Cyclopenta-fused polycyclic aromatic hydrocarbons (CP-PAHs), potentially electronically and biologically highly active materials, were synthesized from readily available 2-aryl-substituted anilines. Reactions occur under extremely mild, room temperature conditions using (t)BuONO as the sole reagent. The use of a nitrite source generates a reactive diazonium intermediate in situ that then reacts with a tethered polycyclic aromatic moiety by intramolecular aromatic substitution. This protocol could be presented as one of the simplest methods to access CP-PAHs.
<p>Effect of herbacetin or kaempferol on ODC activity. (A) Herbacetin or (B) kaempferol was modeled as an allosteric inhibitor with the ODC crystal structure. (C) The effect of herbacetin or kaempferol (upper panels) on ODC activity (lower panel) was assessed using a human ODC recombinant protein. Each reaction was incubated at 37{degree sign}C for 1 h and ODC activity was measured as the release of CO2 from L-[1-C14] ornithine. Data are represented as mean values {plus minus} S.D. of triplicate experiments. The asterisk (*) indicates a significant decrease (p < 0.05) in ODC activity between herbacetin-treated samples compared to untreated or kaempferol-treated samples.</p>
<p>The effect of herbacetin on cell cycle. The effect of herbacetin or DFMO on cell cycle was determined using HCT116, DLD1 or HT29 colon cancer cells. Cells were treated with herbacetin or DFMO for 48 h in medium supplemented with 10% FBS and then cells were serum starved for 24 h in medium supplemented with 0.5% FBS. Cells were stained with propidium iodide (PI) and cell cycle was analyzed by Fluorescence Activated Cell Sorting (FACS). All data are represented as mean values {plus minus} S.D. of triplicate values from 3 independent experiments. The asterisk (*) indicates a significant effect (p < 0.05) of herbacetin or DFMO compared to untreated control.</p>
Fluoroalkylated alkynes, which are versatile building blocks for the synthesis of various biologically active organofluorine compounds, were synthesized from easily available alkynyl halides and fluoroalkyl halides by visible-light photocatalysis.
Multiple metals in action: Relying on the prowess of various metal-catalyzed CO and CC bond-forming reactions, a concise asymmetric total synthesis of (−)-dactylolide has been achieved (see scheme). The formation of a Z-trisubstituted vinylboronate through an Alder–ene reaction and subsequent rhenium-mediated regioselective transposition of an allylic alcohol are the key features of this convergent synthesis. Detailed facts of importance to specialist readers are published as "Supporting Information". Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.
Abstract Photocatalysis provides a versatile approach to redox activation of various organic substrates for synthetic applications. To broaden the scope of photoredox catalysis, developing catalysts with strong photoredox power is imperative. Photoredox catalysts with excited-state properties that include cathodic oxidation potentials and long lifetimes are particularly demanded. In this research, we demonstrate the high-efficiency catalytic utility of two-coordinated Au(I) complex photocatalysts that exhibit an exclusive ligand-to-ligand charge-transfer (LLCT) transition in C-C cross-coupling reactions between N -heterocycles and (hetero)aryl halides, including redox-resistant (hetero)aryl chlorides. Our photocatalysis system can steer reactions under visible-light irradiation at a catalyst loading as low as 0.1 mol% and exhibits a broad substrate scope with high chemo- and regioselectivity. Our mechanistic investigations provide direct spectroscopic evidence for each step in the catalysis cycle and demonstrate that the LLCT-active Au(I) complex catalysts offer several benefits, including strong visible-light absorption, a 207 ns-long excited-state lifetime without short-lived components, and a 91% yield in the production of free-radical intermediates. Given the wide structural versatility of the proposed catalysts, we envision that our research will provide useful insights into the future utilization of the LLCT-active Au(I) complex for organic transformations.
Nanog regulates human and mouse embryonic stem (ES) cell self-renewal activity. Activation of ERKs signaling negatively regulates ES cell self-renewal and induces differentiation, but the mechanisms are not understood. We found that ERK1 binds and phosphorylates Nanog. Activation of MEK/ERKs signaling and phosphorylation of Nanog inhibit Nanog transactivation, inducing ES cell differentiation. Conversely, suppression of MEK/ERKs signaling enhances Nanog transactivation to inhibit ES cell differentiation. We observed that phosphorylation of Nanog by ERK1 decreases Nanog stability through ubiquitination-mediated protein degradation. Further, we found that this phosphorylation induces binding of FBXW8 with Nanog to reduce Nanog protein stability. Overall, our results demonstrated that ERKs-mediated Nanog phosphorylation plays an important role in self-renewal of ES cells through FBXW8-mediated Nanog protein stability.
Abstract This review covers the visible light induced reactions of quinones such as benzoquinone, naphthoquinone, and anthraquinone. These quinones are distinguished by their fully conjugated structures, which feature minimal energy gaps, and nonbonding electron pairs on the oxygen atoms. Such structural attributes facilitate n p → π* transition, allowing for easy access to excited states and rendering quinones highly reactive under visible‐light irradiation. We describe three primary types of reactions facilitated by these electronic characteristics: Paternò–Büchi (PB) reactions, which entail [2 + 2] photocycloaddition between the carbonyl groups of quinones and alkenes or alkynes; CH activation processes, which showcase quinones' versatility in functionalizing hydrocarbons; and the formation of electron donor–acceptor complexes, demonstrating quinones' capability to engage in charge transfer interactions. Through this review, we highlight the critical role quinones play in photochemistry, their unique electronic properties, and their broad applicability in synthetic organic chemistry.
The allelic variations at the Vrn-1 and Ppd-1 loci of Korean wheat cultivars were determined to evaluate their effects on agronomic traits and response to vernalization treatment. Korean wheat cultivars displayed high frequency of Vrn-D1a and Ppd-B1b alleles, but all of the tested cultivars carried vrn-A1, vrn-B1, Ppd-A1b and Ppd-D1a alleles at the corresponding loci. Regardless of vernalization treatments, Korean wheat cultivars carrying the vrn-D1 allele showed longer days to flag leaf unfolding than those with the Vrn-D1a allele. Unvernalized cultivars carrying the vrn-D1 allele also exhibited larger final leaf number than those with the Vrn-D1a allele. However, there were no significant differences in the response of the Korean wheat cultivars to vernalization treatment based on allelic variation at the Ppd-1 loci. With respect to agronomic traits, the Vrn-D1a allele was related to increased grain yield and decreased thousand kernel weight compared to the vrn-D1 allele. Cultivars carrying both Vrn-D1a and Ppd-B1b alleles produced higher grain yield (5.5 tons/ha) than those with the vrn-D1 and Ppd-B1b alleles (5.0 tons/ha).
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