Scheme 1. Unsuccessful strategies for the selective derivatization of ratjadone A. Reagents and conditions: (a) TBSOTf (2.3 equiv.), 2,6-lutidine (2.6 equiv.), (CH₂Cl₂), –100 °C, 3 h, 62% brsm; (b) MsCI (3.3 equiv.), Py (4.0 equiv.), (CH₂Cl₂), 23 °C, 3.5 h, 98%; (c) NaN₃ (3.0 equiv.), (DMF); (d) DIAD (1.1 equiv.), PPh₃ (1.15 equiv.), DPPA (1.0 equiv.), (THF); (e) mCPBA (1.0 equiv., NaHCO₃ (1.05 equiv.), (CH₂Cl₂ : H₂O/3 : 1), 0 °C or –10 °C; (f) DMDO (1.1 equiv.), (CH₂Cl₂), –30 °C; (g) O₃, (CH₂C1₂ : MeOH/9 : 1), –78 °C, PPh₃ (xs); (h) OsO₄ (0.01 equiv.), NMO (1.0 equiv.) or PNO (1.0 equiv.), (CH₂Cl₂), 0 °C or –10 °C.