Collect. Czech. Chem. Commun. 1996, 61, 1360-1370

Oleanane Triterpenoids Functionalized at C-25 and C-26

Jan Sejbala, Jiří Klinota and Miloš Buděšínskýb

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


Reaction of 25-oximino-19β,28-epoxy-18α-oleanan-2β-ol (4) with nitrous acid afforded hemiacetal 22 ((25S)-2β,25;19β,28-diepoxy-18α-oleanan-25-ol). Functionalization of 19β,28-epoxy-18α-oleanan-2β-ol (1) with lead(IV) acetate gave 2β,25;19β,28-diepoxy-18α-oleanane (31). A series of derivatives with an oxygen functionality at position 25 has been prepared by modification of the functional groups in compounds 22 and 31. 26-Oximino-19β,28-epoxy-18α-oleanan-2β-ol (7) on reaction with nitrous acid afforded the corresponding nitrimine 10 which could not be converted into derivatives with an oxygen group at C-26: all the attempted preparations led invariably to compounds containing a nitrile group in position 8β. The nitrile groups in positions 10β and 8β appeared to be extremely unreactive.

Keywords: Triterpenoids; Oleanane; Functionalization; Oximes.