AHP model for performance evaluation of employees in a Czech management consulting company

Central European Journal of Operations Research - The article is focused on an application of the analytic hierarchy process (AHP) to the performance evaluation of employees of a management...     

Determination of estradiol and its degradation products by liquid chromatography

A novel HPLC method for simultaneous determination of estradiol and its seven degradation products in topical gel was developed. Zorbax SB-CN (150 mm x 4.6 mm, 5 microm) analytical column and mobile phase composed of acetonitrile, phosphoric acid 0.085%, and tetrahydrofurane (27:63:10, v/v/v) at flow-rate 1.0 ml min(-1) were used for the chromatographic separation using UV detection at 225 nm. The active substance estradiol was separated from all its known degradation products successfully. Two degradation products estrone and Delta(9(11))-estrone were not separated sufficiently, their peaks were evaluated as a sum of two components. The method was validated according to ICH guideline recommendations and thereafter it was successfully applied for stability tests of topical cream Estrogel HBF in the quality control laboratory. Limits of detection for degradation products ranged from 1.03 x 10(-5) to 1.14 x 10(-4) mg ml(-1), limits of quantitation for degradation products were in the range 3.43 x 10(-5) to 3.81 x 10(-4) mg ml(-1). The developed method is selective, precise, accurate and sensitive enough for determination of estradiol and its known degradation products.     

Total Synthesis of Tiacumicin B: Study of the Challenging β-Selective Glycosylations**

We give a full account of the total synthesis of tiacumicin B (Tcn-B), a natural glycosylated macrolide with remarkable antibiotic properties. Our strategy is based on our experience with the synthesis of the tiacumicin B aglycone and on unique 1,2-cis-glycosylation steps. We used sulfoxide anomeric leaving-groups in combination with a remote 3-O-picoloyl group on the donors that allowed highly β-selective rhamnosylation and noviosylation that rely on H-bond-mediated aglycone delivery. The rhamnosylated C1–C3 fragment was anchored to the C4–C19 aglycone fragment by a Suzuki–Miyaura cross-coupling. Ring-size-selective Shiina macrolactonization provided a semiglycosylated aglycone that was engaged directly in the noviolysation step with a virtually total β-selectivity. Finally, a novel deprotection method was devised for the removal of a 2-naphthylmethyl ether on a phenol, and efficient removal of all the protecting groups provided synthetic tiacumicin B.     

Oxidation of small unsaturated methyl and ethyl esters

The ignition delay times were measured behind reflected shock waves for temperatures from 1280 to 1930 K, pressures from of 7–9.65 atm, fuel concentrations of 0.4, 0.5, and 1%, and equivalence ratios equal to 0.25, 1.0, and 2.0 in the cases of four unsaturated esters: methyl crotonate, methyl acrylate, ethyl crotonate, and ethyl acrylate. Ignition delay times were measured using chemiluminescence emission from OH at 306 nm and piezoelectric pressure measurements made at the shock tube sidewall. No important difference of reactivity was observed between methyl and ethyl unsaturated esters, methyl and ethyl crotonate having the same reactivity as methyl butanoate. The reactivity of acrylates is greater than that of crotonates especially at the lowest investigated temperatures. Detailed mechanisms for the combustion of the four studied unsaturated esters have been automatically generated using the version of EXGAS software recently improved to take into account this class of oxygenated reactants. These mechanisms have been validated through satisfactory comparison of simulated and experimental results. The main reaction pathways have been derived from flow rate and sensitivity analyses. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 204–218, 2011     

Fluorine conformational effects in organocatalysis: an emerging strategy for molecular design

Molecular design strategies that profit from the intrinsic stereoelectronic and electrostatic effects of fluorinated organic molecules have mainly been restricted to bio-organic chemistry. Indeed, many fluorine conformational effects remain academic curiosities with no immediate application. However, the renaissance of organocatalysis offers the possibility to exploit many of these well-described phenomena for molecular preorganization. In this minireview, we highlight examples of catalyst refinement by introduction of an aliphatic C-F bond which functions as a chemically inert steering group for conformational control.