An attempt to enlarge the B ring of maoecrystal B, an ent-kaurane-type diterpene

An attempt to enlarge the B ring of maoecrystal B (6), an ent-kaurane-type diterpene from Isodon eriocalyx (Labiatae), to obtain the desired compound 23 via six steps, led to the novel rearranged diterpene compound 22.