Immobilised Zinc (II) Cyclen complexes as catalytic reagents for phosphodiester hydrolysis

Many hydrolases found in nature have Zn(II) ions at their active site. Artificial hydrolases as alternatives for non-enzymatic hydrolysis were prepared by attaching Zn(II) cyclen complexes with an alcohol pendant to a polymeric support. These modified polymers showed a 104-fold enhanced intrinsic reactivity for the hydrolysis of activated phosphodiesters over the non-catalysed reaction in solution

Electronic Effects on the Bergman Cyclisation of Enediynes. A Review

The thermal cyclisation of enediynes to benzene-1,4-diyl diradicals (Bergman cyclisations) is affected by geometrical and electronic conditions. While the effect of ring strain or conformational constrains on the cyclisation temperature has been investigated in detail, electronic contributions have been less studied. Often geometrical and electronic contributions cannot be clearly distinguished. In most cases metal ion chelation does involve both. We have summarised clear-cut observations of electronic substituents effects on the thermal enediyne reactivity

Chromone derivatives which bind to human hair

Chromone derivatives bearing a quaternary ammonium functionality which bind to human hair were synthesised. The radical scavenging activity, according to the DPPH assay, of the chromone derivatives is considerably lower compared with flavonoids. The compounds show interesting UV absorption properties that depend on the position of a methoxy substituent. A bathochromic shift of 29 nm was observed when the methoxy group on the ammonium salts were shifted from position 7 to position 6

Vesicles and Micelles from Amphiphilic Zinc(II)−Cyclen Complexes as Highly Potent Promoters of Hydrolytic DNA Cleavage

Phosphate esters are essential to any living organism and their specific hydrolysis plays an important role in many metabolic processes. As phosphodiester bonds can be extraordinary stable, as in DNA, great effort has been put into mimicking the active sites of hydrolytic enzymes which can easily cleave these linkages and were often found to contain one or more coordinated metal ions. With this in mind, we report micellar and vesicular Zn(II)–cyclen complexes which considerably promote the hydrolytic cleavage of native DNA and the activated model substrate bis(4-nitrophenyl)phosphate (BNPP). They are formed by self-assembly from amphiphilic derivatives of previously employed complexes in aqueous solution and therefore allow a simple and rapid connection of multiple active metal sites without great synthetic effort. Considering the hydrolytic cleavage of BNPP at 25 °C and pH 8, the micellar and vesicular metal catalysts show an increase of second-order rate constants (k2) by 4–7 orders of magnitude compared to the unimolecular complexes under identical conditions. At neutral pH, they produce the highest k2 values reported so far. For pBR322 plasmid DNA, both a conversion of the supercoiled to the relaxed and linear form, and also a further degradation into smaller fragments by double strand cleavages could be observed after incubation with the vesicular Zn(II)–complexes. Finally, even the cleavage of nonactivated single-stranded oligonucleotides could be considerably promoted compared to background reaction

Chromone: A valid scaffold in medicinal chemistry

Chromones are a group of naturally occurring compounds that are ubiquitous in nature, especially in plants. The word chromone is derived from the Greek word chroma, meaning “color”, which point out that many chromone derivatives can exhibit a diversity of colors.This work was supported by the Foundation for Science and Technology (FCT), Portugal (projects PTDC/QUI-QUI/113687/2009 and PEst-C/QUI/UI0081/2013). A.G. (SFRH/BD/43531/2008) and M.J.M. (SFRH/BD/61262/2009) thank FCT for grants