Monthly Archives: March 2024

Novel Ruthenium‐based Nitrosyl Complexes: NO Donation and Vasorelaxant Potentials for Cardiovascular Therapeutics

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Novel Ruthenium-based Nitrosyl Complexes: NO Donation and Vasorelaxant Potentials for Cardiovascular Therapeutics

Nitrosyl Ruthenium compounds are promising platforms for nitric oxide (NO) delivery. A novel nitrosyl ruthenium complex containing the ligand 2-methylimidazole was synthetized and characterized through spectroscopic techniques, including X-ray Absorption Spectroscopy (XAS). That compound showed promising NO releasing capabilities and promoted vasodilation together with free radical scavenging. Such properties are desirable for the treatments of cardiovascular diseases, such as atherosclerosis.


Abstract

Nitrosyl ruthenium complexes have emerged as promising platforms for the controlled delivery of nitric oxide (NO) and nitroxyl (HNO), both of which possess significant therapeutic implications. Considering this scenario, we synthesized and characterized the metal complex cis-[RuNO(phen)2(2MIM)]3+ and its precursors, where phen and 2MIM correspond to 1,10-phenantroline and 2-methylimidazole, respectively. Comprehensive structural elucidation was undertaken using a combination of spectroscopic and electrochemical methodologies, including XANES/EXAFS experiments. This structural data was further validated through DFT computational analyses. We demonstrated that such compound can release NO and HNO in the presence of thiol-based substrates. Not only this, but the same metal complex can also delivery nitric oxide under irradiation with visible light (λ=460 nm). The nitrosyl complex and its derivatives displayed marked vasodilatory capabilities as evidenced in assays involving isolated rat aorta rings. They also exhibited commendable antioxidant activity in free radical scavenging assays. Collectively, based on these data, this nitrosyl ruthenium compound is a potential therapeutic candidate, especially in the field of cardiovascular pathology like atherosclerosis, thereby deserving further in-depth investigations.

CuI/DMAP‐Catalyzed Oxidative Alkynylation of 7‐Azaindoles: Synthetic Scope and Mechanistic Studies

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CuI/DMAP-Catalyzed Oxidative Alkynylation of 7-Azaindoles: Synthetic Scope and Mechanistic Studies

Using a new CuI/DMAP catalytic system, oxidative N-alkynylation of 7-azaindole has been discussed. A detailed mechanistic study has been performed based on the reactive intermediate [CuII(DMAP)2I2], supported by both DFT calculations and UV-visible spectroscopy. Further several 7-azaindole decorated 1,4 and 1,5 disubstituted 1,2,3-triazole derivatives has been synthesized via click chemistry.


Abstract

An efficient and practical method for the N-alkynylation of 7-azaindoles has been established by using CuI/DMAP catalytic system at room temperature and in open air. This simple protocol has been successfully employed in the synthesis of a wide range of N-alkynylated 7-azaindoles with good yields. Also, this approach is well-suited for large-scale N-alkynylation reactions. The designed N-alkynylated 7-azaindoles were further subjected to Cu-/Ir-catalyzed alkyne–azide cycloaddition (CuAAC/IrAAC) or “click” reaction for the rapid synthesis of 1,4-/1,5 disubstituted 1,2,3-triazole decorated 7-azaindoles. A mechanistic study based on density functional theory (DFT) calculations and ultraviolet–visible (UV) spectroscopic studies revealed that the CuI and DMAP combination formed a [CuII(DMAP)2I2] species, which acts as an active catalyst. The DFT method was used to assess the energetic viability of an organometallic in the C−N bond formation pathway originating from the [CuII(DMAP)2I2] complex. We expect that the newly designed Cu/DMAP/alkyne system will offer valuable insights into the field of Cu-catalyzed transformations.

Direct Through‐Space Substituent‐π Interactions in Noncovalent Arene–Fullerene Assemblies

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Direct Through-Space Substituent-π Interactions in Noncovalent Arene–Fullerene Assemblies

The substituents effects in arene-fullerene interactions were examined by NMR titration experiments using an open-[60]fullerene as a host, revealing self-assembling behavior with substituted benzenes by a 1 : 2 stoichiometry. The destabilization of the OMe-substitution clearly indicates the presence of direct through-space substituent-π interactions describable by the Wheeler-Houk model.


Abstract

The arene-arene interactions between electron-rich and deficient aromatics have been less understood. Herein, we focus on a [60]fullerene π-surface as an electron-deficient aromatics. Using a 1H signal of H2O@C60 as a magnetic probe, the presence of benzene–fullerene interactions was confirmed. To investigate substituent effects on the noncovalent arene-fullerene interactions, NMR titration experiments were carried out using an open-[60]fullerene and a series of substituted benzenes, i. e., PhX (X=NO2, CN, Cl, OMe, H, CH3, and NH2), demonstrating a 1 : 2 stoichiometry with a positive correlation between stabilization energies upon the first association (ΔG 1) and Hammet constants (σ m). The destabilization of the self-assembled structure for X=OMe with a σ-withdrawing nature clearly showed direct through-space substituent-π interactions describable by the Wheeler-Houk model while the second association was suggested to be considerably perturbed by the secondary effects.

Reduced 2,2’‐Bipyridine Lanthanide Metallocenes Provide Access to Mono‐C5Me5 and Polyazide Complexes

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Reduced 2,2’-Bipyridine Lanthanide Metallocenes Provide Access to Mono-C5Me5 and Polyazide Complexes

Exploration of the multielectron reduction chemistry of the lanthanide complexes Cp*2LnCl(bipy), Cp*2Ln(bipy), and [Cp*2Ln(bipy)]1− highlights the unusual reactivity available from this redox-active platform. A variety of unusual polysulfide, polyazide, and mixed-valence complexes are accessible, many of which are formed through the loss of a Cp* ligand and the generation of mono-Cp* complexes.


Abstract

Exploration of the reduction chemistry of the 2,2’-bipyridine (bipy) lanthanide metallocene complexes Cp*2LnCl(bipy) and Cp*2Ln(bipy) (Cp* = C5Me5) resulted in the isolation of a series of complexes with unusual composition and structure including complexes with a single Cp* ligand, multiple azide ligands, and bipy ligands with close parallel orientations. These results not only reveal new structural types, but they also show the diverse chemistry displayed by this redox-active platform. Treatment of Cp*2NdCl(bipy) with excess KC8 resulted in the formation of the mono-Cp* Nd(III) complex, [K(crypt)]2[Cp*Nd(bipy)2], 1, as well as [K(crypt)][Cp*2NdCl2], 2, and the previously reported [K(crypt)][Cp*2Nd(bipy)]. A mono-Cp* Lu(III) complex, Cp*Lu(bipy)2, 3, was also found in an attempt to make Cp*2Lu(bipy) from LuCl3, 2 equiv. of KCp*, bipy, and K/KI. Surprisingly, the (bipy)1− ligands in neighboring molecules in the structure of 3 are oriented in a parallel fashion with intermolecular C⋅⋅⋅C distances of 3.289(4) Å, which are shorter than the sum of van der Waals radii of two carbon atoms, 3.4 Å. Another product with one Cp* ligand per lanthanide was isolated from the reaction of [K(crypt)][Cp*2Eu(bipy)] with azobenzene, which afforded the dimeric Eu(II) complex, [K(crypt)]2[Cp*Eu(THF)(PhNNPh)]2, 4. Attempts to make 4 from the reaction between Cp*2Eu(THF)2 and a reduced azobenzene anion generated instead the mixed-valent Eu(III)/Eu(II) complex, [K(crypt)][Cp*Eu(THF)(PhNNPh)]2, 5, which allows direct comparison with the bimetallic Eu(II) complex 4. Mono-Cp* complexes of Yb(III) are obtained from reactions of the Yb(II) complex, [K(crypt)][Cp*2Yb(bipy)], with trimethylsilylazide, which afforded the tetra-azido [K(crypt)]2[Cp*Yb(N3)4], 6, or the di-azido complex [K(crypt)]2[Cp*Yb(N3)2(bipy)], 7 a, depending on the reaction stoichiometry. A mono-Cp* Yb(III) complex is also isolated from reaction of [K(crypt)][Cp*2Yb(bipy)] with elemental sulfur which forms the mixed polysulfido Yb(III) complex [K(crypt)]2[Cp*Yb(S4)(S5)], 8 a. In contrast to these reactions that form mono-Cp* products, reduction of Cp*2Yb(bipy) with 1 equiv. of KC8 in the presence of 18-crown-6 resulted in the complete loss of Cp* ligands and the formation of [K(18-c-6)(THF)][Yb(bipy)4], 9. The (bipy)1− ligands of 9 are arranged in a parallel orientation, as observed in the structure of 3, except in this case this interaction is intramolecular and involves pairs of ligands bound to the same Yb atom. Attempts to reduce further the Sm(II) (bipy)1− complex, Cp*2Sm(bipy) with 2 equiv. of KC8 in the presence of excess 18-crown-6 led to the isolation of a Sm(III) salt of (bipy)2− with an inverse sandwich Cp* counter-cation and a co-crystallized K(18-c-6)Cp* unit, [K2(18-c-6)2Cp*]2[Cp*2Sm(bipy)]2 ⋅ [K(18-c-6)Cp*], 10.

Recent Advances of Chiral Small Organic Molecules: Structure and Properties for Circularly Polarized Luminescence

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Circularly polarized luminescence (CPL) refers to the emission of light with distinguishable left or right circular polarization in non-racemic systems. CPL has attracted significant attention due to its potential applications in future displays, photonics technologiesIn recent years, there has been significant development in the field of circularly polarized luminescent (CPL) materials based on small organic molecules, attributed to their precise and tunable molecular structures and high luminescent efficiency. With the continuous investigation of chiral molecular frameworks and molecular derivatization, the performance of CPL small molecules has been comprehensively promoted. We herein provide a detailed discussion on commonly studied CPL chiral frameworks of small molecules, including axially chiral binaphthyls, axially chiral biphenyls, chiral helicenes, planar chiral cyclophanes, spirocycles, metal-centered chirality, and point chirality, aiming at providing readers with the basic understanding and research status about CPL as well as inspiration for future development.

Total Synthesis and Stereochemical Assignment of Talaroconvolutin A and Talarofuranone: Gram‐scale Synthesis of Ferroptosis Inducer Talaroconvolutin A

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Total Synthesis and Stereochemical Assignment of Talaroconvolutin A and Talarofuranone: Gram-scale Synthesis of Ferroptosis Inducer Talaroconvolutin A

The first scalable total synthesis and stereochemical assignment of talaroconvolutin A and talarofuranone are presented.


Comprehensive Summary

The first total synthesis of talaroconvolutin A (1.1 g obtained) and talarofuranone has been achieved using accessible materials (12 steps, 7.5% and 8.2% yields, respectively). Convergent routes involved intramolecular Diels−Alder reactions in two approaches for creating the decalin moiety. Additionally, an unprecedented DMP-mediated domino reaction resulted in the deoxy-tetramic acid system. These syntheses not only establish the absolute configuration of talaroconvolutin A but also enable further collaborative studies of this type of ferroptosis inducers.

Feasible Synthesis of N,O‐Bidentate Difluoroboron Chromophores through Direct Functionalization of Quinoxalin‐2(1H)‐ones with Ketones in One Shot

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Feasible Synthesis of N,O-Bidentate Difluoroboron Chromophores through Direct Functionalization of Quinoxalin-2(1H)-ones with Ketones in One Shot

A rapid synthetic protocol for N,O-bidentate difluoroboron chromophores was achieved via cascade C—H functionalization and difluoroboronation reaction from readily accessible feedstock chemicals in one shot.


Comprehensive Summary

Organic difluoroboron complexes are a kind of potential platforms for a wide range of applications owing to their excellent photophysical properties. Herein, we have explored a simple and direct synthesis methodology for a library of N,O-bidentate difluoroboron complexes from quinoxalin-2(1H)-ones and ketones in one shot. The photophysical properties of the generated complexes were evaluated and the application potential of these compounds on subcellular imaging was also explored.

Artemordins A—S, Cadinane‐Type Sesquiterpenoid Dimers from Artemisia ordosica and Their Antihepatoma Activities

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Artemordins A—S, Cadinane-Type Sesquiterpenoid Dimers from Artemisia ordosica and Their Antihepatoma Activities

Nineteen new cadinane-involving sesquiterpenoid dimer, artemordins A—S (1—19) were isolated from Artemisia ordosica. Notably, artemordins A—F (1—6) were the first examples of two cadinane units connected by unprecedented C—C single bond with an oxido-rearranged 6/5/6/6 fused ring system; artemordins G—J (7—10) were biogenetically formed by [4 + 2] cycloaddition and possessed a novel 5/6/6/6/6/6/5—heptacyclic fused ring system. Artemordins B and H (2 and 8) exhibited inhibitory activities on three hepatoma cell lines with IC50 values of 26.9 and 25.1 μmol/L (HepG2), 29.5 and 18.3 μmol/L (Huh7), 19.7 and 15.7 μmol/L (SK-Hep-1).


Comprehensive Summary

Nineteen new cadinane-involving sesquiterpenoid dimers, artemordins A—S (1—19), together with 13 known SDs (20—32) were isolated from Artemisia ordosica. Their structures and absolute configurations were established by comprehensive spectral analyses, X-ray single crystal diffraction, theoretical ECD, and NMR calculations. Chemically, artemordins A—F (1—6) were the first examples of two cadinane units constructed by unprecedented C-3−C-15′ or C-3−C-13′ single bond with an oxido-rearranged 6/5/6/6 fused ring system; artemordins G—K (7—11) were biogenetically connected by [4 + 2] cycloaddition reaction and artemordins G—J (7—10) possessed a novel 5/6/6/6/6/6/5-heptacyclic fused ring system. Artemordins L—S (12—19) were formed by esterification, which involved three different types of sesquiterpenoids. Antihepatoma assay suggested that the most active compounds, artemordins B and H (2 and 8), exhibited inhibitory activities on three hepatoma cell lines with IC50 values of 26.9 and 25.1 μmol/L (HepG2), 29.5 and 18.3 μmol/L (Huh7), 19.7 and 15.7 μmol/L (SK-Hep-1).

Vicinal Diones and α‐Keto Esters as Electrophiles of Aldolases for Stereoselective Construction of Tertiary Alcohols

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Aldolases are powerful C−C bond-forming enzymes with high stereoselectivity and broad substrate scope in biocatalysis, but their ability to stereoselectively construct tertiary alcohols has not been fully explored. Herein, we demonstrate that vicinal diones and α-keto esters are electrophiles that can be accepted by both natural and computationally designed aldolases via various catalytic mechanisms. This method allows for the efficient asymmetric synthesis of small molecules with tertiary alcohols, including noncanonical amino acids. This study presents the first types of generic nonnatural substrates of aldolases and reveals new opportunities for the use of aldolases in the synthesis of versatile chiral synthons.