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-d6/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.