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Decarboxylation
From Wikipedia, the free encyclopedia
Decarboxylation is any chemical reaction in which a carboxyl group (-COOH) is split off from a compound as carbon dioxide (CO2).
Common biosynthetic decarboxylations of amino acids to amines are: tryptophan to tryptamine, phenylalanine to phenylethylamine, tyrosine to tyramine, histidine to histamine, serine to ethanolamine, glutamic acid to GABA, lysine to cadaverine, arginine to agmatine, ornithine to putrescine, 5-HTP to serotonin, and L-DOPA to dopamine. Other decarboxylation reactions from the citric acid cycle include: pyruvate to acetyl-CoA, oxalosuccinate to α-ketoglutarate, and α-ketoglutarate to succinyl-CoA. Enzymes that catalyze decarboxylations are called decarboxylases or, more formally, carboxy-lyases (E.C.4.1.1).
Chemical decarboxylations reactions often require extensive heating in high-boiling solvents. Copper salts are often added as catalysts. Also the addition of catalytic amounts of cyclohexen-2-one has been reported to catalyze the decarboxylation of amino acids. Decarboxylations are especially easy for beta-keto acids due to the formation of a cyclic transition state for instance in Knoevenagel condensations. The Barton decarboxylation is a radical reaction.