Synthesis of Novel Enantiopure
4-Hydroxypipecolic Acid Derivatives with a
Bicyclic β-Lactam Structure from a Common
3-Azido-4-oxoazetidine-2-carbaldehyde Precursor
posted on 2008-02-15, 00:00authored byBenito 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.