CHEMISTRY OF URSOLIC ACID
15 January 2009 (online)
Oxidation of ursolic acid acetate with chromium trioxide in acetic acid leads to 3β–acetoxy–11–oxoursolic acid (50 %) and a new ketolactone, 3β–acetoxy–12–oxo–ursan–28–oic–13(28)–lactone (20 %) if the reaction temperature is kept under 80° C. At 100° C, 3β–acetoxy–11,12–dioxoursan–28–oic–13(28)lactone (26 %) is formed instead of the 12–oxo–lactone.
LiAlH4 reduction of 3β–acetoxy–11–oxo–ursolic acid yields two new compounds, 3β–ol–ursa–11,12–ene–13,28–oxaand3β–ol–ursa–11,12–ene–13(28)–lactone.
The reduction mechanism is investigated and described.