Fig. 3: Enantioselective synthesis of the tropinone building block 16.

Reagents and conditions: a 19, MeOH, rt, 3 d, 90%; b (COCl)2, DMSO, Et3N, CH2Cl2, −78 °C; c NaH, 21, THF, 0 °C to reflux, 60% (for 2 steps); d TMSOTf, Et3N, CH2Cl2, 0 °C, e Tf2O, DTBMP, ZnBr2, CH2Cl2, −78 °C to rt, 78% (for 2 steps from cis-17).