Collect. Czech. Chem. Commun. 1985, 50, 2918-2924

Preparation of isomeric 2-methyl-3-oxolupane-28-nitriles

Jiří Klinot, Jarmil Světlý, Eva Klinotová and Alois Vystrčil

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


2β-Methyl- and 2α-methyl-3-oxo derivatives of lupane-28-nitrile XV and XVI were prapared from betulin-3-acetate (I). The key steps of the synthesis were the condensation of ketone VII with formaldehyde and dimethylamine hydrochloride, conversion of the methylene ketone VIII formed to 3β-acetoxy-2-methylene derivative X and hydrogenation of the exomethylene double bond. Both 2-methyl-3-oxo derivatives, XV and XVI, are approximately equally stable; in their equilibrium mixture 47 ± 3% of the 2β-isomer were found.