Structure Guided Discovery of Novel Pan Metallo-ß-Lactamase Inhibitors with Improved Gram-Negative Bacterial Cell Penetration.

The use of ß-lactam (BL) and ß-lactamase inhibitor combination to overcome BL antibiotic resistance has been validated through clinically approved drug products. However, unmet medical needs still exist for the treatment of infections caused by Gram-negative (GN) bacteria expressing metallo-ß-lactamases. Previously, we reported our effort to discover pan inhibitors of three main families in this class: IMP, VIM, and NDM. Herein, we describe our work to improve the GN coverage spectrum in combination with imipenem and relebactam. This was achieved through structure- and property-based optimization to tackle the GN cell penetration and efflux challenges. A significant discovery was made that inhibition of both VIM alleles, VIM-1 and VIM-2, is essential for broad GN coverage, especially against VIM-producing P. aeruginosa. In addition, pharmacokinetics and nonclinical safety profiles were investigated for select compounds. Key findings from this drug discovery campaign laid the foundation for further lead optimization toward identification of preclinical candidates.

Synthesis of a Complex and Highly Potent PCSK9 Inhibitor.

The solution-based gram-scale synthesis of complex and highly potent proprotein convertase subtilisin-like/kexin type 9 (PCSK9) inhibitor 1 is presented. Construction of Northern fragment 2, followed by stepwise installation of Eastern 3, Southern 4, and Western 5 fragments, provided macrocyclic precursor 19. This intermediate was cross-linked via an intramolecular azide-alkyne click reaction, which preceded macrolactamization to afford the core framework of compound 1. Finally, coupling with poly(ethylene glycol) side-chain-based 6 gave the PCSK9 inhibitor 1.

Total Synthesis of Darobactin A.

The collaborative total synthesis of darobactin A, a recently isolated antibiotic that selectively targets Gram-negative bacteria, has been accomplished in a convergent fashion with a longest linear sequence of 16 steps from d-Garner's aldehyde and l-serine. Scalable routes toward three non-canonical amino acids were developed to enable the synthesis. The closure of the bismacrocycle was realized through sequential, halogen-selective Larock indole syntheses, where the proper order of cyclizations proved crucial for the formation of the desired atropisomer of the natural product.

Metal-Free Stereoselective Synthesis of (E)- and (Z)-N-Monosubstituted ß-Aminoacrylates via Condensation Reactions of Carbamates.

N-monosubstituted ß-aminoacrylates are building blocks, which have been used in the preparation of amino acids and pharmaceuticals. Two efficient, stereoselective methods of preparation, via acid- or base-promoted condensation reactions of carbamates, are described. The base-promoted reaction is E-selective, while acid catalysis can, through the choice of solvent, selectively form E or Z. The acid-catalyzed E-selective process proceeds through a crystallization obviating the need for chromatographic purification.

Chemoselective Reduction of α-Cyano Carbonyl Compounds: Application to the Preparation of Heterocycles.

ß-Aminoacrylates are reactive intermediates that are useful building blocks in synthesis. General methods for their preparation typically afford α and ß disubstitution patterns or ß only. Molecules with only α-substituents (ß-hydrogen) are much less well-known. A chemoselective reductive tautomerization of α-cyanoacetates, using DIBAL-H, has been developed to access these valuable synthons. α,ß-Unsaturated cyanoacetates and α-cyanoketones can, also, be selectively reduced via this methodology. A series of heterocycles were prepared using these ß-enamino carbonyl compounds.

Site selective syntheses of [(3)H]omeprazole using hydrogen isotope exchange chemistry.

Omeprazole (Prilosec®) is a selective and irreversible proton pump inhibitor used to treat various medical conditions related to the production of excess stomach acids. It functions by suppressing secretion of those acids. Radiolabeled compounds are commonly employed in the drug discovery and development process to support efforts including library screening, target identification, receptor binding, assay development and validation and safety assessment. Herein, we describe synthetic approaches to the controlled and selective labeling of omeprazole with tritium via hydrogen isotope exchange chemistry. The chemistry may also be used to prepare tritium labeled esomeprazole (Nexium®), the active pure (S)-enantiomer of omeprazole.

NMR-based approach to the analysis of radiopharmaceuticals: radiochemical purity, specific activity, and radioactive concentration values by proton and tritium NMR spectroscopy.

Compounds containing tritium are widely used across the drug discovery and development landscape. These materials are widely utilized because they can be efficiently synthesized and produced at high specific activity. Results from internally calibrated (3)H and (1)H nuclear magnetic resonance (NMR) spectroscopy suggests that at least in some cases, this calibrated approach could supplement or potentially replace radio-high-performance liquid chromatography for radiochemical purity, dilution and scintillation counting for the measurement of radioactivity per volume, and liquid chromatography/mass spectrometry analysis for the determination of specific activity. In summary, the NMR-derived values agreed with those from the standard approaches to within 1% to 9% for solution count and specific activity. Additionally, the NMR-derived values for radiochemical purity deviated by less than 5%. A benefit of this method is that these values may be calculated at the same time that (3)H NMR analysis provides the location and distribution of tritium atoms within the molecule. Presented and discussed here is the application of this method, advantages and disadvantages of the approach, and a rationale for utilizing internally calibrated (1)H and (3)H NMR spectroscopy for specific activity, radioactive concentration, and radiochemical purity whenever acquiring (3)H NMR for tritium location.

A novel 5-[1,3,4-oxadiazol-2-yl]-N-aryl-4,6-pyrimidine diamine having dual EGFR/HER2 kinase activity: design, synthesis, and biological activity.

A novel 5-[1,3,4-oxadiazol-2-yl]-N-aryl-4,6-pyrimidine diamine was synthesized and found to have potent dual EGFR/HER2 kinase inhibitory activity. The structure-based drug design of this molecule as well as the kinase and cellular inhibition of HER2 kinase dependent cell lines will be discussed.

Synthesis, structure-activity relationship and in vivo antiinflammatory efficacy of substituted dipiperidines as CCR2 antagonists.

A series of substituted dipiperidine compounds have been synthesized and identified as selective CCR2 antagonists. Combining the most favorable substituents led to the discovery of remarkably potent CCR2 antagonists displaying IC50 values in the nanomolar range. Compound 7a had outstanding selectivity over CCR1, CCR3, CCR4, CCR5, CCR6, CCR7, and CCR8 and showed excellent efficacy in adjuvant-induced arthritis model, collagen-induced arthritis model, and allergic asthma model.