C(NC(C)C)(C)C.C([Li])CCC.[CH3:13][CH2:14][C:15](=[O:18])[CH2:16][CH3:17].[C:19]([O:23][C:24]([N:26]1[CH2:31][CH2:30][CH:29]([CH:32]=[O:33])[CH2:28][CH2:27]1)=[O:25])([CH3:22])([CH3:21])[CH3:20]>C1COCC1>[C:19]([O:23][C:24]([N:26]1[CH2:31][CH2:30][CH:29]([CH:32]([OH:33])[CH:14]([CH3:13])[C:15](=[O:18])[CH2:16][CH3:17])[CH2:28][CH2:27]1)=[O:25])([CH3:22])([CH3:21])[CH3:20]
A solution of diisopropylamine (0.63 mL, 4.5 mmol) in THF (16 mL) at 0° C. was treated with 1.6 M n-butyllithium in sol'n in hexanes (2.8 mL). The resulting solution was stirred at 0° C. for 10 min, then cooled to −78° C. 3-Pentanone (0.41 mL, 4.1 mmol) was added and the resulting mixture was stirred cold for 1 h. A solution of 1-(t-butoxycarbonyl)-4-formylpiperidine (435 mg, 2.05 mmol) (from Step B) in THF (3 mL) was then added. After 15 min, the reaction was quenched with sat'd ammonium chloride (25 mL) and extracted with ether (100 mL). The extract was dried over magnesium sulfate and concentrated. MPLC (Biotage) on a 40S silica cartridge using 4:1 v/v, then 3:2 v/v hexanes/ethyl acetate as the eluent afforded 517 mg (85%) of the title compound.
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