Synthesis of α,α-dialkyl-α-amino esters by α-alkylation of aldimines prepared from a novel pyridoxalmodelcompound was studied. The α-alkylation of the aldimines having an ethoxy-ethoxy group at C-3 proceeded most rapidly when LiOH was employed as a base and gave α,α-dialkyl-α-amino esters after acidic hydrolysis. The chelated structure composed of the aldimine and Li+ was also revealed by 1H-NMR analysis
Asymmetric α-Alkylation of α-Amino Esters Using Pyridoxal Derivatives Having a Chiral Ansa-Structure and a Chiral Ionophore Function: a Novel Example of Double Asymmetric Induction
Stereoselective alkylation of aldimines, prepared from α-aminoesters and a pyridoxalmodelhaving a chiral ansa-structure and an ethoxyethoxy group at C-3, proceeded in the presence of Li+ to give α,α-dialkyl amino esters after acidic hydrolysis. Double asymmetric induction effect was also observed in the alkylation reaction by combination of the chiral ansa-structure and a chiral ionophore side chain
Catalytic α-Allylation of Unprotected Amino Acid Esters
作者:Ping Fang、Mani Raj Chaulagain、Zachary D. Aron
DOI:10.1021/ol300665n
日期:2012.4.20
Catalytic alpha-allylation of unprotected amino acid esters to produce alpha-quaternary alpha-allyl amino acid esters is reported. Catalytic loadings of picolinaldehyde and Ni(II) salts induce preferential reactivity at the enolizable alpha-carbon of amino acid esters over the free nitrogen with electrophilic palladium pi-allyl complexes. Fourteen examples are given. Additionally, the use of chiral ligands to access enantioenriched alpha-quaternary amino acid esters from racemic precursors is demonstrated by the enantioselective synthesis of alpha-allyl phenylalanine methyl ester from racemic phenylalanine methyl ester.