Ammonium Acetate → [(S)-1-(2-{(4-borono-phenyl)-[(E)-(3-phenylacryloyl)]amino}acetyl)pyrrolidin-3-yl]carbamic acid, tert-butyl ester

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Reaction Steps

Sodium periodate (2.06 g, 9.6 mmol) and ammonium acetate (0.74 g, 9.6 mmol) in water (20 mL) were added to [(S)-1-(2-{[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]-[(E)-(3-phenylacryloyl)]amino}acetyl)pyrrolidin-3-yl]-carbamic acid, tert-butyl ester 4 (1.85 g, 3.2 mmol) in acetone (30 mL) and the reaction stirred at room temperature for 64 h. The reaction mixture was concentrated in vacuo and 1M NaOH was added. The mixture was stirred for 4 h and then shaken with dichloromethane and filtered. The two layers were separated and the NaOH layer washed with dichloromethane. The aqueous basic layer was acidified to pH1 with conc. hydrochloric acid and extracted with ethyl acetate (×2). The combined organic layers were washed with brine, dried (Na2SO4) and evaporated to dryness. The resultant residue was purified by flash column chromatography on silica gel, eluting with ethyl acetate→5% methanol/ethyl acetate→10% methanol/ethyl acetate→methanol, to give the title compound as a glass (1.26 g, 80%) which was used directly in the next stage.

Provenance & Evidence