Collect. Czech. Chem. Commun. 1986, 51, 611-620

Conformation of ring A in 3-oxotriterpenoids. Dipole moments and CD spectra

Jiří Klinot, Václav Všetečka, Eva Klinotová and Alois Vystrčil

Department of Organic Chemistry, Charles University, 128 40, Prague 2


The A ring of 3-oxotriterpenoids allobetulone (I) and 3-xo-lupane-28-nitrile (IV) exists by about 40% in the boat form as derived from comparison of their dipole moments with those of 2α-methyl derivatives II, V (chair models) and 2β-methyl compounds III, VI (boat models). The same result was obtained from the CD spectra of 3-oxotriterpenoids I-VIII and from isomerization of the 2α- and 2β-substituted ketones XI and XII, respectively.