Scheme 41.

Synthesis of (3S)- and (3R)-296, as reported by Hong et al. [116]. Reagents and conditions: i. 292 (1.1 equiv.), NaN(TMS)₂ (1.0 equiv.), THF, −78 °C, rt, 15 min; ii. N-Bu₄NF (6 equiv.), THF, rt, 3 h; iii. TBSCl (2 equiv), imidazole (3 equiv), CH₂Cl₂, rt, 30min; iv. t-BuOOH (1.5 equiv), Ti(O-i-Pr)₄ (1.0 equiv.), l-(+)-DIPT(1.2 equiv.), CH₂Cl₂,−18 °C, 5 h; v. TBSOTf (1.5 equiv.), 2,6-lutidine (3 equiv.), CH₂Cl₂, 10 min, 97%; vi. tBuOOH (1.5 equiv.), Ti(O-i-Pr)₄ (1.0 equiv.), l-(+)-DIPT (1.2 equiv.), CH₂Cl₂,−18 °C, 3 h; vii. TBSOTf, 2,6-lutidine, CH₂Cl₂, 10 min, 97%.