Imidazole → 5(S)-[1(S)-(Boc-amino)-2-phenylethyl]-3(R)-phenylmethyldihydrofuran-2-(3H)one

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Reaction Steps

8 g of imidazole and 10 g of tert-butyldimethylchlorosilane are added, with stirring, to a solution of 6.35 g of 5(S)-(Boc-amino)-4(S)-hydroxy-6-phenyl-2(R)-phenylmethylhexanoic acid in 90 ml of DMF. After being stirred for 18 hours at room temperature, the clear yellow solution is poured onto ice-water and extracted three times using 250 ml of ethyl acetate each time. The combined extracts are washed in succession three times with 10% citric acid, once with water, three times with aqueous saturated sodium hydrogen carbonate solution, once with water and finally with brine. After drying over sodium sulfate, the solvent is evaporated and the resulting tert-butyldimethylsilyl ether (13.5 g) is dissolved in 53 ml of THF and treated with 53 ml of acetic acid and 20 ml of water. After being stirred for 3 hours at room temperature, the mixture is poured onto water and extracted three times with ether. The combined ether extracts are washed twice with water and once with brine and dried over sodium sulfate. After concentration, the crude product is purified by column chromatography (SiO2, hexane/ethyl acetate: 3.5/1.5) and the title compound obtained. TLC Rf (D)=0.37; FAB-MS (M+H)+ =528.

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