CN1CCN(C)[C:4](=[O:9])[C:3]1=[O:10].[CH3:11][CH:12]([CH2:16][CH2:17][CH2:18][CH:19]([CH3:21])[CH3:20])[CH2:13][CH2:14][Li].[CH3:22][CH:23]([CH2:27][CH2:28][CH2:29][CH:30]([CH3:32])[CH3:31])[CH2:24][CH2:25]Br.[Li].Cl>CCOCC>[CH3:31][CH:30]([CH2:29][CH2:28][CH2:27][CH:23]([CH3:22])[CH2:24][CH2:25][C:4](=[O:9])[C:3](=[O:10])[CH2:14][CH2:13][CH:12]([CH3:11])[CH2:16][CH2:17][CH2:18][CH:19]([CH3:21])[CH3:20])[CH3:32]
To a suspension of 1,4-dimethylpiperazine-2,3-dione (2.08 g, 1.46×10−2 mol) in 50 ml of dry Et2O was added 3,7-dimethyloctyl lithium (0.45M solution in Et2O, 65 ml, 2.9×10−2 mol, freshly prepared from 3,7-dimethyloctyl bromide and lithium) by a syringe. After 40 min of stirring at room temperature under N2, the solution was hydrolyzed with 100 ml of 10% HCl and extracted with CHCl3. The combined organic layers were washed with saturated aqueous NaHCO3 and dried over Na2SO4. The product was chromatographed on silica gel with 3:1 hexane:CHCl3 as the eluent. Yield=4.446 g (91% based on 65 ml of 0.45M 3,7-dimethyloctyl lithium in Et2O). 1H NMR (250 MHz, CDCl3): δ 2.69-2.78 (m, 4H, —CH2CO), 1.06-1.65 (m, 20H, (CH3)2CHCH2CH2CH2CH(CH3)CH2CH2CO), 0.87 (d, 6H, J=9.0 Hz, —CH3), 0.86 (d, 12H, J=9.5 Hz, —CH3). CI MS m/z: 338.3175 (M+) (calcd 338.318).
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