A round bottom flask was charged with Fmoc-glycine (756 mg, 2543 μmol), 1H-benzo[d][1,2,3]triazol-1-ol (412 mg, 3052 μmol), (S)-methyl-4,4-difluoropyrrolidine-2-carboxylate TFA salt (710 mg, 2543 μmmol), Hunig's Base (2221 μl, 12717 μmol) and 10.2 mL DMF. The mixture was stirred for 5 min at RT, and benzotriazole-1-yl-oxy-tris-(dimethylamino)-phosphonium hexafluorophosphate (1350 mg, 3052 μmol) was added. The reaction mixture was stirred overnight at RT. The solution was diluted with DCM and washed with water. The organic layer was dried, filtered, and concentrated. The crude oil was purified by silica gel chromatography, 0-5% MeOH/DCM to provide (R)-methyl 1-(2-(((9H-fluoren-9-yl)methoxy)carbonyl)acetyl)-4,4-difluoropyrrolidine-2-carboxylate. MS: [M+H]=445.
