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Synthesis of Novel Enantiopure 4-Hydroxypipecolic Acid Derivatives with a Bicyclic β-Lactam Structure from a Common 3-Azido-4-oxoazetidine-2-carbaldehyde Precursor

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posted on 2008-02-15, 00:00 authored by Benito Alcaide, Pedro Almendros, Amparo Luna, Teresa Martínez del Campo
Two different stereocontrolled accesses to new 4-hydroxypipecolic acid analogues with a bicyclic β-lactam structure have been developed by using intramolecular reductive amination or allenic hydroamination reactions in 2-azetidinone-tethered azides. The access to the cyclization precursors was achieved from 3-azido-4-oxoazetidine-2-carbaldehyde via metal-mediated carbonyl−allenylation in aqueous environment or by organocatalytic direct aldol reaction. The tin hydride-promoted cyclization of the 2-azetidinone-tethered azidoallene is totally regioselective for the central allenic carbon providing a fused piperidine.

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