Synthesis of typical sulfonamide antibiotics with [14C]- and [13C]-labeling on the phenyl ring for use in environmental studies

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Background Due to their widespread use, sulfonamide antibiotics (SAs) have become ubiquitous environmental contaminants and thus a cause of public concern. However, a complete understanding of the behavior of these pollutants in complex environmental systems has been hampered by the unavailability and high cost of isotopically labeled SAs. Results Using commercially available uniformly [ 14 C]- and [ 13 C]-labeled aniline as starting materials, we synthesized [phenyl-ring- 14 C]- and [phenyl-ring- 13 C]-labeled sulfamethoxazole (SMX), sulfamonomethoxine (SMM), and sulfadiazine (SDZ) in four-step (via the condensation of labeled N -acetylsulfanilyl chloride and aminoheterocycles) or five-step (via the condensation of labeled N -acetylsulfonamide and chloroheterocycles) reactions, with good yields (5.0–22.5% and 28.1–54.1% for [ 14 C]- and [ 13 C]-labeled SAs, respectively) and high purities (> 98.0%). Conclusion The synthesis of [ 14 C]-labeled SAs in milligram amounts enables the preparation of labeled SAs with high specific radioactivity. The efficient and feasible methods described herein can be applied to the production of a variety of [ 14 C]- or [ 13 C]-labeled SAs for studies on their environmental behavior, including the fate, transformation, and bioaccumulation of these antibiotics in soils and aqueous systems.