Ureas, carbamoyl derivatives, amides, and sulfonamides can be easily prepared from the strained (R,R)-cylohexanediamine urea (1) in high yield, leaving a free amino group that shows good catalytic activity in intramolecular aldol condensations. The preparation of Wieland-Miescher ketone has been studied with these catalysts.
Carbazole-based receptors functionalized with two sulfonamide groups have been synthesized and their properties as anion receptors have been evaluated. The receptor with bis(trifluoromethyl)aniline groups has shown a very high affinity for halide ions, especially remarkable as only two hydrogen bonds are formed in the complexes. (1)H NMR and fluorescence titrations have been carried out and binding constants up to 7.9 × 10(6) M(-1) have been reached. X-ray structures have been obtained and a modelling study has shown the possible reasons for the large affinity of these compounds for halide anions.
Enzymes are the most
efficient and specific catalysts to date.
Although they have been thoroughly studied for years, building a true
enzyme mimic remains a challenging and necessary task. Here, we show
how a three-dimensional geometry analysis of the key catalytic residues
in natural hydrolases has been exploited to design and synthesize
small-molecule artificial enzymes which mimic the active centers of
chymotrypsin and N-terminal hydrolases. The optimized prototype catalyzes
the methanolysis of the acyl enzyme mimic with a half-life of only
3.7 min at 20 °C, and it is also able to perform the transesterification
of vinyl acetate at room temperature. DFT studies and X-ray diffraction
analysis of the catalyst bound to a transition state analogue proves
the similarity with the geometry of natural hydrolases.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.