2-Methoxyethyl Nitrite as a Reagent for Chemoselective On-Water Nitration

An on-water approach has been developed that allows a nitration of tyrosines and phenols under mild conditions. We envisioned that the assembly of tyrosine/tyrosyl radical couples with interfacial water molecules would realize a biomimetic stacking hydrogen atom transfer (HAT) transition state to facilitate the electron-transfer process. The optimal organic nitrite, 2-methoxyethyl nitrite, resulted in rapid coupling of the tyrosyl radicals with •NO 2 at the oil-water interface to afford the nitrated phenols. Many characteristics found in our on-water strategy are distinct from other complementary systems that include radical nitration. These enticing roles of water in the reaction process introduce new avenues to explore in the design of synthetic organic chemistry systems.

Calixarenes Incorporating Sulfonamide Moieties: Versatile Ligands for Carbonic Anhydrases Inhibition

Carbonic anhydrases (CAs) continue to represent a relevant pharmaceutical target. The need of selective inhibitors and the involvement of these metalloenzymes in many multifaceted diseases boost the search for new ligands able to distinguish among the different CA isoforms, and for multifunctional systems simultaneously able to inhibit CAs and to interfere with other pathological events by interacting with additional targets. In this work, we successfully explored the possibility of preparing new CAs ligands by combining calixarenes with benzensulfonamide units. Inhibition tests towards three human CA isoforms evidenced, for some of the ligands, K_i values in the nanomolar range and promising selectivity. X-ray and molecular modeling studies provided information on the mode of binding of these calixarene derivatives. Thanks to the encouraging results and the structural features typical of the calixarene scaffold, it is then possible to plan for the future the design of multifunctional inhibitors for this class of widely spread enzymes.