Trifluoroacetic acid → HCID 68900372, compound

A mixture of 15A (2.02 g, 7.5 mmol), TFA salt of (3R,4R)-methyl 4-(allyloxycarbonyl)piperidine-3-carboxylate (2.8 g, 7.87 mmol), (prepared as described in U.S. patent application Ser. No. 11/019,901) and TEA (3.14 ml, 22.5 mmol) in dichloroethane (50 ml) was heated at 70° C. for 1 h. After cooling to room temperature, the reaction mixture was washed with water, dried and concentrated in vacuo. Purification using silica gel flash column (DCM/MeOH=98/2) gave 15B (2.91 g, 90%) as a solid. The compound has an analytical HPLC retention time=1.547 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=431+.