17 research outputs found
Controlled Ring-Opening of SiloxyÂdifluoroÂcycloÂpropanes for Carbocyclization: Synthesis of DifluoroÂcycloÂpentenones
A highly controlled ring opening
of siloxyÂdifluoroÂcycloÂpropanes,
formed by <i>n</i>BuN<sub>4</sub>Br-catalyzed difluorocycloÂpropanation
of methyl vinyl ketones bearing a β-alkylthio group by using
TMSCF<sub>2</sub>Br as a unique difluorocarbene source, results in
metal difluoroÂhomoenolates with assistance of copper or silver
followed by an intramolecular addition and elimination reaction leading
to α-<i>gem</i>-difluorocyclopentenones efficiently
Additional file 1 of GGT5 facilitates migration and invasion through the induction of epithelial–mesenchymal transformation in gastric cancer
Supplementary Material 1
Ring-Opening Diarylation of Siloxydifluorocyclopropanes by Ag(I) Catalysis: Stereoselective Construction of 2‑Fluoroallylic Scaffold
A silver-catalyzed, defluorination
ring-opening diarylation of
siloxy 2,2-difluorocyclopropanes, with two arenes, to directly prepare
polysubstituted 2-fluoroallylic compounds, is described. This multicomponent
reaction proceeds smoothly in good stereoselectivity, which is due
to a chelation-controlled addition of arenes to α-fluorinated
ketone intermediate
Lateral-Size-Mediated Efficient Oxygen Evolution Reaction: Insights into the Atomically Thin Quantum Dot Structure of NiFe<sub>2</sub>O<sub>4</sub>
The
study of high-performance electrocatalysts for driving the
oxygen evolution reaction (OER) is important for energy storage and
conversion systems. As a representative of inverse-spinel-structured
oxide catalysts, nickel ferrite (NiFe<sub>2</sub>O<sub>4</sub>) has
recently gained interest because of its earth abundance and environmental
friendliness. However, the gained electrocatalytic performance of
NiFe<sub>2</sub>O<sub>4</sub> for the OER is still far from the state-of-the-art
requirements because of its poor reactivity and finite number of surface
active sites. Here, we prepared a series of atomically thin NiFe<sub>2</sub>O<sub>4</sub> catalysts with different lateral sizes through
a mild and controllable method. We found that the atomically thin
NiFe<sub>2</sub>O<sub>4</sub> quantum dots (AT NiFe<sub>2</sub>O<sub>4</sub> QDs) show the highest OER performance with a current density
of 10 mA cm<sup>–2</sup> at a low overpotential of 262 mV and
a small Tafel slope of 37 mV decade<sup>–1</sup>. The outstanding
OER performance of AT NiFe<sub>2</sub>O<sub>4</sub> QDs is even comparable
to that of commercial RuO<sub>2</sub> catalyst, which can be attributed
to its high reactivity and the high fraction of active edge sites
resulting from the synergetic effect between the atomically thin thickness
and the small lateral size of the atomically thin quantum dot (AT
QD) structural motif. The experimental results reveal a negative correlation
between lateral size and OER performance in alkaline media. Specifically
speaking, the number of low-coordinated oxygen atoms increases with
decreasing lateral size, and this leads to significantly more oxygen
vacancies that can lower the adsorption energy of H<sub>2</sub>O,
increasing the catalytic OER efficiency of AT NiFe<sub>2</sub>O<sub>4</sub> QDs
Comparative Study of Homogeneous and Heterogeneous Photocatalytic Degradation of RhB under Visible Light Irradiation with Keggin-Type Manganese-Substituted Catalysts
This paper reported for the first
time a comparative study of the photocatalytic activity of the Keggin-type
MnÂ(II)-substituted heteropolyanion PW<sub>11</sub>O<sub>39</sub>Mn<sup>II</sup>(H<sub>2</sub>O)<sup>5–</sup> (PW<sub>11</sub>Mn)
and its heterogeneous system PW<sub>11</sub>Mn/D301R through the degradation
of rhodamine B (RhB) under visible light irradiation. A novel photocatalytic
mechanism was suggested, and an interaction between PW<sub>11</sub>Mn and RhB was scrutinized by using visible absorption spectrum and
fluorescence emission spectrum. Influences of some factors such as
the RhB initial concentration, the PW<sub>11</sub>Mn concentration,
the PW<sub>11</sub>Mn/D301R dosage, the solution pH, and different
anions existing in solution on the photocatalytic degradation rate
of RhB were also examined. The stability of PW<sub>11</sub>Mn/D301R
was evaluated by the cycle photodegradation of RhB in the end. The
experimental results showed that 100% of RhB degradation was reached
at 100 min for the PW<sub>11</sub>Mn system and 40 min for the PW<sub>11</sub>Mn/D301R system when the solution containing 10 μmol·L<sup>–1</sup>RhB was exposed to visible light. The hydroxyl radicals
were responsible for the destruction of dye. The photocatalysis mechanism
was different from that of both semiconductor and Keggin parent catalysts.
An electrostatic interaction and a coordination interaction between
PW<sub>11</sub>Mn and RhB occurred simultaneously in an acidic aqueous
solution. The coordination interaction slowed significantly the RhB
degradation, but became weak obviously after PW<sub>11</sub>Mn was
adsorbed onto the D301R resin. The influence of anions existing in
solution on the RhB degradation followed the sequence of PO<sub>4</sub><sup>3–</sup> > SO<sub>4</sub><sup>2–</sup>>
Cl<sup>–</sup>> NO<sub>3</sub><sup>–</sup>. No matter
if in neutral or in acidic aqueous solution, the photocatalyst PW<sub>11</sub>Mn/D301R was stable
Bipoladien A, a Sesterterpenoid Containing an Undescribed 5/8/5/7 Carbon Skeleton from Bipolaris maydis
Bipoladiens A–E (1–5), five
new ophiobolin-derived
sesterterpenoids, and a known compound 6 (bipolaricin
R) were isolated from the cultures of the phytopathogenic fungus Bipolaris maydis. Their structures and absolute configurations
were elucidated based on comprehensive spectroscopic analyses, HRESIMS,
electronic circular dichroism (ECD) calculations, and single-crystal
X-ray diffraction analyses. Notably, compound 1 has an
undescribed tetracyclic 5/8/5/7 fused carbon skeleton, and compound 2 possesses a rare multicyclic caged ring system. The biosynthetic
pathway of 1 was proposed starting from 6 via a series of oxidation and cyclization reactions. Compound 6 showed excellent antiproliferation and apoptosis induction
effects against A549 cell line. Additionally, compounds 5 and 6 exhibited noticeable antimicrobial ability against Bacillus cereus, Staphylococcus aureus, and Staphylococcus epidermidis. These
findings not only developed the chemical and bioactivities diversities
of ophiobolin-sesterterpenoid but also provided an idea to boost the
application of natural products in the control of food pathogens
Bipoladien A, a Sesterterpenoid Containing an Undescribed 5/8/5/7 Carbon Skeleton from Bipolaris maydis
Bipoladiens A–E (1–5), five
new ophiobolin-derived
sesterterpenoids, and a known compound 6 (bipolaricin
R) were isolated from the cultures of the phytopathogenic fungus Bipolaris maydis. Their structures and absolute configurations
were elucidated based on comprehensive spectroscopic analyses, HRESIMS,
electronic circular dichroism (ECD) calculations, and single-crystal
X-ray diffraction analyses. Notably, compound 1 has an
undescribed tetracyclic 5/8/5/7 fused carbon skeleton, and compound 2 possesses a rare multicyclic caged ring system. The biosynthetic
pathway of 1 was proposed starting from 6 via a series of oxidation and cyclization reactions. Compound 6 showed excellent antiproliferation and apoptosis induction
effects against A549 cell line. Additionally, compounds 5 and 6 exhibited noticeable antimicrobial ability against Bacillus cereus, Staphylococcus aureus, and Staphylococcus epidermidis. These
findings not only developed the chemical and bioactivities diversities
of ophiobolin-sesterterpenoid but also provided an idea to boost the
application of natural products in the control of food pathogens
Cytotoxicity of MPLs and drug-loaded TAT-MPLs measured using MTT assays after.
<p>(A) 12, (B) 24, and (C) 48 h incubation with bEnd.3 cells. (GSH: glutathione, HES: hesperidin, NAR: naringin).</p
Flow cytometry analysis of bEnd.3 cells.
<p>Cells incubated with free FITC and QDs (1), MPLs (2), and TAT-MPLs (3) for 0.5 h, 3 h and 12 h at a NP concentration of 20 µg/mL. The NPs were labeled with FITC. The FITC (A and B) and QD fluorescence intensity (C and D) are shown.</p
Physical characterization of TAT-conjugated MPLs.
<p>Physical characterization of TAT-conjugated MPLs.</p