We present several multicomponent crystalline species formed by zwitterionic GABA analogues Pregabalin and Phenibut. These compounds are evaluated based on their crystal structure in congruence with properties such as melting...

Crystallization and multicomponent crystal formation of active pharmaceutical ingredients Baclofen and Phenibut with dicarboxylic acid co-formers are discussed. The crystallization process of several crystalline entities is elucidated via single crystal—as well as powder X-ray—diffraction, followed by thermal analysis and phase stability studies over time. Both APIs form increasingly complex crystalline phases with co-formers malic and tartaric acid, where phase purity of a desired compound is not necessarily a given. Therefore, the influence of different solution and milling environments during crystallization on the outcome is studied. Emphasis is laid on how molecular influences such as the chirality, propensity to form hydrates as well as low solubility of Baclofen and Phenibut impede attempts to gather high-quality single crystals. The results highlight that targeted crystallization of these compounds with dicarboxylic acids can be difficult and unreliable.

Halogen bonding of neutral donors using imine groups of porous organic cage compounds as acceptors leads to the formation of halogen-bonded frameworks. We report the use of two different imine...

A typical approach of a multicomponent crystal design starts with a retrosynthetic analysis of the target molecule followed by a one-pot reaction of all components. To develop protocols for multicomponent crystal syntheses, controlled stepwise syntheses of a selected crystalline ternary multicomponent system 1 involving 2-methylresorcinol (MRS), tetramethyl-pyrazine (TMP), and 1,2-bis(4-pyridyl)ethane (BPE) are presented. The obtained binary cocrystals 2 (involving MRS and TMP) and 3 (involving MRS and BPE) as well as the final resulting ternary multicomponent system 1 were characterized by X-ray analysis.

Phenibut is an anxiolytic drug approved for medical use in many eastern European states. With the exception of the HCl Salt of Phenibut no crystal structure related research has been conducted on this substance. Herein, the crystal structures of Phenibut and Phenibut⋅H2O are presented, including crystal packing analysis based on interaction energy calculations. IR spectra are shown alongside powder diffraction data and thermogravimetric analysis to characterize and compare structural as well as thermal properties of the examined Phenibut forms. Single crystal diffraction is used in conjunction with Crystal Explorer based Hirshfeld analysis to carefully identify the bonding interaction properties in each compound. Finally, a case is made regarding stability of the compared crystalline phases based on the conducted structural analyses and the quantification of the molecular interaction energies.

In this study, we compare the mechanochemical and classical solvent crystallization methods for forming maleates of GABA and its pharmaceutically active derivatives: Pregabalin, Gabapentin, Phenibut, and Baclofen. Common characterization techniques, like powder and single crystal X-ray diffraction, IR-spectroscopy, differential scanning calorimetry, thermogravimetric analysis and 1H-NMR spectroscopy, are used for the evaluation of structural and physicochemical properties. Our work shows that maleate formation is possible with all investigated target compounds. Large increases in solubility can be achieved, especially for Pregabalin, where up to twentyfold higher solubility in its maleate compared to the pure form can be reached. We furthermore compare the mechanochemical and solvent crystallization regarding quickness, reliability of phase production, and overall product quality. A synthetic route is shown to have an impact on certain properties such as melting point or solubility of the same obtained products, e.g., for Gabapentin and Pregabalin, or lead to the formation of hydrates vs. anhydrous forms. For the GABA and Baclofen maleates, the method of crystallization is not important, and similarly, good results can be obtained by either route. In contrast, Phenibut maleate cannot be obtained pure and single-phase by either method. Our work aims to elucidate promising candidates for the multicomponent crystal formation of blockbuster GABA pharmaceuticals and highlight the usefulness of mechanochemical production routes.

The controlled pH-based crystallization approach with acetic acid to the pharmaceutical interesting metastable polymorph II of the API γ-aminobutyric acid (GABA), which is hitherto accessible by sublimation under reduced pressure and high temperature, is described. Furthermore, the synthesis and single crystal characterization of a nonhydrated chiral [GABA-H][malate] compound is presented.