In a round bottom flask was added CuI (0.54 mg, 2.8 μmol, 0.1 equivalents), Cs2CO3 (18.3 mg, 0.056 mmol, 2 equivalents), and tert-butyl (2R,5S)-2-(4-{[(6-bromopyridin-2-yl)methyl](methyl)carbamoyl}benzyl)-5-[(R)-{[tert-butyl(dimethyl)silyl]oxy}(phenyl)methyl]-pyrrolidine-1-carboxylate (20 mg, 0.028 mmol). The flask was evacuated and backfilled with nitrogen (3×) and then 2,4-pentadione (1.69 mg, 0.017 mmol, 0.6 equivalents), DMF (141 μL) and ammonium hydroxide (19.6 μL, 0.141 mmol, 5 equivalents) was added. The contents were transferred to a sealed tube under positive nitrogen pressure. The reaction was stirred and heated at 90° C. for 16 hours. The reaction was cooled and filtered over celite and washed with EtOAc. The EtOAc was washed with water and the aqueous layer was extracted with. EtOAc (3×). The organic extracts were then dried over Na2SO4, filtered, and concentrated in vacuo to afford the crude product (19 mg) that was taken directly onto the next step. LC-MS=646.3 (M+H)+.
