SEARCH Articles Figures Tables Asymmetric epoxidation catalyzed by novel azacrown ether-type chiral quaternary ammonium salts under phase-transfer catalytic conditions Azacrown ether derivatives Azacrown ether-type quaternary ammonium Azacrown ethers and porphyrinogens Azacrown ethers, conformers Azacrown ethers, synthesis Azacrowns Chiral azacrown ether Synthesis of the azacrown ether Synthesis of the azacrown ether-type quaternary ammonium salt