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Heterogeneous copper catalysts were prepared by the deposition of CuI on a hybrid material consisting of silica and a polymer with imidazolium moieties.The solid materials were characterised using solid-phase NMR, Fourier transform infrared, Raman and X-ray photoelectron spectroscopies and Brunauer-Emmett-Teller measurements. The formation of copper-carbene complexes was proved from Raman spectra and the results were supported by density functional theory calculations. The catalyst could be recycled efficiently with low loss of copper. Metal leaching was proved to be facilitated by the use of conditions typical for a homogeneous system (the presence of a polar solvent or the addition of a tertiary amine). Besides simple model reactions, the best catalyst was found to be suitable for the synthesis of triazoles of more elaborate structure, such as ferrocene or steroid derivatives.

The potential inhibitory effect of diverse triazolyl-ferrocene steroids on key enzymes of the estrogen biosynthesis was investigated. Test compounds were synthesized via copper-catalyzed cycloaddition of steroidal azides and ferrocenyl-alkynes using our efficient methodology published previously. Inhibition of human aromatase, steroid sulfatase (STS) and 17β-hydroxysteroid dehydrogenase type 1 (17β-HSD1) activities was investigated with in vitro radiosubstrate incubations. Some of the test compounds were found to be potent inhibitors of the STS. A compound bearing ferrocenyl side chain on the C-2 displayed a reversible inhibition, whereas C-16 and C-17 derivatives displayed competitive irreversible binding mechanism toward the enzyme. 17α-Triazolyl-ferrocene derivatives of 17β-estradiol exerted outstanding inhibitory effect and experiments demonstrated a key role of the ferrocenyl moiety in the enhanced binding affinity. Submicromolar IC50 and Ki parameters enroll these compounds to the group of the most effective STS inhibitors published so far. STS inhibitory potential of the steroidal ferrocenes may lead to the development of novel compounds able to suppress in situ biosynthesis of 17β-estradiol in target tissues.

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