydrogen phosphate obtained. The yield was 97.2%, with a content of 96.2% and purity greater than or equal to 99%. 
       EXAMPLE 40 
       [0069]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous methanol were added and stirred to yield a uniform mixture. 0.4966 g of phosphoric acid was mixed with 10 mL of anhydrous methanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of potassium hydroxide was added and allowed to react for 15 min. Subsequently, methanol was distilled off at 40° C. under reduced pressure. The solution was concentrated, crystallized with petroleum ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir potassium dihydrogen phosphate obtained. The yield was 90.6%, with a content of 97.7% and purity greater than or equal to 99%. 
       EXAMPLE 41 
       [0070]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous methanol were added and stirred to yield a uniform mixture. 0.4966 g of phosphoric acid was mixed with 10 mL of anhydrous methanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of cesium hydroxide was added and allowed to react for 15 min. Subsequently, methanol was distilled off at 40° C. under reduced pressure. The solution was concentrated, crystallized with petroleum ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir cesium dihydrogen phosphate obtained. The yield was 89.6%, with a content of 98.3% and purity greater than or equal to 99%. 
       EXAMPLE 42 
       [0071]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous ethanol were added and stirred to yield a uniform mixture. 5.06 mmol of sulfuric acid was mixed with 10 mL of anhydrous ethanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of sodium tert-butoxide was added and allowed to react for 15 min. Subsequently, ethanol was distilled off at 35° C. under reduced pressure. The solution was concentrated, crystallized with ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir sodium hydrogen sulfate obtained. The yield was 96.2%, with a content of 98.5% and purity greater than or equal to 99%. 
       EXAMPLE 43 
       [0072]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous methanol were added and stirred to yield a uniform mixture. 5.06 mmol of sulfuric acid was mixed with 10 mL of anhydrous methanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of potassium hydroxide was added and allowed to react for 15 min. Subsequently, methanol was distilled off at 40° C. under reduced pressure. The solution was concentrated, crystallized with petroleum ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir sodium hydrogen sulfate obtained. The yield was 90.6%, with a content of 97.7% and purity greater than or equal to 99%. 
       EXAMPLE 44 
       [0073]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous ethanol were added and stirred to yield a uniform mixture. 5.06 mmol of sulfuric acid was mixed with 10 mL of anhydrous ethanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of cesium hydroxide was added and allowed to react for 15 min. Subsequently, ethanol was distilled off at 40° C. under reduced pressure. The solution was concentrated, crystallized with petroleum ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir cesium hydrogen sulfate obtained. The yield was 87.6%, with a content of 98.7% and purity greater than or equal to 99%. 
       EXAMPLE 45 
       [0074]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous methanol were added and stirred to yield a uniform mixture. 5.06 mmol of sulfuric acid was mixed with 10 mL of anhydrous methanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of ammonium acetate was added and allowed to react for 15 min. Subsequently, methanol was distilled off at 40° C. under reduced pressure. The solution was concentrated, crystallized with petroleum ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir ammonium hydrogen sulfate obtained. The yield was 91.6%, with a content of 98.7% and purity greater than or equal to 99%. 
       EXAMPLE 46 
       [0075]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous ethanol were added and stirred to yield a uniform mixture. 5.06 mmol of sulfuric acid was mixed with 10 mL of anhydrous ethanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of ammonium propionate was added and allowed to react for 15 min. Subsequently, ethanol was distilled off at 40° C. under reduced pressure. The solution was concentrated, crystallized with petroleum ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir ammonium hydrogen sulfate obtained. The yield was 89.6%, with a content of 98.1% and purity greater than or equal to 99%. 
       EXAMPLE 47 
       [0076]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous ethanol were added and stirred to yield a uniform mixture. 0.496 g of phosphoric acid was mixed with 10 mL of anhydrous ethanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of ammonium acetate was added and allowed to react for 15 min. Subsequently, methanol was distilled off at 35° C. under reduced pressure. The solution was concentrated, crystallized with ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir ammonium dihydrogen phosphate obtained. The yield was 94.2%, with a content of 97.6% and purity greater than or equal to 99%. 
       EXAMPLE 48 
       [0077]    To a 100 mL reaction flask, 5.06 mmol of cefdinir and 20 mL of anhydrous ethanol were added and stirred to yield a uniform mixture. 0.496 g of phosphoric acid was mixed with 10 mL of anhydrous ethanol, and the resulting solution was dripped slowly into the uniform mixture. After the solution was clear, 5.06 mmol of ammonium acetate was added and allowed to react for 15 min. Subsequently, methanol was distilled off at 35° C. under reduced pressure. The solution was concentrated, crystallized with petroleum ether using a dropping funnel, and stirred to yield a solid. The solid was dried and cefdinir ammonium dihydrogen phosphate obtained. The yield was 89.2%, with a content of 98.6% and purity greater than or equal to 99%. 
       EXAMPLE 49  
     INDUSTRIAL APPLICABILITY   
       [0078]    Cefdinir is hard soluble in water. The solubility of the compounds of the invention has been increased by 100 times. Table 1 lists the solubility of the compounds of the invention. 
         [0000]    
       
         
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 No. 
                 Compound 
                 Solubility 
               
               
                   
               
             
             
               
                 1 
                 Cefdinir sodium hydrogen (0.5) sulfate (1.5) 
                 Soluble 
               
               
                 2 
                 Cefdinir potassium hydrogen (0.5) sulfate (1.5) 
                 Soluble 
               
               
                 3 
                 Cefdinir ammonium hydrogen (0.5) sulfate (1.5) 
                 Soluble 
               
               
                 4 
                 Cefdinir sodium hydrogen sulfate 
                 Slightly soluble 
               
               
                 5 
                 Cefdinir potassium hydrogen sulfate 
                 Slightly soluble 
               
               
                 6 
                 Cefdinir ammonium hydrogen sulfate 
                 Slightly soluble 
               
               
                 7 
                 Cefdinir sodium dihydrogen phosphate 
                 Slightly soluble 
               
               
                 8 
                 Cefdinir potassium dihydrogen phosphate 
                 Slightly soluble 
               
               
                 9 
                 Cefdinir ammonium dihydrogen phosphate 
                 Slightly soluble 
               
               
                   
               
             
          
         
       
     
         [0079]    Beagles, half male and half female, with body weight of 10 kg, were starved for 12 hrs and only water fed. The compounds of the invention were formulated into capsules containing 200 mg of cefdinir and fed to beagles by intragastric administration. The control group was administered with conventional cefdinir capsules. 3 hrs later, the beagles were fed with common food. At 0 h, 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 4 h, 6 h, 8 h, and 10 h after intragastric administration, 0.5 mL of venous blood was collected respectively to measure the concentration of cefdinir. The results are listed in Table 2. 
         [0000]    
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Bioavailability comparison between compounds of the invention 
               
               
                 and conventional cefdinir capsule 
               
             
          
           
               
                   
                   
                 Time  
                 AUC 
                 Bioavail- 
               
               
                   
                   
                 to 
                 (0-10) 
                 ability 
               
               
                   
                 Cmax 
                 peak 
                 (μg · h/ 
                 percentage 
               
               
                 Drugs 
                 (μg/mL) 
                 (h) 
                 mL) 
                 increase 
               
               
                   
               
               
                 Conventional cefdinir capsule 
                 21.80 
                 3   
                 102.11 
                 / 
               
               
                 Cefdinir sodium hydrogen sulfate 
                 65.43 
                 3   
                 255.27 
                 149% 
               
               
                 Cefdinir sodium hydrogen (0.5) 
                 50.23 
                 3   
                 239.96 
                 135% 
               
               
                 sulfate (1.5) 
                   
                   
                   
                   
               
               
                 Cefdinir potassium hydrogen  
                 54.13 
                 2.5 
                 261.41 
                 156% 
               
               
                 sulfate  
                   
                   
                   
                   
               
               
                 Cefdinir potassium  
                 47.65 
                 3   
                 213.40 
                 109% 
               
               
                 hydrogen (0.5) sulfate (1.5) 
                   
                   
                   
                   
               
               
                 Cefdinir ammonium hydrogen  
                 43.63 
                 3   
                 202.18 
                  98% 
               
               
                 sulfate 
                   
                   
                   
                   
               
               
                 Cefdinir ammonium  
                 34.12 
                 2.5 
                 160.31 
                  57% 
               
               
                 hydrogen (0.5) sulfate (1.5) 
                   
                   
                   
                   
               
               
                 Cefdinir sodium dihydrogen 
                 27.28 
                 2.5 
                 123.55 
                  20% 
               
               
                 phosphate 
                   
                   
                   
                   
               
               
                 Cefdinir potassium dihydrogen 
                 30.37 
                 3   
                 152.15 
                  49% 
               
               
                 phosphate 
               
               
                   
               
             
          
         
       
     
         [0080]    As shown in Table 2, the bioavailability of the compounds of the invention has been improved by 20% compared with that of conventional cefdinir capsules. The largest increase was 156%. 
         [0081]    The production process of cefdinir sodium hydrogen sulfate of Example 1 and cefdinir potassium hydrogen sulfate of Example 3 is stable and thus the bioavailability thereof has improved a lot. 
         [0082]    While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.