Pyroglutamic acid

• L -pyroglutamic acid
• (S)- pyroglutamic acid
• D -pyroglutamic acid
• (R) -pyroglutamic acid

• 98-79-3 (L -pyroglutamic acid )
• 4042-36-8 (D -pyroglutamic acid )
• 149-87-1 (DL- pyroglutamic )

Fixed

162-163 ° C ( L- enantiomer)

Soluble in water, ethanol and acetone

Attention

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Pyroglutamic acid is a derivative of glutamic acid and not one of the ( proteinogenic ) amino acids. Pyroglutamic acid has a stereogenic center at the 2- position on the pyrrolidine ring, that is chiral. Thus, there exist two enantiomers: L- pyroglutamic acid [ Synonym: (S)- pyroglutamic acid ] and D -pyroglutamic acid [ Synonym: (R) -pyroglutamic acid ].

When it is mentioned in this article or in the scientific literature " pyroglutamic acid " without further suffix ( prefix) -pyroglutamic acid ISTL meant.

Occurrence

L -pyroglutamic acid is a cyclized inner amide of L -glutamic acid and is found in vegetables, fruits, grasses, and in molasses. Peptides with N-terminal L -glutamine, the amino group is unprotected, are easily converted into pyroglutamyl - peptides.

Production and representation

By heating a mixture of equal parts by weight of glutamic acid, and water in an autoclave, is obtained at reaction temperatures of 135-140 ° C and the pyroglutamic acid.

Chemical Properties

The carboxyl group of the L- pyroglutamic acid may be with alcohols in acidic medium to L- esters of pyroglutamic acid (also called together with the Pyroglutamate salt of pyroglutamic acid ) are esterified, the lactam function remains unchanged. By treatment with phosphorus pentasulfide, the lactam function of the L- pyroglutamic is converted into a Thiolactamfunktion.

D- and L -pyroglutamic acid also do not count as amino acids, because in addition to the acidic carboxy no basic amino group present in the molecule, since the nitrogen in the five-membered ring part of a lactam ( cyclic amide ) is. Are both D- and L- pyroglutamic acid also derivatives of an amino acid of the D-or L -glutamic acid.

Use

The pure enantiomers of pyroglutamic acid, ie, L -pyroglutamic acid and D -pyroglutamic acid, are often used for the resolution of racemic amines. From L -pyroglutamic acid also L-proline can be synthesized. The chiral auxiliary RAMP was synthesized from D -pyroglutamic acid. The use of both enantiomers of pyroglutamic acid in other stereoselective synthesis has been described in a review article. The natural product domoic acid was synthesized in a multistep synthesis of (S) -pyroglutamic acid.