Picolinic acid explained

Picolinic acid is an organic compound with the formula . It is a derivative of pyridine with a carboxylic acid (COOH) substituent at the 2-position. It is an isomer of nicotinic acid and isonicotinic acid, which have the carboxyl side chain at the 3- and 4-positions, respectively. It is a white solid although impure samples can appear tan. The compoundthat is soluble in water.

Production

On a commercial scale, picolinic acid is produced by ammoxidation of 2-picoline followed by hydrolysis of the resulting nitrile:

It is also produced by oxidation of picoline with nitric acid.

In the laboratory, picolinic acid is formed from 2-methylpyridine by oxidation with potassium permanganate (KMnO₄).^{[1] [2]}

Reactions

Hydrogenation of picolinic acid gives piperidine-2-carboxylic acid, a precursor to the drug Mepivacaine.

Picolinic acid is a bidentate chelating agent of elements such as chromium, zinc, manganese, copper, iron, and molybdenum in the human body.^{[3] [4]}

It is a substrate in the Mitsunobu reaction. In the Hammick reaction, picolinic acid reacts with ketones to give pyridine-2-carbonols:^[5]

Biosynthesis

Picolinic acid is a catabolite of the amino acid tryptophan through the kynurenine pathway.^[6] Its function is unclear, but it has been implicated in a variety of neuroprotective, immunological, and anti-proliferative effects. In addition, it is suggested to assist in the absorption of zinc(II) ions and other divalent or trivalent ions through the small intestine.^[7]

Picolinates

Salts of picolinic acid (picolinates) include:

• Chromium(III) picolinate
• Zinc picolinate

See also

• Dipicolinic acid

Notes and References

1. 10.15227/orgsyn.020.0079 . Picolinic Acid Hydrochloride . Organic Syntheses . 1940 . 20 . 79. Alvin W.. Singer. S. M. . McElvain .
2. Book: Harold Hart, Leslie E. Craine, David J. Hart, Christopher M. Hadad; Nicole Kindler. 'Organische Chemie 3. Auflage. Wiley-VCH. Weinheim. 2007. 978-3-527-31801-8. 494.
3. 10.3891/acta.chem.scand.23-3011 . The Crystal Structure of Zinc Picolinate Tetrahydrate, Zn(C₆H₄O₂N)₂(H₂O)₄ . 1969 . Lumme . Paavo . Lundgren . Georg . Mark . Wanda . Lundström . Hans . Borch . Gunner . Craig . J. Cymerman . Acta Chemica Scandinavica . 23 . 3011–3022 .
4. 10.1021/ar5004626 . Bidentate, Monoanionic Auxiliary-Directed Functionalization of Carbon–Hydrogen Bonds . 2015 . Daugulis . Olafs . Roane . James . Tran . Ly Dieu . Accounts of Chemical Research . 48 . 4 . 1053–1064 . 25756616 . 4406856 .
5. Book: Fuchs, Philip L. . Picolinic acid . https://books.google.com/books?id=Cbc2AAAAQBAJ&q=picolinic%20acid . Catalytic Oxidation Reagents . 2013-07-29 . 495ff . Wiley Inc. . 954583821 . 9781118704844.
6. Tan . L. . etal . December 2012 . The kynurenine pathway in neurodegenerative diseases: mechanistic and therapeutic considerations . J Neurol Sci . 323 . 1–2. 1–8 . 10.1016/j.jns.2012.08.005 . 22939820 . 6061945 .
7. Evans . Gary . 1982 . The Role of Picolinic Acid in Metal Metabolism . Life Chemistry Reports . Harwood Academic Publishers . 1 . 57–67 . 20 March 2015 . 26 January 2016 . https://web.archive.org/web/20160126125834/http://naldc.nal.usda.gov/download/46436/PDF . dead .