1: 1.) O3; 2.) Me2S / 1.) CH2Cl2, -78 deg C; 2.) reflux 2: NaOH / methanol / Heating 3: DIBAH / diethyl ether / -100 °C 4: Et2Zn / toluene / 60 °C 5: PCC / CH2Cl2 6: tetrahydrofuran View Scheme