Library synthesis of Slack potassium channel activators based on a high-throughput screening hit

Introduction: Fragile X syndrome (FXS) is an X-linked disorder that is associated with cognitive disabilities. Previous studies have shown an association between a mutation in the FMR1 gene and FXS. The mutation is an overexpansion of the promoter region, resulting in hypermethylation and silencing of fragile X mental retardation protein 1 (FMRP).1 FMRRP is necessary for activating Slack proteins, which are important for normal neuronal activity.2, 3 Objective: To synthesize a library of small molecules in two distinct regions of an HTS hit chemotype made of sulfonamides and heteroaryl amines for functional testing versus Slack channels. Methods: Solution-phase and microwave-assisted organic chemistry were utilized to synthesis small molecules. Purification of compounds involved using automated liquid chromatography. Final compounds were characterized through NMR and HRMS data obtained from a Bruker Fourier 300HD and Agilent 6230 time-of-flight LC/MS, respectively. Activity of new compounds versus Slack was measured utilizing a Thallium flux assay in HEK293 cells stably expressing WT Slack channels. Results: SAR studies conducted around hit compound VU0521448 have thus far discovered analogs showing only weak activity against Slack proteins. Data for SAR studies developed around hit compound VU0521398 are in the process of being collected. Conclusion: The sulfonamide library prepared using different sulfonyl chloride substituents gave some analogs with weak activity in activating Slack proteins. Additional SAR studies will be carried out to examine other aspects of the chemotype, such as modifying the piperidine ring to pyrroline or pyrrolidine. FUNDING STATEMENT Research reported in this publication was supported by the National Heart, Lung, and Blood Institute (R25HL125447) and the National Institute of Mental Health (R21MH125257), both of the National Institutes of Health. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Health.