A novel group of alkaline earth metal amides: syntheses and characterization of M[N(2,6-(i)Pr(2)C(6)H(3))(SiMe(3))](2)(THF)(2) (M = Mg,Ca, Sr,Ba) and the linear,two-coordinate Mg[N(2,6-(i)Pr(2)C(6)H(3))(SiMe(3))](2)

Novel alkaline earth metal aryl-substituted silylamides were prepared using alkane (Mg) and salt elimination reactions (Mg, Ca, Sr, and Ba). The salt elimination regime involved the treatment of the alkaline earth metal iodides with 2 equiv of the respective potassium amide KNDiip(SiMe(3)), (Diip = 2,6-i-Pr(2)C(6)H(3)). The organomagnesium source for the alkane elimination was ((n)()Bu/(s)()Bu)(2)Mg. All compounds were characterized using (1)H, (13)C NMR, and IR spectroscopy, in addition to X-ray crystallography (except Mg[NDiip(SiMe(3))](2)THF(2)). Crystal data with Mo Kalpha (lambda = 0.710 73 A) are as follows: Mg[NDiip(SiMe(3))](2), 1, a = 9.4687(6) A, b = 9.6818(6) A, c = 17.9296(1) A, alpha = 96.487(1) degrees, beta = 94.537(1) degrees, gamma = 89.222(1) degrees, V = 1608.8(2) A(3), Z = 2 (two independent molecules), triclinic, space group P(-)1, R1 (all data) = 0.0508; (n)()BuMg[NDiip(SiMe(3))]THF(2), 2, a = 9.5413(1) A, b = 16.493(2) A, c = 9.8218(1) A, beta = 108.149(2) degrees, V = 1468.7(4) A(3), Z = 2, monoclinic, space group P2(1), R1(all data) = 0.1232; Ca[NDiip(SiMe(3))](2)THF(2), 4, a = 9.7074(1) A, b = 20.9466(4) A, c = 21.6242(3) A, alpha = 73.573(1) degrees, beta = 78.632(1) degrees, gamma = 89.621(1) degrees, V = 4129.1(1) A(3), Z = 4 (two independent molecules), triclinic, space group P(-)1, R1 (all data) = 0.0902; Sr[NDiip(SiMe(3))](2)THF(2), 5, a = 20.5874(5) A, b = 9.8785(2) A, c = 20.8522(5) A, beta = 102.035(2) degrees, V = 4147.6(2) A(3), Z = 4 (two independent molecules), monoclinic, space group P2/n, R1 (all data) = 0.0756; Ba[NDiip(SiMe(3))](2)THF(2), 6, a = 20.5476(2) A, b = 10.0353(2) A, c = 20.9020(4) A, beta = 101.657(1) degrees, V = 4221.0(1) A(3), Z = 4 (two independent molecules), monoclinic, space group P2/n, R1 (all data) = 0.0573.     

Copolymeric (lR-trans)-N,N'-1,2-cyclohexylene-bisbenzamide oligodimethylsiloxane chiral stationary phase for gas chromatography

A copolymeric stationary phase, consisting of a chiral selective part, i.e. (1R-trans)-N,N'-1,2-cyclohexylenebisbenzamide, and an efficient siloxane oligomeric part, was successfully applied to open tubular column GC analysis. The efficiency and the chiral selectivity of this stationary phase were studied in detail, and high capacity and efficiency at elevated GC temperatures were especially noted. Several drugs and other enantiomeric pairs were separated. The shown examples demonstrate a broad application range for this type of chiral stationary phase in GC analysis.     

Li2Br(NH2): Das erste ternäre Alkalimetallamidhalogenid

Li₂Br(NH₂): The First Ternary Alkali Metal Amide Halide The pseudobinary system LiNH₂/LiBr was investigated by X-ray methods. The crystal structure of the compound Li₂Br(NH₂) was solved by single crystal data: Li₂Br(NH₂): Pnma, Z = 8, a = 12.484(2) Å, b = 7.959(1) Å, c = 6.385(1) Å, Z(F_o) with (F_o)² ≧ 3σ(F_o)² = 348, Z (parameter) = 51, R/R_w = 0.019/0.021 Li₂Br(NH₂) crystallizes in a new type of structure. To one another isolated chains of [Li₂Li_4/2(NH₂)₂²⁺] show the motif of closest rod packing. They are connected via bromide ions in a distorted cubic primitive arrangement.     

Formation of internally nanostructured triblock copolymer particles

Particles with an internal structure have been found in dilute water solutions of a triblock copolymer of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO), which has short hydrophilic PEO endblocks compared to the central hydrophobic PPO block (EO5PO68EO5, L121). The properties of the block copolymer particles (i.e., their structure, size, and time stability) have been investigated using cryogenic transmission electron microscopy (cryo-TEM) in combination with dynamic light scattering (DLS) and turbidity measurements. The particles were formed in dilute solutions by quenching the temperature to temperatures where the reversed hexagonal phase is in equilibrium with a solution of unaggregated L121 copolymers (L1). From the DLS measurements, a mean hydrodynamic radius of 158 nm was extracted. The time-scan turbidity measurements were found to be unchanged for about 46 h. At higher copolymer concentrations, a reversed hexagonal phase (H2) exists in the L121/water system. SAXS was used to investigate the internal structure of the dispersed L121-based particles containing 15 wt % L121. It was found that the internal structure transforms from H2 to an inverse micellar system (L2) as the temperature increases from 37 to 70 degrees C.     

meso-substituted aromatic 34pi core-modified octaphyrins: syntheses,characterization and anion binding properties

Modified octaphyrins with 34pi electrons have been synthesized and characterized following a simple synthetic methodology. An acid-catalyzed alpha,alpha coupling of tetrapyrranes containing furan, thiophene and selenophene rings resulted in the formation of the respective octaphyrins in relatively good yield. Solution studies by (1)H NMR and 2D NMR methods and single crystal Xray structural characterization reveal an almost flat structure with two heterocyclic rings inverted. Specifically, in 14 two selenophene rings (one on each biselenophene unit) are inverted while in 15 two furan rings (one on each bifuran unit) are inverted when the meso substituent are mesityl groups. On changing the mesityl substituent to m-xylyl group as in 19, the location of ring inversion shifts to pyrrole rings (one on each bipyrrole unit) indicating the dependence of structure on the meso substituents. UV/Vis studies, both in freebase and protonated forms reveal typical porphyrinic character and the aromatic nature of the octaphyrins. The Deltadelta values evaluated by (1)H NMR spectroscopy also support their aromatic nature. The protonated forms of octaphyrins bind TFA anion in a 1:2 ratio. The TFA anions are located one above and below the plane of the octaphyrin macrocycle and they are held by weak electrostatic NH-O interactions similar to that observed for protonated rubyrins. However, in the present case, there is an additional non-electrostatic CH-O interaction involving beta-CH of the inverted heterocyclic ring and the carbonyl oxygen of the TFA. Furthermore, inter molecular interactions between the Cbond;H of the meso-mesityl group and the fluorine of CF(3) group of bound TFA leads to the formation of one-dimensional supramolecular arrays with interplanar distance of 13 A between two octaphyrins.     

Synthesis of stable and cell-type selective analogues of cyclic ADP-ribose, a Ca(2+)-mobilizing second messenger. Structure--activity relationship of the N1-ribose moiety

We previously developed cyclic ADP-carbocyclic ribose (cADPcR, 2) as a stable mimic of cyclic ADP-ribose (cADPR, 1), a Ca(2+)-mobilizing second messenger. A series of the N1-ribose modified cADPcR analogues, designed as novel stable mimics of cADPR, which were the 2"-deoxy analogue 3, the 3"-deoxy analogue 4, the 3"-deoxy-2"-O-(methoxymethyl) analogue 5, the 3"-O-methyl analogue 6, the 2",3"-dideoxy analogue 7, and the 2",3"-dideoxydidehydro analogue 8, were successfully synthesized using the key intramolecular condensation reaction with phenylthiophosphate-type substrates. We investigated the conformations of these analogues and of cADPR and found that steric repulsion between both the adenine and N9-ribose moieties and between the adenine and N1-ribose moieties was a determinant of the conformation. The Ca(2+)-mobilizing effects were evaluated systematically using three different biological systems, i.e., sea urchin eggs, NG108-15 neuronal cells, and Jurkat T-lymphocytes. The relative potency of Ca(2+)-mobilization by these cADPR analogues varies depending on the cell-type used: e.g., 3"-deoxy-cADPcR (4) > cADPcR (2) > cADPR (1) in sea urchin eggs; cADPR (1) > cADPcR (2) approximately 3"-deoxy-cADPcR (4) in T-cells; and cADPcR (2) > cADPR (1) > 3"-deoxy-cADPcR (4) in neuronal cells, respectively. These indicated that the target proteins and/or the mechanism of action of cADPR in sea urchin eggs, T-cells, and neuronal cells are different. Thus, this study represents an entry to cell-type selective cADPR analogues, which can be used as biological tools and/or novel drug leads.     

Synthesis and Reactivity of Stannyloligosilanes IV [1]: From Hydrido Substituted Stannasilanes Towards Stannasiloxanes

Summary.  Hydrido substituted stannasilanes of the type or (Z = H, Me, Ph; R, R′ = alkyl, Ph) are accessible by reaction of either alkali metal stannides (MSn(Z)R ₂; M = Li, Na) with halogen substituted silanes (; X = F, Cl) or chlorostannanes (R ₂SnCl₂, Ph₃SnCl) and fluorosilanes in the presence of magnesium. Stannasilanes with halogen substituents at the silicon as well as the tin atom are formed by treatment of the hydrido substituted stannasilanes with CHCl₃ or CCl₄. The hydrido substituted stannasilanes decompose in contact with air to distannanes and siloxanes or to the linear ( ^t Bu₂Sn(–O– ^t Bu₂Si–OH)₂) and cyclic ((– ^t Bu₂Sn–O– ⁱ Pr₂Si–O–)₂) stannasiloxanes. Received November 29, 2001. Accepted (revised) January 16, 2002     

Ultraviolet B Wavelength Dependence for the Regulation of Two Major Matrix-Metalloproteinases and Their Inhibitor TIMP-1 in Human Dermal Fibroblasts

Abstract— The wavelength dependence for the regulation of two major matrix-metalloproteinases, interstitial collagenase (MMP-1) and stromelysin-1 (MMP-3), and their major inhibitor, tissue inhibitor of metalloproteinases (TIMP-1), was studied in human dermal fibroblasts in vitro. Monochromatic irradiation at 302, 307, 312 and 317 nm with intensities ranging from 20 to 300 J/m² increased MMP-1 and MMP-3 mRNA steady-state levels and the secretion of the corresponding proteins up to 4.4-fold, whereas almost no increase was observed at wavelengths <290 nm. In contrast, the synthesis of TIMP-1 increased only marginally. This unbalance may contribute to the severe connective tissue damage related to photoaging of the skin. The wavelengths responsible for MMP-1 and MMP-3 induction reported here are distinct from the absorption spectrum of DNA and are different from results previously reported in the literature. Importantly, they overlap with wavelengths whose intensity is predicted to increase on the earth's surface upon ozone depletion. Intensities and particular wavelengths used in our studies in vitro can be absorbed readily by fibroblasts within the skin in vivo and, thus, are relevant for risk assessment and development of protective agents.     

Electrochemical solid-phase microextraction of anions and cations using polypyrrole coatings and an integrated three-electrode device

A method for the extraction, transfer and desorption of anions and cations under controlled potential conditions employing a new integrated three-electrode device is described. The device, containing working, reference and counter electrodes, was prepared from tubes that could be moved vertically with respect to each other. In this way, a small amount of solvent, held by capillary force, remained between the electrodes when the device was lifted out of a solution after an extraction. This design allowed the potential control to be maintained at all times. With the new integrated device, it was possible to perform potential controlled desorption into vials containing as little as 200 microl of solution. The required ion exchange capacity was obtained by electrodeposition of a polypyrrole coating on the surface of the glassy carbon working electrode. Solid-phase microextractions of several cations or anions were performed simultaneously under potentiostatic control by doping the polypyrrole coating with different anions such as perchlorate and p-toluenesulfonate. The efficiency of the extractions, which could be altered by varying the potential of the working electrode, could be increased by 150 to 200% compared to extractions using normal solid-phase microextraction conditions under open circuit conditions. A constant potential of +1.0 V and -0.5 V with respect to the silver pseudo reference electrode, was found to be well-suited for the extraction of samples containing ppm concentrations of anions (chloride, nitrite, bromide, nitrate, sulfate and phosphate) and cations (cadmium, cobalt and zinc), respectively.