Novel 1,4-benzoxazine and 1,4-benzodioxine inhibitors of angiogenesis

Rational Design, Synthesis, and Anti-Proliferative Evaluation of Novel 4-Aryl-3,4-Dihydro-2H-1,4-Benzoxazines

A synthetic pathway to a novel 4-aryl-3,4-dihydro-2H-1,4-benzoxazine scaffold was developed and a series of compounds based on the scaffold were synthesised as potential anticancer agents. The 4-aryl-substituted compounds were prepared via Buchwald-Hartwig cross-coupling between substituted bromobenzenes and various 1,4-benzoxazines, which in turn were generated from a cascade hydrogenation and reductive amination one-pot reaction. These analogues exhibited moderate to good potency against various cancer cell lines. Structure-activity relationship analysis indicated that the inclusion of hydroxyl groups on ring A and ring B was beneficial to biological activity, while having a para-amino group on ring C significantly enhanced potency. Molecule 14f displayed the most potent anticancer activity (IC50 = 7.84-16.2 µM against PC-3, NHDF, MDA-MB-231, MIA PaCa-2, and U-87 MG cancer cell lines), indicating its potential as a lead compound for further structural optimisation. All the synthesised compounds were fully characterised with NMR, HMRS, and IR. The novel benzoxazine scaffold described in this study holds promise and deserves further in-depth studies.

Multigram-scale HPLC enantioseparation as a rescue pathway for circumventing racemization problem during enantioselective synthesis of ethyl 3,4-dihydro-2H-1,4-benzoxazine-2-carboxylate

Racemic ethyl 3,4-dihydro-2H-1,4-benzoxazine-2-carboxylate is a key synthon for the design of promising therapeutic drugs. It is mainly synthesized from racemic ethyl 2,3-dibromopropionate and 2-aminophenol in presence of K₂ CO₃ in refluxed acetone. Unfortunately, synthesis of (R)- and (S)-enantiomers using the enantioselective version of this reaction, which should normally be performed with a double S_N 2 mechanism, is unsuitable due to a racemization process involving the dehydrobromination of enantiopure ethyl 2,3-dibromopropionate into ethyl 2-bromoacrylate. For the first time, the enantioselective version is studied (ee ≈ 55-66%), and the percentage of racemization process has estimated to around 34-46% after determination of the optimal experimental conditions for analytical HPLC enantioseparation of racemate. The influence of the experimental and purification conditions on the racemization rate is also studied. The results indicate that racemization occurs faster at the beginning of the reaction but the initiation of the double S_N 2 process takes place more faster to limit the racemization rate. The study of the influence of experimental conditions (reaction times, temperature, solvent or type of base, etc.) on the degree of racemization of the (R)- enantiomer is performed and shows that despite changes in the experimental conditions, the synthesis of the (R)- enantiomer is always accompanied by a racemization rate which is difficult in reducing. In parallel, (R)- and (S)-enantiomers are obtained in high enantiopurity (ee > 99.5%) by preparative HPLC enantioseparation of racemate on multigram scale and characterized by optical rotation measurements, ECD and UV spectra.

Synthesis, in vitro COX-1/COX-2 inhibition testing and molecular docking study of novel 1,4-benzoxazine derivatives

The present work deals with an efficient and straightforward synthesis, biological activity and molecular docking study of novel 1,4-benzoxazine derivatives.

Novel colchicine-site binders with a cyclohexanedione scaffold identified through a ligand-based virtual screening approach

Vascular disrupting agents (VDAs) constitute an innovative anticancer therapy that targets the tumor endothelium, leading to tumor necrosis. Our approach for the identification of new VDAs has relied on a ligand 3-D shape similarity virtual screening (VS) approach using the ROCS program as the VS tool and as query colchicine and TN-16, which both bind the α,β-tubulin dimer. One of the hits identified, using TN-16 as query, has been explored by the synthesis of its structural analogues, leading to 2-(1-((2-methoxyphenyl)amino)ethylidene)-5-phenylcyclohexane-1,3-dione (compound 16c) with an IC50 = 0.09 ± 0.01 μM in HMEC-1 and BAEC, being 100-fold more potent than the initial hit. Compound 16c caused cell cycle arrest in the G2/M phase and interacted with the colchicine-binding site in tubulin, as confirmed by a competition assay with N,N'-ethylenebis(iodoacetamide) and by fluorescence spectroscopy. Moreover, 16c destroyed an established endothelial tubular network at 1 μM and inhibited the migration and invasion of human breast carcinoma cells at 0.4 μM. In conclusion, our approach has led to a new chemotype of promising antiproliferative compounds with antimitotic and potential VDA properties.