Truxillic acids are any of several crystalline stereoisomeric cyclic dicarboxylic acids with the formula (C6H5C2H2(CO2H)2. They are colorless solids. These compounds are obtained by the [2 + 2] photocycloadditions of cinnamic acid where the two trans alkenes react head-to-tail. The isolated stereoisomers are called truxillic acids. The preparation of truxillic acids provided an early example of organic photochemistry.
Occurrence and reactions These compounds are found in a variety of plants, for example in coca. Incarvillateine, an alkaloid from the plant Incarvillea sinensis, is a derivative of α-truxillic acid.
Upon heating, truxillic acids undergo cracking to give cinnamic acid.
Isomers Truxillic acid can exist in five stereoisomers.
Truxillic acid isomersIsomerabcdefα-truxillic acid(cocaic acid)COOHHHC6H5HCOOHγ-truxillic acidCOOHHHC6H5COOHHε-truxillic acidHCOOHC6H5HHCOOH peri-truxillic acidCOOHHC6H5HCOOHH epi-truxillic acidCOOHHC6H5HHCOOH
Below are the five stereoisomers of truxillic acid, called alpha, gamma, epsilon, peri, and epi. These are shown both in a 2D skeletal diagram with stereocenters indicated and a 3D rendering of the structural geometry of the isomers themselves.
See also Truxinic acids are isomers of the truxillic acids with phenyl groups on adjacent methyne centers.
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