DE1543868A1 - Improved Process for the Production of N-Acetylasparagine - Google Patents

Description

ÖOCIETE DE HlODUITS CHIHIQUES ET DE SYSiPHESE in BezoiosCVal d'Oise) / France

Improved Process for Making N-Acety 1-

asparagine

The invention relates to a new, improved process for the preparation of II-acetyl-1-asparagine.

The acetylation of the nitrogen atom of ^ C-amino acids, which is carried out frequently, aims to provide functional protection in the synthesis of peptides. aside from that sometimes result from acetylated derivatives of amino acids their interesting pharmacodynamic properties to use.

As in the case of carbobenzoxylation, sulfonylation or benzoylation using the corresponding chlorides

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For the acetylation of amino acids, the Schotten-Baumann's reaction or its modifications were almost always used, for example using acetyl chloride or acetic anhydride in a highly diluted state, e.g. in an ether or benzene protective phase. In the aforementioned process, the pH value of the initial aqueous amino acid solution is generally obtained by simultaneously adding a dilute sodium hydroxide solution or soda solution.

The aforementioned method has been recommended in the specialist literature in the case of glutamic acid and aspartic acid, of tyrosine, cystine, leucine, tryptophan, arginine, g-lutamine, asparagine, etc. and numerous polypeptides. The same process was also used for the preparation of chloroacetyl derivatives. However, the process has the disadvantage that large amounts of water and organic solvents are necessary. In addition, in the case of a soluble acetylation product, the purification of the same is particularly difficult (evaporation of the solvents, separation of the salts, removal of the substance, etc.). This is the case with the manufacture of N-acetyl-asparagins

H ₂ N-CO-CH ₂ -CH-COOH

NH-COCH ₃ .

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Production takes place in accordance with all known processes the aforementioned compound by acetylation in an alkaline water solution. Karrer and locksmith have a 9 ^ alkaline solution of asparagine and excess acetic anhydride, in the absence of one Protective solvent used. After subsequent neutralization by means of sulfuric acid, evaporation of the solvents at a low temperature and separation the raw amount of mineral salts by means of ethyl acetate was able to obtain N-acetyl-asparagine with a yield of $ 60 will. (HeIv. Chim. Aeta., 6 ,, 415, 1923).

Before. recently an analogous process was claimed in British patent 792 576/58, according to which the acetic anhydride is diluted with 15 times the volume of ether. The deposition of the final product was how in the aforementioned procedure, using alcohol as a withdrawal agent carried out.

The known methods have the disadvantage that considerable Amounts of water and organic solvents due to the high solubility of acetyl asparagine come into use. It also prepares the separation of the end product from the mineral salts formed by means of of an organic solvent under reflux, large

0098 13/184 p

Trouble. The aforementioned mineral salts, which mainly consist of Ka ₂ SO, .1OH ₂ O, can represent up to 6 times the weight of acetyl asparagine.

It could also be stated that the application of the known processes on an industrial scale is possible Manufacture of acetyl asparagine lead to poor results because the same thing is strong with byproducts is contaminated.

According to the invention it was recognized * that! -Asparagin means Acetic anhydride can be easily acetylated in an acidic medium. Although the hydrated form of the commercially available Ir asparagine has a very poor solubility in the aforementioned solvent, finds the The reaction takes place continuously, which lasts only a few hours, but under the condition that the starting product is finely ground. It is surprising that the reaction in a heterogeneous medium in which the end product is insoluble, takes place, liur as a result of the change in crystal form, it is evident that the reaction has occurred. The course of the reaction can be checked very easily by a chemical analysis will. For this purpose, a sample is taken, which is spun and washed with alcohol. Afterward

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the free cC-amino group was analyzed using minhydrin. In the presence of free cC amino acid groups creates a purple color. If this color no longer forms, it is proof that the acetylation has ended, so that the reaction product can be separated from the reaction gel by centrifugation.

The aim of the invention is therefore the production of N-acetyl-asparagine by reacting finely divided asparagine suspended in glacial acetic acid with an excess Amount of acetic anhydride.

According to the invention, optically active or racial, finely divided asparagine can be used as raw material, a very pure N-acetyl-asparagine is used obtained in high yield.

The process according to the invention can, as in Example 1, be carried out in the absence of a catalyst.

Example 1;

800 parts by weight of finely ground L-asparagine monohydrate were suspended in 1,600 parts by weight of glacial acetic acid. Under vigorous stirring. 'were then for 15 minutes 1,300 parts by weight of 98 # acetic anhydride were added. The reaction took place with a sudden increase in temperature, which rose to about 3 ° C. after 2 hours. The suspension was vigorously stirred for 2 customers (negative Results in the analysis of cfc amino acids

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then cooled by ninhydrin) to 1O ⁰ C and filtered with a Buchner filter. The thus obtained N-acetyl-L-asparagine \ / urde twice with 800 parts by weight of alcohol, and dried each time in a drying oven at 60 ⁰ C. In this way, a pure product having a melting point 165-166 ⁰ C, which had a rotatory power of ^ Sc / _D = 2.5 ° (c = in water. The yield was 75 #. Ii ° /> found 16 , 12; Ni> calculated = 16.07.

With the aforementioned method, DL-asparagine can also be acetylated. Here, the raceiüische K-acetyl-asparagine Mt was obtained, melting point 166-167 ⁰ C under the same conditions. The yield in this case was

By another method it is possible to carry out the acetylation reaction under the same conditions according to the invention by adding a very small amount of sulfuric acid or an arylsulfonic acid or phosphoric acid to accelerate, whereby the yield is still improved.

Particularly benzene sulfonic acid are used as aryl sulfonic acid, p-Toluenesulfonic acid and the xylenesulfonic acids to use.

BATH ORIGINAL

009813/1845

It v-ur-de tried various acidic catalysts as well To use Friedel-Crafts' catalysts. Part of the same, such as boron fluoride, phosphorus trichloride, phosphorus oxychloride and methanesulfonic acids accelerate the reaction rate, however, do not lead to a higher yield.

Other Qatar's like dry hydrochloric acid, perchloric acid and zinc chloride slightly accelerate the rate of acetylation, but lead to a decrease the yield of acetyl asparagine. However, it was found that when using the aforementioned catalysts for the inventive method in the ver. equal to the known processes in which the aforementioned catalysts are used, nevertheless a higher one Yield is achieved, the reaction rate being a much greater one and the reaction process being a much simpler one is. .

The use of sulfuric acid, arylsulfonic acids and phosphoric acid as a catalyst is preferred according to the invention, without being limited to it.

It should be emphasized that very small amounts of the aforementioned Catalysts, for example from 0.001 to 0.01 mol / mol

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Asparagine, produce good results.

The following examples describe the invention
Process with simultaneous use of catalysts.

Example 2:

100g of finely ground L-asparagine monohydrate were in
Suspended 200 ecm of glacial acetic acid. After vigorous stirring, 135 ml of acetic anhydride, to which 0.005 mol of sulfuric acid had been added, were added to the mixture. The temperature was maintained at 35 to 37 ⁰ O.

After 5 hours the robe with minhydrin was negative
Proof that all of the L-asparagine reacted.
The reaction mixture was ^{cooled at 10 °} C., the acetyl asparagine obtained in this way was spun and washed by pasting in ethanol. The reaction product was then dried in a drying cabinet at 50 ^{° C. until it reached a constant weight.}

In this manner, 93g N-acetyl-L-asparagine were obtained with a melting point of 165-166 ⁰ C. The yield was

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"Under the same conditions, but without the addition of Sulfuric acid as a catalyst, a yield of $ 75 was obtained.

Example 3:

The N-acetyl-asparagine was made under the same conditions, as in Example 2, but with the difference that instead of sulfuric acid 0.005 ^ ol Phosphoric acid was used. The yield of N-acetyl-II-asparagine was 82 #.

Example 4:

The N-acetyl-asparagine was prepared under the same conditions as in Example 2, but with the The difference is that instead of sulfuric acid, 0.002 moles of p-toluenesulfonic acid are used to apply Jam. The yield was

.-10

C09813 / 184S 'bathroom

Claims (6)

Claims 1. Process for the preparation of N-acetyl-asparagine, thereby gekennz ei chnet that finely divided asparagine suspended in glacial acetic acid with a Excess acetic anhydride is caused to react. 2. The method according to claim 1, characterized net that either left-turning or right-turning or racial asparagine is used. 3. The method according to claims 1 and 2, characterized gekennz ei seframe that the reaction between 20 and 100 ⁰ C takes place. 4. The method according to claims 1 to 3 _f thereby marked eichnet that the reaction takes place in a heterogeneous medium in the absence of a catalyst. 5. The method according to claims 1 Ms J _t thereby ge - k ü η η ζ eicbne t that the He & kiioß in one -11- 0098 13/1845 BATH ORIGINAL heterogeneous medium in the presence of a catalyst consisting of 0.001 to 0.01 mol of sulfuric acid, an aryl sulfonic acid or phosphoric acid per mole of asparagine takes place. 6. The method according to any one of the preceding claims, characterized in that the acetylasparagine by pasting and washing with an organic solvent in which it is insoluble, is cleaned. 009813/1845