Oxalyl chloride → 4-ethoxycarbonyl-(S,S)-2,4-dibenzylbutyryl chloride

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Reaction Steps

The starting material is prepared as follows: 4.0 g of (S,S)-2,4-dibenzylglutaric anhydride is refluxed in 40 ml of ethanol:toluene (3:2) overnight. The reaction mixture is concentrated to yield 4-ethoxycarbonyl-(S,S)-2,4-dibenzylbutyric acid as an oil. Oxalyl chloride (3.5 ml) is added to the solution of 4.5 g of 4-ethoxycarbonyl-(S,S)-2,4-dibenzylbutyric acid in 10 ml of methylene chloride. The mixture is stirred at room temperature overnight and evaporated to yield 4-ethoxycarbonyl-(S,S)-2,4-dibenzylbutyryl chloride, which is used as such without further purification.

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