The Future of (Radio)-Labeled Compounds in Research and Development within the Life Science Industry

Selective H/D Exchange in E-H (E = Si, Ge, Sn) Bonds Catalyzed by 1,2,3-Triazolylidene-Stabilized Nickel Nanoparticles

Nickel nanoparticles (Ni·MIC) stabilized with mesoionic 1,2,3-triazolylidene (MIC) ligands were prepared via decomposition of the [Ni(COD)2] (COD = 1,5-cyclooctadiene) complex with H2 (3 bar) in the presence of 0.2 or 0.5 equiv of ligand. The obtained monodisperse and small-sized (3.2-3.8 nm) nanoparticles were characterized by high-resolution transmission electron microscopy (TEM, HRTEM) and inductively coupled plasma (ICP) analysis. Further analysis of the nickel nanoparticles by X-ray photoelectron spectroscopy (XPS) demonstrated the coordination of the MIC ligands to the metal surface. Finally, the Ni·MIC nanoparticles were applied in the isotopic H/D exchange in hydrides of group 14 elements (Si, Ge, Sn) using D2 gas under relatively mild conditions (1.0-1.8 mol % Ni, 1 bar D2, 55 °C). High and chemoselective deuterium incorporation at the E-H (E = Si, Ge, Sn) bond in these derivatives was observed.

Multiple Deuterium Atom Transfer Perdeuteration of Unactivated Alkenes under Base-Assisted Cobalt/Photoredox Dual Catalysis

A radical approach for hydrogenative perdeuteration of unactivated alkenes under cobalt/photoredox dual catalysis is described. The addition of a suitable base plays a key role in controlling two competing pathways by switching the catalytic performance of cobalt/photoredox catalysis. Base-assisted cobalt/photoredox dual catalysis promoted a hydrogen isotope exchange reaction of alkenes to afford deuterated alkenes via multiple repeating deuterium atom transfer/hydrogen atom abstraction processes, while consecutive reductive deuteration of alkenes proceeded in the absence of a base to afford polydeuterated alkanes. One-pot hydrogenative perdeuteration and perdeutero-arylation were also developed, providing access to various polydeuterated aliphatic compounds.

Nitrile-tolerant Iridium-catalysed Hydrogen Isotope Exchange

Isotopically labelled molecules are vital tools within drug discovery and are used extensively to assess a given candidate's absorption, distribution, metabolism, excretion, and toxicity (ADMET) profile. Related to this, transition metal-catalyzed hydrogen isotope exchange (HIE) has become a prominent technique for the rapid and selective late-stage installation of a deuterium or tritium label. Despite having a generally wide applicability, the current state-of-the-art in this specific field is limited when particularly co-ordinating motifs are present within a given molecule to be labelled. For example, the exceptional binding strength and sterically unencumbered nature of the nitrile functionality leads to inhibition of catalyst turnover, and has hindered the development of efficient methods for the HIE of nitrile-containing molecules. Herein, in silico solvent binding energy parameter approaches have been disclosed which have facilitated the discovery of uniquely tolerant neutral iridium catalyst species that demonstrate a significantly lower binding strength with nitrile functionality. In turn, we describe the first effective nitrile-tolerant HIE methodology enabled via ortho-directed C(sp2)-H activation using air- and moisture-stable iridium pre-catalysts of the type Ir(COD)(NHC)Cl under an atmosphere of deuterium gas. This methodology proceeds under mild and practically accessible reaction conditions with a range of directing groups, including heterocycles, ketones, and amines, with this class of catalyst also shown to be applicable towards bioactive molecules, resulting in products with high levels of isotopic labelling.

Phytoremediation of trichloroethylene in the soil/groundwater environment: Progress, problems, and potential

Trichloroethylene (TCE) poses a significant environmental threat in groundwater and soil, necessitating effective remediation strategies. Phytoremediation offers a cost-effective and environmentally friendly approach to remediation. However, the mechanisms governing plant uptake, volatilisation, and degradation of TCE remain poorly understood. This review explores the mechanisms of TCE phytoremediation, metabolic pathways, and influencing factors, emphasizing future research directions to improve the understanding of TCE phytoremediation. The results showed that although the proportion of TCE phytovolatilisation is limited, it is important at sites chronically contaminated with TCE. The rhizosphere is a key microzone for pollutant redox reactions that significantly enhance its effectiveness when its characteristics are fully utilised and manipulated through reinforcement. Future research should focus on manipulating microbial communities through methods such as the application of endophytic bacteria and genetic modification. However, practical applications are in their infancy and further investigation is needed. Furthermore, many findings are based on non-uniform parameters or unstandardised methods, making them difficult to compare. Therefore, future studies should provide more standardised experimental parameters and employ accurate and standardised methods to develop suitable prediction models, enhancing data comparability and deepening our understanding of plant detoxification mechanisms.

Au(I)-Catalyzed Regioselective Hydrogen Isotope Labeling of Indoles

The gold(I)-catalyzed hydrogen isotope exchange reaction on indoles and related heterocycles is described under mild conditions and low catalyst loadings, using CD3OD and D2O as readily available deuterium sources. C3-unsubstituted indoles are labeled at the C3 position with exquisite regioselectivity, while C3-substituted indoles are labeled at the C2 position. The method is also applicable to the regioselective tritiation of indoles. Mechanistic studies revealed the involvement of aurated indoles as key intermediates.

The Development and Application of Tritium-Labeled Compounds in Biomedical Research

With low background radiation, tritiate compounds exclusively emit intense beta particles without structural changes. This makes them a useful tool in the drug discovery arsenal. Thanks to the recent rapid progress in tritium chemistry, the preparation and analysis of tritium-labeled compounds are now much easier, simpler, and cheaper. Pharmacokinetics, autoradiography, and protein binding studies have been much more efficient with the employment of tritium-labeled compounds. This review provides a comprehensive overview of tritium-labeled compounds regarding their properties, synthesis strategies, and applications.

Engineered Antibodies as Cancer Radiotheranostics

Radiotheranostics is a rapidly growing approach in personalized medicine, merging diagnostic imaging and targeted radiotherapy to allow for the precise detection and treatment of diseases, notably cancer. Radiolabeled antibodies have become indispensable tools in the field of cancer theranostics due to their high specificity and affinity for cancer-associated antigens, which allows for accurate targeting with minimal impact on surrounding healthy tissues, enhancing therapeutic efficacy while reducing side effects, immune-modulating ability, and versatility and flexibility in engineering and conjugation. However, there are inherent limitations in using antibodies as a platform for radiopharmaceuticals due to their natural activities within the immune system, large size preventing effective tumor penetration, and relatively long half-life with concerns for prolonged radioactivity exposure. Antibody engineering can solve these challenges while preserving the many advantages of the immunoglobulin framework. In this review, the goal is to give a general overview of antibody engineering and design for tumor radiotheranostics. Particularly, the four ways that antibody engineering is applied to enhance radioimmunoconjugates: pharmacokinetics optimization, site-specific bioconjugation, modulation of Fc interactions, and bispecific construct creation are discussed. The radionuclide choices for designed antibody radionuclide conjugates and conjugation techniques and future directions for antibody radionuclide conjugate innovation and advancement are also discussed.

Combining Umpolung and Carbon Isotope Exchange Strategies for Accessing Isotopically Labeled α-Keto Acids

The integration of umpolung and carbon isotope exchange for accessing isotopically labeled α-keto acids through photoredox catalysis is elucidated. This process involves the carbonyl umpolung of C(sp2)-α-keto acids to yield C(sp3)-α-thioketal acids, followed by the carbon isotope exchange of C(sp3)-α-thioketal acids, and ultimately, deprotection to generate carbon-labeled α-keto acids.

Enantioselective Carbon Isotope Exchange

The synthesis of isotopically labeled organic molecules is vital for drug and agrochemical discovery and development. Carbon isotope exchange is emerging as a leading method to generate carbon-labeled targets, which are sought over hydrogen-based labels due to their enhanced stability in biological systems. While many bioactive small molecules bear carbon-containing stereocenters, direct enantioselective carbon isotope exchange reactions have not been established. We describe the first example of an enantioselective carbon isotope exchange reaction, where (radio)labeled α-amino acids can be generated from their unlabeled precursors using a stoichiometric chiral aldehyde receptor with isotopically labeled CO2 followed by imine hydrolysis. Many proteinogenic and non-natural derivatives undergo enantioselective labeling, including the late-stage radiolabeling of complex drug targets.

A practical guide for the preparation of C1-labeled α-amino acids using aldehyde catalysis with isotopically labeled CO2

Isotopically carbon-labeled α-amino acids are valuable synthetic targets that are increasingly needed in pharmacology and medical imaging. Existing preparations rely on early stage introduction of the isotopic label, which leads to prohibitive synthetic costs and time-intensive preparations. Here we describe a protocol for the preparation of C1-labeled α-amino acids using simple aldehyde catalysts in conjunction with [*C]CO2 (* = 14, 13, 11). This late-stage labeling strategy is enabled by the one-pot carboxylate exchange of unprotected α-amino acids with [*C]CO2. The protocol consists of three separate procedures, describing the syntheses of (±)-[1-13C]phenylalanine, (±)-[1-11C]phenylalanine and (±)-[1-14C]phenylalanine from unlabeled phenylalanine. Although the delivery of [*C]CO2 is operationally distinct for each experiment, each procedure relies on the same fundamental chemistry and can be executed by heating the reaction components at 50-90 °C under basic conditions in dimethylsulfoxide. Performed on scales of up to 0.5 mmol, this methodology is amenable to C1-labeling of many proteinogenic α-amino acids and nonnatural derivatives, which is a breakthrough from existing methods. The synthesis of (±)-[1-13C]phenylalanine requires ~2 d, with product typically obtained in a 60-80% isolated yield (n = 3, μ = 71, σ = 8.3) with an isotopic incorporation of 70-88% (n = 18, μ = 72, σ = 9.0). Starting from the preformed imino acid (~3 h preparation time), rapid synthesis of (±)-[1-11C]phenylalanine can be completed in ~1 h with an isolated radiochemical yield of 13%. Finally, (±)-[1-14C]phenylalanine can be accessed in ~2 d with a 51% isolated yield and 11% radiochemical yield.

Platform for Multiple Isotope Labeling via Carbon-Sulfur Bond Exchange

In this work, we explore a nickel-catalyzed reversible carbon-sulfur (C-S) bond activation strategy to achieve selective sulfur isotope exchange. Isotopes are at the foundation of applications in life science, such as nuclear imaging, and are essential tools for the determination of pharmacokinetic and dynamic profiles of new pharmaceuticals. However, the insertion of an isotope into an organic molecule remains challenging, and current technologies are element-specific. Despite the ubiquitous presence of sulfur in many biologically active molecules, sulfur isotope labeling is an underexplored field, and sulfur isotope exchange has been overlooked. This approach enables us to move beyond standardized element-specific procedures and was applied to multiple isotopes, including deuterium, carbon-13, sulfur-34, and radioactive carbon-14. These results provide a unique platform for multiple isotope labeling and are compatible with a wide range of substrates, including pharmaceuticals. In addition, this technology proved its potential as an isotopic encryption device for organic molecules.

Efficient palladium-catalyzed electrocarboxylation enables late-stage carbon isotope labelling

Carbon isotope labelling of bioactive molecules is essential for accessing the pharmacokinetic and pharmacodynamic properties of new drug entities. Aryl carboxylic acids represent an important class of structural motifs ubiquitous in pharmaceutically active molecules and are ideal targets for the installation of a radioactive tag employing isotopically labelled CO2. However, direct isotope incorporation via the reported catalytic reductive carboxylation (CRC) of aryl electrophiles relies on excess CO2, which is incompatible with carbon-14 isotope incorporation. Furthermore, the application of some CRC reactions for late-stage carboxylation is limited because of the low tolerance of molecular complexity by the catalysts. Herein, we report the development of a practical and affordable Pd-catalysed electrocarboxylation setup. This approach enables the use of near-stoichiometric 14CO2 generated from the primary carbon-14 source Ba14CO3, facilitating late-stage and single-step carbon-14 labelling of pharmaceuticals and representative precursors. The proposed isotope-labelling protocol holds significant promise for immediate impact on drug development programmes.