A novel no‐carrier‐added submicromolar scale radiosynthesis of [S‐methyl‐14C]‐florfenicol

In this paper is reported a novel reaction scheme for the no‐carrier‐added submicromolar scale radiosynthesis of S‐methyl‐¹⁴C]‐florfenicol that has been newly designed, developed and employed by us successfully. The ¹⁴C]‐product was obtained in an overall radiochemical yield of 30% based on ¹⁴C]‐methyl iodide taken for the reaction with a radiochemical purity of more than 96%. The specific activity of the product was ~50 mCi (1.85 GBq)/mmol. Chlorosulfonation of compound I was followed by sodium salt formation in situ and it was succeeded by the introduction of ¹⁴C]‐methyl group by coupling with ¹⁴C]‐CH₃I. Subsequently, the oxazolidin‐2‐one protecting group was opened up by a reaction with sulfuric acid in dioxane and later, the amino group was dichloroacetylated with methyl‐2,2‐dichloroacetate in triethylamine to obtain S‐methyl‐¹⁴C]‐florfenicol.