Remote asymmetric induction with vinylketene silyl n,o-acetal

A highly regio- and diastereoselective TiCl4-mediated vinylogous Mukaiyama aldol reaction using the chiral vinylketene silyl N,O-acetal has been developed. The present vinylogous Mukaiyama aldol reaction provides a unique and effective means of controlling remote asymmetric induction. The methyl group at the alpha-position is important in achieving a high level of stereoselectivity. From a synthetic point of view, this methodology can provide a one-step construction of delta-hydroxy-alpha,gamma-dimethyl-alpha,beta-unsaturated carbonyl unit that is seen in many natural polyketide products.     

First-Known High-Nuclearity Copper–Nickel Carbonyl Cluster: [CuxNi35−x(CO)40]5− (with x=3 or 5) Containing an Unprecedented 35-Atom Three-Layer hcp Triangular Stacking Metal-Core Geometry

Reactions of [Ni₆(CO)₁₂]^2- (1) with CuBr₂ have given rise in small yields (10%) to the first example of a close-packed copper-nickel carbonyl cluster; its formulation as [Cu_xNi_35-x(CO)₄₀]^5- (with x=3 or 5) is based upon a low-temperature CCD X-ray crystallographic determination coupled with an elemental analysis and X-ray fluorescence measurements. This air-unstable black pentaanion (2) together with one co-crystallized bromide anion, six [NMe₄]⁺ counterions, and one solvated acetone molecule comprise the crystallographic independent part in a monoclinic unit cell of P2₁/n symmetry (with Z=4). The geometrically unprecedented 35-atom hcp M(A)₂M(B)₃Ni₃₀ polyhedron of pseudo-D_3h symmetry consists of a central 15-atom equilateral ₄M(B)₃Ni₁₂ triangle that is capped on both sides by two symmetry-related 10-atom equilateral ₃M(A)Ni₉ triangles. The 35-atom M(A)₂M(B)₃Ni₃₀ core is encapsulated by 40 COs, whose connectivities, due to an extra CO ligand on one of the three triangular sides, reduce the pseudo D_3h symmetry of the metal core to C_s. An elemental analysis via AA and X-ray fluorescence measurements resulted in Cu/Ni ratios of 3.2/31.8 and 3.7/31.3, respectively, that are consistent with the metal core being either Cu₅Ni₃₀ (i.e., M(A)=M(B)=Cu) or Cu₃Ni₃₂ (i.e., M(A)=Ni; M(B)=Cu). Several attempts to determine the actual stoichiometry of the metal core by use of electrospray FT/MS/ICR measurements were unsuccessful. The maximum metal-core diameter of 2 is ca. 0.41 nm parallel and 0.85 nm perpendicular to the principal 3-fold axis.     

On a p-Local Geometry Associated with a Complex of Non-Trivial p-Subgroups

Let D be a complex of non-trivial p-subgroups of a finite groupG, closed under G-conjugation. In this paper, a p-local geometry^p(G; D) is introduced for G associated with the complex D. Thehomotopy equivalence between ^p(G; D) and D is also studied.2000 Mathematics Subject Classification 20E15, 51E24.     

Nanosecond Time-Gated Spectroscopy of Laser-Ablation Plume of Human Hair to Detect Calcium for Potential Diagnoses

We demonstrate the nanosecond time-gated spectroscopy of plume luminescence in UV laser ablation of human hair. Clear and sharp peaks of calcium ion (Ca⁺) appear in the spectrum although the Ca content is only 0.1% in human hair. Highly sensitive detection of Ca is thus possible. In the experiment, the peak intensity of Ca⁺ was measured for human hair samples of female subjects over a wide range of age, and compared to the bone mineral density of the lumbar vertebrae of the subjects themselves. Our experimental results suggest that this specific spectroscopy has the potential for novel diagnoses including monitoring of daily Ca intake and a screening diagnosis of osteoporosis. The spectroscopic system and time transition of plume-luminescence spectra are also described.