A biodegradable polyester amide with side chain base having stereocomplex crystallization performance and an enzymatic preparation method thereof

Abstract

The present invention discloses a biodegradable polyester amide with a side chain base having stereocomplex crystallization performance and an enzymatic preparation method thereof. The method uses D- or L-glutamic acid / aspartic acid derivatives as starting materials, and prepares a polymerization monomer containing a side chain base through a series of derivatization reactions. The polymerization monomer obtains a polyester amide with an optically pure side chain base under the catalysis of a protease. Such D- and L-configured polyester amides can form a D- / L-layer alternating stereocomplex structure through specific recognition of side chain bases under certain conditions to achieve stereocomplex crystallization of the polymer. Compared with polyester amides of a single configuration, the melting point of polyester amides with a stereocomplex structure is increased. The preparation method of the biodegradable polyester amide of the present invention uses naturally abundant amino acid derivatives as starting materials, and improves the thermal properties of the obtained polymer through a stereocomplex crystallization method, providing a new perspective for solving "white pollution".

Description

Technical Field

[0001] The invention belongs to the field of preparation of novel biodegradable materials, and in particular relates to a side chain base biodegradable polyester amide with stereocomplex crystallization performance and an enzymatic preparation method thereof. Background Art

[0002] "White pollution" is one of the biggest environmental challenges faced by mankind since the 20th century. Faced with the increasingly serious problem of plastic pollution, finding a substitute for plastic is undoubtedly an important scientific issue that urgently needs to be solved in the field of polymer materials. Polyester materials are a new type of material with very good biodegradability and biocompatibility. It has been regarded as the best substitute for plastic and is also considered to be one of the most effective ways to solve "white pollution". Compared with traditional polymer materials (such as polyamide, polyethylene, etc.), the lower bond energy of ester bonds gives polyester materials good biodegradability, which can solve the environmental pollution problems caused by traditional plastics. However, this characteristic also leads to relatively poor thermal and mechanical properties of polyester materials, which greatly limits its application.

[0003] Therefore, exploring new polyester materials with excellent performance and researching ways to improve the performance of polyester materials have very important scientific value and practical significance for solving the current plastic pollution dilemma.

[0004] In recent years, chiral polymers have shown excellent application prospects in nonlinear optics, biomedical materials, and gene therapy. Among the many properties of chiral polymers, stereocomplex crystallization behavior is undoubtedly the most direct and effective way to improve their thermal / mechanical properties. R - / S -The chiral polymers can be greatly improved in thermal / mechanical properties by forming alternating layers of stereocomplexes. In view of this, applying the stereocomplex crystallization theory of chiral polymers to polyester research, designing chiral polyester materials with unique structures and using their stereocomplex crystallization behavior to improve thermal / mechanical properties is one of the important measures to achieve polyester materials replacing traditional plastics and fundamentally solve the "white pollution".

[0005] Domestic and foreign researchers have achieved many fruitful results in the field of stereocomplex crystallization of chiral polyesters: Coates of Cornell University in the United States, Professor Lv Xiaobing of Dalian University of Technology in China, and Professor Pan Pengju of Zhejiang University have all discovered a variety of chiral polyesters with stereocomplex crystallization properties. However, these studies are almost all confined to poly (epoxide-diacid) esters and polylactic acid chiral polymers. Therefore, designing chiral polyester molecules with stereocomplex crystallization properties and realizing their efficient synthesis has extremely important scientific value and practical significance. Summary of the invention

[0006] In view of the above problems existing in the prior art, the object of the present invention is to provide a biodegradable polyester amide with side chain bases having stereocomplex crystallization properties and an enzymatic preparation method thereof.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A biodegradable polyester amide with side chain base having stereocomplex crystallization performance, wherein the main chain of the structure is a dimer repeating unit of glutamic acid or aspartic acid and amino alcohol, and the side chain is acylated adenine or thymine, and the structural formula thereof is shown in Formula I:

[0009] ;

[0010] In the formula, x is 0 or 1, y is 2 or 4; the substituent R is thymine or adenine; the configuration of the polyester amide is D-configuration or L-configuration; and n is an integer ranging from 20-70.

[0011] Furthermore, the molecular weight of the polyester amide is 8.0×10 3 -30.0×10 3 g / mol, chiral configuration is L -configuration or D-configuration, and the polymer type is polyesteramide.

[0012] The present invention also provides an enzymatic preparation method of a side chain base biodegradable polyester amide with stereocomplex crystallization performance, comprising the following steps:

[0013] Step 1: α-carboxyl-N-tert-butyloxycarbonyl-glutamic acid monomethyl ester or α-carboxyl-N-tert-butyloxycarbonyl-aspartic acid monomethyl ester as shown in formula 1 is used as a substrate, and the molecular configuration of the substrate is L - or D-configuration, react with pentafluorophenyl trifluoroacetate shown in formula 2 in the presence of DMF as solvent and pyridine as acid-binding agent, and stir overnight at room temperature under nitrogen protection to prepare the compound of formula 3, that is, L - or D-configuration intermediate 1, the reaction formula is as follows:

[0014] ;

[0015] Step 2: Using triethylamine as an acid-binding agent, the intermediate 1 obtained in step 1 reacts with the amino alcohol shown in formula 4 in DMF solvent, and the mixture is stirred at room temperature under nitrogen protection for 20-30 hours. After the reaction, the compound of formula 5, i.e., the corresponding intermediate 2, is obtained by post-treatment. The reaction formula is as follows:

[0016] ;

[0017] Step 3: The intermediate 2 obtained in step 2 is reacted with trifluoroacetic acid in DCM solvent, and stirred overnight at room temperature under nitrogen protection. After the reaction is completed, the solvent is removed by concentration under reduced pressure to obtain a crude product, and the crude product is purified by column chromatography to obtain a compound of formula 6, namely, intermediate 3;

[0018] ;

[0019] Step 4: Adenine acetic acid shown in Formula 7 or thymine acetic acid shown in Formula 8 is used as a starting material, and reacts with pentafluorophenyl trifluoroacetate shown in Formula 9 in the presence of DMF as a solvent and pyridine as an acid-binding agent to prepare pentafluorophenyl adenine or thymine acetic acid shown in Formula 10 or Formula 11, i.e., intermediate 4. The reaction formula is as follows:

[0020] ;

[0021] Step 5: Using triethylamine as an acid-binding agent, the intermediate 3 obtained in step 3 and the intermediate 4 obtained in step 4 are reacted in DMF solvent, and stirred at room temperature for 20-30 hours under nitrogen protection. After the reaction, the compound of formula 12, i.e., the corresponding polymerization monomer, is obtained by post-treatment, and its structural formula is as follows:

[0022] ;

[0023] Step 6: alkaline protease is added in two parts. The polymerizable monomer prepared in step 5 is added to a DMF-phenyl ether mixed solvent, and the first part of alkaline protease is added, heated to 75-90° C., stirred for 10-15 hours under nitrogen protection, and then reduced to 100-300 mbar for reaction for 12-20 hours, and then the second part of alkaline protease is added, and the reaction is continued at 5-20 mbar for 60-80 hours. After the reaction is completed, the target product shown in formula I is obtained by post-treatment;

[0024] Wherein, x, y, and R in Formula 1, Formula 3-6, and Formula 12 are defined the same as in Formula I.

[0025] Furthermore, in step 1, the molar ratio of the compound of formula 2 to the compound of formula 1 is 1.2-1.5:1, and the molar ratio of pyridine to the compound of formula 1 is 1.5-2:1. After the reaction in step 1 is completed, the following post-treatment step is also included: adding water to quench the reaction, extracting the reaction solution with ethyl acetate, combining the organic phases, drying with anhydrous magnesium sulfate, and concentrating under reduced pressure to obtain a crude product, and the crude product is purified by column chromatography, and the eluent is a mixture of ethyl acetate / petroleum ether in a volume ratio of 1:3-8.

[0026] Furthermore, in step 2, the molar ratio of intermediate 1 to the compound of formula 4 is 1:1.5-2.5. After the reaction in step 2 is completed, the following post-treatment step is also included: adding water to quench the reaction, extracting the reaction solution with ethyl acetate, combining the organic phases, drying with anhydrous magnesium sulfate, and concentrating under reduced pressure to obtain a crude product. The crude product is purified by column chromatography, and the eluent is a mixture of ethyl acetate / petroleum ether in a volume ratio of 1:2-5.

[0027] Furthermore, in step 3, the molar ratio of intermediate 2 to trifluoroacetic acid is 1:3-8, and the eluent for column chromatography purification in step 3 is a mixture of ethyl acetate / petroleum ether in a volume ratio of 1:2-5.

[0028] Furthermore, in step 4, the molar ratio of adenine acetic acid shown in formula 7 or thymine acetic acid shown in formula 8 to pentafluorophenyl trifluoroacetate is 1:1.2-1.5, and after the reaction in step 4 is completed, the following post-treatment step is also included: adding water to quench the reaction, extracting the reaction solution with ethyl acetate, combining the organic phases, drying with anhydrous magnesium sulfate, and concentrating under reduced pressure to obtain a crude product, and the crude product is purified by column chromatography, and the eluent is a mixed solution of ethyl acetate / petroleum ether with a volume ratio of 1:3-8.

[0029] Furthermore, in step 5, the molar ratio of intermediate 3 to intermediate 4 is 1:1.5-2.5, and after the reaction in step 5 is completed, the following post-treatment steps are also included: adding water to quench the reaction, extracting the reaction solution with ethyl acetate, combining the organic phases, drying with anhydrous magnesium sulfate, and concentrating under reduced pressure to obtain a crude product, and the crude product is purified by column chromatography, and the eluent is a mixture of ethyl acetate / petroleum ether in a volume ratio of 1:2-5.

[0030] Furthermore, in step 6, the volume ratio of DMF-phenyl ether is 1:3-5, the alkaline protease is an alkaline protease derived from Bacillus subtilis, the mass ratio of the first part and the second part of the alkaline protease is 0.8-1.2:1, and when the enzyme activity of the alkaline protease is 500,000 U / g, the total mass of the two parts of the alkaline protease is 30-40% of the mass of the polymerized monomer.

[0031] Furthermore, the post-treatment steps after the reaction in step 6 are: cooling to room temperature, adding DMF to dissolve the product, filtering to remove the enzyme, dropping the filtrate into an ethyl acetate solution at 2-5°C to precipitate, filtering, and drying to obtain the target product.

[0032] The stereocomplex crystallization process of the side chain base biodegradable polyester amide with stereocomplex crystallization performance is as follows:

[0033] 1) The D-configuration side chain and the L-configuration side chain of the polyester amide of the present invention are complementary bases. The D-configuration polyester amide and the L-configuration polyester amide are dissolved in DMF at a mass ratio of 1:1, and then the mixed solution is dropped into ethyl acetate or n-hexane, placed in a refrigerator at 2-5°C and allowed to stand, precipitated, centrifuged, and vacuum dried at room temperature to obtain the corresponding stereocomplex. The melting point of the stereocomplex is measured using a differential scanning calorimeter (DSC).

[0034] 2) The D-configuration side chain and the L-configuration side chain of the polyester amide of the present invention are complementary bases. The D-configuration polyester amide and the L-configuration polyester amide are mixed and melted in a mass ratio of 1:1, cooled to room temperature, and stored in a refrigerator at 2-5°C for 5-20 days to obtain the corresponding stereocomplex. The melting point of the stereocomplex is measured using a differential scanning calorimeter (DSC).

[0035] The biodegradable polyester amide with side chain base having stereocomplex crystallization performance has the following biodegradation process: a certain amount of side chain base polyester amide is placed in a beaker containing an aqueous solution of common pond sludge, and then stirred at room temperature for 60 days, filtered, and the filtrate is freeze-dried. The molecular weight of the residue is detected by gel permeation chromatography (GPC). The molecular weight of the residue is less than 1.5×10 3 g / mol.

[0036] By adopting the above technology, compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] The invention adopts naturally abundant amino acid derivatives as starting materials to prepare side chain base polyester amide, and the production cost is low. In addition, through the specific recognition of the side chain base, the prepared polyester amide has stereocomplex crystallization performance, and its melting point is increased by nearly 45°C compared with the polyester amide of single configuration, which greatly improves the thermal performance of the polyester amide. Finally, the polyester amide also has excellent biodegradability, and the residual polymer molecular weight after 60 days of decomposition is less than 1.5×10 3 g / mol, which greatly alleviates the environmental pressure brought by polymer materials. DETAILED DESCRIPTION

[0038] The present invention is further described below in conjunction with embodiments, but the protection scope of the present invention is not limited thereto.

[0039] 1. Preparation of polymer monomers

[0040] The general structural formula of the polymerizable monomer shown in Formula 12 is as follows:

[0041] ;

[0042] In formula 12, x is 0 or 1, y is 2 or 4, and the substituent R is thymine or adenine.

[0043] The preparation route of the polymerizable monomer shown in Formula 12 includes:

[0044] 1) Compound 1 reacts with compound 2 to generate compound 3, which is intermediate 1;

[0045] ;

[0046] 2) Compound 3 reacts with compound 4 to generate compound 5, which is intermediate 2;

[0047] ;

[0048] 3) Compound 5 reacts with trifluoroacetic acid in DCM solvent to generate compound 6, i.e. intermediate 3, whose structural formula is as follows:

[0049] ;

[0050] 4) Adenine acetic acid shown in Formula 7 or thymine acetic acid shown in Formula 8 reacts with pentafluorophenyl trifluoroacetate shown in Formula 9 to generate compound 10 or 11, i.e., intermediate 4. The reaction formula is as follows:

[0051] ;

[0052] 5) Intermediate 4 reacts with compound 6 to generate compound 12, which is the corresponding polymerization monomer. Example 1

[0053] In compound 1, compounds 3-6 and compound 12, x=1, y=4, and R is adenine.

[0054] 1) N- Preparation of Boc-L-glutamic acid-1-pentafluorophenyl-5-methyl ester, compound 3

[0055] The preparation chemical reaction equation is as follows:

[0056]

[0057] 1.3 g L -α-Carboxyl- N -tert-Butyloxycarbonyl-glutamic acid monomethyl ester, i.e. compound 1, was dissolved in 10 mL DMF, followed by addition of 2.1 g of trifluoroacetic acid pentafluorophenyl ester, i.e. compound 2 and 0.8 g of pyridine, and stirred at room temperature under nitrogen protection for 16 hours. After the reaction was completed, 20 mL of water was added to quench the reaction. The reaction solution was extracted with ethyl acetate (30 mL×3), the combined organic phases were dried over anhydrous magnesium sulfate, and concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography with an eluent of ethyl acetate / petroleum ether in a volume ratio of 1 / 5 to obtain pureN- Boc-L-glutamic acid-1-pentafluorophenyl-5-methyl ester is compound 3, with a yield of 86%. The structure of the obtained product is characterized by hydrogen nuclear magnetic resonance spectrum.

[0058] 1 H-NMR (400 MHz, DMSO- d 6), δ 7.05 (brs, 1H), 4.21-4.13 (m, 1H), 3.65 (s, 3 H), 2.52-2.36 (m, 4H), 1.18 (s, 9H) ppm.

[0059] 2) N- Preparation of Boc-L-glutamic acid-1-(6-amino-1-hexanol)-5-methyl ester, compound 5

[0060] 0.85 g of compound 3 prepared in step 1 was dissolved in 5 mL of DMF, followed by the addition of 0.47 g of the corresponding aminohexanol, i.e., compound 4, and 0.2 g of triethylamine, and stirred at room temperature for 24 hours under nitrogen protection. After the reaction was completed, 20 mL of water was added to quench the reaction. The reaction solution was extracted with ethyl acetate (30 mL×3), the combined organic phases were dried over anhydrous magnesium sulfate, and concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography with an eluent of ethyl acetate / petroleum ether in a volume ratio of 1 / 3 to obtain pure N- Boc-L-glutamic acid-1-(6-amino-1-hexyl)-5-methyl ester is compound 5, with a yield of 80%. The structure of the obtained product is characterized by hydrogen nuclear magnetic resonance spectrum.

[0061] 1 H-NMR (400 MHz, DMSO- d 6), δ 8.23 ​​(brs, 1H), 7.22 (brs, 1H), 4.18-4.07 (m, 1H), 3.83(m, 2H), 3.62(s, 3H), 3.05(m, 2H), 2.42-2.33 (m, 4H),1.42-1.38(m, 4H), 1.16(s, 9H), 1.08-1.03(m, 4H) ppm. The active hydrogen on the hydroxyl group was not observed in the H NMR spectrum.

[0062] 3) Preparation of L-glutamic acid-1-(6-amino-1-hexanol)-5-methyl ester

[0063] ;

[0064] 0.72 g of compound 5 prepared in step 2 was dissolved in 20 mL of dichloromethane, and then 1.14 g of trifluoroacetic acid was added, and the mixture was stirred at room temperature under nitrogen protection for 16 hours. After the reaction was completed, the mixture was concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography with an eluent of ethyl acetate / petroleum ether in a volume ratio of 1 / 3 to obtain pure L-glutamic acid-1-(6-amino-1-hexyl)-5-methyl ester, i.e., compound 6, with a yield of 95%.

[0065] 1 H-NMR (400 MHz, DMSO- d 6), δ 9.03 (brs, 2H), 8.45 (brs, 1H), 3.76(m,2H), 3.61(s, 3H), 3.05-2.96(m, 3H), 2.35-2.18 (m, 4H),1.53-1.14(m, 8H), ppm. The active hydrogen on the hydroxyl group was not observed in the H NMR spectrum.

[0066] 4) Preparation of adenine acetyl pentafluorophenyl ester, compound 10

[0067] The preparation chemical reaction equation is as follows:

[0068] ;

[0069] 0.96 g of adenine acetic acid (A-CH2COOH) was dissolved in 10 mL of DMF, followed by the addition of 2.1 g of pentafluorophenyl trifluoroacetate and 0.8 g of pyridine, and the mixture was stirred overnight at room temperature under nitrogen protection. After the reaction was completed, 20 mL of water was added to quench the reaction. The reaction solution was extracted with ethyl acetate (30 mL×3), the combined organic phases were dried over anhydrous magnesium sulfate, and concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography with an eluent of ethyl acetate / petroleum ether in a volume ratio of 1 / 5 to obtain pure adenine acetyl pentafluorophenyl ester, i.e., compound 10, with a yield of 60%. The structure of the obtained product was characterized by hydrogen nuclear magnetic resonance spectroscopy.

[0070] 1 H-NMR (400 MHz, DMSO- d 6), δ 8.23(s, 1H), 8.15(s, 1H), 7.14(s, 2H), 5.03(s, 2H) ppm.

[0071] 5) Preparation of N-adenine acetyl-L-glutamic acid-1-(6-amino-1-hexanol)-5-methyl ester, compound 12

[0072] 0.78 g of compound 6 prepared in step 3 was dissolved in 5 mL of DMF, followed by addition of 2.07 g of compound 10 prepared in step 4 and 0.61 g of triethylamine, and stirred at room temperature under nitrogen protection for 24 hours. After the reaction was completed, 20 mL of water was added to quench the reaction. The reaction solution was extracted with ethyl acetate (30 mL×3), the combined organic phases were dried over anhydrous magnesium sulfate, and concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography with an eluent of ethyl acetate / petroleum ether in a volume ratio of 1 / 3 to obtain pure N-adenine acetyl-L-glutamic acid 1-(6-amino-1-hexanol)-5-methyl ester, i.e., compound 12, with a yield of 76%. The structure of the obtained product was characterized by hydrogen nuclear magnetic resonance spectroscopy.

[0073] 1 H-NMR (400 MHz, DMSO- d 6), δ 9.08(brs, 1H), 8.17(s, 1H), 8.08(s, 1H),7.94 (s, 1H), 7.14(s, 2H), 5.98(s, 2H), 4.56(m, 1H), 3.69(m, 2H), 3.62(s,3H), 3.35(m, 2H), 2.31-2.12 (m, 4H),1.48-1.09(m, 8H) ppm. The active hydrogen on the hydroxyl group was not observed in the H NMR spectrum. Example 2

[0074] In compound 1, compounds 3-6 and compound 12, x=0, y=2, and R is thymine.

[0075] 1) N- Preparation of Boc-D-aspartic acid-1-pentafluorophenyl-4-methyl ester, compound 3

[0076] The preparation chemical reaction equation is as follows:

[0077] ;

[0078] 1.23 g D -α-Carboxyl- N -tert-Butyloxycarbonyl-aspartic acid monomethyl ester, i.e. compound 1, was dissolved in 10 mL DMF, followed by addition of 2.1 g of trifluoroacetic acid pentafluorophenyl ester, i.e. compound 2 and 0.8 g of pyridine, and stirred at room temperature for 16 hours under nitrogen protection. After the reaction was completed, 20 mL of water was added to quench the reaction. The reaction solution was extracted with ethyl acetate (30 mL×3), the combined organic phases were dried over anhydrous magnesium sulfate, and concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography with an eluent of ethyl acetate / petroleum ether in a volume ratio of 1 / 5 to obtain pure N-Boc-D-aspartic acid-1-pentafluorophenyl-4-methyl ester, yield 80%. The structure of the obtained product was characterized by H NMR.

[0079] 1 H-NMR (400 MHz, DMSO- d 6), δ 7.08 (brs, 1H), 4.56-4.48 (m, 1H), 3.63 (s, 3 H), 2.98-2.87 (m, 2H), 1.16 (s, 9H) ppm.

[0080] 2) N- Preparation of Boc-D-aspartic acid-1-(4-amino-1-butanol)-4-methyl ester, compound 5

[0081] 0.82 g of compound 3 prepared in step 1 was dissolved in 5 mL of DMF, followed by the addition of the corresponding 0.36 g of aminobutanol, i.e., compound 4, and 0.2 g of triethylamine, and stirred at room temperature for 24 hours under nitrogen protection. After the reaction was completed, 20 mL of water was added to quench the reaction. The reaction solution was extracted with ethyl acetate (30 mL×3), the combined organic phases were dried over anhydrous magnesium sulfate, and concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography with an eluent of ethyl acetate / petroleum ether in a volume ratio of 1 / 3 to obtain pure N- Boc-D-aspartic acid-1-(4-amino-1-butanol)-4-methyl ester is compound 5, with a yield of 84%. The structure of the obtained product is characterized by hydrogen nuclear magnetic resonance spectrum.

[0082] 1 H-NMR (400 MHz, DMSO- d 6), δ 7.98(brs, 1H), 7.06 (brs, 1H), 4.45-4.38(m, 1H), 3.65 (s, 3 H), 3.46-3.22(m, 4H), 2.92-2.88 (m, 2H), 1.43-1.38(m,4H), 1.12 (s, 9H) ppm, the active hydrogen of the hydroxyl group was not observed in the NMR spectrum.

[0083] 3) Preparation of D-aspartic acid-1-(4-amino-1-butanol)-4-methyl ester

[0084] The preparation chemical reaction equation is as follows:

[0085] ;

[0086] 0.64 g of compound 5 prepared in step 2 was dissolved in 20 mL of dichloromethane, and then 1.14 g of trifluoroacetic acid was added, and the mixture was stirred at room temperature under nitrogen protection for 16 hours. After the reaction was completed, the mixture was concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography with an eluent of ethyl acetate / petroleum ether in a volume ratio of 1 / 3 to obtain pure L-glutamic acid-1-(6-amino-1-hexyl)-4-methyl ester, i.e., compound 6, with a yield of 93%.

[0087] 1 H-NMR (400 MHz, DMSO- d 6), δ 9.03(brs, 2H), 7.04 (brs, 1H), 4.12-4.07(m, 1H), 3.62(s, 3 H), 3.44-3.18(m, 4H), 2.90-2.86 (m, 2H), 1.42-1.37(m, 4H)ppm, the active hydrogen of the hydroxyl group was not observed in the NMR spectrum.

[0088] 4) Preparation of thymine acetyl pentafluorophenyl ester, compound 11

[0089] ;

[0090] 0.92 g of thymine acetic acid (T-CH2COOH) was dissolved in 10 mL of DMF, followed by the addition of 2.1 g of pentafluorophenyl trifluoroacetate and 0.8 g of pyridine, and stirred at room temperature under nitrogen protection for 16 hours. After the reaction was completed, 20 mL of water was added to quench the reaction. The reaction solution was extracted with ethyl acetate (30 mL×3), the combined organic phases were dried over anhydrous magnesium sulfate, and concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography with an eluent of ethyl acetate / petroleum ether in a volume ratio of 1 / 5 to obtain pure thymine acetyl pentafluorophenyl ester, i.e., compound 11, with a yield of 72%. The structure of the obtained product was characterized by hydrogen nuclear magnetic resonance spectroscopy.

[0091] 1 H-NMR (400 MHz, DMSO- d 6), δ 11.56(s, 1H), 7.65(s, 1H), 5.00(s, 2H), 1.79(s, 3H) ppm.

[0092] 5) N- Preparation of thymine acetyl-D-aspartic acid-1-(4-amino-1-butanol)-4-methyl ester, compound 12

[0093] 0.65 g of compound 6 prepared in step 3 was dissolved in 5 mL of DMF, followed by the addition of 2.01 g of compound 11 prepared in step 4 and 0.61 g of triethylamine, and stirred at room temperature for 24 hours under nitrogen protection. After the reaction was completed, 20 mL of water was added to quench the reaction. The reaction solution was extracted with ethyl acetate (30 mL×3), the combined organic phases were dried over anhydrous magnesium sulfate, and concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography with an eluent of ethyl acetate / petroleum ether in a volume ratio of 1 / 3 to obtain pure N- Thymine acetyl-D-aspartic acid-1-(4-amino-1-butanol)-4-methyl ester is compound 12, with a yield of 70%. The structure of the obtained product is characterized by hydrogen nuclear magnetic resonance spectroscopy.

[0094] 1 H-NMR (400 MHz, DMSO- d 6), δ 11.54(s,1H), 8.28(brs, 1H), 8.08(brs,1H), 7.58(s, 1H), 4.98(s, 2H), 4.45-4.38(m, 1H), 3.65(s, 3H), 3.43-3.16(m,4H), 2.92-2.86 (m, 2H), 1.44-1.39(m, 4H), 1.82(s, 3H) ppm, the active hydrogen of the hydroxyl group was not observed in the NMR spectrum.

[0095] 2. Enzymatic polymerization of side chain base polyester amides

[0096] Example 3

[0097] Preparation of Poly-N-Adenine Acetyl-L-Glutamic Acid-1-(6-Amino-1-Hexanol) Ester

[0098] The preparation chemical reaction equation is as follows:

[0099] ;

[0100] 0.3 g of the polymer monomer prepared in Example 1, namely compound 12, was dissolved in 1 mL of DMF, followed by the addition of 4 mL of phenyl ether and 0.06 g of alkaline protease and the mixture was heated to 85 °C. o C, stirred for 12 hours under nitrogen protection, and then vacuumed to 200 mbar for 16 hours. After adding 0.06 g of alkaline protease, the reaction was continued at 10 mbar for 72 hours. After the reaction, it was cooled to room temperature, 2 mL of DMF was added to dissolve the product, and the enzyme was filtered out. The filtrate was dripped into a cold ethyl acetate solution (4 oC) was precipitated, filtered and dried to obtain the corresponding side chain base polyester amide, 0.23 g, with a yield of 83%. GPC results showed that the molecular weight of the obtained side chain base polyester amide was 28.2×10 3 g / mol.

[0101] The yield of the polyester amide product in the embodiment of the present invention is calculated as follows:

[0102] Yield = (actual mass of polyester amide product / theoretical mass of polyester amide product) × 100%;

[0103] The theoretical mass of the polyester amide product = (molecular weight of the polymerized monomer, i.e., compound 12 - molecular weight of methanol) × the amount of the polymerized monomer, i.e., compound 12;

[0104] Subsequent yields are calculated using this method, the same below.

[0105] The alkaline protease in Example 3-4 of the present invention is derived from Bacillus subtilis, has an enzyme activity of 500,000 U / g, and is from Tianjin Xiensi Biochemical Technology Co., Ltd.

[0106] Example 4

[0107] Gather N- Preparation of thymine acetyl-D-aspartate-1-(4-amino-1-butanol)

[0108] The preparation chemical reaction equation is as follows:

[0109] ;

[0110] 0.5 g of the polymer monomer prepared in Example 2, namely compound 12, was dissolved in 1 mL of DMF, followed by the addition of 4 mL of phenyl ether and 0.1 g of alkaline protease and the mixture was heated to 85 °C. o C, stirred for 12 hours under nitrogen protection, and then vacuumed to 200 mbar for 16 hours. After adding 0.1 g of alkaline protease, the reaction was continued at 10 mbar for 72 hours. After the reaction, it was cooled to room temperature, 2 mL of DMF was added to dissolve the product, and the enzyme was filtered out. The filtrate was dripped into a cold ethyl acetate solution (4 o C) was precipitated, filtered, and dried to obtain the corresponding side chain base polyester amide, 0.3 g, with a yield of 66%. GPC results showed that the molecular weight of the obtained side chain base polyester amide was 8.3×10 3 g / mol.

[0111] The polyester amides of Examples 3-4 of the present invention were tested for tensile properties of plastics in accordance with GB / T 1040.1-2018, and the results showed that the daily use conditions of the samples could be met.

[0112] 3. Polyesteramide stereocomplex crystallization process: Example 5

[0113] Stereocomplex crystallization process of polyester amide with glutamic acid as main chain

[0114] 50 mg of poly N-adenine acetyl-L-glutamic acid-1-(6-amino-1-hexanol) ester (molecular weight 28.2×10 3 g / mol) and 50 mg poly-N-thymine acetyl-D-glutamic acid-1-(6-amino-1-hexanol) ester (molecular weight 24.5×10 3 g / mol) were successively dissolved in 0.8 mL DMF. Then the polyester amide solution was slowly dripped into 5 mL cold ethyl acetate or n-hexane (4 o C). Put this solution into 4 o C refrigerator for 24 hours, centrifuge, and discard the supernatant. The solid obtained was dried under vacuum at room temperature and its melting point was characterized by DSC. o C) and poly-N-thymine acetyl-D-glutamic acid-1-(6-amino-1-hexanol) ester (melting point 165 o C) compared to the stereocomplex crystallized stereocomplex melting point of 210 o C. This melting point is 45 higher than that of single-configuration poly N-thymine acetyl-D-glutamic acid-1-(6-amino-1-hexanol) ester o C, 32 higher than the single-configuration poly-N-adenine acetyl-L-glutamic acid-1-(6-amino-1-hexanol) ester o C.

[0115] The poly N-thymine acetyl-D-glutamic acid-1-(6-amino-1-hexanol) ester (molecular weight 24.5×10 3 g / mol) comprises the following two steps: 1) firstly, according to the method described in Example 2, the starting material is D -α-Carboxyl- N 1) replacing the "tert-butyloxycarbonyl-aspartic acid monomethyl ester" with an equal molar amount of D-α-carboxyl-N-tert-butyloxycarbonyl-glutamic acid monomethyl ester, and the other conditions remain unchanged to obtain a polymerized monomer; 2) reacting the prepared polymerized monomer according to the method of Example 4, except that the polymerized monomer is replaced with an equal molar amount, the other conditions remain unchanged to obtain a poly N-thymine acetyl-D-glutamic acid-1-(6-amino-1-hexanol) ester product with a molecular weight of 24.5×10 3 g / mol.

[0116] Example 6

[0117] Stereocomplex crystallization process of polyester amide with aspartic acid as main chain

[0118] 50 mg of the polymer prepared in Example 4 was added N- Thymine acetyl-D-aspartate-1-(4-amino-1-butanol) (molecular weight 8.3×10 3 g / mol) and 50 mg poly N- Adenine acetyl-L-aspartic acid-1-(4-amino-1-butanol) (molecular weight 10.5×10 3 g / mol) mixed and heated to 200 o Then, the molten polymer was cooled to room temperature and placed in 4 o The corresponding stereocomplex was obtained after being stored in a refrigerator at C for 10 days. The melting point of the obtained stereocomplex was characterized by DSC. N- Thymine acetyl-D-aspartic acid-1-(4-amino-1-butanol) (melting point 126 o C) and poly N- Adenine acetyl-L-aspartic acid-1-(4-amino-1-butanol) (melting point 133 o C) compared to the stereocomplex crystallization, the melting point of the stereocomplex is 154 o C. This melting point is higher than that of a single configuration of the polymer N- Thymine acetyl-D-aspartate-1-(4-amino-1-butanol) high 28 o C, compared with single-configuration polymers N- Adenine acetyl-L-aspartic acid-1-(4-amino-1-butanol) high 21 o C.

[0119] Example 6 N- Adenine acetyl-L-aspartic acid-1-(4-amino-1-butanol) (molecular weight 10.5×10 3 g / mol) comprises the following two steps: 1) firstly, according to the method described in Example 1, the starting material is L -α-Carboxyl- N -tert-butyloxycarbonyl-glutamic acid monomethyl ester" is replaced by " L -α-Carboxyl- N -tert-butyloxycarbonyl-aspartic acid monomethyl ester", the other conditions remain unchanged, to obtain a polymerizable monomer; 2) the prepared polymerizable monomer is reacted according to the method of Example 3, except that the polymerizable monomer is replaced by an equimolar amount, the other conditions remain unchanged, to obtain a polymerizable monomer N-Adenine acetyl-L-aspartic acid-1-(4-amino-1-butanol) product, molecular weight 10.5×10 3 g / mol.

[0120] In summary, the side chain base polyester amide provided by the present invention can form a D- / L-layer alternating stereocomposite structure through the specific recognition of the side chain base, thereby achieving the purpose of improving its thermal properties. Compared with the polyester amide with a single configuration, after forming a stereocomposite crystal, the melting point can be increased by up to 45 o C.

[0121] 4. Polyesteramide biodegradation process: Example 7

[0122] Take 30 mg of poly N- Adenine acetyl-L-aspartic acid-1-(4-amino-1-butanol) (molecular weight 10.5×10 3 g / mol) was added to a 50 mL beaker containing an aqueous solution of common pond sludge (dry weight of sludge was 100 g, equivalent to a concentration of 2 g / mL), and then stirred at room temperature for 60 days (300 rpm), filtered, and the filtrate was freeze-dried and the residue was tested for its molecular weight using GPC. The results showed that the molecular weight of the residue was 0.94×10 3 This experiment fully proves that the polyester amide prepared by the present invention has good biodegradability.

Claims

1. A biodegradable polyester amide with side chain base having stereocomplex crystallization properties, characterized in that The main chain of the structure is a dimer repeating unit of glutamic acid and amino alcohol or a dimer repeating unit of aspartic acid and amino alcohol, and the side chain is acylated adenine or acylated thymine. The structural formula is shown in Formula I: ； In the formula, x is 0 or 1, y is 2 or 4; the configuration of the polyester amide is D-configuration or L-configuration; and n is an integer ranging from 20-70.

2. A biodegradable polyester amide with side chain base having stereocomplex crystallization properties as claimed in claim 1, characterized in that Its molecular weight is 8.0×10 3 -30.0×10 3 g / mol.

3. A biodegradable polyester amide with side chain base having stereocomplex crystallization properties as claimed in claim 2, characterized in that Also included is the construction of a stereocomplex of polyesteramide, obtained according to the following crystallization process: Method 1: The D-configuration side chain and the L-configuration side chain of the polyester amide are complementary bases, the side chain of one configuration of the polyester amide is acylated adenine, and the side chain of the other configuration of the polyester amide is acylated thymine. The D-configuration polyester amide and the L-configuration polyester amide are dissolved in DMF at a mass ratio of 1:1, and then the mixture is dropped into ethyl acetate or n-hexane, placed in a refrigerator at 2-5°C, precipitated, centrifuged, and vacuum dried at room temperature to obtain the corresponding stereocomplex; Method 2: The D-configuration side chain and the L-configuration side chain of the polyester amide are complementary bases, wherein the side chain of one configuration of the polyester amide is acylated adenine, and the side chain of the other configuration of the polyester amide is acylated thymine. The D-configuration polyester amide and the L-configuration polyester amide are mixed and melted in a mass ratio of 1:1, cooled to room temperature, and stored in a refrigerator at 2-5°C for 5-20 days to obtain the corresponding stereocomplex.

4. The enzymatic preparation method of a biodegradable polyester amide with side chain base having stereocomplex crystallization performance as claimed in claim 1, characterized in that The steps include: Step 1: α-carboxyl-N-tert-butyloxycarbonyl-glutamic acid monomethyl ester or α-carboxyl-N-tert-butyloxycarbonyl-aspartic acid monomethyl ester as shown in formula 1 is used as a substrate, and the molecular configuration of the substrate is L - or D-configuration, react with pentafluorophenyl trifluoroacetate shown in formula 2 in the presence of DMF as solvent and pyridine as acid-binding agent, and stir overnight at room temperature under nitrogen protection to prepare the compound of formula 3, that is, L - or D-configuration intermediate 1, the reaction formula is as follows: ； Step 2: Using triethylamine as an acid-binding agent, the intermediate 1 obtained in step 1 reacts with the amino alcohol shown in formula 4 in DMF solvent, and the mixture is stirred at room temperature under nitrogen protection for 20-30 hours. After the reaction, the compound of formula 5, i.e., the corresponding intermediate 2, is obtained by post-treatment. The reaction formula is as follows: ； Step 3: The intermediate 2 obtained in step 2 is reacted with trifluoroacetic acid in DCM solvent, and stirred overnight at room temperature under nitrogen protection. After the reaction is completed, the solvent is removed by concentration under reduced pressure to obtain a crude product, and the crude product is purified by column chromatography to obtain a compound of formula 6, namely, intermediate 3; ； Step 4: Adenine acetic acid shown in Formula 7 or thymine acetic acid shown in Formula 8 is used as a starting material, and reacts with pentafluorophenyl trifluoroacetate shown in Formula 9 under the conditions of DMF as a solvent and pyridine as an acid-binding agent to prepare pentafluorophenyl adenine acetic acid shown in Formula 10 or pentafluorophenyl thymine acetic acid shown in Formula 11. The compound of Formula 10 or the compound of Formula 11 is marked as intermediate 4. The reaction formula is as follows: ； Step 5: Using triethylamine as an acid-binding agent, the intermediate 3 obtained in step 3 and the intermediate 4 obtained in step 4 are reacted in DMF solvent, and stirred at room temperature for 20-30 hours under nitrogen protection. After the reaction, the compound of formula 12, i.e., the corresponding polymerization monomer, is obtained by post-treatment, and its structural formula is as follows: ； Step 6: alkaline protease is added in two parts. The polymerizable monomer prepared in step 5 is added to a DMF-phenyl ether mixed solvent, and the first part of alkaline protease is added, heated to 75-90° C., stirred for 10-15 hours under nitrogen protection, and then reduced to 100-300 mbar for reaction for 12-20 hours, and then the second part of alkaline protease is added, and the reaction is continued at 5-20 mbar for 60-80 hours. After the reaction is completed, the target product shown in formula I is obtained by post-treatment; Wherein, the definitions of x and y in Formula 1, Formula 3-6 and Formula 12 are the same as those in Formula I.

5. The enzymatic preparation method of a biodegradable polyester amide with side chain base having stereocomplex crystallization properties as claimed in claim 4, characterized in that In step 1, the molar ratio of the compound of formula 2 to the compound of formula 1 is 1.2-1.5:1, and the molar ratio of pyridine to the compound of formula 1 is 1.5-2:

1. After the reaction in step 1 is completed, the following post-treatment step is also included: adding water to quench the reaction, extracting the reaction solution with ethyl acetate, combining the organic phases, drying with anhydrous magnesium sulfate, and concentrating under reduced pressure to obtain a crude product, and the crude product is purified by column chromatography, and the eluent is a mixed solution of ethyl acetate / petroleum ether with a volume ratio of 1:3-8.

6. The enzymatic preparation method of a biodegradable polyester amide with side chain base having stereocomplex crystallization performance as claimed in claim 4, characterized in that In step 2, the molar ratio of intermediate 1 to the compound of formula 4 is 1:1.5-2.

5. After the reaction in step 2 is completed, the following post-treatment steps are also included: adding water to quench the reaction, extracting the reaction solution with ethyl acetate, combining the organic phases, drying with anhydrous magnesium sulfate, and concentrating under reduced pressure to obtain a crude product. The crude product is purified by column chromatography, and the eluent is a mixed solution of ethyl acetate / petroleum ether in a volume ratio of 1:2-5.

7. The enzymatic preparation method of a biodegradable polyester amide with side chain base having stereocomplex crystallization properties as claimed in claim 4, characterized in that In step 3, the molar ratio of intermediate 2 to trifluoroacetic acid is 1:3-8, and the eluent for column chromatography purification in step 3 is a mixed solution of ethyl acetate / petroleum ether in a volume ratio of 1:2-5.

8. The enzymatic preparation method of a biodegradable polyester amide with side chain base having stereocomplex crystallization properties as claimed in claim 4, characterized in that In step 4, the molar ratio of adenine acetic acid shown in formula 7 or thymine acetic acid shown in formula 8 to pentafluorophenyl trifluoroacetate is 1:1.2-1.

5. After the reaction in step 4 is completed, the following post-treatment step is also included: adding water to quench the reaction, extracting the reaction solution with ethyl acetate, combining the organic phases, drying with anhydrous magnesium sulfate, and concentrating under reduced pressure to obtain a crude product, and the crude product is purified by column chromatography, and the eluent is a mixed solution of ethyl acetate / petroleum ether with a volume ratio of 1:3-8.

9. The enzymatic preparation method of a biodegradable polyester amide with side chain base having stereocomplex crystallization properties as claimed in claim 4, characterized in that In step 5, the molar ratio of intermediate 3 to intermediate 4 is 1:1.5-2.

5. After the reaction in step 5 is completed, the following post-treatment steps are also included: adding water to quench the reaction, extracting the reaction solution with ethyl acetate, combining the organic phases, drying with anhydrous magnesium sulfate, and concentrating under reduced pressure to obtain a crude product. The crude product is purified by column chromatography, and the eluent is a mixed solution of ethyl acetate / petroleum ether in a volume ratio of 1:2-5.

10. The enzymatic preparation method of a biodegradable polyester amide with side chain base having stereocomplex crystallization properties as claimed in claim 4, characterized in that In step 6, the volume ratio of DMF-phenyl ether is 1:3-5, the alkaline protease is alkaline protease derived from Bacillus subtilis, the mass ratio of the first part and the second part of the alkaline protease is 0.8-1.2:1, and when the enzyme activity of the alkaline protease is 500,000 U / g, the total mass of the two parts of the alkaline protease is 30-40% of the mass of the polymerized monomer; the post-treatment steps after the reaction in step 6 are: cooling to room temperature, adding DMF to dissolve the product, filtering to remove the enzyme, dripping the filtrate into an ethyl acetate solution at 2-5°C to precipitate, filtering, and drying to obtain the target product.

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