1,721,234 research outputs found
Calixarenes and cations: a time-lapse photography of the big-bang
No full textThe outstanding cation complexation properties emerging from the pioneering studies on calixarene
ligands during a five-year period in the early 1980s triggered a big-bang burst of publications on such
macrocycles that is still lasting at a distance of more than 30 years. A time-lapse photography of this
timeframe is proposed which allows the readers to pinpoint the contributions of the different research
groups
Calixarene in Spherical Metal Ion Recognition
No full textThe development of new synthetic methods for the monoalkylation of calix[4]arenes at the lower rim allows the synthesis of a new class of trihydroxamate siderophores. Three chelating hydroxamic acid units are introduced through a sequence of reactions which blocks the macrocycle in the cone conformation. The new ligands obtained form neutral 1 :1 complexes (FeL) with iron (III), which are stable in EtOH/H,O 9: 1 at pH 2-7. Calix[4]arene his-crown ethers are prepared by exploiting the selective 1,2-(proximal) functionalization of calix[4]arenes at the lower rim. These ligands are, however, less
effective in complexing alkali metal cations compared with the
1J-calix [4] arene crown-ethers which, in their partial cone structure, offer a better shielding for the complexed cations. Rigid upper rim-bridged calix [4] arenes potentially useful for the inclusion of neutral molecules are prepared by exploiting the selective 1,3-diformylation of calixC4larene at the upper rim. Finally a new chloromethylation method for calix 141 arenes blocked in the coneconformation is described together with thesynthesis of new cavitands
Calix[4]arenes with Perfluorinated Alcoholic Functions at the Upper Rim. A New Class of Neutral Anion Receptors
No full textTwo or four perfluorinated alcoholic functions were successfully introduced at the upper rim of calix[4]arenes, affording a new type of neutral receptor for anion recognition; preliminary binding studies indicate that the difunctionalized receptors 3a and 3b are selective for Y-shaped carboxylate ions over spherical anions which are, on the contrary, more efficiently bound by the tetraalcohol 6
Biomimetic Macrocyclic Receptors for Carboxylate Anion Recognition
No full textCarboxylate anions are ubiquitous in nature and are
involved in several biological processes. For example,
the carboxylate group of the D-alanyl-D-alanine terminal
part of the cell wall peptidoglycan is selectively recognized
by the binding pocket of vancomycin-type antibiotics,[1]
di- and tricarboxylates are involved in several metabolic
processes,[2] and other carboxylate anions are known to be
substrates or inhibitors of enzymes.[3] Moreover, chiral propionic
acid derivatives are widely used in therapy as nonsteroidal
anti-inflammatory drugs[4] and carboxylate polyanions
can form well-ordered self-assembled structures
when mixed with complementary polycations or hydrogen
bonding donor groups.[5] For all these reasons the synthesis
of biomimetic receptors for carboxylate anions have been
recently pursued in supramolecular chemistry,[6–8] with
the aim of obtaining 1) useful models of the biological
processes, 2) biologically active molecules, 3) selective
chemosensors, and 4) selective separation systems.
The objective of this article is to highlight the most
successful approaches followed in the design and synthesis
of biomimetic receptors for carboxylate anion recognition,
with major emphasis on the results achieved in
the last 5 years with macrocyclic compounds, and on our
own work
Special issue of Supramolecular Chemistry honouring Professor Rocco Ungaro
No full textIt is really a great pleasure and a privilege for us to
introduce this special issue of Supramolecular Chemistry,
which is dedicated to our esteemed mentor, Prof. Rocco
Ungaro, on the occasion of his 70th birthday
Multivalent Glycocalixarenes
No full textWe herein briefly introduce the potentials of glycocalixarene as multivalent ligands. Their ability to inhibit specific proteins or to stimulate the immuno response, in fact, discloses the important role they might play in bionanotechnology and in nanomedicine. Nella presente rassegna vengono brevemente presentate le potenzialità dei glicocalixareni come leganti multivalenti. La loro capacità di inibire specifiche proteine o stimolare la risposta immunitaria mette in luce l’importante ruolo che questi leganti possono avere nel campo delle bionanotecnologie e della nanomedicina
Solid state interaction of steroids with calixarenes. I. A preliminary FTIR and DSC study on 4-en-3-keto-steroids
No full textBoth DSC and FTIR studies indicate that co-grinding and co-precipitation cause steroids to interact with calixarenes. This interaction leads to breaking of the crystal lattice of the steroids, dispersion of the steroidal carbonyls in a hydrophobic environment and formation of hydrogen bonds between steroidal and calixarene hydroxyls. This interaction seems to be specific, depending on the structure of the calixarene and of the steroid involved. It is reasonable to assume that inclusion complexes are formed
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