In contrast to the wealth of asymmetric transformations for generating central chirality from alkyl radicals, the enantiocontrol over the allenyl radicals for forging axial chirality represents an ...uncharted domain. The challenge arises from the unique elongated linear configuration of the allenyl radicals that necessitates the stereo‐differentiation of remote motifs away from the radical reaction site. We herein describe a copper‐catalyzed asymmetric radical 1,4‐carboalkynylation of 1,3‐enynes via the coupling of allenyl radicals with terminal alkynes, providing diverse synthetically challenging tetrasubstituted chiral allenes. A chiral N,N,P‐ligand is crucial for both the reaction initiation and the enantiocontrol over the highly reactive allenyl radicals. The reaction features a broad substrate scope, covering a variety of (hetero)aryl and alkyl alkynes and 1,3‐enynes as well as radical precursors with excellent functional group tolerance.
A copper‐catalyzed asymmetric radical 1,4‐carboalkynylation of 1,3‐enynes is realized, providing diverse tetrasubstituted chiral allenes. The utilization of the copper/chiral N,N,P‐ligand is crucial for the enantiocontrol over the allenyl radicals, which is difficult due to their elongated linear configuration that necessitates the stereo‐differentiation of remote motifs away from the reaction site.
Fe/N/C is a promising non‐Pt electrocatalyst for the oxygen reduction reaction (ORR), but its catalytic activity is considerably inferior to that of Pt in acidic medium, the environment of polymer ...electrolyte membrane fuel cells (PEMFCs). An improved Fe/N/C catalyst (denoted as Fe/N/C‐SCN) derived from Fe(SCN)3, poly‐m‐phenylenediamine, and carbon black is presented. The advantage of using Fe(SCN)3 as iron source is that the obtained catalyst has a high level of S doping and high surface area, and thus exhibits excellent ORR activity (23 A g−1 at 0.80 V) in 0.1 M H2SO4 solution. When the Fe/N/C‐SCN was applied in a PEMFC as cathode catalyst, the maximal power density could exceed 1 W cm−2.
A non‐precious Fe/N/C electrocatalyst was prepared through pyrolysis of Fe(SCN)3, poly‐m‐phenylenediamine, and carbon black. The obtained Fe/N/C catalyst has high level of S doping and high surface area, and thus exhibits excellent catalytic activity for the oxygen reduction reaction in acidic solution. A polymer electrolyte membrane fuel cell using this catalyst as the cathode can yield a maximal power density as high as 1.03 W cm−2.
Summary
Tumor necrosis factor receptor (TNFR)‐associated factors (TRAFs) form a family of proteins that are best known as signaling adapters of TNFRs. However, emerging evidence suggests that TRAF ...proteins, particularly TRAF2 and TRAF3, also regulate signal transduction by controlling the fate of intracellular signaling factors. A well‐recognized function of TRAF2 and TRAF3 in this aspect is to mediate ubiquitin‐dependent degradation of nuclear factor‐κB (NF‐κB)‐inducing kinase (NIK), an action required for the control of NIK‐regulated non‐canonical NF‐κB signaling pathway. TRAF2 and TRAF3 form a complex with the E3 ubiquitin ligase cIAP (cIAP1 or cIAP2), in which TRAF3 serves as the NIK‐binding adapter. Recent evidence suggests that the cIAP‐TRAF2‐TRAF3 E3 complex also targets additional signaling factors for ubiquitin‐dependent degradation, thereby regulating important aspects of immune and inflammatory responses. This review provides both historical aspects and new insights into the signaling functions of this ubiquitination system.
A copper‐catalyzed asymmetric radical oxytrifluoromethylation of alkenyl oxime and Togni's reagent has been successfully developed, thereby providing straightforward access to CF3‐containing ...isoxazolines bearing α‐tertiary stereocenters with excellent yield and enantioselectivity. The key to success is the rational design of cinchona‐alkaloid‐based sulfonamides as neutral/anionic hybrid ligands to effectively control the stereochemistry in copper‐catalyzed reactions involving free alkyl radical species. The utility of this method is illustrated by efficient transformation of the products into useful chiral CF3‐containing 1,3‐aminoalcohols.
Powerful hybrid ligand: Cinchona‐alkaloid‐based sulfonamides were designed as effective hybrid ligands for copper, which enabled catalytic asymmetric radical oxytrifluoromethylation of alkenyl oximes to give CF3‐containing isoxazolines bearing α‐tertiary stereocenters with excellent yield and enantioselectivity.
Transition metal-catalyzed enantioselective Sonogashira-type oxidative C(sp
)-C(sp) coupling of unactivated C(sp
)-H bonds with terminal alkynes has remained a prominent challenge. The difficulties ...mainly stem from the regiocontrol in unactivated C(sp
)-H bond functionalization and the inhibition of readily occurring Glaser homocoupling of terminal alkynes. Here, we report a copper/chiral cinchona alkaloid-based N,N,P-ligand catalyst for asymmetric oxidative cross-coupling of unactivated C(sp
)-H bonds with terminal alkynes in a highly regio-, chemo-, and enantioselective manner. The use of N-fluoroamide as a mild oxidant is essential to site-selectively generate alkyl radical species while efficiently avoiding Glaser homocoupling. This reaction accommodates a range of (hetero)aryl and alkyl alkynes; (hetero)benzylic and propargylic C(sp
)-H bonds are all applicable. This process allows expedient access to chiral alkynyl amides/aldehydes. More importantly, it also provides a versatile tool for the construction of chiral C(sp
)-C(sp), C(sp
)-C(sp
), and C(sp
)-C(sp
) bonds when allied with follow-up transformations.
We describe a photoinduced copper‐catalyzed asymmetric radical decarboxylative alkynylation of bench‐stable N‐hydroxyphthalimide(NHP)‐type esters of racemic alkyl carboxylic acids with terminal ...alkynes, which provides a flexible platform for the construction of chiral C(sp3)−C(sp) bonds. Critical to the success of this process are not only the use of the copper catalyst as a dual photo‐ and cross‐coupling catalyst but also tuning of the NHP‐type esters to inhibit the facile homodimerization of the alkyl radical and terminal alkyne, respectively. Owing to the use of stable and easily available NHP‐type esters, the reaction features a broader substrate scope compared with reactions using the alkyl halide counterparts, covering (hetero)benzyl‐, allyl‐, and aminocarbonyl‐substituted carboxylic acid derivatives, and (hetero)aryl and alkyl as well as silyl alkynes, thus providing a vital complementary approach to the previously reported method.
Two in one: A photoinduced asymmetric radical decarboxylative alkynylation of bench‐stable racemic carboxylic acid derivatives with easily available terminal alkynes provides expedient access to diverse enantioenriched alkynes. The chiral copper catalyst serves as a dual photo‐ and cross‐coupling catalyst to achieve stereocontrol over the highly reactive prochiral alkyl radical intermediates.
A viologen‐based Borromean entangled porous framework was found to be sensitive to both CuKα and MoKα X‐ray sources, showing rapid photochromic response and recovery within one minute. The ...X‐ray‐induced photochromic process is accompanied by a reversible single‐crystal‐to‐single‐crystal (SC‐SC) structural transformation, an unprecedented phenomenon for X‐ray sensitive materials. The complex can be further processed into portable thin films for detecting the dose of the X‐ray exposure. Moreover, the photochromism can occur over a broad temperature range of 100–333 K, both in the form of single crystals and thin films, making it a potential candidate for practical indoor and outdoor applications.
X‐ray specs: A viologen‐based Borromean‐entangled porous framework was found sensitive to X‐rays and undergo a rapid photochromic response and recovery. This process is accompanied by a reversible single‐crystal‐to‐single‐crystal transformation. The material can be further processed into a thin film for detecting the dose of X‐ray exposure.
The innate immune sensor NLRP3 assembles an inflammasome complex with NEK7 and ASC to activate caspase‐1 and drive the maturation of proinflammatory cytokines IL‐1β and IL‐18. NLRP3 inflammasome ...activity must be tightly controlled, as its over‐activation is involved in the pathogenesis of inflammatory diseases. Here, we show that NLRP3 inflammasome activation is suppressed by a centrosomal protein Spata2. Spata2 deficiency enhances NLRP3 inflammasome activity both in the macrophages and in an animal model of peritonitis. Mechanistically, Spata2 recruits the deubiquitinase CYLD to the centrosome for deubiquitination of polo‐like kinase 4 (PLK4), the master regulator of centrosome duplication. Deubiquitination of PLK4 facilitates its binding to and phosphorylation of NEK7 at Ser204. NEK7 phosphorylation in turn attenuates NEK7 and NLRP3 interaction, which is required for NLRP3 inflammasome activation. Pharmacological or shRNA‐mediated inhibition of PLK4, or mutation of the NEK7 Ser204 phosphorylation site, augments NEK7 interaction with NLRP3 and causes increased NLRP3 inflammasome activation. Our study unravels a novel centrosomal regulatory pathway of inflammasome activation and may provide new therapeutic targets for the treatment of NLRP3‐associated inflammatory diseases.
Synopsis
NLRP3 inflammasome activation requires the interaction of NLRP3 with centrosomal kinase NEK7. Here we show that the centrosome‐localized deubiquitinase complex Spata2‐CYLD deubiquitinates centrosomal kinase PLK4 to augment its binding to and phosphorylation of NEK7, leading to reduced NEK7‐NLRP3 interaction and NLRP3 inflammasome activation.
Spata2 is localized to the centrosome and suppresses NLRP3 inflammasome activation.
Spata2 recruits CYLD to the centrosome to deubiquitinate PLK4.
Deubiquitination of PLK4 facilitates its binding to and phosphorylation of NEK7.
NEK7 phosphorylation by PLK4 attenuates NEK7‐NLRP3 interaction and NLRP3 inflammasome activation.
The centrosomal protein Spata2 is as a novel regulator of NEK7 phosphorylation and NLRP3‐mediated inflammatory responses.
To achieve the high-precision angular velocity and angular acceleration estimation of spacecraft under high dynamic conditions, a novel method based on single-gimbal magnetically suspended control ...moment gyroscope (SGMSCMG) configuration is proposed in this paper. Both the angular rates and angular accelerations have been resolved analytically, and their comparative estimation precision between the proposed method and the traditional one has been further analyzed in the presence of gyro error and installation error. Compared to the traditional three-orthogonal configuration method, the proposed one employs any three SGMSCMGs in the control actuator configuration instead of additional rate gyros. All the inertial coupling items are retained tactfully in the angular rate and angular acceleration solution by the proposed method. Thus, the relative estimation accuracy of the attitude rate depends only on the gyro error and its installation error in practice, which do not decay under high dynamic conditions anymore. And its corresponding angular acceleration estimation precision is determined by the size of angular velocity instead of angular acceleration under the given error condition. The semiphysical simulation results demonstrate the correctness and superiority of the proposed estimation method.
Aimed at solving the microvibration issue of spacecraft, this paper adopts two orthogonal Vernier-gimballing magnetically suspended flywheels (VGMSFs) as vibration suppression actuator. The vibration ...decoupling control law and Vernier-gimballing steering law of the VGMSFs is designed to output the translational and rotational reference displacements of the VGMSFs. By extending the traditional modal decoupling of the magnetically suspended rotor, the on-orbit nonlinear VGMSF system coupled with satellite realizes the precise modal separation and rotation mode decoupling. This method not only realizes complete compensation for the disturbance torque from spacecraft to VGMSFs, but also improves the decoupling precision of Vernier-gimballing moment of VGMSFs. Most importantly, through independent control of translation and rotational modes of on-orbit VGMSFs, the parameter regulation range of spacecraft vibration decoupling controller is greatly enlarged, effectively improving the microvibration suppression effect of spacecraft. The semiphysical simulation results testify the effectiveness and superiority of this method.
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