A novel diterpene lactone

A highly rearranged novel dilactone, ent-5α,15α-epoxy-9,10-friedo-10β,11β-di­hydroxy-16,11α:19,10β-diseco-17-nork­aur­an-16,19-dioic acid 16\rightarrow11:19\rightarrow10-dilactone, C19H24O5, was synthesized from ent-kaur-9(11)-en,16-nor,19-oic acid, which was obtained by oxidation of grandiflorenic acid, under Baeyer–Villiger rearrangement conditions. The structure of the final product was determined unambiguously by X-ray analysis.