4-Nitrophenol → Nalpha-t-butoxycarbonyl-D-valine p-nitrophenyl ester

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Reaction Steps

Nα -t-Butoxycarbonyl-D-valine p-nitrophenyl ester is prepared from 5 g., 24 mmol, of Nα -t-butoxycarbonyl-D-valine, 4.8 g., 24 mmol, of dicyclohexylcarbodiimide and 3.4 g., 24 mmol, of p-nitrophenol dissolved in 25 ml. of dimethylformamide and the solution let stand at room temperature overnight. The solids are separated by filtration and the filtrate evaporated to dryness under reduced pressure. The residual oil is purified by chromatography on silica gel in methanol-benzene (5:95); 5 g.; [α]D23 +21° (c 1.0, methanol); ultraviolet in methanol λmax 270 E11 204.

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