Cinnamic acid is an organic compound with the formula C6H5CHCHCO2H. It is a white crystalline compound that is slightly soluble in water. Classified as an unsaturated carboxylic acid, it occurs naturally in a number of plants. It is freely soluble in many organic solvents. It exists as both a cis and a trans isomer, although the latter is more common. The original synthesis of cinnamic acid involves the Perkin reaction, which entails the base-catalysed condensation of acetic anhydride and benzaldehyde. Cinnamic acid is used in flavors, synthetic indigo, and certain pharmaceuticals. A major use is in the manufacturing of the methyl, ethyl, and benzyl esters for the perfume industry. Cinnamic acid is a precursor to the sweetener aspartame via enzyme-catalysed amination to phenylalanine. Cinnamic acid is also a kind of self-inhibitor produced by fungal spore to prevent germination.