Truxillic acid

Truxillic acid
Names
	IUPAC name 2,4-Diphenyl-1,3-cyclobutanedicarboxylic acid
Identifiers
CAS Number	4462-95-7;
3D model (JSmol)	Interactive image;
ECHA InfoCard	100.022.478
CompTox Dashboard (EPA)	DTXSID20196252 ;
	SMILES OC(C1C(C2=CC=CC=C2)C(C(O)=O)C1C3=CC=CC=C3)=O;
Properties
Chemical formula	C18H16O4
Molar mass	296.322 g·mol−1
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Truxillic acids are any of several crystalline stereoisomeric cyclic dicarboxylic acids (C₆H₅)₂C₄H₄(COOH)₂ that yield cinnamic acid on distillation.^[1] The two trans alkenes react head-to-tail, and the isolated isomers are called truxillic acids. This products are made by a photochemical cycloaddition:

These compounds can be obtained in a variety of plants.^[2]^[3]

Truxillic acid isomers

The symmetry of these compounds makes only possible to have 5 possible stereoisomers in nature:^[4]^[5]

**Truxillic acid isomers**
Isomer	a	b	c	d	e	f
α-truxillic acid	COOH	H	H	C₆H₅	H	COOH
γ-truxillic acid	COOH	H	H	C₆H₅	COOH	H
ε-truxillic acid	H	COOH	C₆H₅	H	H	COOH
peri-truxillic acid	COOH	H	C₆H₅	H	COOH	H
epi-truxillic acid	COOH	H	C₆H₅	H	H	COOH

In the next picture is shown the complete structure of these truxillic acids:

^ Hein, Sara M. (2006). "An Exploration of a Photochemical Pericyclic Reaction Using NMR Data". Journal of Chemical Education. 83: 940–942. doi:10.1021/ed083p940.
^ Liebermann (1888). "Cinnamic acid polymers obtained from the minor alkaloids of cocaine". Berichte der Deutschen Chemischen Gesellschaft. 21: 3372–3376. doi:10.1002/cber.188802102223.
^ Krauze-Baranowska, Miroslawa (2002). "Truxillic and truxinic acids-occurrence in plant kingdom". Acta poliniae Pharmaceutica-Drug research. 59 (5): 403–410.
^ Stoermer (1924). "Five stereoisomers have been obtained: alfa-, gamma-, epsilon-, peri- and epi-isomers. Stereochemical configurations". Berichte der Deutschen Chemischen Gesellschaft, B: Abhandlungen. 57B: 15–23.
^ Agarwai, O. P. (2011). Organic Chemistry Reactions and Reagents. Krishna Prakashan Media. ISBN 8187224657.