Triethylamine → tert-butyl(S)-6-tert-butoxycarbonylamino-2-[3-((R)-1-carboxy-2-cyclohexyl-ethyl)-ureido]-hexanoate

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Reaction Steps

Commercial tert-butyl(S)-2-amino-6-tert-butoxycarbonylaminohexanoate hydrochloride (1.95 g, 5.75 mmol) was mixed in 30 ml of DMF with NEt3 (0.8 ml, 5.754 mmol) and 1,1′-carbonyldiimidazole (0.933 g, 5.754 mmol) and stirred at RT for 30 min. Then (R)-2-amino-3-cyclohexylpropanoic acid trifluoroacetate (1.64 g, 5.754 mmol) and NEt3 (1.6 ml, 11.5 mmol) were added, and the mixture was heated at 80° C. until the imidazolide formed as intermediate was completely converted. The product was purified by flash chromatography on silica gel (CH2Cl2/MeOH gradient). Yield: 2.1 g (73%) of tert-butyl(S)-6-tert-butoxycarbonylamino-2-[3-((R)-1-carboxy-2-cyclohexylethyl)-ureido]-hexanoate.

Provenance & Evidence