Triterpenoids. Part VII. Photoisomerisation of 11-oxo-12-enes
Abstract
Irradiation of a dioxan solution of α- or β-amyrenonyl acetate affords 11,25-cyclo-11α-hydroxy-α- or -β-amyrin acetate, respectively. Oxidation of the 11,25-cyclo-11α-ols with lead tetra-acetate yields 25-hydroxy-α- or-β-amyrenonyl acetate, while acid-catalysed cleavage of the photoproducts gives the corresponding 11-methyl-25-nor-5(10),11,13(18)-triene.