Iridium(iii) complexes bearing the 2-(2-quinolinyl)quinoxaline ligand absorb weakly at 450–750 nm and can be used as broadband reverse saturable absorbers.
Lysine demethylase 5A (KDM5A) is a negative regulator of histone H3K4 trimethylation, a histone mark associated with activate gene transcription. We identify that KDM5A interacts with the P-TEFb complex and cooperates with MYC to control MYC targeted genes in multiple myeloma (MM) cells. We develop a cell-permeable and selective KDM5 inhibitor, JQKD82, that increases histone H3K4me3 but paradoxically inhibits downstream MYC-driven transcriptional output in vitro and in vivo. Using genetic ablation together with our inhibitor, we establish that KDM5A supports MYC target gene transcription independent of MYC itself, by supporting TFIIH (CDK7)-and P-TEFb (CDK9)mediated phosphorylation of RNAPII.These data identify KDM5A as a unique vulnerability in MM functioning through regulation of MYC-target gene transcription, and establish JQKD82 as a tool compound to block KDM5A function as a potential therapeutic strategy for MM.
Multifunctional chiral phosphine (phosphine-thiourea type) L2-catalyzed allylic substitutions of MBH adducts 1 with oxazolones 2 produce the corresponding optically active adducts 3 in good to excellent yields and ee's as well as moderate to good de's under mild conditions. The synergistic interaction between hydrogen bond donor site and nucleophilic site has been discussed, indicating that finely tuning the active sites of the multifunctional phosphine organocatalysts is very important.
Insect communities with diverse life histories and morphologies, such as bees (Hymenoptera: Apoidea), are difficult to representatively sample. Methodological comparison studies have increased our knowledge of bee-sampling method biases. However, further understanding of how sampling methodologies are biased with respect to functional traits and the surrounding environment is needed. We examined the differences in taxonomic and functional trait representation of sampled bee communities between an active netting and passive bee bowl methodology. We also determined the influence of surrounding floral resources on each method's ability to capture bee abundance, richness, and diversity. We captured bees at 32 sites across North Dakota, USA using both methods. Netting and bee bowl methods reflected different bee communities defined by taxonomic families, genera, diet breadth, sociality, and body size. Bee bowls reflected more solitary and small-bodied bees while the netting method selected a greater representation of generalist, social, and large-bodied taxa. Bee bowls captured fewer bees as floral abundance increased, while bee abundance, richness, and diversity captured with the netting method showed the opposite trend with increasing floral resource availability. In addition, the netting method generally captured more varied samples than bee bowl surveys. Our results indicate the importance of using multiple types of sampling methods and of understanding how surrounding floral availability affects sampling of the target bee communities. Methodological biases influence how ecological studies interpret target communities, making it essential for future bee-sampling to incorporate multiple methods and to interpret their results carefully in the context of chosen methodologies and study systems. Implications for insect conservationThe essential ecological services many bees provide, coupled with the concern over declines in bee populations and diversity, fuels the increased interest in bees and studies involving bee-sampling. Management and conservation policy for declining bee populations depend on data that is representative of the sampled bee communities. Therefore, it is important to understand systematic biases in our sampling methods as well as the effects of surrounding habitat on these biases.
Abstract:The 1,4-diazabicyclicA C H T U N G T R E N N U N G [2.2.2]octane (DABCO)-catalyzed intermolecular Rauhut-Currier reaction of maleimides with electron-deficient allenes has been investigated, affording the corresponding products in good to high yields under mild conditions. The first example of a b-isocupreidine (b-ICD)-catalyzed highly enantioselective intermolecular Rauhut-Currier reaction of male-A C H T U N G T R E N N U N G imides with allenoates and penta-3,4-dien-2-one has been also developed, allowing the synthesis of optically active functionalized allene derivatives in good to high yields along with good to excellent enantioselectivities.The Rauhut-Currier (RC) reaction, also known as vinylogous Morita-Baylis-Hillman (MBH) reaction, involves the coupling of one active alkene/latent enolate to a second Michael acceptor, producing a new C À C bond between the a-position of one activated alkene and the b-position of a second alkene under the catalysis of a nucleophilic species.[1] This reaction was first reported by Rauhut and Currier in 1963 in the dimerization of electron-deficient alkenes catalyzed by tertiary phosphine.[1b] A few years later, a series of phosphine-catalyzed intermolecular RC reactions was subsequently explored, demonstrating the wide synthetic utility of this reaction.[2] Moreover, in 1986, Amri and Villieras [3] first disclosed that tertiary amines such as 1,4-diazabicyclicA C H T U N G T R E N N U N G [2.2.2]octane (DABCO) could also efficiently catalyze the intermolecular RC reactions under mild conditions and since then, this type of tertiary amine-catalyzed intermolecular RC reactions has been further developed by Basavaiah and co-workers as well as other researchers during the last decades.[4] The first asymmetric version of an intermolecular Rauhut-Currier reaction was presented by Wang and co-workers using a Cinchona alkaloid thiourea as a catalyst in a novel asymmetric Michael-Michael cascade reaction of trans-3-(2-mercaptophenyl)-2-propenoic acid ethyl ester with transb-nitrostyrene in 2008.[5] Almost at the same time, scandium triflate [ScA C H T U N G T R E N N U N G (OTf) 3 ] combined with (R,R)-Phpybox was used as a catalyst by Scheidt and co-workers in an intermolecular RC reaction of silyloxyallenes with a,b-unsaturated ketones, affording the corresponding product in 72% yield, 20:1 (Z:E) and 70% ee.[6] However, to the best of our knowledge, there has been no report on the asymmetric intermolecular RC reaction involving electron-deficient alkenes with allenes promoted by the amine-based organocatalyst, although enantioselective intramolecular RC-type reactions have achieved a great progress in recent years. [7,8] In this paper, we would like to disclose the application of quinidine-derived b-isocupreidine (b-ICD) as organocatalyst for the asymmetric intermolecular RC reaction of maleimides with electron-deficient allenes, giving the corresponding products in high yields and good to high ee values under mild conditions. We initiated our investigations by seeking ...
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