Starting with readily available and optically active ketone 16, 7-regioselective trimethylsilyl (TMS) enol ether formation followed by BF3 * OEt2 -promoted diastereoselective 1,4-addition (Michael reaction) and subsequent Robinson annulation [no stereochemistry] afforded bicyclic enone 17 in 47% overall yield.

Reagents and conditions: (a) TMSCl (3.0 equiv), HMDS (4.0 equiv), NaI (4.0 equiv), MeCN, 0 → 22 °C, 2 h; (b) MVK (3.0 equiv), BF3 * OEt2 (0.2 equiv), MeOH (1.0 equiv), CH3NO2, −20 °C, 1 h; (c)NaOMe (1.5 equiv, 1.0 M in MeOH), 45 °C, 5 h, 47% (three steps)