Ozonolysis of 18α-Oleanane triterpenoid with an alkenenitrile moiety in the five-membered ring A

A novel synthetic protocol of ozonolytic cleavage of 18α-oleanane triterpenoid with the five-membered α,β-alkenenitrile moiety dissolved in dichloromethane to selectively synthesize a 1,3-secotriterpene derivative with 78% yield was developed. Spontaneous condensations of the synthesized 19β,28-epoxy-1,3-seco-2-nor-18α-olean-3-al-1-oic acid followed by formation of unsubstituted 1,3- and 1,4-lactones were registered in reactions with sodium borohydride as a reducing reagent or oxalyl chloride as an activating agent, respectively. α-Methoxy- and α-ethoxy-substituted 1,3-lactones were obtained when the polar protic solvents methanol or ethanol were used for the ozonolysis of the alkenenitrile. Experiments on ozonolysis were carried out in combination with reduction with dimethyl sulfide. Ozonolysis of alkenenitrile in dichloromethane without reductive treatment was found out to have resulted in stable triterpene ozonide.     

Synthesis of tritium-labeled PAM-43

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Design of pincer complexes based on (methylsulfanyl)acetic/propionic acid amides with ancillary S‐ and N‐donors as potential catalysts and cytotoxic agents

Pincer complexes featuring readily tunable tridentate ligand frameworks comprise one of the most actively studied classes of organometallic and metal–organic compounds and find extensive use in catalysis, organic synthesis, materials science, and other fields of chemistry and allied disciplines. Currently growing attention is devoted to non‐classical ligand scaffolds, such as functionalized carboxamides, which offer multiple options for directed structural modifications. In this study, the reactions of (methylsulfanyl)acetyl and propanoyl chlorides with 2‐(aminomethyl)pyridine, 2‐(2‐aminoethyl)pyridine, 8‐aminoquinoline and 2‐(diphenylthiophosphoryl)aniline afford a series of new pincer‐type ligands based on functionalized carboxamides. The ligands obtained readily undergo direct cyclopalladation under the action of PdCl₂(NCPh)₂ in dichloromethane at room temperature, resulting in Pd(II) pincer complexes with N,N,S‐ and S,N,S‐donor sets. Importantly, some of the cyclopalladated derivatives can also be produced efficiently under solvent‐free conditions according to the approach recently developed by our group. The complexes obtained have been tested for cytotoxicity against several human cancer cell lines and catalytic activity in the model Suzuki reaction. The results have been compared to those for the related Pd(II) pincer complexes to define the main structure–activity relationships and to outline the most promising structures for further investigations.     

Stack the Bowls: Tailoring the Electronic Structure of Corannulene‐Integrated Crystalline Materials

We report the first examples of purely organic donor–acceptor materials with integrated π‐bowls (πBs) that combine not only crystallinity and high surface areas but also exhibit tunable electronic properties, resulting in a four‐orders‐of‐magnitude conductivity enhancement in comparison with the parent framework. In addition to the first report of alkyne–azide cycloaddition utilized for corannulene immobilization in the solid state, we also probed the charge transfer rate within the Marcus theory as a function of mutual πB orientation for the first time, as well as shed light on the density of states near the Fermi edge. These studies could foreshadow new avenues for πB utilization for the development of optoelectronic devices or a route for highly efficient porous electrodes.     

Specific Sorption Sites for Nitrogen in Zeolites NaLSX and LiLSX

Specific sorption sites for nitrogen, N₂, in NaLSX and LiLSX zeolites were investigated using a DRIFT spectroscopic method. Sorption of molecular hydrogen, H₂, by NaLSX or LiLSX zeolite at 77 K with DRIFT control of perturbation of sorbed molecules allowed to discriminate two or three different types of specific sorption sites in the respective zeolites. Their H–H stretching frequencies are 4077 and 4081 cm^–1 for NaLSX, and 4061, 4084 and 4129 cm^–1 for LiLSX. With reference to an independent investigation by methods of both sorption thermodynamics and molecular modeling for N₂ sorption on LiLSX, the first two of the corresponding bands were ascribed to H₂ sorption on lithium cations, Li⁺, localized in supercages of the faujasite, FAU, zeolite framework at sites SIII and SIII, while the latter band most likely belongs to H₂ sorption on Li⁺ cations at sites SII, and on hydroxyl groups, OH. Sorption of N₂ by Li⁺ cations at sites SIII and SIII is the strongest, resulting in a decrease of intensity of the corresponding DRIFT bands that stem from subsequent H₂ sorption. Nitrogen sorption by Li⁺ cations at sites SII is much weaker. Sorption of N₂ on Na⁺ cations at sites SIII in NaLSX zeolite is also stronger than by Na⁺ cations at sites SII.     

CdBiO2Cl: synthesis and powder structure solution

The title compound, cadmium bismuth dioxide chloride, CdBiO₂Cl, was obtained as a white powder by reaction of solid BiOCl with CdO at 973 K. Ab initio crystal structure determination was carried out using X-ray powder diffraction techniques, including direct methods for atom location and Rietveld fitting for the final refinement. Being monoclinic, the crystal structure can be related to tetragonal Sillen layered phases. The main structural elements present are CdBiO₂⁺ pleated metal–oxy­gen layers alternating with Cl layers along the c axis, whereas along the b axis, all atoms are on mirror planes. The formation of a strong Cd—Cl bond draws the layers together, causing layer deformation and a monoclinic distortion in the layer arrangement.     

Synthesis and antiviral activity of novel imidazo[2,1-b]thiazoles coupled with morpholine and thiomorpholines

Herein described the synthesis and antiviral evaluation of a novel series of morpholine and thio-morpholine coupled imidazo[2,1-b]thiazoles. The three-step reaction sequence involving the condensation of 1,3-dichloroacetone with thiourea followed by coupling with morpholine and thiomorpholine and finally cyclization with substituted α-bromoacetophenones yielded the desired imidazothiazoles 7(a–l) . Screening of all the new compounds for their in vitro antiviral activity against influenza virus A/Puerto Rico/8/34 (H1N1) in MDCK cells, resulted in two potent analogs, 7d (IC₅₀: 1.1 μM, C₅₀: >300 μM, SI = 273) and 7e (IC₅₀: 2.0 μM, C₅₀: >300 μM, SI = 150), with a favorable toxicity profile and are the best anti-influenza hit analogs for further structural optimization.     

The influence of convection theories on the solar envelope structure and five-minute oscillation spectrum of the sun

We study the structure of the solar convective zone. The standard mixing length theory (MLT) is compared with several alternative theories. The influence of the superadiabatic convection region on the acoustic oscillation spectrum is examined. It is shown that the outermost superadiabatic layers have a strong effect on the five-minute oscillation spectrum, especially at the high frequencies. Comparison with the observed spectrum shows a decrease in the frequency difference for the convection theories which have a higher superadiabatic gradient in the outermost layers.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 10, pp. 1194–1198, October, 1996.