Synthesis of nonionic ether-backbone analogues of RNA from pseudooligosaccharides

Uracil nucleosides with internucleosidic ether linkage as nonionic analogues of RNA were synthesized by glycosylation of ether-backbone pseudooligosaccharides.     

C−H Methylation of Iminoamido Heterocycles with Sulfur Ylides**

The direct methylation of N‐heterocycles is an important transformation for the advancement of pharmaceuticals, agrochemicals, functional materials, and other chemical entities. Herein, the unprecedented C(sp²)‐H methylation of iminoamido heterocycles as nucleoside base analogues is described. Notably, trimethylsulfoxonium salt was employed as a methylating agent under aqueous conditions. A wide substrate scope and excellent level of functional‐group tolerance were attained. Moreover, this method can be readily applied to the site‐selective methylation of azauracil nucleosides. The feasibility of gram‐scale reactions and various transformations of the products highlight the synthetic potential of the developed method. Combined deuterium‐labeling experiments aided the elucidation of a plausible reaction mechanism.     

Efficient bifurcation and tabulation of multi-dimensional combustion manifolds using deep mixture of experts: An a priori study

This work describes and validates an approach for autonomously bifurcating turbulent combustion manifolds to divide regression tasks amongst specialized artificial neural networks (ANNs). This approach relies on the mixture of experts (MoE) framework, where each neural network is trained to be specialized in a given portion of the input space. The assignment of different input regions to the experts is determined by a gating network, which is a neural network classifier. In some previous studies [1], [2], [3], [4], it has been demonstrated that bifurcation of a complex combustion manifold and fitting different ANNs for each part leads to better fits or faster inference speeds. However, the manner of bifurcation in these studies was based on heuristic approaches or clustering techniques. In contrast, the proposed technique enables automatic bifurcation using non-linear planes in high-dimensional turbulent combustion manifolds that are often associated with complex behavior due to different dominating physics in various zones. The proposed concept is validated using 4-dimensional (4D) and 5D flamelet tables, showing that the errors obtained with a given network size, or conversely the network size required to achieve a given accuracy, is considerably reduced. The effect of the number of experts on inference speed is also investigated, showing that by increasing the number of experts from 1 to 8, the inference time can be approximately reduced by a factor of two. Moreover, it is shown that the MoE approach divides the input manifold in a physically intuitive manner, suggesting that the MoE framework can elucidate high-dimensional datasets in a physically meaningful way.     

The Effect of Guest Metal Ions on the Reduction Potentials of Uranium(VI) Complexes: Experimental and Theoretical Investigations

Two mononuclear uranyl complexes, [UO₂L¹] ( 1 ) and [UO₂L²] ⋅ 0.5 CH₃CN ⋅ 0.25 CH₃OH ( 2 ), have been synthesized from two multidentate N₃O₄ donor ligands, N,N′-bis(5-methoxysalicylidene)diethylenetriamine (H₂L¹) and N,N′-bis(3-methoxysalicylidene)diethylenetriamine (H₂L²), respectively, and have been structurally characterized. Both complexes 1 and 2 showed a reversible U^VI/U^V couple at −1.571 and −1.519 V, respectively, in cyclic voltammetry. The reduction potential of the U^VI/U^V couple shifted towards more positive potential on addition of Li⁺, Na⁺, K⁺, and Ag⁺ metal ions to acetonitrile solutions of complex 2 , and the resulting potential was correlated with the Lewis acidity of the metal ions and was also justified by theoretical DFT calculations. No such shift in reduction potential was observed for complex 1 . All four bimetallic products, [UO₂L²Li_0.5](ClO₄)_0.5 ( 3 ), [UO₂L²Na(ClO₄)]₂ ( 4 ), [UO₂L²Ag(NO₃)(H₂O)] ( 5 ), and [(UO₂L²)₂K(H₂O)₂]PF₆ ( 6 ), formed on addition of the Li⁺, Na⁺, Ag⁺, and K⁺ metal ions, respectively, to acetonitrile solutions of complex 2 , were isolated in the solid state and structurally characterized by single-crystal X-ray diffraction. In all the species, the inner N₃O₂ donor set of the ligand encompasses the equatorial plane of the uranyl ion and the outer open compartment with O₂O′₂ donor sites hosts the second metal ion.     

Design and Synthesis of Benzimidazole-Linked meta-Substituted Benzylidenes/Benzyls as Biologically Significant New Chemical Entities

meta-Linked thiazolidinedione (TZD)– and diethyl malonate (DEM)–based benzylidenes and methyl acetoacetate (MAA)–based benzyl moieties linked to the 2-position of N-methyl benzimidazole were synthesized. TZD- and DEM-based compounds were synthesized by condensation of 2,4-thiazolidinedone and DEM respectively with the corresponding 3-substituted benzaldehyde, whereas MAA-based compounds were obtained by halogen displacement with the corresponding 3-substituted phenol. These new chemical entities were designed to provide a balanced agonism at the peroxisome proliferator activated receptor alpha/gamma (PPARα/γ) in the management of type 2 diabetes: a move from glitazones to selective PPARγ modulators (SPPARγMs).

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Chain elongation of monosaccharides by sequential cross metathesis and asymmetric dihydroxylation: expeditious approach to higher sugars

Glucose-derived alkenes were homologated via chain elongation to afford higher sugars by the application of cross metathesis with an alkene followed by Sharpless asymmetric dihydroxylation. Heptose, octose, nonose, and decose derivatives were expeditiously prepared by this method.     

Separation of Sr(II) from Eu(III) across a supported liquid membrane using TEHDGA and 18-crown-6

Journal of Radioanalytical and Nuclear Chemistry - This paper reports the result of process development studies on separation of Sr(II) from Eu(III) in 4 M nitric acid using supported...     

Investigation of experimental observables in search of the chiral magnetic effect in heavy-ion collisions in the STAR experiment

The chiral magnetic effect(CME)is a novel transport phenomenon,arising from the interplay between quantum anomalies and strong magnetic fields in chiral systems.In high-energy nuclear collisions,the CME may survive the expansion of the quark-gluon plasma fireball and be detected in experiments.Over the past two decades,experimental searches for the CME have attracted extensive interest at the Relativistic Heavy Ion Collider(RHIC)and the Large Hadron Collider(LHC).The main goal of this study is to investigate three pertinent experimental approaches:the$\gamma$correlator,the R correlator,and the signed balance functions.We exploit simple Monte Carlo simulations and a realistic event generator(EBE-AVFD)to verify the equivalence of the core components among these methods and to ascertain their sensitivities to the CME signal and the background contributions for the isobar collisions at the RHIC.