(S)-3-tert-Butoxycarbonylamino-2-hydroxy-pentanoic acid → (S)-2-Amino-1-(3-cyclopropyl-1,2,4-oxadiazol-5-yl)-butan-1-ol

Participants

Reaction Conditions

Reaction Steps

A solution of (S)-3-tert-Butoxycarbonylamino-2-hydroxy-pentanoic acid (2.00 g, 8.57 mmol) and N-Hydroxy-cyclopropanecarboxamidine (1.03 g, 10.29 mmol) in dichloromethane (20 mL) was stirred at 0° C. and 1.25 equivalents of N-cyclohexylcarbodiimide-N′-methyl polystyrene (1.70 mmol/g, 6.30 g, 10.72 mmol) was added in portions. The reaction mixture stirred under nitrogen for three hours while warming to 15° C. The reaction mixture was filtered, the resin washed with dichloromethane and the filtrate evaporated under vacuum to dryness. [LC/MS m/z=338 (M+H+Na)] The residue was dissolved in tetrahydrofuran (20 mL) and heated in a microwave reactor (Smith Creator) at 160° C. for three minutes, cooled to room temperature and evaporated under vacuum to dryness. [LC/MS m/z=320 (M+H+Na)]. The residue was dissolved in dichloromethane (50 mL) and stirred at room temperature as a 50 mL solution of 50% trifluoroacetic acid in dichloromethane was added dropwise. After three hours the reaction was evaporated under vacuum to dryness and dissolved in 50 mL of dichloromethane again. Three equivalents of Silicycle triamine-3 was added and the mixture stirred at room temperature overnight. The mixture was filtered and washed with dichloromethane. Evaporate under vacuum to give 1.04 g (61% overall). [LC/MS m/z=198 (M+H)]

Provenance & Evidence