Benzothiazole–Triphenylphosphonium Conjugates: Synthesis, In Silico Analysis, and Exploratory In Vitro Effects on HT‐29 Colorectal Cancer Cell Viability

Abstract

A series of (2‐((6‐benzo[d]thiazol‐2‐yl)amino)‐2‐oxoethyl)triphenylphosphonium (TPP) derivatives (4a–f) was synthesised and evaluated in a colorectal cancer (CRC) cell model. Compounds were obtained in high yields via acylation of aminobenzothiazoles with chloroacetyl chloride, followed by quaternization with triphenylphosphine. A computer‐aided drug‐design approach combining quantitative structure–activity relationship, molecular docking, and molecular dynamics simulations was used to guide prioritization and explore putative protein–ligand interactions in silico. Antiproliferative effects of conjugates 4a–f on cell viability were assessed in HT‐29 human CRC cells (mutant p53 model), using a resazurin viability assay. Compounds 4b and 4c showed concentration‐responsive activity, with IC50 values of 174 and 153 µM, respectively, identifying them as the most active derivatives in this preliminary phenotypic screen. Gene expression analysis showed upregulation of p21 mRNA, while MDM2 mRNA showed minimal changes, providing preliminary transcript‐level observations in response to compound exposure. As all assays were performed in p53‐mutant HT‐29 cells, these effects are interpreted as exploratory stress‐related responses rather than evidence of wild‐type p53 pathway reactivation or direct inhibition of the p53–MDM2 interaction. The study provides an integrated workflow combining synthesis of an unreported benzothiazole–TPP scaffold, computational prioritization, and preliminary biological evaluation. Despite modest antiproliferative activity, results identify initial structure–activity trends within the series, establishing a foundation for future optimisation.