Synthesis of both 14 C‐ and 3 H‐ labelled trospectomycin and the assessment of their utility in biological studies

Three radiolabelled forms of trospectomycin (6′‐n‐propylspectinomycin sulphate hydrate) have been synthesised, namely [8′‐ 14 C]‐, [6′,7′‐ 3 H]‐, and [5′,6′,7′‐ 3 H]‐trospectomycin. Although all three forms of the drug are metabolically stable and therefore suitable for use in animal studies the 14 C compound is produced in poor yield as is the [6′,7′‐ 3 H]trospectomycin. On the other hand, the [5′,6′,7′‐ 3 H]‐form is produced in good yield and appears to be the labelled form of choice. Following subcutaneous administration of any of the labelled forms to rats, more than 50% of the dose was excreted in the urine as unchanged drug during the first 6h after dosing. Approximately 80% and 10% of the dose appeared in the urine and faeces respectively after 6 days.