L-Pyroglutamic acid Usage and synthesis

L-Pyroglutamic acid Usage and synthesis

Introduction: 

    Pyroglutamic acid is 5-oxyproline. It is formed by the dehydration of the α-NH2 group and the γ-hydroxyl group of glutamic acid to form an intramolecular amide bond; it can also be formed by the loss of the acyl group in the glutamine molecule. If the glutathione synthetase is defective, it can cause pyroglutamateemia and a series of clinical symptoms. Pyroglutamateemia is an organic acid metabolic disorder caused by glutathione synthetase deficiency. Clinical manifestations include onset within 12 to 24 hours of onset, progressive hemolysis, jaundice, chronic metabolic acidosis, intellectual disability, etc.; urine contains pyroglutamic acid, lactic acid, and α-deoxy-4-hydroxyacetoacetic acid lactone. Treatment, symptomatic treatment, pay attention to adjusting diet after one year old, etc.

Properties: 

    L-pyroglutamic acid is also known as L-pyroglutamic acid and L-pyrocollagen. The product precipitated from the mixture of ethanol and petroleum ether is a colorless orthorhombic bipyramidal crystal with a melting point of 162-163°C in Chemicalbook. It is soluble in water, alcohol, acetone and glacial acetic acid, slightly soluble in ethyl acetate, and insoluble in ether. The specific rotation is -11.9° (c=2, H2O).

Features and uses: 

    Human skin contains a water-soluble substance with moisturizing function - natural moisturizing factor, which is roughly composed of amino acids (containing 40%), pyroglutamic acid (containing 12%), inorganic salts (Na, K, Ca, Mg, etc. containing 18.5%), and other organic substances (containing 29.5%). Therefore, pyroglutamic acid is one of the main components of the skin's natural moisturizing factor, and its moisturizing ability far exceeds that of glycerol and propylene glycol. It is non-toxic and non-irritating, and is an excellent raw material for modern skin care and hair care cosmetics. Pyroglutamic acid also inhibits the activity of tyrosine oxidase, thereby preventing "melanin-like" substances from depositing in the skin and having a whitening effect on the skin. It has a softening effect on keratin and can be used in nail cosmetics. In addition to its application in cosmetics, L-pyroglutamic acid can also generate derivatives with some other organic compounds, which have special effects in terms of surface activity, transparent and brightening effects, etc. It can also be used as a surfactant for detergents; a chemical reagent for the resolution of racemic amines; and an organic intermediate.

Preparation method: 

    L-pyroglutamic acid is formed by removing a molecule of water from the L-glutamic acid molecule. Its preparation process is simple, and the key steps are the control of temperature and dehydration time. 

    (1) Add 100 g of L-glutamic acid to a 500 ml beaker, heat the beaker in an oil bath, and when the temperature rises to 145-150°C, keep it warm for 45 minutes to carry out the dehydration reaction. The dehydrated solution is brown. 

    (2) After the dehydration reaction is completed, pour the solution into boiling water with a volume of about 350 ml, and the solution is completely dissolved in the water. After cooling to 40-50°C, add an appropriate amount of activated carbon for decolorization (repeat twice). A colorless and transparent solution is obtained. 

    (3) The colorless and transparent solution obtained in step (2) is directly heated and evaporated to concentrate until the volume is reduced to about half, and then transferred to a water bath to continue concentrating until the volume is about 1/3, then the heating can be stopped, and it is slowly cooled in a hot water bath to crystallize. After 10-20 hours, colorless prismatic crystals can be obtained. The amount of L-pyroglutamic acid used in cosmetics depends on the formula. This product can also be used in cosmetics in the form of 50% concentrated solution.

Uses: 

    Used as organic synthesis intermediate, food additive, etc.

    Used in food, medicine, cosmetics and other industries.

Production method: 

    There are semi-synthesis, enzyme conversion and total synthesis. The main method of industrial production is the semi-synthesis method using glutamic acid as raw material. Heat 42% glutamic acid aqueous solution at 1Chemicalbook40℃ for 3h to obtain a reaction solution with L-pyroglutamic acid as the main component. After reduced pressure concentration, crystallization, washing and drying, L-pyroglutamic acid is obtained, and the conversion rate is 94%.