Platinum-group metal half-sandwich complexes with C-glucopyranosyl 1,2,3-triazoles and isoxazoles as ligands: synthesis and evaluation as antineoplastic and antimicrobial agents

Half-sandwich complexes of platinum-group metals are a widely studied subgroup of organometallic compounds with promising anticancer and antimicrobial properties. Recently, we have published a set of polyhapto arene/arenyl Ru(II), Os(II), Ir(III) and Rh(III) complexes with hetaryl-substituted 1-N-glucopyranosyl-1,2,3-triazole and C-glycopyranosyl-1,3,4- and -1,2,4-oxadiazole-type N,N-bidentate ligands, several of which exhibited (sub)micromolar antineoplastic and bacteriostatic potencies. The structure-activity relationships of these series indicated that the nature of the azole ring and its way of connection to the pyranoid sugar unit played crucial roles in the biological activity of such complexes. In order to further study the influence of the five-membered heteroaromatic moiety, in this work we have synthesised new complexes with O-protected 4-C-(β-D-glucopyranosyl)-1-(pyridin-2-yl)-1,2,3-triazoles and 5-C-(β-D-glucopyranosyl)-3-(pyridin-2-yl)-isoxazoles as N,N-chelating ligands of η6-p-cymRu(II)/Os(II) and η5-Cp*-Ir(III)/Rh(III) complexes and have studied their cytostatic and antibacterial properties. All but the Rh(III)-derived complexes exerted cytostasis on a plethora of neoplasia cell models. The Ru(II)- and Os(II)-based complexes had the best IC50 values. The isoxazole-containing compounds outperformed the triazole-containing ones in terms of their cytostatic properties with submicromolar IC50 values. A subset of the complexes with Ru(II) and Ir(III) ions had bacteriostatic properties with low micromolar MIC values.