Synthesis of multi-substituted 1,2,4-triazoles utilising the ambiphilic reactivity of hydrazones

The synthesis of N-alkyl-1H-1,2,4-triazoles from N,N-dialkylhydrazones and nitriles via formal [3+2] cycloaddition including the C-chlorination/nucleophilic addition/cyclisation/dealkylation sequence was developed. This sequential reaction utilising the in situ generation of hydrazonoyl chloride based on the ambiphilic reactivity of hydrazones afforded a variety of multi-substituted N-alkyl-triazoles in high yields. The synthetic utility of multi-substituted triazoles was also demonstrated by further transformations.

Design, synthesis and biological evaluation of glycolamide, glycinamide, and β-amino carbonyl 1,2,4-triazole derivatives as DPP-4 inhibitors

Through modification of the skeleton of Sitagliptin and Vildagliptin, we successfully synthesized and built-up four series of 1,2,4-triazole derivatives, containing N,O-disubstituted glycolamide, N,N'-disubstituted glycinamide, β-amino ester, and β-amino amide as linkers, for the development of new dipeptidyl peptidase 4 (DPP-4) inhibitors. The synthetic strategy for glycolamides or glycinamides involved convenient two-steps reaction: functionalized transformation of 2-chloro-N-(2,4,5-triflurophenyl)acetamide 9 (hydroxylation or amination) and esterification or amidation of 1,2,4-triazole-3-carboxylic acid. On the other hand, the one-pot synthesis procedure, including substitution and deprotection, was developed for the preparation of β-amino carbonyl 1,2,4-triazoles from (1H-1,2,4-triazol-3-yl)methanol 12 or (1H-1,2,4-triazol-3-yl)methanamine 13 and Boc-(R)-3-amino-4-(2,4,5-trifluoro-phenyl)-butyric acid 14. All of glycolamides, glycinamides, and β-amino carbonyl 1,2,4-triazoles were also evaluated against DPP-4 inhibitory activity. Based on the SAR study of DPP-4 inhibitory capacity, β-amino ester 5n and β-amino amide 1,2,4-triazoles 6d and 6p possessed the significant inhibition of DPP-4 (IC₅₀ < 51.0 nM), particularly for compound 6d (IC₅₀ = 34.4 nM). The selectivity evaluation indicated compound 5n and 6p had excellent selectivity over QPP, DPP-8, and DPP-9. In addition, the docking results revealed compounds 5n and 6p provided stronger π-π stacking interaction with residue Phe357 than 1,5-disubstituted 1,2,4-triazole 6d and Sitagliptin 1. In summary, compounds 5n and 6p could be promising lead compounds for further development of DPP-4 inhibitor.

Structural Identification between Phthalazine-1,4-Diones and N-Aminophthalimides via Vilsmeier Reaction: Nitrogen Cyclization and Tautomerization Study

N-Aminophthalimides and phthalazine 1,4-diones were synthesized from isobenzofuran-1,3-dione, isoindoline-1,3-dione, furo [3,4-b] pyrazine-5,7-dione, or 1H-pyrrolo [3,4-c] pyridine-1,3-dione with monohydrate hydrazine to carry out the 5-exo or 6-endo nitrogen cyclization under the different reaction conditions. Based on the control experimental results, 6-endo thermodynamic hydrohydrazination and kinetical 5-exo cyclization reactions were individually selective formation. Subsequently, Vilsmeier amidination derivatization was successfully developed to probe the structural divergence between N-aminophthalimide 2 and phthalazine 1,4-dione 3. On the other hand, the best tautomerization of N-aminophthalimide to diazinone was also determined under acetic acid mediated solution.

New methyl 5-(halomethyl)-1-aryl-1H-1,2,4-triazole-3-carboxylates as selective COX-2 inhibitors and anti-inflammatory agents: Design, synthesis, biological evaluation, and docking study

A new method was developed for synthesis of 1,2,4-triazole-3-carboxylates 5a-p and 6 from nitrilimines 3a-p through amination and heterocyclization two-steps reactions. All of 1,2,4-triazole-3-carboxylates 5 and 6 were characterized by spectroscopy technique. Based on the SAR study of anti-inflammation activity, most of these compounds showed potential anti-inflammatory activity on NO inhibition in LPS-induced RAW 264.7 cells (IC₅₀ < 7.0 µM) compared with Celecoxib and Indomethacin. Several potential compounds 5b-h, 5j, 5l, 5n, and 5o were subjected to in vitro cyclooxygenase COX-1/COX-2 inhibition assays. Compound 5d showed extraordinary COX-2 inhibition (IC₅₀ = 17.9 nM) and the best selectivity (COX-1/COX-2 = 1080). Furthermore, 5 mg/kg compound 5d exhibited better in vivo anti-inflammation and gastric protection results compared to 10 mg/kg Indomethacin. Docking experiments of 5d into COX-2 binding pocket have been evaluated. Following the bioactivities experimental data, the potential drug candidate 5d, significantly exhibited better anti-inflammatory effect than Indomethacin.