Hydrochloric Acid → (4S)-1-[(2S,3S)-3-(N,N-Dibenzylamino)-2-hydroxy-4-phenylbutyryl]-4-chloro-N-t-butyl-L-prolinamide

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Reaction Steps

12.2 g (0.04 mol) of (4S)-N-t-butoxycarbonyl-4-chloro-N-t-butyl-L-prolinamide were treated with 50 ml of a 4N solution of hydrogen chloride in dioxane, in order to remove the t-butoxycarbonyl group. The product thus obtained and 15.0 g (0.04 mol) of (2S,3S)-3-(N,N-dibenzylamino)-2-hydroxy-4-phenylbutyric acid were dissolved in 50 ml of dimethylformamide, and the solution was cooled with ice. 8.48 ml (52.0 mmol) of diethyl cyanophosphate, and then 11.2 ml (0.08 mmol) of triethylamine, were then added dropwise to the resulting mixture, which was then stirred for 1 day. At the end of this time, the reaction mixture was concentrated by evaporation under reduced pressure, and the concentrate was diluted with ethyl acetate. The diluted solution was washed with a 5% w/v aqueous solution of citric acid and with a 5% w/v aqueous solution of sodium hydrogencarbonate, in that order, after which it was dried over anhydrous sodium sulfate. The solvent was then removed by distillation under reduced pressure, and the resulting residue was purified by column chromatography, using a 1:1 by volume mixture of ethyl acetate and hexane as the eluent, to give 20.0 g of the title compound as a colorless powder, melting at 64°-67° C.

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