JPS58124750A - Preparation of n-acyl-l-carnosine - Google Patents

Abstract

PURPOSE:To obtain the titled compound useful as a drug in high yield, by acylating L-carnosine with an acyl donor under specific conditions. CONSTITUTION:L-Carnosine is acylated with an acyl donor such as carboxylic acid anhydride, etc. shown by the formula (RCO)2O or RCOCl (R is alkyl, etc.) under basic conditions in an alkali aqueous medium (e.g., sodium hydroxide, etc.) with keeping pH 9-13.5 and the reaction temperature at about 5-25 deg.C, to give the desired compound. An inorganic base, etc. such as NaOH, etc. is used for the basic conditions. EFFECT:Racemization and side reactions caused by the acylation of N on the imidazole nucleus in histidine are completely suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for the production of N-acyl-cytolunosine.

N-acyl-silicone has a styrene structure in N-acyl-β-alanyl-L-, and is similar to carnosine (it has a strong inhibitory effect on the limbic system and is useful as a medicine). be.

The aluminum salt also has excellent anti-crush properties.

Conventionally, methods for producing N-anlucarno/one using L-lunosine as a starting material include A, Ca1l and G, C1.
ty is J, Org, Chom, +26. 61
7 (1961)) reported that N-7 cetylcarnosine was obtained by acetylating lunosine with acetic anhydride in glacial acetic acid.

However, when the present inventor tried this known method again,
As is clear from Reference Example 1 below, the raw material carnosine is racemized, and the nitrogen atom in the imidazole nucleus of histidine is also 7-cetylated at the same time, which tends to produce by-products. confirmed.

Therefore, as a result of a detailed study of the acylation conditions of L-carnosine, the present inventor found that L-carnosine was acylated in an alkaline aqueous medium with a pH value of about 9 to 13.5 and a reaction temperature of about 5 to 25C. When the reaction is carried out, side reactions due to racemization and acylation of the nitrogen atom on the imidazole nucleus in histidine are completely suppressed, and the desired N-acyl-carnosine can be obtained in high yield. They discovered this and completed the present invention.

That is, in the present invention, when producing N-acylcarnosine by reacting L-acylcarnosine with an acyl donor, the reaction temperature is about 5 to 25C in an alkaline aqueous medium at a pH of about 9 to 13.5.
The acylation reaction is carried out while maintaining the N
This is a method for producing -acyl-silicyl-lunosine.

In the present invention, a carboxylic acid anhydride represented by the general formula (RCO), O (wherein R is an alkyl, aryl, or aralkyl group) or a general formula RCOCI ( However, carboxylic acid chlorides represented by the formula (R in the formula represents an alkyl, aryl, or 7-ralkyl group) are preferably used, and representative examples thereof (represent acetic anhydride, propionic anhydride, formic acid-acetic acid mixed acid anhydride, acetyl chloride) are preferably used. , propionyl curlide,
Examples include benzoyl chloride and phenylacetyl chloride.
Hydrochloride may be used. Generally, the reaction is carried out using an aqueous solution of L-fluorinone or a mixed solution of water and an aqueous organic solvent, under basic conditions, with the acyl donor as it is or dissolved in an organic solvent. It is done by adding. As the water-soluble organic solvent, for example, acetone, acetonitrile, methanol, etc. are used, and as the organic solvent, for example, acetone, 7-cetonitrile, coulloform, dichloromethane, ethylene dichloride, methyl isobutyl ketone, etc. are used.

As basic conditions, an inorganic base such as sodium hydroxide or potassium hydroxide or an organic base such as triethylamine, trilobylamine or pyridine is used to adjust the pH of the reaction medium to 9.0 to 13.6, preferably 11.5. ~13
．． 5, thereby suppressing side reactions as much as possible and obtaining the desired N-acyl-carnosine in high yield.

In order to maintain the above pH range during the reaction, it is preferable to add the 7 mil donor and the base solution to the L-carnosine solution at the same time.

The reaction temperature is desirably 25C or less, preferably 5-10r.

Since L-carnosine is generally more expensive than the acyl donor, an excess of the acyl donor is used to drive the reaction to completion. Preferably 1.1 to 1.5 times the molar amount of reed! A donated body is used.

After the reaction is completed, the reaction mixture is treated with, for example, Diaion 5K-I.
B, Amberlight IR-120, Tauex 50W
When treated with a strongly acidic ion exchange resin 111 (H-type) such as 111 (H-type), the target substance is adsorbed to the resin, so it can be effectively combined with carboxylic acids and inorganic substances generated by hydrolysis of unreacted acyl donors. It is separated into Then, the resin was eluted with aqueous ammonia, concentrated and deammoniated, and Ampara () IR
A highly pure target product can be easily obtained by passing through a weakly acidic ion exchange tree 111 (H-type) such as C-60 to remove a small amount of unreacted carnosine and ammonia remaining. Alternatively, the desired product can be easily extracted (desalted) by electrodialyzing the reaction mixture or concentrating the residue with a water-soluble solvent such as methanol. Then, if necessary, Resin treatment may also be performed.

The N-acyl-cytolunosine thus obtained has a sufficiently high purity as it is, but it can be made into a purified product by further crystallizing it from a water-itubrobanol mixed solvent.

Examples and reference examples (described in more detail below).

Example 1 L-carnosine 90.4 F (0.40 mol) was added to 2
N-hydroxide) IJium aqueous solution 200-F-dissolved,
This solution was added under stirring at a reaction temperature of 5C to 10C and a pH of 1.
48.6 f (0.44 mol) of 96-acetic anhydride and 260 d of a 2N aqueous sodium hydroxide solution were simultaneously added dropwise while maintaining the mixture in the range of 3.0-13.5. After the dropwise addition was completed, the reaction product was stirred at the same temperature for 1 hour and analyzed by silica gel thin layer chromatography.
The presence of cetylcarnosine was observed, but the presence of the raw material carnosine and the byproduct im* N-7 cetyl-N-7 cetylcarnosine was not observed (*indicates the nitrogen atom on the imidazole nucleus in histidine). . This reaction solution was passed through a strongly acidic ion exchange resin Diaion 5KIB to adsorb N-7 cetylcarnosine, then washed with water until neutral, and eluted with IN-ammonia water. was concentrated to 200-. Add acetic acid to this concentrated solution to adjust the pH.
After adjusting 4J OF, 780- of inpropyl alcohol was added while maintaining the temperature of this solution at 50C.

After stirring at the same temperature for 3 hours and further stirring at C20C for 1 hour, the precipitated crude N-7 cetyl-carno-7 was dried.
Obtained 86.6F. Its specific optical rotation is (α ru + 26.l
o (C-3, water).

Crude N-7 Cetyl-Carnosine 86.6F to 10% Water
After dissolving 4+a/F- and decolorizing it by adding 0.82 g of activated carbon, 780 d of inpropyl alcohol was added while maintaining this decolorizing solution as Cr-. After stirring at the same temperature for 3 hours and further stirring at c20t:' for 1 hour, the precipitated N-7
One carton of cetyl was dried to obtain 82.4.

The thus obtained N-7 cetyl monomer was analyzed for IR% NMRE, and as a result, it completely matched with the standard product. In addition, analysis by gel thin-coomatography revealed a single spot. Also, its specific optical rotation is [α)”: = + 26.20 (C-3, water)
It was confirmed that the results matched with the standard sample, and that no racemization occurred during acetylation after washing with water.

Silica gel thin layer chromatography analysis uses a silica gel 60 thin layer plate made by Merck, and after developing with a mixed solvent of ethyl acetate:acetic acid:water-2+1:1, iodine? Detection was performed from this. Under these conditions, the Rf values of the compounds diacetylcarnonone, acetylcarnosine, carnosine, and histidine were 0.43.0.36.0.22.0.
It was 27.

Example 2 L-lunosine 22.6 f (0.10 mol) in 2N
-Dissolve 55 sllE of aqueous solution of (s)lium hydroxide and adjust the pH
was adjusted to 13.3Ct14. To this solution, 14.0 f (0,132 mol) of 96-thi acetic anhydride and 901 I/2N sodium hydroxide solution were simultaneously added dropwise over 1.6 hours while stirring. During this time, the pH of the reaction solution was 12.6-13.5f.
m, and the reaction temperature was maintained at 18-20C. After the dropwise addition was completed, the reaction product was stirred at the same temperature for 1 hour, and the reaction product was analyzed by silica gel thin layer chromatography, and it was found that the target product N-7 cetylcarnosine was produced, but the raw material carnosine and the byproduct N -7 cetyl-N+m-7 cetylcarnosine was not observed. This reaction solution was treated with a strongly acidic ion exchange resin, pH adjusted, and water-itubrobanol crystallized in the same manner as in Example 1, followed by N-7 cetyl to obtain monocarnosine 21.2F. Its specific optical rotation is [α]
,,+26. lo (C=3, water) and therefore no racemization occurred.

Example 3 33.9 f (0.16 mol) of L-carnosine in 1 mol of water
The pH was adjusted to 12.5 by adding a CN-sodium hydroxide aqueous solution of approximately 83% to the benzoyl solution. 100wI of an acetone solution containing 26.2t of chloride and a 2N aqueous sodium hydroxide solution were simultaneously added dropwise.

During the dropwise addition, the pH of the reaction solution was maintained at 11.5 to 12.6. After the dropwise addition was completed, the acetone was stirred at room temperature for 30 minutes, and then the acetone was distilled off under reduced pressure, 100+w/ of water was added, and the following treatment was carried out in the same manner as in Example 1 to obtain N-benzoyl-L-*L/
Crystal of Shin 38. Obtained OF. This stuff has a melting point of 216~
218c, and the specific optical rotation is [α), −+ I O(C
-3, H, O), and no racemization was observed.

Moreover, both IR and NMR were consistent with the standard product. Even thinner p
Madographic analysis showed only a single spot.

Reference example 1 ^, Co11 and G, C1ty, J, O
rg, Chem, 26 +617 (1961)
According to the method described above, 10.6F of L-carno/one was suspended in 30F of glacial acetic acid, and 8.5f of acetic anhydride was gradually added to it while stirring.
It was added dropwise at 25°C.

After washing, the reaction solution was stirred at room temperature overnight to obtain a homogeneous and transparent solution. The reaction solution was concentrated under reduced pressure to obtain a syrup (100% water was added and further concentrated under reduced pressure. This operation was performed twice. The resulting aqueous solution was analyzed by silica gel thin layer chromatography. Although the presence of the raw material lunosine was not observed, the presence of the target product N-7 cetyl carnonone was excluded.
The presence of 7 cetylcarnonone was recognized. Similar to Example 1, this reaction solution was prepared using the strongly acidic ion exchange resin Diaion 5KI.
B treatment, water-inpropanol crystallization treatment, N-7
Cetylcarnosine 7.82 was obtained.

This substance shows no specific rotation ([α) knee 0 (C-
3. Water)) was completely [racemic].

Reference example 2 L-carnosine 22.6 F (0.10 mol) in water 2
00 t/r-dissolved and this solution was dissolved in 96% acetic anhydride at 42.5 F (0,
40 mol) was added dropwise. After stirring at the same temperature for 2 hours after the dropwise addition, the reaction product was analyzed by silica gel thin layer chromatography, and it was found that in addition to the target N-7 cetylcarnonone, there was unreacted carnosine and 1 lll of N-7cetyl-N10-7cetylcarnonone. The formation of 7 ions was observed.

This reaction solution was treated with a strongly acidic ion exchange resin Diaion 5K-IB in the same manner as in Example 1 to remove the by-product N-7 cetyl-Nlm-acetylcarnosine. Furthermore, in order to remove unreacted carnosine, the eluate was applied with weakly acidic ion exchange resin Ampara C-50IC, and then washed with water until it became neutral. Combine the flow-through liquid and washing liquid and boil under reduced pressure at E 30.
It was concentrated to wrl. After that, the same operation as in Example 1 was carried out, and N-acetyl-carnosine water)) Therefore,
It is thought that partial racemization occurs during the acetylation process.

Reference example 3 L-lunosine 22.6 F (0.10 mol) in water 1
00 scrap/C, and this solution (under stirring, reaction temperature 5
~! 0r1 and the pH of the reaction solution is in the range r of 7.0 to 7.4.
- 50 ml of an aqueous solution containing 16.6 F of 96-thiacetic anhydride and 15.9 F of sodium carbonate was simultaneously added dropwise. After dropping, stir at the same temperature for 1 hour, then adjust the pH with acetic acid.
5. Adjusted Oc. When the reaction product was analyzed by silica gel thin layer chromatography, it was found that in addition to the target N-acetylcarnosine, unreacted carnosine and by-product N
-7 cetyl-Nim-7 cetylcarnosine was observed to be produced. This reaction solution was subjected to the same operation as in Reference Example 2, and N-7
After setting it up, Ichiriki Runon got 18.5 f.

The N-7 cetylcarnonine thus obtained had a specific optical rotation [α bow'-+21.45 (3.H, O on day 0), which did not match that of the standard product. Therefore, it is considered that partial racemization occurs during the acetylation step.

The reaction conditions and results obtained in Examples 1 to 3 and Reference Examples 1 to 3 are collectively shown in Table 1. As is clear from the same table, according to the method of the present invention, the reaction proceeds smoothly,
F-targeted N-7 nor-L- without any racemization
It will be appreciated that carnosine can be obtained in good yield.

Claims (1)

[Claims] (1) By reacting L-carnosine with an acyl donor, N-
When producing N-acyl-carnosine, the acylation reaction is carried out in an alkaline aqueous medium while maintaining the pH at about 9-13.5 and the reaction temperature at about 5-26r. Manufacturing method. In the patent claim, the acyl donor is a carboxylic acid anhydride or carboxylic acid chloride represented by the general formula (RCO)s O or RCOC+ (wherein R represents a furkyl, aryl, or aralkyl group) Scope (Production method according to claim 11. Ill Claim in which the acyl donor is acetic anhydride. i Production method according to claim 11. (41 Claim in which the acyl donor is benzoyl chloride (Production method according to claim 11) Manufacturing method. (51 Claim in which the alkaline aqueous medium is an aqueous sodium hydroxide solution or a mixed solvent of an aqueous sodium hydroxide solution and a water-soluble organic solvent +11, (!), (II or (4)
Manufacturing method described in section.