Transition-metal-catalyzed radical relay coupling reactions have recently emerged as one of the most powerful methods to achieve difunctionalization of olefins. However, there has been limited ...success in applying this method to asymmetric catalysis using an effective chiral ligand. Herein we report the Cu-catalyzed enantioselective alkylarylation of vinylarenes using alkylsilyl peroxides as alkyl radical sources. This reaction proceeds under practical reaction conditions and affords chiral 1,1-diarylalkane structures that are found in a variety of bioactive molecules. Notably, a highly enantioselective reaction was accomplished by combining chiral bis(oxazoline) ligands with chiral binaphthyl scaffolds.
A series of hydrogen-atom transfer (HAT) catalysts based on the readily available and tunable 1,4-diazabicyclo2.2.2octane (DABCO) structure was designed, and their photoinduced HAT catalysis ability ...was demonstrated. The combination of our HAT catalyst with an acridinium-based organophotoredox catalyst enables efficient and site-selective C–H alkylation of substrates ranging from unactivated hydrocarbons to complex molecules. Notably, a HAT catalyst with additional substituents adjacent to a nitrogen atom further improved the site selectivity. Mechanistic studies suggested that the N-substituent of the catalyst plays a crucial role, assisting in the generation of a dicationic aminium radical as an active species for the HAT process.
Protein‐free: A hydrogel containing phenylboronate was optimized so as to undergo rapid glucose‐dependent changes in the state of hydration under physiological aqueous conditions. A localized ...dehydration of the gel surface to form a “skin layer” enabled control of the release of insulin from the gel. This dehydration is induced by fluctuations in the glucose concentration in the range between normo‐ and hyperglycemia.
A
bstract
We consider three distinct methods to compute the mass spectrum of gauge theories in the Hamiltonian formalism: (1) correlation-function scheme, (2) one-point-function scheme, and (3) ...dispersion-relation scheme. The first one examines spatial correlation functions as we do in the conventional Euclidean Monte Carlo simulations. The second one uses the boundary effect to efficiently compute the mass spectrum. The third one constructs the excited states and fits their energy using the dispersion relation with selecting quantum numbers. Each method has its pros and cons, and we clarify such properties in their applications to the mass spectrum for the 2-flavor massive Schwinger model at
m
/
g
= 0
.
1 and
θ
= 0 using the density-matrix renormalization group (DMRG). We note that the multi-flavor Schwinger model at small mass
m
is a strongly coupled field theory even after the bosonizations, and thus it deserves to perform the first-principles numerical calculations. All these methods mostly agree and identify the stable particles, pions
π
a
(
J
PG
= 1
−
+
), sigma meson
σ
(
J
PG
= 0
++
), and eta meson
η
(
J
PG
= 0
−−
). In particular, we find that the mass of
σ
meson is lighter than twice the pion mass, and thus
σ
is stable against the decay process,
σ
→
ππ
. This is consistent with the analytic prediction using the WKB approximation, and, remarkably, our numerical results are so close to the WKB-based formula between the pion and sigma-meson masses,
M
σ
/
M
π
=
3
.
A
bstract
The tensor renormalization group method is a promising approach to lattice field theories, which is free from the sign problem unlike standard Monte Carlo methods. One of the remaining ...issues is the application to gauge theories, which is so far limited to U(1) and SU(2) gauge groups. In the case of higher rank, it becomes highly nontrivial to restrict the number of representations in the character expansion to be used in constructing the fundamental tensor. We propose a practical strategy to accomplish this and demonstrate it in 2D U(
N
) and SU(
N
) gauge theories, which are exactly solvable. Using this strategy, we obtain the singular-value spectrum of the fundamental tensor, which turns out to have a definite profile in the large-
N
limit. For the U(
N
) case, in particular, we show that the large-
N
behavior of the singular-value spectrum changes qualitatively at the critical coupling of the Gross-Witten-Wadia phase transition. As an interesting consequence, we find a new type of volume independence in the large-
N
limit of the 2D U(
N
) gauge theory with the
θ
term in the strong coupling phase, which goes beyond the Eguchi-Kawai reduction.
A novel approach for the efficient cleavage of the amide bonds in tertiary amides is reported. Based on the selective radical abstraction of a benzylic hydrogen atom by a CuBr
/Selectfluor hybrid ...system followed by a selective cleavage of an N-C bond, an acyl fluoride intermediate is formed. This intermediate may then be derivatized in a one-pot fashion. The reaction proceeds under mild conditions and exhibits a broad substrate scope with respect to the tertiary amide moiety as well as to nitrogen, oxygen, and carbon nucleophiles for the subsequent derivatization. Mechanistic studies suggest that the present reaction proceeds
a radical-polar crossover process that involves benzylic carbon radicals generated by the selective radical abstraction of a benzylic hydrogen atom by the CuBr
/Selectfluor hybrid system. Furthermore, a synthetic application of this method for the selective cleavage of peptides is described.
A
bstract
Monte Carlo simulation of gauge theories with a
θ
term is known to be extremely difficult due to the sign problem. Recently there has been major progress in solving this problem based on ...the idea of complexifying dynamical variables. Here we consider the complex Langevin method (CLM), which is a promising approach for its low computational cost. The drawback of this method, however, is the existence of a condition that has to be met in order for the results to be correct. As a first step, we apply the method to 2D U(1) gauge theory on a torus with a
θ
term, which can be solved analytically. We find that a naive implementation of the method fails because of the topological nature of the
θ
term. In order to circumvent this problem, we simulate the same theory on a punctured torus, which is equivalent to the original model in the infinite volume limit for
|θ| < π
. Rather surprisingly, we find that the CLM works and reproduces the exact results for a punctured torus even at large
θ
, where the link variables near the puncture become very far from being unitary.
Display omitted
•An organic electrochemical transistor with trisaccharide-functionalized PEDOT:PSS was developed for human influenza virus sensing.•The interaction of sialyllactose with hemagglutinin ...on the viral surface mimicked the host infection mechanism.•Influenza virus recognition was continuously monitored by drain current changes at no gate bias.•The limit of detection for human influenza A virus was 0.025 HAU.
An organic electrochemical transistor (OECT) with a trisaccharide-grafted conductive polymer channel was developed for human influenza A virus detection under aqueous conditions. A target recognition element was introduced into the electrochemical amplifier of the OECT for highly sensitive, selective, and label-free virus sensing. 3,4-Ethylenedioxythiophene (EDOT) and its derivative bearing an oxylamine moiety (EDOTOA) were electrochemically copolymerized on the channel region composed of a PEDOT:PSS thin film. The trisaccharides composed of Sia-α2,6′-Gal-Glu (2,6-sialyllactose), a specific receptor for the hemagglutinin used as a spike protein on the surface of human influenza A virus, were covalently introduced into the EDOTOA unit. Changes in the drain current of the OECT were observed following virus adsorption onto the 2,6-sialyllactose-functionalized channel. A signal transduction mechanism involving a doping effect due to the adsorption of negatively-charged virus nanoparticles is proposed. The limit of detection was more than two orders of magnitude lower than commercial immunochromatographic influenza virus assays over the same detection time. Because of its processability with printing technologies and low power consumption, the OECT device developed here may be suitable for the wearable monitoring of influenza virus infection.
PIC‐ing a winner: siRNA encapsulated by a phenylboronate‐functionalized polyion complex (PIC) micelle shows binding between the phenylboronate and the 3′ ribose of the siRNA (see scheme), stabilizing ...the complex under conditions equivalent to the extracellular environment. This complex is disrupted in response to addition of ATP, at a concentration comparable to that inside cells.
PDF
