N-heterocyclic carbene catalyzed [2 + 3] annulation reaction for the synthesis of trifluoroethyl 3,2'-spirooxindole γ-lactam.

Asymmetric catalytic processes promoted by N-heterocyclic carbenes (NHCs) hold great potential for the sustainable preparation of chiral molecules. However, catalyzing the reactions by manipulating the reactive intermediates is challenging. We report herein that the known NHC-catalyzed [3 + 2] annulation reaction between ketimine and enal can also be turned into a [2 + 3] annulation reaction for the highly enantioselective direct synthesis of trifluoroethyl 3,2'-spirooxindole γ-lactams (4) through timely catalysis of the intermediates. DFT calculations revealed that this transformation included the key step of the nucleophilic attack of the Breslow intermediate M2 derived from NHC and enal (2) to the unattacked ketimine (1). Our study demonstrates that it is possible to tune the desired selectivities through the dynamic catalysts of the reactive intermediates.

Molecular mechanisms that regulate the heat stress response in sea urchins (Strongylocentrotus intermedius) by comparative heat tolerance performance and whole-transcriptome RNA sequencing.

In the context of climate change and extreme high temperature, the commercially important sea urchin Strongylocentrotus intermedius suffers high mortality during summer in Northern China. How sea urchins respond to high temperatures is of great concern to academia and industry. How to understand the heat tolerance of sea urchin from the whole transcriptome level. In this study, the heat-resistant S. intermedius bred by our team and its control group were used as the research objects, then we applied whole-transcriptome RNA sequencing to detect differentially expressed mRNAs, microRNAs, long noncoding RNAs that respond to heat stress in the heat-resistant and control S. intermedius. A competitive endogenous RNA (ceRNA) regulatory network was constructed with predicted pairs of differentially expressed mRNAs and noncoding RNAs and revealed the molecular regulatory mechanisms in S. intermedius responding to heat stress. A functional analysis suggested that the ceRNAs were involved in basal metabolism, calcium ion transport, endoplasmic reticulum stress, and apoptosis. This is the whole-transcriptomic analysis of S. intermedius under heat stress to propose ceRNA networks that will provide a basis for studying the potential functions of long noncoding RNAs and miRNAs in the heat stress response in S. intermedius and provide a theoretical basis for the study of the molecular mechanism of sea urchins in response to environmental changes.

Differences in body wall metabolites of Apostichopus japonicus of different ages in liquid chromatography-tandem mass spectrometry.

Apostichopus japonicus is a marine invertebrate with high economic value. Analysis of the effects of age on the structure of this species is important for understanding the status of the population and conservation. In this study, metabolite analysis of the body walls of A. japonicus of three different ages (1, 2, and 3 years) was performed using LC-MS/MS. Metabolite analysis was performed for the KEGG metabolic pathway. The partial least squares-discriminant analysis is clearly distinguished metabolites in the three groups of A. japonicus. A total of 59, 222, and 179 different metabolites were detected in the age 3 vs age 2, age 3 vs age 1, and age 2 vs age 1 controls, respectively (P < 0.05). These metabolic differences involved several metabolic pathways, including phenylalanine metabolism, taurine and hypotaurine metabolism, sulfur metabolism et al. Thiamin, riboflavin, lipoic acid, acetyl l-carnitine levels increase with age, trans-10-heptadecenoic acid, stearic acid, pentadecanoic acid, dibutyl sebacate, and 8,15-diHETE levels decrease with age, which these metabolites can be used as potential markers to determine the age of A. japonicus. Our results provide the foundation for determining the age of A. japonicus and are important for the conservation of germplasm resources of A. japonicus.

A close look into the biological and synthetic aspects of fused pyrazole derivatives.

The fusion of pyrazole scaffold with other skeletons creates a class of attractive molecules, demonstrating significant biological and chemical potentiality in the development of medicinal chemistry. Over the past few decades, numerous biologically active molecules featuring fused pyrazole moieties have been excavated and synthesized, some of which represented by sildenafil have been marketed as drugs, and the biological importance together with chemical synthesis strategies of fused pyrazole compounds, including structural modification based on lead compounds, have been steadily progressing. In this review, we focused our attention on the biological importance of fused pyrazoles and highlighted recent progress in the synthesis of this framework over the past 10 years. What' s more, the limitations, challenges, and future prospects were proposed, wishing to provide references for the development of pyrazole fused frameworks in the field of medicinal chemistry. Contents.

Construction of multi-substituted pyrazoles via potassium carbonate-mediated [3 + 2] cycloaddition of in situ generated nitrile imines with cinnamic aldehydes.

A highly efficient potassium carbonate-mediated [3 + 2] cycloaddition reaction of hydrazonoyl chlorides with cinnamic aldehydes to furnish multi-substituted pyrazoles under nontoxic and mild conditions has been developed. A plausible stepwise cycloaddition reaction mechanism is proposed. This protocol featured broad substrate coverage, good functional group tolerance, wide scalability, and operational simplicity, as well as conveniently constructed pyrazole scaffolds.

Graphene quantum dots/L-cysteine coreactant electrochemiluminescence system and its application in sensing lead(II) ions.

A new coreactant electrochemiluminescence (ECL) system including single-layer graphene quantum dots (GQDs) and L-cysteine (L-Cys) was found to be able to produce strong cathodic ECL signal. The ECL signal of GQD/L-Cys coreactant system was revealed to be mainly dependent on some key factors, including the oxidation of L-Cys, the presence of dissolved oxygen and the reduction of GQDs. Then, a possible ECL mechanism was proposed for the coreactant ECL system. Furthermore, the ECL signal of the GQD/L-Cys system was observed to be quenched by lead(II) ions (Pb(2+)). After optimization of some important experimental conditions, including concentrations of GQDs and L-Cys, potential scan rate, response time, and pH value, an ECL sensor was developed for the detection of Pb(2+). The new methodology can offer a rapid, reliable, and selective detection of Pb(2+) with a detection limit of 70 nM and a dynamic range from 100 nM to 10 µM.