Endoplasmic Reticulum-Targeting Quinazolinone-Based Lipophilic Probe for Specific Photoinduced Ferroptosis and Its Induced Lipid Dynamic Regulation

Lethal lipid peroxidation caused by reactive oxygen species occurs in different types of programmed cell death, especially in ferroptosis. Ferroptosis inducers, which serve as small-molecule probes, can provide insight into the mechanism of ferroptosis and facilitate drug discovery. The classical ferroptosis inducers indirectly lead to lipid peroxidation; thus, it is difficult to explore lipid regulation during the ferroptotic process. In this study, we designed two quinazolinone-based lipophilic probes BODIQPy-TPA and QPy-TPA, which proved to directly induce lipid peroxidation by light irradiation in vitro. The probe BODIQPy-TPA, which was mainly distributed in the endoplasmic reticulum (ER), specifically triggered ferroptosis in B16 and HepG2 cells upon light irradiation. As a comparison, the probe QPy-TPA, which was mainly distributed in lipid droplets (LDs), induced cell death by a nonferroptotic pathway. Further lipidomic analysis revealed that these two probes caused different patterns of lipid regulation and lipid peroxidation, suggesting that ferroptosis might activate distinct lipid regulation.

Facile preparation of optically active helical polycarbenes with salicylate substituents and their postpolymerization modification

Optically active helical polycarbenes were constructed through the living and controlled helix-sense-selective polymerization (HSSP) of methyl salicylate modified diazoacetate monomer catalysed via π-allylPdCl with chiral phosphine ligands. The obtained helical polycarbenes could undergo postpolymerization modification to afford functional polycarbenes efficiently.

Accurate identification of radicals by in-situ electron paramagnetic resonance in ultraviolet-based homogenous advanced oxidation processes

Accurate identification of radicals in advanced oxidation processes (AOPs) is important to study the mechanisms on radical production and subsequent oxidation-reduction reaction. The commonly applied radical quenching experiments cannot provide direct evidences on generation and evolution of radicals in AOPs, while electron paramagnetic resonance (EPR) is a cutting-edge technology to identify radicals based on spectral characteristics. However, the complexity of EPR spectrum brings uncertainty and inconsistency to radical identification and mechanism clarification. This work presented a comprehensive study on identification of radicals by in-situ EPR analysis in four typical UV-based homogenous AOPs, including UV/H₂O₂, UV/peroxodisulfate (and peroxymonosulfate), UV/peracetic acid and UV/IO₄^- systems. Radical formation mechanism was also clarified based on EPR results. A reliable EPR method using organic solvents was proposed to identify alkoxy and alkyl radicals (CH₃C(=O)OO·, CH₃C(=O)O· and ·CH₃) in UV/PAA system. Two activation pathways for radical production were proposed in UV/IO₄^- system, in which the produced IO₃·, IO₄·, ·OH and hydrated electron were precisely detected. It is interesting that addition of specific organic solvents can effectively identify oxygen-center and carbon-center radicals. A key parameter in EPR spectrum for 5,5-dimethyl-1-pyrroline N-oxide (DMPO) spin adduct, A_H, is ranked as: ·CH₃ (23 G) >·OH (15 G) >IO₃· (12.9 G) >O₂·^- (11 G) ≥·OOH (9-11 G) ≥IO₄· (9-10 G) ≥SO₄·^- (9-10 G) >CH₃C(=O)OO· (8.5 G) > CH₃C(=O)O· (7.5 G). This study will give a systematic method on identification of radicals in AOPs, and shed light on the insightful understanding of radical production mechanism.

Synthesis of 8-Alkoxy-5H-isochromeno[3,4-c]isoquinolines and 1-Alkoxy-4-arylisoquinolin-3-ols through Rh(III)-Catalyzed C-H Functionalization of Benzimidates with 4-Diazoisochroman-3-imines and 4-Diazoisoquinolin-3-ones

Rh(III)-catalyzed C-H activation/annulation of benzimidates with 4-diazoisochroman-3-imines furnished 8-alkoxy-5H-isochromeno[3,4-c]isoquinolines in moderate to excellent yields with a broad range of substrate scope. The reaction was carried out under mild reaction conditions and could be scaled up with practical usage. Similar reaction between benzimidates and 4-diazoisoquinolin-3-ones provided 1-alkoxy-4-arylisoquinolin-3-ols in excellent yields. Moreover, the synthesized products could be conveniently transformed to the corresponding heterocycles with a 1,8-naphthyridinone or isochromenopyridinone core, which are privileged structures in medicinal chemistry.

Cyclopropanations via Heme Carbenes: Basic Mechanism and Effects of Carbene Substituent, Protein Axial Ligand, and Porphyrin Substitution

Catalytic carbene transfer to olefins is a useful approach to synthesize cyclopropanes, which are key structural motifs in many drugs and biologically active natural products. While catalytic methods for olefin cyclopropanation have largely relied on rare transition-metal-based catalysts, recent studies have demonstrated the promise and synthetic value of iron-based heme-containing proteins for promoting these reactions with excellent catalytic activity and selectivity. Despite this progress, the mechanism of iron-porphyrin and hemoprotein-catalyzed olefin cyclopropanation has remained largely unknown. Using a combination of quantum chemical calculations and experimental mechanistic analyses, the present study shows for the first time that the increasingly useful C=C functionalizations mediated by heme carbenes feature an Fe^II-based, nonradical, concerted nonsynchronous mechanism, with early transition state character. This mechanism differs from the Fe^IV-based, radical, stepwise mechanism of heme-dependent monooxygenases. Furthermore, the effects of the carbene substituent, metal coordinating axial ligand, and porphyrin substituent on the reactivity of the heme carbenes was systematically investigated, providing a basis for explaining experimental reactivity results and defining strategies for future catalyst development. Our results especially suggest the potential value of electron-deficient porphyrin ligands for increasing the electrophilicity and thus the reactivity of the heme carbene. Metal-free reactions were also studied to reveal temperature and carbene substituent effects on catalytic vs noncatalytic reactions. This study sheds new light into the mechanism of iron-porphyrin and hemoprotein-catalyzed cyclopropanation reactions and it is expected to facilitate future efforts toward sustainable carbene transfer catalysis using these systems.

Wavelength-focusing organic molecular materials with diazoacetate or fumarate as a monofluorophore

Wavelength-focusing molecular materials can focus the shorter and longer wavelengths of simulated solar radiation into an identical wavelength in between.

Mechanistic studies of the copolymerization between ethyl diazoacetate and cinnamaldehyde

N^diazo,C^ω-diradical species and their chain propagation mechanism during copolymerization.

Computation Sheds Insight into Iron Porphyrin Carbenes' Electronic Structure, Formation, and N-H Insertion Reactivity

Iron porphyrin carbenes constitute a new frontier of species with considerable synthetic potential. Exquisitely engineered myoglobin and cytochrome P450 enzymes can generate these complexes and facilitate the transformations they mediate. The current work harnesses density functional theoretical methods to provide insight into the electronic structure, formation, and N-H insertion reactivity of an iron porphyrin carbene, [Fe(Por)(SCH3)(CHCO2Et)](-), a model of a complex believed to exist in an experimentally studied artificial metalloenzyme. The ground state electronic structure of the terminal form of this complex is an open-shell singlet, with two antiferromagnetically coupled electrons residing on the iron center and carbene ligand. As we shall reveal, the bonding properties of [Fe(Por)(SCH3)(CHCO2Et)](-) are remarkably analogous to those of ferric heme superoxide complexes. The carbene forms by dinitrogen loss from ethyl diazoacetate. This reaction occurs preferentially through an open-shell singlet transition state: iron donates electron density to weaken the C-N bond undergoing cleavage. Once formed, the iron porphyrin carbene accomplishes N-H insertion via nucleophilic attack. The resulting ylide then rearranges, using an internal carbonyl base, to form an enol that leads to the product. The findings rationalize experimentally observed reactivity trends reported in artificial metalloenzymes employing iron porphyrin carbenes. Furthermore, these results suggest a possible expansion of enzymatic substrate scope, to include aliphatic amines. Thus, this work, among the first several computational explorations of these species, contributes insights and predictions to the surging interest in iron porphyrin carbenes and their synthetic potential.

A Cu-catalyzed four-component cascade reaction to construct β-ester-γ-amino ketones

Herein, a novel Cu-catalyzed four-component cascade reaction, which encompasses styrenes, diazo reagents, amines, and tert-butyl hydroperoxide (TBHP), was well developed toward β-ester-γ-amino ketones, which showed high chemoselectivity.

A high quantum yield two-way conversion luminescent oligomer: 1,4-butanediol-bis(5-carbonyl-3-carbethoxy-2-pyrazoline)

Oligomers as fluorescent macromolecules exhibit excellent efficiency of a two-way conversion fluorescence process which makes them potentially attractive for biological applications.

Cu-based carbene involved in a radical process: a new crossover reaction to construct γ-peroxy esters and 1,4-dicarbonyl compounds

Herein, a novel crossover reaction of Cu-based carbene, olefin, and tert-butyl hydroperoxide (TBHP) was well developed, leading to γ-peroxy esters and 1,4-dicarbonyl compounds.