A Classic Photochemical Approach Inducing an Unexpected Rearrangement: Exploring the Photoreactivity of Pentacyclic Triterpenic Acids.

The discovery of new bioactivities is closely related to the generation of novel scaffolds, and in the past few years different strategies have been proposed to obtain unknown architectures from the manipulation of known compounds. In the present study, we exploited a vintage photochemical approach for the discovery of an unexpected pathway of reactivity related to Δ-3-oxo-pentacyclic triterpenic acids gaining access to a new class of natural-unnatural 5(10→1)-pentacyclic triterpenic acids.