The Willgerodt-Kindler reaction on lupenone: unusual oxidative dimerization.

In continuation of our interest in chemical modification of triterpenoids, the Willgerodt-Kindler reaction of a lupane type triterpenoid lupenone provided a novel dimerized product 2. Formation of 2 is associated with an unusual oxidative dimerization of lupenone under Willgerodt-Kindler reaction conditions. The structure 2 was confirmed by extensive analysis of spectroscopic data including ES-MS and 2D-NMR.