Deuterium- and Tritium-Labelled Compounds: Applications in the Life Sciences

Discovery of cmpd D6 (FH-001) as a efficiency enhancement and myelosuppression degradation small-molecule fms-like tyrosine kinase 3 inhibitor for the treatment of FLT3-ITD positive acute myeloid leukemia

AML is the most common and lethal type of leukemia. The mutant of FLT3 kinase is the most common mutation in AML. Based on the structure analysis and deuteration modification of the cmpd 18 (CHMFL-FLT3-122), a potent and orally available FLT3 Kinase inhibitor, cmpd D6 (FH-001) was found, which demonstrated a remarkable inhibitory effect on the proliferation of FLT3 - ITD positive AML cancer cell lines. Specifically, it effectively suppressed the growth of the MV4-11 cell line (IC50 = 42.8 nM versus 17.1 nM). Similarly, notable inhibitory activity was observed in the MOLM-13 (IC50 = 20.8 nM versus 53.9 nM). More importantly, the IC50 of cmpd D6 to inhibit FLT3 kinase was 338.689 nM and the IC50 to inhibit c-KIT kinase was 3006.042 nM, which were much lower than the IC50 of cmpd 18 to the two kinases, indicating that cmpd D6 may effectively avoid the synthetic lethal myelosuppression toxicity caused by FLT3/c-KIT double inhibition. Pharmacokinetic experiments showed that the deuterated cmpd D6 could prolong the half-life (T1/2 = 4.333 h versus 3.646 h) and improve bioavailability (F = 42.51 % versus 35.93 %). Pharmacodynamic experiments of the three models showed that cmpd D6 (12.5 mg/kg) could significantly inhibit tumor growth compared with cmpd 18, and had no obvious toxicity. Based on the above results, cmpd D6 is a potential candidate drug for the future treatment of FLT3-ITD positive AML.

Ru-based nanoparticle catalyzed direct H/D exchange of silanes

Deuterated silanes, among the most important reagents for introducing deuterium atoms, are widely utilized in organic synthesis. However, synthesizing versatile deuterated silanes under mild conditions remains a challenge. In this study, we report an effective method for H/D exchange of silanes using Ru-bpy@γ-Al2O3. Deuterium gas (D2), generated in situ from the electrolysis of D2O, served as the deuterium source. Various hydrosilanes and hydrosiloxanes undergo smooth H/D exchange under mild conditions. Furthermore, the products were applied for the derivatization of a wide range of compounds.

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.

Base Promoted Hydrogenation of N-Heteroarenes with Ammonia Borane and DMSO

Herein, we report a sodium tert-butoxide-promoted reduction of N-heteroarenes using ammonia borane and dimethyl sulfoxide (DMSO) under mild reaction conditions. This method demonstrates broad functional group compatibility across diverse N-heteroarene substrates. Notably, substituting DMSO with deuterated DMSO-d6 enables the synthesis of C3-deuterated 1,2,3,4-tetrahydroquinolines with remarkable positional selectivity. Mechanistic investigations indicate that the protons are derived from both ammonia borane and DMSO. This strategy establishes a novel and environmentally benign approach for the synthesis of (deuterated) N-heterocycles, offering practical advantages in terms of operational simplicity and sustainable reaction conditions.

Electrochemical debrominative hydrogenation/deuteration of 2-bromo-N-arylacetamides

Herein, we report a facile and efficient electro-reductive debrominative hydrogenation/deuteration of 2-bromo-N-aryl acetamides using H2O/D2O as an economical source of hydrogen/deuterium at room temperature. The reactions proceeded efficiently via C-Br bond activation, enabling facile synthesis of a range of N-substituted amides in moderate to high yields with broad functional group compatibility.

Photocatalytic and Chemoselective H/D Exchange at α-Thio C(sp3)-H Bonds

Deuterated compounds used in drug discovery and live-cell imaging have recently gained the attention of various scientific fields. Although hydrogen-deuterium (H/D) exchange reactions are straightforward deuteration methods, achieving perfect chemoselectivity is challenging. We report the highly chemoselective deuteration of α-thio C(sp3)-H bonds using a thioxanthone or anthraquinone organic photocatalyst bearing an aromatic ketone skeleton and D2O as an inexpensive deuterium source under 390 nm irradiation. Notably, incorporation of deuterium at the α-positions of the O/N atoms, benzylic positions, and aromatic rings was not observed. The present chemoselectivity was accomplished via a single electron transfer mechanism between the photocatalyst and S-containing substrates, as proven by laser-induced time-resolved transient absorption spectroscopic measurements. Furthermore, the proposed deuteration method could be applied to various S-containing substrates, including pharmaceuticals and biologically active compounds with high regioselectivities. The available deuterated compounds as novel deuterated alkylation reagents for future drug discovery and materials for Raman imaging were also demonstrated.

Nickel-Catalyzed Deuteration of Primary, Secondary, and Tertiary Silanes: Scope and Mechanistic Insights

Deuterated silanes are crucial reagents for deuteration, with a diverse range of applications in materials science, pharmaceuticals, and isotopic labeling. While most methods for synthesizing deuterated silanes rely on stoichiometric environmentally harmful processes or noble metal catalysts, research into more sustainable alternatives has received relatively less attention. In this study, we introduce a catalyst based on a nickel PBP-pincer system (PBP = bis(phosphino)boryl), which effectively facilitates catalytic hydrogen/deuterium exchange for primary, secondary, and tertiary silanes, as well as tertiary siloxanes and certain boranes, utilizing a catalyst loading of 2 mol % at 25 °C. DFT calculations identify two reaction pathways that require overcoming similar energy barriers for the H/D exchange step: silane activation assisted by the PBP ligand (ΔG⧧ = 24.1 kcal mol-1) and H/D exchange promoted by nucleophilic Ni-hydride (ΔG⧧ = 22.4 kcal mol-1). These results suggest that both pathways are feasible, with a slight energetic preference for the latter. We also present detailed mechanistic studies, including control experiments, an analysis of catalyst deactivation pathways, and kinetic studies that are in excellent agreement with the outcome of the theoretical calculations.

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.

Synthesis and characterization of 15N-labeled tetranuclear Ir complexes via Li2C15N2

The synthesis of 15N-labeled organometallic complexes is challenging due to limited suitable 15N-labeled precursors. Herein, we report the preparation of a 15N-labeled tetranuclear iridium complex, 15N-1, from Li2C15N2, with nitrogen atoms originally from 15N2 gas. Mono-methylation and single-electron oxidation of 15N-1 yield the corresponding ate complexes, 15N-2 and 15N-3. These complexes were characterized by 1H, 13C, and 15N NMR spectroscopy and X-ray diffraction.

Application of deuterium in research and development of drugs

Deuterium is gaining increased attention and utilization due to its unique physical and chemical properties. Deuteration has the unique benefit of positively impacting metabolic fate of pharmacologically active compounds without altering their chemical structures, physical properties, or biological activity and selectivity. In these favorable cases, deuterium substitution can in principle improve the pharmacokinetic properties and safety of therapeutic agents. The use of deuterium to create a new chemical entity not only starts with an existing drug, but can be achieved from iterative optimization in the de novo design of new compounds. Furthermore, deuterium has become a powerful tool in pharmaceutical analysis, including deuterium-labeled compounds as internal standards for extensive analysis, metabolomics, ADME, clinical pharmacology studies. This review highlights the application of deuterium in enhancing the pharmacological effects of active molecules during drug discovery and development. Additionally, deuterium-enabled pharmaceutical analysis is also covered. This review is aimed to provide references for the discovery of new deuterium-containing chemical entities with improved pharmacological properties and for the research of fate of drugs.

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.

Deuteriodifluoromethyl Sulfonium Ylides: Easily Accessible Reagents for Electrophilic Deuteriodifluoromethylation of O-Nucleophiles

A class of sulfonium ylide-based reagents for electrophilic deuteriodifluoromethylation is reported. Thus, a wide array of ubiquitous O-nucleophiles such as sulfonic acid, alcohol, carboxyl acid, and phosphoric acid are deuteriodifluoromethylated, providing a straightforward approach to access the OCF2D-functionalizazed scaffolds that are otherwise challenging to synthesize using conventional methods. This base-free protocol also displays broad functional group compatibility and is amenable to effective late-stage modification of bioactive molecules.

Photo-induced dehalogenative deuteration and elimination of alkyl halides enabled by phosphine-mediated halogen-atom transfer

Dehalogenative deuteration of organic halides is an efficient and straightforward method for incorporating deuterium atoms at specific locations within target molecules. However, utilizing organic halides in photoredox chemistry, particularly unactivated alkyl halides, presents challenges due to their low reduction potentials. In this work, we present a general and effective photoinduced dehalogenative deuteration method for a diverse array of alkyl halides, employing D2O as an economical source of deuterium. The use of Cy3P as a halogen-atom transfer reagent facilitates the dehalogenation of alkyl halides. This method demonstrates a broad scope, with over 70 examples, and shows excellent tolerance for various alkyl halides. The precise dehalogenation of complex alkyl halides highlights the potential of this protocol for late-stage dehalogenative deuteration of natural product derivatives and pharmaceutical compounds. Additionally, the dehalogenative elimination of unactivated alkyl halides can also be achieved by integrating photoredox and cobalt catalysis using the same halogen-atom transfer agents.

Atroposelective [4+1] annulation for the synthesis of isotopic isoindolinones bearing both central and axial chirality

Isotopically chiral molecules have drawn much attention due to their practical applications in drug discovery. However, existing studies in this area are mainly limited to centrally chiral molecules and H/D exchange. Herein, we report a chiral phosphoric acid-catalyzed atroposelective [4+1] annulation of ketoaldehydes and 1H-indol-1-amines. By means of this strategy, a series of D- and 18O-labeled atropisomers featuring both central and axial chiralities are synthesized with high enantioselectivities and diastereoselectivities and good to excellent isotopic incorporation. Experimental and density functional theory studies suggest that the reaction involves a sequential condensation, cyclization and isomerization cascade, in which the second step is the enantio-determining process.

Nanobiotechnology: traditional re-interpreting personalized medicine through targeted therapies and regenerative solutions

Nanobiotechnology is transforming personalized medicine by leveraging the unique properties of nanomaterials to address key challenges in targeted drug delivery, regenerative medicine, and diagnostics. The development of nanocarriers, such as liposomes, polymeric nanoparticles, dendrimers, and metallic nanoparticles, has enabled precise drug delivery with enhanced bioavailability and reduced systemic toxicity. Concurrently, nanostructured scaffolds have advanced regenerative medicine by supporting stem cell differentiation, modulating cellular microenvironments, and enhancing tissue repair. These nanoscale innovations have also led to highly sensitive biosensors and imaging agents, significantly improving early disease detection and biomarker monitoring. Despite these advancements, challenges persist, including nanoparticle-induced cytotoxicity, immunogenicity, scalability issues, and regulatory hurdles requiring extensive evaluation of long-term biocompatibility and pharmacokinetics. Addressing these limitations, recent breakthroughs in AI-assisted nanotechnology and CRISPR-Cas9-mediated gene editing are driving next-generation precision medicine, integrating nanoscale therapeutics with computational approaches to enhance efficacy. Future directions focus on nanorobotics, bioengineered nanovaccines, and theranostic platforms capable of simultaneous diagnosis and treatment, paving the way for real-time, patient-specific interventions. The successful translation of nanomedicine into clinical practice will require interdisciplinary collaboration across nanoscience, bioengineering, and translational medicine to refine nanoparticle functionalization, optimize safety profiles, and ensure equitable access to nanotherapeutics. This review provides a comprehensive overview of these advancements, challenges, and emerging opportunities in nanobiotechnology-driven precision medicine.

Pd-catalyzed deuteration of aryl halides with deuterium oxide

Late-stage deuteration of aryl halides with deuterium oxide is a highly desirable but challenging transformation, primarily due to the difficulty of activating inert carbon-halogen bonds and the umpolung of deuterium oxide in the presence of various functional groups. To achieve this transformation, efforts have been made to develop photo-chemical, electro-chemical, or mechano-chemical strategies. However, these approaches often require specialized setups or activated substrates. Despite the well-known functional group tolerance of palladium catalysis, which makes it valuable in late-stage functionalization, a palladium-catalyzed deuteration of aryl halides with deuterium oxide has remained elusive. Herein, a deuteration reaction of aryl bromides, chlorides, and triflates with deuterium oxide has been developed, through palladium catalysis. Chemical equivalent amount of D2O is required for inert substrates like aryl chlorides. The reaction features high functional group tolerance, making it suitable for late-stage deuteration.

Electrochemical cobalt-catalyzed semi-deuteration of alkynes to access deuterated Z-alkenes

Deuterium labeling has found extensive applications across various research fields, including organic synthesis, drug design, and molecular imaging. Electrocatalytic semi-hydrogenation of alkynes offers a viable route for the synthesis of Z-alkenes, yet it falls short in achieving the semi-deuteration of these compounds. In this study, we report an electrochemical cobalt-catalyzed transfer deuteration reaction that proficiently accomplishes the semi-deuteration of alkynes, yielding Z-configuration deuterated alkene products. This reaction utilizes cost-effective cobalt salts as catalysts and employs D2O and AcOD (acetic acid-d) as economical and efficient deuterium sources, underscoring its practicality and feasibility. The reaction demonstrates a broad alkyne substrate scope, high reaction efficiency, good functional group compatibility, excellent Z-selectivity, and a remarkable degree of deuteration rate.

Photocatalytic Multiple Deuteration of Polyethylene Glycol Derivatives Using Deuterium Oxide

Deuterated molecules are of growing interest because of the specific characteristics of deuterium, such as stronger C-D bonds being stronger than C-H bonds. Polyethylene glycols (PEGs) are widely utilized in scientific fields (e. g., drug discovery and material sciences) as linkers and for the improvement of various properties (solubility in water, stability, etc.) of mother compounds. Therefore, deuterated PEGs can be used as novel tools for drug discovery. Although the H/D exchange reaction (deuteration) is a powerful and straightforward method to produce deuterated compounds, the deuteration of PEGs bearing many unactivated C(sp3)-H bonds has not been developed. Herein, we report the photocatalytic deuteration of multiple sites of PEGs using tetra-n-butylammonium decatungstate (TBADT) and D2O as an inexpensive deuterium source. This deuteration can be adapted to PEG derivatives bearing various substituents ((hetero)aryl, benzoyl, alkyl, etc.). The deuteration efficiencies of the α-oxy C(sp3)-H bonds at the terminal positions of the PEGs were strongly influenced by the substituents. These reactivities were elucidated by density functional theory calculations of the reaction barriers towards the formation of radical intermediates, induced by the excited state of TBADT and the PEG substrate. In addition, the applicability of deuterated PEGs to internal standard experiments and Raman spectroscopy was demonstrated.

Catalytic H/D exchange of (hetero)arenes with early-late polyhydride heterobimetallic complexes: impact of transition metal pairs

Metal-catalyzed hydrogen isotope exchange (HIE) has become a valuable method for incorporating deuterium and tritium into organic molecules, with applications in a wide range of scientific fields. This study explores the role of transition metal cooperativity in enhancing catalytic hydrogen/deuterium (H/D) exchange using early-late heterobimetallic polyhydride (ELHB) complexes. A series of four ELHB complexes, of general formula [M(CH2tBu)3(H)xM'Cp*], combining early transition metals (M = Hf, Ta) with late metals (M' = Ir, Os), were synthesized and evaluated for their catalytic activity in HIE of (hetero)arenes. Hafnium-iridium and hafnium-osmium complexes showed a clear improvement in catalytic efficiency and reaction rate over monometallic analogues, suggestive of metal-metal synergy. Conversely, the tantalum-based heterobimetallic complexes showed lower catalytic performance, revealing that not all metal combinations are equally effective. These results underline the importance of careful metal selection to optimize transition metal cooperativity, and open up new possibilities for the design of more efficient H/D exchange catalysts.

Photoinduced Late-Stage Radical Decarboxylative and Deoxygenative Coupling of Complex Carboxylic Acids and Their Derivatives

The simple and efficient conversion of carboxylic acids into structurally diverse organic molecules is highly desirable in chemical synthesis. This review covers recent developments in photocatalytic methodology for late-stage transformations of complex carboxylic acids and their derivatives enabled by radical decarboxylation and deoxygenation, highlighting some representative and significant contributions in this field. These advancements are categorized based on the reactivity patterns exhibited by the carboxylic acids. Several activation modes to generate alkyl or aryl radical intermediates during decarboxylation of carboxylic acids are presented, namely, single-electron transfer (SET) oxidation, ligand-to-metal charge transfer (LMCT), SET reduction, and energy transfer (EnT) processes. On the other hand, direct activation of C-O bonds in carboxylic acids mediated by phosphoranyl radicals has been discussed and illustrates their potential synthetic application for the synthesis of complex aldehydes, ketones and amides.

Copper-catalyzed sulfonylation of alkenes with CH3SSO3Na

A successful methodology for the copper-catalyzed dehydrogenated methylsulfonylation of alkenes utilizing CH3SSO3Na in conjunction with hypervalent iodine reagents was successfully established. This method offers a practical avenue to obtain allyl methyl sulfones and alkenyl methyl sulfones by forming C-S bonds. Using the C-H bond oxidation sulfonylation strategy with alkenes and Bunte salts, we successfully synthesized a total of twenty two compounds, including four examples of deuterium-substituted molecules, and demonstrated one example of a scale-up reaction.

Fabrication of atomically dispersed barium hydride catalysts for the synthesis of deuterated alkylarenes

Marvelous natures of alkali and alkaline earth metal hydrides in catalyzing chemical transformations are being discovered. However, the synthesis of (sub)nanostructured metal hydrides, critically important to enhance their catalytic performances, is yet a very challenging task. Herein, we develop a highly reactive heterogeneous catalyst comprising atomically dispersed barium hydrides on MgO support with an ultrahigh barium loading of up to 20 wt% via a convenient preparation method involving liquid-ammonia impregnation followed by hydrogenation. The surface barium hydride species not only exhibits extraordinary reactivity toward H2 activation at room temperature, but also enables the highly efficient hydrogen isotope exchange (HIE) of both sp3 C-H and sp2 C-H bonds in nonactivated alkylarenes using D2 as the deuterium source under mild conditions. The deuteration rate at benzylic site is two orders of magnitude higher than that of bulk BaH2. This study offers an alternative synthetic route for the manufacture of deuterium-labeled compounds using a heterogenous transition metal-free hydride catalyst beyond the widely studied molecular metal complexe catalysts.

Access to N-α-deuterated amino acids and DNA conjugates via Ca(II)-HFIP-mediated reductive deutero-amination of α-oxo-carbonyl compounds

The development of practical and selective strategies for deuterium incorporation to construct deuterated molecules, particularly deuterium-labeled amino acids, has become as a growing focus of basic research, yet it remains a formidable challenge. Herein, we present a bioinspired calcium-HFIP-mediated site-selective reductive deutero-amination of α-oxo-carbonyl compounds with amines. Utilizing d2-Hantzsch ester as the deuterium source, this reaction attains remarkable deuteration efficiency (> 99% deuteration). It enables the synthesis of N-α-deuterated amino acid motifs with a wide range of functionality, as evidenced by over 130 examples. The method exhibits compatibility with diverse substrates, such as amino acids, peptides, drug molecules, and natural products bearing different substituents. Moreover, the application of this strategy in the synthesis of DNA-tagged N-α-deuterated amino acids/peptides has been demonstrated. This work offers an efficient and innovative solution for deuterated amino acid chemistry and holds substantial application potential in organic synthesis, medicinal chemistry, and chemical biology.

Thianthrenium-Enabled Chromium-Catalyzed Deuterated Alkyl Addition to Aldehydes via a Photoactive Electron Donor-Acceptor Complex

The Nozaki-Hiyama-Kishi reaction offers effective and reliable strategies for the preparation of alcohols via carbon-carbon bond formation. Typical methods usually require stoichiometric amounts of chromium salts, co-transition metals, and auxiliary reagents, which limits their practical application in industrial chemistry. To mitigate these limitations, substantial efforts have been made to develop chromium-catalytic approaches. However, an excess of metal reductants or expensive photocatalysts played essential roles during the catalytic cycles. Here, we present a photoactive electron donor-acceptor (EDA) complex-induced chromium-catalyzed route, accomplishing alkyl addition to aldehydes without the requirement of metal reductants or photocatalysts. Furthermore, on the basis of the pH-dependent site-selective hydrogen isotope exchange of alkyl thianthrenium salts, a range of β-deuterated secondary alcohols could be prepared with high efficiency and excellent deuterium incorporation. Mechanistic studies revealed that the photoinduced intramolecular single-electron transfer of the EDA complex happened to provide alkyl radicals that are captured by Cr(II) species to facilitate the subsequent carbon-carbon bond formation. Meanwhile, the excited Hantzsch ester could act as a terminal reductant for the turnover of the chromium catalyst.

Unlocking the potential of hydrogen deuterium exchange via an iterative continuous-flow deuteration process

Labelled compounds bearing hydrogen isotopes are keystones in diverse areas constituting a multi-billion dollar global market including drugs, diagnostics, biology, toxicology and smart materials. While hydrogen deuterium exchange (HDE) methods hold promise as relevant tools for the late-stage and one-step preparation of deuterium-labelled compounds, they often fall short in achieving sufficient isotopic purity combined either with a site-selectivity or with a full deuteration process, highlighting the need for further development and optimisation. This report pinpoints an approach to unlock the potential of HDE using the concept of iterative runs in continuous-flow technology (recirculation process). This closed-loop process grants access now to deuterated compounds with high isotopic purities, labelled at a precise site or perdeuterated on demand, in a fast, productive, and environmentally friendly way.

Hexafluorophosphate-Triggered Hydrogen Isotope Exchange (HIE) in Fluorinated Environments: A Platform for the Deuteration of Aromatic Compounds via Strong Bond Activation

There is a perpetual need for efficient and mild methods to integrate deuterium atoms into carbon frameworks through late-stage modifications. We have developed a simple and highly effective synthetic route for hydrogen isotope exchange (HIE) in aromatic compounds under ambient conditions. This method utilizes catalytic amounts of hexafluorophosphate (PF6 -) in deuterated 1,1,1,3,3,3-hexafluoroisopropanol (HFIP-d1) and D2O. Phenols, anilines, anisoles, and heterocyclic compounds were converted with high yields and excellent deuterium incorporations, which allows for the synthesis of a wide range of deuterated aromatic compounds. Spectroscopic and theoretical studies show that an interactive H-bonding network triggered by HFIP-d1 activates the typically inert P-F bond in PF6 - for D2O addition. The thus in situ formed DPO2F2 then triggers HIE, offering a new way to deuterated building blocks, drugs, and natural-product derivatives with high deuterium incorporation via the activation of strong bonds.

Facile and Regioselective Deuteration of C2-Alkylated Imidazolium Salts in the Presence of Cesium Carbonate

Thirteen imidazolium iodides bearing benzyl, mesityl, or 2,6-diisopropylphenyl substituents on their nitrogen atoms, and C1-C4 alkyl chains on their C2 carbon atom were readily deuterated with D2O as a cheap and non-toxic deuterium source in the presence of Cs2CO3, a weak, innocuous, inorganic base. The isotopic exchange proceeded quickly and efficiently under mild, aerobic conditions to afford a range of aNHC and NHO precursors regioselectively labeled on their C2α exocyclic position and/or C4=C5 heterocyclic backbone. A "carbene-free" mechanism was postulated, in which the carbonate anion acts as a catalyst to activate an exocyclic, acidic C-H bond and ease a deuterium transfer from D2O to the imidazolium salt in a concerted fashion.

Electron paramagnetic resonance spectroscopy: toward the path of dihydrogen isotopologue detection in porous materials

Electron paramagnetic resonance (EPR) spectroscopy is a powerful method to characterize the local framework structure of nanoporous materials during the dihydrogen isotopologue adsorption process. It also allows for exploring the adsorption sites of the dihydrogen isotopes and monitoring their desorption characteristics on the microscopic scale. The paramagnetic spin probes in the form of transition metal ions or organic radicals are required for EPR spectroscopy and are introduced either at the framework lattice position or in the pores of the metal-organic frameworks. This review highlights current advancements within the field of dihydrogen isotopologue detection as well as key findings related to the versatility of in situ continuous wave EPR and pulsed EPR experiments as toolkits for monitoring the adsorption-desorption process of dihydrogen isotopologues from the perspective of the framework as well as studying the host-guest interactions based on high-resolution advantages offered by using a pulsed EPR approach.

Selective Deuteration and Tritiation of Pharmaceutically Relevant Sulfoximines

Pharmaceutical-aligned research endeavors continue to diversify, including via the installation of new chemical functionality and non-classical bioisosteres within drug design. With this, an equally high demand emerges for the direct installation of isotopic substituents into these scaffolds within drug discovery programmes, as isotopologues are essential for the elucidation of the biological efficacy and metabolic fate of the active pharmaceutical ingredient (API). The sulfoximine functional group has recently become established as a high-value unit in this context; however, general and effective methods for the synthesis of deuterium (2H, D) and tritium (3H, T) labelled analogues have remained elusive. Herein, we disclose the design and development of the first iridium-catalyzed sulfoximine-directed hydrogen isotope exchange (HIE) systems that permit the site-selective integration of a distinguishing atomic label at aromatic C(sp2)-H and more challenging C(sp3)-H moieties. Moreover, we exemplify the broad applicability of these methods within a spectrum of molecular settings, as well as in the late-stage generation of isotopically-enriched complex bioactive architectures.

Specific Protein Quantification by Radioimmuno-Dot-Blot Assay for Complex Mixture Samples Utilizing Strep-Tag and Tritium-Labeled Strep-Tactin

Accurately quantifying specific proteins from complex mixtures like cell lysates, for example, during in vivo studies, is difficult, especially for aggregation-prone proteins. Herein, we describe the development of a specific protein quantification method that combines a solid-state dot blot approach with radiolabel detection via liquid scintillation counting. The specific detection with high sensitivity is achieved by using the Twin-Strep protein affinity tag and tritium-labeled 3HStrep-TactinXT probe. While the assay was developed with the recombinant silk protein CBM-AQ12-CBM as a target, the method can be adapted to other recombinant proteins. Variations of the protein tag and Strep-Tactin probe were tested, and it was found that only the combination of Strep-TactinXT and Twin-Strep-tag performed adequately: with this combination, a precision of 95% and an accuracy of 86% were achieved with a linear region from 19 to 400 ng and a limit of quantification at 0.4 pmol. To achieve this, critical optimization steps were preventing nonspecific adsorption and promoting surface adhesion of the target protein to the solid nitrocellulose membrane. The often-overlooked challenges of sample preparation and protein immobilization in quantification assays are discussed and insights into overcoming such issues are provided.

Selective Hydrogen Isotope Exchange Catalysed by Simple Alkali-Metal Bases in DMSO

Dedicated to Proferssor Robert E. Mulvey on the occasion of his 65th birthday. Isotope Exchange processes are becoming the preferred way to prepare isotopically labelled molecules, avoiding the redesign of multistep synthetic protocols. In the case of deuterium incorporation, the most used strategy has employed transition metals, that offer high reactivity under mild reaction conditions. Despite their success, the trade-off is that these metals are precious, so expensive, and often exhibit high toxicity. Therefore, alternative transition-metal-free protocols would be a welcome addition to this field. In this report we show how the simple bases NaHMDS (HMDS=hexamethyldisilazide) and NaCH2SiMe3 can efficiently and selectively promote deuteration of a wide range of C(sp2)-H and C(sp3)-H bonds in DMSO-d6, providing an easy and direct access to deuterated compounds. Heterocycles, fluoroarenes, N-heterocyclic carbenes, amides and other aromatic molecules could be deuterated under mild conditions using catalytic amounts of base. Mechanistic studies along with the isolation and characterisation of reaction intermediates have flagged up the importance of the metalated substrate and metalated solvent in solution, establishing an equilibrium between these compounds is crucial for the success of this approach. An alkali-metal effect was observed, with heavier alkali-metal amides being more reactive at room temperature, but their lower stability at higher temperatures made sodium bases the optimal reagents for Hydrogen Isotope Exchange.

FON: An Innovative Fluorinated Group via Hydroetherification-Type Reactivity

An efficient strategy for preparing the novel O-difluoroalkylhydroxylamine fluorinated functional group, coined FON, is reported. This analogue of medicinally important β-phenethyl ether scaffolds in uniting gem-difluoro and N-O moieties is synthesized in one step via chemo- and regioselectivity metal-free hydroetherification-type additions. As shown, this unique mode of reactivity is realized for a diverse substrate scope and applied to gram-scale synthesis and site-selective deuterium incorporation. Lastly, a mechanistic understanding with implications in Brønsted acid catalysis is offered.

Luminescence Modulation in Boron-Cluster-Based Luminogens via Boron Isotope Effects

Recent advances in luminescent materials highlight the significant impact of hydrogen isotope effects on improving optoelectronic properties. However, the research on the influence of the boron isotope effects on photophysical properties remains underdeveloped. This study focused on exploring the boron isotope effects in boron-cluster-based luminogens. In doing so, we designed and synthesized carborane-based luminogens containing 98 % 10B and 95 % 11B, respectively, and observed distinct photophysical behaviors. Compared to the 10B-enriched luminogens, the 11B-enriched counterparts can significantly enhance luminescence efficiency, prolong emission lifetime, and reduce full-width at half-maximum. Additionally, increased thermal stability, redshifted B-H vibrations, and a fourfold enhanced electrochemiluminescence intensity have also been observed. On the other hand, the biological assessments of a 10B-enriched luminogen reveals low cytotoxicity, high boron uptake, and excellent fluorescence imaging capability, indicating the potential application in boron neutron capture therapy (BNCT). This work presents the first comprehensive exploration on the boron isotope effects in boron clusters, and provides valuable insights into the rational design of organic luminogens for advanced optoelectronic and biomedical applications.

Alkali Metal Amide-Catalyzed α-Deuteration of Sulfides

The catalytic α-deuteration of sulfides was developed under mild conditions by using alkali metal amides [KN(SiMe3)2 and CsN(SiMe3)2] as the catalyst. This approach successfully achieves a selective and efficient H/D exchange reaction of sulfides with D2 without using transition metal catalysts. A series of deuterium-labeled thioanisoles and alkyl methyl sulfides were obtained in good to high levels of deuterium incorporation.

C-H Activation and Hydrogen Isotope Exchange of Aryl Carbamates Using Iridium(I) Complexes Bearing Chelating NHC-Phosphine Ligands

Hydrogen isotope exchange (HIE) via C-H activation constitutes an efficient method for the synthesis of isotopically-enriched compounds, which are crucial components of the drug discovery process and are extensively employed in mechanistic studies. A series of iridium(I) complexes, bearing a chelating phosphine-N-heterocyclic carbene ligand, was designed and synthesized for application in the catalytic HIE of challenging N- and O-aryl carbamates. A broad range of substrates were labeled efficiently, and applicability to biologically-relevant systems was demonstrated by labeling an ʟ-tyrosine-derived carbamate with excellent levels of deuterium incorporation. Combined theoretical and experimental studies unveiled intriguing mechanistic features within this process, in comparison to C-H activation and hydrogen isotope exchange catalyzed by monodentate Ir(I) NHC/phosphine complexes.

Deuteration and Tritiation of Pharmaceuticals by Non-Directed Palladium-Catalyzed C-H Activation in Heavy and Super-Heavy Water

Deuterated and tritiated analogs of drugs are valuable compounds for pharmaceutical and medicinal chemistry. In this work, we present a novel hydrogen isotope exchange reaction of drugs using non-directed homogeneous Pd-catalysis. Aromatic C-H activation is achieved by a commercially available pyridine ligand. Using the most convenient and cheapest deuterium source, D2O, as the only solvent 39 pharmaceuticals were labelled with clean reaction profiles and high deuterium uptakes. Additionally, we describe the first application of non-directed homogeneous Pd-catalysis for H/T exchange on three different pharmaceuticals by using T2O as isotopic source, demonstrating the applicability to the synthesis of radiotracers.

Hydro- and deutero-deamination of primary amines using O-diphenylphosphinylhydroxylamine

While selective defunctionalizations are valuable in organic synthesis, hydrodeamination of primary amines poses challenges. Deuterodeamination, analogous to hydrodeamination, presents even greater difficulties due to its frequently slower deuteration rate, interference by hydrogenation and constraints in deuterated sources. This study introduces a reliable, robust, and scalable hydro- and deuterodeamination method capable of handling various primary amines. Defined by its mild reaction conditions, rapid completion, simplified purification facilitated by water-soluble byproducts, the method leverages deuterium oxide as a deuterium source and employs commercialized O-diphenylphosphinylhydroxylamine for deamination. Applied to a diverse range of biologically active molecules, it has consistently achieved high yields and efficient deuterium incorporation. By synergizing with site-selective C-H functionalization of primary aliphatic amines, our method reveals synthetic strategies utilizing nitrogen atom as a traceless directing group, encompassing deaminative alkylation, 1,1-deuteroalkylation, 1,1-dialkylation, 1,1,1-deuterodialkylation, C-H arylation, and 1,3-deuteroarylation. Emphasizing this innovation, the processes of deaminative degree-controlled deuteration have been developed.

Controlled synthesis of CD2H-ketones

The synthesis of compounds containing partially deuterated groups such as CD2H lacks general methods. These compounds could be important for fine control of metabolic processes in drug discovery, or in the development of multifunctional probes for analysis by complementary spectroscopic techniques. Here, a convenient route to CD2H-methyl ketones is reported through coupling of esters with bis[(pinacolato)boryl]methane and trapping with D2O.

Homogenous Palladium-Catalyzed Dehalogenative Deuteration and Tritiation of Aryl Halides with D2/T2 Gas

Hydrogen isotopically labeled compounds have extensive utility across diverse domains, especially in drug discovery and development. However, synthesis of the labeled compounds with exclusive site selectivity and/or high isotope incorporation is challenging. One widely employed method is heterogeneous palladium(0)-catalyzed (such as Pd/C) dehalogenative deuteration and tritiation with D2/T2 gas. While commonly used, the method faces two long-standing challenges related to insufficient isotope incorporation and functional group tolerance, particularly with aryl bromides and chlorides. These long-standing issues pose a substantial obstacle in the synthesis of deuterated drug molecules and high-specific-activity tritium tracers. Herein, we present a novel palladium catalytic system using Zn(OAc)2 as an additive, enabling novel homogenous dehalogenative deuteration/tritiation using D2/T2 gas. Under mild reaction conditions, a wide range of drug-like aryl halides and pseudohalides undergo selective deuteration with complete isotope incorporation. The reaction displays excellent compatibility with diverse functional groups, including multiple bonds and O/N-benzyl, and cyano groups, which are frequently problematic in the Pd/C reactions. Furthermore, this method was successfully applied to the tritiation of four halogenated pharmaceutically relevant molecules, resulting in predictable high specific activity per halogen atom (26.5-27.7 Ci/mmol). Notably, the developed system allows gram-scale preparation of a deuterium-containing intermediate, a crucial step in synthesizing a deuterium-labeled drug molecule. A key intermediate, Pd(Ar)OAc, is proposed to activate hydrogen gas during dehalogenative deuteration and tritiation, and Zn(OAc)2 plays an essential role in inhibiting Pd poisoning by halides.

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.

Selective monodeuteration enabled by bisphosphonium catalyzed ring opening processes

The selective incorporation of a deuterium atom into small molecules with high selectivity is highly valuable for medical and chemical research. Unfortunately, this remains challenging due to the complete deuteration caused by commonly used hydrogen isotope exchange strategies. We report the development of a photocatalytic selective monodeuteration protocol utilizing C-C bond as the unconventional functional handle. The synergistic combination of radical-mediated C-C bond scission and deuterium atom transfer processes enables the effective constructions of benzylic CDH moieties with high selectivity for monodeuteration. The combinational use of a bisphosphonium photocatalyst, thiol catalyst, and CH3OD deuteration agent provides operationally simple conditions for photocatalytic monodeuteration. Moreover, the photoinduced electron transfer process of the bisphosphonium photocatalyst is elucidated through a series of spectroscopy experiments, identifying a peculiar back electron transfer process that can be regulated by subsequent nucleophilic additions.

Highly Chemoselective Synthesis of α, α-Dideuterio Amines by the Reductive Deuteration of Thioamides Using Mild SmI2-D2O

An efficient and chemoselective protocol for the single-electron-transfer (SET) reductive deuteration of thioamides using SmI2 and D2O is reported. This method uniquely produces α,α-dideuterio amines via a thio-ketyl radical intermediate without generating alcohol byproducts, distinguishing it from the SET reduction of amides. The inherent high reactivity of thioamides obviates the need for ligands like Et3N to improve the reducing power of SmI2, thereby enabling milder reaction conditions that are compatible with a broad range of sensitive functional groups. This protocol tolerates both primary and secondary aliphatic and aromatic thioamides, leading to the synthesis of 27 α,α-dideuterio amines and valuable deuterated nitrogen heterocycles with >95% deuterium incorporations.

Hydrogen isotope labeling unravels origin of soil-bound organic contaminant residues in biodegradability testing

Biodegradability testing in soil helps to identify safe synthetic organic chemicals but is still obscured by the formation of soil-bound 'non-extractable' residues (NERs). Present-day methodologies using radiocarbon or stable (13C, 15N) isotope labeling cannot easily differentiate soil-bound parent chemicals or transformation products (xenoNERs) from harmless soil-bound biomolecules of microbial degraders (bioNERs). Hypothesizing a minimal retention of hydrogen in biomolecules, we here apply stable hydrogen isotope - deuterium (D) - labeling to unravel the origin of NERs. Soil biodegradation tests with D- and 13C-labeled 2,4-D, glyphosate and sulfamethoxazole reveal consistently lower proportions of applied D than 13C in total NERs and in amino acids, a quantitative biomarker for bioNERs. Soil-bound D thus mostly represents xenoNERs and not bioNERs, enabling an efficient quantification of xenoNERs by just measuring the total bound D. D or tritium (T) labeling could thus improve the value of biodegradability testing results for diverse organic chemicals forming soil-bound residues.

Organophotocatalytic Selective Deuteration of Metabolically Labile Heteroatom Adjacent C-H Bonds via H/D Exchange with D2O

We report a general approach for efficient deuteration of the metabolically labile α-C-H bonds of widespread amides and amines. Temporarily masking the secondary amine group as a carbamate allows an unprecedented photoredox hydrogen atom transfer-promoted α-carbamyl radical formation for efficient H/D exchange with D2O. The mild protocol delivers structurally diverse α-deuterated secondary amines including "privileged" piperidine and piperazine structures highly regioselectively with excellent levels of deuterium incorporation (≤100%). Furthermore, we successfully implemented the strategy for α-deuteration of amides, lactams, and ureas with high regioselectivity and high levels of D incorporation. Finally, the observed efficient deuteration of secondary alcohol moieties in late-stage modification of complex amine-containing pharmaceuticals allows for the development of a viable method for efficient α-deuteration of the important functionality.

Population Pharmacokinetics Modeling and Simulation of Deutenzalutamide, A Novel Androgen Receptor Antagonist, in Patients With Metastatic Castration-Resistant Prostate Cancer

Deutenzalutamide is a new molecular entity androgen receptor antagonist. The primary aim of this study was to develop a population pharmacokinetic model of deutenzalutamide and evaluate effects of intrinsic and extrinsic factors on pharmacokinetics. A nonlinear mixed-effects modeling approach was performed to develop the population pharmacokinetic of deutenzalutamide using data from 1 Phase I trial of deutenzalutamide. Goodness-of-fit plots, prediction-corrected visual predictive check, and bootstrap analysis were carried out to evaluate the final model. Simulation for the developed model was used to evaluate the covariate effects on the pharmacokinetics of deutenzalutamide. A 2-compartment model with first-order absorption and elimination from the central compartment was established for deutenzalutamide. The final covariate included body weight on peripheral compartment volume. This is the first research developing the population pharmacokinetic model of deutenzalutamide in patients with metastatic castration-resistant prostate cancer, and it is expected to support the future clinical administration of deutenzalutamide.

Designing chemical systems for precision deuteration of medicinal building blocks

Methods are lacking that can prepare deuterium-enriched building blocks, in the full range of deuterium substitution patterns at the isotopic purity levels demanded by pharmaceutical use. To that end, this work explores the regio- and stereoselective deuteration of tetrahydropyridine (THP), which is an attractive target for study due to the wide prevalence of piperidines in drugs. A series of d0-d8 tetrahydropyridine isotopomers were synthesized by the stepwise treatment of a tungsten-complexed pyridinium salt with H-/D- and H+/D+. The resulting decomplexed THP isotopomers and isotopologues were analyzed via molecular rotational resonance (MRR) spectroscopy, a highly sensitive technique that distinguishes isotopomers and isotopologues by their unique moments of inertia. In order to demonstrate the medicinal relevance of this approach, eight unique deuterated isotopologues of erythro-methylphenidate were also prepared.

Electrocatalytic reductive deuteration of arenes and heteroarenes

The incorporation of deuterium in organic molecules has widespread applications in medicinal chemistry and materials science1,2. For example, the deuterated drugs austedo3, donafenib4 and sotyktu5 have been recently approved. There are various methods for the synthesis of deuterated compounds with high deuterium incorporation6. However, the reductive deuteration of aromatic hydrocarbons-ubiquitous chemical feedstocks-to saturated cyclic compounds has rarely been achieved. Here we describe a scalable and general electrocatalytic method for the reductive deuteration and deuterodefluorination of (hetero)arenes using a prepared nitrogen-doped electrode and deuterium oxide (D2O), giving perdeuterated and saturated deuterocarbon products. This protocol has been successfully applied to the synthesis of 13 highly deuterated drug molecules. Mechanistic investigations suggest that the ruthenium-deuterium species, generated by electrolysis of D2O in the presence of a nitrogen-doped ruthenium electrode, are key intermediates that directly reduce aromatic compounds. This quick and cost-effective methodology for the preparation of highly deuterium-labelled saturated (hetero)cyclic compounds could be applied in drug development and metabolism studies.

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.

Pegylated Phosphine Ligands in Iridium(I) Catalyzed Hydrogen Isotope Exchange Reactions in Aqueous Buffers

The synthesis of a water-soluble, phosphine-pegylated iridium(I) catalyst and its application in hydrogen isotope exchange (HIE) reactions in buffer is reported. The longer polyethylene glycol side chains on the phosphine increased the water solubility independently from the pH. HIE reactions of polar substrates in protic solvents were studied. DFT calculations gave further insights into the catalytic processes. The scope and limitation of the pegylated catalyst was studied in HIE reactions of several complex compounds in borax buffer at pH 9 and the best conditions were applied in a tritium experiment with the drug telmisartan.

Deuterated Alkyl Sulfonium Salt Reagents; Importance of H/D Exchange Methods in Drug Discovery

Deuterated drugs (heavy drugs) have recently been spotlighted as a new modality for small-molecule drugs because the pharmacokinetics of pharmaceutical drugs can be enhanced by replacing C-H bonds with more stable C-D bonds at metabolic positions. Therefore, deuteration methods for drug candidates are a hot topic in medicinal chemistry. Among them, the H/D exchange reaction (direct transformation of C-H bonds to C-D bonds) is a useful and straightforward method for creating novel deuterated target molecules, and over 20 reviews on the synthetic methods related to H/D exchange reactions have been published in recent years. Although various deuterated drug candidates undergo clinical trials, approved deuterated drugs possess CD3 groups in the same molecule. However, less diversification, except for the CD3 group, is a problem for future medicinal chemistry. Recently, we developed various deuterated alkyl (dn-alkyl) sulfonium salts based on the H/D exchange reaction of the corresponding hydrogen form using D2O as an inexpensive deuterium source to introduce CD3, CH3CD2, and ArCH2CD2 groups into drug candidates. This concept summarises recent reviews related to H/D exchange reactions and novel reagents that introduce the CD3 group, and our newly developed electrophilic dn-alkyl reagents are discussed.