Multiple peer-reviewed studies establish that stable isotopes are widely used in pharmaceutical development, metabolic tracking, and the synthesis of deuterated active pharmaceutical ingredients.
A recent review identified the problem of lower isotopologues in deuterated active pharmaceutical ingredients (APIs) as a critical issue in this area of medicinal chemistry. In this Perspective, the relationship between overall enrichment and isotope distribution for deuterated APIs is discussed. Deuterated APIs are divided into single deuterium, methyl-d3, and polydeuterated compounds. For the latter category, distribution calculations demonstrate that the parent deuterated API contains significant quantities of the lower isotopologues. As an alternative to the use of overall enrichment to describe these compounds, it is suggested that describing these compounds with a distribution profile should be preferred, giving an accurate and defensible description of the API. Using this approach, the lower isotopologues become an integral part of the API and not an impurity.
Incorporating stable isotopes into bioactive molecules is crucial in pharmaceutical development, particularly for metabolic studies where higher mass isotopologs of candidate compounds are required. Here we present an isotope exchange method for synthesizing isotopically enriched pyrimidines. By deconstructing pyrimidines into vinamidinium salts and reconstructing them with deuterium, 13C, and 15N-enriched amidines, we achieve high isotopic enrichment across various substitution patterns, including complex drug-like pyrimidine derivatives. The process involves a Tf2O-mediated ring-opening and ring-closing sequence to form a pyrimidinium ion, followed by cleavage to the vinamidinium salt with pyrrolidine. Cyclization with labeled amidines under basic conditions then forms the labeled pyrimidine. Additionally, we deuterated the 5-position of pyrimidines using this approach to offer further versatility in generating higher mass isotopologs.
Publisher Summary This chapter describes operation and capabilities of liquid chromatography–mass spectrometry (LC–MS) instrumentation and explores how it can be best used for stable isotope tracer studies of drug disposition. The combined technique of LC–MS is widely recognized as the most powerful tool available for analysis with high sensitivity and specificity of low concentrations of drugs and their metabolites in biological matrices. The ability of LC–MS to distinguish and measure compounds labeled with stable isotopes with the same analytical prowess makes it the obvious choice when tracer studies with pharmaceuticals are considered. LC–MS interfaces are conveniently divided into two groups: (1) those that deliver the LC analytes to a conventional ion source for subsequent ionization, and (2) those that ionize the analytes and transmit the ions to the mass spectrometer. These are referred transport and ionization type interfaces, respectively. Transport interfaces deliver analytes from the High-performance liquid chromatography (HPLC) eluate to a conventional MS ion source where they are ionized and subsequently mass analyzed. They include the direct liquid introduction (DLI) and moving belt (MB) interface.
Everything we examined (3)
This check searched the claim as stated. It did not run a separate search for evidence against it.