Synthesis of the main long-term dihydroxylated metabolite of LGD-4033 as reference material for doping control analysis

Code: 21A17EP

LGD-4033 (Ligandrol), is a Selective Androgen Receptor Modulator (SARM) with a pyrrolidinyl-benzonitrile core structure. Although it displays promising muscle-and bone-anabolic properties, it is not yet
a drug approved for clinical use and it is included in the World Anti-Doping Agency’s (WADA’s) Prohibited List. Nonetheless, lately numerous related adverse analytical findings have been reported by
doping control laboratories worldwide.

Prior studies related to the detection of LGD-4033’s illicit use by LC–MS analysis of human urine have indicated two isomeric dihydroxylated metabolites as the preferred target analytes. Their monitoring could extend the detection for at least twenty-one days post-administration of the parent compound. For doping control laboratories to check, improve and properly validate their methods of detection of these metabolites it is crucial that relevant reference materials are available for comparison of chromatographic retention times and mass spectrometric properties. However, these compounds are not readily available and their structure has only partially been elucidated. Furthermore, their bis-hemiaminal nature questions their stability for long-term handling and storage. To address the abovementioned challenges, proposed herein is the chemical synthesis of all possible diastereoisomers of the main dihydroxylated LGD-4033 metabolite. Two alternative synthetic approaches that employ as starting material either the parent compound or commercially available building blocks will be investigated at small scale. NMR and LC-MS analysis of the synthesized diastereoisomers in comparison with the ones reported for the targeted metabolite is anticipated to clarify its stereochemistry and stability. To secure material to be distributed among WADA accredited laboratories, the synthesis of the diastereoisomer(s) that match the chromatographic and mass spectrometric properties of the in vivo observed metabolite(s) and exhibit stability that permits their use a reference material will be pursued at a larger scale.