Unambiguous Characterization of the Sesquiterpene (7R,9E)-1,2,11-Trihydroxy-1,3,5,9-bisabolatetraene through Its Enantioselective Synthesis

The bisabolane sesquiterpene (7R,9E)-1,2,11-trihydroxy-1,3,5,9-bisabolatetraene previously extracted from Commiphora kua resins was prepared by enantioselective synthesis using an enzyme-mediated resolution procedure as the key step. Both the chemical structure and the absolute configuration were unambiguously assigned, although the comparison of the obtained analytical data with those previously reported for the isolated terpene indicated a possible error in the characterization of the natural product. A further study on the chemical stability of the aforementioned compound revealed that it is very unstable in an acidic environment, where it cyclizes readily to give the corresponding chromane derivatives.