Tetrahedron Letters最新文献

Schweinfurthin G, one of the most potent of the schweinfurthins containing a hexahydroxanthene moiety, was found to exhibit strong cytotoxicity against A549 and KB cell lines with the IC₅₀ values of 0.8 μM and 0.6 μM, respectively. In this paper, a new series of schweinfurthin G derivatives modified on the isoprenyl side-chain were synthesized from schweinfurthin G using multicomponent reactions. The cytotoxicity of all the synthetic compounds was evaluated against four human cancer cell lines (KB, Hep3B, A549, MCF7) and one non-cancerous cell line (HEK293), which enabled to perform in-depth structure–activity relationships on a still poorly explored part of the molecule.

Organic molecules containing 1,2-diphosphonate moiety are of great value in organic synthesis. Diphosphoryl acetylenes (or named as ethyne-1,2-diyldiphosphonates) are a class of molecules utilized for synthesis of diverse phosphorus compounds applicable in multiple fields. However, present stoichiometric methods for the preparation of diphosphoryl acetylenes generally requires multiple steps or harsh conditions. Herein, we report a facile synthesis of diphosphoryl acetylenes, in which the readily available ethynyl phosphonates couple with dialkyl phosphonates through cheap copper catalysis. A series of diphosphoryl acetylenes in symmetric or unsymmetric fashions are facilely prepared. This protocol demonstrates advantages of mild reaction conditions, inert atmosphere-free, cheap catalyst, base-free, and high efficiency to serve as a practical method for synthesis of diphosphoryl acetylenes.

Three new pimarane diterpenoids, plectalibertellenones A−C (1–3), along with six known compounds, 9α-hydroxy-1,8(14),15-isopimaratrien-3,7,11-trione (4), 9α-hydroxy-1,8(14),15-isopimaratrien-3,11-dione (5), phomenone B (6), (−)-pestalotin (7), (+)-pestalotin (8), and 6-pentyl-4-methoxy-pyran-2-one (9) were isolated from the crude extract of an endolichenic fungus, Pseudoplectania sp. EL000327. The planar structures of metabolites 1–3 were elucidated using UV, mass spectrometry (MS), and nuclear magnetic resonance (NMR) spectroscopic data. The relative and absolute configurations of 1–3 were deduced from an interpretation of circular dichroism (CD) spectroscopic data, application of an advanced Mosher’s method, DP4⁺ calculations, and combination of NMR spectroscopic methods. Compounds 1–9 did not display any significant anti-bacterial activity; however, compounds 1–4 were cytotoxic to Caco2 cells, with IC₅₀ values 54.8, 80.7, 76.4, and 19.6 µM, respectively.

I₂/CAN has emerged as a powerful and efficient oxidizing agent for direct tertiary CH oxidation of 3,3′-(phenyl methylene) bis(N-methyl-7-azaindole) under mild conditions to form bis(N-methyl-7-azaindol-3-yl) (phenyl)methanol in quantitative yield. Further, based on control experiments, a plausible mechanism and characterization of products including XRD are described. Synthetic transformation for bis(N-methyl-7-azaindol-3-yl) (phenyl) methanol is achieved by thionation.

An efficient one-pot approach to access functionalized 3,4-dihydro-[1,3]oxazin-2-one skeletons has been developed through BF₃·Et₂O-mediated addition-cyclization of ynamides and N-Boc phenylsulfones. The metal-free catalytic method exhibits good functional group compatibility. This study provides a practical new method for the synthesis of oxazinone skeletons.

Chiral sulfinamides have emerged as versatile tools in various asymmetric reactions, especially in the generation of chiral amines through asymmetric CC bond formation reactions involving chiral sulfinyl imines derived from sulfinamides and aldehyde or ketones. The prospect of employing sulfinamide auxiliaries in stereoselective carbon–heteroatom bond formation reactions has received considerable attention. This review examines recent advancements in stereoselective reactions involving chiral sulfinamide reagents, focusing on CN, CO, and CS bond formation reactions. The article elucidates the mechanisms and stereocontrol aspects underlying these asymmetric reactions, highlighting their utility in the synthesis of bioactive compounds.

Presented herein is an effective synthesis of branched and linear allyl arenes based on the reactions of 2-aryl-3H-indoles with 5-methylene-1,3-dioxan-2-one or 4-vinyl-1,3-dioxolan-2-one. Mechanistically, the reactions are initiated by Rh(III)-catalyzed aryl C(sp²)–H bond activation/cyclometallation followed by vinyl coordination/migratory insertion and β–O elimination through release of CO₂ as the only by-product. By using this newly developed protocol, a group of 2-aryl-3H-indole derivatives bearing the substructure of either branched or linear allylic alcohol were obtained in good efficiency. Notably, the linear allylic alcohols were obtained with excellent E/Z selectivity when unsubstituted vinyl-1,3-dioxolan-2-one was used as the allyl surrogate. With advantages such as easily available starting materials, mild and redox-neutral reaction conditions, good compatibility with a broad range of functional groups, benign solvent and divergent products, this protocol is expected to be used in the synthesis of indole-based functional molecules.

Herein, we report a mild palladium-catalyzed decarboxylative allylic alkylation of allyl ester-substituted isoindolinone substrates to afford a variety of 3,3-disubstituted isoindolinone derivatives. The decarboxylative coupling reaction tolerates a range of functional groups, including ketones and alkenyl halides, and does not require protection of the isoindolinone nitrogen. Additionally, the reaction was found to proceed in near-quantitative yield for most substrates evaluated. Based on the isolation of competing cyclopropane and protonation products, a reaction mechanism is proposed.

A Brønsted acid catalyzed alkylation method for 1,2,3-triazoles is described using trichloroacetimidates as the electrophiles. These conditions were selective, with a strong preference of N2 alkylation product, often in high yield. The ratio of N2:N1 alkylation is sensitive to both the type of solvent used and the reaction concentration. The optimal results were obtained with a non-polar solvent at higher dilutions. Both 1,2,3-triazoles and 1,2,3-benzotriazoles could be alkylated under these conditions, providing access to N2 substituted 1,2,3-triazoles in good yields.

A palladium-catalyzed intramolecular cyclization borylmethylation of alkene-tethered aryl iodide with 1,1-diborylmethane has been described. This method offers an efficient route to synthesize various benzo-heterocyclic compounds containing oxygen or nitrogen atoms. Further experiments have demonstrated that the products can be employed to synthesize a series of potentially biological active heterocyclic compounds.