JACS Au最新文献

Propane dehydrogenation (PDH) is currently an approach for the production of propylene with high industrial importance, especially in the context of the shale gas revolution and the growing global demands for propylene and downstream commodity chemicals. In this Perspective article, we comprehensively summarize the recent advances in the design of advanced catalysts for PDH and the new understanding of the structure–performance relationship in supported metal catalysts. Furthermore, we discuss the gaps between fundamental research and practical industrial applications in the catalyst developments for the PDH process. In particular, we overview some critical issues regarding catalyst regeneration and the compatibility of the catalyst and reactor design. Finally, we make perspectives on the future directions of PDH research, including the efforts toward achieving a unified understanding of the structure–performance relationship, innovation in reactor engineering, and translation of the knowledge accumulated on PDH studies to other important alkane dehydrogenation reactions.

α-Heteroatom-substituted amides are useful as both targets and intermediates but are challenging to synthesize via conventional enolate chemistry. Herein, we describe a general and unified umpolung procedure to prepare α-heteroatom-functionalized secondary amides with various heteroatom-based nucleophiles under redox-neutral conditions. This transformation is a formal oxidation state reshuffle process from −N to −C in the hydroxamate, thereby achieving the umpolung α-heterofunctionalization of carbonyl groups without external oxidants. Regulated by the reshuffle mechanism, functionalization exclusively occurs at the α-position of the hydroxamate and precisely affords the α-functionalized amide with reliable predictability even in complex settings. Density functional theory studies support that soft enolization enabled by Mg²⁺/DIPEA combination is essential to facilitate the formation of the α-lactam intermediate. This represents the first general protocol to prepare α-functionalized secondary amides.

Ommatins, natural colorants found in cephalopods and arthropods, are biosynthesized from tryptophan with uncyclized xanthommatin (Uc-Xa) as the key biosynthetic precursor. These pigments change color under oxidative or reductive conditions. Xanthommatin (Xa) and dihydro-xanthommatin (H₂-Xa), as well as decarboxylated xanthommatin (Dc-Xa) and decarboxylated-dihydro-xanthommatin (Dc-H₂-Xa), are some of the most common and well-studied ommatins. Herein, we describe the biomimetic total synthesis of Xa/H₂-Xa on a gram scale by using the Mannich reaction and oxidative dimerization as the key steps. The 7-step linear synthetic sequence achieved an overall yield of 27%. Dc-Xa/Dc-H₂-Xa and protected Uc-Xa/Uc-H₂-Xa were also synthesized from the common intermediate-protected 3-hydroxykynurenine (3-OHK). The synthesized ommatins underwent thorough characterization using various spectroscopic techniques, including NMR, UV–vis, FTIR, HRMS, and LC–MS. Their optoelectronic properties were studied using spectrophotometry and electrochemical analysis. Furthermore, the antioxidant activity of the synthesized ommatins was evaluated using an oxygen radical antioxidant capacity activity assay. The results indicated that Dc-Xa exhibited the highest antioxidant activity, followed by Xa, while Uc-Xa showed the lowest activity.

The fleeting existence of aryl carbanion intermediates in the bulk phase prevents their direct observation and spectroscopic measurement. In sharp contrast, we report the direct interception of such unstable species at the air–water interface of microdroplets. We observed the transformation of three types of aryl acids (benzoic, phenylsulfinic, and phenylboronic acids) into phenyl carbanion (Ph^–) in water microdroplets, as examined by mass spectrometry. Experimental and theoretical evidence suggests that the high intrinsic electric field at the microdroplet surface is likely responsible for cleaving the respective acid functional groups of these substrates, generating Ph^–, which can subsequently be trapped by an electrophile, including a proton, to yield the corresponding ipso-substitution product. While catalyst-free decarboxylation at ambient temperature is challenging in the bulk phase, we report over 30% instantaneous conversion of benzoic acid to Ph^– in sprayed aqueous microdroplets in less than a millisecond. Thus, this study lays the foundation of a green chemical pathway for the aromatic electrophilic ipso-substitution reaction by spraying an aqueous solution of aryl acids, eliminating the need for any catalyst or reagent.

Cells are fundamental units of life. The coordination of cellular functions and behaviors relies on a cascade of molecular networks. Technologies that enable exploration and manipulation of specific molecular events in living cells with high spatiotemporal precision would be critical for pathological study, disease diagnosis, and treatment. Framework nucleic acids (FNAs) represent a novel class of nucleic acid materials characterized by their monodisperse and rigid nanostructure. Leveraging their exceptional programmability, convenient modification property, and predictable atomic-level architecture, FNAs have attracted significant attention in diverse cellular applications such as cell recognition, imaging, manipulation, and therapeutic interventions. In this perspective, we will discuss the utilization of FNAs in living cell systems while critically assessing the opportunities and challenges presented in this burgeoning field.

Snakebite envenoming claims 81–138 thousand lives annually, with vipers responsible for many of those. Phospholipase A₂ (PLA₂) enzymes and PLA₂-like proteins are among the most important viper venom toxins. The latter are particularly intriguing, as three decades after their discovery, their molecular mechanism of toxicity is still poorly understood at best. PLA₂-like proteins destabilize eukaryotic cell membranes through an unknown mechanism, causing an uncontrolled influx of Ca²⁺ ions and ultimately triggering cell death. It is now clear that the C-terminal segment is fundamental to the toxicity, as 13-mer peptides with the same sequence exhibit most or all of the activities of the complete PLA₂-like proteins. To finally clarify the mechanism of toxicity of these venom peptides, we have simulated their interaction with model cell membranes. Molecular dynamics simulations showed that peptides initially dispersed across the cell membrane quickly and spontaneously migrated, aggregated, induced membrane thinning, and formed clear and transient membrane pores. We calculated the potentials of the mean force for Ca²⁺ transfer across the cell membranes through the transient pores. The pores significantly lower the free energy barrier for Ca²⁺ translocation, an effect that grows with the size of the peptide aggregates and, thus, with the pore radius. Ca²⁺ flowed across the membrane through the largest pores with almost no barrier. The permeability of Ca²⁺ through the largest pores exceeded the permeability of pharmaceutical drugs by 4 orders of magnitude, revealing the easiness by which Ca²⁺ overflows the intracellular medium. These results elucidate the illusive molecular origin of the toxicity of this famous class of snake venom-derived peptides.

A continuous microfluidic glycosylation strategy that requires no chromatography between steps and significantly expedites glycosylation chemistry is described. This practical approach incorporates the advantages of imidazolium-based chromatography-free purification and in situ mass spectrometry reaction monitoring to achieve fast reaction optimization and shorter reaction times. We demonstrate the utility of this strategy in the synthesis of a series of glycoside targets, including an α-(1,6)-trimannoside and a branched Man₅ oligomannoside, within 1 day.

This study presents a bioinspired ion host featuring continuous binding sites arranged in a tunnel-like structure, closely resembling the selectivity filter of natural ion channels. Our investigation reveals that ions traverse these sites in a controlled, sequential manner due to the structural constraints, effectively mimicking the ion translocation process observed in natural channels. Unlike systems with open binding sites, our model facilitates sequential ion recognition state transitions, enabled by the deliberate design of the tunnel. Notably, we observe dual ion release kinetics, highlighting the system’s capacity to maintain ion balance in complex environments and adapt to changing conditions. Additionally, we demonstrate selective binding of two different ions─a challenging task for systems lacking structured tunnels.

In this report, we present a structurally and spectroscopically characterized diorganocopper system in three distinct oxidation states: [Cu^IICu^II] (1), [Cu^IICu^III] (2), and [Cu^IIICu^III] (3). These states are stabilized by a macrocyclic ligand scaffold featuring two square-planar coordination {C₂^NHCN₂^pyrazole}. We have analyzed the geometric and electronic structures using X-ray diffraction (XRD) and multiple spectroscopic methods including nuclear magnetic resonance (NMR), UV–vis, and electron paramagnetic resonance (EPR) spectroscopies, in combination with density functional theory (DFT) calculations. Remarkably, this study provides a structural determination of mixed-valence diorganocopper(II,III) complex 2, which is at the borderline between valence-trapped or charge-localized class I systems and charge moderately delocalized class II systems in Robin and Day classification. These findings enhance our understanding of the systematic structural and electronic changes that occur in diorganocopper complexes in response to redox transformations.