On the viability of 5-endo-dig cyclisations of O-propargylic hydroxylamine derivatives, leading to 2,5-dihydroisoxazoles (3-isoxazolines)

O-Propargylic hydroxylamines undergo smooth 5-endo-dig cyclisations upon exposure to 3 equiv of molecular iodine to give respectable yields of the corresponding 4-iodo-2,5-dihydroisoxazoles, which should find a number of applications as intermediates for syntheses amongst this useful class of heterocycles.     

Differentiation of opium and poppy straw using capillary electrophoresis and pattern recognition techniques

Opium samples from four different locations and poppy straw from different plant varieties have been assayed using micellar capillary electrophoresis incorporating a sweeping technique. Individual alkaloids (morphine, codeine, papaverine, noscapine, thebaine, oripavine, reticuline and narceine) were quantitatively determined in the different samples by a validated capillary electrophoresis method. Unsupervised pattern recognition of the opium samples and the poppy straw samples using hierarchical cluster analysis (HCA) and principal component analysis (PCA), showed distinct clusters. Supervised pattern recognition using soft independent modelling of class analogy (SIMCA) was performed to show individual groupings and allow unknown samples to be classified according to the models built using the CZE assay results.     

Cavity ring-down spectroscopy of the torsional motions of 1,4-bis(phenylethynyl)benzene

The torsional motions of jet-cooled 1,4-bis(phenylethynyl)benzene (BPEB), a prototype molecular wire, were studied using cavity ring-down spectroscopy in the first UV absorption band (316-321 nm). The torsional spectrum of 1,4-bis(phenylethynyl)-2,3,5,6-tetradeuteriobenzene was also recorded in the gas phase. Both spectra were successfully simulated using simple cosine potentials to describe the torsional motions. The ground-state barrier to rotation was estimated to be 220-235 cm(-1), which is similar to that of diphenylacetylene (tolane). Complementary DFT calculations were found to overestimate the torsional barrier.     

An HPLC assay for the determination of ketoconazole in common pharmaceutical preparations

An HPLC method is described using octadecylsilica (3 microns) with an acetonitrile phosphate buffer mobile phase containing diethylamine which is capable of separating ketoconazole [(+/-)-cis-1-acetyl-4-(4[2-(dichlorophenyl)-2- (1H-imidazol-1-ylmethyl)-1,3-dioxolan-4-yl]methoxy]phenyl)pi perazine] from four related compounds, (R049223, R063600, R053165 and R039519) and from excipients in tablets, cream and shampoo. The method was validated using an external calibration method for tablets, shampoo and creams and a standard addition method for cream. The limits of detection for the related compounds in the presence of ketoconazole are also reported.     

Synthetic erythropoietic proteins: tuning biological performance by site-specific polymer attachment

Chemical synthesis in combination with precision polymer modification allows the systematic exploration of the effect of protein properties, such as charge and hydrodynamic radius, on potency using defined, homogeneous conjugates. A series of polymer-modified synthetic erythropoiesis proteins were constructed that had a polypeptide chain similar to the amino acid sequence of human erythropoietin but differed significantly in the number and type of attached polymers. The analogs differed in charge from +5 to -26 at neutral pH and varied in molecular weight from 30 to 54 kDa. All were active in an in vitro cell proliferation assay. However, in vivo potency was found to be strongly dependent on overall charge and size. The trends observed in this study may serve as starting points for the construction of more potent synthetic EPO analogs in the future.     

Mixed-metal cluster chemistry. 28. Core enlargement of tungsten-iridium clusters with alkynyl, ethyndiyl, and butadiyndiyl reagents

Reaction of [WIr3(mu-CO)3(CO)8(eta-C5Me5)] (1c) with [W(C[triple bond]CPh)(CO)3(eta-C5H5)] afforded the edge-bridged tetrahedral cluster [W2Ir3(mu4-eta2-C2Ph)(mu-CO)(CO)9(eta-C5H5)(eta-C5Me5)] (3) and the edge-bridged trigonal-bipyramidal cluster [W3Ir3(mu4-eta2-C2Ph)(mu-eta2-C=CHPh)(Cl)(CO)8(eta-C5Me5)(eta-C5H5)2] (4) in poor to fair yield. Cluster 3 forms by insertion of [W(C[triple bond]CPh)(CO)3(eta-C5H5)] into Ir-Ir and W-Ir bonds, accompanied by a change in coordination mode from a terminally bonded alkynyl to a mu4-eta2 alkynyl ligand. Cluster 4 contains an alkynyl ligand interacting with two iridium atoms and two tungsten atoms in a mu4-eta2 fashion, as well as a vinylidene ligand bridging a W-W bond. Reaction of [WIr3(CO)11(eta-C5H5)] (1a) or 1c with [(eta-C5H5)(CO)2 Ru(C[triple bond]C)Ru(CO)2(eta-C5H5)] afforded [Ru2WIr3(mu5-eta2-C2)(mu-CO)3(CO)7(eta-C5H5)2(eta-C5R5)] [R = H (5a), Me (5c)] in low yield, a structural study of 5a revealing a WIr3 butterfly core capped and spiked by Ru atoms; the diruthenium ethyndiyl precursor has undergone Ru-C scission, with insertion of the C2 unit into a W-Ir bond of the cluster precursor. Reaction of [W2Ir2(CO)10(eta-C5H5)2] with the diruthenium ethyndiyl reagent gave [RuW2Ir2{mu4-eta2-(C2C[triple bond]C)Ru(CO)2(eta-C5H5)}(mu-CO)2(CO)6(eta-C5H5)3] (6) in low yield, a structural study of 6 revealing a butterfly W2Ir2 unit capped by a Ru(eta-C5H5) group resulting from Ru-C scission; the terminal C2 of a new ruthenium-bound butadiyndiyl ligand has been inserted into the W-Ir bond. Reaction between 1a, [WIr3(CO)11(eta-C5H4Me)] (1b), or 1c and [(eta-C5H5)(CO)3W(C[triple bond]CC[triple bond]C)W(CO)3(eta-C5H5)] afforded [W2Ir3{mu4-eta2-(C2C[triple bond]C)W(CO)3(eta-C5H5)}(mu-CO)2(CO)2(eta-C5H5)(eta-C5R5)] [R = H (7a), Me (7c); R5 = H4Me (7b)] in good yield, a structural study of 7c revealing it to be a metallaethynyl analogue of 3.     

4-Iodo-2-methyl-5-nitro­aniline exhibits neither strong hydrogen bonding nor intermolecular I⃛nitro interactions

In the title compound, C₇H₇IN₂O₂, the O atoms of the nitro group are disordered over two sets of sites and there is evidence that the intramolecular I⃛nitro interaction is repulsive. In the crystal structure, there are neither strong hydrogen bonds, nor intermolecular I⃛nitro interactions, nor aromatic π–π-stacking interactions.     

A numerical technique for laminar swirling flow at the interface between porous and homogenous fluid domains

There have been a few recent numerical implementations of the stress‐jump condition at the interface of conjugate flows, which couple the governing equations for flows in the porous and homogenous fluid domains. These previous demonstration cases were for two‐dimensional, planar flows with simple geometries, for example, flow over a porous layer or flow through a porous plug. The present study implements the interfacial stress‐jump condition for a non‐planar flow with three velocity components, which is more realistic in terms of practical flow applications. The steady, laminar, Newtonian flow in a stirred micro‐bioreactor with a porous scaffold inside was investigated. It is shown how to implement the interfacial jump condition on the radial, axial, and swirling velocity components. To avoid a full three‐dimensional simulation, the flow is assumed to be independent of the azimuthal direction, which makes it an axisymmetric flow with a swirling velocity. The present interface treatment is suitable for non‐flat surfaces, which is achieved by applying the finite volume method based on body‐fitted and multi‐block grids. The numerical simulations show that a vortex breakdown bubble, attached to the free surface, occurs above a certain Reynolds number. The presence of the porous scaffold delays the onset of vortex breakdown and confines it to a region above the scaffold. Copyright © 2008 John Wiley & Sons, Ltd.