C(OP([CH2:9][C:10]([O:12][C:13]([CH3:16])([CH3:15])[CH3:14])=[O:11])(OCC)=O)C.C([O-])(C)(C)C.[Na+].[CH:23]([C:25]1[CH:34]=[CH:33][C:28]([C:29]([O:31][CH3:32])=[O:30])=[C:27]([O:35][CH3:36])[CH:26]=1)=O.[Cl-].[NH4+]>O1CCCC1>[C:13]([O:12][C:10](/[CH:9]=[CH:23]/[C:25]1[CH:34]=[CH:33][C:28]([C:29]([O:31][CH3:32])=[O:30])=[C:27]([O:35][CH3:36])[CH:26]=1)=[O:11])([CH3:14])([CH3:15])[CH3:16]To 720 μL of tert-butyl diethylphosphonoacetate (1.1 equivalents) in 3 mL of tetrahydrofurane cooled to 0° C. under an inert atmosphere are added 307 mg of sodium tert-butanolate (1.15 equivalents). The whole is stirred for 30 minutes at 0° C. and then for 1 hour at room temperature. A solution cooled to 0-4° C. of 540 mg of aldehyde obtained in stage 3 in 1 ml of tetrahydrofurane is added dropwise to the previous mixture also cooled to 0° C. Stirring is maintained at this temperature for 30 minutes before letting the temperature rise back to room temperature for 2 hours. The medium is hydrolyzed with a saturated solution of ammonium chloride and extracted with ethyl acetate several times. The collected organic phases are washed with water, and then dried on magnesium sulfate, filtered and evaporated under reduced pressure. The reaction crude product is purified by chromatography on silica gel (petroleum ether/ethyl acetate: 95/5) leading to 500 mg of the expected product.
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