Differentiation and identification of enantiomers by nuclear magnetic resonance spectroscopy with support of quantum mechanical computations

We report nuclear magnetic resonance studies of two chiral building blocks of solifenacin, phenyltetrahydroisoquinoline and quinuclidinol, in which chiral solvating agents, Mosher's acid, and Pirkle's alcohol were used for spectral discrimination between enantiomers of solifenacin constituents. Based on the constraints following from measurements of the nuclear Overhauser effect, structures of phenyltetrahydroisoquinoline and Pirkle's alcohol solvates were found. Next, shifts of nuclear magnetic resonance signals of phenyltetrahydroisoquinoline due to the application of Pirkle's alcohol were computed using density functional theory methods. The computed carbon-13 shifts reproduce those determined experimentally, allowing us to attribute the absolute configuration to phenyltetrahydroisoquinoline enantiomers without the need for the use of empirical rules.

Synthesis, dielectric properties, molecular docking and ADME studies of pyrrole-3-ones

A novel series of pyrrole-3-one derivatives were synthesized using furan-3-one derivatives and various aromatic amines. The synthesized compounds were identified by spectral studies such as IR, NMR and HRMS. Dielectric properties of the target compounds were experimentally determined by dielectric spectroscopy in the frequency range of 20 Hz - 1 MHz. The real part of the dielectric constant, dielectric loss tangent and conductivity of the samples were investigated as a function of applied frequency. Dielectric measurements showed Ata7 has the maximum dielectric constant at 1 kHz, while Ata1 has a negative dielectric constant value. When the result is evaluated with theoretical calculations, grain boundaries play an effective role in the experimental observed dielectric constant. Additionally, in this research the pyrrole-3-one derivatives (Ata1-9) were theoretically optimized and over these structures, NMR with GIAO (gauge-independent atomic orbital), UV with TD (time dependent), frontier orbitals (HOMO and LUMO), NLO (nonlinear optical properties) and MEP (molecular electrostatic potential) analysis were carried out. Quantum chemical computations were performed by Density Functional Theory (DFT) using B3LYP functional and 6-311++G (d,p) basis set. Later, the molecular docking analysis between Ata1-9 and two different receptors such as 3RZE and 3TDA was performed using AutoDock Vina program. Lastly, drug-likeness, physicochemical and ADME/T properties of the designed compounds were computed with the help of SwissADME online tool.Communicated by Ramaswamy H. Sarma.

London Dispersion and Hydrogen-Bonding Interactions in Bulky Molecules: The Case of Diadamantyl Ether Complexes

Diadamantyl ether (DAE, C20 H30 O) represents a good model to study the interplay between London dispersion and hydrogen-bond interactions. By using broadband rotational spectroscopy, an accurate experimental structure of the diadamantyl ether monomer is obtained and its aggregates with water and a variety of aliphatic alcohols of increasing size are analyzed. In the monomer, C-H⋅⋅⋅H-C London dispersion attractions between the two adamantyl subunits further stabilize its structure. Water and the alcohol partners bind to diadamantyl ether through hydrogen bonding and non-covalent Owater/alcohol ⋅⋅⋅H-CDAE and C-Halcohol ⋅⋅⋅H-CDAE interactions. Electrostatic contributions drive the stabilization of all the complexes, whereas London dispersion interactions become more pronounced with increasing size of the alcohol. Complexes with dominant dispersion contributions are significantly higher in energy and were not observed in the experiment. The results presented herein shed light on the first steps of microsolvation and aggregation of molecular complexes with London dispersion energy donor (DED) groups and the kind of interactions that control them.