A simple monoselective C-H oxygenation approach for the synthesis of ursane triterpenoids.

Herein, we presented a simple approach for C-H oxidation in the C23 or/and C24 of ursane triterpenoids without any protection of a Δ double bond. As a result, from commercial ursolic acid (UA), six naturally occurring ursane triterpenoids were synthesized in overall yields of 3.4% to 36.8%, which implied the importance of this approach for the derivation of natural products and their application in biological activity.