Wikipedia
Truxillic acid
Truxillic acids are any of several crystalline stereoisomeric cyclic dicarboxylic acids (CH)CH(COOH) that yield cinnamic acid on distillation. 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.