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The new homochiral 1D metal–organic coordination polymer {Cu[bdc-(N-MePro)H2O]·0.25H2O}n was synthesized using 2-[(1-methyl- L -prolyl)amino]terephthalic acid, which was obtained for the first time. The unique crystal structure of the new compound was determined using powder X-ray diffraction. The catalytic performance of {Cu[bdc-(N-MePro)H2O]·0.25H2O}n in the asymmetric ring opening reactions of styrene oxide and cyclohexene oxide with aniline was evaluated. [ABSTRACT FROM AUTHOR]

Raltegravir (RLT) is a human immunodeficiency virus integrase strand transfer inhibitor that is prescribed for the treatment of HIV-1 infection. The drug belongs to biopharmaceutics classification system (BCS) class II category and has poor aqueous solubility and chemical stability in acidic/basic medium. Polymorph screening was performed to search for an alternative solid form with improved drug attributes. By serendipity, this screening gave anhydrous RLT (form A) and two crystalline solid phases of impurity C. The RLT form A and impurity C were characterised using powder X-ray diffraction (XRD), thermal analysis (differential scanning calorimetry/thermogravimetric analysis) and vibrational spectroscopy (Fourier-transform infrared). The crystal structures of form A and impurity C were determined from the high resolution powder XRD patterns using Rietveld refinement, thus revealing their conformational and synthon differences. The crystal structure of impurity C1 (MeOH solvate) was solved from single crystal XRD and demonstrates the packing and conformational differences compared to parent phase C. The dissolution/solubility experiments confirmed that form A has a higher solubility than its hydrate in aqueous ethanol medium. Compared to the commercialized RLT potassium salt (RLT-K), form A did not offer improved chemical stability during acid hydrolysis (high-performance liquid chromatography data). Rather, impurity C exhibited higher thermal stability and aqueous stability compared to other RLT solid forms in an acidic medium. [ABSTRACT FROM AUTHOR]

Cephalexin (CPX) is a first-generation β-lactam antibiotic with great efficiency to kill Gram-positive and Gram-negative bacteria. Although the drug belongs to the BCS class I category of high solubility/permeability, it exhibits up to 20% degradation in acidic medium (pH 1.2). In order to improve its chemical stability, pharmaceutical cocrystal screening was carried out with a variety of ionizable/zwitterionic carboxylic acids and amino acids that resulted in a cocrystal with serine (SER), a cocrystal hydrate with 4-hydroxybenzoic acid (PHB) and a salt hydrate with 2,6-dihydroxybenzoic acid (DHB). A liquid-assisted grinding method was employed to obtain the multicomponent solid forms of CPX. The novel solid forms were characterized by powder X-ray diffraction (PXRD), FT-IR spectroscopy and thermal methods (DSC, TGA). The crystal structures of CPX–SER and CPX–DHB were solved in chiral space groups (P212121/P21) by powder XRD and single-crystal XRD techniques. Multiple functional groups in flexible CPX along with the coformer resulted in a complex hydrogen bonding network. The CPX–coformer heterosynthon is the key to forming multicomponent solids, although ionic interactions between the quaternary ammonium cation and the carboxylate ion of CPX are robust in all the solid forms. All the multicomponent solid forms were stable under 35 ± 5 °C and 75 ± 5% relative humidity conditions for a month. An aqueous stability experiment in 0.1 N HCl medium showed that the chemical stability of the novel multicomponent solids of CPX improved up to 2-fold compared to the commercial CPX monohydrate. [ABSTRACT FROM AUTHOR]

Dexamethasone (DEX) is a corticosteroid drug used to treat arthritis and asthma and considered a promising drug for the treatment of COVID-19. The major drawback of DEX is its poor aqueous solubility (89 mg L−1). In order to enhance its solubility, polymorph and cocrystal screening was performed, which resulted in the crystallization of the metastable polymorph (commercial Form A) along with two novel cocrystals with catechol (CAT) and resorcinol (RES). These solid forms were characterized by powder-XRD, DSC, and finally single-crystal XRD. The commercial Form A (P212121, Z′ = 1, new) and reported Form B (P212121, Z′ = 2) were harvested concomitantly during crystallization from CH3CN. While Form A constitutes a trimer ring motif, Form B maintains a dimer synthon between two symmetry independent DEX molecules and they are designated as synthon as well as packing polymorphs. The presence of CAT/RES breaks dimer/trimer synthons in the cocrystal lattice of the drug molecule and forms a hydrogen-bonded sandwich between two anti-parallel DEX chains. In addition, both DEX–CAT and DEX–RES are proved to be isostructural cocrystals based on their identical lattice parameters and molecular packing arrangement. Aqueous solubility (24 h) experiments indicated that commercial Form A was 1.5-fold more soluble than Form B and inversely correlated with their melting points. DEX–CAT and DEX–RES cocrystals improved the aqueous solubility by 2–5-fold than commercial Form A, although both the cocrystals transformed to the mixture of polymorphs during solubility experiments. The improved solubility of the DEX–CAT cocrystal may offer more bioavailability of DEX. [ABSTRACT FROM AUTHOR]

The localization and distribution of germanium atoms in the framework positions of Ge-BEC zeolite upon silylation have been studied using synchrotron XRD and 19F NMR. The high thermal stability of Ge-BEC material synthesized using 1-benzyl-1,4-diazabicyclo[2.2.2]octane as the structure-directing agent (SDA) has been observed, enabling the preparation of calcined Ge-BEC. Unexpectedly, the inhomogeneous enrichment of double-four membered ring (d4r) subunits in the BEC structure with germanium has been observed. The interaction of germanosilicate with (NH4)2SiF6 led to the selective substitution of germanium atoms in T2 and T3 positions with silicon, while fluoride anions preferably occupy positions inside d4r subunits. [ABSTRACT FROM AUTHOR]