A mixture of 14A (80 mg, 0.223 mmol) and 3-methoxyaniline (18.6 mg, 0.151 mmol) in CH3CN (1.5 ml) was heated at 55° C. for 2 h. After cooling to room temperature, 4-N-Boc-aminopiperidine (300 mg, 1.5 mmol) was added and the mixture was heated at 60° C. overnight. The reaction mixture was concentrated in vacuo and the residue was purified by prep HPLC. The desired fraction was concentrated and the resulting residue was dissolved in a mixture of TFA/DCM (1 ml/1 ml) and stirred at room temperature for 1 h, then concentrated. The residue was purified by SCX column, followed by silica gel flash column (DCM/MeOH/NH4OH=90/10/1) to give 14B (9.5 mg, 17%). The compound has an analytical HPLC retention time=1.288 min (Chromolith SpeedROD column 4.6×50 mm, 10-90% aqueous methanol containing 0.1% TFA over 4 minutes, 4 mL/min, monitoring at 254 nm) and a LC/MS M++H=364+.
