[OH-].[Na+].[CH2:3]([O:5][C:6](=[O:13])[CH2:7][C:8](=[O:12])[CH:9]([CH3:11])[CH3:10])[CH3:4].Cl[CH:15](OCC)[CH2:16]Cl>O.C(OCC)C>[CH2:3]([O:5][C:6]([C:7]1[CH:16]=[CH:15][O:12][C:8]=1[CH:9]([CH3:10])[CH3:11])=[O:13])[CH3:4]An ice-chilled solution of sodium hydroxide (1.9 g) in water (25 ml) was added, during 40 minutes, to a stirred solution of 4-methyl-3-oxo-pentanoic acid ethyl ester (3 g, 18.96 mmoles) and 1,2-dichloro-1-ethoxy-ethane (3.3 g, 35.19 mmole) in diethyl ether (15 ml) with ice bath cooling. When the addition was complete the mixture was stirred rapidly for 1 hour, then the ethereal layer was separated, washed with water and dried. Evaporation of the solvent gave a yellow oil, which was purified by flash chromatography using a gradient elution from neat pentane to pentane/diethyl ether 9:1 v/v as eluent, to afford compound 82 as an oil (2.4 g).
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