Asymmetric Dihydroxylation of a Meso-Symmetric Cyclic Diene Using AD-Mix Reagents: A New Enantiocontrolled Route to Conduritol E

The asymmetric dihydroxylation of two symmetric cyclohexa-1,3-diene derivatives, including a meso-symmetric substrate, has been investigated for the first time using the Sharpless AD-mix reagents. Although cyclohexa-1,3-diene itself showed unsatisfactory enantioselectivity, meso-symmetric 1,2-O-benzylidene-cis-cyclohexa-3,5-diene-1,2-diol showed a practical level of enantioselectivity and furnished the optically active diol in good yield. The diol obtained could be transformed into optically pure (+)-conduritol E in good yield, after a single recrystallization. The stereochemical outcome of the dihydroxylation was in harmony with the observations so far reported.