Truly, in our hands commercially available (-)-caryophyllene oxide (11), was converted in good yield and on multigram scale to humulene oxide (10), providing ease access to a valuable intermediate, that is very tricky to be reached otherwise (Scheme 2). Next, we explored the allylic oxidation of 10, using standard protocol employing SeO2/t-BuOOH as the catalytic system. Even though TLC monitoring of the reaction indicated an unexpectedly clean conversion, NMR analysis of the reaction mixture revealed the presence of an inseparable mixture of three isomeric allylic alcohols 12a,b and ent-4. Indeed, Shirahama had previously reported that analogous oxidation on the same substrate leads to mixtures of geometrical isomers of allylic alcohols, one of them appearing in the form of two distinct and stable conformers. Unfortunately, the produced mixture of alcohols was extremely difficult to separate, especially given the unstable nature of them under standard purification conditions. Even worse, the desired (Z)-allylic alcohol ent-4, was by far the minor component of the mixture, indicating that typical SeO2 oxidation was not a productive solution to our problem.