Reaktionsschritte
To a solution of 4-Pyridin-2-ylmethyl-piperazine-1-carboxylic acid tert-butyl ester (prepared from 1-Pyridin-2-ylmethyl-piperazine according to the literature: J. Med. Chem. (1993), 36, 2984) (2.00 g, 7.21 mmol) in THF (15 mL) was added n-BuLi (1.6 M in hexanes, 5.0 mL, 7.9 mmol) at −78° C. The mixture was allowed to warm to room temperature and stirred for 30 minutes. The solution was then cooled to −78° C. and a solution of diethyl ethoxymethylenemalonate (1.72 g, 7.93 mmol) in THF (2 mL) was added dropwise. The reaction mixture was allowed to warm to 0° C. over 1 hour and stirred at 0° C. for 1 hour. The reaction was poured into water and extracted with EtOAc. The combined organic layers were washed with brine, dried and concentrated. The residue was purified by column chromatography (hexanes:EtOAc, 8:1 to 1; 1) to give 2-[2-(4-tert-Butoxycarbonyl-piperazin-1-yl)-1-ethoxy-2-pyridin-2-yl-ethyl]-malonic acid diethyl ester (2.40 g, 67%) as a mixture of diastereomers. Diastereomer 1: 1H NMR (CDCl3, 400 MHz) δ 8.55 (d, J=4.4 Hz, 1H), 7.63 (td, J=7.6 Hz, J=1.6 Hz, 1H), 7.21 (d, J=7.6 Hz, 1H), 7.16 (dd, J=7.6 Hz, J=1.6 Hz, 1H), 4.74 (m, 1H), 4.16 (m, 5H), 3.75 (q, J=7.2 Hz, 2H), 3.52 (d, J=4.4 Hz, 1H), 3.38 (m, 4H), 2.67 (m, 2H), 2.44 (m, 2H), 1.40 (s, 9H), 1.22 (m, 6H), 1.44 (t, J=7.2 Hz, 3H). LCMS (APCI+) m/z 494 [M+H]+; Rt=3.61 min. Diastereomer 2: 1H NMR (CDCl3, 400 MHz) δ 8.58 (d, J=4.8 Hz, 1H), 7.59 (td, J=7.6 Hz, J=1.6 Hz, 1H), 7.15 (dd, J=7.6 Hz, J=1.6 Hz, 1H), 7.08 (d, J=8.0 Hz, 1H), 4.91 (m, 1H), 4.16 (m, 5H), 3.53 (m, 1H), 3.22 (m, 6H), 2.50 (m, 2H), 2.19 (m, 2H), 1.34 (s, 9H), 1.24 (m, 6H), 0.69 (t, J=7.2 Hz, 3H). LCMS (APCI+) m/z 494 [M+H]+; Rt=3.62 min.
