Method for simply and conveniently synthesizing 5-O-(beta-D-glucopyranosyl) gentisic acid

Abstract

The invention provides a method for simply and conveniently synthesizing 5-O-(beta-D-glucopyranosyl) gentisic acid. According to the method, gentisic acid is taken as an initial raw material, and 5-O-(beta-D-glucopyranosyl) gentisic acid is simply prepared through four-step reaction (esterification reaction with tert-butyl alcohol, lewis acid catalyzed high-selectivity glycosylation reaction, trifluoroacetic acid mediated tert-butyl removal reaction and sodium methoxide catalyzed deacetylation reaction). The synthesized target product has the effects of reducing the in-vivo oestrone level and inhibiting the growth of tumor cells and mycobacterium ulcers, and is expected to be applied to the treatment of Briele ulcers. The synthesis method provided by the invention has the advantages of simple steps, mild reaction conditions and high synthesis efficiency, and has positive effects in the fields of biological medicines, medicine synthesis and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic synthesis, and particularly relates to a method for simply synthesizing 5-O-(β-D-glucopyranosyl)gentisic acid. Background Art

[0002] 5-O-(β-D-glucopyranosyl)gentisic acid (CAS registration number 1820-89-9) is an important bioactive substance. As an aromatase inhibitor, it can reduce the level of estrone in the body, thereby inhibiting the growth of tumor cells (Y. Zhang, Y. He, C. Liu, C. Liu, S. Li, J. Sep. Sci. 2018, 41, 483-492). Additionally, as a cystathionine γ-synthase inhibitor, it can inhibit the growth of Mycobacterium ulcerans and is expected to be applied to the treatment of Buruli ulcer (S. K. Kwofie, N. N. O. Dolling, E. Donkoh, G. M. Laryea, L. Mosi, W. A. Miller, M. B. Adinortey, M. D. Wilson, Computation 2021, 9, 32). So far, more than 60 literatures have reported the biological activities of 5-O-(β-D-glucopyranosyl)gentisic acid. However, 5-O-(β-D-glucopyranosyl)gentisic acid mainly relies on extraction from plants. So far, only two literatures have reported its chemical synthesis (G. Wagner, Arch. Pharm. Ber. Dtsch. Pharm. Ges. 1958, 291, 278; Uhrig, R. K. Picard, M. A. Beyreuther, K. Wiessler, M. Carbohyd. Res. 2000, 325, 72-80).

[0003] As shown in Reaction Scheme 1, both synthesis methods use the raw material methyl 2-O-acetylgentisate (Formula 4). The synthesis of this raw material undergoes three steps: (1) Diacetylation of gentisic acid (Formula 1) to obtain diacetylgentisic acid (Formula 2); (2) Selectively removing the 5-O-acetyl group using ammonia to obtain 2-O-acetylgentisic acid (Formula 3); (3) Methylating with highly toxic diazomethane to obtain methyl 2-O-acetylgentisate (Formula 4).

[0004] In the Wagner synthesis method (G. Wagner, Arch. Pharm. Ber. Dtsch. Pharm. Ges. 1958, 291, 278), methyl 2-O-acetylgentisate (Formula 4) reacts with tetraacetyl bromo-β-D-glucopyranose (Formula 5) under Ag 2 O-quinoline conditions to form the intermediate shown in Formula 6. Subsequently, through deacetylation catalyzed by sodium methoxide, hydrolysis of the ester group with Ba(OH) 2 and recrystallization, the target product 5-O-(β-D-glucopyranosyl)gentisic acid shown in Formula 7 is obtained.

[0005] In the Wiessler synthesis method (Uhrig, R. K. Picard, M. A. Beyreuther, K. Wiessler, M. Carbohyd. Res. 2000, 325, 72 - 80), methyl 2-O-acetylgentisate (Formula 4) reacts with tetrabenzyl β-D-glucopyranoside trichloroacetimidate (Formula 5) under BF 3 ·OEt 2 conditions to form the intermediate shown in Formula 9. Subsequently, through deacetylation catalyzed by sodium methoxide, hydrolysis of the ester group with KOH - Ba(OH) 2 and debenzylation with H 2 -Pd / C, the target product 5-O-(β-D-glucopyranosyl)gentisic acid shown in Formula 7 is finally obtained.

[0006]

[0007] The above synthesis methods have disadvantages such as cumbersome steps (both synthesis methods have a total of 7 reaction steps), use of precious metal reagents or catalysts (Ag 2 O is used in the Wagner synthesis method, and Pd is used in the Wiessler synthesis method), long reaction time, and low synthesis efficiency, which are not conducive to the large-scale preparation of 5-O-(β-D-glucopyranosyl)gentisic acid. To address the above problems, the present invention aims to provide a simple and efficient method for synthesizing 5-O-(β-D-glucopyranosyl)gentisic acid. Summary of the Invention

[0008] As shown in Reaction Formula 2, the present invention uses gentisic acid shown in Formula 1 as the starting material and undergoes four reaction steps to prepare the target product 5-O-(β-D-glucopyranosyl)gentisic acid shown in Formula 7. The raw materials and reagents used in the present invention can be directly purchased.

[0009] The technical solution of the present invention is as follows:

[0010] Step 1: Using gentisic acid shown in Formula 1 as the raw material, reacting with tert-butanol ( tEsterification reaction occurs with tert-butanol (BuOH) to synthesize tert-butyl gentisate (Formula 10).

[0011] Step 2: tert-Butyl gentisate (Formula 10) reacts with tetra-O-acetyl-β-D-glucopyranosyl trichloroacetimidate (Formula 11) under the catalysis of boron trifluoride diethyl etherate (BF 3 ·OEt 2 ) or trimethylsilyl trifluoromethanesulfonate (TMSOTf) to generate 5-O-(tetra-O-acetyl-β-D-glucopyranosyl) tert-butyl gentisate shown in Formula 12.

[0012] Step 3: The intermediate shown in Formula 12 removes the tert-butyl group in a 1,4-dioxane solution of trifluoroacetic acid or hydrogen chloride to generate the intermediate 5-O-(tetra-O-acetyl-β-D-glucopyranosyl) gentisic acid shown in Formula 13.

[0013] Step 4: The intermediate shown in Formula 13 removes the acetyl group under the catalysis of sodium methoxide and is treated with acidic DOWEX cation exchange resin to generate the target product 5-O-(β-D-glucopyranosyl) gentisic acid shown in Formula 7.

[0014]

[0015] In the above preparation method, in Step 1, the esterification reaction occurs under the action of carbonyldiimidazole (CDI), and 1,8-diazabicyclo[5.4.0]undec-7-ene, a strong base, needs to be added to the reaction system.

[0016] In the above preparation method, in Step 2, the commonly used solvents are ethyl acetate, acetonitrile, chloroform, dichloromethane, 1,2-dichloroethane, ether, tetrahydrofuran, 1,4-dioxane, toluene, chlorobenzene or their mixtures, and the preferred solvent is dichloromethane.

[0017] In the above preparation method, in Step 2, the amount of tetra-O-acetylglucosyl trichloroacetimidate is 1 - 10 molar equivalents, preferably 1.5 molar equivalents, relative to tert-butyl gentisate. The amount of Lewis acid catalyst is 0.1 - 10 molar equivalents relative to tert-butyl gentisate.

[0018] In the above preparation method, in Step 3, using trifluoroacetic acid as the acid and dichloromethane as the solvent, heat under reflux. Among them, the amount of trifluoroacetic acid is 4 - 50 molar equivalents.

[0019] In the above preparation method, Step 4 is synthesized by a one-pot method, which is specifically divided into two operations: first remove the acetyl group in a methanol solution of sodium methoxide, and then add acidic DOWEX cation exchange resin. The separation method is recrystallization. Among them, the amount of sodium methoxide is 0.1 - 20 molar equivalents, and the amount of DOWEX cation exchange resin is 1 - 100 mass equivalents.

[0020] Advantages and positive effects of the present invention:

[0021] 5-O-(β-D-glucopyranosyl)gentisic acid prepared by the present invention is an important bioactive substance. As an aromatase inhibitor, it can inhibit the growth of tumor cells; as a cystathionine γ-synthase inhibitor, it can inhibit the growth of mycobacteria. The synthesis method provided by the present invention has a short route, high synthesis efficiency, simple operation, is suitable for large-scale preparation, and has high application value. Specific embodiments

[0022] The present invention will be further described below by way of examples, and the present invention is not limited to the scope of the examples.

[0023] Step 1

[0024] Synthesis of tert-butyl gentisate

[0025] Dissolve gentisic acid (3.00 g, 19.5 mmol) and carbonyldiimidazole (3.16 g, 19.5 mmol) in 20 mL of dry DMF, and heat at 40 °C for 1 h. Subsequently, add tert-butanol (3.73 mL, 39 mmol) and DBU (2.91 mL, 19.5 mmol), and continue stirring at 40 °C for 24 h. Cool to room temperature, add 200 mL of water, and extract with ethyl acetate. The extract is dried over anhydrous sodium sulfate, concentrated, and separated by column chromatography to obtain tert-butyl gentisate (2.12 g, yield 52%).

[0026] Light yellow solid, melting point 79 - 81 °C, R f = 0.3 (PE / EtOAc = 2:1, v / v). 1 1H NMR (CDCl 3 , 400 MHz) 10.72 (s, 1H), 7.29 (d, J = 3.2 Hz), 7.01 (dd, J = 3.2, 8.8 Hz, 1H), 6.89 (d, J = 8.8 Hz, 1H), 5.43 (s, 1H), 1.64 (s, 9H).

[0027] Step 2 Synthesis of tert-butyl 5-O-(tetraacetyl-β-D-glucoside)gentisate

[0028] Add tetraacetylpyranosyl trichloroacetimidate (11,476 mg, 1 mmol), tert-butyl gentisate (316 mg, 1.5 mmol) to a 50-mL round-bottom flask, and Molecular sieve. Under nitrogen protection, dry dichloromethane (20 mL) and TMSOTf (5.4 μL, 0.03 mmol) were added. Stir for 1 h under an ice-water bath, and quench with triethylamine (1 mL). Column chromatography separation gave tert-butyl 5-O-(tetraacetyl-β-D-glucopyranosyl)gentisate (432 mg, 80%).

[0029] Following the same procedure, using boron trifluoride diethyl etherate as the catalyst (1 mmol), 398 mg of the product was obtained with a yield of 74%.

[0030] White solid, melting point 108 - 110 °C, R f = 0.1 (PE / EA = 5:1, v / v). 1 1H NMR (400 MHz, CDCl 3 ) δ 10.73 (s, 1H), 7.38 (d, J = 3.0 Hz, 1H), 7.13 (dd, J = 9.0, 3.1 Hz, 1H), 6.88 (d, J = 9.0 Hz, 1H), 5.32–5.20 (m, 2H), 5.17 (t, J = 9.5 Hz, 1H), 4.95 (d, J = 7.6 Hz, 1H), 4.32 (dd, J = 12.3, 4.8 Hz, 1H), 4.14 (dd, J = 12.3, 2.5 Hz, 1H), 3.79 (ddd, J = 9.9, 4.8, 2.5 Hz, 1H), 2.08 (s, 3H), 2.07 (s, 3H), 2.04 (s, 3H), 2.03 (s, 3H), 1.60 (s, 9H). 13 13C NMR (101 MHz, CDCl 3 ) δ 170.5, 170.2, 169.3, 169.3, 169.0, 158.1, 148.8, 125.8, 118.6, 118.4, 113.8, 100.4, 83.3, 72.7, 72.0, 71.2, 68.2, 61.7, 28.2, 20.7, 20.7, 20.6, 20.6. LC-MS (ESI): m / z calcd for: C 25 H 33 O 13 + [M + H] + : 541.1916, found: 541.1915.

[0031] Step 3:

[0032] Synthesis of 5-O-(tetraacetyl-β-D-glucopyranosyl)gentisic acid

[0033] To a 50-mL round-bottom flask were successively added tert-butyl 5-O-(tetraacetyl-β-D-glucopyranosyl)gentisate (475 mg, 0.88 mmol), dry CH 2 Cl 2 (12 mL), trifluoroacetic acid (1.3 mL, 20 equiv.), and the mixture was refluxed until the starting material was completely consumed. Dichloromethane and trifluoroacetic acid were removed under vacuum, and the residue was recrystallized from ethyl acetate and petroleum ether to give 5-O-(tetraacetyl-β-D-glucopyranosyl)gentisic acid (316 mg, 74%).

[0034] White solid, melting point 120 - 123 °C, R f f = 0.6 (EA / HCOOH = 30:1, v / v). 1 H NMR (400 MHz, CDCl 3 ) 10.24 (s, 1H), 8.91 (s, 1H), 7.52 (d, J = 3.0 Hz, 1H), 7.20 (dd, J = 9.1, 3.0 Hz, 1H), 6.93 (d, J = 9.1 Hz, 1H), 5.34–5.21 (m, 2H), 5.15 (t, J = 9.5 Hz, 1H), 4.99 (d, J = 7.5 Hz, 1H), 4.27 (dd, J = 12.3, 5.3 Hz, 1H), 4.19 (dd, J = 12.3, 2.4 Hz, 1H), 3.86 (ddd, J = 10.0, 5.4, 2.4 Hz, 1H), 2.09 (s, 3H), 2.08 (s, 3H), 2.04 (s, 3H), 2.03 (s, 3H). 13 C NMR (101 MHz, CDCl 3 ) δ 173.3, 171.0, 170.4, 169.6, 169.5, 158.5, 149.1, 127.7, 118.9, 118.0, 111.2, 100.1, 72.7, 72.1, 71.2, 68.3, 62.1, 20.7, 20.61, 20.60. LC-HRMS (ESI): m / z calcd for: C 21 H 25 O 13 + [M + H] + : 485.1290, found: 485.1286.

[0035] Step 4 Synthesis of 5-O-(β-D-glucopyranosyl)gentisic acid

[0036] Sodium methoxide (105 mg, 1.95 mmol) was added to a suspension of 5-O-(tetraacetyl-β-D-glucopyranosyl)gentisic acid (316 mg, 0.65 mmol) in methanol (5 mL) at 0 °C. After the addition was complete, the mixture was stirred at room temperature for 1 h to obtain a clear solution. Cation exchange resin DOWEX-50WX4-200 was added to the solution until the pH value of the reaction system was 3 - 4. The mixture was filtered and the filtrate was concentrated to obtain a crude product. The crude product was recrystallized from ethyl acetate to obtain 5-O-(β-D-glucopyranosyl)gentisic acid product (124 mg, 60% yield).

[0037] White solid, melting point 97 - 100 °C, R f f = 0.3 (EA / HCOOH = 30:1, v / v). 1 1H NMR (400 MHz, D 2 2O) δ 7.49–7.44 (m, 1H), 7.26–7.20 (m, 1H), 6.88–6.82 (m, 1H), 4.95–4.90 (m, 1H), 3.94–3.89 (m, 1H), 3.73 (dd, J = 12.5, 5.8 Hz, 1H), 3.62–3.42 (m, 4H). 13 13C NMR (101 MHz, CDCl 3 3) δ 171.7, 155.7, 149.2, 125.7, 118.0, 117.6, 112.9, 101.3, 76.1, 75.5, 72.9, 69.4, 60.5. LC-MS (ESI): m / z calcd for C 13 13H 17 20O 9 + [M + H] + : 317.0867, found: 317.0865.

Claims

1. A method for simply synthesizing 5-O-(β-D-pyranoglucopyranosyl) gentisic acid, characterized in that: Using the gentisic acid shown in Formula 1 as a raw material, 5-O-(β-D-pyranose glucopyranosyl) gentisic acid shown in Formula 7 is simply prepared by undergoing an esterification reaction with tert-butyl alcohol (step 1), a highly selective glycosidation reaction (step 2), a de-tert-butylation reaction (step 3), and a sodium methoxide-catalyzed deacetylation reaction (step 4).

2. The method according to claim 1, characterized in that The tert-butyl gentisate (Formula 10) in step 1 is used as the key intermediate.

3. The method according to claim 1, characterized in that In step 2, tetraacetyl-β-D-pyranose glucopyranosyl trichloroacetimidate (Formula 11) reacts with tert-butyl gentisate in the presence of boron trifluoride·ethyl ether or trimethylsilyl trifluoromethanesulfonate to generate 5-O-(tetraacetyl-β-D-pyranose glucopyranosyl) tert-butyl gentisate (Formula 12).

4. The method according to claim 1, characterized in that: In step 2, the solvent used is ethyl acetate, acetonitrile, chloroform, dichloromethane, 1,2-dichloroethane, ether, tetrahydrofuran, 1,4-dioxane, toluene, chlorobenzene or a mixture thereof, preferably ethyl acetate and dichloromethane.

5. The method according to claim 1, characterized in that In step 3, the reagent used is trifluoroacetic acid.

6. The method according to claim 1, characterized in that In step 4, after the acetyl group is removed, the reaction system needs to be treated with an acidic cation exchange resin.

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