Enantioselective synthesis of tunable chiral pyridine–aminophosphine ligands and their applications in asymmetric hydrogenation

A small library of tunable chiral pyridine–aminophosphine ligands were synthesized based on tetrahydroquinoline scaffolds obtained via Ru-catalyzed asymmetric hydrogenation. The ligands were applied in the Ir-catalyzed asymmetric hydrogenation of olefins and imines.

An integral study of cyclodextrins as solubility enhancers of α-methylstilbene, a resveratrol analogue

trans-α-Methylstilbene (tMS), a resveratrol analogue, has recently been studied in a search for new bioactivities. However, such studies do not take into account that the poor solubility of tMS in aqueous solutions could affect its bioactivity. For this reason, we propose, for the first time, using cyclodextrins (CDs) as solubilizers to increase tMS solubility, in aqueous solutions. The HPLC-RP results obtained, point to a 1 : 1 stoichiometry for all the natural (α-, β- and γ-CD) and modified (HPβCD and MβCD) CDs tested. The K_Fapp (apparent formation constant) for the tMS-CD complexes was seen to be closely dependent on several factors, including the temperature and type of CD. Indeed, the highest K_Fapp value was obtained for MβCD, while the K_Fapp decreased with increasing temperature. In addition, the results showed negative entropy (-8.86 × 10^-3 ± 0.40 kJ mol^-1 K^-1) and enthalpy (-16.70 ± 0.98 kJ mol^-1) changes and a negative Gibbs free energy value at 25 °C (-14.00 ± 0.55 kJ mol^-1) for the encapsulation process. A computational study carried out using molecular docking calculations showed a high degree of correlation between the computed scores and experimental values. Finally, the complexation of trans-stilbene and pinosylvin with HPβCD was compared with tMS.