1: 1.) trimethyl orthoacetate, p-TsOH / 1.) CH2Cl2, CH3CN, RT, 1 h, 2.) CH3CN, -15 deg C, 3 h 2: 94 percent / TBAF / tetrahydrofuran / 3 h / Ambient temperature 3: 80 percent / (NH4)2Ce(NO3)6 / H2O; acetonitrile / 1 h / 0 °C 4: 82 percent / methanolic NaHCO3, Na2CO3 / Ambient temperature View Scheme

1: 1.) trimethyl orthoacetate, p-TsOH / 1.) CH2Cl2, CH3CN, RT, 1 h, 2.) CH3CN, -15 deg C, 3 h 2: 94 percent / TBAF / tetrahydrofuran / 3 h / Ambient temperature 3: 80 percent / (NH4)2Ce(NO3)6 / H2O; acetonitrile / 1 h / 0 °C View Scheme