JPH08788B2 - Method for producing amide compound - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to peptide synthesis, chemical modification of proteins, and methods for producing other industrially useful amide compounds.

[0002]

2. Description of the Related Art In recent years, many chemical methods for chemically synthesizing physiologically active peptides such as tasty peptides represented by peptide hormones and sweeteners have been announced. Many methods have been used for a long time as a chemical synthetic method for these peptides and other industrially useful amides. For example, a method using an acid chloride, a method using an acid azide, a method using a dehydration condensing agent such as dicyclohexylcarbodiimide, and an active ester method for converting a carboxyl component into an active ester to accelerate a nucleophilic substitution reaction are known. Has been.

Among these various methods, particularly in forming an acid amide bond, the active ester method is different from the other methods in that it has the characteristic of proceeding even in the presence of water in the reaction system. Therefore, various active esters have also become important reaction reagents in the field of peptide synthesis.
Known active esters conventionally used are esters with phenol derivatives such as p-nitrophenol and pentachlorophenol, and esters with N-hydroxysuccinimide.

However, although the former phenolic active ester is excellent in reactivity, it is difficult to remove the phenol derivative produced after aminolysis,
Satisfactory purity cannot be obtained without recrystallization or purification by chromatography. N-Hydroxysuccinimide is itself water-soluble and easy to remove from the product, but the reaction yield is not satisfactory. Furthermore, in the reaction using these reagents,
The ester compound formed as the intermediate has a drawback that it is hardly soluble in water. Further, 4-hydroxy-2-methylphenyldimethylsulfonium iodide is a known compound described in J. Amer. Chem. Soc., 80, 3425 (1958), and is known as a highly acidic water-soluble phenol derivative. ing.

[0005]

The present inventors have found that the following sulfonium compound (1) is particularly excellent as an active ester as a method for chemically synthesizing peptides and other industrially useful methods for synthesizing amides. , It has been found to act as a useful amide bond generator.

Embedded image W—O-p-C ₆ H ₄ —S ⁺ (CH ₃ ) ₂ · X ^— (1) (wherein W is an arylsulfonyl group, or an α-amino group thereof and / or a side chain thereof) Introduced a protective group,
Alternatively, it is a residue of an amino acid that has not been introduced, and X 1 represents a halogen ion, a perchlorate ion, a hydrogensulfate ion, a methylsulfate ion, or a p-toluenesulfonate ion. )

According to the method disclosed in the present invention, if an active amino acid represented by the above general formula (1) is used as a substrate and an appropriate amino acid represented by the general formula HY acts, the active ester derived from the phenolsulfonium salt is used as a substrate. , WY, the target amino acid derivative can be obtained in high yield and high purity. Where Y is a side chain and / or α-
A residue of an amino acid with or without introduction of a suitable protecting group to a carboxyl group, and the residue is N of the amino acid.
It means a group obtained by removing hydrogen from the terminal.

In connection with the present invention, 4-produced after amidation
Hydroxyphenyldimethylsulfonium compounds are water soluble due to their ionic character. Therefore, in the decomposition and removal after the reaction, which has been a problem with conventional active esters, it has a feature that it can be easily separated and removed from the target product by washing with water. Further, since the active ester itself represented by the general formula (1) of the present invention is almost always water-soluble, when an amino acid which is a water-soluble compound is used as a nucleophile, a system of water alone is used as a reaction solvent. You can choose.

Further, conventionally, when a reaction similar to this was carried out, it was necessary to protect functional groups and side chains which are not involved in the reaction with a suitable protecting group before carrying out the reaction. Since the water-soluble active ester can use water as a reaction solvent, by adjusting the pH of the aqueous solution, a site that should not react can be protonated to arbitrarily make an inactive state. As a result, the reaction can be carried out while leaving the side chains and functional groups unprotected. This is an important feature that conventional active esters do not have, and can be a means for solving the problem of denaturation by organic solvents. Further, regarding the synthesis of amides in a system using a general organic solvent, there is no difference in the reaction yield from the conventional active ester.

[0009]

The active ester of the present invention gives an equivalent or higher reaction yield in terms of reactivity as compared with conventional esters of p-nitrophenol, pentachlorophenol and N-hydroxysuccinimide. Further, a major feature of the active ester of the present invention is that the active ester itself represented by the general formula (1) of the present invention is also water-soluble, and it is possible to carry out the amidation reaction with an aqueous solvent alone. . Further, in the case of chemically modifying a protein, since an organic solvent or the like is not used, denaturation cannot occur, which is an effect not present in conventional active esters.

The active ester of the present invention is not limited to the use of water as a reaction solvent, but it is possible to use other general water-compatible solvents or water-insoluble solvents. Is also fully effective. For example, in the method for synthesizing amides that are not inactivated in an organic solvent, the reaction proceeds promptly even in a two-layer heterogeneous system of chloroform, dichloromethane, ethyl acetate, etc. capable of dissolving the ester of the present invention and water. . Moreover, not only the formation of the carboxylic acid amide bond but also the synthesis of other industrially useful amides can be widely applied.

[0011]

EXAMPLES Example 1 Reaction in aqueous solution Synthesis of benzyloxycarbonylalanylglycine 4.33 g of dimethyl [(4-benzyloxycarbonylalanyloxy) phenyl] sulfonium methylsulfate was added to water 2
20 ml of an aqueous solution of 0.68 g of glycine and 1.28 ml of triethylamine was added dropwise while being dissolved in 0 ml while stirring at room temperature. 12
After stirring for 2 hours, 2% HCl was added to the reaction solution to adjust the pH to 2, and 100 ml of ethyl acetate was extracted twice from the aqueous solution. Dry the ethyl acetate layer,
Ether was added to the residue obtained by concentration under reduced pressure to obtain a white crystalline substance. Yield 1.58g (61.9%) mp 134.1-135.3 ° C [α] _D -17.5 ° (c1. Alc)

Example 2 Reaction in Chloroform-Water Bilayer System Synthesis of Benzyloxycarbonylalanylvaline Dimethyl [(4-benzyloxycarbonylalanyloxy) phenyl] sulfonium p-toluenesulfonate 4.14 g in chloroform 50 ml. After being dissolved, 20 ml of an aqueous solution of 0.91 g of valine and 1.1 ml of triethylamine was added dropwise with stirring at room temperature, and the mixture was stirred at room temperature for 8 hours. The reaction solution was separated, the chloroform layer was washed with water, dried and concentrated under reduced pressure, and ether was added to the resulting residue to obtain a white crystal. Yield 2.42g (75.0%) mp 121.5-124.2 ° C [α] _D -12.0 ° (c1. Alc)

Example 3 Reaction in homogeneous mixed solvent of acetonitrile-water Synthesis of tosylphenylalanine 4.08 g of dimethyl [(4-p-toluenesulfonyloxy) phenyl] sulfonium perchlorate was added to acetonitrile 5
It was dissolved in 0 ml, and 50 ml of an aqueous solution of 1.65 g of phenylalanine and 1.4 ml of triethylamine was added dropwise while stirring at room temperature. The mixture was stirred for 5 hours, and 2% HCl was added to the reaction solution to adjust to pH 2, white crystals were precipitated. The crystals were collected by filtration and recrystallized from 60% alcohol to obtain the desired product. Yield 2.08g (65.0%) mp 133.5-135.1 ℃

[0014]

As is apparent from the examples, according to the method for producing an amide compound of the present invention, the side chains and functional groups of amino acids are not protected as compared with the conventional active ester while the reaction is performed. And that the sulfonium compound formed after amidation is water-soluble, it has a feature that it can be easily separated and removed by washing with water from the target substance in decomposition and removal after the reaction. It has the characteristics of

Claims (4)

[Claims] 1. A method for producing an amide compound according to general formula 3, which comprises reacting an ester sulfonium salt represented by general formula 1 with an amino acid represented by general formula 2. Embedded image W-O-p-C ₆ H ₄ -S ⁺ (CH ₃ ) ₂ · X- (1) embedded image HY (2) embedded image W-Y (3) (here And W is an arylsulfonyl group, or an α-amino group and / or a suitable protecting group is introduced into the side chain thereof,
Alternatively, it is a residue of an amino acid that has not been introduced, and X represents a halogen ion, a perchlorate ion, a hydrogensulfate ion, a methylsulfate ion, or a p-toluenesulfonate ion.
Y is a residue of an amino acid with or without introducing a suitable protecting group into the side chain and / or α-carboxyl group. ) 2. The method for producing an amide compound according to claim 1, wherein the reaction of the ester sulfonium salt represented by the general formula 1 and the amino acid represented by the general formula 2 is carried out in an aqueous solvent. 3. The reaction between the ester sulfonium salt represented by the general formula 1 and the amino acid represented by the general formula 2 is carried out in a water-soluble organic solvent alone or in a mixed system of water and the water-soluble organic solvent. Item 2. The method for producing an amide compound according to Item 1. 4. A reaction between an ester sulfonium salt represented by the general formula 1 and an amino acid represented by the general formula 2 in a solvent incompatible with water alone or in a two-phase system of a solvent incompatible with water and water. The method for producing an amide compound according to claim 1, which is performed.