Preparation method for high-purity D,L-2-hydroxyl-4-methylthiobutyrate

Abstract

The invention discloses a preparation method for high-purity D,L-2-hydroxyl-4-methylthiobutyrate. The preparation method comprises the following steps: first, D,L-2-hydroxyl-4-methylthiobutyronitrile and pyridinemethanol are employed as reaction materials, and Pinner salt is generated; second, unreacted pyridinemethanol in the system in the first step is evaporated and removed, then water is added, and a mixed liquid D,L-2-hydroxyl-4-methylthiobutyrate and ammonium chloride is obtained; third, water in the system in the second step is removed through condensation, ammonium chloride is removed through centrifugation, and D,L-2-hydroxyl-4-methylthiobutyrate is obtained. The reaction conditions are mild, the technology is simple, products are easy to separate, and the residual problem of D,L-2-hydroxyl-4-methylthiobutyric acid and polymers in the product D,L-2-hydroxyl-4-methylthiobutyrate is solved. The purity and the yield of the product are higher than the purity and the yield of a product obtained through the prior art, and additional organic solvents are not needed in the whole process.

Description

technical field [0001] The invention relates to a preparation process of a protective methionine hydroxy analog, in particular to a preparation method of high-purity D,L-2-hydroxy-4-methylthiobutyrate. Background technique [0002] Although methionine hydroxy analogs can promote fiber degradation and the growth of acetic acid, they are easily degraded by microorganisms in the body, and have a short residence time and low utilization rate in the body, so it is necessary to protect them. The protection of methionine hydroxy analogs mainly adopts the esterification reaction of D,L-2-hydroxy-4-methylthiobutyric acid and alcohol to prepare the protected methionine hydroxy analogs. D, L-2-Hydroxy-4-methylthiobutyrate, also known as hydroxymethionine ester, is one of the basic units of protein and the only sulfur-containing amino acid among essential amino acids. It is rumen-protected methionine. The feeding of dairy cows can increase the milk production and milk quality of dairy ...

AI Technical Summary

Problems solved by technology

U.S. Patents US3761518 and US3850987 disclose that under the catalysis of hydrogen chloride, D,L-2-hydroxy-4-methylthiobutyrate (calcium salt, sodium salt, potassium salt, ammonium salt, etc.) and alkyl alcohol (methanol , ethanol, isopropanol, butanol, etc.) to prepare high-purity D,L-2-hydroxy-4-methylthiobutyrate technical scheme; the process operation is complicated, especially the raw material D,L-2- Preparation of hydroxy-4-methylthiobutyrate, that is, D,L-2-hydroxy-4-methylthiobutyronitrile is hydrolyzed with sulfuric acid, neutralized with ammonia, and desalted to obtain 88% of D,L-2- Aqueous solutions of hydroxy-4-methylthiobutyric acid monomers, dimers and polymers in which the monomer content is 65%, the dimer and polymer content is 23%, and the water content is 12%, in order to obtain Monomer D,L-2-hydroxy-4-methylthiobutyric acid needs to be hydrolyzed by adding alkali to obtain D,L-2-hydroxy-4-methylthiobutyrate, while D,L- Under the action of hydrogen chloride, 2-hydroxy-4-methylthiobutyrate will be converted into D,L-2-hydroxy-4-methylthiobutyric acid, D,L-2-hydroxy-4-methylthio The butyric acid part is polymerized again to form dimers and polymers, which will lead to low purity of the product and low esterification rate of D, L-2-hydroxy-4-methylthiobutyric acid, D, L -2-Hydroxy-4-methylthiobutyrate in low yield

[0007] This shows that D, the preparation method of L-2-hydroxyl-4-methylthiobutyrate still needs to be improved

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