A synthetic receptor for phosphocholine esters.
A bifunctional Zn-salen modified cavitand, reminiscent of the enzyme phospholipase C, shows high efficiency and synergic effect in the binding of the phospholipid DOPC.
Binding Sites↗
Biomedical subjects
Julius Rebek
Publications and source records attributed to Julius Rebek.
Cavitand templated catalysis of acetylcholine.
A Zn-salen-modified cavitand templates the catalytic formation of acetylcholine from choline and acetic anhydride.
Acetic Anhydrides↗
Normal hydrocarbons tumble rapidly in a deep, water-soluble cavitand.
A deep, water-soluble cavitand extracts n-alkanes and other water-insoluble species into its cavity via hydrophobic forces: alkanes bind in a helical manner, and tumble rapidly on the NMR timescale inside the binding pocket.
Alkanes↗
Binding properties of cavitands in aqueous solution--the influence of charge on guest selectivity.
The charge of the upper rim has influences on the binding properties of cavitands in aqueous media.
Ethers, Cyclic↗
Metal directed assembly of ditopic containers and their complexes with alkylammonium salts.
A new self-folding cavitand has been assembled through metal coordination to give a thermodynamically stable ditopic receptor of nanosize dimensions which has been used in the reversible binding of di-alkylammonium and n-alkylammonium salts.
Alkylation↗
Deep cavitands provide organized solvation of reactions.
Deep self-folding cavitands have been shown to stabilize the charged enolate intermediate of the alpha-deuteration of activated olefins by means of a network of organized solvation.
Acrylates↗
Fluorescence resonance energy transfer across a mechanical bond of a rotaxane.
Fluorescence transfer across a donor-acceptor tagged rotaxane was studied and a small conformational change of the rotaxane observed using fluorescent spectroscopy and ROESY NMR.
Fluorescence Resonance Energy Transfer↗
A deep cavitand provides a structured environment for the Menschutkin reaction.
We report that a synthetic, vase-shaped host molecule forms complexes with quinuclidine and accelerates the Menschutkin reaction in the nanoenvironment that the host provides. Kinetic simulation is used to determine rate constants for reactions of the complex, and these are compared to control reactions in the absence of the host. The efficacy of the host in effecting this supramolecular acceleration is dependent on the structures of the alkylating agent and its leaving group.
Journal Article↗
Lower rim mono-functionalization of resorcinarenes.
A versatile, scaleable, one step synthesis of a lower rim mono-functionalized resorcinarene is described.
Calixarenes↗
Functional cavitands: chemical reactivity in structured environments.
Container-shaped molecules provide structured environments that impart geometric bounds on the motions and conformations of smaller molecular occupants. Moreover, they provide "solvation" that is constrained in time and space. When inwardly directed functional groups are present, they can interact chemically with the occupants. Additionally, the potential for reactivity and catalysis is greatly enhanced. Deep cavitands, derived from resorcinarenes, nearly surround smaller molecules and have been one of the most successful platforms for elaboration with functional groups. Derivatives bearing organic and metal-binding functional groups have been shown to affect recognition properties and selectively accelerate diverse reactions. In this review, we examine recent examples of these systems with an emphasis on how and why ordered nanoenvironments impart changes in the properties and reactivity of their occupants.
Binding Sites↗
Diastereoselection of chiral acids in a cylindrical capsule.
The cylindrical dimeric capsule binds two chiral carboxylic acids with modest selectivity for homochiral or heterochiral pairs.
Acids↗
Simultaneous encapsulation: molecules held at close range.
Reversible encapsulation creates spaces where molecules are temporarily isolated from others in solution. Molecules are held within the space of the capsule for lifetimes ranging from milliseconds to hours, and conventional NMR spectroscopy can be used to report on the chemical and magnetic environment as well as the arrangement of the molecules in the encapsulation complex. The complexes self-assemble when, and only when, the spaces inside the capsules are appropriately filled. The weak intermolecular forces that hold these self-assemblies together allow equilibration of the encapsulation complexes at ambient temperatures and pressures in the liquid phase. When two or more molecules are simultaneously encapsulated, intermolecular phenomena are revealed in solution that cannot be observed by other methods. We describe here the unique behavior that emerges from molecules that are simultaneously encapsulated and includes new forms of stereochemistry, isomerism, and asymmetry inside capsules.
Hydrogen Bonding↗
Hydrocarbon binding inside a hexameric pyrogallol[4]arene capsule.
Pyrogallol[4]arene forms discrete hexameric capsules in neat normal, branched, and cyclic alkanes. These hydrocarbon guests fill the available space and show chemical exchange that is slow on the NMR time scale. [reaction: see text]
Calixarenes↗
Resorcinarene assemblies as synthetic receptors.
The host-guest complexes of resorcinarenes are re-examined in solution through modern spectroscopic methods; the assemblies are characterized by 1H NMR and the guest exchange rates are measured by EXSY NMR spectroscopy.
Calixarenes↗
Catalysis by a synthetic receptor sealed at one end and functionalized at the other.
A deep cavitand bearing a zinc (II) salen wall catalyzes the hydrolysis of para-nitrophenylcholine carbonate. The closed end of the cavitand properly positions the carbonyl function of the substrate for activation by the metal center. Substrate specificity for acetylcholine derivatives results from simultaneous cation-pi interactions and a C=O- - -Zn coordination bond.
Carbonates↗
Encapsulation of oligoethylene glycols and perfluoro-n-alkanes in a cylindrical host molecule.
Oligoethylene glycols and perfluoro-n-alkanes are suitable guests for the synthetic cylindrical host molecule 1(2); an investigation of these host-guest systems is reported.
Alkanes↗
Synthesis of galmic: a nonpeptide galanin receptor agonist.
Galanin is a neuropeptide with a wide variety of biological functions. Few nonpeptide ligands, capable of activating galanin receptors, are available today. Based on known pharmacophores of galanin and the tripeptidomimetic galnon, a combinatorial library was formulated, synthesized, and screened against the galanin receptor. An active compound, galmic, was identified and tested in vitro and in vivo for its affinity and efficacy at galanin receptors. The present work describes the total synthesis of galmic, the synthesis of its oxazole precursors, the coupling of the building blocks into a linear trimer, and the macrolactamization reaction.
Magnetic Resonance Spectroscopy↗
Hydrogen-bonded encapsulation complexes in protic solvents.
We describe here the behavior of the hydrogen-bonded capsule 1.1 and its complexes in protic solvents. The kinetics and thermodynamics of the encapsulation process were determined through conventional (1)H NMR methods. The enthalpies and entropies of encapsulation are both positive, indicating a process that liberates solvent molecules. The rates of dissociation-association of the capsule were comparable to the rates for the in-out exchange of large guests, which suggests that guest exchange occurs by complete dissociation of the capsule in protic solvents. The stability of the hydrogen-bonded capsule 1.1 toward protic solvents depends strongly on the guests, with the best guest being dimethylstilbene 8. The results establish guidelines for the properties of capsules that could be accessed in water.
Benzene Derivatives↗