Thiosemicarbazone derivatives bearing a dioxaphosphorinane ring: Synthesis, crystal structure, DFT calculation, in vitro antiproliferative activity against colorectal cancer cells, in silico docking and ADMET investigations

• New thiosemicarbazones (TSCs 2 ) bearing 1,3,2-dioxaphosphorinane cycles were prepared • NMR, SC-XRD and FT-IR were employed to investigate the structure of TSCs 2 • DFT calculations confirm in line with the experimental data a higher stability of the Z isomer with respect to the E isomer • In vitro antiproliferative activity against HT29 and LS174 tumor cell lines revealed that some TSC 2 compounds exhibit potent activity • In silico docking investigations with DNA topoisomerase IIα were conducted • In silico ADMET profiles were established indicating adequate values To design promising new bioactive compounds endowed with anti-tumor activity, we synthesized a series of isomeric phosphonated thiosemicarbazones (TSCs) 2 bearing a six-membered dioxaphosphorinane cycle. The targeted TSCs were obtained in satisfying yields under mild conditions by reaction between β-cycloalkoxyphosphonated hydrazones 1 of type R 1 R 2 C(CH 2 O) 2 P(=O)CH 2 -C{=N-N(H)R 5 }C(H)R 3 R 4 ( 1a R 1 = R 2 = H, R 3 = Me, R 4 = Ph; 1b R 1 = R 2 = H, R 3 = R 4 =Me; 1c R 1 = R 2 = Me, R 3 = H, R 4 = Bn) and various aliphatic and aromatic isothiocyanates. The formula of the synthesized TSCs correspond to R 1 R 2 C(CH 2 O) 2 P(=O)CH 2 {C=N-NH(C=S)-NH-R 5 }CHR 3 R 4 ( 2a R 1 = R 2 = H, R 3 = Me, R 4 = R 5 = Ph; 2b R 1 = R 2 = H, R 3 = Me, R 4 = Ph, R 5 = Cy; 2c R 1 = R 2 = H, R 3 = Me, R 4 = Ph, R 5 = Bn; 2d R 1 = R 2 = H, R 3 = R 4 = Me, R 5 = Ph; 2e R 1 = R 2 = Me, R 3 = H, R 4 = R 5 = Ph). The chemical structures of the novel thiosemicarbazones were assessed in solution by 31 P, 13 C, 1 H NMR and IR spectroscopy. Since several derivates occur as mixtures of Z/E isomers in solution, the structural analysis was further extended by mechanistic elucidation, single-crystal X-ray diffraction analysis (SC-XRD), Hirshfeld surface analysis and computational investigation. The global reactivity parameters of TSCs 2a, 2d and 2e were determined using Frontier Molecular Orbital (FMO) analysis. Compounds 2a, 2b, 2c and 2e were then screened for their in vitro antiproliferative activity against two human colorectal HT29 and LS174 tumor cell lines. Cell viability studies revealed that compound 2b exhibits the most potent antiproliferative activity. To gain insight into the mechanism of action of TSCs 2 , an in-silico docking study of derivatives 2a-d with DNA topoisomerase IIα was conducted. Furthermore, an in silico ADME/Tox profile was established, indicating adequate values in accordance with the Lipinsky rules of five. The druglikeness levels and bioavailability were also investigated.