Hiroshi Tsukube

Double armed crown ethers and armed macrocycles as a new series of metal-selective reagents: A review

Various double armed crown ethers and related macrocycles are presented as metal-selective reagents characterized by macrocyclic ligands and metal-ligating sidearms. They exhibit unique metal binding and recognition functions via macroring-sidearm cooperative action. Since they form three dimensional complexes suitable for metal-sensing and separation, we can develop a new series of metal-selective reagents via armed macrocycle strategy. Polymerization and immobilization of the armed macrocycles further enhance the usefulness in analytical science. This review focuses primarily on the molecular design, host-guest chemistry, and analytical applications of the armed macrocycles, and clearly indicates that these macrocycles provide new options in designing a metal-selective reagent.

Enhanced reaction rate and enantioselectivity in lipase-catalyzed hydrolysis by addition of a crown ether

Abstract Both reaction rate and enantioselectivity in a lipase-catalyzed hydrolysis of β-acetoxybutyronitrile were significantly enhanced by addition of hydroxymethyl-12-crown-4.

Biomimetic Membrane Transport via Designed Macrocyclic Host Molecules

Abstract Biomimetic approaches to naturally occurring ion transport were discussed. Selective transport systems of alkali, alkaline earth, heavy, and transition metal cations as well as organic cations and anions were successfully constructed by using “synthetic” ionophores. They were designed by considering (i) sizes of their molecular cavities for guest-binding; (ii) natures of their binding sites; and (iii) their three-dimensional ligand topologies. Their synthetic strategies, guest-binding and transport abilities, and biological significance were mainly described.

Triazamacrocycle having pyridine-pendant arms as a new Na+ ion-selective ionophore

Abstract A new type of azamacrocycles having pyridine-pendant arms mediated highly selective and efficient transport of Na + ion via three-dimensional complexation, which was not attained by common azamacrocycle, crown, and hemispherand compounds.

Armed crown ether complexes in supramolecular assembly

Abstract Recent advances in macrocyclic chemistry and its applications to supramolecular chemistry are described. We first present concept and examples of “armed crown ethers”, which are characterised by a parent crown ether ring and a functionalised sidearm. Their structural variations extend molecular recognition and add new reactivity to the parent crown ether. As a new synthetic approach, the computer-aided design of Li + ion-specific armed crown ethers is discussed. The rational design and refined synthesis can offer specific molecular recognition and integrated functions. We also address two interesting approaches developed in the border regions between macrocyclic chemistry and supramolecular chemistry. Armed crown ethers form unique supramolecular assemblies with membranes and biopolymers. These modify the original functionalities of both the armed crown ether and the membrane-biopolymer and further exhibit supramolecular functions. Combinations of armed crown ether chemistry with computer chemistry, membrane chemistry and biopolymer chemistry provide interesting possibilities in creating new functional supramolecular assemblies.

Highly selective transport of biogenetic amines and drugs by using functionalized “acyclic crown ether”

Abstract Acyclic crown ether 1 , containing quinoline terminal groups, showed effective transport selectivity for some kinds of biogenetic amines and drugs of biological significances over alkali metal cations, which was not attained by using a typical cyclic crown ether 3 .

K+ ion - dependent, active transport of amino acid anions by macrocyclic carriers

Abstract Active and selective transport of amino acid anions was successfully mediated by macrocyclic carriers, coupled with K+ ion transport.

Ipso substitution of 2-alkylsulfinylpyridine by 2-pyridyllithium; a new preparation of oligopyridine and their bromomethyl derivatives

Abstract Unsymmetrical and symmetrical 2,2′-bipyridines 5 and 6 have been prepared. The methods applied are new and offer efficient syntheses of higher oligopyridines and their bromomethyl derivatives.

“Armed thia-crown ether”: a specific carrier for soft metal cation

Abstract Macrocyclic polythiaether having two ligating “arms” for soft metal cations showed new and specific transport ability for Ag + ion, based on cooperative actions of parent thia-crown ring and side arms.

Enantiomer recognition of organic ammonium salts by podand- and crown-type monensin amides ; new synthetic strategy for chiral receptors

Abstract Podand- and crown-types of new chiral receptors, characterized by a chiral polyether skeleton and an amide junction, were derived from naturally occurring monensin ionophore. Their chiral recognition ability was investigated by ion-selective electrode and 1H-NMR spectroscopic methods. Several podand-type monensin amides formed 1:1 complexes with chiral amine salts and exhibited excellent enantiomer selectivity. Since biological monensin and its macrocyclic derivatives were less effective for chiral recognition, a molecular combination of pseudo-cyclic monensin cavity, chiral polyether skeleton and neutral amide moiety offered high enantiomer selectivity. Chemical modification of biological monensin allowed remarkable development of new ionophoric-functions and provided an effective synthetic strategy for chiral receptors.