Unified Total Syntheses of Anticancer Agent Nepetaefolin F and Indolosesquiterpenoids, Oridamycins A and B

The asymmetric total syntheses of triptobenzene L (<b>1a</b>), 4-<i>epi</i>-triptobenzene L (<b>1c</b>), nepetaefolin F (<b>1b</b>), and oridamycins A (<b>2c</b>) and B methyl ester (<b>2a</b>) have been accomplished through an enantioselective divergent approach from a highly functionalized common intermediate. A Lewis-acid-mediated highly regio- and diastereoselective epoxy-ene cyclization of (-)-<b>6</b> [92% ee] afforded the highly functionalized carbotricyclic core (+)-<b>5</b> [82%, dr >20:1] sharing four contiguous stereogenic centers [out of which two are all-carbon quaternary stereogenic centers]. Efficient functionalization of the advanced intermediate enabled the successful asymmetric total syntheses of naturally occurring <i>anti</i>-cancer abietane diterpenoid, such as <b>1b</b> and indolosesquiterpenoids <b>2a</b> and <b>2c</b>.