LongLarf

Abstract

This manuscript presents a regioselective chlorination of arenes, yielding almost exclusively the monochlorinated product. It tolerates free hydroxy groups, 1°, 2° and 3° amines, and carboxylic acids, among other polar and nonpolar functional groups, as well as mono- and polysubstituted aromatic rings. Additionally, the utilization of chlorosulfonium salts as the chlorinating agent is demonstrated. The method emerges as an alternative to other processes where organic byproducts must be separated from the reaction mixture. In addition, the main byproducts are gaseous materials such as CO and CO₂. This publication introduces the application of sulfoxides, oxalyl chloride, and aqueous hydrogen peroxide as the chlorination mixture.

Nature Chemical Biology, Published online: 20 November 2023; doi:10.1038/s41589-023-01484-2

Oxygen sensitivity hampers applications of metal-dependent CO2 reductases. Here, Oliveira et al. describe how an allosteric disulfide bond controls the activity of a CO2 reductase, preventing its physiological reduction during transient O2 exposure and allowing aerobic handling of the enzyme.

The asymmetric α-alkylation of acyclic carbonyls with hydrocarbons is of substantial interest and challenge. Herein, we achieved the enantioselective oxidative cross-coupling of 2-acylimidazoles with up to 99 % ee in moderate to good yields, thus providing an elegant access to optically active carbonyl compounds. Density functional theory calculations suggest a radical-radical cross-coupling pathway.

Abstract

The direct α-alkylation of acyclic carbonyls with nonactivated hydrocarbons through C(sp³)−H functionalization is both extremely promising and notably challenging, especially when attempting to achieve enantioselectivity using iron-based catalysts. We have identified a robust chiral iron complex for the oxidative cross-coupling of 2-acylimidazoles with benzylic and allylic hydrocarbons, as well as nonactivated alkanes. The readily available and tunable N,N′-dioxide catalysts of iron in connection with oxidants exhibit precise asymmetric induction (up to 99 % ee) with good compatibility in moderate to good yields (up to 88 % yield). This protocol provides an elegant and straightforward access to optically active acyclic carbonyl derivatives starting from simple alkanes without prefunctionalization. Density functional theory (DFT) calculations and control experiments were made to gain insight into the nature of C−C bond formation and the origin of enantioselectivity. We propose a radical-radical cross-coupling process enabled by the immediate interconversion between chiral ferric species and ferrous species.

Cobalt-catalyzed asymmetric hydrogenation of unsaturated substrates is summarized in this review article from the perspective of substrate specificity and mechanistic insight.

Abstract

Asymmetric hydrogenation finds widespread application in academia and industry. And indeed, a number of processes have been implemented for the production of pharma and agro intermediates as well as flavors & fragrances. Although these processes are all based on the use of late transition metals as catalysts, there is an increasing interest in the use of base metal catalysis in view of their lower cost and the expected different substrate scope. Catalysts based on cobalt have already shown their potential in enantioselective hydrogenation chemistry. This review outlines the impressive progress made in recent years on cobalt-catalyzed asymmetric hydrogenation of different unsaturated substrates. We also illustrate the ligand dependent substrate specificity as well as the mechanistic variability in detail. This may well guide further catalyst development in this research area.

We report a vitamin B₁₂-photocatalyzed strategy for the cyclopropanation of electron-deficient alkenes using dichloromethane (CH₂Cl₂) as the methylene source. The reaction has excellent functional group tolerance, is highly chemoselective, and the scope can be extended to other 1,1-dichloroalkanes for the preparation of D₂-cyclopropyl and methyl-substituted cyclopropyl adducts, all of which are important isosteres in medical chemistry.

Abstract

The cyclopropyl group is of great importance in medicinal chemistry, as it can be leveraged to influence a range of pharmaceutical properties in drug molecules. This report describes a Vitamin B₁₂-photocatalyzed approach for the cyclopropanation of electron-deficient alkenes using dichloromethane (CH₂Cl₂) as the methylene source. The reaction proceeds in good to excellent yields under mild conditions, has excellent functional group compatibility, and is highly chemoselective. The scope could also be extended to the preparation of D₂-cyclopropyl and methyl-substituted cyclopropyl adducts starting from CD₂Cl₂ and 1,1-dichloroethane, respectively.

Science, Volume 382, Issue 6673, Page 951-957, November 2023.

Science, Volume 382, Issue 6673, November 2023.

This review focuses on PEGylation, N-terminal acetylation, glycosylation, and some other modifications of peptide/proteins. Characteristics of structures for modifying groups and improvement of the peptide/proteins’ properties including their biodistribution, pharmacokinetics, enzymatic digestion, and toxicity were discussed. Some typical examples relating to regulating biological activities or critical physiological processes were illustrated for different peptide/proteins’ modifications.

Abstract

Covalent attachment of biologically active peptides/proteins with functional moieties is an effective strategy to control their biodistribution, pharmacokinetics, enzymatic digestion, and toxicity. This review focuses on the characteristics of different modification strategies and their effects on the biological activity of peptides/proteins and illustrates their relevant applications and potential.

Publication date: 14 March 2024

Source: Chem, Volume 10, Issue 3

Author(s): Zhenquan Sun, Han Liu, Xuechen Li

The first regioselective selenocarbonylation of alkenes is reported. This general protocol provides a variety of branched and linear selenoesters with wide functional group compatibility and tunable regioselectivity.

Abstract

An unprecedented regiodivergent palladium-catalyzed carbonylation of aromatic alkenes has been developed. Utilizing commercially available Pd(CH₃CN)₂Cl₂ in the presence of 1,1′-ferrocenediyl-bis(tert-butyl(pyridin-2-yl)phosphine) ligand L8 diverse selenoesters are obtained in a straightforward manner. Key to success for the control of the regioselectivity of the carbonylation step is the concentration of the acidic co-catalyst. This general protocol features wide functional group compatibility and good regioselectivity. Mechanistic studies suggest that the presence of stoichiometric amounts of acid changes the properties and coordination mode of the ligand leading to reversed regioselectivity.

Nature Chemical Biology, Published online: 20 November 2023; doi:10.1038/s41589-023-01484-2

Oxygen sensitivity hampers applications of metal-dependent CO2 reductases. Here, Oliveira et al. describe how an allosteric disulfide bond controls the activity of a CO2 reductase, preventing its physiological reduction during transient O2 exposure and allowing aerobic handling of the enzyme.

Nature Chemistry, Published online: 16 November 2023; doi:10.1038/s41557-023-01368-x

The inherent rigidity of the azaarene ring structure has made it challenging to achieve remote stereocontrol through asymmetric catalysis on these substrates. Now, through a photoenzymatic process, an ene-reductase system facilitates the production of diverse azaarenes with distant γ-stereocentres, highlighting the potential of biocatalysts for stereoselectivity at remote sites.

In this review, we highlight the utility of o-boronic acid imines, hydrazones, oximes, and diazaborines in chemical biology applications, including bioconjugation, drug delivery systems, stimuli-responsive polymers, and as chemical probes.

Abstract

Iminoboronates and diazaborines are related classes of compounds that feature an imine ortho to an arylboronic acid (iminoboronate) or a hydrazone that cyclizes with an ortho arylboronic acid (diazaborine). Rather than acting as independent chemical motifs, the arylboronic acid impacts the rate of imine/hydrazone formation, hydrolysis, and exchange with competing nucleophiles. Increasing evidence has shown that the imine/hydrazone functionality also impacts arylboronic acid reactivity toward diols and reactive oxygen and nitrogen species (ROS/RNS). Untangling the communication between C=N linked functionalities and arylboronic acids has revealed a powerful and tunable motif for bioconjugation chemistries and other applications in chemical biology. Here, we survey the applications of iminoboronates and diazaborines in these fields with an eye toward understanding their utility as a function of neighboring group effects.

Protein engineering technologies enabled enzymatic depolymerization to be part of the circular polymer economy. This concept provides an up-to-date summary of protein engineering of PET hydrolytic enzymes for improving catalytic activity and thermostability, and discusses extrinsic factors influencing enzymatic depolymerization efficiency as well as closed-loop bio-recycling and bio-upcycling solutions for PET wastes.

Abstract

Poly (ethylene terephthalate) (PET) is one of the most commonly used plastics in daily life and various industries. Enzymatic depolymerization and recycling of post-consumer PET (pc-PET) provides a promising strategy for the sustainable circular economy of polymers. Great protein engineering efforts have been devoted to improving the depolymerization performance of PET hydrolytic enzymes (PHEs). In this review, we first discuss the mechanisms and challenges of enzymatic PET depolymerization. Subsequently, we summarize the state-of-the-art engineering of PHEs including rational design, machine learning, and directed evolution for improved depolymerization performance, and highlight the advances in screening methods of PHEs. We further discuss several factors that affect the enzymatic depolymerization efficiency. We conclude with our perspective on the opportunities and challenges in bio-recycling and bio-upcycling of PET wastes.

Publication date: 14 December 2023

Source: Chem, Volume 9, Issue 12

Author(s): Raquel Sánchez-Bento, Baptiste Roure, Josep Llaveria, Alessandro Ruffoni, Daniele Leonori

Publication date: 14 December 2023

Source: Chem, Volume 9, Issue 12

Author(s): Petros L. Gkizis, Ierasia Triandafillidi, Christoforos G. Kokotos

Science, Volume 382, Issue 6672, Page 815-820, November 2023.