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Synthesis of C9-methoxy analogues 36 and 38–40. a) Me3O·BF4, Proton Sponge, CH2Cl2, 20 °C, 70 min; b) Me3O·BF4, Proton Sponge, CH2Cl2, 20 °C, 45 min; c) 3N HCl, MeOH, 0 → 20 °C, 16 h; d) HF·py, pyridine, THF, 0 → 20 °C, 3 d. e) NaHMDS, THF, −78 °C, 10 min; 29 or 30, −78 → 0 °C, 30 min; f) HF·py, pyridine, THF, 0 → 20 °C, 3 d.
