1,1'-Carbonyldiimidazole → (4S,5R)-ethyl 4-((tert-butoxycarbonyl)amino)-5-((tert-butyldimethylsilyl)oxy)-3-oxohexanoate

Participants

Reaction Conditions

Reaction Steps

A solution of (2S,3R)-2-((tert-butoxycarbonyl)amino)-3-((tert-butyldimethylsilyl)oxy)butanoic acid (614b) (1.01 g, 3.03 mmol) in THF (10 mL) was treated with 1,1′-carbonyldiimidazole (Aldrich) (0.59 g, 3.63 mmol) and heated at 60° C. for 2 h. A mixture of potassium ethyl malonate (Aldrich) (1.03 g, 6.06 mmol) and magnesium chloride (Aldrich) (0.58 g, 6.06 mmol) was added to the solution and heating was continued at 50° C. for 6 d. The suspension was extracted into EtOAc (2×100 mL) from saturated brine (100 mL) containing 1.0 M aq. HCl (25 mL). The combined organic extracts were washed with saturated aq. NaHCO3 (100 mL), back-extracting with EtOAc (100 mL). The organic extracts were dried (MgSO4) and concentrated to give (4S,5R)-ethyl 4-((tert-butoxycarbonyl)amino)-5-((tert-butyldimethylsilyl)oxy)-3-oxohexanoate (614) (995 mg, 2.46 mmol, 81% yield) as a pale yellow oil. LC-MS m/z 426.0, [M+Na]+.

Provenance & Evidence