Supercritical Fluid Extract of Putranjiva roxburghii Wall. Seeds Mitigates Fertility Impairment in a Zebrafish Model

Putrajeevak (Putranjiva roxburghii Wall.; synonym Drypetes roxburghii (Wall.) Hurus) seeds have been used since ancient times in the treatment of infertility in the Ayurvedic system of medicine in India. In this study, the oil component of Putrajeevak seeds (PJSO) was extracted using the supercritical fluid extraction (SCFE) method using liquid CO₂ and the constituents were analyzed using gas chromatography-flame ionized detectorand high-performance thin-layer chromatography. PJSO contained trace amounts of β-sitosterol with oleic and linoleic acids as the major fatty acid constituents. Male and female zebrafish were mutagenized with N-ethyl-N-nitrosourea (ENU) and fish that produced less than 20 viable embryos were selected for the study. SCFE oil extracts from the P. roxburghii seeds were used in this study to reverse fertility impairment. The mutant fish were fed with PJSO for a period of 14 days and the rates of fertility, conception, and fecundity were determined with wild-type healthy fish as a breeding partner. Treatment with PJSO increased the ovarian follicle count as well as the number of mature eggs, while reducing the number of ovarian cysts. Sperm count as well as sperm motility were greatly enhanced in the ENU-mutagenized male zebrafish when treated with PJSO. The results obtained in this study demonstrate the effectiveness of P. roxburghii seed oil in reversing impaired fertility in both male and female zebrafish models.     

H2 storage and equilibrium isotope effect for Be,Li, and Ti-doped closoborate complexes

Structural Chemistry - This work reports hydrogen uptake capacity and equilibrium isotope effect (EIE) for the Be, Li, and Ti-doped closoborate (B6H6) complexes using first-principles calculations...     

Camouflaging Structural Diversity: Co‐crystallization of Two Different Nanoparticles Having Different Cores But the Same Shell

Two ligand‐protected nanoscale silver moieties, [Ag₄₆(SPhMe₂)₂₄(PPh₃)₈](NO₃)₂ and [Ag₄₀(SPhMe₂)₂₄(PPh₃)₈](NO₃)₂ (abbreviated as Ag₄₆ and Ag₄₀, respectively) with almost the same shell but different cores were synthesized simultaneously. As their external structures are identical, the clusters were not distinguishable and become co‐crystallized. The occupancy of each cluster was 50 %. The outer shell of both is composed of Ag₃₂S₂₄P₈, which is reminiscent of fullerenes, and it encapsulates a well‐studied core, Ag₁₄ and a completely new core, Ag₈, which correspond to a face‐centered cube and a simple cube, respectively, resulting in the Ag₄₆ and Ag₄₀ clusters. The presence of two entities (Ag₄₀ and Ag₄₆ clusters) in a single crystal and their molecular formulae were confirmed by detailed electrospray ionization mass spectrometry. The optical spectrum of the mixture showed unique features which were in good agreement with the results from time‐dependent density functional theory (TD‐DFT).     

A one-pot direct regioselective iodination of Fischer-Borsche product using periodic acid in PEG-400

A metal-free and greener approach for the one-pot direct iodination and dehydrogenation of dihydrobenzo[a]carbazoles has been developed using periodic acid in polyethylene glycol-400 (PEG-400) under mild condition. This method has been proven to be tolerate to a broad range of functional groups, with good to excellent yields include metal-free inexpensive catalyst, easy work-up, benign reaction condition and high regioselectivity. The solvent has been successfully recycled up to 5 times without any loss of activity in an aqueous medium.     

Nature of halogen-centered intermolecular interactions in crystal growth and design: Fluorine-centered interactions in dimers in crystalline hexafluoropropylene as a prototype

The wide occurrence of halogen-centered noncovalent interactions in crystal growth and design prompted this study, which includes a mini review of recent advances in the field. Particular emphasis is placed on providing compelling theoretical evidence of the formation of these interactions between sites of positive electrostatic potential, as well as between sites of negative electrostatic potential, localized on the electrostatic surfaces of the bound fluorine atoms in a prototypical system, hexafluoropropylene (C₃F₆), upon its interaction with another same molecule to form (C₃F₆)₂ dimers. The existence of σ- and π-hole interactions is shown for the stable dimers. Even so, weakly bound interactions locally responsible in holding the molecular fragments together cannot and should not be overlooked since they are partly responsible for determining the overall geometry of the crystal. The results of combined quantum theory of atoms in molecules, molecular electrostatic surface potential, and reduced density gradient noncovalent interaction analyses showed that these latter interactions do indeed play a role in the stability and growth of crystalline C₃F₆ itself and the (C₃F₆)₂ dimers. A symmetry adapted perturbation theory energy decomposition analysis leads to the conclusion that a great majority of the (C₃F₆)₂ dimers examined are the consequence of dispersion (and electrostatics), with nonnegligible contribution from polarization, which together competes with an exchange repulsion component to determine the equilibrium geometries. In a few structures of the (C₃F₆)₂ dimer, the fluorine is found to serve as a six-center five-bond donor/acceptor, as found for carbon in other systems (Malischewski and Seppelt, Angew. Chem. Int. Ed. 2017, 56, 368). © 2019 Wiley Periodicals, Inc.     

Visible Light‐Induced,Metal‐Free Denitrative [3+2] Cycloaddition for Trisubstituted Pyrrole Synthesis

A metal‐free, regioselective synthesis of trisubstituted pyrroles has been developed through a formal [3+2] cycloaddition reaction between 2H‐azirines and nitroalkenes under visible light/photoredox‐catalyzed conditions. The reaction proceeds through 2H‐azaallenyl radical addition on β‐nitrostyrenes in a Michael fashion followed by a base‐mediated denitration reaction. The directive group influence of the nitro group controls the regiochemistry of the reaction.     

Intramolecular nitrone cycloaddition reaction on carbohydrate-based precursors: application in the synthesis of spironucleosides and spirobisnucleosides

A simple synthesis of chiral spironucleosides and spirobisnucleosides is described. Intramolecular 1,3-dipolar nitrone cycloaddition reaction of d-glucose-derived precursors having olefin at C-3 and nitrone at C-5, C-1, or C-2 (in nor-series) furnished bisisoxazolidinospirocycles 4-7, 11, and 12 in good yields. Reductive ring opening of the isoxazolidine moieties in 4-6 followed by construction of a nucleoside base upon the generated amino groups smoothly yielded spirobisnucleosides 17 and 18 and spironucleosides 20 and 21.     

Chemical modification of fluorinated self-assembled monolayer surfaces by low energy reactive ion bombardment

Reactive collisions of low energy (<100-eV) mass-selected ions are used to chemically modify fluorinated self-assembled monolayer surfaces comprised of alkanethiolate chains CF₃(CF₂)₁₁(CH₂)₂S— bound to Au. Typical experiments were done by using 1-nA/cm² beams and submonolayer doses of reactant ions. Characterization of the modified surface was achieved by in situ chemical sputtering (60-eV Xe^+·) and by independent high mass resolution time-of-flight-secondary ionization mass spectrometry (TOF-SIMS) (15–25-keV, Ga⁺) experiments. Treatment with Si³⁵C1 ₄ ^+· produced a surface from which Xe⁺ sputtering liberated CF₂ ³⁵C1⁺ ions, which suggested Cl-for-F halogen exchange at the surface. Isotopic labeling studies that used Si³⁵Cl₂ ³⁷Cl ₂ ^+· ; and experiments with bromine-containing and iodine-containing projectiles, confirmed this reaction. High mass resolution TOF-SIMS spectra, as well as high spatial resolution images, provided further evidence as to the existence of halogen-exchanged species at the bombarded surface. Analogous Cl-for-F halogen substitution was observed in a model gas-phase reaction. The ion-surface reaction is suggested to proceed through an intermediate fluoronium ion in which the projectile is bonded to the target molecule. The most significant conclusion of the study is that selective chemical modification of monolayer surfaces can be achieved by using reactive ion beams, which lead to new covalent bonds at the surface and in the scattered ions.     

Controllable self-assembly of organic-inorganic amphiphiles containing Dawson polyoxometalate clusters

An organic-inorganic molecular hybrid containing the Dawson polyoxometalate, ((C(4)H(9))(4)N)(5)H[P(2)V(3)W(15)O(59)(OCH(2))(3)CNHCOC(15)H(31)], was synthesized and its surfactant-like amphiphilic properties, represented by the formation of bilayer vesicles, were studied in polar solvents. The vesicle size decreases with both decreasing hybrid concentration and with increasing polarity of the solvent, independently. The self-assembly behavior of this hybrid can be controlled by introducing different counterions into the acetonitrile solutions. The addition of ZnCl(2) and NaI can cause a gradual decrease and increase of vesicular sizes, respectively. Tetraalkylammonium bromide is found to disassemble the vesicle assemblies. Moreover, the original counterions of the hybrid can be replaced with protons, resulting in pH-dependent formation of vesicles in aqueous solutions. The hybrid surfactant can further form micro-needle structures in aqueous solutions upon addition of Ca(2+) ions.     

Synthesis and antisense properties of fluoro cyclohexenyl nucleic acid (F-CeNA), a nuclease stable mimic of 2'-fluoro RNA

We report the design and synthesis of 2'-fluoro cyclohexenyl nucleic acid (F-CeNA) pyrimidine phosphoramidites and the synthesis and biophysical, structural, and biological evaluation of modified oligonucleotides. The synthesis of the nucleoside phosphoramidites was accomplished in multigram quantities starting from commercially available methyl-D-mannose pyranoside. Installation of the fluorine atom was accomplished using nonafluorobutanesulfonyl fluoride, and the cyclohexenyl ring system was assembled by means of a palladium-catalyzed Ferrier rearrangement. Installation of the nucleobase was carried out under Mitsunobu conditions followed by standard protecting group manipulations to provide the desired pyrimidine phosphoramidites. Biophysical evaluation indicated that F-CeNA shows behavior similar to that of a 2'-modified nucleotide, and duplexes with RNA showed slightly lower duplex thermostability as compared to that of the more rigid 3'-fluoro hexitol nucleic acid (FHNA). However, F-CeNA modified oligonucleotides were significantly more stable against digestion by snake venom phosphodiesterases (SVPD) as compared to unmodified DNA, 2'-fluoro RNA (FRNA), 2'-methoxyethyl RNA (MOE), and FHNA modified oligonucleotides. Examination of crystal structures of a modified DNA heptamer duplex d(GCG)-T*-d(GCG):d(CGCACGC) by X-ray crystallography indicated that the cyclohexenyl ring system exhibits both the (3)H(2) and (2)H(3) conformations, similar to the C3'-endo/C2'-endo conformation equilibrium seen in natural furanose nucleosides. In the (2)H(3) conformation, the equatorial fluorine engages in a relatively close contact with C8 (2.94 ?) of the 3'-adjacent dG nucleotide that may represent a pseudo hydrogen bond. In contrast, the cyclohexenyl ring of F-CeNA was found to exist exclusively in the (3)H(2) (C3'-endo like) conformation in the crystal structure of the modified A-form DNA decamer duplex [d(GCGTA)-T*-d(ACGC)](2.) In an animal experiment, a 16-mer F-CeNA gapmer ASO showed similar RNA affinity but significantly improved activity compared to that of a sequence matched MOE ASO, thus establishing F-CeNA as a useful modification for antisense applications.