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-(14)C]-florfenicol that has been newly designed, developed and employed by us successfully. The [(14)C]-product was obtained in an overall radiochemical yield of 30% based on [(14)C]-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 [(14)C]-methyl group by coupling with [(14)C]-CH3 I. 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-(14)C]-florfenicol.