Synthesis and in vitro antitumour screening of 2-(β-d-xylofuranosyl)thiazole-4-carboxamide and two novel tiazofurin analogues with substituted tetrahydrofurodioxol moiety as a sugar mimic

2-(β-d-xylofuranosyl)thiazole-4-carboxamide (2) and two new tiazofurin analogues with 5-hydroxymethyl-2-methyl-tetrahydro-furo[2,3-d][1,3]dioxol-6-ol moiety as a sugar mimic (27 and 28) have been synthesized and evaluated for their in vitro antitumour activity against a panel of human tumour cell lines (K562, HL 60, Jurkat, Raji and HeLa). In contrast to previous literature reports, a metabolic MTT assay revealed remarkable cytotoxicity of 2 against K562 (IC50 = 0.15 μM) and HL-60 (IC50 = 0.13 μM) cells. Flow cytometry data suggest that cytotoxic effects of analogue 2 in the culture of K562 cells might be mediated by apoptosis, in opposite to tiazofurin, which did not induce apoptosis of K562 cells after 24 h, thus suggesting a different mechanism of action. All three analogues 2, 27 and 28 were also active against Jurkat, Raji and HeLa cells, with IC50 values in the range from 0.06 to 5.61 μM, but were completely inactive against the normal foetal lung fibroblasts (MRC-5).