Vicinal diaryl azole-based urea derivatives as potential cholesterol lowering agents acting through inhibition of SOAT enzymes

Development of an oxazole-based cleavable linker for peptides

We report the development of a new oxazole-based cleavable linker to release peptides from attached cargo. Oxazoles are stable to most reaction conditions, yet they can be rapidly cleaved in the presence of single-electron oxidants like cerium ammonium nitrate (CAN). An oxazole linker could be synthesized and attached to peptides through standard solid-phase peptide coupling reactions. Cleavage of these peptide-oxazole conjugates is demonstrated on a broad scope of peptides containing various natural and unnatural amino acids. These results represent the first example of a peptide-based linker that is cleaved through single-electron oxidation. The oxazole is also demonstrated to be a suitable linker for both the release of a peptide from a conjugated small molecule and the orthogonal release of cargo from a peptide containing multiple cleavable linkers. Oxazole linkers could serve as a promising tool for peptide screening platforms such as peptide-encoded libraries.

Identification of a novel class of cortisol biosynthesis inhibitors and its implications in a therapeutic strategy for hypercortisolism

AIMS

Dysregulation of adrenocortical steroid (corticosteroids) biosynthesis leads to pathological conditions such as Cushing's syndrome. Although several classes of steroid biosynthesis inhibitors have been developed to treat cortisol overproduction, limitations such as insufficient efficacy, adverse effects, and/or tolerability still remain. The present study aimed to develop a new class of small molecules that inhibit cortisol production, and investigated their putative modes of action.

MAIN METHODS

We screened an in-house chemical library with drug-like chemical scaffolds using human adrenocortical NCI-H295R cells. We then evaluated and validated the effects of the selected compounds at multiple regulatory steps of the adrenal steroidogenic pathway. Finally, genome-wide RNA expression analysis coupled with gene enrichment analysis was conducted to infer possible action mechanisms.

KEY FINDINGS

A subset of benzimidazolylurea derivatives, including a representative compound (designated as CJ28), inhibited both basal and stimulated production of cortisol and related intermediate steroids. CJ28 attenuated the mRNA expression of multiple genes involved in steroidogenesis and cholesterol biosynthesis. Furthermore, CJ28 significantly attenuated de novo cholesterol biosynthesis, which contributed to its suppression of cortisol production.

SIGNIFICANCE

We identified a novel chemical scaffold that exerts inhibitory effects on cortisol and cholesterol biosynthesis via coordinated transcriptional silencing of gene expression networks. Our findings also reveal an additional adrenal-directed pharmacological strategy for hypercortisolism involving a combination of inhibitors targeting steroidogenesis and de novo cholesterol biosynthesis.

Direct Synthesis of N-(1,2,5-Oxadiazolyl)hydrazones through a Diazotization/Reduction/Condensation Cascade

A straightforward synthesis of a series of previously unknown N-(1,2,5-oxadiazolyl)hydrazones through the diazotization/reduction/condensation cascade of amino-1,2,5-oxadiazoles was accomplished. The described protocol was suitable for a wide array of target hydrazones, which were prepared in good to high yields under smooth reaction conditions with very good functional group tolerance. Importantly, the presented approach unveils a direct route to in situ generation of previously inaccessible (1,2,5-oxadiazolyl)hydrazines. In addition, a first example of the ionic structure incorporating a protonated hydrazone motif linked to the 1,2,5-oxadiazole 2-oxide subunit was synthesized, indicating the stability of prepared compounds toward acid-promoted hydrolysis. Overall, this method provides a direct access to the isosteric analogues of drug candidates for treatment of various neglected diseases, thus enabling their potential application in medicinal chemistry and drug design.

Crystal structure of poly[(μ3-4-amino-1,2,5-oxa-diazole-3-hydroxamato)thallium(I)]

The title compound represents the thallium(I) salt of a substituted 1,2,5-oxa-diazole, [Tl(C3H3N4O3)] n , with amino- and hydroxamate groups in the 4- and 3- positions of the oxa-diazole ring, respectively. In the crystal, the deprotonated hydroxamate group represents an inter-mediate between the keto/enol tautomers and forms a five-membered chelate ring with the thallium(I) cation. The coordination sphere of the cation is augmented to a distorted disphenoid by two monodentately binding O atoms from two adjacent anions, leading to the formation of zigzag chains extending parallel to the b axis. The cohesion within the chains is supported by π-π stacking [centroid-centroid distance = 3.746 (3) Å] and inter-molecular N-H⋯N hydrogen bonds.

Mild Synthesis of Substituted 1,2,5-Oxadiazoles Using 1,1'-Carbonyldiimidazole as a Dehydrating Agent

1,1'-Carbonyldiimidazole was found to induce the formation of a variety of 3,4-disubstituted 1,2,5-oxadiazoles (furazans) from the corresponding bisoximes at ambient temperature. This method enables these inherently energetic compounds to be prepared at temperatures well below their decomposition points and with improved functional group compatibility relative to prior methods. Conditions were developed that allowed for the first high-yielding synthesis of chlorofurazans from their amino counterparts, enabling the mild synthetic manipulation of these heterocycles.