Carboiodanation of Arynes: Organoiodine(III) Compounds as Nucleophilic Organometalloids

Organic iodine(III) compounds represent the most widely used hypervalent halogen compounds in organic synthesis, where they typically perform the role of an electrophile or oxidant to functionalize electron-rich or -nucleophilic organic compounds. In contrast to this convention, we discovered their unique reactivity as organometallic-like nucleophiles toward arynes. Equipped with diverse transferable ligands and supported by a tethered spectator ligand, the organoiodine(III) compounds undergo addition across the electrophilic C-C triple bond of arynes while retaining the trivalency of the iodine center. This carboiodanation reaction can forge a variety of aryl-alkynyl, aryl-alkenyl, and aryl-(hetero)aryl bonds along with the concurrent formation of an aryl-iodine(III) bond under mild conditions. The newly formed aryl-iodine(III) bond serves as a versatile linchpin for downstream transformations, particularly as an electrophilic reaction site. The amphoteric nature of the iodine(III) group as a metalloid and a leaving group in this sequence enables the flexible and expedient synthesis of extended π-conjugated molecules and privileged biarylphosphine ligands, where all of the iodine(III)-containing compounds can be handled as air- and thermally stable materials.

Copper-Catalyzed Intramolecular Olefinic C(sp2)-H Amidation for the Synthesis of γ-Alkylidene-γ-lactams

Herein, we report the copper-catalyzed dehydrogenative C(sp2)-N bond formation of 4-pentenamides via nitrogen-centered radicals. This reaction provides a straightforward and efficient preparation method for γ-alkylidene-γ-lactams. Notably, we could controllably synthesize α,β-unsaturated- or α,β-saturated-γ-alkylidene-γ-lactams depending on the reaction conditions.

(3R,7S)-12-Hydroxy- jasmonoyl-L-isoleucine is the genuine bioactive stereoisomer of a jasmonate metabolite in Arabidopsis thaliana

The oxylipin plant hormone JA-Ile is widely recognized as a plant defense hormone against pathogens and chewing insects. The metabolism of JA-Ile into 12-OH-JA-Ile and 12-COOH-JA-Ile is the central mechanism for the inactivation of JA signaling. Recently, 12-OH-JA-Ile was reported to function as a ligand for the JA-Ile co-receptor COI1-JAZ. However, in previous studies, the "12-OH-JA-Ile" used was a mixture of four stereoisomers, the naturally occurring cis-isomer (3R,7S)-12-OH-JA-Ile and the trans-isomer (3R,7R)-12-OH-JA-Ile and the unnatural cis-isomer (3S,7R)-12-OH-JA-Ile and the trans-isomer (3S,7S)-12-OH-JA-Ile. Thus, the genuine bioactive form of 12-OH-JA-Ile has not yet been identified. In this study, we prepared pure stereoisomers of 12-OH-JA-Ile and identified (3R,7S)-12-OH-JA-Ile, as the naturally occurring bioactive form of 12-OH-JA-Ile and found that it binds to COI1-JAZ9 as effectively as (3R,7S)-JA-Ile. In addition, we revealed that the unnatural trans-isomer (3S,7S)-12-OH-JA-L-Ile functions as another bioactive isomer. The pure (3R,7S)-12-OH-JA-Ile causes partial JA-responsive gene expression without affecting the expressions of JAZ8/10, which are involved in the negative feedback regulation of JA-signaling. Thus, (3R,7S)-12-OH-JA-Ile could cause weak and sustainable expression of certain JA-responsive genes until the catabolism of (3R,7S)-12-OH-JA-Ile into (3R,7S)-12-COOH-JA-Ile and (3R,7S)-12-OH-JA occurs. The use of chemically pure (3R,7S)-12-OH-JA-Ile confirmed the genuine biological activities of "12-OH-JA-Ile" by excluding the possible effects of other stereoisomers. A chemical supply of pure (3R,7S)-12-OH-JA-Ile with an exact bioactivity profile will enable further detailed studies of the unique role of 12-OH-JA-Ile in planta.

Iron-Catalyzed Biomimetic Dimerization of Tryptophan-Containing Peptides

Biomimetic oxidative dimerization of tryptophan derivatives in aqueous media with oxygen as a bulk oxidant catalyzed by an iron octacarboxy phthalocyanine complex was established. The discovery of the extremely active iron catalyst enables to perform aerobic enzyme-mimetic oxidation in the flask. This method was applicable to the oxidative dimerization of a wide range of tryptophan derivatives, including various dipeptides and oligopeptides with remarkable functional group tolerance without the protection of the amino acid residues. Furthermore, oxidative dimerization of tryptophan derivatives bearing dioxopiperazine units enabled the convergent total synthesis of five natural pyrroloindole compounds and unnatural congeners. The established chemical method will provide facile access to a broad range of dimerized peptides with the unique scaffold to link two turn structures, which would serve as a powerful tool to create new small- or middle-molecule drug candidates.

Sequential click modification of a lithium-ion endohedral fullerene connecting small molecules through a dieneazide linker

A versatile method for the chemical modification of a lithium-ion endohedral fullerene (Li⁺@C₆₀) to connect various small molecules is described. The designed dieneazide linker enables the facile connection of Li⁺@C₆₀ with small molecules bearing a terminal alkyne via Huisgen annulation and a subsequent Diels-Alder reaction. This strategy significantly expands the diversity of small molecules to be attached by Li⁺@C₆₀.

Thiourea fused γ-amino alcohol organocatalysts for asymmetric Mannich reaction of β-keto active methylene compounds with imines

Catalytic functionality of new optically active thiourea fused γ-amino alcohols was examined in the asymmetric Mannich reaction of β-keto active methylene compounds with imines to afford chiral Mannich products, β-amino keto compounds, with continuous chiral centers, that are versatile synthetic intermediates for deriving various biologically active compounds. In particular, the thiourea fused γ-amino alcohols showed satisfactory catalytic activity in this reaction and afforded chiral Mannich products in excellent chemical yield (up to 88%) and stereoselectivities (up to syn : anti/93 : 7 dr, up to 99% ee).

New boro amino amide organocatalysts for asymmetric cross aldol reaction of ketones with carbonyl compounds

Distinct types of new boron fused primary amino amide organocatalysts were designed and synthesized from commercially available amino acids. Their catalytic activities were investigated in asymmetric crossed aldol reaction of ketones with aromatic aldehydes to afford the corresponding chiral anti-aldol adducts with good chemical yields, moderate diastereoselectivity and good to excellent enantioselectivities (up to 94% yields, up to 90 : 10 dr, up to 94% ee).

Synthesis and fluorescence properties of 9,9-dimethylfluorene-diyl bridged molecular gyrotops: Effects of slight fluorophore motion on fluorescence efficiency in solid state

The fluorescence of organic molecules has been widely investigated in the development of functional materials. Clarifying the relationship between molecular motion and fluorescence quantum yield (FQY) can aid in developing...

Development of an Internal Calibration Algorithm for Ultrahigh-Resolution Mass Spectra of Dissolved Organic Matter

In order to obtain a spectrum with high mass accuracy, an internal calibration of Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) is inevitable. This in turn is critical for subsequent data processing and is generally performed using the commercial instrument software DataAnalysis in the benchmark calibration mode. However, no methodological study has systemically addressed the automated internal calibration of FTICR-MS spectra for dissolved organic matter (DOM) from different sources such as terrestrial and aquatic environments. In this study, a new piecewise algorithm, FTMSCalibrate, was developed to automatically calibrate FTICR-MS spectra in both positive and negative ion modes. FTMSCalibrate was found to reproduce 91.7% ± 4.4% (referred to as the true positive ratio) of the chemical formulas obtained by calibration using manual DataAnalysis. In addition to significantly reducing the mass error, FTMSCalibrate is more accurate in terms of the molecular formula assignment for low m/z peaks than Formularity and MFAssignR. FTMSCalibrate was compatible with deprotonated ions for FTICR-MS spectra in the negative ion mode as well as protonated and adduct ions, including Na- and K-adducts, for FTICR-MS spectra in the positive ion mode. These results suggest that FTMSCalibrate publicly available herein is a robust alternative for the internal calibration of FTICR-MS spectra during postdata processing and will facilitate DOM analysis by FTICR-MS.

Direct C-H Carboxylation Forming Polyfunctionalized Aromatic Carboxylic Acids by Combined Brønsted Bases

CO₂ fixation into electron-deficient aromatic C-H bonds proceeds with the combined Brønsted bases LiO-t-Bu and LiO-t-Am/CsF/18-crown-6 (t-Am = CEtMe₂) under a CO₂ atmosphere to afford a variety of polyfunctionalized aromatic carboxylic acids.

Formula Assignment Algorithm for Deuterium-Labeled Ultrahigh-Resolution Mass Spectrometry: Implications of the Formation Mechanism of Halogenated Disinfection Byproducts

Ultrahigh-resolution mass spectrometry (UHR-MS) coupled with isotope labeling has attracted significant attention in elucidating the mechanisms of the transformation of dissolved organic matter (DOM). Herein, we developed a novel formula assignment algorithm based on deuterium (D)-labeled UHR-MS, namely, FTMSDeu, for the first time. This algorithm was employed to determine the precursor molecules of halogenated disinfection byproducts (X_n-DBPs) and to evaluate the relative contribution of electrophilic addition and substitution reactions in X_n-DBP formation according to the H/D exchange of DOM molecules. Further, tandem mass spectrometry with homologous-based network analysis was used to validate the formula assignment accuracy of FTMSDeu in the identification of iodinated disinfection byproducts. Electrophilic substitution accounted for 82-98, 71-89, and 43-45% of the formation for Cl-, Br-, and I-containing X_n-DBPs, respectively, indicating the dominant role of the electrophilic substitution in chlorinated disinfection byproducts with low Br and I concentrations. The absence of putative precursors in some X_n-DBPs also suggests that X_n-DBP formation includes secondary reactions (e.g., oxidation and hydrolysis) in addition to the electrophilic addition and/or substitution of halogens. These findings highlight the significance of isotopically labeled UHR-MS techniques in revealing the transformation of DOM in natural and engineered systems.

Enantiodivergent One-Pot Synthesis of Axially Chiral Biaryls Using Organocatalyst-Mediated Enantioselective Domino Reaction and Central-to-Axial Chirality Conversion

Enantiodivergent one-pot synthesis of biaryls was developed using a catalytic amount of a single chiral source. A domino organocatalyst-mediated enantioselective Michael reaction and aldol condensation provided centrally chiral dihydronaphthalenes with excellent enantioselectivity, from which an enantiodivergent chirality conversion from central-to-axial chirality was achieved. Both enantiomers of biaryls were obtained with excellent enantioselectivity. All transformations can be conducted in a single reaction vessel. A plausible reaction mechanism for the enantiodivergence is proposed.

Optimal application of compressive palatal stents following mesiodens removal in pediatric patients: A Randomized Controlled Trial

Background

There is no scientific evidence supporting the choice of a palatal stent in patients who underwent removal of an impacted supernumerary tooth. We aimed to investigate the effects of palatal stents in patients who underwent supernumerary tooth removal through a palatal approach and to suggest the optimal stent thickness and material.

Material and Methods

We recruited 144 patients who underwent extraction of a supernumerary tooth between the maxillary anterior teeth. Subjects were assigned to a control group (CG) or one of four compressive palatal stent groups (CPSGs) classified by the thickness and material of the thermoplastic acrylic stent used. Palatal gingival swelling and objective indices (healing, oral hygiene, gingival, and plaque) were evaluated before surgery and on postoperative days (PODs) 3, 7, and 14; pain/discomfort and the Child Oral Health Impact Profile (COHIP) were assessed as subjective indices of the effects of the stent.

Results

The CPSGs showed faster healing than did the CG on PODs 7 (P<0.001) and 14 (P=0.043); swelling was measured by 1.64±0.88 mm and 4.52±0.39 mm, respectively. Although swelling was least in the 4-mm hard group (0.92±0.33 mm), the difference compared with that in the 2-mm hard group (1.01±0.18 mm) was not significant (P=0.077). The CPSGs showed better COHIP (P<0.001-0.036) and pain scores (P<0.001) than did the CG on PODs 1-3.

Conclusions

Compressive palatal stents reduce discomfort by decreasing pain and alleviating swelling. Although a stent is effective regardless of its thickness and material, 2-mm hard stents maximized such positive effects with minimal discomfort.

Key words:Supernumerary tooth, tooth Extraction, postoperative care, oral Health, pediatric dentistry.

Synthesis of 4,7′-Bibenzo[b]thiophenes Bearing Several Different Substituents at 2-, 2′-, 4′-, and 7-Positions; Structurally Featured Molecular Scaffolds for Selective Substitution

Four isomers of 4,7′-bibenzothiophene scaffolds bearing two different halogen (Br, Cl) and triisopropylsilyl substituents have been synthesized from the two multihalobenzo[b]thiophenes via iodoselective Miyaura borylation reaction using potassium benzoate as a base. Further investigation into the reactivity of 4,7′-bibenzothiophenes in substitution reaction, Suzuki–Miyaura cross-coupling reaction, and C–H direct arylation reaction revealed that tetrasubstituted 4,7′-bibenzothiophenes can be synthesized site- (chemo-) selectively, which are promising novel components for molecular architecture.

Simple amino silyl ether organocatalyst for asymmetric hetero Diels-Alder reaction of isatins with enones

New two catalysts component system comprising of a primary β-amino silyl ethers as an organocatalyst and N-protected amino acids as a co-catalyst put together worked as an efficient organocatalyst system in the hetero Diels-Alder reaction of isatins with enones affording the chiral spirooxindole-tetrahydropyranones in good chemical yields and stereoselectivities (up to 94%, up to dr 78:22., up to 85% ee).

Semipinacol rearrangement of a bicyclo[7.2.0]undecane framework into a bicyclo[6.3.0]undecane skeleton: a model study on the biosynthesis of seiridiasteriscane A

Seiridiasteriscane A is an asteriscane-type sesquiterpenoid bearing a trans-fused bicyclo[6.3.0]undecane skeleton. Although its biosynthesis has been proposed to involve a semipinacol rearrangement of a putative intermediary acetate bearing a bicyclo[7.2.0]undecane ring system (presumably derived from coisolated pestalotiopsin M) followed by epimerization of the resulting cis-fused seiridiasteriscane B, such a type of semipinacol rearrangement has never been reported so far. Our model study revealed that a 1-hydroxybicyclo[7.2.0]undecan-2-yl acetate underwent a smooth and stereospecific semipinacol rearrangement with the assistance of Et2AlCl to give the corresponding bicyclo[6.3.0]undecane-9-one. In addition, the resulting cis-fused 5,8-bicyclic ketone was partially epimerized to the corresponding trans-fused ketone by prolonged adsorption onto a silica gel plate. These results may support a recently proposed biosynthetic pathway of seiridiasteriscane A.

Temperature-Dependent Low-Frequency Vibrations of Thiamine Crystal Containing Hydrated Ions

Low-frequency vibrations of crystalline molecules are very sensitive to the local environment in which the molecules, for example, hydrated ions captured in crystals, find themselves. We present low-temperature X-ray crystallographic measurements on the harvested thiamine crystal containing hydrated ions and its temperature-dependent terahertz spectra and synchrotron infrared microspectra. It is found from the X-ray structure that the hydrated ions and hydration water are in a similar environment to liquid, although those are captured in crystals. The vibrationally resolved THz spectra of two states in the present organic crystals containing hydrated ions are well explained by the difference in the hydrogen-bonded pattern. Peak assignments were performed based on highly accurate first-principles calculations incorporating relativistic effects and dispersion corrections. The temperature dependences are observed for the vibrations around the chloride ions and hydration water due to the loose binding of chloride ions, the bond elongation with increasing temperature, and the cleavage of weak hydrogen bonds.

Synthesis of Stoichiometric SrTiO3 and Its Carrier Doping from Air-Stable Bimetallic Complexes

We demonstrate the synthesis of perovskite oxide SrTiO₃ with ideal cation stoichiometry and homogeneous La doping using air-stable Sr-Ti and La-Ti bimetallic peroxo complexes with a 1:1 cation ratio. Phase-pure SrTiO₃, La₂Ti₂O₇, and LaTiO₃ were successfully synthesized by thermal decomposition of those complexes. La-doped SrTiO₃ was obtained by mixing the Sr-Ti and La-Ti complexes in an acid solution, followed by thermal decomposition. La-doped SrTiO₃ showed systematic chemical trends in the lattice constant and electrical conduction. Not only those bulk polycrystals but also cation-stoichiometric SrTiO₃ epitaxial thin films were grown with an atomically flat surface from the Sr-Ti complex.

New small γ-turn type N-primary amino terminal tripeptide organocatalyst for solvent-free asymmetric aldol reaction of various ketones with aldehydes

New small γ-turn type N-primary amino terminal tripeptides were synthesized and their functionality as an organocatalyst was examined in the asymmetric aldol reaction of various ketones with different aromatic aldehydes under solvent-free neat conditions to afford the desired chiral anti-aldol products in good to excellent chemical yields, diastereoselectivities and enantioselectivities (up to 99%, up to syn : anti/13 : 87 dr, up to 99% ee).

New small γ-turn type N-primary amino terminal tripeptides were applied for the asymmetric aldol reaction of ketones with aldehydes under neat conditions to afford the chiral aldol products (up to 99%, up to syn : anti/13 : 87 dr, up to 99% ee).

Simple primary β-amino alcohols as organocatalysts for the asymmetric Michael addition of β-keto esters to nitroalkenes

Simple primary β-amino alcohols act as an efficient organocatalysts in the asymmetric Michael addition of β-keto esters with nitroalkenes affording highly pure chiral Michael adducts. Also, both enantiomers of the adducts were obtained, depending on the specific catalyst used and reaction temperature.

Stereocontrolled Total Synthesis of (-)-Isocelorbicol and Its Elaboration to Natural Dihydro-β-agarofuran Esters

The first total synthesis of four naturally occurring dihydro-β-agarofuran esters has been accomplished via a highly stereocontrolled 14-step access to their common core triol, (-)-isocelorbicol. A semipinacol rearrangement of an epoxy alcohol to install a quaternary carbon, diastereoselective conjugate reduction of a spirocyclic butenolide for the establishment of a methyl-bearing chiral center, and ring-closing metathesis to construct the decalin ring system were exploited as the key steps for the high-yielding synthesis of (-)-isocelorbicol.

Search for Sub-eV Sterile Neutrinos at RENO

We report a search result for a light sterile neutrino oscillation with roughly 2200 live days of data in the RENO experiment. The search is performed by electron antineutrino (ν[over ¯]_{e}) disappearance taking place between six 2.8 GW_{th} reactors and two identical detectors located at 294 m (near) and 1383 m (far) from the center of the reactor array. A spectral comparison between near and far detectors can explore reactor ν[over ¯]_{e} oscillations to a light sterile neutrino. An observed spectral difference is found to be consistent with that of the three-flavor oscillation model. This yields limits on sin^{2}2θ_{14} in the 10^{-4}≲|Δm_{41}^{2}|≲0.5  eV^{2} region, free from reactor ν[over ¯]_{e} flux and spectrum uncertainties. The RENO result provides the most stringent limits on sterile neutrino mixing at |Δm_{41}^{2}|≲0.002  eV^{2} using the ν[over ¯]_{e} disappearance channel.

Cocrystals of Li+ encapsulated fullerenes and Tb(iii) double-decker single molecule magnet in a quasi-kagome lattice

Cocrystallization of a lithium ion encapsulated fullerene Li⁺@C₆₀ with a terbium(iii) phthalocyaninato porphyrinato double-decker single-molecule magnet [Tb(Pc)(OEP)] is reported. The cocrystal, containing PF₆^- as a counter anion, packs in a quasi-kagome lattice, which leads to intermolecular ferromagnetic interactions as well as the modulation of the single-molecule magnet (SMM) properties.

Development and Application of a High-Precision Algorithm for Nontarget Identification of Organohalogens Based on Ultrahigh-Resolution Mass Spectrometry

Brominated and/or chlorinated organic compounds (referred to as organohalogens) are frequently detected in natural and engineered environments. However, ultrahigh-resolution mass spectrometry (UHR-MS)-based nontargeted identification of organohalogens remains challenging because of the coexistence of a vast number of halogenated and nonhalogenated organic molecules. In this study, a new algorithm, namely, the NOMDBP code, was developed to simultaneously identify organohalogens and non-organohalogens from the UHR-MS spectra of natural and engineered waters. In addition to isotopic patterns, for the first time, three optional filter rules [i.e., selection for minimum nonoxygen heteroatoms, inspection of the presence of newly formed halogenated disinfection byproducts (Xn-DBPs), and of their precursors] were incorporated into our code, which can accurately identify DBP-associated peaks and further elucidate Xn-DBP generation and transformation mechanisms. The formula assignment ratio against 2815 previously reported organohalogens, and their 11,583 isotopologues exceeded 97%. Application of our algorithm to disinfected natural organic matter indicated that oxygen-containing Xn-DBP species accounted for a majority of the Xn-DBPs. Furthermore, brominated Xn-DBPs (Br-DBPs) were characterized by a higher degree of unsaturation compared to chlorinated Xn-DBPs. In addition to electrophilic substitution and electrophilic addition reactions, the decomposition/transformation pathway was found to be another important mechanism in Br-DBP formation. The results of this study highlight the superior potential of our code for the efficient detection of yet unknown organohalogens (including organohalogens bearing nonoxygen heteroatoms) in a nontargeted manner and for the identification of their generation mechanism occurring during the disinfection process.

Evidence for an enolate mechanism in the asymmetric Michael reaction of α,β-unsaturated aldehydes and ketones via a hybrid system of two secondary amine catalysts

The key nucleophile was found to be neither an enamine nor an enol, but an enolate in the direct Michael reaction of α,β-unsaturated aldehydes and non-activated ketones catalyzed by two amine catalysts namely diphenylprolinol silyl ether and pyrrolidine. This is a rare example of an enolate from a ketone serving as a key intermediate in the asymmetric organocatalytic reaction involving secondary amine catalysts because the ketone enolates are generally generated using a strong base, and the enamine is a common nucleophile in this type of reaction.

The key nucleophile was found to be neither an enamine nor an enol, but an enolate in the direct Michael reaction of α,β-unsaturated aldehydes and non-activated ketones catalyzed by two amine catalysts namely diphenylprolinol silyl ether and pyrrolidine.

Self-assembly of photoresponsive azo-containing phospholipids with a polar group as the tail

Vesicles or micelles prepared from amphiphiles with azobenzene (Az) moieties and long alkyl chains have attracted much attention in drug delivery systems. To induce release behavior from smart carriers via trans–cis photoisomerization of the Az groups, UV light exposure is typically used, but it can damage DNA and hardly penetrates cells. In this paper, Az-containing phospholipids without long alkyl tails were designed and synthesized; in these compounds, the end group of the Az moiety was substituted with a –NO₂ and –OCH₃ group (abbreviated N6 and M6, respectively). N6 self-assembled into H-aggregates with an interdigitated bilayered structure in water through the antiparallel orientation due to π–π interactions of the Az group, the attractive van der Waals forces, and the interactions and bending behavior of the phosphocholine groups. Vesicles showing visible light stimuli-responsive behavior were obtained by mixing N6 and M6, and the release of encapsulated calcein was triggered by visible light.

A mixture of a nitro- and methoxy-substituted azo-containing phospholipids without long alkyl tails formed vesicles showing visible light stimuli-responsive behavior. Release of encapsulated calcein from the vesicles was triggered by visible light.

Data on synthesis and characterization of new p-nitro stilbene Schiff bases derivatives as an electrochemical DNA potential spacer

The structural investigation of synthesized compounds can be carried out by various spectroscopic techniques. It is an important prospect in order to elucidate the structure of the desired products before being further utilized. The preparation of new p-nitro stilbene Schiff base derivatives as an electrochemical DNA potential spacer was synthesized using (E)-4-(4-nitrostyryl)aniline from Heck reaction with aldehydes in ethanolic solution. The data presented here in this article contains FTIR, UV-Vis and ¹H and ¹³C NMR of (E)-4-(4-nitrostyryl)aniline and nitrostyryl aniline derivatives.

Inversion of the Axial Information during Oxidative Aromatization in the Synthesis of Axially Chiral Biaryls with Organocatalysis as a Key Step

Invited for the cover of this issue is the group of Yujiro Hayashi at the University of Tohoku University. The image depicts the spinning motion of a figure skater, which illustrates the transformation of the chiral information investigated in this work. Read the full text of the article at 10.1002/chem.201905814.

Simple organocatalyst component system for asymmetric hetero Diels–Alder reaction of isatins with enones

A simple two catalyst component system consisting of primary β-amino alcohols as a catalyst and amino acids as a co-catalyst put together works as an efficient organocatalyst system in the hetero Diels–Alder reaction of isatins with enones to afford the chiral spirooxindole–tetrahydropyranones in good chemical yields and stereoselectivities (up to 86%, up to 85 : 15 dr., up to 95% ee).

A simple two catalysts component system of β-amino alcohols (catalyst) and amino acids (co-catalyst) works as an efficient organocatalysts in hetero Diels–Alder reaction of isatins with enones to afford chiral spirooxindole-tetrahydropyranones.

Gear Slippage in Molecular Bevel Gears Bridged with a Group 14 Element

Ditriptycilmethanes are known as molecular bevel gears because the two triptycil groups show correlated rotation. In this report, molecular bevel gears bridged with a group 14 element, bis(methyltriptycil)X (X = SiH₂, GeH₂, GeF₂), were synthesized, and their gearing properties were investigated. Gear slippage, that is an error in gear rotation, is observed in high-temperature solutions of molecular bevel gears. Heavy atom derivatives undergo gear slippage more easily due to the long bond lengths and wide angles between the two triptycil units and the bridging group 14 element. Activation energies of gear slippages were estimated by temperature-dependent NMR spectroscopy and DFT calculations, and theoretical thermodynamic parameters for gear slippage were found to be in excellent agreement with experimental values. The results indicate that theoretical calculations for gear rotation in molecular bevel gears can accurately reproduce experimental phenomena.

Kinetic Stabilization of Carbazole Nitroxides by Inclusion in a Macrocage and Their Electron Spin Resonance Characterization

Some nitroxides, for example, tetramethylpyridiniumoxide, are known as stable radicals; however, carbazole nitroxide is less stable. The kinetic stabilization of labile radicals by introduction of bulky substituents is usually effective to investigate intrinsic properties of the molecule because of small electronic perturbation induced by the substituents. In this study, macrocage molecules with a carbazole nitroxide connected by covalent bonds were newly designed as kinetically stabilized carbazole nitroxides. The nitroxides were prepared and characterized by electron spin resonance spectroscopy. The caged nitroxides presented long half-lives (∼50 h) by kinetic analysis.

Synthesis and Stereochemical Revision of the Aromatic Polyketide NFAT-133

NFAT-133, isolated from Streptomyces sp., is an immunosuppressive, antidiabetic, and antitrypanosomal aromatic polyketide with three contiguous stereocenters. The first enantioselective total synthesis of the proposed structure of NFAT-133 [(10R,11R,12S)-1] and its C10 epimer [(10S,11R,12S)-1] was achieved from a known aromatic ester (5) by a 10-step sequence that featured chiral auxiliary-directed asymmetric alkylation and the Evans asymmetric aldol reaction as the chirality-inducing steps. The ¹H and ¹³C NMR data as well as the specific rotation value of natural NFAT-133 were not identical to those of the proposed structure, but were in good agreement with those of its C10 epimer. This led us to conclude that the absolute configuration of NFAT-133 should be revised to 10S, 11R, and 12S.

The thermodynamic properties and molecular dynamics of [Li+@C60](PF6-) associated with structural phase transitions

Calorimetric and terahertz-far-infrared (THz-FIR) spectroscopic and infrared (IR) spectroscopic measurements were conducted for [Li+@C60](PF6-) at temperatures between 1.8 and 395 K. [Li+@C60](PF6-) underwent a structural phase transition at around 360 K accompanied by the orientational order-disorder transition of Li+@C60 and PF6-. The transition occurred in a step-wise manner. The total transition entropy (ΔtrsS) of 40.1 ± 0.4 J K-1 mol-1 was smaller than that of the orientational order-disorder transition in a pristine C60 crystal (ΔtrsS = 45.4 ± 0.5 J K-1 mol-1). Thus, the orientational disorder of Li+@C60 in the high-temperature phase of [Li+@C60](PF6-) was much less excited than that of the pristine C60 owing to the Coulombic interactions, which stabilized the ionic crystal lattice of [Li+@C60](PF6-). At T < 100 K, upon cooling, Li+ ions were trapped in two pockets on the inner surface of C60, and no phase transition was observed. Finally, the Li+ ions achieved a complete order at 24 K through antiferroelectric transition. The ΔtrsS value of 4.6 ± 0.4 J K-1 mol-1 was slightly smaller than R ln 2 = 5.76 J K-1 mol-1 expected for the two-site order-disorder transition. The extent of the Li+ motion in the C60 cage was related to the selection rule in the THz-FIR and IR spectroscopy of the C60 internal vibrations, because a C60 cage should be polarized by the Li+ ion. It is shown that the local symmetry of the caged molecule can be modified by the rotational or hopping motion of the encaged ions.

Fuel-Composition Dependent Reactor Antineutrino Yield at RENO

We report a fuel-dependent reactor electron antineutrino (ν[over ¯]_{e}) yield using six 2.8 GW_{th} reactors in the Hanbit nuclear power plant complex, Yonggwang, Korea. The analysis uses 850 666 ν[over ¯]_{e} candidate events with a background fraction of 2.0% acquired through inverse beta decay (IBD) interactions in the near detector for 1807.9 live days from August 2011 to February 2018. Based on multiple fuel cycles, we observe a fuel ^{235}U dependent variation of measured IBD yields with a slope of (1.51±0.23)×10^{-43}  cm^{2}/fission and measure a total average IBD yield of (5.84±0.13)×10^{-43}  cm^{2}/fission. The hypothesis of no fuel-dependent IBD yield is ruled out at 6.6σ. The observed IBD yield variation over ^{235}U isotope fraction does not show significant deviation from the Huber-Mueller (HM) prediction at 1.3 σ. The measured fuel-dependent variation determines IBD yields of (6.15±0.19)×10^{-43} and (4.18±0.26)×10^{-43}  cm^{2}/fission for two dominant fuel isotopes ^{235}U and ^{239}Pu, respectively. The measured IBD yield per ^{235}U fission shows the largest deficit relative to the HM prediction. Reevaluation of the ^{235}U IBD yield per fission may mostly solve the reactor antineutrino anomaly (RAA) while ^{239}Pu is not completely ruled out as a possible contributor to the anomaly. We also report a 2.9 σ correlation between the fractional change of the 5 MeV excess and the reactor fuel isotope fraction of ^{235}U.