Cesium carbonate → 4-{(S)-2-[(5-Benzyloxycarbonylmethoxy-1-phenyl-1H-pyrazole-3-carbonyl)-amino]-4-tert-butoxycarbonyl-butyryl}-piperazine-1-carboxylic acid ethyl ester

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Reaction Steps

To a solution of 14.5 g 4-{(S)-4-tert-butoxycarbonyl-2-[(5-hydroxy-1-phenyl-1H-pyrazole-3-carbonyl)-amino]-butyryl}-piperazine-1-carboxylic acid ethyl ester in 110 ml DMF were added 4.5 ml benzyl bromoacetate and 17.8 g cesium carbonate. After stirring at RT for 12 h the solution was reduced to a volume of 50 ml, diluted with 400 ml ethyl acetate and extracted with aqueous LiCl (4% w/w). The crude product obtained after evaporation of the solvent was purified by flash chromatography on silica eluting with a gradient of n-heptane/ethyl acetate. Yield: 13.2 g yellowish amorphous solid.

Provenance & Evidence