Gratifyingly, our hypothesis proved correct. After much experimentation we found that treatment of (-)-caryophyllene oxide (11) with NBS in acetone afforded the expected humulene-type bromide 13, with vinyl bromides 14a,b accounting for the rest of the consumed starting material (Scheme 4). NBS proved unique electrophilic bromine source among a variety of similar activators tested. Different halogen electrophiles also turned out to be unproductive. Unlikely, the polarity of all three bromides was very similar rendering purification problematic. To circumvent this adverse event, we proceeded with the hydrolysis of the reaction mixture with the expectation that vinylic bromides 14a,b would be inert to the reaction conditions. Indeed, the anticipated (Z)-allylic alcohol ent-4 was the only alcohol detected in the reaction mixture, while bromides 14a,b were recovered intact after fast purification using neutralized silica gel. The combined yield range of alcohol ent-4 for the two-step sequence is 30-35%, consistently, regardless the scale of the reaction, typically applied on gram scale. Scheme 4. Two-step synthesis of (Z)-alcohol ent-4 from (-)caryophyllene oxide (11).