Figure 2.

Structures and synthesis of CDDO and CDDO-Me, two synthetic derivatives of oleanolic acid. (A) Synthesis pathway of CDDO, as described by Honda et al. [18]. Compound 2 was obtained from the already known compound 1 by alkali hydrolysis and Jones oxidation. Compound 3 was obtained by formylation of 2 with ethyl formate; compound 4 was obtained from 3 by addition of hydroxylamine, and compound 5 by cleavage of isoxazole 16 with sodium methoxide and subsequent double bond introduction at C1 with PhSeC1–H₂O₂. CDDO (compound 6) was obtained from 5 by halogenolysis of 5 with lithium iodide in dimethylformamide. (B) Structure of CDDO and CDDO-Me. CDDO-Me is the C28 methyl ester of CDDO.