Synthesis of stable isotope labelled internal standards for drug–drug interaction (DDI) studies

Scalable biocatalytic C-H oxyfunctionalization reactions

Catalytic C-H oxyfunctionalization reactions have garnered significant attention in recent years with their ability to streamline synthetic routes toward complex molecules. Consequently, there have been significant strides in the design and development of catalysts that enable diversification through C-H functionalization reactions. Enzymatic C-H oxygenation reactions are often complementary to small molecule based synthetic approaches, providing a powerful tool when deployable on preparative-scale. This review highlights key advances in scalable biocatalytic C-H oxyfunctionalization reactions developed within the past decade.

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

Hydrogen isotopes are unique tools for identifying and understanding biological and chemical processes. Hydrogen isotope labelling allows for the traceless and direct incorporation of an additional mass or radioactive tag into an organic molecule with almost no changes in its chemical structure, physical properties, or biological activity. Using deuterium-labelled isotopologues to study the unique mass-spectrometric patterns generated from mixtures of biologically relevant molecules drastically simplifies analysis. Such methods are now providing unprecedented levels of insight in a wide and continuously growing range of applications in the life sciences and beyond. Tritium (³ H), in particular, has seen an increase in utilization, especially in pharmaceutical drug discovery. The efforts and costs associated with the synthesis of labelled compounds are more than compensated for by the enhanced molecular sensitivity during analysis and the high reliability of the data obtained. In this Review, advances in the application of hydrogen isotopes in the life sciences are described.

An efficient synthesis of deuterium-labeled degarelix acetate, a third-generation gonadotropin-releasing hormone receptor antagonist

Degarelix acetate, a third-generation gonadotropin-releasing hormone receptor antagonist, shows great potential in the treatment of many androgen-related diseases. To support clinical studies of degarelix acetate, deuterium-labeled degarelix is highly desired for use as an internal standard. Using D₂ O/D₃ PO₄ as a deuterium source, 2-amino-3-(naphthalen-2-yl)propanoic acid was converted to deuterated degarelix acetate in 13 steps and in 14% overall yield.

Burgess iridium(I)-catalyst for selective hydrogen isotope exchange

We have evaluated the commercially available Burgess catalyst in hydrogen isotope exchange reactions with several substrates bearing different directing group functionalities and have obtained moderate to high (50%-97%D) deuterium incorporations. The broad applicability in hydrogen isotope exchange reactions makes the Burgess catalyst a possible alternative compared to other commercially available iridium(I)-catalysts.

Hydrogen-deuterium exchange of aromatic amines and amides using deuterated trifluoroacetic acid

The H-D exchange of aromatic amines and amides, including pharmaceutically relevant compounds such as acetaminophen and diclofenac, was investigated using CF3COOD as both the sole reaction solvent and source of deuterium label. The described method is amenable to efficient deuterium incorporation for a wide variety of substrates possessing both electron-donating and electron-withdrawing substituents. Best results were seen with less basic anilines and highly activated acetanilides, reflecting the likelihood of different mechanistic pathways.

Preparation of labeled human drug metabolites and drug-drug interaction-probes with fungal peroxygenases

Enzymatic conversion of a drug can be an efficient alternative for the preparation of a complex metabolite compared with a multi-step chemical synthesis approach. Limitations exist for chemical methods for direct oxygen incorporation into organic molecules often suffering from low yields and unspecific oxidation and also for alternative whole-cell biotransformation processes, which require specific fermentation know-how. Stable oxygen-transferring biocatalysts such as unspecific peroxygenases (UPOs) could be an alternative for the synthesis of human drug metabolites and related stable isotope-labeled analogues. This work shows that UPOs can be used in combination with hydrogen/deuterium exchange for an efficient one-step process for the preparation of 4'-OH-diclofenac-d6. The scope of the reaction was investigated by screening of different peroxygenase subtypes for the transformation of selected deuterium-labeled substrates such as phenacetin-d3 or lidocaine-d3. Experiments with diclofenac-d7 revealed that the deuterium-labeling does not affect the kinetic parameters. By using the latter substrate and H2 (18) O2 as cosubstrate, it was possible to prepare a doubly isotope-labeled metabolite (4'-(18) OH-diclofenac-d6). UPOs offer certain practical advantages compared with P450 enzyme systems in terms of stability and ease of handling. Given these advantages, future work will expand the existing 'monooxygenation toolbox' of different fungal peroxygenases that mimic P450 in vitro reactions.

Selected scientific topics of the 11th International Isotope Symposium on the Synthesis and Applications of Isotopes and Isotopically Labeled Compounds

This micro-review describes hot topics and new trends in isotope science discussed at the 11th International Isotope Symposium on the Synthesis and Applications of Isotopes and Isotopically Labeled Compounds from a personal perspective.