Dimethylamine → (2S,4E)-6-(Benzyloxy)-2-isopropylhex-4-enoic acid dimethylamide

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Reaction Steps

7.75 ml of oxalyl chloride (87 mmol) and 0.11 ml of N,N-dimethylformamide (1.4 mmol) were added to a solution of 19.02 g of (2S,4E)-6-(benzyloxy)-2-isopropylhex-4-enoic acid obtained in Example (1b) (72.5 mmol) in methylene chloride (180 ml) at room temperature. The mixture was stirred at the same temperature for one hour to prepare a solution of (2S,4E)-6-(benzyloxy)-2-isopropylhex-4-enoic acid chloride in methylene chloride. The solution of acid chloride in methylene chloride above was added to a solution of 76 ml of a 50% dimethylamine aqueous solution (725 mmol) in a mixed solvent of tetrahydrofuran (180 ml) and t-butanol under ice-cooling over one hour, and the mixture was stirred at the same temperature for 20 minutes. The reaction mixture was concentrated under reduced pressure to about ⅕ of the volume and diluted with 150 ml of water, followed by extraction with ethyl acetate. Then, the organic layer was washed with water, a saturated sodium bicarbonate aqueous solution and brine and dried over anhydrous magnesium sulfate. After filtration, the solvent was evaporated under reduced pressure to obtain 21.20 g of the crude title compound.

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