CC([O-])(C)C.[K+].[CH3:7][C:8]1[CH:13]=[CH:12][C:11]([CH2:14][C:15]([O:17][C:18]([CH3:21])([CH3:20])[CH3:19])=[O:16])=[CH:10][CH:9]=1.[CH:22]1(Br)[CH2:26][CH2:25][CH2:24][CH2:23]1>CN(C=O)C>[CH:22]1([CH:14]([C:11]2[CH:10]=[CH:9][C:8]([CH3:7])=[CH:13][CH:12]=2)[C:15]([O:17][C:18]([CH3:21])([CH3:20])[CH3:19])=[O:16])[CH2:26][CH2:25][CH2:24][CH2:23]133.5 g (0.3 mol) of potassium tert-butylate are initially introduced into 100 ml of anhydrous DMF at 0° C., and 51.6 g (0.25 mol) of tert-butyl 4methylphenyl-acetate in 250 ml of anhydrous DMF are added dropwise. The mixture is stirred at 0° C. for 30 minutes, 32.2 ml (0.3 mol) of cyclopentyl bromide in 150 ml of anhydrous DMF are added dropwise at 5-15° C. and the mixture is stirred at 25° C. for 20 hours. After concentration, the residue is partitioned between water and diethyl ether and the ether phase is dried over sodium sulphate and concentrated. The product crystallizes out.
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