Abstract:
The present invention relates to a process for preparing (3R,4S)-3-[[[R]-1′-t-butyldimethylsilyloxy]ethyl]-4-[(R)-1″-carboxyethyl]-2-azetidinone (beta-methylazetidin-2-one; 4-BMA), a key intermediate for the synthesis of carbapenem and penem antibiotics. Specifically, the present invention relates to a process comprising first, the preparation of a chiral auxiliary from cheap L-Phenylalaninol, and then the preparation of 4-BMA in high yield and high selectivity, under industrially mild condition.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a manufacturing method of an intermediate for the synthesis of penems or carbapenems, particularly A method for manufacturing an intermediate (3R,4S)-3-[[[R]-1′-t-butyldimethylsilyloxy]ethyl]-4-[(R)-1″-carboxyethyl]-2-azetidinone (beta-methylazetidin-2-one; 4-BMA) and a chiral auxiliary. 
         [0002]    4-BMA has been known in the art as an intermediate for the synthesis of 1 β-methylcarbapenem which exhibits potent antibacterial activity. Many types of carbapenems can be prepared from the 4-BMA, typical examples of which is Meropenem, Ertapenem, and Doripenem: 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    exhibits a broad spectrum of antibacterial activity against gram-positive and gram-negative strains. In particular, it has an excellent antimicrobial effect in controlling gram-negative strains and metalactamase-producing strains. Also, the presence of the beta-methyl group makes Meropenem, Ertapenem, and Doripenem to have better stability against dehydropeptidase-I (DRP-I) in the kidney compared to the existing carbapenem antibacterial agent of Imipenem (Antimicrobial Agents and Chemotheraphym 33, 215-222 (1984). Thus, in contrast to Imipenem, they does not have to be administered along with cilastatin to maintain stability in the body, and can be administered alone. 
         [0003]    Various methods for preparing the 4-BMA, a key intermediate for manufacturing important medicines, such as carbapenem and penem antibiotics, have been developed. In earlier researches, 1″-position hydrogen atom in the acetic acid residue at 4-position of the betamethyl compound was removed by a strong base, and methyl group was introduced thereto [Heterocycles, 21, 29 (1984)]. However, this method posed problems of essentially using lithium diisopropylamide that is difficult to handle, and of having to be carried out under an extremely low temperature, such as −78° C. There is also the disadvantage that the compound having 1 a-methyl group of the following formula as followed 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    was produced in large amounts as a by-product (β/α=4/l). 
         [0004]    Several approaches have been tried to overcome such problems, and the most advantageous was to introduce p-methyl group using a chiral auxiliary. [Tetrahedron 52, 331-375, (1996)] 
       &lt;Earlier Methods for the Preparation of Chiral Auxiliaries&gt; 
       [0005]    In most methods for preparing chiral auxiliaries for the synthesis of 4-BMA, propionyl group is introduced as an acyl group. A halide compound, which is not easy to handle, such as propionyl bromide, is used for introducing propionyl group, and a metal catalyst, such as n-butyllithimn, is used for the coupling reaction (JP2789190, DE3632916, U.S. Pat. No. 5,104,984, KR940008748, U.S. Pat. No. 5,231,179). 
       &lt;Earlier Methods for the Preparation of 4-BMA&gt; 
       [0006]    For the coupling reaction of (3R,4R)-4-acetoxy-3-[(R)-1′-(t-butyldimethylsilyl)oxy)ethyl]-2-azetidinone (4-AA) with the chiral auxiliary, trimethylchlorosilane (TMSCl)/lithium diisopropylamide (LDA), tintriflate [Sn(OTf)2], diethylborotriflate (Et2BOTf)/zinc bromide (ZnBr2), tert-butyldimethylsilyltriflate (TBDMSOTf)/zinc chloride (ZnCl2), LDA-Zr(Cp) 2Ch, etc. have been used (EP0974582, U.S. Pat. No. 5,104,984, J AM Chern. Sac, 1986, 108, 4675, etc.). However, these substances are explosive metal catalysts, or should be used in an extremely low temperature (−78° C.) reaction. Thus, it is difficult and uneconomical to use them industrially. 
         [0007]    As summarized above, several methods for preparing 4-BMA have been reported, but a method suitable for preparing the desired compound in high yield and high selectivity using substances that are easy to handle in industrial production has not yet been developed. 
       SUMMARY OF THE INVENTION 
       [0008]    The primary object of the present invention is to provide a chiral auxiliary from cheap starting material in high yield under mild conditions, and in obtaining good quality of 4-BMA of β/α ratio. 
         [0009]    Another object of the present invention is to provide a new process for preparing the 4-BMA that can be effectively used as an intermediate for preparing carbapenem or penem antibiotics. 
         [0010]    Another object of the present invention is to provide a new process for preparing the chiral auxiliary effectively used for stereoselectively preparing the 4-BMA. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The structure and the technical means adopted by the present invention to achieve the above and other objects can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings, wherein 
           [0012]      FIG. 1  is a schematic drawing showing chemical equation of Example 1 
           [0013]      FIG. 2  is a schematic drawing showing chemical equation of Example 2a 
           [0014]      FIG. 3  is a schematic drawing showing chemical equation of Example 2b 
           [0015]      FIG. 4  is a schematic drawing showing chemical equation of Example 3a.3b 
           [0016]      FIG. 5  is a schematic drawing showing chemical equation of Example 4a 
           [0017]      FIG. 6  is a schematic drawing showing chemical equation of Example 4b 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0018]    A manufacturing method is described as following: 
       Example 1 
     Preparation of (S)-4-benzyloxazolidine-2-one-(2) 
       [0019]    Refer to  FIG. 1 , to a mixture of (2S)-2-amino-3-phenyl-1-propanol (649 g; 4.29 mol) and diethyl carbonate (1040 ml; 8.58 mol), anhydrous potassium carbonate (20 g; 0.14 mol) was added, and the mixture was stirred at 120 to 130° C. for 3 hours. After cooling, to the resulting mixture 1N hydrochloric acid (1.5 L) and ethyl acetate (about 20 L) were added and stirred. The organic layer was separated and washed with brine. Distilling off the solvent under reduced pressure gave (4S)-4-benzyloxazolidin-2-one (760 g, quantitative yield) as a colorless solid. The sample for analysis obtained by recrystallization from a mixed solvent of cyclohexane and toluene (1:1). Colorless crystals. M.P., 88-89° C. [α] 20   d  −63° (c=1.0 in CHC1 3 ); IR (KBr): 1751, 1710, 1408, 1246, 1020, 944, 760, 710, 618, 532;  1 H-NMR (CDC1 3 ): δ7.33 (t, 3H), 7.26 (t, 1H), 7.16 (d, 2H), 5.39 (br, 1H), 4.44 (t, 1H), 4.14 (dd, 1H), 4.07 (m, 1H), 2.86 (d, 2H); (IR, bs), 7.29 (5R, m); +Mass m/e: 177 (M); Calculated: C, 67.78%; H, 6.26%; N, 7.90%. Found: C, 67.82%; H, 6.34%; N, 7.86% 
       Example 2a 
     Preparation of (S)-4-benzyl-3-propionyloxazolidine-2-one-(2) 
       [0020]    Refer to  FIG. 2 , the compound (12) prepared in Example 1 (120 g) was dissolved in methane dichloride (984 ml), and cooled to 0° C. ZnCl 2  (52 g) was added, triethylamine (101 g) was then added, and the resulting mixture was stirred over a 30 min. Propionic acid anhydride (96.9 g) was slowly added over a 30 min. time period. The reaction mixture was heated to reflux temperature and stirred for 1-1.5 hours. The reaction solution was cooled, water (300 ml) was added, and the mixture was stirred for 30 min. The methane dichloride phases were separated, and extracted once again with 1.5N hydrochloride solution (300 ml). The organic solution was washed once again with aqueous 5% sodium bicarbonate solution (240 ml). The organic solution was distilled by vacuum to remove methane dichloride until nothing come out. Heptanes was added to the resulting solution and stirred for 1 hours at −5 to 0° C., which was then filtered and dried to produce the white solid compound (2) (150 g, Yield 95%) 
         [0021]      1 H-NMR 0 (CDC1 3 ): δ7.33 (dd, 2H) 7.30 (m, 1H), 7.19 (d, 2H), 4.65 (m, 1H), 4.19-4.14 (m, 2H), 3.29 (dd, 1H), 3.00-2.89 (m, 2H), 2.75 (dd, 1H), 1.19 (t, 3H) 
       Example 2b 
     Preparation of (S)-4-benzyl-3-propionyloxazolidine-2-one-(2) 
       [0022]    Refer to  FIG. 3 , the compound (12) prepared in Example 1 (120 g) was dissolved in tetrahydrofuran (600 ml), and cooled to 0° C. Lithium chloride (33.3 g) was added, triethylamine (101 g) was then slowly added, and the resulting mixture was stirred for 30 min. Propionic acid anhydride (96.9 g) was slowly added over a 30 min. time period. The reaction mixture was slowly warmed to room temperature, and stirred for 1-1.5 hours. The reaction solution was cooled, 1N aqueous sodium chloride solution (300 ml) was added, and the mixture was stirred for 30 min. Ethyl acetate (300 ml) was added, the phases were separated, and extracted once again by ethyl acetate (300 ml). After washing with 1.5N hydrochloride solution (300 ml), the organic solution was washed once again with aqueous sodium chloride solution (240 ml). The ethyl acetate solution was distilled by vacuum to remove ethyl acetate until nothing come out. Heptanes was added to the resulting solution and stirred for 1 hours at 0-10° C., which was then filtered and dried to produce the white solid compound (2) (145.3 g, Yield 92%) 
       Example 3a 
     Preparation of (S)-3-((R)-2-(3-((R)-1-(t-butyldimethylsilyloxy)ethyl)-4-oxoazetidine-2-yl)propanoyl)-4-benzyloxazolidine-2-one-(10) 
       [0023]    Refer to  FIG. 4 , the compound (2) prepared in Example 2a or 2b (50.0 g) was dissolved in methane dichloride (140 ml), and cooled to 0° C. Titanium chloride (43.6 g) was added. After 1 hour diisopropylethylamine (42.4 g) and then Zinc bromide (24.1 g) in tetrahydrofuran (150 ml) was added at 0° C. Then 4-AA (50.0 g) was added. The resulting mixture was reacted for 2 hours at 5-15° C. Water (300 ml) was added to separate the phases. 1.5N hydrochloride acid (300 g) was added thereto. The phases were separated and washed with aqueous sodium bicarbonate solution once again, distilled to produce the title compound contaminated with some impurities (98 g). 
         [0024]      1 H NMR (300 MHz, CDCl 3 ) δ7.32 (m, 2H), 7.25 (m, 1H), 7.19 (d, 2H), 5.91 (s, 1H), 4.66-4.63 (m, 1H), 4.22-4.17 (m, 4H), 3.95 (m, 1H), 3.30 (dd, 1H), 3.06 (m, 1H), 2.68 (dd, 1H), 1.24-1.19 (m, 6H), 0.87 (s, 12H) 
       Example 3b 
     Preparation of (S)-3-((R)-2-(3-((R)-1-(t-butyldimethylsilyloxy)ethyl)-4-oxoazetidine-2-yl)propanoyl)-4-benzyloxazolidine-2-one-(10) 
       [0025]    Refer to  FIG. 4 , the compound (2) prepared in Example 2a or 2b (50.0 g) was dissolved in methane dichloride (140 ml), and cooled to 0° C. Titanium chloride (43.6 g) was added. After 30 minute diisopropylethylamine (42.4 g) was added at 0° C. Then 4-AA (50.0 g) was added. The resulting mixture was reacted for 4 hours at 15-20° C. Water (300 ml) was added to separate the phases. 1.5N hydrochloride acid (300 g) was added thereto. The phases were separated and washed with aqueous sodium bicarbonate solution once again, distilled to produce the title compound contaminated with some impurities (99 g). 
         [0026]      I H NMR (300 MHz, CDCl 3 ) δ7.32 (m, 2H), 7.25 (m, 1H), 7.19 (d, 2H), 5.91 (s, 1H), 4.66-4.63 (m, 1H), 4.22-4.17 (m, 4H), 3.95 (m, 1H), 3.30 (dd, 1H), 3.06 (m, 1H), 2.68 (dd, 1H), 1.24-1.19 (m, 6H), 0.87 (s, 12H) 
       Example 4a 
     Preparation of (3R,4S)-3-[[[R]-1′-t-butyldimethylsilyloxy]ethyl]-4-[(R)-1″-carboxyethyl]-2-azetidinone (1) 
       [0027]    Refer to  FIG. 5 , the compound (10) prepared in Example 3a (98 g) was dissolved in acetone (350 ml) and water (200 ml). Hydrogen peroxide (50 ml) was added thereto, and the mixture was stirred at 0° C. Sodium hydroxide (19 g) was dissolved in water (150 ml), which was then added, over a 30 min. time period. The reaction solution was stirred for 1 hours at 15-25° C., white solid, the compound (12), was precipitated out. After filtering, washing by water (20 ml) and drying the compound (12) was obtained that be reused to prepare compound (2) as example-2 (30.4 g with 98.5% purity, 82% yield calculated from compound (2). Water (500 ml) and methane dichloride (500 ml) were added into resulting filtrate, and the phases were separated. The organic phase was distilled to produce the compound of formula (2) (20 g). The aqueous phase was adjusted to pH 3.5 using 6N hydrochloric acid to produce a crystal. This crystal was filtered to produce the title compound. Then wet cake product was washed with the mixing solvent of methane dichloride and heptanes (50 ml) at −5 to 5° C. After drying at more than 40° C. having ratio of &gt;99.9/0.1 with 38.0 g. (Yield 72% that was calculated from the 4-AA compound; purity 99.0% and assay 99.5% by HPLC). 
         [0028]    IH NMR (300 MHz, CDCl3) δ6.5 (br s, IH), 4.3 (m, IH), 3.97 (dd, IH), 3.05 (ddm, IH), 2.85 (m, IH), 1.29 (d, 3H), 1.22 (d, 3H), 0.89 (s, 9H), 0.08 (s, 6H) [the corresponding-isomer to 4-BMA] 
         [0029]    IH NMR (300 MHz, CDCl3) δ6.5 (br s, 1H), 4.2 (m, IH), 3.72 (dd, IH), 2.85 (ddm, IH), 2.65 (m, IH), 1.3 (d, 3H), 1.23 (d, 3H), 0.90 (s, 9H), 0.08 (s, 6H) 
       Example 4b 
     Preparation of (3R,4S)-3-[[[R]-1′-t-butyldimethylsilyloxy]ethyl]-4-[(R)—I″-carboxyethyl]-2-azetidinone (1) 
       [0030]    Refer to  FIG. 6 , the compound (10) prepared in Example 3a (98 g) was dissolved in acetone (350 ml) and water (200 ml). Hydrogen peroxide (50 ml) was added thereto, and the mixture was stirred at 0° C. Sodium hydroxide (19 g) was dissolved in water (150 ml), which was then added, over a 30 min. time period. The reaction solution was stirred for 1 hour at 15-25° C., white solid, the compound (12), was precipitated out. After filtering, washing by water (20 ml) and drying the compound (12) was obtained that be reused to prepare compound (2) as example-2 (30.4 g with 98.5% purity, 82% yield calculated from compound (2). Water (500 ml) and methane dichloride (500 ml) were added into resulting filtrate, and the phases were separated. The organic phase was distilled to produce the compound of formula (2) (20 g). The aqueous phase was adjusted to pH 3.5 using 6N hydrochloric acid to produce a crystal. This crystal was filtered to produce the title compound. Then wet cake product was washed with the mixing solvent of methane dichloride and heptanes (50 ml) at −5 to 5° C. After drying at more than 40° C. having ratio of &gt;99.9/0.1 with 38.0 g. (Yield 72% that was calculated from the 4-AA compound; purity 99.0% and assay 99.5% by HPLC). 
         [0031]    The present invention has been explained by referring to the mode and the embodiments. However, the present invention is not limited to this mode and these embodiments, and can be modified or altered within the scope of the common knowledge of one having ordinary skill in the art.