5,7-Dimethoxy-2-phenyl-4H-chromen-4-one

The asymmetric unit of the title compound, C17H14O4, contains two independent molecules which differ in the relative orientations of the phenyl rings with repect to the essentially planar [maximum deviations of 0.029 (2) and 0.050 (2) angstrom in the two molecules] chromene fused-ring system, forming dihedral angles of 10.3 (5) and 30.86 (5)degrees in the two molecules. The crystal structure is stabilized by weak C-H center dot center dot center dot O and C-H center dot center dot center dot pi interactions, and pi-pi stacking interactions.

Chlorinated Hypoelectronic Dimetallaborane Clusters: Synthesis, Characterization, and Electronic Structures of (eta(5)-C5Me5W)(2)B5HnClm (n=7, m=2 and n=8, m=1)

Pyrolysis of (eta(5)-C5Me5WH3)B4H8, 1, in the presence of excess BHCl2 center dot SMe2 in toluene at 100 degrees C led to the isolation of (eta(5)-C5Me5W)(2)B5H9, 2, and B-Cl inserted (eta(5)-C5Me5W)(2)B5H8Cl, 3, and (eta(5)-C5Me5W)(2)B5H7Cl2, (four isomers). All the Chlorinated tungstaboranes were isolated as red and air and moisture sensitive solids. These new compounds have been characterized in solution by H-1, B-11, C-13 NMR, and the structural types were unequivocally established by crystallographic analysis of compounds 3, 4, and 7. Density functional theory (DFT) calculations were carded out on the model molecules of 3-7 to elucidate the actual electronic structures of these chlorinated species. On grounds of DFT calculations we demonstrated the role of transition metals, bridging hydrogens, and the effect of electrophilic substitution of hydrogens at B-H vertices of metallaborane structures.

Structure of pentacyclo[7.4.2.02,6.06,15.011,14]pentadec-4-ene-7,13-dione, a novel pentacyclic C15 quinane system

C 15H 1602 (a synthetic precursor to dodecahedrane), monoclinic, P21/n, a = 12.171 (5), b = 6.976(5), c = 13.868 (3) A, B = 102.56 (3) ° , Z = 4, D m = 1.30, D c = 1.318 g cm -3, F(000) = 488, g(Mo K¢t) = 0.92 cm- 1. Intensity data were collected on a Nonius CAD-4 diffractometer and the structure was solved by direct methods. Full-matrix least-squares refinement gave R = 0.077 (R w = 0.076) for 1337 observed reflections. All the five-membered rings are cis fused and have envelope (C s symmetry) conformations.

Editorial of "International Journal of Critical Indigenous Studies, Volume 7, Number 2, 2014"

This edition scales the merlons and embrasures that mark the epistemological barriers that contemporary colonising power continually puts in place. Each article harnesses a critical Indigenous perspective in order to challenge conservative approaches or positions, be they concerned with reconciliation, Indigenous-led research, research tools or the nature of Aboriginal being. The first article, by Barry Judd and Emma Barrow, examines reconciliation discourse within the higher education sector and highlights the ways a normative Anglo-Australian identity militates against genuine ‘whitefella’ attempts to ‘reconcile’. The authors stress the importance of inclusive, institutional practice that serves to decentre Anglo-centrism and which, in turn, brings Indigenous peoples more fully into the fold of Australian university life.

A combined extended and helical backbone for Boc-(Ala-Leu-Ac(7)c-)(2)-OMe

The structure of the peptide Boc-Ala-Leu-Ac(7)c-Ala-Leu-Ac(7)c-OMe (Ac(7)c,1-aminocycloheptane-1-carboxylic acid) is described in crystals. The presence of two Ac(7)c residues was expected to stabilize a 3(10)-helical fold. Contrary to expectation the structural analysis revealed an unfolded amino terminus, with Ala(1) adopting an extended beta-conformation (phi = -93degrees,psi = 112degrees). Residues 2-5 form a 3(10)-helix, stabilized by three successive intramolecular hydrogen bonds. Notably, two NH groups Ala(1) and Ac(7)c(3) do not form any hydrogen bonds in the crystal. Peptide assembly appears to be dominated by packing of the cycloheptane rings that stack against one another within the molecule and also throughout the crystal in columns.

N-(7-Nitrobenz-2-oxa-1,3-diazol-4-yI)colcemid, a probe for different classes of colchincine-binding site on tubulin

The nature of binding of 7-nitrobenz-2-oxa-1,3-diazol-4-yl-colcemid (NBD-colcemid), an environment-sensitive fluorescent analogue of colchicine, to tubulin was tested. This article reports the first fluorometric study where two types of binding site of colchincine analogue on tubulin were detected. Binding of NBD-colcemid to one of these sites equilibrates slsowly. NBD-colcemid competes with colchicine for this site. Binding of NBD-colcemid to this site also causes inhibition of tubulin self-assembly. In contrast, NBD-colcemid binding to the other site is characterised by rapid equilibration and lack of competition with colchicine. Nevertheless, binding to this site is highly specific for the cholchicine nucleus, as alkyl-NBD analogues have no significant binding activity. Fast-reaction-kinetic studies gave 1.76 × 105 M–1 s–1 for the association and 0.79 s–1 for the dissociation rate constants for the binding of NBD-colcemid to the fast site of tubulin. The association rate constants for the two phases of the slow site are 0.016 × 10–4 M–1 s–1 and 3.5 × 10–4 M–1 respectively. These two sites may be related to the two sites of colchicine reported earlier, with binding characteristics altered by the increased hydrophobic nature of NBD-colcemid.

4-Azidomethyl-7-methyl-2-oxo-2H-chromene-6-sulfonyl azide

In the title compound, C11H8N6O4S, the plane of the coumarin aromatic ring is twisted by 17.2 (2)degrees with respect to the plane of the azide group bound to the methylene substituent, whereas it is twisted by 83.2 (2)degrees to the plane of the azide attached to the sulfonyl group. The crystal structure is stabilized by weak C-H center dot center dot center dot O interactions, leading to the formation of dimers with R-2(2)(12) graph-set motifs. These dimers are further linked by weak S-O center dot center dot center dot pi and pi-pi contacts centroid-centroid distance = 3.765 (2) angstrom], leading to the formation of a layered structure.

Synthesis of 5,5-Dimethyl-7-methoxy 4-oxatricyclo [4,3,1,03,7]decan-2-ones

Two new synthetic routes for the preparation of the title compound and its 3-substituted derivatives, a novel ring system present in morellin and other related natural products, are reported from the readily available dihydroanisoles.

A comparison of the DNMR behaviour of methyl 5,6-bis(2-methoxyphenyl)-1,4-dimethyl-7-oxobicyclo[2.2.1]hept-5-en-2-endo-carboxylate and its 7-oxa analogue

Methyl 5,6-Bis(2-methoxyphenyt)-1,4-dimethyl-7-oxobicyclo[2.2.1]hept-5-en-2-endo-carboxylate, a moderately crowded norbornenone ester, exhibits complex VT-DNMR behaviour. A similar behaviour is not seen in its 7-oxa analogue, showing that conformational transmission from position 7 has a crucial influence on the distance parameters that govern the dynamic processes involving the substituents on the bicycloheptene framework.

PICES Press, Vol. 7, No. 2, July 1999

Improving PICES CO2 measurement quality The status of the Bering Sea: July - December 1998 The state of the eastern North Pacific since October 1998 The state of the western North Pacific in the second half of 1998 Paul Henry LeBlond Report on the ICES/SCOR Symposium on Ecosystem Effects of Fishing What is the carrying capacity of the North Pacific Ocean for salmonids? Southeast Bering Sea Carrying Capacity (SEBSCC) The Whole Earth System: The role of regional programs Sub-Arctic Gyre Experiment in the North Pacific Ocean (SAGE) The Alaska Predator Ecosystem Experiment (APEX): An integrated seabird and forage fish investigation sponsored by the Exxon Valdez Oil Spill Trustee Council ICES and GOOS: A progress report Report on GOOS Living Marine Resource Panel Meeting

Laser action from 1,3,5,7-tetramethyl-2,6-diethyl-8-n-propyl pyrromethene-BF2

We measured spectroscopic and laser action properties of a novel 8-position substituted pyrromethene-BF2, namely 1,3,5,7-tetramethyl-2,6-diethyl-8-n-propyl pyrromethene-BF2 complex. The laser action was performed with the corresponding dye solution in ethanol, which was placed in a Littman-type laser cavity pumped by the second harmonic of a Q-switched Nd:YAG laser. The spectroscopic measurements clearly indicated that the corresponding dye solution in ethanol exhibited intense absorption in the visible spectral region with large fluorescence quantum yield. It possesses rather low triplet-triplet absorption in the spectral region 460-550 nm and almost negligible triplet-triplet absorption in the lasing spectral region. As a consequence, it lases nearly as efficiently as commercially available benchmark laser dyes such as Rhodamine-6G and outperformed them in wavelength tunability in our laser cavity and pump geometry. (C) 2002 Optical Society of America.