Application of a supramolecular-ligand library for the automated search for catalysts for the asymmetric hydrogenation of industrially relevant substrates.

A procedure is described for the automated screening and lead optimization of a supramolecular-ligand library for the rhodium-catalyzed asymmetric hydrogenation of five challenging substrates relevant to industry. Each catalyst is (self-) assembled from two urea-functionalized ligands and a transition-metal center through hydrogen-bonding interactions. The modular ligand structure consists of three distinctive fragments: the urea binding motif, the spacer, and the ligand backbone, which carries the phosphorus donor atom.

2,N6-disubstituted adenosine analogs with antitrypanosomal and antimalarial activities.

A library of 2,N(6)-disubstituted adenosine analogs was synthesized and the analogs were tested for their antiprotozoal activities. It was found that 2-methoxy and 2-histamino and N(6)-m-iodobenzyl substitutions generally produced analogs with low levels of antiprotozoal activity. The best antiplasmodial activity was achieved with large aromatic substitutions, such as N(6)-2,2-diphenylethyl and naphthylmethyl, which could indicate a mechanism of action through aromatic stacking with heme in the digestive vacuole of Plasmodium spp.

UREAphos: supramolecular bidentate ligands for asymmetric hydrogenation.

Supramolecular bidentate phosphite ligands are presented as a new class of ligands for rhodium catalysed asymmetric hydrogenation.

The mechanism of selective purine C-nitration revealed: NMR studies demonstrate formation and radical rearrangement of an N7-nitramine intermediate.

Modified purine derivatives are of great importance in biomedical sciences, and substitution reactions on the purine skeleton are intensively studied. In our laboratory, an efficient and selective purine C2-nitration reaction was developed using a mixture of tetrabutylammonium nitrate and trifluoroacetic anhydride. The resulting 2-nitro moiety appeared to be a versatile handle to introduce a variety of pharmacophores onto the purine skeleton.