Hideto Miyabe

Chiral environment specifically induced by metal ion: Asymmetric α-alkylation of α-amino esters using pyridoxal derivatives having a chiral ionophore function

Abstract Stereoselective alkylation of aldimines, prepared from α-amino esters and pyridoxal models having an ionophoric side-chain composed of a chiral glycerol structure, proceeded in the presence of Li+ or Na+ to afford α,α-dialkyl amino esters after acidic hydrolysis. Both the structure of the side chain and the metal ion were found to be in relation with the stereoselectivity, affording the highest stereoselectivity when the side-chain having a 2-naphthylmethoxy group and a methoxy group at the respective 3′- and 2′-positions was employed in the presence of Na+.

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

Abstract Stereoselective alkylation of aldimines, prepared from α-amino esters and a pyridoxal model having 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 at C-3.

α-alkylation of α-amino esters by using a pyridoxal model compound having a Li+-ionophore character

Abstract Synthesis of α,α-dialkyl-α-amino esters by α-alkylation of aldimines prepared from a novel pyridoxal model compound 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 1 H-NMR analysis.

Asymmetric α-alkylation of α-amino esters using pyridoxal model compounds with a chiral ionophore function; dependence of stereoselectivity on a chelated metal ion

Asymmetric α-alkylation of α-amino esters by use of novel pyridoxal model compounds having a chiral ionophore function is studied; the stereoselectivity is specifically induced by Na+ and the most effective asymmetric induction occurs with a combination of Na+ and an additional chiral ansa-structure.

Novel indole-ring formation by thermolysis of 2-(N-acylamino)-benzylphosphonium salts. Effective synthesis of 2-trifluoromethylindoles

Thermolysis of 2-(N-acylamino)benzyl methyl ethers, in the presence of an acid catalyst and triphenylphosphine, or 2-(N-acylamino)benzylphosphonium salts is found to serve as a novel method for indole formation, in particular for the synthesis of 2-trifluoromethylindoles. The reaction of the benzyl methyl ethers is suggested to involve a phosphonium intermediate, which thermally decomposes to the indoles.