Synthesis, spectroscopic characterization and in vitro antitumor activity of new trans 1-heteroaryl-2-(1-methylpyridinium-2-yl) ethylenes

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REVERSIBLE MUTAROTATION IN A MACROCYCLIC YTTERBIUM COMPLEX

M40 is a four-fold symmetry macrocyclic ligand endowed with axial and central chiral elements, all of R configuration. It promptly binds late lanthanides (Yb III and Lu III) yielding a negative helicity, as witnessed by NIR-electronic circular dichroism. In the course of a few hours, a new conformation of the complex takes over, which has opposite helicity and allows for a dynamic free-bound equilibrium. Upon slow solvent evaporation, the original conformation is retrieved and the whole dynamic process can be started again, as in a sandclock, allowing one to envisage applications as a time-marker chiral switch. Helices are a-changing: In a macrocyclic complex of late lanthanides, a slow ligand conformational rearrangement in solution leads to helicity inversion that can be reverted by slow solvent evaporation and provides a circular dichroism time-marker (see graphic)

Second generation of calix[6]aza-Cryptands: synthesis of heteroditopic receptors for organic ion pairs.

The efficient syntheses of calix[6]azacryptands decorated with anion-binding groups on the narrow rim have been achieved from an 1,3,5-tris-protected calix[6]hexa-amine. These heteroditopic receptors can bind ammonium ions or organic ion pair salts with a positive cooperativity. In regard to their functionalization at the 1,3,5-phenolic positions, these compounds constitute the first examples of a second generation of C3 v symmetrical calix[6]azacryptands.Journal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Fluorous dienophiles are powerful diene scavengers in diels-alder reactions

(Matrix presented) Three fluorous dienophiles have been synthesized, and their value in scavenging an excess diene after Diels-Alder reactions is shown. The resulting fluorous derivatives are separated by solid-phase extraction on fluorous silica gel (FSPE). The fluorous [1,2,4]triazoline-3,5-dione 10 reacted with most dienes within seconds or minutes