- Correction of Q Factor Effects for Simultaneous Collection of Elemental Analysis and Relaxation Times by Nuclear Magnetic Resonance
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A new method for measurement of elemental analysis by nuclear magnetic resonance (NMR) of unknown samples is discussed here as a quick and robust means to measure elemental ratios without the use of internal or external calibration standards. The determination of elemental ratios was done by normalizing the signal intensities by the frequency dependent quality factor (Q) and the gyromagnetic ratios (?) for each measured nucleus. The correction for the frequency dependence was found by characterizing the output signal of the probe as a function of the quality factor (Q) and the frequency, and the correction for γwas discussed in a previous study. A Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence was used for evaluation of the relative signal intensities, which allows for derivation of elemental ratios, and was correspondingly used to simultaneously measure the T2? of samples for an added parameter for more accurate identification of unknown samples.
- Widgeon Paisner, Scarlett,Janicke, Michael T.,Kaseman, Derrick C.,Frankle, Rachel K.,Yoder, Jacob L.,Alvarez, Marc A.,Espy, Michelle A.,Williams, Robert F.
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- TRIS(FLUOROALKOXY)METHYLPHOSPHONIUM SALTS IN THE SYNTHESIS OF METHYLPHOSPHORANES
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The reactions of phosphites containing electron-withdrawing fluoroalkyl groups with methyl triflate gave tris(fluoroalkoxy)methylphosphonium triflates, which react with alcohols to give either tetrakis(fluoroalkoxy)methylphosphoranes (in the case of fluoroalcohols) or alkylation products - ethers and bis(fluoroalkoxy)methylphosphonates (in the case of unsubstituted alcohols).The structures of the phosphonium salts and phosphoranes were supported by 1H and 31p NMR spectroscopy.
- Mironov, V. F.,Mavleev, R. A.,Konovalova, I. V.,Ofitserov, E. N.,Pudovik, A. N.
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- A Green Process for the Preparation of Bis(2,2,2-trifluoroethyl) Methylphosphonate
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Bis(trifluoroethyl) methylphosphonate is the starting material for the synthesis of Jin's reagent. Jin's reagent is widely used for the preparation of (Z)-α,β-unsaturated ketones and is also a valuable potent flame-retardant additive. Preparation of bis(trifluoroethyl) methylphosphonate was investigated by direct transesterification of dimethyl methylphosphonate with 2,2,2-trifluoroethanol (further trifluoroethanol, TFE), being a well-known weak nucleophile, using microwave and flow reactors. Direct transesterification was successful in a continuous flow reactor at 450 °C and 200 bar using a highly diluted reaction mixture. The product, bis(trifluoroethyl) methylphosphonate, was purified by column chromatography, and excess trifluoroethanol was recovered by distillation.
- Molnár, Katalin,Takács, László,Faigl, Ferenc,Kardos, Zsuzsanna
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p. 1985 - 1989
(2017/12/26)
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- DBU-promoted alkylation of alkyl phosphinates and H-phosphonates
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The alkylation of alkyl phosphinates and some H-phosphonate diesters is promoted by the base DBU. Only more reactive alkyl halides react in preparatively useful yields. However, the method provides easy access to important H-phosphinate building blocks, without the need for a protecting group strategy or metal catalysts. The reaction is conveniently conducted at, or below, room temperature. The preparation of methyl-H-phosphinate esters is particularly interesting as it avoids the heretofore more common use of methyldichlorophosphine MePCl2.
- Gavara, Laurent,Petit, Christelle,Montchamp, Jean-Luc
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supporting information
p. 5000 - 5003
(2012/11/07)
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- LAULIMALIDE ANALOGS AND USES THEREOF
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The present invention provides compounds having formula 1: (I) and pharmaceutically acceptable derivatives thereof, wherein R1-R10, q, t, X0, X1, A, B, D, E, G, J, K, L, M and Z are as described generally and in classes and subclasses herein, and additionally provides pharmaceutical compositions thereof, and methods for the use thereof for the treatment of disorders associated with cellular hyperproliferation.
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Page/Page column 151
(2010/02/11)
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- SYNTHESIS OF DISCODERMOLIDE
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The invention relates to a process for preparing discodermolide, for preparing intermediates for the manufacture of discodermolide and discodermolide analogues and to the intermediates obtained during the process. Wherein the process proceeds via a tetrae
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- Synthetic studies toward the microtubule-stabilizing agent laulimalide: Synthesis of the C1-C14 fragment
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The C1-C14 fragment of the paclitaxel-like antimicrotubule agent laulimalide has been synthesized in 15 steps from L-(-)-citronellal. The C9 chiral center was established using an asymmetric allylation, the dihydropyran ring was prepared through ring-closing metathesis, and the exo-methylene was incorporated using Eschenmoser's salt.
- Nadolski, Geoffry T.,Davidson, Bradley S.
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p. 797 - 800
(2007/10/03)
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- Total synthesis of microtubule-stabilizing agent (-)-laulimalide
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An enantioselective first total synthesis of laulimalide (1) is described. Laulimalide, a remarkably potent antitumor macrolide, has been isolated from the Indonesian sponge Hyattella sp. and the Okinawan sponge Fasciospongia rimosa. Laulimalide represents a new class of antitumor agents with significant clinical potential. The synthesis is convergent and involved the assembly of C3-C16 segment 4 and C17-C28 segment 5 by Julia olefination. The sensitive C2-C3 cis-olefin functionality was installed by Yamaguchi macrolactonization of a hydroxy alkynic acid followed by hydrogenation of the resulting alkynoic lactone over Lindlar's catalyst. Initial attempts of intramolecular Still's variant of Horner - Emmons olefination between the C19-phosphonocetate and C3-aldehyde provided a 1:2 mixture of cis- and trans-macrolactones. The trans-isomer was photo-isomerized to a mixture of cis- and trans-isomers. The other key steps involved ring-closing olefin metathesis to construct both dihydropyran units, stereoselective anomeric alkylation to functionalize the dihydropyran ring, stereoselective reduction of the resulting alkynyl ketone to set the C20-hydroxyl stereochemistry, and a novel Julia olefination protocol for the installation of the C13-exomethylene unit. The sensitive epoxide at C16-C17 was introduced in a highly stereoselective manner by Sharpless epoxidation at the final stage of the synthesis.
- Ghosh,Wang,Kim
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p. 8973 - 8982
(2007/10/03)
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- Fluorinated phosphorus compounds: Part 2. The synthesis of some bis(fluoroalkyl) alkylphosphonates
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Twenty bis(fluoroalkyl) alkylphosphonates of structure (RFO)2P(O)R were prepared in 28-69% yields by treatment of alkylphosphonic dichlorides Cl2P(O)R [R=Me, Et, n-Pr, i-Pr] with fluoroalcohols RFOH [RF=CF3CH2, H(CF2)2CH2, C2F5CH2, C3H7CH2, (CF3)2CH] in diethyl ether in the presence of triethylamine. Reactions of isopropylphosphonic dichloride with two molar equivalents of alcohols and fluoroalcohols were compared. After 12h at room temperature, the alcohols EtOH, n-PrOH, i-PrOH and n-BuOH gave mixtures of monoesters and diesters, except isopropanol, which gave the monoester exclusively. Electronic and steric effects caused by the alkoxy substituents satisfactorily account for the product ratios. With the fluoroalcohols CF3CH2OH, C2F5CH2OH, C3F7CH2OH and (CF3)2CHOH, the diesters predominated. Here the electronic effects of the fluoroalkoxy substituents stabilise the intermediate phosphoranes, eg. Cl2(RFO)P(OH)i-Pr and Cl(RFO)2P(OH)i-Pr, and drive the reactions to completion. Steric effects are clearly much less important in the case of attack by fluorinated alcohols.
- Timperley, Christopher M.,Broderick, John F.,Holden, Ian,Morton, Ian J.,Waters, Matthew J.
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- A convenient method for the synthesis of bis-trifluoroethyl phosphonoacetates
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Bis-trifluoroethyl phosphonoacetates were easily obtained by condensation of bis-trifluoroethyl alkylphosphonates with alkyl chloroformates in the presence of 2 equivalents of lithium hexamethyldisilazane (LiHMDS).
- Patois,Savignac,About-Jaudet,Collignon
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p. 2391 - 2396
(2007/10/02)
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