An efficient protocol for stereoselective synthesis of densely functionalized pyrrolidines by a [3 + 2]-annulation of N-Ts-alpha-amino aldehydes and 1,3-bis(silyl)propenes is described.
Three situations are observed when the new
cobaltocene derivative
Co(C5H4BPri
2)2
(2) is oxidized.
The cobaltocenium salt [2]PF6
(3) is obtained with
[FeCp2]PF6 as oxidant. With
Cu(OH)2 the inverse chelate [2]OH (4) with a μ-OH group bridging
the two boron
centers is formed. Oxidation with
C2Cl6 gives a zwitterionic chloride (5) with a trigonal and a
quaternized
boron center; in solution 5 is fluxional.
The surface shear viscosity of a myelin mimetic Langmuir monolayer is investigated upon adsorption of myelin basic protein (MBP). We measure an increase of the surface shear viscosity at picomolar concentrations of the protein, suggesting that the globular conformation of MBP changes upon adsorption at the monolayer. The conformational change enables hydrodynamic interactions of the proteins, with a typical separation of hundreds of nanometers. This unfolding is essential for the compactification of the myelin sheath, serving an enhanced saltatory signal transduction in vertebrates. The viscometry used extends the sensitivity of standard surface viscometers toward lower viscosities.
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