CC(C)([O-])C.[K+].[C:7]1([CH:13]2[CH2:18][NH:17][C:16](=[O:19])[CH2:15][CH2:14]2)[CH:12]=[CH:11][CH:10]=[CH:9][CH:8]=1.Br[CH:21]([CH2:27][CH3:28])[C:22]([O:24][CH2:25][CH3:26])=[O:23].C(OCC)(=O)C>C1(C)C=CC=CC=1>[O:19]=[C:16]1[CH2:15][CH2:14][CH:13]([C:7]2[CH:8]=[CH:9][CH:10]=[CH:11][CH:12]=2)[CH2:18][N:17]1[CH:21]([CH2:27][CH3:28])[C:22]([O:24][CH2:25][CH3:26])=[O:23]
In a 1 l three necked flask fitted with reflux condenser, magnetic stirrer and dropping funnel under inert atmosphere, 9.8 g (87 mmoles) of potassium t-butoxide were suspended in 600 ml of dry toluene. 11.8 g (67 mmoles) of 5-phenyl-2-piperidinone 25 were added, and the mixture stirred for 30 min. 17 g (87 mmoles) of ethyl 2-bromobutanoate were added and the temperature raised to 70° C. for 5 hours. 600 ml of ethyl acetate were added, the solution was washed twice with brine, the organic phase dried over magnesium sulfate, filtered and concentrated to dryness. The residue was purified by PrepLC (1 kg SiO2, CH2Cl2/EtOH, 97.5/2.5) to give 3.7 g of pure ester 26 as a mixture of diastereomers, 70.4% yield.
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