Photoredox-Mediated Hydrogen Isotope Exchange Reactions of Amino-Acids, Peptides, and Peptide-Derived Drugs.

Hydrogen isotopically labelled compounds are essential diagnostic tools in drug research and development, as they provide vital information about the biological metabolism of drug candidates and their metabolites. Herein we report a photoredox-initiated hydrogen atom transfer (HAT) protocol which efficiently and selectively introduces deuterium or tritium at C(sp3 )-H bonds, utilizing heavy water (D2 O or T2 O) as the hydrogen isotope source, and a guanidine base. This protocol has been successfully applied to the incorporation of deuterium in several amino acids (lysine, glycine and proline) and small peptides. Finally, the method has been applied to tritium, because tritium-labelled peptides are essential for application in biological experiments, such as ligand-binding assays, or absorption, distribution, metabolism, and excretion (ADME) studies.

New Developments in Chiral Cooperative Ion Pairing Organocatalysis by Means of Ammonium Oxyanions and Fluorides: From Protonation to Deprotonation Reactions.

This personal account summarizes our contribution to the ion pairing organocatalysis mainly by use of chiral quaternary or tertiary ammonium fluorides, aryloxides and carboxylates. Starting from an experimental observation, we were able to develop several approaches for the enantioselective protonation of silyl enolates and enol esters giving rise to chiral carbonyl compounds bearing a stereogenic center at the α-position. Moving from protonation to deprotonation reactions, chiral ammonium ion pair catalysts were successfully applied to several asymmetric transformations such as an Henry reaction or a direct vinylogous aldol reaction to cite a few. An outlook of further possible developments in this field of research will also be discussed.

Ruthenium-catalyzed cross-dehydrogenative ortho-N-carbazolation of diarylamines: versatile access to unsymmetrical diamines.

The dehydrogenative C-N cross-coupling of unprotected, secondary anilines through ortho-N-carbazolation has been achieved using a Ru catalytic system with O2 as the terminal oxidant. The reactions proceed in an intermolecular fashion, selectively in the ortho position. Implications for the field of organic synthesis are discussed.