SYNTHESIS OF ENANTIOMERICALLY ENRICHED α-AMINOPHOSPHINIC ACID DERIVATIVES VIA ASYMMETRIC HYDROGENATION

Stereoselective Synthesis of α-Amino-C-phosphinic Acids and Derivatives

α-Amino-C-phosphinic acids and derivatives are an important group of compounds of synthetic and medicinal interest and particular attention has been dedicated to their stereoselective synthesis in recent years. Among these, phosphinic pseudopeptides have acquired pharmacological importance in influencing physiologic and pathologic processes, primarily acting as inhibitors for proteolytic enzymes where molecular stereochemistry has proven to be critical. This review summarizes the latest developments in the asymmetric synthesis of acyclic and phosphacyclic α-amino-C-phosphinic acids and derivatives, following in the first case an order according to the strategy used, whereas for cyclic compounds the nitrogen embedding in the heterocyclic core is considered. In addition selected examples of pharmacological implications of title compounds are also disclosed.

Reactions in Micellar Systems

The notion of "green chemistry" has encouraged even synthetic organic chemists to include water as a solvent. Incredible selectivities and activities can be achieved through the addition of amphiphiles with a defined structure. The morphology of supramolecular assemblies or associates formed by surfactants vary according to the temperature and concentration. As a rule, reactions are typically conducted using simple spherical aggregates, that is, micelles in the nanometer range. The strong polarity gradient present between the hydrophilic surface and the hydrophobic core of the micelle means that both nonpolar and polar reagents can be solubilized. This solubilization results in reactants becoming more concentrated within the micelle than in the surrounding water phase and leads to an acceleration of the reaction and causes selective effects. The kinetic treatment of reactions in micellar systems can be accomplished by considering them as microheterogeneous two-phase systems.