Development and chromatographic exploration of stable-bonded cross-linked amino silica against classical amino phases.

The present work reports on a novel stable-bonded amino silica stationary phase obtained by crosslinking of surface aminopropyl moieties using triglycidyl isocyanurate. The obtained cross-linked amido-amino network silica material exhibited superior hydrolytic stability compared to classical 3-aminopropyl phases and showed, inter alia, excellent separation of nine therapeutically effective sulfonamides in hydrophilic interaction/weak anion exchange chromatography elution mode. Additionally, the separation of carbohydrates was investigated under classical hydrophilic interaction chromatography conditions as well proving the suitability of the novel phase for such applications. For the evaluation of the hydrolytic stability the prepared material, as well as two commercially available benchmark columns and a set of in-house synthesized amino-modified materials, were exposed to harsh aqueous mobile phase conditions for in total of 50 h at elevated temperature. In this context, the materials were examined by elemental analysis, (13 C and 29 Si cross-polarization/magic angle spinning) solid-state nuclear magnetic resonance, and a chromatographic test before and subsequent to the exposure to these stress conditions. Lastly, the new stationary phase was classified in comparison to a set of commercially available stationary phases by principal component analysis of resultant retention factors gained from chromatographic standard tests.

Correction to "Cathepsin-Targeting SARS-CoV-2 Inhibitors: Design, Synthesis, and Biological Activity".

[This corrects the article DOI: 10.1021/acsptsci.3c00313.].

Cathepsin-Targeting SARS-CoV-2 Inhibitors: Design, Synthesis, and Biological Activity.

Cathepsins (Cats) are proteases that mediate the successful entry of SARS-CoV-2 into host cells. We designed and synthesized a tailored series of 21 peptidomimetics and evaluated their inhibitory activity against human cathepsins L, B, and S. Structural diversity was realized by combinations of different C-terminal warhead functions and N-terminal capping groups, while a central Leu-Phe fragment was maintained. Several compounds were identified as promising cathepsin L and S inhibitors with Ki values in the low nanomolar to subnanomolar range, for example, the peptide aldehydes 9a and 9b (9a, 2.67 nM, CatL; 0.455 nM, CatS; 9b, 1.76 nM, CatL; 0.512 nM, CatS). The compounds' inhibitory activity against the main protease of SARS-CoV-2 (Mpro) was additionally investigated. Based on the results at CatL, CatS, and Mpro, selected inhibitors were subjected to investigations of their antiviral activity in cell-based assays. In particular, the peptide nitrile 11e exhibited promising antiviral activity with an EC50 value of 38.4 nM in Calu-3 cells without showing cytotoxicity. High metabolic stability and favorable pharmacokinetic properties make 11e suitable for further preclinical development.

Branched medium-chain fatty acid profiling and enantiomer separation of anteiso-forms of teicoplanin fatty acyl side chain RS3 using UHPLC-MS/MS with polysaccharide columns.

This work reports on targeted UHPLC-tandem mass spectrometry methods for the chiral separation of anteiso-methyl branched fatty acids (aiFAs). The methods involve precolumn derivatization with 1-naphthylamine and chiral separation on Chiralpak IG-U. anteiso-Methyl branched fatty acids with up to eight carbons can be separated. A method was used for the assignment of the absolute configuration of an aiFA present as fatty acyl residue of the teicoplanin mixture, namely teicoplanin RS3. Furthermore, the excellent methylene selectivity and improved selectivity for constitutional isomers of the polysaccharide columns was exploited for the elucidation and structural confirmation of previously unknown fatty acyl residues in teicoplanin. This shows the versatility and practical applicability of polysaccharide columns as orthogonal stationary phases to reversed-phase for structural elucidation of natural compounds. The developed methods are useful tools for related subdisciplines such as targeted metabolomics and lipidomics.

Principles and Applications of CF2X Moieties as Unconventional Halogen Bond Donors in Medicinal Chemistry, Chemical Biology, and Drug Discovery.

As an orthogonal principle to the established (hetero)aryl halides, we herein highlight the usefulness of CF2X (X = Cl, Br, or I) moieties. Using tool compounds bearing CF2X moieties, we study their chemical/metabolic stability and their logP/solubility, as well as the role of XB in their small molecular crystal structures. Employing QM techniques, we analyze the observed interactions, provide insights into the conformational flexibilities and preferences in the potential interaction space. For their application in molecular design, we characterize their XB donor capacities and its interaction strength dependent on geometric parameters. Implementation of CF2X acetamides into our HEFLibs and biophysical evaluation (STD-NMR/ITC), followed by X-ray analysis, reveals a highly interesting binding mode for fragment 23 in JNK3, featuring an XB of CF2Br toward the P-loop, as well as chalcogen bonds. We suggest that underexplored chemical space combined with unconventional binding modes provides excellent opportunities for patentable chemotypes for therapeutic intervention.

Comprehensive profiling of conjugated fatty acid isomers and their lipid oxidation products by two-dimensional chiral RP×RP liquid chromatography hyphenated to UV- and SWATH-MS-detection.

This research reports on the development of a comprehensive two-dimensional liquid chromatography (2D-LC) method hyphenated to inline DAD-UV and ESI-QTOF-MS/MS-detection for the separation of conjugated polyunsaturated fatty acid isomers and structurally related (saturated, unconjugated, oxidized) compounds. In pharmaceutical lipid formulations conjugated fatty acids can be found as impurities, generated by oxidation of polyunsaturated fatty acids. Due to the structural complexity of resultant multi-component samples one dimensional liquid chromatography may be suboptimal for quality control and impurity profiling. The screened reversed-phase columns showed a lack of selectivity for the conjugated fatty acid isomers but the resolutions improved with the shape selectivity of the stationary phases (C18- < C30- < cholesteryl-ether-bonded). Further enhanced selectivity for the non-chiral conjugated FAs could be achieved with amylose/cellulose-based chiral stationary phases (CSPs) which harbor cavities for selective inclusion depending on E/Z configurations of the double bonds of the analytes. Amylose-based CSPs showed higher selectivity for conjugated fatty acids than the cellulose-based polysaccharide CSPs. Hyphenating the chiral and reversed-phase columns in a comprehensive 2D-LC-setup was favorable since they showed orthogonality and good compatibility, because both were operated under RP-conditions. The chiral dimension (1D) mainly separated the different isomers, while the reversed-phase dimension (2D) separated according to number of double bonds and degree of oxidation. Using this setup, advanced structural annotation of unknowns was possible based on UV-, MS1- and MS2-spectra. Data-independent acquisition (by SWATH) enabled differentiation of positional isomers of oxidized lipids by characteristic MS2-fragments and elucidation of co-eluted compounds by selective extracted ion chromatograms of fragment ions (MS2 EICs).