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The human P2X7 receptor (hP2X7R) is an ATP-gated nonspecific cation channel. It is expressed in cells of the immune system. Via this receptor, ATP, released during cell damage or hypoxia, serves as danger associated molecular pattern to induce inflammatory reactions. In comparison to other P2X receptors, P2X7R-dependent ionic currents differ in their activation kinetics by an absence of desensitization and induction of large membrane pores by long lasting agonist applications, i.e. the gating and permeation mechanisms of P2X7 receptors are not fully understood.G338 within the second transmembrane domain (TM2) is part of the narrow ion channel pore domain. Substitution of G338 to cysteine reversed the gating behaviour of the hP2X7R channel, i.e. hP2X7G338C expressing Xenopus oocytes displayed a leak conductance which is decreased by application of ATP or by the P2X7R agonist, BzATP. Substitution of extracellular Na+ by the larger organic Tris+ significantly decreased the ion conductance and shifted the reversal potential of the ATP-induced current to more negative potentials indicating that the leak current was carried by cations.Modeling the structural changes of hP2X7G338C during ATP application with the recently published truncated zebrafish P2X4 receptor model as template we found that G338 is located at the narrowest part of the closed ion channel pore and substitution by cysteine pushes the TM2 of the three subunits apart leading to an incomplete channel closure. ATP application leads to a conformation switch of hP2X7G338C which allows an interaction of C338 with Y40 and Y343 decreasing the ion channel pore diameter and leading to a reduced ion current.These findings point to a critical role of G338 in gating the P2X7 receptor.This work was supported by the German research foundation (DFG, Ma 1581/15-1, Schm 536/9-1

The synthesis of new chiral salenophos-type ligands bearing `hard' and `soft' coordination sites is described. The polyfunctionalised ligands are used for the construction of monometallic and early–late heterobimetallic complexes. In the reaction with titanium(IV) reagents the salen subunit selectively coordinated to the `hard' metal. The phosphine groups in turn can be coordinated to rhodium(I). The coordination geometry of the diphosphine–Rh subunit is strongly influenced by the counter ligands COD or CO and Cl, respectively. In the asymmetric hydroformylation of vinyl acetate with one of the Rh–Ti-complexes, the branched aldehyde is predominantly formed with 30% ee.

A comparative study on the reaction of (CO)3Mo(CH3CN)3 with a series of homologous chiral and prochiral trisphosphines is presented. Only one of the tripodal ligands formed the desired unique complex (CO)3Mo(η3-triphos) (3b) being the first example of a Mo(0)-complex containing a seven- as well as an eight-membered chelate ring. Spectroscopic properties of this complex and two different η2-coordinated species are discussed. The molecular structure of the η3-coordinated complex 3b has been determined by X-ray crystallography.

The synthesis of the chiral polyfunctional diphosphine salenophos 1 is described. The new ligand bearing hard and soft coordination sites chelates titanium(IV) as well as palladium(II) in a defined manner provided a certain order during the introduction of the two metals was kept. In this way the first chiral early-late heterobimetallic complex could be synthesized. It was fully characterized by NMR spectroscopy and X-ray structural analysis. Remarkable features of the heterobimetallic complex are the trans coordination of the phosphine groups on palladium and the distance between Ti and Pd which is more than 4.13 A.

Chiral phosphinephosphites were prepared by the reaction of enantiomerically pure cis - or trans -3-diphenylphosphinotetrahydrofuran-4-ol with atropisomeric chlorophosphites. These ligands were tested in the rhodium catalyzed hydroformylation of allyl acetate. Selectivities up to 44% ee were observed in dependence on the configuration of the applied phosphinephosphites and the bulk of the aromatic groups bound to the phosphorus. The results clearly show that both, central and axial chirality are responsible for the stereochemical outcome of this reaction.

The synthesis of chiral bisphosphines bearing a hydroxyl group in a rigid backbone is described. These compounds which are analogues of the prominent ligand DIOP formed definite rhodium complexes. IR spectra provided evidence that the hydroxyl groups do not participate in the complexation to the metal or to one of the acetal oxygen atoms. The complexes have proven successful in the asymmetric hydrogenation of prochiral functionalized olefins in different solvents. In methanol only small effects could be detected in comparison to parent complexes which do not carry a hydroxyl group. However, when hydrogenations were performed in methylene chloride or toluene significant differences in the enantioselectivities (by up to 17 %ee) were observed, especially in the reaction with itaconic acid or its dimethyl ester, respectively. In the latter cases the effect is contingent on the spatial orientation of the hydroxyl group in the catalyst.

The complexation behaviour of cis- und trans-3-diphenylphosphino-4-hydroxyl-tetrahydrofurans with [Rh(COD)2]BF4 is studied with the help of NMR and IR spectroscopy. In dependence of the spatial arrangement of hydroxyl and phosphino group the formation of different intra- and intermolecular bridged O-P complexes has been observed.

The synthesis of (4R,5R)-4,5-bis(diphenylphosphinomethyl)-2-hydroxymethyl-2-phenyl-1,3-dioxolane 1 which is related to DIOP is described. The application of this new ligand in asymmetric catalysis is illustrated in the stereodifferentiating hydrogenation.

The synthesis of enantiomerically pure ( R,R )-N,N′-bis(3-diphenylphosphino-2-hydroxybenzylidene)-1,2-diphenyl-1,2-ethanediamine ( 1 ) is described. This multidentate salentype ligand offers several possibilities for the construction of chiral mono-nuclear or bi-nuclear metal complexes, which may be useful in bifunctional asymmetric catalysis.