Radiosynthesis of three [11C]ureido-substituted benzenesulfonamides as PET probes for carbonic anhydrase IX in tumors

Three ureido-substituted benzenesulfonamides 1a–c have been developed as potent inhibitors for carbonic anhydrase IX, which is overexpressed in hypoxic tumors. In this study, we labeled these unsymmetrical ureas 1a–c using [11C]phosgene ([11C]COCl2) as a labeling agent with the expectation that [11C]1a–c could become promising positron tomography probes for imaging carbonic anhydrase IX in tumors. The strategy for radiosynthesis of [11C]1a–c was to react hydrochloride of anilines 2a–c with [11C]COCl2 to give isocyanate [11C]4a–c, followed by a reaction with 4-aminobenzenesulfonamide (3).

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