JPS6140230B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is based on the following general formula (In the formula, R ₁ is a lower alkoxy group, and R ₂ is a protecting group for a carboxyl group.) This invention relates to a cis-2,3-epoxy-4-lower alkoxyphenylbutanoic acid derivative represented by the formula: and a method for producing the same. . The compound of the general formula () of the present invention is
3-Amino-2-hydroxy-4-p-hydroxyphenylbutanoic acid (s) described in Publication No. 136118
- It is a useful intermediate for producing 3-amino-2-hydroxy-4-p-hydroxyphenylbutanoic acid, which is the raw material for leucine. Previously, Umezawa et al. cultivated bestatin-producing bacteria belonging to actinomycetes, and from the culture obtained bestatin [(2S,3R)--, which has a strong inhibitory effect on aminopeptidase B, leucine amino-peptidase, and bleomycin hydrolase. 3-Amino-2
-Hydroxy-4-phenylbutanoyl-(s)
- Leucine] () was isolated (for example, in
-Refer to Publication No. 7187). In addition, this bestatin contains (2S,3R)-3-amino-2-hydroxy-4-phenylbutanoic acid and L
-It has been reported that it can be produced synthetically by reacting leucine (Japanese Patent Application Laid-Open No. 136118-1983)
(see publication). Furthermore, this publication describes that 3-amino-2-hydroxy-4-hydroxyphenylbutanoyl-
It has been disclosed that (s)-leucine has similar physiological activity to bestatin. The present inventors focused on the excellent physiological activity of bestatin, and were interested in the production of bestatin green compounds, especially derivatives having a hydroxyl group on the phenyl nucleus of bestatin, by a synthetic method, and DL, an important intermediate thereof. -Threo-3-Amino-2
The present invention was completed as a result of various studies on simple synthetic methods for -hydroxy-4-substituted phenylbutanoic acid. cis- represented by the general formula () of the present invention
The 2,3-epoxy-4-lower alkoxyphenylbutanoic acid derivative is a compound that has not been described in any literature, and is produced by the method shown by the following formula. (In the formula, R ₁ and R ₂ are the same as above.) That is, the first method is to epoxidize the cis-4-lower alkoxyphenyl-2-butenoic acid derivative represented by the general formula (). In the epoxidation reaction used in this method, well-known organic peracids (eg, metachloroperbenzoic acid, trifluoroperacetic acid, etc.) are applied, and the target compound can be obtained in high yield. The reaction temperature and reaction time vary depending on the type of reagent used. There is no need to use any special method to separate and purify the target substance from the reaction mixture after the completion of the reaction, and this can be easily accomplished by well-known means commonly used for such purposes. formula()
The protecting group R for the carboxyl group is represented by the formula ()
When converted to the epoxide compound shown by
Any group may be used as long as the free acid is a necessary group for stably existing the unstable epoxide compound (), and it serves the purpose and does not cause any undesirable reaction with the reagent used. For example, methyl, ethyl , lower alkyl groups such as propyl and butyl, phenyl groups, and benzyl groups. Preferred from a practical standpoint are lower alkyl groups such as methyl and ethyl groups. The alkyl group and phenyl group in these protecting groups may have a substituent that does not inhibit their function as a protecting group. Note that the compound of general formula () is a novel compound that has not been described in any literature, and can be synthesized by the method shown in the following formula. (In the formula, R ₁ and R ₂ are the same as above, and R represents an alkyl group.) That is, substituted phenyl acetic acid chloride () is reacted with Meldrum's acid () to form acylated Meldrum's acid (), which is then subjected to alcoholysis. Then, β-ketoester () is obtained. Then β-
The ketoester is reacted with hydrazine to form a pyrazolone compound (). When this product was reacted with thallium nitrate in alcohol, a tetrolic acid derivative () was obtained, and the compound of the above general formula () was synthesized from this product by a catalytic reduction method using a Lindlar catalyst. The reaction between the compound of general formula () and the compound of general formula () is carried out using an organic base such as pyridine in the presence of an organic solvent. Room temperature is sufficient for the reaction temperature. In the next step, alcoholysis, the alcohol used may be refluxed for about 2 hours at its boiling point. Note that β
-The reaction to obtain tetrolic acid derivative () from ketoester () is Angew.Chem.internat.Edit.
, 11 48 (1972) in high yield. Next, a second method for producing the compound of general formula () will be explained. The second production method involves converting the trans-4-lower alkoxyphenyl-2-butenoic acid derivative represented by the general formula () into a 2,3-
It is a dihydroxy-4-lower alkoxyphenylbutanoic acid derivative. Next, a sulfochloride such as alkyl or allyl sulfonyl chloride is reacted to form a monosulfonyl ester. Finally, by reacting with a base, cis-2,3-
An epoxy-4-alkoxyphenylbutanoic acid derivative () is obtained. The cis-glycolation reaction used in this method includes the well-known osmium tetroxide-pyridine method, the osmium tetroxide-oxidizing agent (e.g., chlorate, hydrogen peroxide solution, tert-butyl hydroperoxide, etc.) method,
Any method such as the permanganate method can be applied, and the target compound can be obtained in high yield. When using osmium tetroxide, it is preferable to use a combination method with an oxidizing agent, considering that this reagent is expensive and toxic.
About 0.001 mole of osmium tetroxide and about 1.5 to 2.5 moles of oxidizing agent are used. In addition, the alkyl or allyl sulfonyl chloride used in monosulfonylation is used in an amount of 1 to 1.5 equivalents based on the raw material, and the base is used so that it does not cause any undesirable side reactions under the reaction conditions and during post-treatment. Any substance may be used as long as it can be easily removed, and representative examples thereof include organic bases such as pyridine, triethylamine, and collidine, and metal bases such as sodium hydride and sodium alkoxide. The reaction temperature can be arbitrarily selected within the range of 0 to 100°C, but room temperature is optimal. The reaction time varies depending on the reaction temperature, but 3 to 30 hours is sufficient at room temperature. In addition, metal bases such as sodium and potassium hydride and sodium and potassium alkoxide are suitable as bases used in the epoxidation reaction, and 1 to 1.1 equivalents thereof are added to inert bases such as benzene, toluene, tetrahydrofuran, and ether. The reaction may be carried out in a solvent. The reaction temperature may be the boiling point of the solvent used, and the epoxide compound can be obtained in good yield in a reaction time of 6 to 20 hours. In any of the above cases, it is not necessary to use any special method to separate and purify the target substance from the reaction mixture after the completion of the reaction, and this can be easily achieved by well-known means commonly used for such purposes. In this method, the starting material, a trans-4-lower alkoxyphenyl-2-butenoic acid derivative represented by the general formula (), can be obtained by reacting the corresponding lower alkoxyphenylacetaldehyde with a Wittig reagent. can get. The compound of the general formula () thus obtained is reacted with ammonia, and the resulting compound is then hydrolyzed to produce 3-amino-2-hydroxy-4-p-hydroxyphenylbutanoic acid. DL-threo-3-amino-2-hydroxy-4-p-hydroxyphenylbutanoic acid is obtained. The reaction between the compound of general formula () and ammonia is carried out in an alcoholic solvent from 0°C to the boiling point of the solvent, preferably
It is carried out at a temperature of 15-30 ° C. Ammonia is usually used in the form of aqueous ammonia. The compound of general formula () can be obtained by hydrolyzing the obtained compound, but it is possible to obtain a compound of general formula () by using a hydrolyzing agent that is usually used for hydrolysis, such as hydrochloric acid.
When hydrolyzing under heating reflux for about 20 to 90 minutes
DL-threo-3-amino-2-hydroxy-4
-p-methoxyphenylbutanoic acid is obtained. This compound is further heated and refluxed for about 10 to 20 hours in the presence of a hydrolyzing agent such as hydrochloric acid, and when it is completely hydrolyzed, the methoxy group becomes a hydroxyl group and DL
-threo-3-amino-2-hydroxy-4-p
-Hydroxyphenylbutanoic acid can be obtained. In addition, the compound obtained by the reaction with ammonia is directly treated in the presence of a hydrolyzing agent such as hydrochloric acid.
The above results can also be obtained by heating under reflux for about 20 hours.
DL-threo-3-amino-2-hydroxy-4
-p-hydroxyphenylbutanoic acid can be obtained. Examples of lower alkoxy groups in the present invention include methoxy, ethoxy, propoxy, and butoxy groups, and this lower alkoxy group may be substituted at any of the ortho, meta, or para positions on the phenyl nucleus. Good too. Note that DL-threo-3-amino-2-hydroxy-4-p-hydroxyphenylbutanoic acid has useful physiological activity when reacted with (s)-leucine by a conventional method to form a peptide bond. A derivative having a p-hydroxyl group on the phenyl nucleus of subbestatin can be obtained. Also DL-threo-3-amino-2-hydroxy-
4-p-hydroxyphenylbutanoic acid is (s)-
Before the reaction with leucine, it may be optically resolved to form optical isomers and then reacted with (s)-leucine. As described above, the method of the present invention can easily produce the phenyl nucleus of bestatin in high yields without producing any by-products, under mild reaction conditions, with simple operations, and using readily available raw materials. This work opens the door to obtaining cis-2,3-epoxy-4-substituted phenylbutanoic acid derivatives, which are compounds that have not been described in any literature and are advantageous intermediates for the synthesis of derivatives having p-hydroxyl groups on top. The present invention will be specifically described below with reference to Examples and Reference Examples. Example 1 Synthesis of cis-2,3-epoxy-4-p-methoxyphenylbutanoic acid methyl ester From cis-4-p-methoxyphenylbutanoic acid methyl ester, cis-4-p-methoxyphenylbutenoic acid methyl ester 366 mg of ester and 1.02 g of disodium hydrogen phosphate to 10 ml of methylene chloride
and heated this solution to reflux for 90 min.
% hydrogen peroxide solution 100mg and trifluoroacetic anhydride
A trifluoroperacetic acid solution prepared from 680 mg is slowly added dropwise. After the addition is complete, reflux is continued overnight. After completion of the reaction, water is added until all the inorganic substances in the reaction mixture are dissolved, and the methylene chloride layer is separated, washed with water, dried over anhydrous sodium sulfate, and concentrated under reduced pressure to obtain 320 mg of an oily substance. This was subjected to column chromatography using 10 g of silica gel (MERCK Kieselgel 60) and eluted with benzene to obtain 260 mg of oily cis-2,3-epoxy-4-p-methoxyphenylbutanoic acid methyl ester. Yield 66% Elemental analysis value (as C ₁₂ H ₁₄ O ₄ ) Theoretical value C: 64.85% H6.35% Experimental value C: 65.13% H: 6.22% IRν ^film _nax 1750, 1610, 1580, 1515, 1250
，
1035, 800cm ^-1 NMR (CDCl ₃ ) δ: 3.57 (1H.dJ=4Hz

[Formula]) 3.23~3.47 (1H.m.

[Formula]) Threo-3-hydroxy-2-tosyloxy-
From 4-p-methoxyphenylbutanoic acid methyl ester, dissolve 800mg of threo-3-hydroxy-2-paratoluenesulfonyloxy-4-p-methoxyphenylbutanoic acid methyl ester in 15ml of anhydrous benzene, and dissolve sodium hydride.
Add 58 mg and heat to reflux overnight. After the reaction, the benzene layer is washed successively with water and saturated brine, dried over anhydrous sodium sulfate, and concentrated under reduced pressure to obtain 570 mg of an oily substance. 15g of silica gel
column chromatography and elution with benzene yielded 397 mg of oily cis-2,3-epoxy-4-p-methoxyphenylbutanoic acid methyl ester.
get. Yield 88% Reference example 1 dl-threo-3-amino-2-hydroxy-4
- Synthesis of p-methoxyphenylbutanoic acid 220 mg of cis-2,3-epoxy-4-p-methoxyphenylbutanoic acid methyl ester was dissolved by adding 3 ml of methanol and 3 ml of 29% aqueous ammonia,
Stir and react at room temperature for 6 days. After the reaction was completed, the reaction solution was concentrated under reduced pressure, and then 6N hydrochloric acid 2
ml and heated under reflux for 1 hour for hydrolysis. After the reaction, the mixture is concentrated under reduced pressure, added with 2 ml of water, and passed through a column packed with 5 ml of strongly acidic ion exchange resin Dowex 50 (H type) to adsorb the target product. After washing with water,
Elute with 2N ammonia water, and concentrate the eluate to dryness under reduced pressure to obtain 125 mg of crystals. Yield 56% mp.245-247℃ (decomposition) Elemental analysis value (as C ₁₁ H ₁₅ O ₄ N) Theoretical value C: 58.65%, H: 6.71%, N: 6.22% Experimental value C: 58.98%, H :6.61%, N:6.44% IRν ^Nujol _nax 3375, 1640, 1620, 1580, 1515
，
1255, 1090, 825cm ^-1 Reference example 2 dl-threo-3-amino-2-hydroxy-4
-Synthesis of p-hydroxyphenylbutanoic acid dl-threo-3-amino-2-hydroxy-4
-Heat reflux 30 mg of p-methoxyphenylbutanoic acid with 2 ml of 6N hydrochloric acid for 20 hours. After the reaction, concentrate under reduced pressure, add 1 ml of water, and pass through a column packed with 1.5 ml of strongly acidic ion exchange resin Dowex 50 (H type) to adsorb the target product. After washing with water, elute with 2N aqueous ammonia, and concentrate the eluate to dryness under reduced pressure to obtain 20 mg of amorphous powder. Yield 72% mp.266-268℃ (decomposition) Elemental analysis value (as C ₁₀ H ₁₃ O ₄ N) Theoretical value C: 56.86%, H: 6.20%, N: 6.63% Experimental value C: 57.19%, H :6.02%, N:6.87% IRν ^Nujol _nax 3425, 3200, 3125, 1635, 1615,
1590,
1515, 1380, 1265, 1100, 850 cm ^-1 Reference example 3 Synthesis of cis-4-p-methoxyphenyl-2-butenoic acid methyl ester (1) 3-oxo-4-p-methoxyphenyl butanoic acid methyl ester Synthesis of Meldrum's acid (2,2-dimethyl-1,3-dioxane-4,6-dione) 8.6g, pyridine 9.4g
In a solution of 50 ml of methylene chloride, add 11 g of p-methoxyphenyl acetic acid chloride to 20 ml of methylene chloride.
ml of the solution was added under ice-cooling, and the mixture was reacted for 1 hour under ice-cooling and then for 1 hour at room temperature. After the reaction is complete, pour the dark brown reaction solution into ice water and acidify with concentrated hydrochloric acid. The organic layer is washed successively with water and saturated brine, dried over anhydrous sodium sulfate, and concentrated under reduced pressure to obtain dark brown crystals. Then, without purification, methanol 60
ml and heated under reflux for 2 hours. Concentrate under reduced pressure to obtain 12 g of dark brown oil. Obtain 8.2 g of a fraction with a Bp of 142-144°C/0.1 mmHg. Yield 62% Elemental analysis value (as C ₁₂ H ₁₄ O ₄ ) Theoretical value C: 64.85% H: 6.35% Experimental value C: 64.51% H: 6.55% IRν ^film _nax 1745, 1715, 1610, 1580, 1510,
1250, 1035cm ^-1 NMR (CDCl ₃ ) δ: 3.43 (2H.S.

【formula】) 3.70 (3H.S.

【formula】) 3.75 (2H.S.

【formula】) 3.80 (3H.S.

[Formula]) (2) Synthesis of 5-p-methoxybenzylpyrazolone Add 500 mg of hydrazine monohydrate to a solution of 2.22 g of 3-oxo-4-p-methoxyphenylbutanoic acid methyl ester in 6 ml of ethanol. White crystals begin to precipitate after 30 minutes. Collect the crystals and wash with ether to obtain 1.6 g. Yield 78% mp.190-191℃ Elemental analysis value (as C ₁₁ H ₁₀ O ₂ N ₂ ) Theoretical value C: 65.33% H: 4.98%
N: 13.86% Experimental value C: 65.59% H: 5.13%
N: 13.67% IRν ^Nujol _nax 2750～2550, 1605, 1560, 1510
，
1465, 1025, 755cm ^-1 NMR (DMSO−d ₆ ) δ: 3.67 (5H.S.

【formula】) 5.13 (1H.S.

[Formula]) (3) Synthesis of 4-p-methoxyphenyltetrolic acid methyl ester A solution of 6.5 g of thallium nitrate in 20 ml of methanol is added dropwise to a solution of 1.7 g of 5-p-methoxybenzylpyrazolone in 10 ml of methanol. After stirring at room temperature for 30 minutes,
Heat to reflux for 30 minutes. After the reaction is complete, remove the precipitate and add 60 ml of chloroform to the methanol solution. The chloroform layer is washed with water and saturated brine, and then dried over anhydrous sodium sulfate. The chloroform layer was then passed through a column containing 30 g of Florosil, and concentrated under reduced pressure to obtain 1.3 g of a yellow oil. Yield 82% Elemental analysis value (as C ₁₂ H ₁₂ O ₃ ) Theoretical value C: 70.57% H: 5.92% Experimental value C: 70.25% H: 6.20% IRν ^film _nax 2250, 1715, 1610, 1510, 1250,
1070, 835, 750cm ^-1 NMR (CDCl ₃ ) δ: 3.67 (2H.S.

【formula】) 3.77 (3H.S.

【formula】) 3.80 (3H.S.

[Formula]) (4) Synthesis of cis-4-p-methoxyphenyl-2-butenoic acid methyl ester 500 mg of 4-p-methoxyphenyl tetrolic acid methyl ester was dissolved in 5 ml of methanol, and Lindlar catalyst (5% Pd - Add 100 mg of BaSO ₄ ) and 1 drop of quinoline for catalytic reduction. When 1 equivalent of hydrogen has been absorbed, the reaction is stopped, the catalyst is removed, the solvent is distilled off under reduced pressure, and the mixture is subjected to column chromatography on 10 g of silica gel and eluted with benzene to obtain 483 mg of an oily substance. Yield 96% Elemental analysis value (as C ₁₂ H ₁₄ O ₃ ) Theoretical value C: 69.88% H: 6.84% Experimental value C: 70.18% H: 6.71% IRν ^ffim _nax 1720, 1645, 1610, 1510, 1250,
1040, 830cm ^-1 NMR (CDCl ₃ ) δ: 5.78 (1H.dt.J=1,11Hz

[Formula]) Reference Example 4 Synthesis of 3-hydroxy-2-p-toluenesulfonyloxy-4-p-methoxyphenylbutanoic acid methyl ester (1) trans-4-p-methoxyphenyl-2-
Synthesis of butenoic acid methyl ester with 8.6g of p-methoxyphenylacetaldehyde and
A solution of 20 g of Wittig reagent (methoxycarbonylmethylenetriphenylphosphorane) in 30 ml of benzene is stirred at room temperature overnight. After the reaction, benzene is distilled off under reduced pressure, and 100 ml of n-hexane is added to the residue, followed by stirring. Insoluble materials were removed and the n-hexane layer was distilled off under reduced pressure to obtain an oily substance. This was subjected to column chromatography using 30 g of silica gel and eluted with benzene to obtain 11 g of an oily substance. Yield 93% Elemental analysis value (as C ₁₂ H ₁₄ O ₃ ) Theoretical value C: 69.88% H: 6.84% Experimental value C: 70.15% H: 6.68% IRν ^film _nax 1720, 1660, 1612, 1595, 1515,
1250, 1040, 835cm ^-1 NMR (CDCl ₃ ) δ: 5.77 (1H.dt J=1,16Hz

[Formula]) (2) Synthesis of threo-2,3-dihydroxy-4-p-methoxyphenylbutanoic acid methyl ester 824 mg of trans-4-p-methoxyphenyl-2-butanoic acid methyl ester, tetraethylammonium acetate, Tetrahydrate 262mg, 70% tert
-A solution of 1 ml of butyl hydroperoxide, 1 ml of osmium tetroxide solution (adjusted from 1 g of osmium tetroxide, 199 ml of tert-butanol, and 1 ml of 90% hydrogen peroxide) in 10 ml of acetone is stirred at room temperature for 20 hours. After reaction, add 35ml of ether and dilute to 20% under ice cooling.
Add 2 ml of sodium bisulfite aqueous solution and stir for 1 hour. The ether layer is washed with saturated brine, dried over anhydrous sodium sulfate, and concentrated under reduced pressure to obtain white crystals. When this is washed with petroleum ether and dried, 690 mg of the target product is obtained. Yield 72% mp.71-73℃ Elemental analysis value (as C ₁₂ H ₁₆ O ₅ ) Theoretical value C: 59.99% H: 6.71% Experimental value C: 59.72% H: 7.02% IRν ^Nujol _nax 3400, 1725, 1610 ,1510,1250
，
1055,850cm ^-1 (3) Synthesis of 3-hydroxy-2-p-toluenesulfonyloxy-4-p-methoxyphenylbutanoic acid methyl ester Threo-2,3-dihydroxy-4-p-methoxyphenyl Rubbutanoic acid methyl ester 1.1g and p-
Toluenesulfonyl chloride 1.3g pyridine 6
Stir the ml solution overnight at room temperature. After the reaction, pour into ice water, make acidic with 2N hydrochloric acid, and extract with ethyl acetate. The organic layer is washed successively with water and saturated brine, dried over anhydrous sodium sulfate, and concentrated under reduced pressure to obtain 2 g of a brown oil. This was subjected to column chromatography using 30 g of silica gel and eluted with benzene-ethyl acetate (4:1) to obtain 1.4 g of the desired product. yield
78% Elemental analysis value (as C ₁₉ H ₁₈ O ₇ S) Theoretical value C: 58.46% H: 4.65% Experimental value C: 58.79% H: 4.52% IRν ^film _nax 3500, 1765, 1740, 1610, 1595,
1510, 1370, 1250, 1180cm ^-1 NMR (CDCl ₃ ) δ: 2.43 (3H.S.

[Formula]) 2.77 (2H.dJ=7Hz

[Formula]) 4.71 (1H.dJ=3Hz

【formula】)

Claims (1)

[Claims] 1. General formula (In the formula, R ₁ is a lower alkoxy group, and R ₂ is a protecting group for a carboxyl group.) A cis-2,3-epoxy-4-lower alkoxyphenylbutanoic acid derivative represented by the following. 2 General formula (In the formula, R ₁ is a lower alkoxy group and R ₂ is a protecting group for a carboxyl group.) cis-Lower alkoxyphenyl-
General formula characterized by epoxidizing a 2-butenoic acid derivative (In the formula, R ₁ and R ₂ are the same as above.) A method for producing a cis-2,3-epoxy-4-lower alkoxyphenylbutanoic acid derivative represented by the following. 3 General formula (In the formula, R ₁ is a lower alkoxy group and R ₂ is a protecting group for a carboxyl group.) The trans-4-lower alkoxyphenyl-2-butenoic acid derivative represented by the formula is converted into cis-glycol, and the general formula (In the formula, R ₁ and R ₂ are the same as above) A 2,3-dihydroxy-4-lower alkoxyphenylbutanoic acid derivative represented by By reacting with the general formula (In the formula, R ₁ and R ₂ are the same as above.) A method for producing a cis-2,3-epoxy-4-lower alkoxyphenylbutanoic acid derivative represented by the following.