Synthesis, anti-proliferative activity and SAR studies of novel 5-(3-indolyl)-5H-thiazolo[4,3-b][1,3,4]thiadiazoles tethered with steroid moieties

Abstract

A new series of the fused thiazolo[4,3-b]-1,3,4-thiadiazoles 2a-e have been synthesized via one-pot reaction of N-substituted indole-3-carboxaldehydes 1a-e with thioglycolic acid and thiosemicarbazide under grinding condition. Condensation reaction of 2a-e with acetylated epiandrosterone and progesterone afford the corresponding Schiff's bases 3a-e and 4a,b, respectively. Besides, the chloroacetylation of 2a-e in situ by chloroacetyl chloride yielded the chloroacetamides 5a-e. The reaction of 5a-e with 3-amino-pyrazolopyridine derivative 6 provided the goal 2-[(steroids)-2H-pyrazolo[3,4-b]pyridin-3-ylamino]-5- (indoles)-thiazolo[4,3-b][1,3,4]thiadiazol-2-yl]-acetamides 7a-e. The analytical and spectral data of the entire target compounds 3a-e, 4a,b and 7a-e were compatible with their structures. Compounds 3a-e, 4a,b, and 7a-e were selected to be screened in vitro against different cancer cell lines, namely A-549, HC-T116, MCF-7, and PC3 using MTT assay. The antiproliferative activity results implied that compounds 3a-e, 4a, and 7e showed excellent growth inhibitory activity toward the human colon cancer cell (HCT-116) with IC50 value ranging from 7.25-38.92 μM/ml in comparison to the reference drug doxorubicin with IC50 of 48.02 μM/ml. Interestingly, compound 3e found to be the most active one towards A-549, HCT-116, and PC3 cancer cell lines with IC50 of 27.05, 12.69, and 24.61μM/ml in comparison with doxorubicin of IC50 39.74, 48.02, and 34.77μM/ml, respectively. In addition, molecular docking studies helped to rationalize the binding interaction of the most active compounds toward human colon cancer cell (HCT-116) 3a-e, 4a and 7a with the anti-apoptotic Bcl-2 and the result revealed that the docking of compounds was more potent compared co-crystalline ligand.