Into a Round bottom flask was added compound 20 (425.0 mg, 0.001203 mol) and Ether (8.0 mL, 0.076 mol) under an atmosphere of Nitrogen, −78 Celsius. Into the reaction mixture, was added 1.7 M of tert-Butyllithium in Heptane (1.5 mL) slowly. The reaction mixture was stirred at −78 Celsius for 90 minutes, followed by addition of benzyl chloroformate (0.20 mL, 0.0014 mol). 2 hours later at −78 Celsius, the reaction mixture was poured into water, extracted with EtOAc. The organic layer was washed with brine, dried over sodium sulfate, concentrated and purified with biotage to give product 21 (250 mg).
