Potassium tert-Butoxide-Promoted Tandem Cyclization of Organoselenium Alkynyl Aryl Propargyl Ethers.

Base-promoted cyclization of 3-organoselenyl-methylene-2-alkynyl aryl propargyl ethers has been developed for the synthesis of 3-butylselanyl-methylene benzofurans, 3-methyl-2-alkynyl-benzofurans, and 4-iodo-benzo[b]furan-fused selenopyrans. Under potassium tert-butoxide as the base and tetrahydrofuran as the solvent, at room temperature, 3-organoselenyl-methylene-2-alkynyl aryl propargyl ethers were converted into 3-butylselanyl-methylene benzofurans via a 5-exo-dig mode. Using the same substrate, changing the solvent to dimethylsulfoxide, 3-methyl-2-alkynyl-benzofurans were selectively obtained in good yields. From 3-butylselanyl-methylene benzofurans, 4-iodo-benzo[b]furan-fused selenopyrans were prepared through a nucleophilic cyclization promoted by molecular iodine. The optimization of the reaction conditions showed that the solvents governed the regioselectivity of this cyclization and the initial formation of the dimsyl anion by the reaction of dimethylsulfoxide with potassium tert-butoxide was crucial for the 3-methyl-2-alkynyl-benzofuran preparation. We also proposed the mechanism for the formation of the products, demonstrated that the methodology can be scaled up, and showed the application of the prepared compounds as substrate in further transformations.

Development of a nanotechnological-based hydrogel containing a novel benzofuroazepine compound in association with vitamin E: An in vitro biological safety and photoprotective hydrogel.

This study aimed to evaluate the potential DNA photoprotection of nano-based hydrogels containing a novel benzofuroazepine molecule. Photoprotective property of three benzofuroazepine derivative compounds was assessed by determining a UV light absorptive profile. Nanocapsule suspensions (Eudragit® RS 100 as polymeric wall and medium-chain triglyceride or vitamin E as oil core) containing the benzofuroazepine compound that had the best UV spectral absorption were developed and physicochemically characterized. Photostability assay, bioadhesive property as well as preliminary toxicity parameters (HET-CAM and Artemia salina lethality assays) for free or nanoencapsulated forms were assessed. Among the molecules, the UV absorbance spectrum of free MBBA showed a broad and high intensity absorbance at UVB and UVA ranges. MBBA-nanocapsule suspensions had nanometric and homogeneous size distribution, bioadhesiveness property, and increased the UV light scattering in comparison to the free compound. Besides, all formulations triggered no irritative responses and the nanoencapsulation mitigated the toxic effect to Artemia salina observed to free MBBA. Following, hydrogels were prepared by thickening nanocapsule suspensions with gellan gum and their DNA photoprotection properties were determined by the exposure of DNA samples to the UVB and UVA radiation. Hydrogels showed acid pH values, compound content close to the theoretical value (3 mg/g), particle size in nanometric range, and spreadability profile suitable for cutaneous application. All MBBA hydrogels were effective against photoproducts formation induced by UVB and UVA radiation. In conclusion, these data show the identification of a compound with promising UV absorptive potential and the preparation of a final nano-based hydrogel for cutaneous application.