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• Characteristics and Application

  L-pyroglutamic acid is an amino acid that occurs naturally in the body. It is present in the brain, spinal fluid, skin and blood.
  pyroglutamic acid is one of the major components of natural moisturizing factor of the skin, its moisturizing ability is far stronger than glycerin and propylene glycol. Moreover, it is non-toxic, non-irritating, and is an excellent raw material for modern skin care, and hair care cosmetics. Pyroglutamic acid also has inhibitory effect on the tyrosine oxidase activity, and thus preventing "melanoidins" substance from being deposited in the skin, and having a whitening effect on the skin. It has a keratin softening effect which can be used in nail cosmetics.
  In addition to be applied in cosmetics, L-pyroglutamic acid derivatives can also have reaction with a number of other organic compounds for synthesis of derivatives. It also has some special effect on the surface activity and brilliant effect. Moreover, it can also be used as surfactants for detergents; as a chemical reagent, it can be used for the resolution of racemic amines; it can also be used as a kind of organic intermediates.;

• Pyroglutamic acid

  Pyroglutamic acid is a kind of based 5-oxo-proline. It is produced by the dehydration and formation of intramolecular amide bond between the α-NH2 group and γ-hydroxy of glutamic acid; the molecule can also be produced from glutamine by losing its intramolecular amine group. The condition of glutathione synthetase deficiency can cause the anemia of pyroglutamic acid with a series of clinical symptoms. Pyroglutamic acid anemia is a kind of organic acid metabolic disorder disease caused by glutathione synthetase hyperlipidemia. Clinical manifestations: disease onset occurs within 12 to 24 hours of born with progressive hemolysis, jaundice, chronic metabolic acidosis, mental retardation; urine containing pyroglutamic acid, lactic acid, α-deoxy-4-hydroxyphenyl acetyl acid lactone. For treatment, based on the actual symptoms, pay attention to adjust the diet after yearling.
  The above information is edited by the Chemicalbook of Dai Xiongfeng. ;

• Preparation

  L-pyroglutamic acid is formed by removing one intramolecular water molecule in the L-glutamic acid; the preparation process is simple with the key step being the control of the temperature and dehydration time.
  (1) Add100 g of L-glutamic acid into a 500-ml beaker; heat the beaker in an oil bath until the temperature was raised to 145~150 °C, incubate for 45 minutes to perform dehydration reaction. The dehydrated solution was brown.
  (2) After the end of dehydration reaction, pour the solution into a volume of about 350 ml of boiling water with a solution of all further being dissolved in water. Cool to 40~50 °C, add appropriate amount of activated carbon for decolorization (repeated twice) to obtain a colorless transparent solution.
  (3) directly heat and evaporate the colorless and transparent solution of the step (2) is a colorless and transparent solution for concentration to a half of the previous volume and then continue for concentration in a water bath to a volume of about 1/3 of the previous solution, and then stop heating; have it slightly cooled in the hot water bath for crystallization; the colorless prisms can be obtained after 10 to 20 hours.
  The applied amount of L-pyroglutamic acid in cosmetics should depend on the formula. This product can also be applied to cosmetic in the form of 50% concentrated solution. ;

• Chemical Properties

  It is colorless crystals with the melting point being 162-163 °C; it is soluble in water, alcohol, acetone and acetic acid, slightly soluble in ethyl acetate, but insoluble in ether. ;

• Uses

  L-Pyroglutamic acid is used in the synthesis of:
  Nonproteinogenic amino acids such as (3S,4R)-3,4-dimethyl-L-pyroglutamic acid and (3S,4R)-3,4-dimethyl-L-glutamine.
  Chiral N-heterocyclic carbenes (NHCs) as catalysts for the asymmetric dimerization of alkylarylketenes to give the corresponding α-quaternary β-alkylidenyl-β-lactones.
  It is also used in the total synthesis of (−)-stemoamide and celogentin C.
  It can be used as a kind of intermediates of organic synthesis as well as food additives.
  It is used in food, medicine, cosmetics and other industries.;

• Production method

  There are semi-synthetic methods, enzymatic conversion method and total synthesis method. Currently the major approach of industrial production is the semi-synthetic method with glutamic acid being the raw material. Have the 42% of glutamic acid solution heated at 140 °C for 3h to obtain the reaction solution with L-pyroglutamic acid being the major component. The reaction solution further undergoes concentration under reduced pressure, crystallization, washing, and drying to obtain the L-pyroglutamic acid with the conversion rate being 94%. ;

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