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Asymmetric Synthesis of Functionalized Aza-Cyclic Amino Acids with Quaternary Stereocenters by a Phase-Transfer-Catalyzed Alkylation Strategy

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journal contribution
posted on 20.01.2005, 00:00 by Takashi Ooi, Takashi Miki, Keiji Maruoka
Practical asymmetric synthesis of functionalized aza-cyclic α-amino acid derivatives possessing quaternary stereocenters has been achieved by the phase-transfer-catalyzed alkylation of 2 or 3 using chiral quaternary ammonium bromide 1 as catalyst. Subsequent reduction and alkylation of the 3-keto carbonyl moiety of 4 proceeded with complete diastereochemical control to afford the corresponding β-hydroxy aza-cyclic α-amino acid derivatives having stereochemically defined consecutive quaternary carbon centers.