Dmitry V. Zakharychev

Three different types of chirality-driven crystallization within the series of uniformly substituted phenyl glycerol ethers.

Seven chiral arylglycerol ethers 2-R-C(6)H(4)-O-CH(2)CH(OH)CH(2)OH (R = H, Me, Et, Allyl, n-Pr, i-Pr, tert-Bu) were synthesized in racemic and scalemic form. The IR spectra, melting points, and enthalpies of fusion for racemic and scalemic samples of every species were measured, the entropies of enantiomers mixing in the liquid state and Gibbs free energies of a racemic compound formation were derived and binary phase diagrams were reconstructed for the whole family. Solid racemic compounds stabilities were ranked for the four substances. Spontaneous resolution was established for the registered chiral drug mephenesin and its ethyl analogue. Metastable anomalous conglomerate, forming crystals having three independent R* and one independent S* molecules in the unit cell, is formed during solution crystallization of tert-butyl derivative; metastable phase transforms slowly into traditional racemic conglomerate.

Chiral drug timolol maleate as a continuous solid solution: Thermochemical and single crystal X-ray evidence

Thermochemical properties of binary mixtures of the popular chiral drug timolol maleate (TM) were investigated by differential scanning calorimetry. It was found that there are no eutectic points on the melting phase diagram, and the enantiomeric components form a continual set of solid solutions over a wide concentration range. The crystal structure of heterochiral racemic TM is essentially isostructural with that of the homochiral (S)-TM, having close cell parameters but containing a crystallographic inversion centre. The crystal structure of the homochiral TM contains two symmetry independent molecules in the unit cell. These molecules have different conformations but are approximate mirror images of each other in the crystal lattice. Within the homochiral crystals only one site of two changes its nature in the heterochiral crystals. The solid solution of TM could be treated as the solid solution of a regular racemic compound and a pure enantiomer.

Crystal structure and phase behavior of the tolyl glycerol ethers. From the conglomerate former to the chirality-driven nanogelator

According to differential scanning calorimetry data ortho-, meta-, and para-tolyl glycerol ethers 1–3 form thermodynamically most stable crystal phases during solution crystallization. For all members of the series the crystal phases formed during melt crystallization have different thermodynamic characteristics from those of the stable ones. Binary melting diagrams were constructed for the stable solid phases; on this basis it was found that 1 is prone to spontaneous resolution, and 2 and 3 form stable solid racemic compounds, the Gibbs energy of formation for which are found to be −2.70 and −2.43 kJ mol−1. Solution grown single crystals of 1–3 were investigated by an X-ray diffraction method. The principal supramolecular crystal formative motifs were revealed: 1D columns for 1 and scal-2, 2D bilayers having developed a 2D system of intermolecular hydrogen bonds (IMHB) for rac-2 and rac-3, and 2D bilayer having 1D spiral IMHB organization for scal-3. The possible reasons preventing the solid racemic compound formation in the case of 1, and the spontaneous resolution manifestation in the cases of 2 and 3 are disclosed. It was demonstrated that, from the whole family of tolyl glycerol ethers, only scal-3 samples are capable of supramolecular gels formation. This property is connected with the peculiarities of the scalemic 3 crystal packing.

Synthesis and some features of phase behavior of chiral p-alkoxyphenyl glycerol ethers

A series of (S)-3-(4-alkoxyphenoxy)propane-1,2-diols was prepared with the enantiomeric excess 86–92% by Sharpless asymmetric dihydroxylation of 1-alkoxy-4-allyloxybenzenes with an AD-mix-β mixture. R-Enantiomers with enantiomeric excess 97–99% and racemic samples were obtained by reaction of sodium p-substituted phenolates with (R)- and rac-3-chloropropane-1,2-diol. The phase behavior of racemates and scalemates in the produced homolog series of glycerol aryl ethers with hydrocarbon substituents of various length was examined by means of thermomicroscopy. The higher memberes of the homolog series of both racemic and scalemic diols undergo at heating an enantiotropic phase transition to a smectic liquid crystal phase.