To a solution of (R)-5-methyl-4-((S)-2-methylpiperazin-1-yl)-6,7-dihydro-5H-cyclopenta[d]pyrimidine dihydrochloride (32 mg, 0.14 mmol) in DCM (5 mL) were added triethylamine (1 mL), (R)-2-(tert-butoxycarbonylamino)-3-(4-chloro-3-fluorophenyl)propanoic acid (44 mg, 0.14 mmol) and HBTU (52 mg, 0.14 mmol). The mixture was stirred at room temperature for 1 hour. The solvent was removed and the residue was purified by silica gel chromatography, eluting with ethyl acetate to afford tert-butyl (R)-3-(4-chloro-3-fluorophenyl)-1-((S)-3-methyl-4-((R)-5-methyl-6,7-dihydro-5H-cyclopenta[d]pyrimidin-4-yl)piperazin-1-yl)-1-oxopropan-2-ylcarbamate (55 mg, 82%). 1H NMR (CDCl3, 400 MHz) δ 8.46 (s, 1H), 7.31-6.85 (m, 3H), 5.45-5.18 (m, 1H), 4.90-4.60 (m, 2H), 4.50-4.30 (m, 1H), 4.20-4.00 (m, 1H), 3.90-3.60 (m, 2H), 3.40 (m, 1H), 3.20-2.70 (m, 2H), 2.24 (m, 1H), 1.70 (m, 1H), 1.42 (s, 9H), 1.30-0.98 (m, 6H). MS (APCI+) [M+H] +532.
