Toward the Total Synthesis of Vinigrol: Synthesis of epi-C-8-Dihydrovinigrol

Two approaches to vinigrol starting from the advanced tricyclic core <b>7</b> have been explored using as key intermediates epoxide <b>12</b> and diol <b>17</b>. The preparation of the properly functionalized epoxide <b>12</b> has been achieved in a straightforward fashion. However, all attempts to prepare tertiary alcohol <b>14</b> by reductive opening of <b>12</b> failed. In alternative exploratory efforts to achieve the same goal, allylic alcohols <b>16</b> and <b>29</b> were prepared by regioselective dehydration of diol <b>17</b>. Whereas <i>endo</i>-isomer <b>16</b> was found to be reluctant to undergo catalytic hydrogenation, the <i>exo</i> counterpart <b>29</b> led to the undesired isomer affording after hydrolysis epi-C-8-dihydrovinigrol <b>32</b>.