Collect. Czech. Chem. Commun. 1993, 58, 1675-1691

Structure of Dimeric Compounds Obtained from 3β-Acetoxy-21,22-dioxo-18α,19βH-ursan-28,20β-olide

Eva Klinotováa, Jiří Klinota, Václav Křečeka, Stanislav Hilgarda, Miloš Buděšínskýb and Jan Malátb

a Department of Organic Chemistry, Charles University, 128 40 Prague 2, Czech Republic
b Institute and Biochemistry, Academy of Sciences of the Czech Republic, 166 10 Prague 6, Czech Republic


The triterpenoid α-diketone with oxabicyclo[2.2.2]octane system in the ring E (3β-acetoxy-21,22-dioxo-18α,19βH-ursan-28,20β-olide (I)) gives isopropylidenedioxy derivative II and dimeric compounds V and IX when submitted to chromatography on silica gel in the presence of acetone. Compounds V and IX were reduced with hydride to hydroxy derivatives VI, X, and XI; on reaction with diazomethane they gave dimeric compounds with spiroepoxide group at the position 21 (compound VII) or 22 (compound XII) which reacted further with diazomethane to give monomeric spiroepoxides VIII, XIII, and XIV. The structure of the compounds obtained was derived from their 1H and 13C NMR, IR, and FAB mass spectra.