A solution of 4.78 g (0.025 mol) of N-acetyl-L-methionine in CH2Cl2: acetonitrile (120 ml) was cooled to 0° C. To this solution was added 5.36 g (0.025 mol) of dicyclohexylcarbodiimide (DCC) followed by the rapid addition of 3.90 g (0.021 mol) of N-t-butoxycarbonylpiperazine in 6 ml of dichloromethane. The progress of the reaction was followed on silica gel TLC plates developed with 4:1 acetonitrile: tetrahydrofuran and visualized with either iodine or ninhydrin spray. The reaction was complete within 2 h. A few drops of glacial acetic acid were added to the reaction mixture and the solvent was removed on a rotary evaporator. The residue was taken up in ether and filtered. The clear filtrate was washed with dilute acid followed by dilute base. The organic layer was separated, dried over anhydrous sodium sulfate, filtered, and evaporated to give 8.2 g of 1-(t-butoxycarbonyl) -4-(N-acetyl-L-methionyl)piperazine, a colorless oil which required no further purification: IR (film) 3304, 3058, 2973, 2931, 2868, 1701, 1645, 1539, 1420, 1237, 1173 cm−1; NMR (CDCl3) δ 1.47 (s, 9 H), 1.80 (m, 2 H), 2.02 (s, 3 H), 2.10 (s, 3 H), 2.46 (m, 2 H), 3.53 (m, 8 H), 5.10 (M, 1 H), 6.35 (b, 0.5 H), 6.43 (b, 0.5 H).
