7 research outputs found
Oxidatively Stable Polyolefin Thermoplastics and Elastomers for Biomedical Applications
Statistical
copolymers were prepared by the Ring Opening Metathesis
coPolymerization (ROMP) of (<i>Z</i>)-5,5-dimethylcyclooct-1-ene
and <i>cis</i>-cyclooctene. Subsequent hydrogenation yielded
polyÂ(ethylene-<i>co</i>-isobutylene) (PEIB) materials. The
feed ratio of the comonomers controls the degree of branching and
resulting thermal and mechanical properties of the PEIB samples. Oxidative
degradation studies, conducted under accelerated in vitro conditions
were used to assess and predict their long-term biostability. Relative
to commercial polyÂ(ether urethanes) and a structurally similar polyolefin,
polyÂ(ethylene-<i>co</i>-1-butylene), the PEIB samples showed
much better oxidative resistance. The facile synthesis, improved stability,
and excellent mechanical performance of these PEIB materials bode
well for their use in biomedical applications that require long-term
biostability
Soft Propargylic Deprotonation: Designed Ligand Enables Au-Catalyzed Isomerization of Alkynes to 1,3-Dienes
By functionalizing the privileged
biphenyl-2-ylphosphine with a
basic amino group at the rarely explored 3′ position, the derived
goldÂ(I) complex possesses orthogonally positioned “push”
and “pull” forces, which enable for the first time soft
propargylic deprotonation and permit the bridging of a difference
of >26 p<i>K</i><sub>a</sub> units (in DMSO) between
a propargylic
hydrogen and a protonated tertiary aniline. The application of this
design led to efficient isomerization of alkynes into versatile 1,3-dienes
with synthetically useful scope under mild reaction conditions
Formal Synthesis of 7-Methoxymitosene and Synthesis of its Analog via a Key PtCl<sub>2</sub>-Catalyzed Cycloisomerization
A formal synthesis of 7-methoxymitosene is achieved via a key platinum-catalyzed cycloisomerization. The precursor for the Pt catalysis, a fully functionalized benzene intermediate, was prepared via a regioselective electrophilic bromination followed by a chemoselective Sonogashira cross-coupling. It underwent the PtCl<sub>2</sub>-catalyzed cycloisomerization smoothly despite its hindered and highly electron-rich nature. Analogs of 7-methoxymitosene can be accessed in an expedient manner by following a similar synthetic sequence
Experimental and Computational Evidence for Gold Vinylidenes: Generation from Terminal Alkynes via a Bifurcation Pathway and Facile C–H Insertions
Facile cycloisomerization of (2-ethynylphenyl)Âalkynes
is proposed
to be promoted synergistically by two molecules of BrettPhosAuNTf<sub>2</sub>, affording tricyclic indenes in mostly good yields. A gold
vinylidene is most likely generated as one of the reaction intermediates
on the basis of both mechanistic studies and theoretical calculations.
Different from the well-known Rh, Ru, and W counterparts, this novel
gold species is highly reactive and undergoes facile intramolecular
CÂ(sp<sup>3</sup>)–H insertions as well as O–H and N–H
insertions. The formation step for the gold vinylidene is predicted
theoretically to be complex with a bifurcated reaction pathway. A pyridine <i>N</i>-oxide acts as a weak base to facilitate the formation
of an alkynylgold intermediate, and the bulky BrettPhos ligand in
the gold catalyst likely plays a role in sterically steering the reaction
toward formation of the gold vinylidene
Experimental and Computational Evidence for Gold Vinylidenes: Generation from Terminal Alkynes via a Bifurcation Pathway and Facile C–H Insertions
Facile cycloisomerization of (2-ethynylphenyl)Âalkynes
is proposed
to be promoted synergistically by two molecules of BrettPhosAuNTf<sub>2</sub>, affording tricyclic indenes in mostly good yields. A gold
vinylidene is most likely generated as one of the reaction intermediates
on the basis of both mechanistic studies and theoretical calculations.
Different from the well-known Rh, Ru, and W counterparts, this novel
gold species is highly reactive and undergoes facile intramolecular
CÂ(sp<sup>3</sup>)–H insertions as well as O–H and N–H
insertions. The formation step for the gold vinylidene is predicted
theoretically to be complex with a bifurcated reaction pathway. A pyridine <i>N</i>-oxide acts as a weak base to facilitate the formation
of an alkynylgold intermediate, and the bulky BrettPhos ligand in
the gold catalyst likely plays a role in sterically steering the reaction
toward formation of the gold vinylidene
Table_1_The clinical efficacy and safety of different biliary drainage in malignant obstructive jaundice: a meta-analysis.docx
BackgroundCurrently, percutaneous transhepatic cholangial drainage (PTCD) and endoscopic retrograde cholangiopancreatography (ERCP) are commonly employed in clinical practice to alleviate malignant obstructive jaundice (MOJ). Nevertheless, there lacks a consensus regarding the superiority of either method in terms of efficacy and safety.AimTo conduct a systematic evaluation of the effectiveness and safety of PTCD and ERCP in treating MOJ, and to compare the therapeutic outcomes and safety profiles of these two procedures.MethodsCNKI, VIP, Wanfang, CBM, PubMed, Web of Science, Embase, The Cochrane Library, and other databases were searched for randomized controlled trials (RCTs) on the use of PTCD or ERCP for MOJ. The search period was from the establishment of the databases to July 2023. After quality assessment and data extraction from the included studies, Meta-analysis was performed using RevMan5.3 software.ResultsA total of 21 RCTs involving 1,693 patients were included. Meta-analysis revealed that there was no significant difference in the surgical success rate between the two groups for patients with low biliary obstruction (P=0.81). For patients with high biliary obstruction, the surgical success rate of the PTCD group was higher than that of the ERCP group (P 0.05).ConclusionBoth PTCD and ERCP can efficiently alleviate biliary obstruction and enhance liver function. ERCP is effective in treating low biliary obstruction, while PTCD is more advantageous in treating high biliary obstruction.</p
Asymmetric Hydrogenation of α‑Substituted Acrylic Acids Catalyzed by a Ruthenocenyl Phosphino-oxazoline–Ruthenium Complex
Asymmetric hydrogenation of various
α-substituted acrylic
acids was carried out using RuPHOX–Ru as a chiral catalyst
under 5 bar H<sub>2</sub>, affording the corresponding chiral α-substituted
propanic acids in up to 99% yield and 99.9% ee. The reaction could
be performed on a gram-scale with a relatively low catalyst loading
(up to 5000 S/C), and the resulting product (97%, 99.3% ee) can be
used as a key intermediate to construct bioactive chiral molecules.
The asymmetric protocol was successfully applied to an asymmetric
synthesis of dihydroartemisinic acid, a key intermediate required
for the industrial synthesis of the antimalarial drug artemisinin