Dehydrative Direct CH Allylation with Allylic Alcohols under [Cp*CoIII] Catalysis

The unique reactivity of [Cp*Co^III] over [Cp*Rh^III] was demonstrated. A cationic [Cp*Co^III] catalyst promoted direct dehydrative C? H allylation with non‐activated allyl alcohols, thus giving C2‐allylated indoles, pyrrole, and phenyl‐pyrazole in good yields, while analogous [Cp*Rh^III] catalysts were not effective. The high γ‐selectivity and C2‐selectivity indicated that the reaction proceeded by directing‐group‐assisted C? H metalation. DFT calculations suggested that the γ‐selective substitution reaction proceeded by C? H metalation and insertion of a C? C double bond, with subsequent β‐hydroxide elimination. The [Cp*Co^III] catalyst favored β‐hydroxide elimination over β‐hydride elimination.     

Biomimetic synthesis of grandione from demethylsalvicanol via hetero-Diels-Alder type dimerization and structure revision of grandione

Grandione, a unique isetexane diterpene dimer, was synthesized from demethylsalvicanol via the solid state hetero-Diels-Alder type dimerization reaction. By X-ray crystallography, grandione was determined to have the structure, in which the two isopropyl groups on the two monomer units are arranged syn. Grandione and some of its analogues showed a moderate cytotoxity on P388 murine leukemia cells.     

Dissection of the Catalytic Mechanisms of Transmembrane Terpene Cyclases Involved in Fungal Meroterpenoid Biosynthesis

Pyr4-family terpene cyclases are noncanonical transmembrane terpene cyclases involved in the biosynthesis of microbial meroterpenoids and catalyze diverse cyclization reactions. Despite the ubiquity of Pyr4-family terpene cyclases in microorganisms, their three-dimensional structures have never been experimentally determined. Herein, we focused on AdrI, the Pyr4-family enzyme for the andrastin A pathway, and its homologues, and performed a series of mutational experiments using their AlphaFold2-generated structures. Intriguingly, we found that AdrI and InsA7, which both accept the same substrate, use different amino acid residues for the initiation of the cyclization cascade. Furthermore, we obtained several AdrI variants with altered product selectivity, one of which dominantly yielded a new meroterpenoid species. Collectively, our study provides important insights into the catalytic functions of Pyr4-family terpene cyclases and will facilitate the engineering of these enzymes.     

Anomeric information obtained from a series of synthetic trisaccharides using energy resolved mass spectra

The majority of structural investigations of oligosaccharides based on mass spectrometry use naturally occurring oligosaccharides, which do not allow extracting any common feature associated with anomeric structures and linkage positions. In order to address the issue to find such characteristics possibly contained in oligosaccharide structure, a synthetic combinatorial trisaccharide library was analyzed. The trisaccharides used in the analysis consisted of L-fucose, D-galactose and D-glucose, in which individual glycosidic linkages existed in either alpha- or beta-anomers. The analysis of energy-resolved mass spectra (ERMS) and the scattered plot analysis of some parameters obtained from ERMS for a series of trisaccharides revealed that lower activation energy was required for the dissociation of alpha-glycosides of these sugars compared to those of the corresponding beta-anomers. It is suggested that this finding may be useful in structural analysis of natural oligosaccharides.     

Synthesis and electrochemical properties of nanostructured LiAl x Mn2 − x O4 − y Br y particles

Nanostructured LiAl _x Mn_2 − x O_4 − y Br _y particles were synthesized successfully by annealing the mixed precursors, which were prepared by room-temperature solid-state coordination method using lithium acetate, manganese acetate, lithium bromide, aluminum nitrate, citric acid, and polyethylene glycol 400 as starting materials. X-ray diffractometer patterns indicated that the particles of the as-synthesized samples are well-crystallized pure spinel phase. Transmission electron microscopy images showed that the LiAl _x Mn_2 − x O_4 − y Br _y samples consist of small-sized nanoparticles. The results of galvanostatic cycling tests revealed that the initial discharge capacity of LiAl_0.05Mn_1.95O_3.95Br_0.05 is 119 mAh g⁻¹; after the 100th cycle, its discharge capacity still remains at 92 mAh g⁻¹. The introduction of Al and Br in LiMn₂O₄ bring a synergetic effect and is quite effective in increasing the capacity and elevating cycling performance.     

Mg-catalyzed enantioselective benzylic C-H bond functionalization of isoindolinones: addition to imines

Access to chiral isoindolinones: The Mg-catalyzed enantioselective benzylic C-H bond functionalization of isoindolinones is described. A Bu(2) Mg/Schiff base catalyst (1:1) promoted the enantioselective addition of N-Boc-isoindolinones to aryl, heteroaryl, alkenyl, and alkyl imines, giving 3-substituted isoindolinones in 84-99?%?ee and 50:50-91:9?d.r. (see scheme).     

Oxygen evolution on SrFeO3 electrode

Oxygen evolution reactions on SrFeO₃ were investigated in alkaline and acidic solutions. It was found that the catalytic activity for the oxygen evolution reaction in the alkaline solution is high. The following reaction steps (V)+Fe+2H₂O→(O)+FeOH₂+2H⁺+2e^? in acidic solution and FeOH+OH^?→FeO^?+H₂O in alkaline solution are presumed to be rate-controlling in the anodic evolution of oxygen on SrFeO₃ electrode, where (V) denotes oxygen vacancy on the electrode surface. The reaction mechanism and the catalytic property are discussed in connection to the band structure of the oxide.     

Preparation and characterization of LiMn2-yCoyO4 spinels by low heating solid state coordination method

Cathode material LiMn2-yCoyO4 spinels were prepared by annealing the mixed precursors, which were synthesized by a low heating solid state coordination method using lithium acetate, manganese acetate, cobalt acetate, and oxalic acid as original materials. The structures and morphologies of the LiMn2-yCoyO4 spinels were investigated as a function of annealing temperature and time. The results showed that all samples in different annealing temperature and time had the same spinel structure. There were some growth and agglomeration in the particles when annealing temperature increased from 450 to 650 degrees C. And the crystal structure was more perfect at the upper temperature. In addition, the electrochemical properties of LiMn2-yCoyO4 spinels used as cathode material for lithium-ion batteries were studied in detail in this paper.     

A two-dimensional molecular network structure of trimesic acid prepared by adsorption-induced self-organization

A two-dimensional molecular network of trimesic acid on Au(111) was visualized by in situ scanning tunneling microscopy with submolecular resolution. The supramolecular structures including an 'order to order' phase transition were constructed by precise potential-controlled adsorption based on adsorption-induced self-organization.     

Radiation-induced chemical evolution of biomolecules

Chemical evolution in glycilglycine (Gly2) films irradiated with 146 nm vacuum ultraviolet light was studied. It is found that quantum efficiency of chemical evolution from Gly2 to glycilglycilglycine (Gly3) is smaller than that to glycilglycilglycilglycine (Gly4) due to the multiple step of reaction. Furthermore, we have carried out measurement of soft X-ray natural circular dichroism spectra for serine and alanine films in the energy region of oxygen 1s transition and we report the splitting of 1s→π* transitions.