1: PPTs / ethanol / 20 °C 2: Ti(i-PrO)4; L-(+)-DET; t-BuOOH / CH2Cl2 / -20 °C 3: I2; Ph3P; imidazole / diethyl ether; acetonitrile / 0 °C 4: NaBH3(CN) / tetrahydrofuran; hexamethylphosphoric acid triamide / 60 °C 5: TBAF / tetrahydrofuran View Scheme