Benzyl chloroformate → 2-(t-Butyloxycarbonyl)amino-4S-hydroxy-5S-(benzyloxycarbonyl)amino-1,6-diphenyl-2-azahexane

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Reaction Steps

Under a nitrogen atmosphere, 220 mg (0.57 mmol) of 1-[2(S)-hydroxy-3(S)-amino-4-phenyl-butyl]-1-[phenylmethyl]-2-[tert-butoxycarbonyl]-hydrazine (=H-[PheNNPhe]-Boc, Example 30b) in 15 ml of dioxane/water 1:1 and 408 mg (2.9 mmol) of K2CO3 are reacted with 120 mg (0.69 mmol) of chloroformic acid benzyl ester for 16 h at RT. KHSO4 solution is added, the mixture is extracted with 3 portions of ethyl acetate, and the organic phases are washed with water and brine, dried with Na2SO4 and concentrated by evaporation. Digestion from hexane yields the pure title compound: TLC Rf (I)=0.52; tRet (V)=17.1 min; FAB-MS (M+H)+ =520.

Provenance & Evidence