1: 1.) DMSO,(COCl)2, Et3N, 2.) CSA / 1.) CH2Cl2, 2.) CH2Cl2, room temperature 2: (C6H11)2NMgBr / methanol / -55 °C 3: DDQ / CH2Cl2 / 1.5 h / Ambient temperature; buffer (pH 6.86) View Scheme