(R)-4-Carboxymethyl-2-methyl-piperazine-1-carboxylic acid tert-butyl ester (100 mg, 0.39 mmol), 6-bromo indoline (100 mg, 0.43 mmol) and triethylamine (0.148 mL, 1.06 mmol) were dissolved in DCM (1.94 mL) at ambient temperature. PyBrop (199 mg, 0.43 mmol) was added and the reaction stirred for 18 h. The solvent was removed in vacuo and the residue purified by column chromatography on silica gel (gradient elution, 0-100% EtOAc/petrol), to give the title compound (97 mg, 52%) as a pale yellow oil. 1H NMR (Me-d3-OD): 8.32 (1H, s), 7.24-7.10 (2H, m), 5.50 (1H, s), 4.38-4.17 (3H, m), 3.83 (1H, d), 3.31 (1H, s), 3.17 (2H, t), 2.91 (1H, d), 2.81 (1H, d), 2.33 (1H, dd), 2.20-2.09 (1H, m), 1.48 (9H, s), 1.30 (3H, d).
