Derivatization of ursolic acid, one of the natural ursene-type pentacyclic triterpenes, was investigated by the oxidation with dioxoruthenium(VI) tetraphenylporphyrins. Oxidation selectivity on the terpenestructure was modulated by the auxiliaries introduced on the tetraphenylporphyrin. Chemical oxidation of the ursolic acid affected the cytotoxic activity against tumor cell lines.