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131.
Garo Horozoglu Armen Carlos Braunstein Mitchell I. Weinstein A.David Baker 《Tetrahedron letters》1979,20(43):4197-4200
Azoxyanisole, but not azoxybenzene, reacts readily with oxalyl chloride to give the corresponding orth-substituted azocompound. The differences in reactivity are discussed in terms of different HOMO energies, measured by PES. 相似文献
132.
Jonathan Fine Judy Kuan-Yu Liu Armen Beck Kawthar Z. Alzarieni Xin Ma Victoria M. Boulos Hilkka I. Kenttmaa Gaurav Chopra 《Chemical science》2020,11(43):11849
Diagnostic ion–molecule reactions employed in tandem mass spectrometry experiments can frequently be used to differentiate between isomeric compounds unlike the popular collision-activated dissociation methodology. Selected neutral reagents, such as 2-methoxypropene (MOP), are introduced into an ion trap mass spectrometer where they react with protonated analytes to yield product ions that are diagnostic for the functional groups present in the analytes. However, the understanding and interpretation of the mass spectra obtained can be challenging and time-consuming. Here, we introduce the first bootstrapped decision tree model trained on 36 known ion–molecule reactions with MOP. It uses the graph-based connectivity of analytes'' functional groups as input to predict whether the protonated analyte will undergo a diagnostic reaction with MOP. A Cohen kappa statistic of 0.70 was achieved with a blind test set, suggesting substantial inter-model reliability on limited training data. Prospective diagnostic product predictions were experimentally tested for 13 previously unpublished analytes. We introduce chemical reactivity flowcharts to facilitate chemical interpretation of the decisions made by the machine learning method that will be useful to understand and interpret the mass spectra for chemical reactivity.We combine mass spectrometry with machine learning that is predictive and explainable using chemical reactivity flowcharts for diagnostic ion–molecule reactions. 相似文献
133.
Krueger EB Hopkins TP Keaney MT Walters MA Boldi AM 《Journal of combinatorial chemistry》2002,4(3):229-238
The solution-phase synthesis of amido-, urea-, and aminofuranoses was achieved. Alkylated furanose aldehydes were treated with primary amines in the presence of sodium triacetoxyborohydride to give secondary amines. Subsequent acylation with acid chlorides and isocyanates afforded amidofuranoses and ureafuranoses, respectively. Second, reductive amination of furanose aldehydes with secondary amines yielded tertiary amines. The resulting acetonides were treated with alcohols in the presence of acid to yield mixed acetals. In the library syntheses, functionalized scavenger resins were used in the purification of intermediates and products. 相似文献
134.
Yan B Fang L Irving M Zhang S Boldi AM Woolard F Johnson CR Kshirsagar T Figliozzi GM Krueger CA Collins N 《Journal of combinatorial chemistry》2003,5(5):547-559
The quality of combinatorial libraries determines the success of biological screening in drug discovery programs. In this paper, we evaluate and compare various methods for measuring identity, purity, and quantity (yield) of combinatorial libraries. Determination of quantitative purity reveals the true library quality and often indicates potential quality problems before full-scale library production. The relative purity can be determined for every member in a large library in a high-throughput mode, but must be cautiously interpreted. In particular, many impurities are not observable by relative purity measurements using detectors such as UV(214), UV(254), and evaporative light-scattering detection. These "invisible" impurities may constitute a significant portion of the sample weight. We found that TFA, plastic extracts, inorganic compounds, and resin washout are among these impurities. With compelling evidence, we reach a conclusion that purification is the only way to remove "invisible" impurities and improve the quantitative purity of any compound even though some compounds may have a high relative purity before purification. 相似文献
135.
Voituriez A Panossian A Fleury-Brégeot N Retailleau P Marinetti A 《Journal of the American Chemical Society》2008,130(43):14030-14031
Planar chiral phosphines displaying a new ferrocenophane scaffold have been prepared via a stereoselective approach. The P-cyclohexyl substituted phosphine affords high levels of asymmetric induction in the organocatalytic [3 + 2] annulation reaction between allenes and electron-poor olefins. 相似文献
136.
Alpha-alkoxy ketones 3 can be transformed into 1-alkynyl ethers 5 by a two-step procedure involving formation of the enol triflate or phosphate and base-induced elimination. Performing the same reaction sequence with allylic alcohols (R2OH, R2 = allyl) furnishes instead gamma,delta-unsaturated carboxylic acid derivatives 6, derived from [3,3]-sigmatropic rearrangement of the intermediate allyl alkynyl ethers at -78 degrees C and trapping of the subsequently formed ketene with nucleophiles (Nu-H). Benzyl alkynyl ether 5 (R2 = benzyl) rearranges to indanone 7 upon heating to 60 degrees C. 相似文献
137.
Let hR denote an L∞ normalized Haar function adapted to a dyadic rectangle R⊂d[0,1]. We show that for choices of coefficients α(R), we have the following lower bound on the L∞ norms of the sums of such functions, where the sum is over rectangles of a fixed volume:
138.
139.
Astghik Mikayelyan Armine Aleksanyan Mariam Sargsyan Arpine Gevorgyan Hasmik Zakaryan Armen Harutyunyan Lusine Zhamharyan Yeghig Armoudjian Tigran Margaryan 《Biomedical chromatography : BMC》2020,34(1):e4710
A protein precipitation method for the determination of clobazam (CLB) and its major active metabolite N-desmethylclobazam (N-CLB) in human plasma by liquid chromatography tandem mass spectrometry (LC–MS/MS) was established. CLB and N-CLB were extracted from human plasma samples by protein precipitation with methanol. Analyte separation was done using a Phenomenex Kinetex™ Biphenyl (50 × 2.1 mm, 1.7 μm) column using isocratic elution with a mobile phase of 5 mm ammonium formate with 0.01% ammonium hydroxide (40%) and methanol (60%) at a flow rate of 0.4 mL/min and an injection volume of 10 μL. The detection was performed on a triple quadrupole mass spectrometer in multiple reaction monitoring mode to monitor the precursor-to-product ion transitions of m/z 301.1 → 259.0, 306.0 → 263.9 for CLB and CLB-D5 and 287.0 → 245.0, 292.0 → 250.0 for N-CLB and N-CLB-D5 in positive electrospray ionization mode, respectively. The method was validated over a concentration range of 2.0–750 ng/mL for CLB and 0.7–200 ng/mL for N-CLB on SCIEX Triple Quad 4500 MS System. Total run time was 5 min. This method has been designed for bioequivalence study for formulations containing 20 mg of CLB. 相似文献
140.
A Major Advance in the Synthesis of Fluoroalkyl Pyrazoles: Tuneable Regioselectivity and Broad Substitution Patterns
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Etienne Schmitt Dr. Armen Panossian Dr. Jean‐Pierre Vors Dr. Christian Funke Dr. Norbert Lui Dr. Sergiy Pazenok Dr. Frédéric R. Leroux 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(32):11239-11244
A novel approach towards highly functionalized fluoroalkyl pyrazoles was developed by using fluoroalkyl amino reagents in combination with a variety of fluorinated ketimines. Tuneable introduction of fluoroalkyl groups in the 3‐ and 5‐positions was possible by using vinamidinium intermediates or the corresponding enamino ketones after hydrolysis. These high‐value building blocks can give rise to a large number of analogues for bioactivity screening and discovering new heterocyclic bioactive ingredients in various life science fields. 相似文献