JPS6112899B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides N-(α-hydroxyalkanoyl)-
The present invention relates to a method for producing a peptide, and specifically relates to a method characterized by reacting an α-hydroxycarboxylic acid and an α-amino acid by heating them to a temperature equal to or higher than the melting point of the former. N-(α-hydroxyalkanoyl)-peptides are attracting attention for their biological and pharmacological activities such as antiviral, antibacterial, and antifungal effects, and are useful substances in fields such as agricultural chemicals and antifungal paints. As for its industrial production method, no fully satisfactory method has yet been found. As a result of various studies, the present inventors found that the diketopiperazine ring partially opens in a thermal reaction in the presence of an α-hydroxy acid to generate an N-(α-hydroxyalkanoyl)-dipeptide. Since the yield of the target product is relatively low in this reaction method, we continued to conduct research to improve this method, and as a result, we completed the method of the present invention. That is, the method of the present invention mixes α-hydroxycarboxylic acid and α-amino acid in an appropriate ratio to produce α-
When heated to a temperature above the melting point of the hydroxycarboxylic acid and reacted with stirring until a homogeneous phase is formed, a dehydration condensation reaction easily occurs, yielding one or a mixture of N-(α-hydroxyalkanoyl)-peptides, This is based on the knowledge that this reaction mixture is highly soluble in water and can be easily separated from unreacted α-hydroxy acids and amino acids by treatment with an ion exchange resin. It has the advantage of being easy to produce, with high yield, and at low cost. At first glance, the method of the present invention appears to be a simple peptide synthesis method, but if we consider the following points surrounding this reaction, it appears to be a fairly specific reaction. For example, (1) This reaction uses α-hydroxycarboxylic acid as a raw material, but this reaction does not occur with β-hydroxycarboxylic acid, even if the same hydroxy acid is used. That is, even if β-hydroxycarboxylic acid and α-amino acid are mixed and heated, the dehydration condensation reaction does not proceed.
Amino acids are difficult to dissolve. If the reaction is forced to proceed at a higher temperature and heated for a longer period of time, an unknown substance that is completely different from the intended target product will be produced. (2) α-Hydroxycarboxylic acids are known to easily cyclize themselves into glycolide derivatives when heated, and α-amino acids are said to similarly easily become diketopiperazine derivatives when heated. . However, when an α-hydroxycarboxylic acid and an α-amino acid are coexisting and heated, such a cyclization reaction is suppressed and a chain-like condensate as shown is obtained. (3) When a hydroxy acid and an amino acid undergo a dehydration condensation reaction between molecules, there are two possibilities for the reaction (bonding), and it is not necessarily certain which one takes priority. That is, the reaction between a hydroxy acid and an amino acid involves a) formation of an ester bond through dehydration condensation between the hydroxyl group of the hydroxy acid and the carboxyl group of the amino acid, and b) formation of an ester bond between the carboxyl group of the hydroxy acid and the amino group of the amino acid. Although there are two possibilities of forming an amide bond through dehydration condensation between It becomes a reaction. Furthermore, condensation between hydroxy acids and amino acids can be suppressed. Note that the N- produced in the first stage condensation reaction
The terminal carboxyl group of the (α-hydroxyalkanoyl)-amino acid tends to be easily condensed with the next amino acid. As described above, this reaction is a) a reaction specific to α-hydroxy acids, b) condensation between the same molecules,
The cyclization reaction is difficult to occur, and the reaction proceeds exclusively between different molecules, and c) the condensation reaction has directionality and selectivity.
It is widely applied as a method for producing precursors for the synthesis of various peptides with pharmacological activity, or for the synthesis of polypeptides with larger molecular weights, antibiotics, etc. To explain the method of the present invention in more detail below, the α-hydroxycarboxylic acid used as a raw material has the general formula HO-CHR ₁ -COOH (wherein R ₁ is a hydrogen atom or a straight carbon number having 1 to 25 carbon atoms). (Represents an alkyl group having a chain or side chain.)
Specifically, for example, glycolic acid, lactic acid, α-oxybutyric acid, α-oxyvaleric acid,
Typical examples include α-oxycaproic acid, α-oxypalmitic acid, α-oxydocosanoic acid, α-oxyhexacosanoic acid, α-oxybutanoic acid, α-oxymethylpentanoic acid, α-oxymethylhexanoic acid, etc. Can be mentioned. In addition, α-amino acids have the general formula H ₂ N-CHR ₂ -COOH (where R ₂ is a hydrogen atom or an alkyl group containing a heteroatom such as an alkyl group, an alkenyl group, a cycloalkyl group, an oxygen, sulfur, or a nitrogen atom). , an alkenyl group, or an amino acid residue such as a cycloalkyl group, allyl group, or aralkyl group), specifically, for example, glycine, alanine, valine, leucine, isoleucine, serine, threonine, lysine. , arginine, cysteine, methionine, phenylalanine, tyrosine, proline, hydroxyproline, histidine, tryptophan, sarcosine, α-methylalanine, ornithine, homoserine, and dopa. The ratio of α-hydroxycarboxylic acid and α-amino acid used is usually a stoichiometric amount with a molar ratio of 1/1, but if necessary, it is possible to use a slight excess of either component. There is no problem.
The reaction is carried out at a temperature above the melting point of the α-hydroxy acid, preferably
The reaction is carried out by heating at 100° C. or higher and 180° C. or lower for 10 minutes to several hours. At this time, it is preferable to sufficiently stir the reaction solution and conduct the reaction in an inert gas atmosphere. As the reaction progresses, the solid content gradually dissolves and becomes a homogeneous liquid at the end of the reaction. The reaction product is highly soluble in water, and unreacted raw materials can be easily separated using an ion exchange resin or other separation and purification means. Hereinafter, representative examples of the method of the present invention will be shown and explained in more detail. However, it goes without saying that these examples are merely illustrative and the method of the present invention is not limited to these. Of course, various implementations can be made within the scope. In the examples, "%" means "% by weight". Example 1 9.0 g (0.1 mol) of lactic acid and 18.9 g (0.1 mol) of valine were mixed, sealed in a glass reaction tube purged with nitrogen, heated in an oil bath at 160°C for 30 minutes, and allowed to react. It became a homogeneous liquid. When the reaction product was dissolved in water and analyzed by high performance liquid chromatography, the conversion rate of lactic acid was 62.5%, and the conversion rate of lactic acid was 62.5%.
-Hydroxypropionyl)valine selectivity is 80
It was %. Example 2 9.0 g of lactic acid and 8.9 g (0.1 mol) of alanine were mixed, sealed in a glass reaction tube purged with nitrogen, heated in a 150°C oil bath for 30 minutes, and allowed to react. The reaction solution became a homogeneous liquid. Summer. When the reactant was dissolved in water and analyzed by high performance liquid chromatography, the conversion rate of lactic acid was 73% and the selectivity of N-(α-hydroxypropionyl)-alanine was 49%.
In addition, 31% each of N-α-hydroxypropionyl)-alanylalanine and N-(α-hydroxypropionyl)-alanylalanylalanine,
It was produced with a selectivity of 20.5%. Comparative Example 10 g (0.1 mol) of β-hydroxy n-butyric acid and 8.9 g of alanine were mixed and a reaction was carried out in exactly the same manner as in Example 1. However, the reaction did not proceed slowly, and 1.0 hours after the start of heating, the reaction was carried out in an oil bath. When the temperature was raised to 180°C and the reaction was continued for 1 hour, a homogeneous reaction solution was finally obtained. The reaction mixture was dissolved in water and analyzed by high performance liquid chromatography, but no hydroxyalkanoyl peptide was obtained, and only the production of a substance of unknown structure was confirmed. Example 3 2-Hydroxy-3-methyl-pentanoic acid 13.2
g (0.1 mol) and glycine 7.5 g (0.1 mol) were mixed, sealed in a glass reaction tube purged with nitrogen, and heated at 140°C.
After heating and reacting in an oil bath for 30 minutes, the reaction solution became a homogeneous liquid. When the reaction product was dissolved in water and analyzed using high performance liquid chromatography, 2-
The conversion rate of hydroxy-3-methyl-pentanoic acid is
The selectivity for N-(2-hydroxy-3-methyl-pentanoyl)-glycine was 56%. In addition, N-(2-hydroxy-3-methylpentanoyl)-glycylglycine and N-(2-hydroxy-3-methylpentanoyl)-diglycylglycine were produced with selectivities of 26.7% and 17.3%, respectively. . Examples 4 to 8 Various α-hydroxy acids and amino acids were reacted in the same manner, and the following results were obtained. 【table】

Claims (1)

[Claims] 1. A method for producing an N-(α-hydroxyalkanoyl)-peptide, which comprises reacting an α-hydroxycarboxylic acid and an α-amino acid by heating them to a temperature equal to or higher than the melting point of the former.