C([C:3]([CH2:14][CH3:15])(P(=O)=O)[C:4]([O:6][C:7]([CH3:10])([CH3:9])[CH3:8])=[O:5])C.[H-].[Na+].O=C1C[CH2:23][CH:22]([C:25]2[CH:35]=[CH:34][C:28]([C:29]([O:31][CH2:32][CH3:33])=[O:30])=[CH:27][CH:26]=2)[CH2:21][CH2:20]1>CN(C)C=O>[C:7]([O:6][C:4]([CH:3]=[C:14]1[CH2:15][CH2:23][CH:22]([C:25]2[CH:26]=[CH:27][C:28]([C:29]([O:31][CH2:32][CH3:33])=[O:30])=[CH:34][CH:35]=2)[CH2:21][CH2:20]1)=[O:5])([CH3:8])([CH3:9])[CH3:10]5.63 g of tert-butyl diethylphosphoacetate (20.3 mmol, 1 eq.) are placed in 20 mL of dimethylformamide with stirring. The solution is cooled to a temperature of 4° C. by placing it in an ice bath, and 0.536 g of sodium hydride (22.33 mmol, 1.1 eq.) is then added portionwise. After 30 minutes, 5 g of ethyl 4-(4-oxo-cyclohexyl)benzoate (20.3 mmol, 1 eq.) are added and the ice bath is removed. After stirring for 1 hour, the flask is placed in an ice bath to cool the reaction medium to a temperature of 4° C., and 0.049 g of sodium hydride (2.04 mmol, 0.1 eq.) is added. The ice bath is removed and, after 30 minutes, the mixture is poured into 200 mL of 1N potassium hydrogen sulfate and extracted with 300 mL of ethyl ether. The organic phase is washed 4 times with brine. The organic phase is dried over sodium sulfate and evaporated. The residue is chromatographed on silica gel, eluting with a gradient of methanol in dichloromethane ranging from 0% to 5%. 5.04 g of ethyl 4-(4-tert-butoxycarbonylmethylenecyclohexyl)benzoate are obtained.
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