23 research outputs found
Radical <i>ipso</i>-Substitution of a Carbon–Fluorine Bond Leading to Fluoro-7-azaindolines and Fluoro-7-azaindoles
Rare
examples of a synthetically useful radical <i>ipso</i>-substitution
of a carbon–fluorine bond are reported, leading
to highly functionalized 5,6-difluoro-7-azaindolines. An unexpected
hydrogen atom translocation and fragmentation with loss of molecular
nitrogen and formation of a nitrile were observed in the case of an <i>N</i>-benzyl-tetrazole derivative
Expedient Approach to Novel N‑Unprotected Bicyclic Azapyrimidine and Pyridine Structures
A direct route to novel bicyclic <i>N</i>-unprotected azapyrimidine structures including fused five-, six-, and seven-membered rings is described involving radical addition and cyclization of xanthates; this approach could be partially extended to pyridines
Base-Promoted Protodeboronation of 2,6-Disubstituted Arylboronic Acids
Facile
based promoted deboronation of electron-deficient arylboronate
esters was observed for arylboronates containing two ortho electron-withdrawing
group (EWG) substituents. Among 30 representative boronates, only
the diortho-substituted species underwent facile C–B fission
in aqueous basic conditions (200 mM hydroxide). These results provide
fundamental insight into deboronative mechanisms with implications
for cross-coupling reactions, regioselective deuteration/tritiation
for isotopic labeling, and the design of new <sup>18</sup>F-trifluoroborate
radioprosthetics
Desulfonylative Radical Ring Closure onto Aromatics. A Modular Route to Benzazepin-2-ones and 5-Arylpiperidin-2-ones
Adducts from the intermolecular radical addition of <i>N</i>-xanthylacetyl-<i>N</i>-methanesulfanilides to Boc-protected allylamine undergo ring closure with loss of a methanesulfonyl radical to give benzazepin-2-ones. Upon deprotection and exposure to triethylamine, these compounds rearrange into 5-aryl-2-piperidones. This approach also represents a useful route to benzazepin-2-ones unsubstituted on the nitrogen atom of the azepinone ring
Imaging in a 3-year-old boy with PA-VSD.
<p>3D Volume-rendered image with electronic dissection, which remove contrast from the cardiac chambers, shows the defect (*) in ventricle septum (VS) and the overriding aorta (<50%). AAo indicates ascending aorta.</p
The diagnostic algorithm used for patients with PA-VSD.
<p>The diagnostic algorithm used for patients with PA-VSD.</p
MDCT in a 4-year-old boy with PA-VSD.
<p>(a) Axial CT shows the patients has patent ductus arteriosus(*). Some MAPCAs (white arrow) from the descending aorta (DAo) to the right lung. (b) Axial CT demonstrates good-sized right pulmonary artery (RPA) and left pulmonary artery(LPA). The orifice of a MAPCA (#) is depicted clearly. (c) 3D Volume-rendered image (posterior view) shows a MAPCA (white arrowhead) from the descending aorta to the right lung.</p
NiPS<sub>3</sub> Nanosheet–Graphene Composites as Highly Efficient Electrocatalysts for Oxygen Evolution Reaction
Developing new electrocatalysts
is essentially important for efficient
water splitting to produce hydrogen. Two-dimensional (2D) materials
provide great potential for high-performance electrocatalysts because
of their high specific surface area, abundant active edges, and tunable
electronic structure. Here, we report few-layer NiPS<sub>3</sub> nanosheet–graphene
composites for high-performance electrocatalysts for oxygen evolution
reaction (OER). The pure NiPS<sub>3</sub> nanosheets show an overpotential
of 343 mV for a current density of 10 mA cm<sup>–2</sup>, which
is comparable to that for IrO<sub>2</sub> and RuO<sub>2</sub> catalysts.
More importantly, the NiPS<sub>3</sub> nanosheet–graphene composites
show significantly improved OER activity due to the synergistic effect.
The optimized composite shows a very low overpotential of 294 mV for
a current density of 10 mA cm<sup>–2</sup>, 351 mV for a current
density of 100 mA cm<sup>–2</sup>, a small Tafel slope of 42.6
mV dec<sup>–1</sup>, and excellent stability. These overall
performances are far better than those of the reported 2D materials
and even better than those of many traditional materials even at a
much lower mass loading of NiPS<sub>3</sub>
Activating TiO<sub>2</sub> Nanoparticles: Gallium-68 Serves as a High-Yield Photon Emitter for Cerenkov-Induced Photodynamic Therapy
The classical photodynamic
therapy (PDT) requires external light to activate photosensitizers
for cancer treatment. However, limited tissue penetration of light
has been a long-standing challenge for PDT to cure malignant tumors
in deep tissues. Recently, Cerenkov radiation (CR) emitted by radiotracers
such as <sup>18</sup>F-fluorodeoxyglucose (<sup>18</sup>F-FDG) has
become an alternative and promising internal light source. Nevertheless,
fluorine-18 (F-18) only releases 1.3 photons per decay in average;
consequently, injection dose of F-18 goes beyond 10–30 times
more than usual to acquire therapeutic efficacy because of its low
Cerenkov productivity. Gallium-68 (Ga-68) is a favorable CR source
owing to its ready availability from generator and 30-time higher
Cerenkov productivity. Herein, we report, for the first time, the
use of Ga-68 as a CR source to activate dextran-modified TiO<sub>2</sub> nanoparticles (D-TiO<sub>2</sub> NPs) for CR-induced PDT. Compared
with <sup>18</sup>F-FDG, <sup>68</sup>Ga-labeled bovine serum albumin
(<sup>68</sup>Ga-BSA) inhibited the growth of 4T1 cells and exhibited
significantly stronger DNA damage to tumor cells. In vivo studies
showed that the tumor growth was almost completely inhibited when
tumor-bearing mice were treated with a combination of D-TiO<sub>2</sub> NPs and <sup>68</sup>Ga-BSA. This study proved that Ga-68 is a more
potent radionuclide for PDT than F-18 both in vitro and in vivo offered
a promising strategy of using a diagnostic dose of radioactivity to
achieve depth-independent cancer therapy without using any external
light source
<sup>18</sup>F‑Alanine Derivative Serves as an ASCT2 Marker for Cancer Imaging
Amino
acids derivative are well established molecular probes for
diagnosis of a variety of cancer using positron emission tomography
(PET). Recently, boramino acid (BAAs) was found as a prospective molecular
platform for developing PET tracer. The objective of this study was
to develop a <sup>18</sup>F-labeled alanine derivative through displacing
its carboxylate by trifluoroborate as a selective ASCT2 marker for
cancer imaging. <sup>18</sup>F-Ala-BF<sub>3</sub> was first evaluated
in healthy FVB/N mice <i>in vivo</i>, exhibiting rapid renal
clearance with almost negligible uptake in stomach (1.53 ± 0.31%ID/g).
Notable uptake was observed in thyroid (3.71 ± 0.49%ID/g, 40
min post injection), of which the uptake was significantly inhibited
by co-injection with natural L-alanine. In addition, we further established <sup>18</sup>F-Ala-BF<sub>3</sub> on a human gastric cancer cell (BGC-823)
xenografts bearing mouse model. Dynamic PET-CT scan revealed the optimal
time window for tumor imaging, it was between 40 and 60 min post injection,
when the BGC-823 xenografts uptake was 5.49 ± 1.47%ID/g (<i>n</i> = 4), and the tumor-to-stomach, tumor-to-blood, tumor-to-muscle,
and tumor-to-brain ratios were 3.27 ± 1.53, 3.80 ± 1.48,
3.47 ± 1.48, and 6.20 ± 1.47, respectively