Bulletin of the Korean Chemical Society最新文献

The theoretical study on the fixation and release of nitric oxide (NO) by N-heterocyclic carbenes (NHCs) is explored by utilizing a multivariate linear regression approach. We utilized data-driven tools to establish correlations between molecular descriptors of NHC and reaction outputs of the formation and NO release of NHC nitric oxide radicals (NHCNOs). A key electronic parameter, the singlet-triplet energy gap (ΔE_ST), plays a pivotal role in the thermodynamics of NHCNO formation (ΔG_f) and NO release (ΔG_r). The activation energy models highlight HOMO energy level (E_HOMO), C–N bond length (d_C–N), and NBO charge on N atom (q^NBO_N) as crucial factors for the formation of NHCNO (ΔG^‡_f), while the activation energy for the NO release (ΔG^‡_r) significantly correlates with free energy difference (ΔG_r), resulting a strong ΔE_ST dependency. This study provides valuable insights into the thermodynamics and kinetics of NHCNO processes, offering predictive capabilities to design NHCs tailored for NO release.

Oxazolo[5,4-d]pyrimidine derivatives have been reported to exhibit interesting biological activities. Herein, we described a solid-phase synthetic method to produce N-alkyl-7-alkylamino-2-aryloxazolo[5,4-d]pyrimidine-5-carboxamide derivatives. The strategy consists of loading the template compounds (i.e., 2-aryl-6,7-dihydrooxazolo[5,4-d]pyrimidin-7-one-5-carboxylic acids) onto aminated acid-sensitive methoxybenzaldehyde (AMEBA) resins, the subsequent benzotriazol-1-yloxytris(dimethylamino)phosphonium hexafluorophosphate (BOP)-mediated direct amination with primary/secondary amines, and the final cleavage from the solid support to afford the target compounds. The template 2-aryl-6,7-dihydrooxazolo[5,4-d]pyrimidin-7-one-5-carboxylic acids were prepared using a five-step solution-phase synthetic route from ethyl 2-cyano-2-(hydroxyimino)acetate. BOP-mediated direct amination conditions were optimized by a solution-phase model study. The solid-phase synthetic method provided the 17 target compounds in 16%–92% five-step overall isolated yields from the Merrified resin for selected template compounds and primary/secondary amines.

Amino-single benzene-based fluorophores (SBBFs) are representative small-size fluorescent dyes that have an electron push-pull structure within the benzene core. In this work, a new library of amino-SBBFs, which have trifluoroacetyl moiety at the electron-pushing amine group (named SBBF-TFA), featuring a variety of methylamines, dimethylamines, as well as acetyl. To explore the SBBF-TFA library, we conducted (i) library synthesis, (ii) assessment of various photophysical properties in nine different types of organic/aqueous solvents, and (iii) evaluation of cytotoxicity in the HeLa cell line. We believe that our findings provide valuable insights for advancing novel small-molecule fluorescent probes and materials with diverse applications across pharmacochemical fields.

Lithium–sulfur batteries (LSBs) have attracted attention as promising next-generation batteries due to their remarkably high capacity compared to lithium-ion batteries and the low cost of sulfur. However, one of the inherent problems of LSBs is the “shuttle effect,” which causes lithium metal anode instability and capacity fading. This is still a major barrier that must be overcome before it is used in the industry. Therefore, to commercialize LSBs, it is essential to suppress this shuttle effect. From this point of view, this review focuses on the categorization of the methods and materials for interlayer and separator modification, which is one of the effective ways to address the shuttle effect.

The escalating concern regarding microplastics (MPs) in the environment has recently accentuated the need for comprehensive analyses across various matrices. Fourier Transfrom Infrared (FT-IR) microscopy is widely used method for MP identification, but challenges arise due to the presence of secondary materials on real samples, causing inaccuracies in spectral matching. To tackle this issue, we propose a solution: a 1D-convolution neural network (1D-CNN) machine-learning model classifying FT-IR spectra into 16 polymer species. Using a dataset of 5413 spectra, with 80% (4330) for training and 20% (1083) for external testing, our method achieved 98.59% accuracy for cross-validation and 92.34% for external validation. This study underscores the efficacy of machine learning in discerning polymer types among MPs, even in real samples tainted by secondary materials. The implementation of our 1D-CNN model marks a significant leap in overcoming conventional method limitations, providing a robust tool for accurately unraveling MPs intricacies in environmental matrices.

Metal nanoparticle (NP)-catalyzed electron transfer (ET) from a reducing agent to a metal complex is useful for signal amplification in biosensors. For efficient ET, the metal complex must undergo rapid outer-sphere reactions, be highly water-soluble, and effectively penetrate bio/organic layers on metal NPs. Our study identifies Ru(NH₃)₆³⁺ as well-suited for this purpose. Among reducing agents, ammonia-borane (AB) enables rapid metal NP-catalyzed ET, with Au, Pt, and Pd NPs displaying similar catalytic activities. The pseudo second-order rate constant for 20-nm Au NP-catalyzed ET from AB to Ru(NH₃)₆³⁺ (1.4 × 10⁸ M⁻¹ s⁻¹) approaches the diffusion-controlled rate constant. Despite immunoglobulin G and bovine serum albumin passively adsorbed on Au NPs, catalytic activity remains largely unaffected. Applying Au NP-catalyzed ET to prostate-specific antigen detection in human serum achieves a low detection limit of 10 pg/mL. These findings highlight the potential of Ru(NH₃)₆³⁺ and AB in designing biosensors based on rapid catalytic reaction.

The first facile synthesis of cypripedin (1) was achieved using commercially available 2,3-dihydroxybenzaldehyde (2) and 5-bromovanillin (4) via a convergent strategy involving the Mizoroki–Heck reaction and photocyclization as key steps.

The cover picture illustrates the artificial intelligence model that predicts the performance of organic photovoltaics. This model predicts how organic photovoltaics will perform under 1 sun AM 1.5 G illumination by using only the molecular structure of the organic semiconductors within the bulk heterojunction photoactive layer. The organic semiconductors of the target organic photovoltaics comprise polymer donors and bay-position-linked diperylenediimide acceptors. More details are available in the article Gyu-Hee Kim, Keonho Yoon, Chihyung Lee, Minwoo Nam, Doo-Hyun Ko

Atomically dispersed metal catalysts or single-atom catalysts have made great strides during the past decade in the catalysis field. While an initial vision of atomically dispersed metal catalysts was to combine the advantages of homogeneous and heterogeneous catalysts, their unexpected potentials continue to be discovered. In this account, we introduce historical backgrounds underpinning the emergence of atomically dispersed metal catalysts. Next, we illustrate some recent examples demonstrating the unusual reactivities of atomically dispersed metal catalysts, which are hard to realize by homogeneous or heterogeneous catalysts. We conclude the account by suggesting the remaining challenges in this exciting field.

Stereoselective synthesis of the C₂₁-C₄₁ fragment 4 of the reported structure of Neaumycin B(1), a 28-membered macrolide compound with 19-chiral centers and 6,6-spiroketal structure, has been described. C₂₁-C₂₇ fragment 5 was synthesized from the commercially available (S)-Roche ester 7 using stereoselective allylation and Brown anti-crotylation as key steps. C₂₈-C₄₁ fragment 6 was constructed from chiral oxazolidinone auxiliary 13 using Evans syn-aldol reaction, diastereoselective epoxidation, and (S)-CBS reduction as key steps. Finally, boron-mediated acetate aldol reaction of 5 and 6 led to the synthesis of C₂₁-C₄₁ fragment 4 for the reported structure of Neaumycin B (1).