Collect. Czech. Chem. Commun. 1979, 44, 211-225

Preparation of 2-methyl-3-oxo triterpenoids of 18α-oleanane series and the conformation of ring A

Jiří Klinota, Jarmil Světlýa, Dagmar Kudláčkováa, Miloš Buděšínskýb and Alois Vystrčila

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


2-Methyl-3-hydroxy derivatives X, XIII, XV, XVI and 2-methyl-3-oxo derivatives III, VIII and IX of 19β,28-epoxy-18α-oleanane were prepared from ketones I and XVII. From spectral data it was deduced that compounds III, VIII and XV containing a 2β-methyl group have their A ring in boat conformation. Both isomeric 2-methyl-3-oxo derivatives VIII and IX are approximately equally stable; 52 ± 4% of the 2β-isomer VII were found in their equilibrium mixture.