Collect. Czech. Chem. Commun. 1987, 52, 1052-1061

Reaction of 3-keto and 2-ketotriterpenoids with 3-chloroperoxybenzoic acid in aliphatic alcohols. A new method of preparation of α-hydroxy ketones

Jan Sejbal, Jiří Klinot and Alois Vystrčil

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


19β,28-Epoxy-18α-oleanan-3-one (I), 19β,28-epoxy-24-nor-18α-oleanan-3-one (XIV) and 3-lupanone (XVII) are hydroxylated with 3-chloroperoxybenzoic acid in the presence of methanol or ethanol and 0.01-0.1% of sulfuric acid in position 2α. Hydroxy ketones VII, XV, and XVI are formed, respectively. The reaction is sensitive to the concentration of sulfuric acid; beyond this concentration range predominantly various 3,4-seco derivatives are formed (for example VI, IX, X, XVIII). 2-Oxo derivative IV is hydroxylated in a similar manner, giving rise to 3α-hydroxy-2-ketone VIII, while 1-oxo derivative XIII does not react. A reaction path is proposed for the hydroxylation, comprising the enol form or the enol ether as an intermediate.