Macrocycle

Potentiometric titrations and 1H NMR spectroscopic studies of amino acids binding to the [ZnL]2R-complex where
L¼cyclen in aqueous solution provide information concerning complexing species identity, their stability, and
coordination mode declaration. The amino acids form stable ternary [ZnL(HLn)]2R and [ZnL(Ln)]R complexes. The
observations indicate bidentate coordination mode of the deprotonated amino acids, involving both the amine and
the carboxylate functions to the [ZnL]2R complex in pH region of about 7.5–9.5. The determined stability constants
indicate that [ZnL]2R complex is a very efficient receptor for simple amino acids such as glycine and alanine.

Pillar[n]arenes are a new family of nanocapsules that have shown application in a number of areas, but because of their poor water solubility their biomedical applications are limited. Recently, a method of synthesizing water-soluble pillar[n]arenes was developed. In this study, carboxylated pillar[n]arenes (WP [n], n = 6 or 7) have been examined for their ability to form host-guest complexes with compounds relevant to drug delivery and biodiagnostic applications. Both pillar[n]arenes form host-guest complexes with memantine, chlorhexidine hydrochloride, and proflavine by 1H nuclear magnetic resonance and modeling. Binding is stabilized by hydrophobic effects within the cavities, and hydrogen bonding and electrostatic interactions at the portals. Encapsulation within WP[6] results in the complete and efficient quenching of proflavine fluorescence, giving rise to " on " and " off " states that have potential in bio-diagnostics. The toxicity of the pillar[n]arenes was examined using in vitro growth assays with the OVCAR-3 and HEK293 cell lines. The pillar[n]arenes are relatively nontoxic to cells except at high doses and after prolonged continuous exposure. Overall, the results show that there could be a potentially large range of medical applications for carboxylated pillar[n]arene nanocapsules.

A convergent total synthesis of amphidinolactone A, a cytotoxic macrolide from the cultured dinoflagellate Amphidinium sp., is described in 13 linear steps. The key step in the synthetic sequence involves an intramolecular Nozaki–Hiyama–Kishi (NHK) reaction for the construction of the 13-membered lactone ring by union of two fragments derived from a single chiral epoxide. The stereochemical outcome of the NHK reaction has been supported by computational studies.

The synthesis, characterization and structure are described for new cobalt complexes, with a BF2 bridged, bis(a-dioxime) ligand, based upon a sterically demanding framework derived from an anthracene Diels-Alder adduct. The ligand provides a deep cleft within which axial ligands and/or O2 can bind. The crystal structures of the bis- and mono(BF2 ) bridged complexes have space groups P21/c and PI,