JPH0380147B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a novel method for producing amino acid amides. Calcitonin, gonadotropin-releasing hormone (LH-RH), melanocyte-stimulating hormone (α-MSH), secretin,
Some natural bioactive peptides have amidated carboxyl terminals, such as Substance P, thyrotropin-releasing hormone (TRH), vasoactive intestinal peptide (VIP), and Vasopressin. (See Pharmacia Review No. 3, Physiologically Active Peptides, Pharmaceutical Society of Japan, 1980). Amino acid amides are extremely important compounds as starting materials for synthesizing these natural peptides and their related compounds. N-protected amino acid amides are also useful substances as starting materials for monocyclic β-lactams. For example, N-benzyloxycarbonyl-L-threoninamide is the starting material for azuthreonam (see JP-A-56-125362). [Prior Art] Conventional methods for producing amino acid amides or N-protected amino acid amides are as follows: 1. An amino acid amide is obtained by aminolysis of a lower alkyl ester of an amino acid, and then, if necessary, free amino groups are protected. Method 2 Direct condensation of an N-protected amino acid and an amine using a carbodiimide such as dicyclohexylcarbodiimide or ethyldimethylaminopropylcarbodiimide, and then removing the protecting group as necessary Method 3 Mixed acid of an N-protected amino acid and an alkyl carbonic acid A method is known in which an anhydride is reacted with an amine and then, if necessary, a protecting group is removed. [Problems to be Solved by the Invention] However, although these methods are suitable for synthesis on a laboratory scale, they are not suitable for mass production.
That is, implementing method 1) requires a large excess of ammonia gas and a pressurized reaction vessel to prevent leakage of the ammonia gas, which poses problems in terms of cost and safety. Method 2) requires carbodiimide, which is expensive and causes severe irritation if it adheres to the skin, and method 3) requires reaction conditions of -20°C or lower because the mixed acid anhydride is unstable. However, problems remain in terms of price and equipment. [Means for Solving the Problems] Therefore, the present inventors conducted intensive studies to develop a method suitable for mass production of N-protected amino acid amides, and as a result, a method selected from phosphorus halides and phosphorus oxyhalides was developed. At least one phosphorus compound and general formula () (In the formula, X and Y are the same or different and are a hydrogen atom, a lower alkyl group having 1 to 7 carbon atoms,
Indicates an allyl group or an aralkyl group. ) is reacted with an amine represented by the formula ( ) (In the formula, A-CO represents an amino acid residue whose amino group may be protected.) It has been found that an amino acid amide represented by the following formula can be obtained. To explain the present invention in more detail, the phosphorus halides used as the raw material of the present invention include, for example, phosphorus trihalides and phosphorus pentahalides, and specifically, for example, phosphorus trichloride, phosphorus tribromide, Examples include phosphorus pentachloride and phosphorus pentabromide.
Examples of the phosphorus oxyhalide include phosphorus oxychloride and phosphorus oxybromide. The amines used are those represented by the general formula (), where X and Y are the same or different and represent a hydrogen atom or an alkyl group, an allyl group, or an aralkyl group having 1 to 7 carbon atoms, and are branchable. may be branched or circular.
Specific examples of X and Y include lower alkyl groups having 1 to 7 carbon atoms such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, and heptyl group, phenyl group, and benzyl group. It will be done. Specific representative examples of amines of general formula () include ammonia, methylamine, ethylamine,
Examples include propylamine, butylamine, pentylamine, hexylamine, heptylamine, dimethylamine, diethylamine, dipropylamine, methylbenzylamine, ethylbenzylamine, aniline, and benzylamine. The amino acid in the N-protected amino acid used in the present invention is not limited to monoaminomonocarboxylic acid, and any amino acid having a functional group in its side chain may be used without any problem. Specific representative examples of amino acids include glycine, alanine, β-alanine, ornithine, aspartic acid, asparagine, glutamic acid, glutamine, pyroglutamic acid, histidine, hydroxylysine, hydroxyproline, isoleucine, leucine, lysine, phenylalanine, Examples include proline, serine, threonine, tryptophan, tyrosine, valine, phenylglycine, hydroxyphenylglycine, γ-aminobutyric acid, methionine, arginine, and cysteine. As a protecting group for the N-protected amino acid of the present invention, protecting groups for amino groups used in peptide chemistry can be used, but among them, preferable protecting groups include a benzyloxycarbonyl group, a lower alkoxy group on a phenyl group, and a lower alkyl group on a phenyl group. group, a halogen atom, a benzyloxycarbonyl group having a nitro group (e.g. p-methoxybenzyloxycarbonyl group, p-chlorobenzyloxycarbonyl group,
p-bromobenzyloxycarbonyl group, p-nitrobenzyloxycarbonyl group), tert-alkoxycarbonyl group (e.g. tert-butyloxycarbonyl group, tert-pentoxycarbonyl group),
Formyl and phthalyl groups are common. When using an amino acid having a functional group in its side chain, this side chain functional group may be protected. The protecting group used here may be a protecting group commonly used in peptide chemistry depending on the type of side chain functional group. Representative examples of amino acids with side chain functional groups protected include δ-benzyloxycarbonyl or t-butoxycarbonyl-ornithine;
Aspartate β-benzyl or t-butyl ester, Glutamate γ-benzyl or t-butyl ester, N ^im -benzylhistidine, N ^im -tosylhistidine, O-benzyl or t-butylhydroxylysine, O-benzyl or t-butyl Hydroxyproline, ε-benzyloxycarbonyl or t-butoxycarbonyllysine, O-benzyl or t-butylserine, O-benzyl or t-
-butylthreonine, O-benzyl or t-butyltyrosine, O-benzyl or t-butylhydroxyphenylglycine, methionine sulfoxide, N ^G -tosyl or nitro or benzyloxycarbonylarginine, s-benzyl or methoxybenzyl or acetamidomethylcysteine etc. can be mentioned. Note that the steric configuration of the amino acid having an asymmetric carbon may be any of L, D, and DL. Two methods can be employed to implement the invention. Specifically, one method is to dissolve phosphorus halide or phosphorus oxyhalide (hereinafter abbreviated as phosphorus halides) in the above-mentioned solvent, add amines under ice cooling, react, and then form a reaction product. One method involves isolating the product and reacting it with an N-protected amino acid in a solvent. The other method is to subject the product to the next reaction with the N-protected amino acid as it is in solution without isolating it. however,
The latter method is preferable in view of both the stability of the reaction product and the ease of handling. The solvent used in the present invention is not particularly limited as long as it does not participate in the reaction, and specific examples include dichloromethane, chloroform, halogenated hydrocarbons such as carbon tetrachloride, and cyclic ethers such as dioxane and tetrahydrofuran. Examples include aromatic hydrocarbons such as benzene, toluene, and xylene, and esters such as methyl acetate, ethyl acetate, and n-propyl acetate. The amount of phosphorus halide, which is a reaction reagent of the present invention, is not particularly limited as long as it is 0.5 molar equivalent or more relative to the N-protected amino acid, but it is preferably 1.0 to 1.5 molar equivalent. The amount of amine is 3 to 10 molar equivalents, preferably 5 to 8 molar equivalents, relative to the phosphorus halide. The reaction temperature used in the present invention is not particularly limited, but it can usually be carried out between room temperature and the boiling point of the solvent, but it is preferable to use a solvent with a boiling point of 60 to 100°C and carry out the reaction at a temperature at or near the boiling point. is usually 2
Completed in ~8 hours. If the N-protected amino acid amide thus produced is itself soluble in the reaction solvent, water is added to extract the target compound into the organic solvent layer, and if necessary, 5
It can be easily isolated by sequentially washing with % sodium bicarbonate aqueous solution and saturated saline, removing the solvent under reduced pressure, and then adding water or a suitable solvent to crystallize. If the target compound does not dissolve in the reaction solvent, it can be isolated by removing the solvent under reduced pressure, adding an extraction solvent, and performing the same operation as above. If the target compound is insoluble in water, it can be isolated by removing the solvent under reduced pressure and then adding water for crystallization. If necessary, the N-protecting group of the isolated N-protected amino acid amide can be removed by a known method to obtain an amino acid amide. Removal of the protecting group may be carried out at a temperature below the boiling point of the solvent, for example -50°C, depending on the type of protecting group or the type of solvent.
It can be carried out at a temperature ranging from ℃ to 150℃, preferably from -40℃ to 120℃, and various inorganic and organic solvents can be used as the solvent. Examples of inorganic solvents include water, liquid ammonia, and liquid fluoride. Examples of organic solvents include aqueous solvents such as C ₁ to _{C 4} alcohols, acetic acid, dimethylformamide, and dioxane, and acetic acid lower alkyl esters, and these can be used as a mixed solvent in some cases. . Methods for removing the protective group include methods such as reduction (for example, catalytic reduction or reduction with an alkali metal and ammonia), hydrolysis, acid decomposition, and hydrazine decomposition, depending on the type of the protective group. Table 1 shows preferred types of protecting groups and preferred removal methods.

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〔Effect of the invention〕

According to the present invention, there is no need for special reaction equipment such as a pressurized reaction vessel or special reaction conditions such as -20°C or lower, and there is no need for expensive raw materials such as carbodiimide. The amide can be obtained with high purity and high yield without racemization. Therefore, the method of the present invention is suitable for mass production of amino acid amides. Example 1 1.37 g of phosphorus trichloride in 30 ml of chloroform
(10.0 mmol) is added and cooled to 5°C, and 1.02 g (60.0 mmol) of ammonia gas is introduced into this solution at a temperature range of 5 to 20°C. After introduction, 2.16 g of N-(tert-butyloxycarbonyl)-L-valine
(10.0 mmol) and reacted under heating under reflux for 7 hours. After the reaction, the reaction solution was concentrated under reduced pressure to remove chloroform, and 20 ml of ethyl acetate and 20 ml of water were added to the residue.
The product is extracted into ethyl acetate layer. 5% extract
10ml of sodium bicarbonate aqueous solution and 10ml of saturated saline solution
The obtained ethyl acetate layer is dried with anhydrous sodium sulfate, and the solvent is distilled off under reduced pressure to obtain 1.60 g of N-(tert-butyloxycarbonyl)-L-valinamide (yield 74.3%). . Melting point: 156-157°C [α] ²⁰ _D -10.1° (C=1.0, acetic acid) This product completely matched the separately synthesized standard product in NMR and IR. Example 2 1.37 g of phosphorus trichloride in 30 ml of chloroform
(10.0 mmol) was added and cooled to 5°C, and 0.85 g (50.0 mmol) of ammonia gas was introduced into this solution at a temperature below 20°C. After introduction, 2.49 g (10.0 mmol) of N-benzyloxycarbonyl-L-proline was added,
React under heating under reflux for 14 hours. After the reaction, the reaction solution was concentrated under reduced pressure to remove chloroform, and 20 ml of water was added to the residue.
Add to make a solution, and adjust the pH to 8.0 with 1N aqueous sodium hydroxide solution. Next, add 30 ml of ethyl acetate to
Extract twice, wash the ethyl acetate layer with 15 ml of saturated brine, and dry over anhydrous sodium sulfate. The solvent is distilled off under reduced pressure to obtain an oil. By crystallizing from 20 ml of n-hexane and drying, 2.40 g (yield 97.6%) of N-benzyloxycarbonyl-L-prolinamide is obtained. Melting point: 87-89°C [α] ²⁰ _D -32.1° (C=2.0, ethanol) This product completely matched the separately synthesized standard product in NMR and IR. Example 3 1.37 g of phosphorus trichloride in 40 ml of tetrahydrofuran
(10.0 mmol) was added and cooled to 5°C, and 1.02 g (60.0 mmol) of ammonia gas was introduced into this solution at a temperature below 20°C. After introduction, 2.51 g of N-(p-methoxybenzyloxycarbonyl)-L-alanine
(10.0 mmol) and react under heating and reflux for 25 hours. After concentrating the solvent under reduced pressure and distilling it off, the same treatment as in Example 1 yielded 2.07 g of N-(p-methoxybenzyloxycarbonyl)-L-alaninamide.
(Yield 82.1%) is obtained. Melting point: 136-137°C [α] ²⁰ _D +19.5° (C = 1.0, dimethylformamide) This product completely matched the separately synthesized standard product in NMR and IR. Example 4 1.10 g of phosphorus trichloride in 30 ml of chloroform
(7.9 mmol) was added, cooled to 5℃, and 0.67g (39.5 mmol) of ammonia gas was added to this solution at a temperature of 20℃.
It will be introduced below. 2.36g of N-benzyloxycarbonyl-L-phenylalanine after introduction
(7.9 mmol) and reacted under heating under reflux for 6 hours. After the reaction, the reaction solution was concentrated under reduced pressure and the solvent was distilled off.
Coarse crystals are obtained by processing in the same manner as in Example 1. Further recrystallization from 60 ml of 50% aqueous methanol solution yielded 1.35 g of N-benzyloxycarbonyl-L-phenylalaninamide (yield:
87.5%). Melting point: 160-161°C [α] ²⁰ _D -7.2° (C=1.0, methanol) This product completely matched the separately synthesized standard product in NMR and IR. Example 5 Phosphorus oxychloride in 300 ml of tetrahydrofuran
15.30g (0.1mol) was added and cooled to 5℃, and 8.50g (0.5mol) of ammonia gas was added to this solution at a temperature of 20℃.
It will be introduced below. After introduction, N-benzyloxycarbonyl-L-phenylalanine 29.90g (0.1mol)
was added, and the mixture was allowed to react under heating and reflux for 6 hours. After the reaction, the reaction solution was concentrated under reduced pressure to remove the solvent, and the following Example 1 was prepared.
After processing in the same manner as above, add 170 ml of water and dry to obtain N-benzyloxycarbonyl-
L-phenylalanine amide 28.00g (yield 94.0
%) is obtained. Example 6 1.10 g of phosphorus trichloride in 30 ml of chloroform
(7.9 mmol) was added and cooled to 5°C, and 0.80 g (47.4 mmol) of ammonia gas was introduced into this solution at a temperature below 20°C. After the introduction, 2.00 g (7.9 mmol) of N-benzyloxycarbonylthreonine is added, and the mixture is reacted under heating under reflux for 10 hours. After the reaction, the reaction solution was concentrated under reduced pressure to remove the solvent, treated in the same manner as in Example 1, added with 10 ml of water, crystallized, and dried to obtain N-benzyloxycarbonyl-L. - 0.99 g of threoninamide (yield
50%). Melting point: 82-84°C [α] ²⁵ _D +23.7° (C = 1.0, tetrahydrofuran) This product completely matched the separately synthesized standard product in NMR and IR. Example 7 12.10 g of phosphorus oxychloride in 200 ml of chloroform
(79.0 mmol) was added and cooled to 5°C, and 8.00 g (0.47 mol) of ammonia gas was introduced into this solution at a temperature below 20°C. After the introduction, 20.0 g (79.0 mmol) of N-benzyloxycarbonyl-L-threonine is added, and the reaction is carried out under heating under reflux for 6 hours. After the reaction, the reaction solution is concentrated under reduced pressure to remove the solvent, 100 ml of water is added, and the solution is dissolved by heating. The solution was cooled, and the precipitated crystals were collected and dried to yield 16.90 g of N-benzyloxycarbonyl-L-threoninamide.
(Yield 85.0%) is obtained. Example 8 N-benzyloxycarbonyl-L-
16.30 g (yield 82.0%) of threoninamide is obtained. Example 9 16.50 g of N-benzyloxycarbonyl-L-threoninamide (yield 83.0%) was obtained by using ethyl acetate as the reaction solvent in place of chloroform in Example 7 and carrying out the same treatment as in Example 7.
is obtained. Example 10 3.10 g of phosphorus oxychloride in 50 ml of chloroform
(20.0 mmol) was added and cooled to 5°C, and 2.10 g (60.0 mmol) of ammonia gas was introduced into this solution at a temperature below 20°C. After the introduction, the precipitated crystals are left at room temperature for 30 minutes, washed, and dried to obtain 5.20 g of a reaction product containing ammonium chloride. 5.20 g of the obtained reaction product and 5.0 g of N-benzyloxycarbonyl-L-threonine
(19.8 mmol) in 50 ml of benzene at a temperature of 75-85° C. for 3 hours. After the reaction, the reaction solution is concentrated under reduced pressure to remove the solvent, and then 30 ml of water is added and dissolved by heating to form a solution. By cooling and collecting the precipitated crystals, washing and drying, N-benzyloxycarbonyl-L
- 4.40 g of threoninamide (yield 88.0%) is obtained. Example 11 1.37 g of phosphorus trichloride in 30 ml of chloroform
(10.0 mmol) and diethylamine under cooling.
Add 3.66 g (50.0 mmol) dropwise and allow to react at room temperature for 30 minutes. 2.10 g (10.0 mmol) of N-benzyloxycarbonylglycine was added to this solution, and the mixture was allowed to react under heating under reflux for 7 hours. After the reaction, the reaction solution was concentrated under reduced pressure to remove the solvent, and the same procedure as in Example 1 was carried out to obtain 1.58 g (yield: 60.0%) of oily N-benzyloxycarbonylglycine diethylamide. This product completely matched the separately synthesized standard product in NMR and IR. Example 12 1.53 g of phosphorus oxychloride in 50 ml of ethyl acetate
(10.0 mmol) and benzylamine under cooling.
6.43g (60.0mmol) was added dropwise and allowed to react at room temperature for 30 minutes. 2.23 g (10.0 mmol) of N-benzyloxycarbonyl-L-alanine was added to this solution and reacted under heating under reflux for 4 hours. After the reaction, add 30 ml of water and extract the product into a solvent. After drying the extract over anhydrous sodium sulfate, the solvent is concentrated and distilled off under reduced pressure to obtain a crude product. Recrystallization from ethyl acetate and cyclohexane yielded 2.90 g of N-benzyloxycarbonyl-L-alanine benzylamide (yield
92.0%) is obtained. Melting point: 141-142°C [α] ²⁰ _D +8.7° (C = 2.0, dimethylformamide) This product completely matched the separately synthesized standard product in NMR and IR. Example 13 1.53 g of phosphorus oxychloride in 50 ml of ethyl acetate
(10.0 mmol) and benzylamine under cooling.
6.43g (60.0mmol) was added dropwise and allowed to react at room temperature for 30 minutes. 2.10 g (10.0 mmol) of N-benzyloxycarbonylglycine is added to this solution, and the mixture is reacted under heating under reflux for 6 hours. The crude product is obtained by the same treatment as in Example 12. This product is recrystallized from acetone and water to obtain 2.30 g (yield: 88.5%) of N-benzyloxycarbonylglycine benzylamide. Melting point: 119-120℃ This product completely matched the separately synthesized standard product in NMR and IR. Example 14 Phosphorus oxychloride in 50 ml of tetrahydrofuran
1.53 g (10.0 mmol) was dissolved, and 5.23 g (60.0 mmol) of isopentylamine was added dropwise under cooling, and the mixture was allowed to react at room temperature for 30 minutes. Add 2.65 g of N-benzyloxycarbonyl-L-leucine to this solution.
(10.0 mmol) and reacted under heating and reflux for 6 hours. After the reaction, the reaction solution is concentrated under reduced pressure to remove the solvent, 50 ml of ethyl acetate and 50 ml of water are added to the residue, and the product is extracted into ethyl acetate. Add the extract to 30ml of 0.5N hydrochloric acid solution.
The resulting ethyl acetate solution is dried over anhydrous sodium sulfate, and the solvent is distilled off under reduced pressure to obtain a crude product. The obtained crude product is recrystallized from isopropyl ether to obtain 2.80 g (yield: 83.7%) of N-benzyloxycarbonyl-L-leucine isopentylamide. Melting point: 93-94°C [α] ²⁵ _D -18.7° (C=2.0, ethanol) This product completely matched the separately synthesized standard product in NMR and IR. Example 15 1.53 g of phosphorus oxychloride in 50 ml of chloroform
(10.0 mmol) was added dropwise to the solution under cooling, and the mixture was reacted for 30 minutes at room temperature. Add 2.99 g of N-benzyloxycarbonyl-L-phenylalanine to this liquid.
(10.0 mmol) and reacted under heating and reflux for 2 hours. The following treatment is carried out in the same manner as in Example 14 to obtain an oily crude product. This was subjected to column chromatography using 300 g of silica gel and a mixed solvent of toluene-ethyl acetate as a developing solvent, and the fractions containing the target product were collected and the solvent was distilled off by vacuum concentration. enylalanine ethylbenzylamide
2.62 g (yield 63.0%) is obtained. [α] ²⁵ _D −2.8° (C=1.0, methanol) This product completely matched the separately synthesized standard product in NMR and IR. Example 16 2.00 g (8.1 mmol) of N-benzyloxycarbonyl-L-prolinamide was dissolved in 30 ml of methanol, and 0.20 g of palladium black was added to the mixture at room temperature and normal pressure.
Perform time contact reduction. After the reaction, the catalyst is separated and the liquid is concentrated under reduced pressure to remove the solvent, yielding the desired product in the form of an oil. Add 20ml of ether to this and crystallize it.
The precipitated crystals are collected and dried to obtain 0.90 g (yield 97.0%) of L-prolinamide. Melting point: 101-102°C [α] ²⁵ _D -86.6° (C=1.0, methanol) This product completely matched the separately synthesized standard product in NMR and IR. Example 17 N-(p-methoxybenzyloxycarbonyl)
When 2.00 g (7.9 mmol) of -L-alaninamide is treated in the same manner as in Example 16, the desired product is obtained as an oil. 10 ml of isopropyl ether and 20 ml of n-hexane were added to this for crystallization, and the precipitated crystals were taken and dried to yield 0.68 g of L-alaninamide (yield:
98.0%) is obtained. Melting point: 71-72°C [α] ²⁵ _D +6.5° (C=2.0, water) This product completely matched the separately synthesized standard product in NMR and IR. Example 18 1.50 g (7.0 mmol) of N-tert-butyloxycarbonyl-L-valinamide is dissolved in 10 ml of 4N hydrogen chloride dioxane solution and stirred at room temperature for 1 hour.
The solvent was distilled off by concentration under reduced pressure and washed with dry ether to give 1.06 g of L-valinamide hydrochloride (yield:
99.0%) is obtained. Melting point: 262-263°C [α] ²⁰ _D +34.1° (C=1.0, methanol) This product completely matched the separately synthesized standard product in NMR and IR.

Claims (1)

[Claims] 1. At least one phosphorus compound selected from phosphorus halides and phosphorus oxyhalides, and the general formula [Formula] 7 lower alkyl groups,
Indicates an allyl group or an aralkyl group. ) is reacted, then an N-protected amino acid (if the side chain has a functional group, the functional group may be protected) is reacted, and the protecting group is removed as necessary. A method for producing an amino acid amide represented by the general formula [Formula] (wherein A-CO represents an amino acid residue whose amino group may be protected).