Absolute Configuration of Chiral Molecules by VCD

This week in the world of BioTools:

Structural and in Vitro Functional Characterization of a Menthyl TRPM8 Antagonist Indicates Species-Dependent Regulation

V. Blair Journigan*David Alarcón-AlarcónZhiwei Feng, Yuanqiang Wang, Tianjian LiangDenise C. Dawley, A. R. M. Ruhul Amin, Camila Montano, Wade D. Van Horn, Xiang-Qun Xie, Antonio Ferrer-Montiel, and Asia Fernández-Carvajal

March 31, 2021, ACS Med. Chem. Lett.


TRPM8 antagonists derived from its cognate ligand, (−)-menthol, are underrepresented. We determine the absolute stereochemistry of a well-known TRPM8 antagonist, (−)-menthyl 1, using VCD and 2D NMR. We explore 1 for its antagonist effects of the human TRPM8 (hTRPM8) orthologue to uncover species-dependent inhibition versus rat channels. (−)-Menthyl 1 inhibits menthol- and icilin-evoked Ca2+ responses at hTRPM8 with IC50 values of 805 ± 200 nM and 1.8 ± 0.6 μM, respectively, while more potently inhibiting agonist responses at the rat orthologue (rTRPM8 IC50 (menthol) = 117 ± 18 nM, IC50 (icilin) = 521 ± 20 nM). Whole-cell patch-clamp recordings of hTRPM8 confirm the 1 inhibition of menthol-stimulated currents, with an IC50 of 700 ± 200 nM. We demonstrate that 1 possesses ≥400-fold selectivity for hTRPM8 versus hTRPA1/hTRPV1. (−)-menthyl 1 can be used as a novel chemical tool to study hTRPM8 pharmacology and differences in species commonly used in drug discovery.

Multigram Preparation of BRD4780 Enantiomers and Assignment of Absolute Stereochemistry

Brian T. Chamberlain*, Mathilde Vincent, Jordan Nafie, Peter Müller, Anna Greka, and Florence F. Wagner*

February 22, 2021, The Journal of Organic Chemistry



The development of a multigram synthesis of 3-exo-isopropylbicyclo[2.2.1]heptan-2-endo-amine hydrochloride (1) (also known as BRD4780 and AGN-192403) is described. The process involves protection of the amine as 4-nitrobenzyl carbamate, pNZ, which enables chiral SFC chromatography. The absolute configuration (AC) of the individual enantiomers has been determined by Mosher’s amide method, VCD spectroscopy, and X-ray crystallography. We highlight the VCD approach as a rapid and effective means of AC determination that can be deployed directly on the target compounds.

FTIR Spectroscopy Detects Intermolecular β-Sheet Formation Above the High Temperature Tm for Two Monoclonal Antibodies

Garrett Baird, Chris Farrell, Jason Cheung, Andrew Semple, Jeffery Blue & Patrick L. Ahl

The Protein Journal  39, pages 318–327 (2020)



The temperature-dependent secondary structure of two monoclonal IgG antibodies, anti-IGF1R and anti-TSLP, were examined by transmission mode Fourier Transform Infrared (FTIR) spectroscopy. Anti-IGF1R and anti-TSLP are IgG monoclonal antibodies (mAbs) directed against human Insulin-like Growth Factor 1 Receptor for anti-tumor activity and Thymic Stromal Lymphopoietin cytokine for anti-asthma activity, respectively. Differential scanning calorimetry (DSC) clearly indicates both antibodies in their base formulations have a lower temperature protein conformational change near 70 °C (Tm1) and a higher temperature protein conformational change near 85 °C (Tm2). Thermal scanning dynamic light scatting (TS-DLS) indicates a significant particle size increase for both antibodies near Tm2 suggesting a high level of protein aggregation. The nature of these protein conformational changes associated with increasing the formulation temperature and decreasing sucrose concentration were identified by transmission mode FTIR and second derivative FTIR spectroscopy of temperature controlled aqueous solutions of both monoclonal antibodies. The transition from intra-molecular β sheets to inter-molecular β sheets was clearly captured for both monoclonal antibodies using FTIR spectroscopy. Finally, FTIR Spectroscopy was able to show the impact of a common excipient such as sucrose on the stability of each monoclonal antibody, further demonstrating the usefulness of FTIR spectroscopy for studying protein aggregation and formulation effects.

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