5,6-Dihydropyran derivatives of nor-lupane: synthesis and properties

Using triterpenoid betulin as an example, a convenient method for the synthesis of 5,6-dihydropyran derivatives containing a nor-triterpenoid fragment at position 4 was proposed. The method involves the reaction of lupane triterpenoids with paraformaldehyde in dioxane in the presence of sulfuric acid. Approaches to the synthesis of triterpene derivatives of 5,6-dihydropyran-2-one and penta-2,4-dienoic acid were developed based on the obtained 4-(3,28-diacetoxy-20,29,30-tri-nor-lupan-19-yl)-5,6-dihydropyran. Triterpene-substituted penta-2,4-dienoic acid heated with triphenylphosphonium triflate formed a quaternary phosphonium salt, which showed cytotoxicity against human cancer cells MCF-7 (breast cancer) and HCT116 (colon cancer) with IC₅₀ 4–19 µmol L⁻¹, with its activity against these cell lines being superior to the activity of the comparison drug camptothecin.