Novel Tricyclo[4.2.1]Nonane and Bicyclo[2.2.1]Heptane Derivatives: Synthesis, <i>in Vitro</i> Biological Activities and <i>in Silico</i> Studies

The target benzothiazole derivatives (8a-g) were synthesized starting from norbornene. The addition of dichloroketene to norbornene followed by the reduction of chlorine atoms were synthesized tricyclo[4.2.1.02,5]non-7-en-3-one (4). The condensation of benzaldehyde derivatives with compound 4 were obtained chalcone analogs (6a-g). Finally, benzothiazole derivatives (8a-g) were obtained by the reaction of the chalcone analogs with 2-aminobenzothiol in an acidic medium. The antiproliferative activities of compounds 6a-g and 8a-g were determined against C6 (rat brain tumor) and HeLa (human cervical carcinoma) cell lines using a BrdU cell proliferation ELISA assay with 5-fluorouracil (5-FU) as a standard. In both series, when compared with 5-FU (IC₅₀=3.8 μM for C6 and 16.33 μM for HeLa), the most active compounds against C6 cells were 6a and 8g with IC₅₀ values of 14.13 μM and 29.99 μM, respectively. With this, 6a, 6e, 6f, and 8b were the most active compounds against HeLa cells with IC₅₀ values of 0.8, 1.21, 19.33 and 18.13 μM, respectively. Additionally, the SwissADME online web tool was used to predict the physicochemical and ADME properties of the tested compounds. The results showed that all compounds possess promising predicted physiochemical and pharmacokinetic properties and comply with Lipinski's rule of 5, indicating that they are predicted to be orally bioavailable that they possess a predicted bioavailability score of 0.55. Furthermore, in the SwissADME Boiled-Egg chart, all compounds showed high predicted GIT absorption, while compounds 6a-g showed blood-brain barrier (BBB) permeation, and compounds 8a-g did not. Moreover, none of the compounds was (P-gp) substrates. This study investigated the potential interactions between the antiapoptotic proteins Bcl-2, Bcl-xl, Bcl-w, Brag-1, Bfl-1, and Mcl-1 and compounds 6a, 8b, and 8g through molecular docking studies. The findings suggest that these compounds may effectively inhibit antiapoptotic proteins, as evidenced by significant hydrogen bonds and hydrophobic interactions, particularly with Bcl-xl.