To further improve our synthesis, we envisioned direct installation of hydroxyl group, while triggering the retro-cycloisomerization rearrangement. A recent work by Lei describes the visible light mediated anti-Markovnikov hydration of olefins, that is claimed to proceed via a radical intermediate, thus deemed to be ideal for our purposes (Scheme 3; I: X = OH, * = radical). Regretfully, on our substrate, such a protocol proved ineffective, since it led to a rather complicated reaction mixture, the 1 H-NMR spectrum of which did not indicate any ring opening of the bicyclic of caryophyllene oxide. Having ensure a rapid access to the oxidized humulene-type substrate ent-4, we were in position to investigate the plausible biomimetic intramolecular epoxide opening. Apparently, acid catalysis was required to favor the anticipated regioselectivity, that forms a seven membered ring, in contrast to the six membered analogue that is expected to be preferred in a non-catalytic process. Thankfully, treatment of ent-4 with various types of acids (SnCl4, BF3•Et2O, TFA, Sc(OTf)3), all brought about