Discovery of highly selective and potent monoamine oxidase B inhibitors: Contribution of additional phenyl rings introduced into 2-aryl-1,3,4-oxadiazin-5(6 H )-one

Copper-catalyzed intermolecular formal (5 + 1) annulation of 1,5-diynes with 1,2,5-oxadiazoles

One-carbon homologation reactions based on one-carbon insertion into the N-O bond of heterocycles have received tremendous interest over the past decades. However, these protocols have to rely on the use of hazardous and not easily accessible diazo compounds as precursors, and examples of the relevant asymmetric catalysis have not been reported. Here we show that a copper-catalyzed intermolecular formal (5 + 1) annulation of 1,5-diynes with 1,2,5-oxadiazoles involving one-carbon insertion into the heterocyclic N-O bond via non-diazo approach. This method enables practical and atom-economic synthesis of valuable pyrrole-substituted oxadiazines in generally moderate to good yields under mild reaction conditions. In addition, the possibility of such an asymmetric formal (5 + 1) annulation also emerges.

DMSO as a Dual Carbon Synthon and Water as Oxygen Donor for the Construction of 1,3,5-Oxadiazines from Amidines

A selective and efficient synthesis of diaryl 1,3,5-oxadiazines was established for the first time from simple and readily available amidines in wet DMSO. DMSO was employed as a dual carbon synthon and water offered the oxygen atom to construct the oxadiazine ring. The reaction involved two new C-N and two new C-O bond formations.

Diastereoselective Synthesis of Nonplanar 3-Amino-1,2,4-oxadiazine Scaffold: Structure Revision of Alchornedine

Herein, we report the diastereoselective synthesis of a 3-amino-1,2,4-oxadiazine (AOXD) scaffold. The presence of a N-O bond in the ring prevents the planar geometry of the aromatic system and induces a strong decrease in the basicity of the guanidine moiety. While DIBAL-H appeared to be the most efficient reducing agent because it exhibited high diastereoselectivity, we observed various behaviors of the Mitsunobu reaction on the resulting β-aminoalcohol, leading to either inversion or retention of the configuration depending on the steric hindrance in the vicinity of the hydroxy group. The physicochemical properties (pK_a and log D) and hepatic stability of several AOXD derivatives were experimentally determined and found that the AOXD scaffold possesses promising properties for drug development. Moreover, we synthesized alchornedine, the only natural product with the AOXD scaffold. Based on a comparison of the analytical data, we found that the reported structure of alchornedine was incorrect and hypothesized a new one.

Single Heterocyclic Compounds as Monoamine Oxidase Inhibitors: From Past to Present

Inhibitors of monoamine oxidase (MAO) have shown therapeutic values in a variety of neurodegenerative diseases such as depression, Parkinson's disease and Alzheimer's disease. Heterocyclic compounds exhibit a broad spectrum of biological activities and vital leading compounds for the development of chemical drugs. Herein, we focus on the synthesis and screening of novel single heterocyclic derivatives with MAO inhibitory activities during the past decade. This review covers recent pharmacological advancements of single heterocyclic moiety along with structure- activity relationship to provide better correlation among different structures and their receptor interactions.

Monoamine oxidases inhibitors from Colvillea racemosa: Isolation, biological evaluation, and computational study

Bioassay-guided fractionation and chemical investigation of Colvillea racemosa stems led to identification of two new α, β-dihydroxydihydrochalcones, colveol A (1) and colveol B (2) along with fifteen known compounds. The structures were elucidated via interpretation of spectroscopic data. The absolute configurations of the dihydrochalcones 1 and 2 were assigned by a combination of chemical modification and electronic circular dichroism data. The isolated compounds were evaluated for their inhibition activity toward recombinant human monoamine oxidases (rhMAO-A and -B). Compound 1 demonstrated preferential inhibition against hMAO-A isoenzyme (IC₅₀ 0.62μM, SI_A/B 0.02) while S-naringenin (13) and isoliquiritigein (15) demonstrated preferential hMAO-B inhibition (IC₅₀ 0.27 and 0.51μM, SI_A/B 31.77 and 44.69, respectively). Fisetin (11) showed inhibition against hMAO-A with IC₅₀ value of 4.62μM and no inhibitory activity toward hMAO-B up to 100μM. Molecular docking studies for the most active compounds were conducted to demonstrate the putative binding modes. It suggested that 1 interacts with Gln215, Ala111, Phe352, and Phe208 amino acid residues which have a role in the orientation and stabilization of the inhibitor binding to hMAO-A, while S-naringenin (13) occupies both entrance and substrate cavities and interacts with Tyr326, a critical residue in inhibitor recognition in hMAO-B.