Ethyl Acetate → HCID 66744319, compound

Participants

Reaction Conditions

Reaction Steps

{4-[5-((S)-1-tert-Butoxycarbonylamino-but-3-enyl)-1,3,4-oxadiazol-2-yl]-3-nitro-phenyl}-carbamic acid methyl ester: 168B (0.3 g, 0.393 mmol) and (S)-2-(tert-butoxycarbonylamino)pent-4-enoic acid (0.085 g, 0.393 mmol) were dissolved in DMF (2 mL) in a 15 mL rbf and TEA (0.274 mL, 1.967 mmol) was added. Mixture was stirred under nitrogen at room temperature while propane phosphonic acid anhydride (T3P), 50% in EtOAc (0.293 mL, 0.983 mmol) was added dropwise. The flask was fitted with a reflux condenser, and the resulting mixture was stirred in an 80° C. oil bath for 5 h. Reaction mixture was poured into ice water and extracted 3× with EtOAc. Combined extracts were washed with sat'd aq. NaHCO3, water and brine, dried over anh. Na2SO4, filtered and evaporated to provide {4-[N′-((S)-2-tert-butoxycarbonylamino-pent-4-enoyl)-hydrazinocarbonyl]-3-nitro-phenyl}-carbamic acid methyl ester, (0.46 g, 86%) as a light yellow solid which was used without further purification. The solid (0.46 g, 1.019 mmol) was dissolved in anhydrous THF (20 mL) under argon and the solution transferred to a 75 mL pressure flask. Burgess reagent (1.33 g, 5.58 mmol) was added, the flask was sealed with a pressure relief cap and then heated in a 75° C. oil bath for 2 h behind a blast shield then left standing overnight at room temperature. Reaction mixture was evaporated on rotary evaporator. Residue was purified by normal phase chromatography to give 168C as a light yellow foam (0.315 g, 71.3%). MS (ESI) m/z: 434.3 (M+H)+ 378.3 (M+H−tBu)+.

Provenance & Evidence