Synthesis of Novel Ethyl (substituted)phenyl‐4‐oxothiazolidin‐3‐yl)‐1‐ethyl‐4‐oxo‐1,4‐dihydroquinoline‐3‐Carboxylates as Potential Anticancer Agents

A series of ethyl (substituted)phenyl‐4‐oxothiazolidin‐3‐yl)‐1‐ethyl‐4‐oxo‐1,4‐dihydroquinoline‐3‐carboxylates ( 7a , 7b , 7c , 7d , 7e , 7f , 7g ) has been prepared from reactions between aminoquinolones 6 with arenealdehydes and mercaptoacetic acid. The critical intermediates, 6 a and 6b , were obtained from appropriate amines by a sequence of steps involving (i) reaction with diethylethoxymethylenemalonate, (ii) thermal cyclization in diphenyl ether, (iii) ethylation and (iv) Pd/C catalyzed reduction. New compounds 7a , 7b , 7c , 7d , 7e , 7f , 7g were fully identified and characterized by NMR (¹H and ¹³C) and specifically for 7d by X‐ray crystallography. Compounds 7b , 7c , 7d , 7e , 7f were found not to exhibit activity at 10 uM concentrations against gastric ascitis (AGP‐01), gastric adenocarcinoma kind intestinal (ACP‐02), colon (HCT‐116) and murine melanome (B16F10) cancer cells. However, none exhibited cytotoxicity against normal cells human fibroblast (MRC‐5), murine fibroblast (NIH3T3) and normal human melanocyte (Melan‐A).     

Straightforward synthesis of sphinganines via a serine-derived Weinreb amide

Sphinganines can be synthesized in just three steps from easily prepared serine-derived Weinreb amide 4. Pre-deprotonation of the acidic (N-H and O-H) protons of 4 allows for its efficient conversion to amino ketones 5. Such ketones can be selectively reduced to either erythro- or threo-sphinganines. Partially protected sphinganines 11 are also readily accessible in five steps from 4. Thus, Weinreb amide 4 represents one of the most versatile templates described to date for sphinganine synthesis.     

Direct determination of selenium in urine samples by electrothermal atomic absorption spectrometry using a Zr plus Rh-treated graphite tube and co-injection of Rh as chemical modifier

Different chemical modifiers for use with electrothermal atomic absorption spectrometry (ET AAS) were investigated in relation to determining the selenium in human urine samples. The samples were diluted in a solution containing 1% v/v HNO₃ and 0.02% m/v cetyltrimethylammonium chloride (CTAC). Studying the modifiers showed that the use of either Ru or Ir as the permanent modifier gave low sensitivity to Se and the peak shape was very noisy, while Zr or Rh gave no peak at all. The same occurred when Zr was used in solution. For mixtures of permanent modifiers, Ir plus Rh or Zr plus Rh gave very low sensitivity, Zr plus Rh with co-injection of Ir in solution was also not efficient, Zr plus Rh in solution gave good sensitivity, but the best results were obtained with a mixture of Zr and Rh as the permanent modifier and co-injection of Rh in solution. Using this last modifier, the following dilutions with the HNO₃ and CTAC were studied: 1:1, 1:2, 1:3 and 1:4. The best dilution was 1:1, which promoted good sensitivity and a more defined peak shape and made it possible to correct for the background using a deuterium arc lamp. Under these conditions, a characteristic mass of 26±0.2 pg was obtained for Se in aqueous solution. Six certified urine samples were analyzed using matrix matching calibration and the measured concentrations were in agreement with the certified values, according to a t-test at the 95% confidence level. Recovery tests were carried out and the recoveries were in the range 100–103%, with relative standard deviation better than 9%. The limit of detection (LOD, 3 sd, n=10) was 3.0 μg L⁻¹ in the sample. The treated graphite tube could be used for at least 600 atomization cycles without significant alteration of the analytical signal.     

Photostability of 4,4′‐Dihydroxythioindigo,a Mimetic of Indigo

The photochemical properties of indigo, a widely used industrial dye, has attracted both experimentalists and theoreticians from the beginning. Especially the high photostability of indigo has been the subject of intensive research. Recently, it was proposed that after photoexcitation an intramolecular proton transfer followed by a nonradiative relaxation to the ground state promote photostability. In indigo the hydrogen bond and the proton transfer occur between the opposing hemiindigo parts. Here, we provide experimental and theoretical evidence that a hydrogen transfer within one hemiindigo or hemithioindigo part is sufficient to attain photostability. This concept can serve as an interesting strategy towards new photostable dyes for the visible part of the spectrum.     

Tail behavior of conditional sojourn times in Processor-Sharing queues

We investigate the tail behavior of the sojourn-time distribution for a request of a given length in an M/G/1 Processor-Sharing (PS) queue. An exponential asymptote is proven for general service times in two special cases: when the traffic load is sufficiently high and when the request length is sufficiently small. Furthermore, using the branching process technique we derive exact asymptotics of exponential type for the sojourn time in the M/M/1 queue. We obtain an equation for the asymptotic decay rate and an exact expression for the asymptotic constant. The decay rate is studied in detail and is compared to other service disciplines. Finally, using numerical methods, we investigate the accuracy of the exponential asymptote. AMS 2000 Subject Classifications Primary:60K25,Secondary: 60F10,68M20,90B22     

Computational studies of peripheral ring twisting in meso-N-methyl pyridyl-substituted porphyrins

Semiempirical molecular orbital calculations for the porphyrins tetrakis(4-N-methyl pyridyl)porphine (H₂TMpyP-4) and tetrakis(2-N-methyl pyridyl)porphine using the MNDO and AM -1 Hamiltonians suggest that twisting one or more of the pyridinium rings results, at considerable energy expense, in highly nonplanar macrocycle configurations as the exocyclic ring(s) approach coplanarity. The results imply that the mechanism of intercalation of H₂TMpyP-4 into DNA cannot require twisting the exocyclic rings anywhere close to coplanarity with the central porphine core, but involves, instead, the inherent flexibility of DNA itself. © 1993 John Wiley & Sons, Inc.     

Congener-specific identification of technical PCB mixtures by capillary gas chromatography on a n-octyl-methyl silicone phase (SB-Octyl 50) with electron capture- and mass-selective detection

Summary The technical PCB mixtures Aroclor 1242, Aroclor 1254 and Aroclor 1260 have been analyzed by capillary gas chromatography using the new methyl n-octylpolysiloxane phase (SB-Octyl 50) with electron capture- and mass-selective detection. The selectivity of this new stationary phase in the separation of PCB is superior to that of the methyl-polysiloxanes. A pronounced separation according to the out-of-plane orientation of the PCB congeners is observed.

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Kongeneren-spezifische Identifizierung der technischen PCB-Gemische durch HRGC/ECD und HRGC/MSD mit einer n-Octyl-methyl-silicon-Phase

     

Some Boolean Algebras with Finitely Many Distinguished Ideals I

We consider the theory Th_prin of Boolean algebras with a principal ideal, the theory Th_max of Boolean algebras with a maximal ideal, the theory Th_ac of atomic Boolean algebras with an ideal where the supremum of the ideal exists, and the theory Th_sa of atomless Boolean algebras with an ideal where the supremum of the ideal exists. First, we find elementary invariants for Th_prin and Th_sa. If T is a theory in a first order language and α is a linear order with least element, then we let Sentalg(T) be the Lindenbaum-Tarski algebra with respect to T, and we let intalg(α) be the interval algebra of α. Using rank diagrams, we show that Sentalg(Th_prin) ? intalg(ω⁴), Sentalg(Th_max) ? intalg(ω³) ? Sentalg(Th_ac), and Sentalg(Th_sa) ? intalg(ω² + ω²). For Th_max and Th_ac we use Ershov's elementary invariants of these theories. We also show that the algebra of formulas of the theory Tx of Boolean algebras with finitely many ideals is atomic.