(RS)-2-Carboxymethylpiperazine-1,4-dicarboxylic acid 4-tert-butyl ester 1-(9H-fluoren-9-ylmethyl) ester from description 109 (2.0 g) was dissolved in DMF (25 ml) and stirred at room temperature under argon for 3 days in the presence of potassium carbonate (0.697 g) and 2-bromo-4′-fluoroacetophenone (0.930 g). The reaction solution was then partitioned between ethyl acetate and water the organic solution was washed with brine, dried (MgSO4) and evaporated. The crude product was chromatographed over silica gel, eluting with 25 to 100% ethyl acetate in hexane, followed by 10% ethanol in ethyl acetate. The title compound was obtained as a pale yellow solid (0.887 g), mass spectrum (API+) 381 [MH+], C19H25FN2O5 requires 380.
