C(NC(C)C)(C)C.C([Li])CCC.[O:13]1[CH2:18][CH2:17][CH:16]([C:19]([O:21][CH3:22])=[O:20])[CH2:15][CH2:14]1.Br[CH2:24][C:25]([O:27][C:28]([CH3:31])([CH3:30])[CH3:29])=[O:26]>O1CCCC1.O>[C:28]([O:27][C:25](=[O:26])[CH2:24][C:16]1([C:19]([O:21][CH3:22])=[O:20])[CH2:17][CH2:18][O:13][CH2:14][CH2:15]1)([CH3:31])([CH3:30])[CH3:29]
Step 2 Diisopropylamine (1.28 mL, 9.16 mmol) was diluted with tetrahydrofuran (2 mL) and cooled to −78° C. n-Butyllithium (2.5 M, 3.66 mL, 9.16 mmol) was added dropwise, and the solution was allowed to stir for 1 h. Methyl tetrahydro-2H-pyran-4-carboxylate (1.1 g, 7.63 mmol) was added as a solution in tetrahydrofuran (1.5 mL) at −78° C. The mixture was allowed to warm to −35° C. and stirred for 1 h. tert-Butyl bromoacetate (1.58 mL, 10.7 mmol) was added neat at −35° C. The mixture was allowed to warm to 0° C. and stirred for 2 h. The mixture was stirred at rt overnight. Water was added at 0° C. and the mixture extracted with ethyl acetate. The organic phase was washed with brine, and dried over sodium sulfate. The crude product was purified by flash chromatography (Biotage Flash 40M, 6:1 hexane/ethyl acetate) to afford methyl 4-(2-tert-butoxy-2-oxoethyl)tetrahydro-2H-pyran-4-carboxylate (1.12 g, 56%). LC-MS ret. time 2.47 min, m/z 258.7 (MH+); 1H NMR (300 MHz, CDCl3) δ 1.38 (s, 9H), 1.52-1.61 (m, 2H), 2.00-2.07 (m, 2H), 2.50 (s, 2H), 3.52-3.60 (m, 2H), 3.70 (s, 3H), 3.71-3.77 (m, 2H).
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