Stereoselective Synthesis of New Glycoconjugated Ruthenium(II)-Arene Complexes as Potential Anticancer Agents

Novel ruthenium complexes based on triphenylphosphine ligands¹ were conjugated with different carbohydrate units, in order to increase the selectivity towards tumor cells. Indeed, these new glycoconjugates could exploit the glucose membrane transporters (GLUTs) to drastically increase the uptake of the antitumor complexes in the cancer cells. The synthesis of these glycoconjugated ruthenium complexes followed three different approaches for the construction of the glycophosphine moieties: the first is an appealing methodology for the synthesis of 2,3- unsaturated glycosides, starting from glycal derived vinyl epoxides as new and powerful glycosyl donors.² A second approach consisted in a more classic synthetic pathway, starting from trichloroacetimidate as the glycosyl donor. The last one consisted in a Sonogashira coupling between the glycosyl donor (acetylated D-mannose) bearing a terminal triple bond and a bromo-substituted triphenylphosphine.³ Interestingly, from the first approach it is possible to obtain new glycoconjugates in which the glycoside portion is directly connected to triphenylphosphine ligand (type A complexes); from the second and third ones, the glycoside moiety is connected to the triphenylphosphine ligand through a linker (type B complexes). All these systems are currently under investigation to evaluate their antitumor activity. [1] Biancalana, L.; Pratesi, A.; Chiellini, F.; Zacchini, S.; Funaioli, T.; Gabbiani, C.; Marchetti, F. “Ruthenium arene complexes with triphenylphosphane ligands: cytotoxicity towards pancreatic cancer cells, interaction with model proteins, and effect of ethacrynic acid substitution” New Journal of Chemistry 2017, pp. 1-45. [2] Di Bussolo, V.; Caselli, M.; Pineschi, M.; Crotti, P. “New Stereoselective β-Glycosylation via a Vinyl Oxirane Derived from D-Glucal”,Org. Lett. 2002, 4, 3695-3698. [3] Smith, J.N; Hook, J. M.; Lucas, N. T. “Superphenylphosphines: NanographeneBased Ligands That Control Coordination Geometry and Drive Supramolecular Assembly” J. of Am. Chem. Soc. 2018, 140, 1131-1141.