Scheme 1. Synthesis of Stereochemically Pure Diols 24–26.

Reagents and conditions: (a) potassium vinyltrifluoroborate, PdCl₂(dppf)–CH₂Cl₂, triethylamine (TEA), ethanol (EtOH), 140 °C, MW; (b) mCPBA, CH₂Cl₂, 0 °C (40–70% yield, 2 steps); (c) ChiralPac AD-H SFC chromatography, 10% EtOH/CO₂, flow rate 200 mL/min, 100 bar, 25 °C; (d) N-Boc-piperazine, EtOH, 150 °C, MW (50–90% yield); (e) (i) trifluoroacetic acid, CH₂C₂, rt, (ii) Na₂CO₃ (aq) (85–90% yield); (f) NBS, H₂O/t-butanol (2:1), 40 °C, then addition of NaOH at 0 °C (44–85% yield); (g) 20 + 22, EtOH, 150 °C, MW (58–92% yield).