JPH0482872A - Production of 13carbon-labeled methionine or homolog thereof - Google Patents

Abstract

PURPOSE:To obtain the subject compound by reducing a specific optically active amino acid into thio anions in liquid ammonia or an amine solvent with an alkali metal and then reacting the resultant product with an alkyl halide having a <13>C-labeled alkyl group. CONSTITUTION:An optically active amino acid (e.g. L-methionine) expressed by formula I (R1 is alkyl or aralkyl; R2 to R4 are H or 1-3C alkyl) is reduced into thio anions in liquid ammonia or an amine solvent with an alkali metal. an alkyl halide (e.g. <13>C-labeled methyl iodide) expressed by formula II (R5 is alkyl having at least one carbon labeled with <13>carbon; X is halogen) is then reacted with the resultant product to afford <13>carbon-labeled optically active methionine or a homolog hereof (e.g. L-methionine in which C in the terminal methyl group is <13>carbon) expressed by formula III. The subject compound can be obtained in good yield in a short process according to the aforementioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing optically active methionine labeled with carbon-13 or its analogues, and this compound can be used in biosynthesis and metabolic research or in methylmalonic acid blood production. It is useful for diagnosing metabolic disorders such as schizophrenia.

[Conventional technology]

Optically active methionine labeled with carbon-13 is a known compound and is used for the above-mentioned purposes. However, not only is this compound very expensive, but most of the congeners other than methionine are difficult to obtain.

The general method for producing optically active methionine is, first, L-
In this method, a mixture of methionines is obtained and then optically resolved. For example, as shown in British Pat. This is further reacted with ammonia and hydrolyzed to obtain methionine. Since this methionine is a mixture of 0-isomer and L-isomer, it is separated by selective hydrolysis using acylase. Therefore,
In order to obtain methionine labeled with carbon-13, it is necessary to synthesize it through the synthetic route described above using a reagent in which at least one of the carbons constituting acrolein, mercaptan, and hydrocyanic acid is labeled with carbon-13. However, this method not only requires a large number of routes, but also has the drawback of requiring the use of large amounts of expensive carbon-13-labeled reagents, which makes it expensive.

[Problems to be Solved by the Invention] An object of the present invention is to obtain a carbon-13-labeled optically active methionine or a homologue thereof in good yield by a simple route.

[Means to solve the problem]

The present invention relates to the general formula (I) R2R3R4 R+S CHCHCC00H NH2(I) (However, R1 represents an alkyl group or an aralkyl group, and R
2, R3 and R4 represent hydrogen or an alkyl group having 1 to 3 carbon atoms, and these may be the same or different) in liquid ammonia or an amine solvent, After reduction to a thioanion using an alkali metal, the general formula (I[)R5X
(II) (However, R5 is small (tomo-
carbon represents an alkyl group labeled with carbon-13,
(represents a halogen atom) General formula (ITJ) R2R3R4 R55-CH-CH-C-C00H NH2(I[) (However, R5 has at least one carbon represents an alkyl group labeled with carbon 13, R2, R3 and R1 represent hydrogen or an alkyl group having 1 to 3 carbon atoms, which may be the same or different) This is a method for producing labeled optically active methionine or its analogue.

The optically active amino acid used as a raw material in the present invention is represented by the general formula (I), where R1 represents an alkyl group or an aralkyl group, and R2, R3, and R4 are hydrogen or have 1 to 3 carbon atoms. represents an alkyl group, which may be the same or different. As R1,
Examples include methyl group, ethyl group, propyl group, benzyl group, etc., and examples of R2, R3 and R4 include hydrogen, methyl group, ethyl group, and propyl group. Specifically, L-methionine, D-methionine, L-3-methylmethionine, I)-
Examples include 2-methylmethionine.

The optically active methionine labeled with carbon-13 or its homolog obtained in the present invention is represented by the general formula (III), where R5 represents at least one carbon
3 indicates a labeled alkyl group, R2, R3 and R4
represents hydrogen or an alkyl group having 1 to 3 carbon atoms, and these may be the same or different. Examples of R5 include methyl group, ethyl group, propyl group, butyl group, etc., and examples of R2, R3 and R4 include hydrogen, methyl group,
There are ethyl and propyl groups. Specifically, L-methionine, D-methionine, L-3-methylmethionine, D-2-methylmethionine, etc. in which the terminal methyl group is labeled with 13 can be mentioned.

The production of methionine or a homologue thereof of the present invention is carried out as follows. As the optically active amino acid represented by the general formula (I), commercially available L-methionine and synthesized methionine analogs can be used. Since this is not labeled with carbon-13, it can be easily obtained or synthesized. This optically active amino acid is reduced to a thioanion by reacting with an alkali metal while dissolved in liquid ammonia or an amine solvent. The amount of liquid ammonia or amine solvent to be used may be any amount sufficient to dissolve the amino acid, and is suitably between 10 and 100 times its weight. As the alkali metal, lithium or sodium is preferable, and the appropriate amount to be used is about 1 to 10 times the molar amount of the amino acid, and it is preferable to add it gradually in small amounts. The reaction temperature is within the range necessary for the solvent used to remain liquid; however, in the case of liquid ammonia,
℃ or less is 20℃ for methylamine or ethylamine
A temperature of approximately This reaction is carried out by stirring for about 0.5 to 3 hours after adding the alkali metal. To complete the reaction, a part of the reaction solution is collected and its 'H-NMR is measured, and a signal of an alkyl group such as a terminal methyl group or an aralkyl group (for example, δ2 derived from the methyl group of L-methionine) is detected. This can be confirmed by checking the disappearance of .Ippm).

In addition, when carrying out this reaction, if a regulator such as ferric chloride is added, preferably 0.1
Addition of ~5 times the molar amount will adjust the reducing power and increase the production of thioanions.

For the thioanion obtained in this reaction, the general formula (II
) An alkyl halide represented by R5X is added and reacted. Here, R5 represents an alkyl group in which at least one carbon atom is labeled with carbon-13, X represents a halogen atom, and the alkyl halide represented by the general formula (n) is methyl iodide. , ethyl iodide, methyl bromide, ethyl bromide, etc. And for example, carbon-13
Labeled methyl iodide can be easily synthesized in large amounts from Co, which is the basic compound of the carbon-13 labeled compound, via methane.

The reaction with the alkyl halide can be carried out in the same solvent as above, and the reaction temperature may be in the same range, but the amount of proton donor such as ammonium chloride in the solvent is about 1 to 2 times the mole of the amino acid. It is desirable to add. Examples of proton donors include alcohols in addition to ammonium salts. This reaction is carried out by gradually dropping the alkyl halide under stirring conditions and stirring for about 0.1 to 1 hour. Further, it is preferable that these reactions in general be carried out under an atmosphere of an inert gas such as nitrogen or argon.

After the reaction is completed, the liquid ammonia or amine solvent is removed by means such as vaporization separation, and the product is taken out. Since this product contains side reaction products, reaction additives, etc., it is separated to obtain methionine represented by general formula (III) or its homolog. Separation can be carried out, for example, by dissolving the product in water, filtering off insoluble matter, concentrating it under reduced pressure and drying it to precipitate crystals.Purification can be carried out by dissolving these crystals in ethanol. This can be carried out by recrystallizing, then washing with ether, and drying.

According to the production method of the present invention, optically active methionine labeled with carbon-13 and represented by general formula (I) or its homologue can be produced almost quantitatively from a common optically active amino acid.

〔Example〕

Examples of the present invention will be shown below.

Example 1 5 with dry ice-methanol condenser installed
A 007nl three-sided flask was immersed in a dry ice methanol bath, 1.8g of L-methionine and 80d of liquid ammonia were added to the flask, and after stirring, 0.60g of metallic lithium was added, and then ferric chloride was added to the microspermide. and continued stirring for 1.5 hours. The color of the reaction solution changed from initially colorless to blue and then to gray. A part of the reaction solution was taken out and subjected to 'H-NMR (D20
) and found that δ2. Since a signal was observed at ippm, 0.03 g of lithium was added and 1
．． Stirring was continued for 5 hours. Similarly, 'H-NMR(D
20), it was found that the signal disappeared at δ2 and lppm, so the reaction was terminated.

While maintaining this flask at -78°C, 0.65 g of ammonium chloride was added, followed by 2 g of carbon-13 labeled methyl iodide, and the mixture was further stirred for 3 hours to carry out the reaction.

Thereafter, the flask was taken out of the bath, the condenser was removed, and the flask was left at room temperature overnight to vaporize and remove the ammonia.

The obtained white crystalline product was dissolved in pure water and filtered through Celite, and the filtrate was concentrated under reduced pressure and dried to obtain light brown crystals. The crystals were dissolved in a small amount of pure water, the pH was adjusted to 5 with dilute hydrochloric acid, and the solution was again concentrated under reduced pressure to dryness to obtain light brown crystals. This was heated and dissolved using ethanol and then cooled to precipitate white crystals. After storing this at 4°C overnight, it was centrifuged, and the separated crystals were washed with ether and dried to obtain 0.843 g of white crystals. In addition, the mother liquor separated by centrifugation was concentrated under reduced pressure and dried to obtain yellow crystals, which were then recrystallized using ethanol in the same manner as above, and then washed with ethanol and ether. , and dried to obtain 0.862 g of white crystals.

When 0.843 g of the white crystals and 0.862 g of the white crystals were measured by 'H-NMR (D20), 99 atom% of the carbons in the terminal methyl groups were carbon-13.
It was confirmed that it was monomethionine.

Yield 94%.

Measurement results mp: 270°C 'H-NMR: 2. 10ppm (3H, d, J
”'C-) (=139Hz.

3CH3), a C-H cup link was observed.

3C-NMR (D20. 100MHz, Ref,
dioxane): 14, 7 ppm ("'CH
3S) MS: m/z 150 (M-, 63%)
, m/z 62 (100%) [Effects of the Invention] According to the production method of the present invention, carbon 1 can be produced in high yield in a short process.
Optically active methionine labeled with 3 or a homolog thereof can be obtained.

Patent applicant: Nippon Steel Chemical Co., Ltd.

Claims (1)

[Claims] (1) General formula (I) ▲Mathematical formulas, chemical formulas, tables, etc.▼(I) (However, R_1 represents an alkyl group or an aralkyl group,
R_2, R_3 and R_4 represent hydrogen or an alkyl group having 1 to 3 carbon atoms, and these may be the same or different) in liquid ammonia or an amine solvent, After reduction to a thioanion using an alkali metal, the general formula (II) R_5X (II) (wherein R_5 represents an alkyl group in which at least one carbon is labeled with carbon 13, and X represents a halogen atom)
General formula (III), which is characterized by reacting with an alkyl halide represented by and R_2, R_3 and R_4
represents hydrogen or an alkyl group having 1 to 3 carbon atoms, and these may be the same or different)
A method for producing optically active methionine labeled with or a homolog thereof.