Spectroscopic study on enantiomeric Ni(II) complexes of porphyrin-porphyrin Tröger's base and porphyrin-chlorin spiro-Tröger's base derivatives supported by DFT calculations.

The chiral properties of nickel(II) complexes of porphyrin-porphyrin Tröger's base and porphyrin-chlorin spiro-Tröger's base with phenyl or 3-methoxyphenyl substitutions in their meso-positions were studied. Enantioseparation of racemic mixtures was investigated via high-performance liquid chromatography (HPLC) on an analytical ReproSil Chiral-NR column. The optimal conditions were utilized for a multimilligram scale isolation with a semipreparative column. The purity of the isolated enantiomers was determined by HPLC and UV-Vis spectroscopy. The absolute configurations of the isolated enantiomers were determined by evaluating the Cotton effect in electronic circular dichroism spectra. The determination was supported by TDDFT calculations, in which good agreement was achieved between the experimental and simulated spectra. The maximum molar ellipticity values, [θ]λmax given in deg ∙ cm2 ∙ dmol-1, were [θ]435 = 1.73 ∙ 107 for phenyl spiroTB and [θ]436 = 1.24 ∙ 107 and [θ]436 = 2.15 ∙ 107 for 3-methoxyphenyl TB and spiroTB, respectively.

Preparations of spherical nanoparticles of chiral Cinchona alkaloid-based bridged silsesquioxanes and their use in heterogeneous catalysis of enantioselective reactions.

Two spherical nanoparticulate materials were prepared by base-catalyzed sol-gel hydrolysis/self-condensation of the bis-Cinchona alkaloid-phthalazine-based bridged bis(triethoxysilanes). For the purpose of comparing the catalytic properties, two compact materials were also prepared from the same precursors using a fluoride-catalyzed sol-gel process. All materials were characterized by SEM, TEM, solid-state 29Si NMR and 13C NMR, TGA, and FTIR. The prepared silsesquioxane-based materials were studied as potential heterogeneous catalysts for selected enantioselective reactions. The spherical material with regularly incorporated bis-quinine-phthalazine chiral units exhibited good to excellent enantioselectivities in osmium-catalyzed dihydroxylations of alkenes. Enantioselectivities observed in dihydroxylations of aromatic trans-alkenes were as excellent as those observed with the homogeneous catalyst (DHQ)2-PHAL. One compact and one nanoparticulate material was successfully recycled and reused five times without loss of enantioselectivity. Furthermore, both quinine-based and cinchonine-based materials were tested as heterogeneous organocatalysts for chlorolactonization of 4-arylpent-4-enoic acids. The materials showed only moderate enantioselectivities; however, these are the first heterogeneous catalysts for enantioselective chlorolactonization published so far.

Synthesis and absolute configuration of cyclic synthetic cathinones derived from α-tetralone.

The emergence of new synthetic cathinones continues to be a matter of public health concern. In fact, already known products (drugs) are being rapidly replaced by new structurally related alternatives, whereby modifications in the basic cathinone structure are used by manufacturers to circumvent the legislation. On the other hand, some derivatives of synthetic cathinones represent important pharmaceuticals with antidepressant properties. In the search for pharmaceutically relevant analogs, the main goal of the present study was to design and characterize novel cyclic α-tetralone-based derivatives of synthetic cathinones. We synthesized a series of derivatives and verified their chemical structure. Subsequently, chiral separation has been accomplished by high-performance liquid chromatography (HPLC) equipped with a circular dichroism (CD) detector, which directly provided CD spectra of the enantiomers of the analyzed substances at 252 nm. Using density functional theory calculations, we have obtained stable conformers of selected enantiomers in solution and their relative abundances, which we used to simulate their spectra. The experimental and calculated data have been used to assign the absolute configuration of six as-yet unknown synthetic cathinones.

Conformational analysis of amphetamine and methamphetamine: a comprehensive approach by vibrational and chiroptical spectroscopy.

After cannabis, the most commonly used illicit substance worldwide is amphetamine and its derivatives, such as methamphetamine, with an ever-increasing number of synthetic modifications. Thus, fast and reliable methods are needed to identify them according to their spectral patterns and structures. Here, we have investigated the use of molecular spectroscopy methods to describe the 3D structures of these substances in a solution that models the physiological environment. The substances were analyzed by Raman and infrared (IR) absorption spectroscopy and by chiroptical methods, vibrational circular dichroism (VCD) and Raman optical activity (ROA). The obtained experimental data were supported by three different computational approaches based on density functional theory (DFT) and molecular dynamics (MD). Successful interpretation relies on good agreement between experimental and predicted spectra. The determination of the conformer populations of the studied molecules was based on maximizing the similarity overlap of weighted conformer spectra by a global minimization algorithm. Very good agreement was obtained between the experimental spectra and optimized-population weighted spectra from MD, providing a detailed insight into the structure of the molecules and their interaction with the solvent. The relative population of three amphetamine and six methamphetamine conformers was determined and is consistent with a previous NMR study. However, this work shows that only a few isolated conformers are not sufficient for the successful interpretation of the spectra, but the entire conformational space needs to be sampled appropriately and explicit interaction with the solvent needs to be included.