Photoinduced Three-Component Difluoroamidosulfonylation/Bicyclization: A Route to Dihydrobenzofuran Derivatives

A visible-light-induced photocatalyst-free three-component radical cascade bicyclization has been achieved to obtain diverse difluoroamidosulfonylated dihydrobenzofurans in moderate to good yields. This protocol avoids potential toxicity and the tedious removal procedure for photocatalysts and also features mild reaction conditions and a good functional group tolerance. Moreover, mechanistic investigations reveal the formation of a charge-transfer complex and the involvement of an intramolecular 1,5-hydrogen atom transfer process in this transformation.

Synthesis of Chiral Propargylamines, Chiral 1,2-Dihydronaphtho[2,1-b]furans and Naphtho[2,1-b]furans with C-Alkynyl N,N'-di-(tert-butoxycarbonyl)-aminals and β-Naphthols

Chiral phosphoric acid-catalyzed couplings of C-alkynyl N,N'-di-(tert-butoxycarbonyl)-aminals with β-naphthols led to chiral propargylamines in moderate to high yields with high to excellent enantioselectivity, in which the reactions underwent sequential chiral phosphoric acid-catalyzed in situ formation of N-(tert-butoxycarbonyl)-imines (N-Boc-imines) from the aminals, and 1,2-addition of β-naphthols to the N-Boc-imines. Chiral 1,2-dihydronaphtho[2,1-b]furans and naphtho[2,1-b]furans were prepared with satisfactory results when 10 mol% AgOAc and 20 mol% 2,6-lutidine or 1.2 equiv. of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) were added to the resulting chiral propargylamines solution, respectively.

Palladium-catalyzed asymmetric annulation between aryl iodides and racemic epoxides using a chiral norbornene cocatalyst

Herein, we describe our initial development of an asymmetric Pd-catalyzed annulation between aryl iodides and racemic epoxides for synthesis of 2,3-dihydrobenzofurans using a chiral norbornene cocatalyst. A series of enantiopure ester-, amide- and imide-substituted norbornenes have been prepared with a reliable synthetic route. Promising enantioselectivity (42-45% ee) has been observed using the isopropyl ester-substituted norbornene (N1*) and the amide-substituted norbornene (N7*).

Direct Annulation between Aryl Iodides and Epoxides through Palladium/Norbornene Cooperative Catalysis

Herein we report a direct annulation between aryl iodides and epoxides through palladium/norbornene (Pd/NBE) cooperative catalysis. An iso-propyl ester substituted NBE was found to be most efficient to suppress the formation of multiple-NBE-insertion byproducts and affords the desired 2,3-dihydrobenzofuran derivatives in 44-99 % yields. The reaction is scalable and tolerates a range of functional groups. Asymmetric synthesis is realized using an enantiopure epoxide. Application of this method into a concise synthesis of insecticide fufenozide is demonstrated.

Strategies for the Synthesis of 2,3-Dihydrobenzofurans

This article gives an overview of synthetic approaches to the 2,3-dihydrobenzofuran ring system with an emphasis on recently developed methods. The synthetic approaches are classified according to the key bond(s) formed during the construction of the dihydrobenzofuran skeleton, and approaches of relevance to the synthesis of natural products are highlighted.

Toxicological characterization of N-methyl-N-nitrosourea-induced cataract in rats by LC/MS-based metabonomic analysis

Cataract is one of the most serious drug-induced side effects that can terminate the development of drug candidates, and pharmaceutical companies consider it important to evaluate cataract-inducing potential in the early phases. Metabonomics is expected to be a powerful approach for the safety evaluation of drug candidates. In this study, we conducted a toxicological characterization of N-methyl-N-nitrosourea (MNU)-induced cataract in rats by LC/MS-based metabonomic analysis. MNU was intraperitoneally administered once to 15-day old rats at 70 mg kg(-1) . After that, animals were kept for 3 weeks waiting for cataract formation. Lens samples for metabonomic analysis were collected on 7, 14 and 21 days after MNU administration. Comprehensive analyses of lens metabolites were conducted using an LC/MS system, and multivariate data for each sample were compared by principal component analysis (PCA) to find any changes in lens metabolites. Lens opacity was confirmed by ophthalmoscopy 14 days after dosing, and even by gross observation 21 days after dosing. PCA of the lens samples for the control and MNU-treated groups revealed that the metabolite profiles of lens differed from each other, and several lens metabolites, such as lots of α-amino acids and gluthathione, decreased after MNU treatment. In conclusion, metabonomic analysis enabled us to identify new marker candidates for cataract and provided a better understanding of the mechanism related to MNU-induced cataract. It was considered that metabonomics is a useful approach for the characterization of drug-induced toxicity.

Synthesis, discovery and preliminary SAR study of benzofuran derivatives as angiogenesis inhibitors

A series of benzofuran derivatives were synthesized and evaluated against HUVEC proliferation. Among these compounds, compound 32 exhibited good inhibitory activity and remarkable selectivity to HUVEC. Our current data suggested that array order of methyl, acrylate and carboxylate groups in benzofuran scaffold is the basic requirement for inhibitory activity against HUVEC proliferation. These results demonstrated that benzofuran scaffold represents a promising structural core to discover a new class of active and selective angiogenesis inhibitors.