Prephenic acid

Prephenic acid, commonly also known by its anionic form prephenate, is an intermediate in the biosynthesis of the aromatic amino acids phenylalanine and tyrosine, as well as of a large number of secondary metabolites of the shikimate pathway.

Prephenic acid

Names
Preferred IUPAC name (1s,4s)-1-(2-Carboxy-2-oxoethyl)-4-hydroxycyclohexa-2,5-diene-1-carboxylic acid
Other names Prephenate; cis-1-Carboxy-4-hydroxy-α-oxo-2,5-cyclohexadiene-1-propanoic acid
Identifiers
CAS Number	126-49-8 (unspecified) Y 87664-40-2 (cis) Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:84387 N
ChemSpider	16735981 Y
MeSH	Prephenic+acid
PubChem CID	1028 (unspecified)
UNII	Z66B98Z97I (unspecified) Y
CompTox Dashboard (EPA)	DTXSID60894109
InChI InChI=1S/C10H10O6/c11-6-1-3-10(4-2-6,9(15)16)5-7(12)8(13)14/h1-4,6,11H,5H2,(H,13,14)(H,15,16)/t6-,10+ Y Key: FPWMCUPFBRFMLH-XGAOUMNUSA-N Y InChI=1/C10H10O6/c11-6-1-3-10(4-2-6,9(15)16)5-7(12)8(13)14/h1-4,6,11H,5H2,(H,13,14)(H,15,16)/t6-,10+ Key: FPWMCUPFBRFMLH-XGAOUMNUBN
SMILES O=C(O)[C@@]/1(CC(=O)C(O)=O)\C=C/[C@@H](O)\C=C\1
Properties
Chemical formula	C10H10O6
Molar mass	226.184 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Occurrence and biological significance

Prephenic acid occurs naturally as an intermediate in the biosynthesis of phenylalanine and tyrosine via the shikimic acid pathway.^[1][2] It is formed from chorismic acid by chorismate mutase. It can be dehydrated by prephenate dehydratase to phenylpyruvic acid, which is a precursor of phenylalanine. Alternatively, it can be dehydrated by prephenate dehydrogenase to 4-hydroxyphenylpyruvic acid, which is a precursor of tyrosine.^[1]

It is biosynthesized by a [3,3]-sigmatropic Claisen rearrangement of chorismate.^[3][4]

Synthesis

Prephenic acid is unstable; as a 1,4-cyclohexadiene, it is easily aromatized, for example, under the influence of acids or bases. This instability makes both isolation and synthesis difficult. Prephenic acid was first isolated from mutants of Escherichia coli that were unable to convert prephenic acid to phenylpyruvic acid. During this process, the barium salt was obtained.^[2]

Stereochemistry

Prephenic acid is an example of achiral (optically inactive) molecule which has two pseudoasymmetric atoms (i.e. stereogenic but not chirotopic centers), the C1 and the C4 cyclohexadiene ring atoms. It has been shown^[5] that of the two possible diastereoisomers, the natural prephenic acid is one that has both substituents at higher priority (according to CIP rules) on the two pseudoasymmetric carbons, i.e. the carboxyl and the hydroxyl groups, in the cis configuration, or (1s,4s) according to the new IUPAC stereochemistry rules (2013).^[6]

The other stereoisomer, i.e. trans or, better, (1r,4r), is called epiprephenic.

See also

• C₁₀H₁₀O₆