Tethering Carbohydrates to the Vinyliminium Ligand of Antiproliferative Organometallic Diiron Complexes

Four propargyl O-glycosides derivatized with mannose, glucose, and fructose moieties were synthesized and then incorporated within a diiron structure as part of a vinyliminium ligand. Hence, six glycoconjugated diiron complexes, [2-5]CF₃SO₃ (see Scheme 1) and the nonglycosylated analogues [6a-b]CF₃SO₃, were obtained in high yields and unambiguously characterized by elemental analysis, mass spectrometry, and IR and multinuclear NMR spectroscopies. All compounds exhibited a significant stability in DMSO-d ₆/D₂O solution, with 63-89% of the complexes unaltered after 72 h at 37 °C and also in the cell culture medium. The cytotoxicity of [2-6]CF₃SO₃, as well as that of previously reported 7 and 8, was assessed on CT26 (mouse colon carcinoma), U87 (human glioblastoma), MCF-7 (human breast adenocarcinoma), and RPE-1 (human normal retina pigmented epithelium) cell lines. In general, the IC₅₀ values correlate with the hydrophobicity of the compounds (measured as octanol-water partition coefficients) and do not show an appreciable level of selectivity against cancer cells with respect to the nontumor ones.