4-Methylmorpholine → Ethyl 3-(5-{(1R)-4-cyclohexyl-1-[2-(hydroxyamino)-2-oxoethyl]butyl}-1,2,4-oxadiazol-3-yl)propanoate

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Reaction Steps

A solution of 3R)-6-cyclohexyl-3-[3-(3-ethoxy-3-oxopropyl)-1,2,4-oxadiazol-5-yl]hexanoic acid (Preparation 94) (110 mg, 0.30 mmol) and N-methylmorpholine (60 μl, 0.54 mmol) in anhydrous tetrahydrofuran (6 ml) was cooled to 0° C., treated with isobutyl chloroformate (42 μl, 0.32 mmol) and stirred under a nitrogen atmosphere for 2.5 hours. O-(Trimethylsilyl)hydroxylamine (120 μl, 1.00 mmol) was added and the mixture was stirred for 18 hours, being allowed to warm to room temperature over this time. The mixture was then treated with methanol and stirred at room temperature for 3 hours. The solvent was removed under reduced pressure. The residue was dissolved in ethyl acetate and washed with water and brine, dried over anhydrous sodium sulphate, filtered and the solvent removed under reduced pressure. The oil was purified by column chromatography on silica gel eluting with a gradient system of 100:0 (dichloromethane:methanol) gradually changing to 90:10 (dichloromethane:methanol) to afford the title compound as a yellow oil (94 mg).

Provenance & Evidence