cinnamic acid

Cinnamic acid is a central intermediate in the biosynthesis of a myriad of natural products including lignols (precursors to lignin and lignocellulose), flavonoids, isoflavonoids, coumarins, aurones, stilbenes, catechin, and phenylpropanoids. Its biosynthesis involves the action of the enzyme phenylalanine ammonia-lyase (PAL) on phenylalanine.{{cite journal|journal=Molecular Plant|year=2010|volume=3|issue=1|pages=2–20|doi=10.1093/mp/ssp106|title=Phenylpropanoid Biosynthesis|last=Vogt|first=T.|pmid=20035037|doi-access=free}}

It is obtained from oil of cinnamon, or from balsams such as storax.{{Merck12th}} It is also found in shea butter.{{cn|date=June 2023}} Cinnamic acid has a honey-like odor;{{cite web|url=http://www.flavornet.org/info/140-10-3.html|title=Cinnamic acid|website=flavornet.org}} and its more volatile ethyl ester, ethyl cinnamate, is a flavor component in the essential oil of cinnamon, in which related cinnamaldehyde is the major constituent. It is also found in wood from many diverse tree species.{{cite web |last1=Oldach |first1=Laurel |title=Forensic researchers use mass spectrometry to identify smuggled wood |url=https://cen.acs.org/analytical-chemistry/mass-spectrometry/Forensic-researchers-use-mass-spectrometry-to-identify-smuggled-wood/101/i7 |website=Chemical and Engineering News |publisher=American Chemical Society |date=February 22, 2023}}

Cinnamic acid was first synthesized by the base-catalysed condensation of acetyl chloride and benzaldehyde, followed by hydrolysis of the acid chloride product.{{Ullmann|first=Dorothea|last=Garbe|title=Cinnamic Acid|doi=10.1002/14356007.a07_099|year=2012}} In 1890, Rainer Ludwig Claisen described the synthesis of ethyl cinnamate via the reaction of ethyl acetate with benzaldehyde in the presence of sodium as base.{{cite journal|last=Claisen|first=L.|date=1890|url=https://babel.hathitrust.org/cgi/pt?id=uc1.b3481786;view=1up;seq=992|title=Zur Darstellung der Zimmtsäure und ihrer Homologen|trans-title=On the preparation of cinnamic acid and its homologues|journal=Berichte der Deutschen Chemischen Gesellschaft|volume=23|pages=976–978|doi=10.1002/cber.189002301156}} Another way of preparing cinnamic acid is by the Knoevenagel condensation reaction.{{cite book|first=L.|last=Tieze|title=Reactions and Synthesis in the Organic Chemistry Laboratory|location=Mill Vall, CA|date=1988|page=1988}} The reactants for this are benzaldehyde and malonic acid in the presence of a weak base, followed by acid-catalyzed decarboxylation. It can also be prepared by oxidation of cinnamaldehyde, condensation of benzal chloride and sodium acetate (followed by acid hydrolysis), and the Perkin reaction. The oldest commercially used route to cinnamic acid involves the Perkin reaction, which is given in the following scheme

:File:Zimtsäure nach Perkin.svg.{{cite journal |doi=10.15227/orgsyn.005.0083|author=F. K. Thayer|title=m-Nitrocinnamic Acid|journal=Organic Syntheses|year=1925|volume=5|page=83}}]]

Cinnamic acid, obtained from autoxidation of cinnamaldehyde, is metabolized into sodium benzoate in the liver.{{cite journal | vauthors = Jana A, Modi KK, Roy A, Anderson JA, van Breemen RB, Pahan K | title = Up-regulation of neurotrophic factors by cinnamon and its metabolite sodium benzoate: therapeutic implications for neurodegenerative disorders | journal = Journal of Neuroimmune Pharmacology | volume = 8 | issue = 3 | pages = 739–55 | date = June 2013 | pmid = 23475543 | pmc = 3663914 | doi = 10.1007/s11481-013-9447-7 | url = | issn = }}

Cinnamic acid is used in flavorings, synthetic indigo, and certain pharmaceuticals. A major use is as a precursor to produce methyl cinnamate, ethyl cinnamate, and benzyl cinnamate for the perfume industry. Cinnamic acid is a precursor to the sweetener aspartame via enzyme-catalysed amination with phenylalanine. Cinnamic acid can dimerize in non-polar solvents resulting in different linear free energy relationships.{{cite journal | doi = 10.1186/s13065-015-0080-9 | pmid = 25798191 | pmc = 4369286 | title = Determination of Abraham model solute descriptors for the monomeric and dimeric forms of trans-cinnamic acid using measured solubilities from the Open Notebook Science Challenge | journal = Chemistry Central Journal | volume = 9 | pages = 11 | year = 2015 | last1 = Bradley | first1 = J.-C. | last2 = Abraham | first2 = M. H. | last3 = Acree | first3 = W. E. | last4 = Lang | first4 = A. | last5 = Beck | first5 = S. N. | last6 = Bulger | first6 = D. A. | last7 = Clark | first7 = E. A. | last8 = Condron | first8 = L. N. | last9 = Costa | first9 = S. T. | last10 = Curtin | first10 = E. M. | last11 = Kurtu | first11 = S. B. | last12 = Mangir | first12 = M. I. | last13 = McBride | first13 = M. J. | doi-access = free }}

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{{Hydroxycinnamic acid}}

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Category:Flavors

Category:Enoic acids

Category:Phenylpropanoids