Imidazole → ethyl 1(R)-[1-[2(S)-(tert-butoxycarbonylamino)-3-[N-cyclopropyl-N-(pent-4-enyl)amino]propanoyl]-4(R)-(tert-butyldimethylsilyloxy)pyrrolidine-2(S)-carboxamido]-2(S)-vinylcyclopropanecarboxylate

Participants

Reaction Steps

To a mixture of ethyl 1(R)-[1-[2(S)-(tert-butoxycarbonylamino)-3-[N-cyclopropyl-N-(pent-4-enyl)amino]propanoyl]-4(R)-hydroxypyrrolidine-2(S)-carboxamido]-2(S)-vinylcyclopropanecarboxylate (1.55 g, 2.75 mmol.) in 10 mL of DMF was added imidazole (0.47 g, 6.88 mmol.) and tert-butyldimethylsilyl chloride (826 mg, 5.50 mmol.). The mixture was stirred at rt for 18 h, concentrated in vacuo, and partitioned between ethyl acetate and water. The organic phase was dried over magnesium sulfate, and concentrated in vacuo to obtain an off-white solid. Flash chromatography (eluting with methylene chloride and then ethyl acetate) gave ethyl 1(R)-[1-[2(S)-(tert-butoxycarbonylamino)-3-[N-cyclopropyl-N-(pent-4-enyl)amino]propanoyl]-4(R)-(tert-butyldimethylsilyloxy)pyrrolidine-2(S)-carboxamido]-2(S)-vinylcyclopropanecarboxylate as a white solid (1.75 g, 94%): LC-MS (Phenomenex 10 μm C18 HPLC column: 3.0×50 mm length. Gradient: 100% Solvent A/0% Solvent B to 0% Solvent A/100% Solvent B. Gradient time: 2 min. Hold time: 1 min. Flow rate: 5 mL/min. Detector Wavelength: 220 nM. Solvent A: 10% MeOH/90% H2O/0.1% TFA. Solvent B: 10% H2O/90% MeOH/0.1% TFA.) (Retention time: 2.51 min), MS m/z 677 (M++1).

Provenance & Evidence