4-tert-Butyl hydrogen N-((phenylmethoxy)carbonyl)-L-aspartate → 4-((S)-2-benzyloxycarbonylamino-3-tert-butoxycarbonyl-propionyl)-piperazine-1-carboxylic acid ethyl ester

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Reaction Steps

To a solution of 15.4 g (S)-2-Benzyloxycarbonylamino-succinic acid 4-tert-butyl ester, 24.4 ml NEM and 15.6 g TOTU in 80 ml DMF 7.5 g piperazine-1-carboxylic acid ethyl ester were added at RT and stirred for 16 h. The reaction mixture was then diluted with ethyl acetate and washed with aqueous LiCl (4 w/w) and saturated aqueous sodium hydrogen carbonate. The organic phase was dried over MgSO4 and the solvents were removed under reduced pressure. The crude product was used in the subsequent reaction. Yield: 23.0 g.

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