The synthesis of β-amyrin

Abstract

18α-Olean-12-ene, which is in acid-catalysed equilibrium with olean-13(18)-ene (δ-amyrene), has been converted in several steps into olean-12-ene (β-amyrene). Transformation of this hydrocarbon into its 11α-hydroxyderivative and photolysis of the nitrite of the latter gave 11α-hydroxy-1-oximino-olean-12-ene. This oxime has been hydrolysed and further processed to furnish olean-12-en-1-one. Several methods have been developed to change the 1-oxo into a 3-oxo-function and vice versa. Since olean-12-en-3-one has already been reduced to β-amyrin and olean-13(18)-ene has been synthesised, our work constitutes a synthesis of β-amyrin.

Related studies on the photolysis of 11β-hydroxyolean-12-ene nitrite and on the interrelationship of the 1- and 3-oxo-groups in the lanostane series are also recorded.