Synthesis and anticancer activity studies of ferrocenyl-thymine-3,6-dihydro-2H-thiopyranes - A new class of metallocene-nucleobase derivatives

A convenient synthesis of ferrocenyl-4-thiothymine-3,6-dihydro-2H-thiopyrane (3) and ferrocenylthymine-3,6-dihydro-2H-thiopyrane (4) by a hetero-Diels-Alder cycloaddition reaction is reported. These complexes represent new class of ferrocenyl nucleobase derivatives. The 2H-thiopyrane ring mimics the sugar subunit present in natural nucleosides and nucleotides. The X-ray crystal structure analysis of the precursor thioketone (1) showed that individual molecules of 1 form H-bonded dimers in the solid state. Compounds 3 and 4 were tested in vitro for their antiproliferative activity against human colon carcinoma HT-29, estrogen receptor-responsive human breast adenocarcinoma MCF-7, estrogen-negative human breast adenocarcinoma MDA-MB-231, human promyelocytic leukemia HL-60 and human monocytic MonoMac6 cancer cells. Ferrocenyl-4-thiothymine-3,6-dihydro-2H-thiopyrane 3 showed a cytostatic effect on MonoMac6, MCF-7 and HL-60 cell lines, but was devoid of activity on MDA-MB-231 and HT-29 cells. In contrast, all cell lines tested were sensitive toward thymine derivative 4. Proapoptic activity of 3 and 4 was confirmed by means of acridine orange/ethidium bromide (AO/EB) double-staining assay. (C) 2015 Elsevier B.V. All rights reserved.