The Chemical Entities of Biological Interest (ChEBI) ontology is downloaded weekly from EMBL-EBI at http://www.ebi.ac.uk/chebi/. The data is made available under the Creative Commons License (CC BY 3.0, http://creativecommons.org/licenses/by/3.0/). For more information see: Degtyarenko et al. (2008) ChEBI: a database and ontology for chemical entities of biological interest. Nucleic Acids Res. 36, D344–D350.
An alpha,beta-unsaturated carboxylic ester of general formula R(1)R(2)C=CR(3)-C(=O)OR(4) (R(4) =/= H) in which the ester C=O function is conjugated to a C=C double bond at the alpha,beta position.