In an inert atmosphere, trans-4-(trifluoromethyl)cinnamic acid (28 mg, 0.13 mmol) was dissolved in DCM (0.5 mL) followed by the addition of 1-chloro-N,N,2-trimethylpropenylamine (19.4 mg, 0.145 mmol). The mixture was stirred at rt for 30 min followed by the addition of DIPEA (34 mg, 0.26 mmol) and 1-(4-benzyl-piperazin-1-yl)-2-(4-butoxy-benzylamino)-(S)-3-phenyl-propan-1-one (63 mg, 0.13 mmol). Stirring was continued for 30 min. The mixture was concentrated in vacuo and the residue was directly purified by prep. HPLC to give 51 mg (57%) of N—[(S)-1-benzyl-2-(4-benzyl-piperazin-1-yl)-2-oxo-ethyl]-N-(4-butoxy-benzyl)-3-(4-trifluoromethyl-phenyl)-acrylamide. LC-MS: tR=1.02 min; [M+H]+=684.49.
