A method for synthesizing imipenem drug intermediate 4-AA

Abstract

This invention belongs to the field of pharmaceutical chemical synthesis technology, specifically relating to a method for synthesizing the penem intermediate 4-AA. Using bromonitromethane as a raw material, it reacts with methyl acetoacetate and sodium methoxide to generate methyl 2-nitromethyl-3-oxobutyrate. After enzymatic reduction, methyl 2-nitromethyl-3-oxobutyrate reacts with tert-butyldimethylchlorosilane, followed by hydrogenation reduction to obtain methyl (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate. This methyl ester undergoes a ring-closure reaction and is then catalytically oxidized with oxyacetic acid to obtain the penem intermediate 4-AA. This invention directly cyclizes the amino compound obtained from nitro reduction to obtain a β-lactam four-membered ring compound, eliminating the need for amino protection and deprotection. The operation is simple and more suitable for industrial production, and the yield of the penem intermediate 4-AA reaches over 95.5%, with a purity of over 99.6%.

Description

Technical Field

[0001] This invention belongs to the field of pharmaceutical chemical synthesis technology, specifically relating to a method for synthesizing 4-AA, an intermediate in penem drugs. Background Technology

[0002] (3R,4R)-4-acetoxy-3-[(R)-tert-butyldimethoxy)ethyl]-2-azacyclobutanone, also known as 4-acetoxyazacyclobutanone or simply 4-AA, is a key intermediate in the synthesis of penem drugs and has important applications in the pharmaceutical industry. The 4-AA structure contains three chiral centers and one lactam ring, which constitutes both the focus and the challenge in its synthesis. Early synthetic work began with the selection of suitable and inexpensive chiral sources from natural products for stereocontrolled synthesis. Later, to meet the needs of large-scale production, semi-synthetic studies using penicillin and cephalosporins as raw materials were conducted. In recent years, with the gradual expansion of the penem drug market share, the market demand for 4-AA is growing significantly.

[0003] The asymmetric catalytic hydrogenation reaction of Noyori in Japan uses methyl acetoacetate as a starting material. After the methyl acetoacetate undergoes the Mannich reaction, a single product is obtained under the action of a chiral catalyst. Following hydrolysis, the product is cyclized in the presence of triphenylphosphine and dithiopyridine, then protected with a hydroxyl group. Finally, an acetoxy group is introduced at the C4 position under the catalysis of peracetic acid and ruthenium trichloride to obtain 4-AA, as shown in the route below. The process for synthesizing 4-AA from ethyl acetoacetate has the advantages of high yield and good stereoselectivity, and has already been industrialized in Japan. However, the chiral catalyst used in this method (such as R-BRNAP-Ru) is expensive, the reaction conditions are harsh, and industrial implementation is difficult; furthermore, the cost of the hydrolyzed starting materials triphenylphosphine and dithiopyridine is high, and the post-processing is complex.

[0004]

[0005] Chinese patent CN113173947A discloses a method for preparing 4-AA, comprising the following steps: S1, preparing a first intermediate using benzamide and formaldehyde aqueous solution; S2, preparing a second intermediate using the first intermediate, thionyl chloride, toluene, and n-heptane; S3, preparing a third intermediate using the second intermediate, methyl acetoacetate, sodium methoxide, toluene, dilute hydrochloric acid, and isopropanol; S4, preparing a fourth intermediate using the third intermediate, reductase, ethyl acetate, saturated sodium bicarbonate, and saturated brine; S5, preparing a fifth intermediate using the fourth intermediate, imidazole, TBSCL, and toluene; S6, preparing a sixth intermediate using the fifth intermediate, ethanolamine, methanol, and n-heptane; S7, preparing a seventh intermediate using the sixth intermediate, Grignard reagent, and n-heptane; S8, obtaining 4-AA using the seventh intermediate, ruthenium trichloride, potassium acetate, ethyl acetate, acetic acid, and peracetic acid solution, the reaction process of which is shown below. In this patent, the preparation of the third intermediate uses the second intermediate and methyl acetoacetate as raw materials. The second intermediate employs a benzoyl group to protect the amino group, but this protecting group needs to be removed during the preparation of the sixth intermediate. This not only increases the number of reaction steps but also complicates the operation. Furthermore, the post-processing of the seventh intermediate requires multiple concentrations and crystallizations to achieve the desired product yield and quality. This is because after the fourth intermediate is fed in, the fifth and sixth intermediates are not discharged, resulting in fewer impurity outlets and making product crystallization difficult.

[0006]

[0007] Chinese patent CN108069998A discloses a method for synthesizing a penem drug intermediate, using (R)-3-hydroxybutyrate as a raw material to prepare the penem drug intermediate 4-AA, and the reaction process is shown below. This patent still uses an expensive chiral ruthenium catalyst in the asymmetric hydrogenation reduction, and the product's ee value is less than 97%, severely affecting the optical purity of the target product 4-AA. Furthermore, the final step of the process uses ozone oxidation, which is highly hazardous and restricts the industrial implementation of this route.

[0008]

[0009] Therefore, there is an urgent need to develop a simple, low-cost, high-yield, and high-purity method for synthesizing 4-AA, a penem drug intermediate. Summary of the Invention

[0010] The purpose of this invention is to provide a method for synthesizing penem drug intermediate 4-AA, which directly cyclizes the amino compound obtained by nitro reduction to obtain a β-lactam four-membered ring compound without the need for further protection and deprotection of the amino group. The method is short, simple, and low in cost, making it more suitable for industrial production. Furthermore, the penem drug intermediate 4-AA obtained by this invention has high yield and high purity.

[0011] The technical solution adopted by this invention to solve its technical problem is: a method for synthesizing 4-AA, an intermediate in penem drugs, comprising the following steps:

[0012] (1) Using bromonitromethane as a raw material, methyl acetoacetate and sodium methoxide are added to react and methyl 2-nitromethyl-3-oxobutyrate is obtained;

[0013] (2) Methyl 2-nitromethyl-3-oxobutyrate is first reduced by carbonyl reductase to give methyl (2S,3R)-2-nitromethyl-3-hydroxybutyrate; methyl (2S,3R)-2-nitromethyl-3-hydroxybutyrate reacts with tert-butyldimethylchlorosilane to give methyl (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate.

[0014] (3) Methyl (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate was subjected to hydrogenation reduction to obtain methyl (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate.

[0015] (4) Methyl (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate undergoes a cyclization reaction to give (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone; (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone is then reacted with peracetic acid to give penem intermediate 4-AA.

[0016] Specifically, in step (1), the molar ratio of bromonitromethane to methyl acetoacetate is 1:1.05 to 1.15, the molar ratio of methyl acetoacetate to sodium methoxide is 1:1 to 1.05, the reaction temperature is -5 to 5℃, and the reaction time is 2 to 4 hours.

[0017] In step (2), the mass ratio of methyl 2-nitromethyl-3-oxobutyrate to carbonyl reductase is 1:0.21-0.24, and the NCBI accession number of carbonyl reductase is CDZ96865.1; the enzyme reduction reaction temperature is 30-40℃, and the enzyme reduction reaction time is 15-25 hours; (2S,3R)-2-nitromethyl-3-hydroxybutyrate methyl ester and tert-butyldimethylchlorosilane are reacted at 90-110℃ for 4-6 hours.

[0018] The carbonyl reductase is the reductase with NCBI accession number CDZ96865.1 or its homolog. In this invention, "homolog" refers to an enzyme whose amino acid sequence has a similarity of >70% to the amino acid sequence of the carbonyl reductase disclosed in this invention.

[0019] The amino acid sequence of the carbonyl reductase is as follows:

[0020] MSDTTVYLVTGANRGIGLSIVKALASNPANVIFAGARTPAKATALHELAKSSQAKINVIGLVSADTESNHKAAEEIKKAAGRVDVIIANAGVGAPEAAQFVHESDPAQWTAHYEVNVVGPVVLYKEFYS LLRASKVAAKFIVVSSIAGSLELAPQFDKPFGIYSTSKAAVNYATVKIHLESKDFGLIAFPLHPGTVKTDMFDAVVKKLFPDGKENPFANQTISLEESAEAILKVVNEATRESHGGKFLSYDGSNLPY.

[0021] In step (3), the hydrogenation reduction reaction temperature is 30-50℃, the hydrogenation reduction reaction time is 3-6 hours, and the hydrogenation reduction reaction pressure is 0.1-5MPa.

[0022] In step (4), the ring-closing reaction temperature is -5 to 10°C and the ring-closing reaction time is 2 to 5 hours.

[0023] Further, the specific operation of step (1) is as follows: toluene, methyl acetoacetate, and sodium methoxide in methanol are mixed, and a mixture of bromonitromethane and toluene is added to react. After the reaction is completed, the pH value is adjusted, the organic phase is separated, and the mixture is concentrated under reduced pressure to obtain methyl 2-nitromethyl-3-oxobutyrate; the reaction formula is as follows:

[0024] ;

[0025] The ratio of toluene to methyl acetoacetate is 4.5–6.5:1, with toluene measured in ml and methyl acetoacetate in g; the concentration of sodium methoxide in the methanol solution is 27–30 wt%; in the mixture of bromonitromethane and toluene, the ratio of bromonitromethane to toluene is 1:4–5, with bromonitromethane measured in g and toluene in ml; the pH is adjusted to ≤5.0 using hydrochloric acid solution, with a concentration of 30–35 wt%.

[0026] Further, the specific operation of the enzyme reduction reaction in step (2) is as follows: methyl 2-nitromethyl-3-oxobutyrate is dissolved in phosphate buffer, and carbonyl reductase solution, glucose dehydrogenase, glucose and coenzyme NADP are added. + The pH was initially adjusted to initiate the enzyme reduction reaction. The pH was then adjusted again, and the mixture was filtered. The filter cake was extracted, washed, and the resulting organic phase was distilled, crystallized, filtered, and dried to obtain methyl (2S,3R)-2-nitromethyl-3-hydroxybutyrate. The reaction formula is as follows:

[0027] ;

[0028] The composition of the phosphate buffer is as follows: methyl 2-nitromethyl-3-oxobutyrate is in a mass ratio of 1:4 to 5.2; the pH of the phosphate buffer is 7.0 to 7.5, and the phosphate buffer is an aqueous solution of potassium dihydrogen phosphate, with a mass ratio of potassium dihydrogen phosphate to water of 1:75 to 76; the molar ratio of glucose to methyl 2-nitromethyl-3-oxobutyrate is 1.01 to 1.08:1; and the phosphate buffer also contains methyl 2-nitromethyl-3-oxobutyrate, glucose dehydrogenase, and NADP coenzyme. + The mass ratio is 1:2–3.5:0.0006–0.001; the enzyme content in the carbonyl reductase solution is 10–12 wt%.

[0029] The pH value was initially adjusted to 7.65–7.85 using sodium hydroxide solution, and then adjusted again to 4.0–4.5 using citric acid solution; the concentration of sodium hydroxide solution was 8–12 wt%, and the concentration of citric acid solution was 28–32 wt%; the crystallization temperature was 0–10℃, the crystallization time was 1–3 hours, the drying temperature was 40–60℃, and the drying time was 4–8 hours.

[0030] Further, the specific operation of the reaction between (2S,3R)-2-nitromethyl-3-hydroxybutyrate methyl ester and tert-butyldimethylchlorosilane in step (2) is as follows: an acid-binding agent is added to (2S,3R)-2-nitromethyl-3-hydroxybutyrate methyl ester, the temperature is raised to 80-90°C, a mixed solution of tert-butyldimethylchlorosilane and toluene is added, and the temperature is further raised to 90-110°C under nitrogen protection for reaction. The mixture is then cooled, washed, and the solvent is removed by vacuum distillation to obtain (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate methyl ester; its reaction formula is as follows:

[0031] ;

[0032] The molar ratio of (2S,3R)-2-nitromethyl-3-hydroxybutyrate, tert-butyldimethylchlorosilane, and acid-binding agent is 1:1.06-1.10:1.06-1.15, and the acid-binding agent is imidazole; the ratio of tert-butyldimethylchlorosilane to toluene is 1:2.1-2.2, where tert-butyldimethylchlorosilane is expressed in g and toluene in ml.

[0033] Further, the specific operation of the hydrogenation reduction reaction in step (3) is as follows: methyl (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate, catalyst, and ethyl acetate are mixed, and then hydrogen gas is introduced to carry out the hydrogenation reduction reaction. After filtration, methyl (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate is obtained; its reaction formula is as follows:

[0034] ;

[0035] Wherein: the molar ratio of (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate to hydrogen is 1:9 to 11; the amount of catalyst is 2 to 4% of the mass of (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate, and the catalyst is 5% Pd / C; the ratio of ethyl acetate to (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate is 5 to 7:1, ethyl acetate is in ml, and (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate is in g.

[0036] Further, the specific operation of the ring-closing reaction in step (4) is as follows: Grignard reagent is mixed with n-heptane, and methyl (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate is added to react. After the reaction is completed, acetic acid is added to adjust the pH value, water is added and allowed to stand, and the layers are separated to obtain an organic phase. The organic phase is concentrated, crystallized, filtered and dried to obtain (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone; its reaction formula is as follows:

[0037] ;

[0038] The molar ratio of (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate methyl ester to Grignard reagent is 1:2.5-3.5, wherein the Grignard reagent is tert-butylmagnesium chloride; the molar ratio of (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate methyl ester to n-heptane is 1:3-4, wherein (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate methyl ester is expressed in g, and n-heptane in ml; the pH is adjusted to 6.5-7, the crystallization temperature is 0-10℃, and the crystallization time is 0.5-2.0 hours. Preferably, a tetrahydrofuran solution of Grignard reagent (where the concentration of Grignard reagent is 2.0 mol / L) is mixed with n-heptane.

[0039] Further, the specific operation of the reaction between (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone and peracetic acid in step (4) is as follows: Under nitrogen protection, acetic acid, potassium acetate, ethyl acetate, and (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone are mixed, a catalyst and peracetic acid solution are added to carry out the reaction, quench, concentrate, filter, wash, and dry to obtain penem drug intermediate 4-AA; its reaction formula is as follows:

[0040] ;

[0041] Wherein: the molar ratio of (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone to peracetic acid is 1:6-7, and the concentration of the peracetic acid solution is 15-20wt%; the ratio of potassium acetate, acetic acid, ethyl acetate to (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone is 0.3-0.5:2-4:8-12:1, and the amounts of potassium acetate, acetic acid, and (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone are in g, and the amount of ethyl acetate is in ml;

[0042] The molar ratio of (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone and catalyst is 1:0.0005-0.001, and the catalyst is ruthenium trichloride; the reaction temperature is -10 to 0℃, the reaction time is 1 to 3 hours; the drying temperature is 40 to 60℃, and the drying time is 4 to 8 hours.

[0043] The present invention has the following beneficial effects:

[0044] (1) In the prior art, the synthesis of the intermediate 4-AA of penem drugs mainly uses benzamide as the starting material. It first undergoes a hydroxymethylation reaction with formaldehyde, and then a chlorination reaction to generate an intermediate that can be condensed with methyl acetoacetate to obtain an intermediate with an amino protecting group. The other raw material used in this process, formaldehyde aqueous solution, is not only difficult to treat in terms of environmental protection, but also inevitably causes harm to the operators during operation. The control of the chlorination reaction involved is relatively strict. In addition, the obtained intermediate with an amino protecting group needs to be removed in subsequent steps, which increases the reaction steps and makes the operation complicated. Compared with existing technologies, this invention uses bromonitromethane as a raw material, reacting it with methyl acetoacetate and sodium methoxide to obtain methyl 2-nitromethyl-3-oxobutyrate, avoiding the safety hazards caused by formaldehyde aqueous solution and chlorination reaction, thus greatly improving the safety of the process. After enzymatic reduction, methyl 2-nitromethyl-3-oxobutyrate reacts with tert-butyldimethylchlorosilane to obtain methyl (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate. Methyl (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate is then hydrogenated and directly cyclized to obtain a β-lactam four-membered ring compound, eliminating the need for amino protection and deprotection, simplifying the operation, and saving production costs.

[0045] Furthermore, the enzyme selected in this invention is a carbonyl reductase with NCBI accession number CDZ96865.1, which has three major advantages compared to traditional enzymes: ① The enzyme in this invention can achieve good reaction results using only water as the reaction medium, achieving good reaction rate and product purity while being environmentally friendly; ② The purity of the product is controlled to be as high as 98% during the enzyme reaction of this invention, which not only ensures product quality but also improves product yield; ③ The enzyme in this invention can withstand reaction temperatures of 30-40℃, which is more conducive to industrial production and storage while improving the reaction rate.

[0046] (2) In the prior art, the synthesis of penem drug intermediate 4-AA requires three steps: reaction with tert-butyldimethylchlorosilane, deprotection, and cyclization to obtain the cyclized intermediate. Moreover, the melting point of the cyclized intermediate is low, and problems such as difficulty in crystallization and centrifugation often occur, which brings considerable trouble to industrial production. At the same time, the yield and quality of the product cannot be guaranteed.

[0047] In this invention, (2S,3R)-2-nitromethyl-3-hydroxybutyrate methyl ester is first reacted with tert-butyldimethylchlorosilane to obtain (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate methyl ester. The (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate methyl ester is then hydrogenated and reduced to obtain (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate methyl ester. This methyl ester undergoes a cyclization reaction to yield the cyclization intermediate (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone. This shortens the reaction steps, achieves a yield of over 91% for the cyclization intermediate, and ensures that the purity of the (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone is over 99.0%. The synthesis of the high-quality cyclic intermediate (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone not only reduced the amount of ruthenium trichloride catalyst used from 2-3‰ to ≤1‰, thus lowering production costs, but also further improved the purity and yield of the penem drug intermediate 4-AA. The single-step yield of the product increased from 85% to over 95%, meeting market demand.

[0048] In summary, the method of the present invention significantly improves the yield and purity of the penem drug intermediate 4-AA, with a yield of over 95.5% and a purity of over 99.6%, shortens the synthesis steps of the target compound, and features simple operation, low cost, and reliable safety, making it more suitable for industrial production. Attached Figure Description

[0049] Figure 1 This is an HPLC chromatogram of methyl 2-nitromethyl-3-oxobutyrate prepared in Example 1 of this invention.

[0050] Figure 2 This is an HPLC chromatogram of methyl (2S,3R)-2-nitromethyl-3-hydroxybutyrate prepared in Example 1 of this invention.

[0051] Figure 3 This is the HPLC chromatogram of (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone prepared in Example 1 of this invention.

[0052] Figure 4 This is an HPLC chromatogram of 4-AA, a penem drug intermediate prepared in Example 1 of this invention.

[0053] Figure 5 This is the infrared spectrum of 4-AA, a penem drug intermediate prepared in Example 1 of this invention. Detailed Implementation

[0054] The following are specific embodiments of the present invention, which further describe the technical solution of the present invention. However, the scope of protection of the present invention is not limited to these embodiments. All changes or equivalent substitutions that do not depart from the concept of the present invention are included within the scope of protection of the present invention.

[0055] The glucose dehydrogenase and NADP used in the embodiments of the present invention + Purchased from McLean Biotech Co., Ltd.

[0056] The carbonyl reductase used in this invention was obtained through gene mining, screening the target gene of the reductase from the NCBI database, ligating it into the expression vector pET-28a, transforming it into the *E. coli* expression host, and inducing protein expression. *E. coli* was introduced into a fermentation medium for amplification culture, centrifuged to obtain resting cells, which were then suspended in a buffer solution and homogenized using a high-pressure homogenizer to obtain the reductase solution. The reductase content (%) in the reductase solution was calculated as: (resting cell weight / buffer weight) × 100%.

[0057] The carbonyl reductase described in this invention is derived from Lentilactobacillus kefiri.

[0058] Example 1

[0059] The method for synthesizing penem intermediate 4-AA includes the following steps:

[0060] (1) Under nitrogen protection, 600 ml of toluene and 107 g (0.921 mol) of methyl acetoacetate were mixed at 0-5 °C and stirred for 10 min. Then, 174.8 g of a methanol solution of sodium methoxide (0.922 mol) (sodium methoxide concentration was 28.5 wt%) was added dropwise, and the mixture was kept at 0-5 °C for 2 hours. A mixture of bromonitromethane and toluene (117 g (0.836 mol) of bromonitromethane and 500 ml of toluene) was added, and the mixture was reacted at -5 to -2 °C for 4 hours. After the reaction was completed, the pH value was adjusted to ≤5.0 with 30 wt% hydrochloric acid solution, and the organic phase was separated. The organic phase was concentrated under reduced pressure until no liquid distilled off, yielding 160 g of methyl 2-nitromethyl-3-oxobutyrate in an oily form, of which the content of methyl 2-nitromethyl-3-oxobutyrate was 85% (external standard method), the yield was 92.9%, and the purity was 93.87%. Its HPLC chromatogram is shown below. Figure 1 As shown.

[0061] (2) The above-mentioned oily methyl 2-nitromethyl-3-oxobutyrate was mixed with 544g of phosphate buffer (pH 7.0, 7.07g potassium dihydrogen phosphate + 536.93g purified water), 297.7g of carbonyl reductase solution (enzyme content 10wt%), 150g of glucose (0.833mol), and coenzyme NADP. +0.09 g of glucose dehydrogenase and 408 g of methyl methacrylate were mixed. The pH was initially adjusted to 7.75 with 10 wt% sodium hydroxide solution, and the enzyme reduction reaction was carried out at 35 °C for 20 hours. The pH was then adjusted again to 4.3 with 30 wt% citric acid solution, and the mixture was filtered. The filter cake was washed three times with 500 ml, 500 ml, and 300 ml of ethyl acetate extract at 50 °C, and washed once with 191.9 g of saturated sodium chloride-sodium bicarbonate solution. After distilling off ethyl acetate from the obtained organic phase, the remaining reaction solution was crystallized at 0–3 °C for 3 hours, filtered, and the filter cake was dried at 50 °C for 6 hours to obtain 116 g of methyl (2S,3R)-2-nitromethyl-3-hydroxybutyrate, with a yield of 83.5% and a purity of 99.06%. Its HPLC chromatogram is shown below. Figure 2 As shown.

[0062] (3) Add 47.8g of imidazole to the above (2S,3R)-2-nitromethyl-3-hydroxybutyrate methyl ester, heat to 85℃, add a mixed solution of tert-butyldimethylchlorosilane and toluene (103.8g of tert-butyldimethylchlorosilane and 222mL of toluene), react at 100℃ for 5 hours under nitrogen protection, and when the raw material is controlled to be ≤2.0% in the liquid phase detection, slowly lower the system temperature to below 45℃, wash with water, and remove the solvent from the organic phase under reduced pressure to obtain 183.3g of (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate methyl ester with a purity of 99.14%.

[0063] (4) Mix the above-mentioned (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate methyl ester, 5.48 g of 5% Pd / C catalyst, and 932 ml of ethyl acetate. Replace the air with nitrogen three times, and then replace the nitrogen with hydrogen three times. Then introduce 12.6 g of hydrogen to carry out the hydrogenation reduction reaction for 4.5 hours, control the reaction temperature at 40℃ and the reaction pressure at 3.0 MPa, filter, and obtain 159.7 g of (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate methyl ester with a purity of 99.21%.

[0064] (5) 908.8 mL of tetrahydrofuran solution of tert-butyl magnesium chloride (with a concentration of 2.0 mol / L of tert-butyl magnesium chloride) was mixed with 554.4 mL of n-heptane. The above-mentioned (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate methyl ester was added dropwise to the reaction system at -5 to 0 °C for 5 hours. After the reaction was completed, the temperature was raised to 12 °C, acetic acid was added to adjust the pH to 6.5, water was added and allowed to stand, and the organic phase was separated into layers. The organic phase was concentrated and crystallized at 0 to 3 °C for 2 hours. After filtration, it was dried under reduced pressure at 40 °C for 8 hours to obtain 136.5 g of (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone, with a yield of 97.5% and a purity of 99.32%. The NMR data of (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone were as follows: 1 HNMR (400MHz, CDCl3), δ H =5.67(m, 1H, NH), 4.22(m, 1H), 3.36-3.29(m, 2H, 2-H), 3.25(m, 1H, 3-H), 1.20(d, 3H), 0.88(s, 9H), 0.08(s, 6H), its HPLC chromatogram is as follows Figure 3 As shown.

[0065] During steps (3), (4), and (5), the overall yield of (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone was 91.11%.

[0066] (6) Under nitrogen protection, 406.0 g of acetic acid, 53.6 g of potassium acetate, 1345.0 mL of ethyl acetate, and the above (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone were mixed and cooled to -6 to -3 °C. 0.127 g of ruthenium trichloride was added with stirring. 1517.36 g of peracetic acid solution (concentration 19 wt%) was slowly added dropwise to the reaction system. The system temperature was maintained at -6 to -3 °C for 2 hours. Saturated NaHSO3 aqueous solution was added to quench the reaction, and the reaction system was directly concentrated at 45 °C. The reaction solution was filtered, the filter cake was washed, and dried at 50 °C for 6 hours to obtain 162.7 g of penem intermediate 4-AA, with a yield of 95.6% and a purity of 99.798%. NMR data of penem intermediate 4-AA: 1 HNMR (400MHz, CDCl3), δ H =5.84(m,1H,NH),6.48(d,1H,2-H),4.22(m,1H),3.19(dd,1H,3-H),2.11(d,3H),0.88(s,9H),0.08(s,6H).

[0067] The HPLC chromatogram of 4-AA, an intermediate in penem drugs, is shown below. Figure 4 As shown, the infrared spectrum is as follows Figure 5 As shown.

[0068] Example 2

[0069] The method for synthesizing penem intermediate 4-AA includes the following steps:

[0070] (1) Under nitrogen protection, 500 ml of toluene and 107 g (0.921 mol) of methyl acetoacetate were mixed at 0-3℃ and stirred for 10 min. Then, 174.2 g of a methanol solution of sodium methoxide (0.967 mol) (sodium methoxide concentration was 30 wt%) was added dropwise and the mixture was kept at 0-3℃ for 2 hours. A mixture of bromonitromethane and toluene (121.0 g (0.865 mol) of bromonitromethane and 491 ml of toluene) was added and the mixture was reacted at -3-2℃ for 3 hours. After the reaction was completed, the pH value was adjusted to ≤5.0 with 35 wt% hydrochloric acid solution and the organic phase was separated. The organic phase was concentrated under reduced pressure until no liquid distilled off, and 158.8 g of methyl 2-nitromethyl-3-oxobutyrate was obtained as an oily substance. The content of methyl 2-nitromethyl-3-oxobutyrate was 88% (external standard method), the yield was 92.3%, and the purity was 95.13%.

[0071] (2) The above-mentioned oily methyl 2-nitromethyl-3-oxobutyrate was mixed with 720.5g of phosphate buffer (pH 7.5, consisting of 9.48g potassium dihydrogen phosphate and 711.02g purified water), 296.7g of carbonyl reductase solution (enzyme content 11wt%), 148.3g of glucose (0.823mol), and coenzyme NADP. + 0.12 g of glucose dehydrogenase and 280 g of methyl methacrylate were mixed, and the pH was initially adjusted to 7.85 with 8 wt% sodium hydroxide solution. The enzyme reduction reaction was carried out at 30 °C for 25 hours. The pH was then adjusted again to 4.5 with 28 wt% citric acid solution. The mixture was filtered. The filter cake was washed three times with 500 ml, 500 ml, and 300 ml of ethyl acetate extract at 50 °C with stirring. It was washed once with 191.9 g of saturated sodium chloride-sodium bicarbonate solution. After distilling off ethyl acetate from the obtained organic phase, the remaining reaction solution was crystallized at 3-6 °C for 2 hours. The mixture was filtered, and the filter cake was dried at 40 °C for 8 hours to obtain 123.4 g of methyl (2S,3R)-2-nitromethyl-3-hydroxybutyrate, with a yield of 86.7% and a purity of 99.30%.

[0072] (3) Add 54.2 g of imidazole to the above (2S,3R)-2-nitromethyl-3-hydroxybutyrate methyl ester, heat to 80 °C, add a mixed solution of tert-butyldimethylchlorosilane and toluene (111.2 g of tert-butyldimethylchlorosilane and 233.6 mL of toluene), react at 90 °C for 6 hours under nitrogen protection, and when the raw material is controlled to be ≤2.0% in the liquid phase detection, slowly lower the system temperature to below 45 °C, wash with water, and remove the solvent from the organic phase under reduced pressure to obtain 194.5 g of (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate methyl ester with a purity of 99.44%.

[0073] (4) Mix the above-mentioned (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate methyl ester, 4.16 g of 5% Pd / C catalyst, and 1156 ml of ethyl acetate. Replace the air with nitrogen three times, and then replace the nitrogen with hydrogen three times. Then introduce 12.43 g of hydrogen to carry out the hydrogenation reduction reaction for 6 hours, controlling the reaction temperature at 30℃ and the reaction pressure at 5 MPa. After filtration, 167.5 g of (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate methyl ester with a purity of 99.35% was obtained.

[0074] (5) Mix 1113.8 ml of tetrahydrofuran solution of tert-butyl magnesium chloride (with a concentration of 2.0 mol / L of tert-butyl magnesium chloride) with 529.2 ml of n-heptane. Add the above-mentioned (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate methyl ester dropwise to the reaction system at 0-5℃ and react for 3.5 hours. After the reaction is completed, raise the temperature to 10℃, add acetic acid to adjust the pH value to 7, add water and let stand. The organic phase is separated into layers. The organic phase is concentrated and crystallized at 4-7℃ for 1.0 hour. After filtration, dry under reduced pressure at 35℃ for 8 hours to obtain 145.0 g of (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone, with a yield of 98.7% and a purity of 99.35%.

[0075] During steps (3), (4), and (5), the overall yield of (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone was 90.75%.

[0076] (6) Under nitrogen protection, 296.0 g of acetic acid, 44.4 g of potassium acetate, 1184.0 mL of ethyl acetate and the above (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone were mixed and cooled to -10 to -6 °C. 0.118 g of ruthenium trichloride was added with stirring. 1960.8 g of peracetic acid solution (concentration of 15 wt%) was slowly added dropwise to the reaction system. The system temperature was maintained at -10 to -6 °C for 3 hours. Saturated NaHSO3 aqueous solution was added to quench the reaction and the reaction system was directly concentrated at 50 °C. The reaction solution was filtered, the filter cake was washed, and dried at 40 °C for 8 hours to obtain 4-AA173.4 g of penem drug intermediate, with a yield of 95.8% and a purity of 99.761%.

[0077] Example 3

[0078] The method for synthesizing penem intermediate 4-AA includes the following steps:

[0079] (1) Under nitrogen protection, 690 ml of toluene and 107 g (0.921 mol) of methyl acetoacetate were mixed at 3-5 °C and stirred for 10 min. Then, 189.7 g of a methanol solution of sodium methoxide (0.948 mol) (sodium methoxide concentration was 27.0 wt%) was added dropwise and the mixture was kept at 3-5 °C for 2 hours. A mixture of bromonitromethane and toluene (112.1 g (0.801 mol) of bromonitromethane and 561 ml of toluene) was added and the mixture was kept at -2-5 °C for 2 hours. After the reaction was completed, the pH value was adjusted to ≤5.0 with 33 wt% hydrochloric acid solution and the organic phase was separated. The organic phase was concentrated under reduced pressure until no liquid distilled off, and 147.4 g of methyl 2-nitromethyl-3-oxobutyrate was obtained as an oily substance. The content of methyl 2-nitromethyl-3-oxobutyrate was 89% (external standard method), the yield was 93.5%, and the purity was 95.22%.

[0080] (2) The above-mentioned oily methyl 2-nitromethyl-3-oxobutyrate was mixed with 591.7g of phosphate buffer (pH 7.0, consisting of 7.73g potassium dihydrogen phosphate and 583.97g purified water), 252.3g of carbonyl reductase solution (enzyme content 12wt%), 138.5g of glucose (0.769mol), and coenzyme NADP. +0.14 g of glucose dehydrogenase and 458.8 g of methyl glucose dehydrogenase were mixed, and the pH was initially adjusted to 7.65 with 12 wt% sodium hydroxide solution. The enzyme reduction reaction was carried out at 40 °C for 15 hours. The pH was then adjusted again to 4.0 with 32 wt% citric acid solution, and the mixture was filtered. The filter cake was washed three times with 500 ml, 500 ml, and 300 ml of ethyl acetate extract at 50 °C, and washed once with 191.9 g of saturated sodium chloride-sodium bicarbonate solution. After distilling off ethyl acetate from the obtained organic phase, the remaining reaction solution was crystallized at 7–10 °C for 1 hour. The mixture was filtered, and the filter cake was dried at 60 °C for 4 hours to obtain 119.6 g of methyl (2S,3R)-2-nitromethyl-3-hydroxybutyrate, with a yield of 89.4% and a purity of 99.20%.

[0081] (3) Add 50.1 g of imidazole to the above (2S,3R)-2-nitromethyl-3-hydroxybutyrate methyl ester, heat to 90 °C, add a mixed solution of tert-butyldimethylchlorosilane and toluene (110.2 g of tert-butyldimethylchlorosilane and 242.4 mL of toluene), react at 110 °C for 4 hours under nitrogen protection, and when the raw material is controlled to be ≤2.0% in the liquid phase detection, slowly lower the system temperature to below 45 °C, wash with water, and remove the solvent from the organic phase under reduced pressure to obtain 189.9 g of (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate methyl ester with a purity of 99.27%;

[0082] (4) Mix the above-mentioned (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate methyl ester, 7.53 g of 5% Pd / C catalyst, and 1283 ml of ethyl acetate. Replace the air with nitrogen three times, and then replace the nitrogen with hydrogen three times. Then introduce 14.1 g of hydrogen to carry out the hydrogenation reduction reaction for 3 hours, controlling the reaction temperature at 50℃ and the reaction pressure at 0.1 MPa. Filter to obtain 165.5 g of (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate methyl ester with a purity of 99.41%.

[0083] (5) 786.5 mL of tetrahydrofuran solution of tert-butyl magnesium chloride (with a concentration of 2.0 mol / L of tert-butyl magnesium chloride) was mixed with 641.6 mL of n-heptane. The above-mentioned (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate methyl ester was added dropwise to the reaction system at 5-10 °C and reacted for 2 hours. After the reaction was completed, the temperature was raised to 15 °C, acetic acid was added to adjust the pH value to 6.8, water was added and allowed to stand, and the organic phase was obtained by separation. The organic phase was concentrated and crystallized at 6-10 °C for 0.5 hours. After filtration, it was dried under reduced pressure at 40 °C for 8 hours to obtain 141.1 g of (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone, with a yield of 97.3% and a purity of 99.50%.

[0084] During steps (3), (4), and (5), the overall yield of (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone was 91.38%.

[0085] (6) Under nitrogen protection, 544.8 g of acetic acid, 68.1 g of potassium acetate, 1634.4 mL of ethyl acetate and the above (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone were mixed and cooled to -4 to 0 °C. 0.136 g of ruthenium trichloride was added with stirring. 1580.0 g of peracetic acid solution (concentration of 20 wt%) was slowly added dropwise to the reaction system. The system temperature was maintained at -4 to 0 °C for 1 hour. Saturated NaHSO3 aqueous solution was added to quench the reaction and the reaction system was directly concentrated at 40 °C. The reaction solution was filtered, the filter cake was washed, and dried at 60 °C for 4 hours to obtain 4-AA169.4 g of penem drug intermediate, with a yield of 96.0% and a purity of 99.688%.

[0086] The penem intermediate 4-AA of the present invention was determined according to the relevant methods in Part IV of the 2015 edition of the Pharmacopoeia of the People's Republic of China. The performance data of the penem intermediate 4-AA of the present invention are shown in Table 1.

[0087] Table 1 Performance data of 4-AA, a penem intermediate of the present invention.

[0088] Test Project Performance data Appearance White or off-white crystalline powder Melting point 105.0～109.0℃ Moisture ≤0.2% specific rotation [a 25 D]]]> +48.0°～+55.0° chromatographic purity ≥99.5%

[0089] Comparative Example 1

[0090] Replace “carbonyl reductase” in step (2) of Example 1 with “carbonyl reductase mutant from Chinese Patent CN115433721A”, and follow the same steps as in step (2). 105.3 g of methyl (2S,3R)-2-nitromethyl-3-hydroxybutyrate was obtained, with a yield of 74.9% and a purity of 97.85%.

[0091] By comparing Example 1 and Comparative Example 1, it can be seen that Comparative Example 1 changed the type of reductase, which significantly reduced the yield of methyl (2S,3R)-2-nitromethyl-3-hydroxybutyrate. If the methyl (2S,3R)-2-nitromethyl-3-hydroxybutyrate obtained in Comparative Example 1 is used to prepare penem intermediate 4-AA, the overall yield of penem intermediate 4-AA will be reduced.

[0092] Comparative Example 2

[0093] The (2S,3R)-2-nitromethyl-3-hydroxybutyrate methyl ester obtained in step (2) of Example 1 was first subjected to a hydrogenation reduction reaction to obtain (2S,3R)-2-aminomethyl-3-hydroxybutyrate methyl ester. The (2S,3R)-2-aminomethyl-3-hydroxybutyrate methyl ester was then reacted with tert-butyldimethylchlorosilane to obtain (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate methyl ester. The specific steps are as follows:

[0094] (3) Mix the (2S,3R)-2-nitromethyl-3-hydroxybutyrate methyl ester obtained in step (2) of Example 1, 5.48 g of 5% Pd / C catalyst, and 932 ml of ethyl acetate. Replace the air with nitrogen three times, and then replace the nitrogen with hydrogen three times. Then introduce 12.6 g of hydrogen to carry out a hydrogenation reduction reaction for 4.5 hours, control the reaction temperature at 40°C and the reaction pressure at 3.0 MPa, filter, and obtain a filtrate containing (2S,3R)-2-aminomethyl-3-hydroxybutyrate methyl ester (containing 82.3 g of (2S,3R)-2-aminomethyl-3-hydroxybutyrate methyl ester).

[0095] (4) Add 43.8 g of imidazole to the above filtrate containing (2S,3R)-2-aminomethyl-3-hydroxybutyrate methyl ester, heat to 85°C, add a mixed solution of tert-butyldimethylchlorosilane and toluene (92.7 g of tert-butyldimethylchlorosilane and 200 mL of toluene), react at 100°C for 5 hours under nitrogen protection, and when the raw material is controlled to be ≤2.0% in the liquid phase detection, slowly lower the system temperature to below 45°C, wash with water, and remove the solvent from the organic phase under reduced pressure to obtain 119.4 g of (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate methyl ester with a purity of 57.24%.

[0096] (5) Mix 392.1 ml of tetrahydrofuran solution of tert-butyl magnesium chloride (with a concentration of 2.0 mol / L of tert-butyl magnesium chloride) with 239 mL of n-heptane. Add the above-mentioned (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate methyl ester dropwise to the reaction system at -5 to 0°C and react for 5 hours. After the reaction is completed, raise the temperature to 12°C, add acetic acid to adjust the pH value to 6.5, add water and let stand. The organic phase is separated into layers. The organic phase is concentrated and crystallized at 0 to 3°C for 2 hours. After filtration, dry under reduced pressure at 40°C for 8 hours to obtain 48.8 g of (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone, with a yield of 79.8% and a purity of 98.01%.

[0097] During steps (3), (4), and (5), the overall yield of (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone was 32.1%.

[0098] (6) Under nitrogen protection, 142.5 g of acetic acid, 19.0 g of potassium acetate, 475.0 mL of ethyl acetate and the above (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone were mixed and cooled to -5 to -3 °C. 0.048 g of ruthenium trichloride was added with stirring. 538.4 g of peracetic acid solution (concentration of 19 wt%) was slowly added dropwise to the reaction system. The system temperature was maintained at -5 to -3 °C for 1 hour. Saturated NaHSO3 aqueous solution was added to quench the reaction and the reaction system was directly concentrated at 45 °C. The reaction solution was filtered, the filter cake was washed, and dried at 50 °C for 7 hours to obtain 61.5 g of penem drug intermediate 4-AA, with a yield of 95.7% and a purity of 93.210%.

[0099] By comparing Example 1 and Comparative Example 2, it can be seen that during the reaction of (2S,3R)-2-aminomethyl-3-hydroxybutyrate methyl ester with tert-butyldimethylchlorosilane in Comparative Example 2, the amino group in the (2S,3R)-2-aminomethyl-3-hydroxybutyrate methyl ester structure also reacts with tert-butyldimethylchlorosilane, resulting in a side reaction. This leads to a significant reduction in the purity of (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate methyl ester, which in turn reduces the overall yield of (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone in steps (3), (4), and (5), ultimately resulting in a significant reduction in the overall yield of penem intermediate 4-AA.

[0100] This invention is not limited to the above-described embodiments. Anyone should know that any structural changes made under the guidance of this invention, and any technical solutions that are the same as or similar to this invention, fall within the protection scope of this invention.

[0101] The technologies, shapes, and structures not described in detail in this invention are all known technologies.

Claims

1. A method for synthesizing 4-AA, an intermediate in penem drugs, characterized in that, Includes the following steps: (1) Using bromonitromethane as a raw material, methyl acetoacetate and sodium methoxide are added to react and methyl 2-nitromethyl-3-oxobutyrate is obtained; (2) Methyl 2-nitromethyl-3-oxobutyrate is first reduced by carbonyl reductase to give methyl (2S,3R)-2-nitromethyl-3-hydroxybutyrate; methyl (2S,3R)-2-nitromethyl-3-hydroxybutyrate reacts with tert-butyldimethylchlorosilane to give methyl (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate. (3) Methyl (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate was subjected to hydrogenation reduction to obtain methyl (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate. (4) Methyl (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate undergoes a cyclization reaction to give (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone; (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone is then reacted with peracetic acid to give penem intermediate 4-AA.

2. The method for synthesizing penem intermediate 4-AA according to claim 1, characterized in that, In step (1), the molar ratio of bromonitromethane to methyl acetoacetate is 1:1.05 to 1.15, the molar ratio of methyl acetoacetate to sodium methoxide is 1:1 to 1.05, the reaction temperature is -5 to 5℃, and the reaction time is 2 to 4 hours. In step (2), the mass ratio of methyl 2-nitromethyl-3-oxobutyrate to carbonyl reductase is 1:0.21-0.24, and the NCBI accession number of carbonyl reductase is CDZ96865.1; the enzyme reduction reaction temperature is 30-40℃, and the enzyme reduction reaction time is 15-25 hours; (2S,3R)-2-nitromethyl-3-hydroxybutyrate methyl ester and tert-butyldimethylchlorosilane are reacted at 90-110℃ for 4-6 hours.

3. The method for synthesizing penem intermediate 4-AA according to claim 1, characterized in that, In step (3), the hydrogenation reduction reaction temperature is 30-50℃, the hydrogenation reduction reaction time is 3-6 hours, and the hydrogenation reduction reaction pressure is 0.1-5MPa; in step (4), the ring-closing reaction temperature is -5-10℃, and the ring-closing reaction time is 2-5 hours.

4. The method for synthesizing penem drug intermediate 4-AA according to claim 1 or 2, characterized in that, The specific operation of step (1) is as follows: mix toluene, methyl acetoacetate and sodium methoxide in methanol, add a mixture of bromonitromethane and toluene to react, adjust the pH value after the reaction is completed, separate the organic phase, concentrate under reduced pressure to obtain methyl 2-nitromethyl-3-oxobutyrate. The ratio of toluene to methyl acetoacetate is 4.5–6.5:1, with toluene measured in ml and methyl acetoacetate in g; the concentration of sodium methoxide in the methanol solution is 27–30 wt%; in the mixture of bromonitromethane and toluene, the ratio of bromonitromethane to toluene is 1:4–5, with bromonitromethane measured in g and toluene in ml; the pH is adjusted to ≤5.0 using hydrochloric acid solution, with a concentration of 30–35 wt%.

5. The method for synthesizing penem intermediate 4-AA according to claim 1 or 2, characterized in that, The specific operation of the enzyme reduction reaction in step (2) is as follows: dissolve methyl 2-nitromethyl-3-oxobutyrate in phosphate buffer, and add carbonyl reductase solution, glucose dehydrogenase, glucose and coenzyme NADP. + The pH value was initially adjusted to carry out the enzyme reduction reaction, the pH value was adjusted again, and the mixture was filtered. The filter cake was extracted and washed, and the resulting organic phase was distilled, crystallized, filtered, and dried to obtain methyl (2S,3R)-2-nitromethyl-3-hydroxybutyrate. The mass ratio of methyl 2-nitromethyl-3-oxobutyrate to phosphate buffer is 1:4–5.2, and the pH of the phosphate buffer is 7.0–7.5; the molar ratio of glucose to methyl 2-nitromethyl-3-oxobutyrate is 1.01–1.08:1; and the components include methyl 2-nitromethyl-3-oxobutyrate, glucose dehydrogenase, and NADP coenzyme. + The mass ratio is 1:2~3.5:0.0006~0.001; the enzyme content in the carbonyl reductase solution is 10~12wt%.

6. The method for synthesizing penem drug intermediate 4-AA according to claim 5, characterized in that, The pH value was initially adjusted to 7.65–7.85 using sodium hydroxide solution, and then adjusted again to 4.0–4.5 using citric acid solution; the concentration of sodium hydroxide solution was 8–12 wt%, and the concentration of citric acid solution was 28–32 wt%; the crystallization temperature was 0–10℃, the crystallization time was 1–3 hours, the drying temperature was 40–60℃, and the drying time was 4–8 hours.

7. The method for synthesizing penem intermediate 4-AA according to claim 5, characterized in that, The specific operation of the reaction between (2S,3R)-2-nitromethyl-3-hydroxybutyrate methyl ester and tert-butyldimethylchlorosilane in step (2) is as follows: an acid-binding agent is added to (2S,3R)-2-nitromethyl-3-hydroxybutyrate methyl ester, the temperature is raised to 80-90°C, a mixed solution of tert-butyldimethylchlorosilane and toluene is added, and the temperature is further raised to 90-110°C under nitrogen protection for reaction. The mixture is then cooled, washed, and the solvent is removed by vacuum evaporation to obtain (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate methyl ester. The molar ratio of (2S,3R)-2-nitromethyl-3-hydroxybutyrate methyl ester, tert-butyldimethylchlorosilane, and the acid-binding agent is 1:1.06-1.10:1.06-1.15, and the acid-binding agent is imidazole.

8. The method for synthesizing penem intermediate 4-AA according to claim 1 or 3, characterized in that, The specific operation of the hydrogenation reduction reaction in step (3) is as follows: (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate methyl ester, catalyst, and ethyl acetate are mixed, and then hydrogen is introduced to carry out the hydrogenation reduction reaction. After filtration, (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate methyl ester is obtained. Wherein: the molar ratio of (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate to hydrogen is 1:9-11; the amount of catalyst is 2-4% of the mass of (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate, and the catalyst is 5% Pd / C; the ratio of ethyl acetate to (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate is 5-7:1, ethyl acetate is in ml, and (2S,3R)-2-nitromethyl-3-tert-butyldimethylsiloxybutyrate is in g.

9. The method for synthesizing penem drug intermediate 4-AA according to claim 1 or 3, characterized in that, The specific operation of the cyclization reaction in step (4) is as follows: Grignard reagent is mixed with n-heptane, and (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxymethylbutyrate is added to react. After the reaction is completed, acetic acid is added to adjust the pH value, water is added and allowed to stand, and the organic phase is obtained by separation. The organic phase is concentrated, crystallized, filtered and dried to obtain (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone. The molar ratio of methyl (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate to Grignard reagent is 1:2.5-3.5, and the Grignard reagent is tert-butylmagnesium chloride; the molar ratio of methyl (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate to n-heptane is 1:3-4, and the amount of methyl (2S,3R)-2-aminomethyl-3-tert-butyldimethylsiloxybutyrate is in g, while the amount of n-heptane is in ml; the pH is adjusted to 6.5-7, the crystallization temperature is 0-10℃, and the crystallization time is 0.5-2.0 hours.

10. The method for synthesizing penem intermediate 4-AA according to claim 1 or 3, characterized in that, The specific operation of the reaction between (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone and peracetic acid in step (4) is as follows: under nitrogen protection, acetic acid, potassium acetate, ethyl acetate and (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone are mixed, a catalyst and peracetic acid solution are added to carry out the reaction, quench, concentrate, filter, wash and dry to obtain penem drug intermediate 4-AA; The molar ratio of (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone to peracetic acid is 1:6-7, and the concentration of the peracetic acid solution is 15-20 wt%; the ratio of potassium acetate, acetic acid, ethyl acetate to (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone is 0.3-0.5:2-4:8-12:1, with potassium acetate, acetic acid, (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone calculated in g, and ethyl acetate calculated in ml; the molar ratio of (1R)-(tert-butyldimethylsiloxy)ethyl-(3S)-azacyclobutanone to catalyst is 1:0.0005-0.001, and the catalyst is ruthenium trichloride; the reaction temperature is -10 to 0℃, and the reaction time is 1-3 hours.

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