Separation methods for captopril in pharmaceuticals and biological fluids

Captopril (CAP) is an orally active angiotensin-converting enzyme (ACE) inhibitor and has been widely used for management of hypertension and congestive heart failure. CAP lacks an aromatic chromophore required for facile direct UV detection and also has two chiral centers. These factors can render the determination of CAP in complex matrices challenging. This review covers more than 20 years of analytical research on this drug, focusing mainly on pharmaceutical and biological applications. The primary separation techniques discussed are gas chromatography, liquid chromatography, and capillary electrophoresis. The structures of the CAP derivatizing agents as well as a table summarizing various HPLC methods are provided. A discussion of key recent chromatographic and electrophoretic methods for other ACE inhibitors is also present.     

Interrupted Fischer Indolization Approach toward the Communesin Alkaloids and Perophoramidine

A concise approach toward the total synthesis of the communesin alkaloids and perophoramidine is reported. The strategy relies on the use of the interrupted Fischer indolization to build the tetracyclic indoline core of the natural products. Studies to probe the scope and limitations of this plan are presented. Although the methodology does not tolerate a C8-allyl substituent en route to the challenging vicinal quaternary stereocenters, variation at C7 and on the C ring is permitted.     

Chemiluminescence detection flow cells for flow injection analysis and high-performance liquid chromatography

We have examined a range of new and previously described flow cells for chemiluminescence detection. The reactions of acidic potassium permanganate with morphine and amoxicillin were used as model systems representing the many fast chemiluminescence reactions between oxidising agents and organic analytes, and the preliminary partial reduction of the reagent was exploited to further increase the rates of reaction. The comparison was then extended to high-performance liquid chromatography separations of α- and β-adrenergic agonists, with permanganate chemiluminescence detection. Flow cells constructed by machining novel channel designs into white polymer materials (sealed with transparent films or plates) have enabled improvements in mixing efficiency and overall transmission of light to the photodetector.     

Crystal Structures of a Series of 1,1-Spiro-bis(1,2,3,4-tetrahydronaphthalene)-Based Derivatives

Abstract  

The structures of four spirobisnaphthalenes based monomers 1, 2, 3a and 3b are reported. Each compound represents a methoxylated precursor which after deprotection led to the formation of a monomer successfully used for the synthesis of Polymers of intrinsic microporosity. The spiro-centre represents the site of contortion that, since its rigidity, leads to inefficient packing in the solid state inducing microporosity in the final polymer. Compound 1 crystallized in the monoclinic P2/c space group with unit cell parameters a = 8.1659(19) ?, b = 7.5298(18) ?, c = 19.130(5) ?, β = 97.935(4)°, V = 1165.0(5) ?³, Z = 2, D = 1.210 Mg m⁻³. Compound 2 crystallized in the monoclinic P2₁/n space group with unit cell parameters a = 12.6940(9) ?, b = 7.7267(6) ?, c = 19.9754(15) ?, β = 97.220(1)°, V = 1943.7(3) ?³, Z = 4, D = 1.355 Mg m⁻³. Compound 3a crystallized in the monoclinic P2₁/c space group with unit cell parameters a = 16.8137(14) ?, b = 10.5577(9) ?, c = 31.344(3) ?, β = 103.618(1)°, V = 5407.5(8) ?³, Z = 8, D = 1.308 Mg m⁻³. Compound 3b crystallized in the monoclinic Pc space group with unit cell parameters a = 15.594 ?, b = 12.564 ?, c = 18.339 ?, β = 90.224(1)°, V = 3593.0 ?³, Z = 4, D = 1.236 Mg m⁻³.     

Isothermic Submanifolds

We propose an answer to a question raised by F. Burstall: Is there any interesting theory of isothermic submanifolds of ? ⁿ of dimension greater than two? We call an n-immersion f(x) in ? ^m isothermic _k if the normal bundle of f is flat and x is a line of curvature coordinate system such that its induced metric is of the form $\sum_{i=1}^{n} g_{ii}\,\mathrm{d} x_{i}^{2}$ with $\sum_{i=1}^{n} \epsilon_{i} g_{ii}=0$ , where ?? _i =1 for 1??i??n?k and ?? _i =?1 for n?k<i??n. A smooth map (f ₁,??,f _n ) from an open subset ${\mathcal{O}}$ of ? ⁿ to the space of m×n matrices is called an n-tuple of isothermic _k n-submanifolds in ? ^m if each f _i is an isothermic _k immersion, $(f_{i})_{x_{j}}$ is parallel to $(f_{1})_{x_{j}}$ for all 1??i,j??n, and there exists an orthonormal frame (e ₁,??,e _n ) and a GL(n)-valued map (a _ij ) such that $\mathrm{d}f_{i}= \sum_{j=1}^{n} a_{ij} e_{j}\,\mathrm {d} x_{j}$ for 1??i??n. Isothermic₁ surfaces in ?³ are the classical isothermic surfaces in ?³. Isothermic _k submanifolds in ? ^m are invariant under conformal transformations. We show that the equation for n-tuples of isothermic _k n-submanifolds in ? ^m is the $\frac{O(m+n-k,k)}{O(m)\times O(n-k,k)}$ -system, which is an integrable system. Methods from soliton theory can therefore be used to construct Christoffel, Ribaucour, and Lie transforms, and to describe the moduli spaces of these geometric objects and their loop group symmetries.     

Nonlinear polarisation effects in optical microcoil resonators with fibre twist and birefringence

We study the nonlinear response of optical microcoil resonators (OMRs) based on twisted birefringent microfibres by incorporating Kerr nonlinearity into the underlying coupled mode equations. The resulting hysteresis characteristics were found to be highly polarisation dependent, with both the switching powers and contrast levels strongly influenced by the twist-induced cross-polarisation coupling. In addition, the existence of multiple bistability in OMRs is explored when the two orthogonal polarisations' resonances are spectrally close enough to influence the propagation of a monochromatic pump. Both the bistability and nonlinear switching may potentially be utilised for implementing polarisation-sensitive devices, especially for signal processing purposes, and benefit from the low threshold powers needed to observe nonlinear effects in OMRs.     

Synthesis and rotation barriers in 2, 6‐Di‐(o‐anisyl) anisole

Variable temperature ¹H NMR spectroscopic studies of 2, 6‐di(o‐anisyl) anisole show syn and anti atropisomers at low temperature. The barrier for interconverting these isomers by rotation about the aryl‐aryl bond, found by fitting the experimental data, is 41.2 kJ/mol. Copyright © 2012 John Wiley & Sons, Ltd.     

Gamma-ray bursts in the swift-Fermi era

Gamma-ray bursts （GRBs） are among the most violent occurrences in the universe. They are pow- erful explosions, visible to high redshift, and thought to be the signature of black hole birth. They are highly luminous events and provide excellent probes of the distant universe. GRB research has greatly advanced over the past 10 years with the results from Swift, Fermi and an active followup community. In this review we survey the interplay between these recent observations and the theoretical models of the prompt GRB emission and the subsequent afterglows.