The preparation of deuterium labeled fexinidazole, a 5-nitroimidazole drug candidate for the treatment of Human African Trypanosomiasis, and its two main metabolites (fexinidazole sulfoxide and fexinidazole sulfone) for use as internal standards for liquid chromatography-mass spectrometry are reported. Additionally, the synthesis of a 14 C-labeled version of fexinidazole for absorption, distribution, metabolism, and excretion studies is also described via a five-step procedure starting from commercially available potassium [14 C]cyanide.

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The preparation of [(14) C]tribendimidine, a broad-spectrum anthelmintic agent related to amidantel, and its use during excretion and metabolism studies in the rat are described in this paper.

SUMMARYThe synthesis in eight steps of the title compound from the commercially available[2O-"C]pregnenolone 1 is described. The expected I-[4-methyl-3-oxo-4-aza-5a-androstane-17~-[14C]carbonyl]-1,3-diisopropylurea ([14C]FCE 26073) wasobtained with a radiochemical purity higher than 97% and a specific activity of 2.03 GBq/mmol. An overall radiochemical yield of21% was achieved from 1.

SummaryJTT-501 specifically labelled with 13 C was obtained via a four-step synthesis at an isotopic enrichment level of 99% and in 14% overall chemical yield starting from 4-hydroxy-[ring-U-13 C 6 ]benzaldehyde (3). The hydrogenation of