Discovery of SHR1653, a Highly Potent and Selective OTR Antagonist with Improved Blood-Brain Barrier Penetration

[Astragalus polysaccharide protects against blood-brain barrier damage in MCAO rats by inhibiting P2X7R channel]

OBJECTIVE

To investigate the protective effect of astragalus polysaccharide (APS) against blood-brain barrier in a rat model of middle cerebral artery occlusion (MCAO) and the role of P2X7R channel in the protective mechanism.

METHODS

In rat microglial cell models of oxygen and glucose deprivation (OGD) or ATP treatment, the formation of blood-brain barrier in vitro was assessed using the leak test, and the effect of APS on the permeability of the blood-brain barrier was determined using LC-MS. In 12 SD rats, MCAO model was established followed by treatment with intraperitoneal injection of normal saline (n= 6) or APS (45 mg/kg, n=6) for 3 consecutive days, with another 6 rats without MCAO receiving saline injections as the control group. The permeability of the blood-brain barrier of the rats was evaluated by determining Evans blue (EB) extravasation, and ATP content in the brain tissue was detected using ELISA; the expression levels of matrix metalloproteinase-9 (MMP-9) and P2X7R in the brain tissue were detected with Western blot.

RESULTS

In the in vitro cell model of OGD or ATP treatment, APS treatment obviously promoted the repair of blood-brain barrier integrity. In the rat models, the EB content in the brain tissue and the blood-brain barrier permeability increased significantly in MCAO+saline group and MCAO+APS group as compared with those in the control group (P < 0.01). Compared with saline treatment, APS treatment significantly decreased EB content in the brain tissue and improved the blood-brain barrier permeability in the MCAO rats (P < 0.05). MCAO caused a significant reduction of ATP content and obviously increased the expression levels of MMP-9 and P2X7R in the brain tissue of the rats (P < 0.01), and these changes were significantly alleviated after APS treatment (P < 0.01 or 0.05).

CONCLUSION

APS can protect the brain tissue of MCAO rats by stabilizing the internal environment, down-regulating the expression of MMP-9 and improving the permeability of blood-brain barrier under cerebral ischemia and hypoxia, and its mechanism may involve the inhibition of P2X7R channel.

Construction of Spiro[3-azabicyclo[3.1.0]hexanes] via 1,3-Dipolar Cycloaddition of 1,2-Diphenylcyclopropenes to Ninhydrin-Derived Azomethine Ylides

The multi-component 1,3-dipolar cycloaddition of ninhydrin, α-amino acids (or peptides), and cyclopropenes for the synthesis of spirocyclic heterocycles containing both 3-azabicyclo[3.1.0]hexane and 2H-indene-1,3-dione motifs has been developed. This method provides easy access to 3-azabicyclo[3.1.0]hexane-2,2′-indenes with complete stereoselectivity and a high degree of atom economy under mild reaction conditions. A broad range of cyclopropenes and α-amino acids have been found to be compatible with the present protocol, which offers an opportunity to create a new library of biologically significant scaffold (3-azabicyclo[3.1.0]hexane). In addition, the сomprehensive study of mechanism of azomethine ylide formation from ninhydrin and sarcosine was performed by means of M11 density functional theory (DFT) calculations. It has been revealed that experimentally observed 1-methylspiro[aziridine-2,2′-indene]-1′,3′-dione is a kinetically controlled product of this reaction and appears to act as a 1,3-dipole precursor. This theoretical study also shed light on the main transformations of the azomethine ylide derived from ninhydrin and sarcosine such as a 1,3-dipolar cycloaddition to cyclopropene dipolarophiles, a dimerization reaction and a (1+5) electrocyclization reaction. The antitumor activity of some synthesized compounds against cervical carcinoma (HeLa­) cell line was evaluated in vitro by MTS-assay.

Divergent Synthesis of Substituted Amino-1,2,4-triazole Derivatives

A divergent efficient assembly of disubstituted 1,2,4-triazoles was established by cyclization of readily accessible N′-nitro-2-hydrocarbylidene-hydrazinecarboximidamides with moderate to excellent yields under mild reaction conditions. This divergent synthetic strategy was achieved simply by varying the reaction conditions. Under acidic conditions, amino-1,2,4-triazoles were obtained by an intramolecular redox reaction involving the NO2 group. Control experiments and DFT studies revealed that this transformation proceeds via an intramolecular 1,3-hydride transfer pathway leading to HNO2 elimination. Under neutral conditions with water as the solvent, nitroimino-1,2,4-triazoles were obtained by oxidative intramolecular annulation under air.

Cu-Enabled [3 + 2] Annulation of In Situ Formed Nitrile Ylides with Aryldiazonium Salts: Access to 5-Cyano-1,2,4-Triazoles

The unified construction of cyano-substituted 1,2,4-triazoles, particularly the 5-cyano counterparts, remains underdeveloped. Herein we describe a three-component method to access a wide range of 1-aryl 5-cyano-1,2,4-triazoles using readily available 2-diazoacetonitriles, nitriles, and aryldiazonium salts. This regiospecific synthesis relies on the dipolar [3 + 2] annulation of the in situ formed nitrile ylides with aryldiazonium salts. Furthermore, this protocol can be amendable to gram-scale synthesis, chemical transformations of the nitrile moieties, and access to chiral bis(cyano-triazole)-1,1'-naphthalene, which would all be likely applicable in the synthesis of structurally diverse bioactive compounds and novel bidentate ligands for asymmetric catalysis.

Opportunities for Tapping into Three-Dimensional Chemical Space through a Quaternary Carbon

A quaternary carbon bears four other carbon substituents or combination of four non-hydrogen substituents at four vertices of a tetrahedron. The spirocyclic quaternary carbon positioned at the center of a bioactive molecule offers conformational rigidity, which in turn reduces the penalty for conformational entropy. The quaternary carbon is a predominant feature of natural product structures and has been associated with more effective and selective binding to target proteins compared to planar compounds with a high sp² count. The presence of a quaternary carbon stereocenter allows the exploration of novel chemical space to obtain new molecules with enhanced three-dimensionality. These characteristics, coupled to an increasing awareness to develop sp³-rich molecules, boosted utility of quaternary carbon stereocenters in bioactive compounds. It is hoped that this Perspective will inspire the chemist to utilize quaternary carbon stereocenters to enhance potency, selectivity, and other drug-like properties.

trans-Selective Aryldifluoroalkylation of Endocyclic Enecarbamates and Enamides by Nickel Catalysis

Efficient methods for the dicarbofuntionalization of the cyclic alkenes 2-pyrroline and 2-azetine are limited. Particularly, the dicarbofunctionalization of endocyclic enecarbamates to achieve fluorinated compounds remains an unsolved issue. Reported here is a nickel-catalyzed trans-selective dicarbofunctionalization of N-Boc-2-pyrroline and N-Boc-2-azetine, a class of endocyclic enecarbamates previously unexplored for transition metal catalyzed dicarbofunctionalization. The reaction can be extended to six- and seven-membered endocyclic enamides. A variety of arylzinc reagents and bromodifluoroacetate, and its derivatives, undergo the reaction, providing straightforward and efficient access to an array of pyrrolidine- and azetidine-containing fluorinated amino acids and oligopeptides, which may have applications in the life sciences.