Collect. Czech. Chem. Commun. 1999, 64, 329-347

Reaction of 18β,19β-Epoxylupan-21-one Derivatives with Acids: A Way to 21,22-Disubstituted Lup-18-ene Triterpenoids

Eva Klinotová*, Jitka Čermáková, Martin Rejzek, Václav Křeček, Jan Sejbal, Petr Olšovský and Jiří Klinot

Department of Organic Chemistry, Faculty of Science, Charles University, 128 40 Prague 2, Czech Republic


Depending on the conditions and the acid employed, 18β,19β-epoxy-28-hydroxy- 21-oxolupan-3β-yl acetate (2a) and 18β,19β-epoxy-21-oxolupane-3β,28-diyl diacetate (2b) on treatment with acid gave three types of products: (i) 28-nor derivatives: 21-oxo-28-norlupa-16,18-dien-3β-yl acetate (6), 19β-hydroxy-21-oxo-28-norlup-17-en-3β-yl acetate (7) and 17ξ-hydroxy-21-oxo-28-norlup-18-en-3β-yl acetate (8), (ii) lupa-12,18-dien-21-ones 4a and 4b, and (iii) 22β-substituted lup-18-en-21-one derivatives of the type 5. The formation of 22β-substituted derivatives of the type 5 probably proceeds in the enol form of epoxy ketone 2. Opening of the epoxide ring with shift of the double bond to position 19(21) and attack by nucleophilic species at C-22 followed by elimination of water and re-formation of the 22-oxo group leads to derivatives of the type 5.

Keywords: Triterpenes; Triterpenoids; Lupane; Epoxy ketones; NMR spectroscopy, 1H and 13C.