An unusual ruthenium(ii) complex frozen at an intermediate point of hydride transfer between boron and ruthenium centres is reported.

No abstract

Microtubules (mt) are highly dynamic polymers composed of alpha-and beta-tubulin monomers that are present in all dividing and non-dividing cells. A broad variety of natural products exists that are known to interfere with the microtubule network, by either stabilizing or de-stabilizing these rope-like polymers. Among those tubulysins represent a new and potent class of cytostatic tetrapeptides originating from myxobacteria. Early studies suggested that tubulysins interact with the eukaryotic cytoskeleton by inhibition of tubulin polymerization with EC 50 values in the picomolar range. Recently, pretubulysins have been described to retain the high tubulindegradation activity of their more complex tubulysin relatives and represent an easier synthetic target with an efficient synthesis already in place. Although tubulin has been suggested as the dedicated target of tubulysin a comprehensive molecular target analysis of pretubulysin in the context of the whole proteome has not been carried out so far. Here we utilize synthetic chemistry to develop two pretubulysin photoaffinity probes which were applied in cellular activity-based protein profiling and imaging studies in order to unravel and visualize dedicated targets. Our results clearly show a remarkable selectivity of pretubulysin for beta-tubulin which we independently confirmed by a mass-spectrometry based proteomic profiling platform as well as by tubulin antibody based co-staining on intact cells.

Nitrogen-containing heterocycles have found remarkable applications in natural product research, material sciences, and pharmaceuticals. Although the synthesis of this interesting class of compounds attracted the interest of generations of organic chemists, simple and straightforward assembly methods based on transition-metal catalysis have regularly been elusive. The recent advancements in the development of C-H functionalization have helped in accomplishing the synthesis of a variety of complex heterocycles from simple precursors. This Focus Review summarizes the recent advances in one particular field: the copper-catalyzed C-N bond formation reactions via C-H bond functionalization to furnish a comprehensive range of nitrogen heterocycles. Applicability and synthetic feasibility of a particular reaction represent major requirements for the inclusion in this review.