| Summary: | <i>S</i>-trityl-<span style="font-variant: small-caps;">l</span>-cysteine (<b>STLC</b>) is a well-recognized lead compound known for its anticancer activity owing to its potent inhibitory effect on human mitotic kinesin Eg5. <b>STLC</b> contains two free terminal amino and carboxyl groups that play pivotal roles in binding to the Eg5 pocket. On the other hand, such a zwitterion structure complicates the clinical development of <b>STLC</b> because of the solubility issues. Masking either of these radicals reduces or abolishes <b>STLC</b> activity against Eg5. We recently identified and characterized a new class of nicotinamide adenine dinucleotide-dependent deacetylase isoform 2 of sirtuin protein (SIRT2) inhibitors that can be utilized as cytotoxic agents based on an <i>S</i>-trityl-<span style="font-variant: small-caps;">l</span>-histidine scaffold. Herein, we propose new <b>STLC</b>-derived compounds that possess pronounced SIRT2 inhibition effects. These derivatives contain modified amino and carboxyl groups, which conferred <b>STLC</b> with <b>SIRT2</b> bioactivity, representing an explicit repurposing approach. Compounds <b>STC4</b> and <b>STC11</b> exhibited half maximal inhibitory concentration values of 10.8 ± 1.9 and 9.5 ± 1.2 μM, respectively, against SIRT2. Additionally, introduction of the derivatizations in this study addressed the solubility limitations of free <b>STLC</b>, presumably due to interruption of the zwitterion structure. Therefore, we could obtain drug-like <b>STLC</b> derivatives that work by a new mechanism of action. The new derivatives were designed, synthesized, and their structure was confirmed using different spectroscopic approaches. In vitro and cellular bioassays with various cancer cell lines and in silico molecular docking and solubility calculations of the synthesized compounds demonstrated that they warrant attention for further refinement of their bioactivity.
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