Design And Synthesis Of An Easily Obtainable Maleimide Reagent N-[2-(4-[F-18]Fluoro-N-Methylbenzenesulfonamido)Ethyl]Maleimide ([F-18]Fbsem) To Radiolabel Thiols In Proteins

An easily obtainable thiol-selective labeling reagent [F-18]FBSEM (N-[2-(4-[F-18]fluoro-N-methylbenzenesulfonamido)ethyl]maleimide) was developed. The advantage of the design is that the precursor and [F-18]FBSEM have the same backbone and backbone construction is not required; in contrast, known thiol-specific labeling reagents do require backbone construction, and this is thought to be the cause of their complicated synthesis. [F-18]FBSEM was successfully obtained in higher yield (25%) and in a simpler way (two fluorination and deprotection steps in 65 min) than the widely used [F-18]FBEM (N-[2-(4[F-18]fluorobenzamide)ethyl]maleimide). The labeling efficacy of [F-18]FBSEM was confirmed by conjugation with glutathione. [F-13]FBSEM is a promising labeling agent for proteins.