Synthesis of the second generation photoaffinity probes of tautomycin

Molecular design, synthesis and biological evaluation of novel 1,2,5-trisubstituted benzimidazole derivatives as cytotoxic agents endowed with ABCB1 inhibitory action to overcome multidrug resistance in cancer cells

Multidrug resistance (MDR) is a leading cause for treatment failure in cancer patients. One of the reasons of MDR is drug efflux by ATP-binding cassette (ABC) transporters in eukaryotic cells especially ABCB1 (P-glycoprotein). In this study, certain novel 1,2,5-trisubstituted benzimidazole derivatives were designed utilising ligand based pharmacophore approach. The designed benzimidazoles were synthesised and evaluated for their cytotoxic activity towards doxorubicin-sensitive cell lines (CCRF/CEM and MCF7), as well as against doxorubicin-resistant cancer cells (CEM/ADR 5000 and Caco-2). In particular, compound VIII showed a substantial cytotoxic effect in all previously mentioned cell lines especially in doxorubicin-resistant CEM/ADR5000 cells (IC₅₀ = 8.13 µM). Furthermore, the most promising derivatives VII, VIII and XI were tested for their ABCB1 inhibitory action in the doxorubicin-resistant CEM/ADR 5000 subline which is known for overexpression of ABCB1 transporters. The results showed that compound VII exhibited the best ABCB1 inhibitory activity at three tested concentrations (22.02 µM (IC₅₀), 50 µM and 100 µM) in comparison to verapamil as a reference ABCB1 inhibitor. Such inhibition resulted in a synergistic effect and a massive decrease in the IC₅₀ of doxorubicin (34.5 µM) when compound VII was used in a non-toxic dose in combination with doxorubicin in doxorubicin-resistant cells CEM/ADR 5000 (IC_50(Dox+VII) = 3.81 µM). Molecular modelling studies were also carried out to explain the key interactions of the target benzimidazoles at the ABCB1 binding site. Overall the obtained results from this study suggest that 1,2,5-trisubstituted benzimidazoles possibly are promising candidates for further optimisation and development of potential anticancer agents with ABCB1 inhibitory activity and therefore overcome MDR in cancer cells.

Tautomycin's interactions with protein phosphatase 1

It has been a long journey since tautomycin (TTM) was isolated in 1987 and the discovery that it inhibited protein phosphatase 1 (PP1) more strongly than PP2A until finally the cocrystal structure of TTM and PP1 was presented early in 2009. The fact that TTM shows preference to inhibit PP1 over PP2A makes this compound unique among the known PP1 and PP2A inhibitors. A number of groups were involved in work aiming to unravel TTM's interactions with PP1 and by doing so hoping to disentangle the secrets as to why TTM is a better inhibitor of PP1 than PP2A. This Focus Review looks back at the work conducted with TTM in order to establish its point of interaction with PP1 prior to X-ray structure. Finally the conclusions before the X-ray structure are compared with the real situation.

Determination of solvent-trapped products obtained by photolysis of aryl azides in 2,2,2-trifluoroethanol

A series of nonfluorinated and fluorinated aryl azides with varied functionality patterns were irradiated in 2,2,2-trifluoroethanol with either a high-pressure or a low-pressure mercury lamp. Interestingly, one of the major products in these reactions was the result of the recombination of anilino and alkyl radicals to form the corresponding hemiaminal compounds. The structure of the recombination products was assigned unambiguously after proton/deuterium exchange experiments followed by MS and MS/MS analysis.