One-Pot Preparation of Enantiopure Fluorinated β-Amino Acid Precursors: Enantiopure Fluorinated β-Amino Acid Precursors
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A practical and convenient method for the efficient and regio- and stereoselective ring-opening of enantiopure monosubstituted epoxides by sodium azide under hydrolytic conditions is reported. The ringopening of enantiopure styryl and pyridyl (S)-epoxides by N3 in hot water takes place preferentially at the internal position with complete inversion of configuration to produce (R)-2-azido ethanols with up to 99% enantio- and regioselectivity, while the (S)-adamantyl oxirane provides mainly the (S)-1-adamantyl- 2-azido ethanol in excellent yield. In general, 1,2-amino ethanols were obtained in high yield and excellent enantiopurity by the reduction of the chiral 1,2-azido ethanols with PPh3 in water/THF, and then converted into the Boc or acetamide derivatives.more » « less