2-Cyano-3,12-dioxoolean-1,9-dien-28-oic acid (CDDO), with CAS number 218600-44-3, is a synthetic triterpenoid derivative based on the natural product oleanolic acid. It is a potent and well-characterized small molecule activator of the Nrf2 (Nuclear factor erythroid 2-related factor 2) signaling pathway. This compound is a key intermediate and the core pharmacophore for the development of more advanced analogs, such as CDDO-methyl ester (CDDO-Me, bardoxolone methyl) and CDDO-imidazolide (CDDO-Im). The primary and most significant application of CDDO and its derivatives is in the field of oncology and inflammation-related diseases. By activating the Nrf2 pathway, it induces the expression of a battery of cytoprotective genes, leading to antioxidant, anti-inflammatory, and anti-proliferative effects. This mechanism underpins its investigation as a therapeutic agent for various cancers, chronic kidney disease, and other conditions driven by oxidative stress and inflammation. Bardoxolone methyl has been advanced into clinical trials for these indications. As a semi-synthetic derivative of a natural pentacyclic triterpenoid, CDDO represents a significant molecule in medicinal chemistry for structure-activity relationship (SAR) studies. Its complex, multi-functionalized structure makes it a specialized synthetic target rather than a general-purpose building block. Research focuses on its biological activity and the development of its prodrug forms for improved pharmacokinetics.