Scheme 3. Reaction conditions: (1) H₂O₂ (1.5 equiv.), Na₂CO₃ (1.5 equiv.), EtOH, 45 °C, 2 h. (2) DIBAL (1.0 equiv.), THF, −78 °C, 3 h. (3) CH₃MgCl (2.0 equiv.), THF, room temperature, 3 h. (4) Methyltriphenylphosphonium bromide (2.0 equiv.), t-BuOK (2.0 equiv.), THF, room temperature, 6 h.