Synthesis of Novel 8,14-Secoursane Derivatives: Key Intermediates for the Preparation of Chiral Decalin Synthons from Ursolic Acid

The novel 8,14‐secoursatriene derivative 6 was synthesized starting from ursolic acid (1) via methyl esterification of the 17‐carboxylic acid group and benzoylation of the 3‐hydroxy group (→2; Scheme 1), ozone oxidation of the C(12)C(13) bond (→3), dehydrogenation with Br2/HBr (→4), enol acetylation of the resulting carbonyl group (→5; Scheme 2), and ring‐C opening with the aid of UV light (→6). Ring‐C‐opened dienone derivative 7 of ursolic acid was also obtained via selective hydrolysis of 6 (Scheme 2). Both compounds 6 and 7 are key intermediates for the preparation of chiral decalin synthons from ursolic acid.