JP6358877B2 - Method for producing liquiritigenin precursor - Google Patents

Description

The present invention relates to a process for producing isoliquiritigenin as a precursor of licorice liquiritigenin.

Licorice liquiritigenin is an excellent herbal medicine with widely recognized medicinal effects, and is generally extracted from licorice. However, the extraction method requires extraction of the liquoritigenin by reverse phase chromatography after removing saccharide parts (glucose and abiose) after hydrolysis after extracting licorice root with heat. Therefore, extraction of licorice from licorice is expensive and valuable, and it is sold at over 10,000 yuan per gram. In addition, licorice is declining because it is difficult to cultivate licorice.

There is an attempt to artificially synthesize licorice liquiritigenin. As shown in FIG. 2, the first method is a method in which p-hydroxybenzaldehyde is used as a starting material, and 4-carboxycinnamic acid is synthesized, and 1,3-dihydroxybenzene is added via this to isomerize. Although it is a method for obtaining lithigenin (Non-patent Document 1), there is a disadvantage that the yield is low. Therefore, as a second method, as shown in FIG. 3, p-hydroxybenzaldehyde is used as a starting material and the hydroxyl group at the p-position is protected with a MOM reagent, while the hydroxyl group of 1,3-dihydroxybenzene is protected with a MOM reagent. A method of adding both is proposed (Non-Patent Document 2). However, when actually verified, purification steps by column chromatography are required in almost all stages (yield, product is oily, etc.). Moreover, in our follow-up experiment, the yield of the coupling process when scaled up decreased to 42%, and in addition, the ring-closing reaction from isoliquiritigenin to liquiritigenin in the final process brought the equilibrium between the raw material and the target product. As a result, the yield was not increased. In addition, it was difficult to separate the raw material and the target product at the ring closure stage, and liquiritigenin tailed under the final chromatographic purification conditions, resulting in a significant reduction in recovery. In addition, two extra steps are required for the carcinogenicity of the MOM protecting reagent, and further protection and deprotection, and the second method was effective at the laboratory level, but it was found that it was not suitable for mass production.

Pharmacological Journal Acta Pharmaceutica Sinica 1994,29 (11): 877-880 Hu etc. European Journal of Medical Chemistry, 45,3453-3458

  Therefore, the present inventors selected a method for crystallization without using a chromatograph in the method for mass production of liquiritigenin, and without using a carcinogenic MOM protecting reagent, and further artificially isolyquiritigenin into liquiritigenin. In consideration of the fact that the yield does not increase with the equilibrium reaction when converted to, the organically synthesized liquiritigenin coexists with the (+) and (-) isomers, and requires a new toxicity test. The purpose of this study is to provide an appropriate method for mass production of liquiritigenin.

  The inventors of the present invention organically synthetically convert isoliquiritigenin to liquiritigenin, and unlike the natural product, the (+) body and the (−) body coexist, but when administered to a human body, (−) Focusing on the possibility of being converted to liquiritigenin in the body, it does not synthesize liquiritigenin, synthesizes its precursor isoliquiritigenin, administers it to the human body, and attempts to convert it to the target liquiritigenin in the body In the production of isoliquiritigenin, p-alkoxycinnamic acid is used as a starting material, and p-alkoxybenzene is coupled to this using the Feidelcraft reaction to form trialkoxyisolithicigenin in a high yield. Thus, a method suitable for mass production of isoliquiritigenin by crystallization and deprotection is provided. This isoliquiritigenin may be converted to liquiritigenin by in vivo conversion, and the pharmacological effect of liquiritigenin (−) form can be obtained in the body.

As shown in FIG. 1, the reaction formula of the present invention comprises a coupling reaction (A), and the formula (i
) -P-alkoxycinnamic acid represented by formula (ii) and 1,3-dialkoxybenzene represented by formula (ii) to synthesize trialkoxyisolithicigenin represented by formula (iii), and the protective group is removed to remove The method synthesizes lithigenin. In formulas (i), (ii) and (iii), R is preferably an alkoxy group in which R is methyl, ethyl or butyl, and a methoxy group in which R is methyl is usually available. . The reaction is halogenated by adding a halogenating agent to p-alkoxycinnamic acid represented by formula (i), to which p-alkoxybenzene represented by formula (ii) is added, and then a catalyst (metal halide, For example, trialkoxycinnamic acid represented by the formula (iiia) is obtained by electrophilic substitution with hydrogen of a predetermined aromatic ring in the presence of aluminum chloride or the like. Secondly, in the reaction formula (B), when the protective device is removed, the target isoliquiritigenin represented by the formula (iv) is obtained. Isoliquiritigenin is converted to liquiritigenin represented by formula (v) by ring-closure reaction (C), but in organic synthesis, (+) and (−) isomers are converted. Therefore, it is necessary to separate the two by chiral resolution if necessary. Therefore, liquiritigenin obtained from licorice is a (−) isomer. Therefore, by using the isomerase enzyme of isoliquiritigenin, the liquiritigenin (−) isomer is obtained, or the enzyme is administered when isoliquiritigenin is administered to the human body. A (−) body of Kirichigenin can also be obtained in the body tissue by the reaction. As p-alkoxycinnamic acid, p-methoxycinnamic acid is preferable, but p-ethoxycinnamic acid and p-butoxy cinnamic acid may be used. In the following Examples, specifically, p-methoxycinnamic acid represented by the formula (ia) and 1,3-dimethoxybenzene represented by the formula (iia) are used to obtain trimethoxyisolithici represented by the formula (iiia). There is a method for synthesizing isoliquiritigenin by synthesizing genin and removing the protecting group.

It is a reaction diagram which shows the 1st reaction (A), the 2nd reaction (B), and the 3rd reaction (C) which show the manufacture example of isoliquiritigenin concerning this invention. It is a reaction diagram which shows the manufacture example of the conventional 1st method liquiritigenin. It is a reaction diagram which shows the manufacture example of the liquiritigenin of the conventional 2nd method. Hereinafter, preferred specific examples of the present invention will be described based on examples. Example 1

4-メトキシケイヒ酸 式(ia）10ｇをジメチルホルムアミド0.25 mLを含む無水塩化メチレン50 mLに溶解し，室温にてオキザリルクロリド9.6 mLを発泡に注意しながら10分かけて滴下した。そのまま，室温にて2時間撹拌の後，溶媒を減圧下で除去した。得られた残渣に，1，3-ジメトキシベンゼン7.4 mL（式iiａ）と無水エーテル200 mLを加え，氷浴中で，粉末にした触媒無水三塩化アルミニュウム22.4 gを15分かけてゆっくりと加えた。そのまま室温にて一晩放置した後，内容物を氷上(500 g)にあけ，６M 塩酸を10 mL加え，氷が溶解した後，酢酸エチル(300 mL)で4回抽出した。抽出液を無水硫酸ナトリウムで乾燥後，減圧下で濃縮し，残渣をエーテル-ヘキサン混液で結晶化することにより，14.2 gの目的物(式iiia)の結晶を得た。
収率85% ¹H-NMR (CDCl₃) δ 7.73 (1H, d, J=8.1 Hz), 7.64 (1H, d, J=15.1 Hz), 7.54 (2H, d, J=7.7 Hz), 7.38 (1H, d, J=15.1 Hz), 6.90 (2H, d, J=7.7 Hz), 6.55 (1H, brd, J=8.1 Hz), 6.49 (1H, brs), 3.89 (3H, s), 3.85 (3H, s), 3.83 (3H, s).

4-methoxycinnamic acid 10 g of formula (ia) was dissolved in 50 mL of anhydrous methylene chloride containing 0.25 mL of dimethylformamide, and 9.6 mL of oxalyl chloride was added dropwise at room temperature over 10 minutes while paying attention to foaming. After stirring for 2 hours at room temperature, the solvent was removed under reduced pressure. To the obtained residue, 7.4 mL of 1,3-dimethoxybenzene (formula iia) and 200 mL of anhydrous ether were added, and 22.4 g of powdered catalyst anhydrous aluminum trichloride was slowly added over 15 minutes in an ice bath. . The mixture was allowed to stand at room temperature overnight, then the contents were poured on ice (500 g), 10 mL of 6M hydrochloric acid was added, and the ice was dissolved, followed by extraction four times with ethyl acetate (300 mL). The extract was dried over anhydrous sodium sulfate, concentrated under reduced pressure, and the residue was crystallized from an ether-hexane mixture to obtain 14.2 g of the desired product (formula iiia).
Yield 85% ¹ H-NMR (CDCl ₃ ) δ 7.73 (1H, d, J = 8.1 Hz), 7.64 (1H, d, J = 15.1 Hz), 7.54 (2H, d, J = 7.7 Hz), 7.38 (1H, d, J = 15.1 Hz), 6.90 (2H, d, J = 7.7 Hz), 6.55 (1H, brd, J = 8.1 Hz), 6.49 (1H, brs), 3.89 (3H, s), 3.85 (3H, s), 3.83 (3H, s).

上記生成物(式iiia)3 gを塩化メチレン60 mLに溶解し0 ℃にて1 M BBr₃塩化メチレン溶液を滴下した。室温まで昇温し，そのまま2日間撹拌した。セニエット塩34 gを含む氷冷水700 mLとメタノール350 mLを加え，室温で一晩撹拌した。得られた黄色溶液を酢酸エチルで2回抽出し，1 Mセニエット塩-飽和食塩水で洗浄後，無水硫酸ナトリウムで乾燥，濃縮した。残渣をエーテル-ヘキサンで結晶化し，目的物(式iv)1.95 gを得た。またその母液を濃縮後再度エーテル-ヘキサンで結晶化することにより0.59 gの目的物第２晶を得た。
合計収率98%¹H-NMR (acetone-d₆) δ 13.5 (1H, s), 8.10 (1H, d, J=8.3 Hz), 7.82 (1H, d, J=15.4 Hz), 7.74 (1H, d, J=15.4 Hz), 7.72 (2H, d, J=8.2 Hz), 6.90 (2H, d, J=8.2 Hz), 6.44 (1H, dd, J=8.3 and 1.7 Hz), 6.34 (1H, d, J=1.7 Hz).

（実施例２）

3 g of the above product (formula iiia) was dissolved in 60 mL of methylene chloride, and 1 M BBr ₃ methylene chloride solution was added dropwise at 0 ° C. The mixture was warmed to room temperature and stirred for 2 days. Ice-cooled water (700 mL) containing 34 g of Sennet salt and methanol (350 mL) were added, and the mixture was stirred overnight at room temperature. The resulting yellow solution was extracted twice with ethyl acetate, washed with 1 M seniette-saturated brine, dried over anhydrous sodium sulfate and concentrated. The residue was crystallized from ether-hexane to obtain 1.95 g of the desired product (formula iv). The mother liquor was concentrated and recrystallized from ether-hexane to obtain 0.59 g of the second crystal of the desired product.
Total yield 98% ¹ H-NMR (acetone-d ₆ ) δ 13.5 (1H, s), 8.10 (1H, d, J = 8.3 Hz), 7.82 (1H, d, J = 15.4 Hz), 7.74 (1H , d, J = 15.4 Hz), 7.72 (2H, d, J = 8.2 Hz), 6.90 (2H, d, J = 8.2 Hz), 6.44 (1H, dd, J = 8.3 and 1.7 Hz), 6.34 (1H , d, J = 1.7 Hz).

(Example 2)

原料200 mg（式iv）に海砂3 gを加え，撹拌し，よく分散した後に，水20 mLを加えた。その懸濁液にピロリジン合計200 μLを三回に分け，1日1回加え，3日間撹拌した。海砂をろ過除去し，ろ液を１M HCｌに加え，残渣を少量のメタノールに溶かし，それらを併せて酢酸エチルで3回抽出した。抽出液を無水硫酸ナトリウムで乾燥後，濃縮し，エーテルで結晶化することによりリキリチゲニンの粗結晶96 mgを得た（式v）。
収率48%.
1H-NMR (DMSO-d₆) δ 9.65 (1H, brs), 7.58 (1H, m), 7.27 (2H, m), 6.74 (2H, m), 6.45 (1H, m), 6.28 (1H, m), 5.39 (1H, brd, J=11.6 Hz), 3.65 (1H, brt, J=15.0 Hz), 2.58 (1H, brd, J=15.7 Hz).

To 200 mg (formula iv) of raw material, 3 g of sea sand was added, stirred and well dispersed, and then 20 mL of water was added. To the suspension, a total of 200 μL of pyrrolidine was divided into three times, added once a day, and stirred for 3 days. The sea sand was removed by filtration, the filtrate was added to 1M HCl, the residue was dissolved in a small amount of methanol, and they were combined and extracted three times with ethyl acetate. The extract was dried over anhydrous sodium sulfate, concentrated, and crystallized with ether to obtain 96 mg of liquiritigenin crude crystals (formula v).
Yield 48%.
1H-NMR (DMSO-d ₆ ) δ 9.65 (1H, brs), 7.58 (1H, m), 7.27 (2H, m), 6.74 (2H, m), 6.45 (1H, m), 6.28 (1H, m ), 5.39 (1H, brd, J = 11.6 Hz), 3.65 (1H, brt, J = 15.0 Hz), 2.58 (1H, brd, J = 15.7 Hz).

Claims (4)

Trialkoxy represented by the formula (III) by coupling 4-alkoxycinnamic acid represented by the formula (I) and 1,3-alkoxybenzene represented by the formula (II) by Friedel- Craft reaction (A). A method for producing isoliquiritigenin, comprising synthesizing and crystallizing isoliquiritigenin, and removing the protecting group in reaction (B) to obtain isoliquiritigenin represented by formula (IV).
However, in formula (I), formula (II), and formula (III), R is methoxy, ethoxy, or butoxy.

As a reagent for reaction (A) of claim 1 (COCl) ₂ And AlCl ₃ As a reagent for reaction (B), BBr ₃ The method according to claim 1, wherein The isoliquiritigenin according to claim 2 , wherein the compound of formula (Ia), (IIa) or (IIIa) is used in formula (I), (II) and (III), wherein R of protecting group RO is a methyl group. Manufacturing method.

The method according to claim 3, wherein the isolithicigenin represented by the formula (IV) is cyclized to obtain the liquiritigenin represented by the formula (V).

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