- Stereocontrolled Synthesis of Functionalized Bicyclic α-Methylene Butyrolactones via Tungsten-Mediated Intramolecular Allylation of Aldehydes
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The syntheses of a series of CpW(CO)2(π-γ-lactonyl) complexes bearing a tethered aldehyde are described. These π-allyl complexes are prepared as either syn- or anti-stereoisomers. Treatment of these dicarbonyl complexes with NOBF4 and NaI in CH3CN effects an intramolecular allylation of the tethered aldehyde, yielding bicyclic α-methylene butyrolactones comprising a homoallylic alcohol. Both syn- and anti-isomers of tungsten-π-allyl compounds produce the same α-methylene butyrolactones. The cyclizations proceed with high diastereoselectivities to give only the cis-fused bicyclic γ-lactones. The preference for cis-fused stereoselection can be rationalized based on a tricyclic transition state mechanism.
- Shiu, Lin-Hun,Li, Yang-Lian,Li, Chien-Le,Lao, Ching-Yu,Chen, Wei-Chen,Yu, Chin-Hui,Liu, Rai-Shung
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Read Online
- TASTE MODULATING ALDEHYDES
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Aldehydes of formula (I) (X represents an alkyl or alkenyl group having up to 9 carbon atoms) for use in taste modulation and/or flavor compositions are provided. Specifically, the compounds of the presently disclosed subject matter provide effective and unexpected taste modulating properties. The taste modulation and/or flavor compositions can be incorporated into various consumer end products in particular in combination with high intensity sweeteners.
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Page/Page column 30
(2018/03/28)
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- Evolution of an Efficient and Scalable Nine-Step (Longest Linear Sequence) Synthesis of Zincophorin Methyl Ester
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Because of both their synthetically challenging and stereochemically complex structures and their wide range of often clinically relevant biological activities, nonaromatic polyketide natural products have for decades attracted an enormous amount of attention from synthetic chemists and played an important role in the development of modern asymmetric synthesis. Often, such compounds are not available in quantity from natural sources, rendering analogue synthesis and drug development efforts extremely resource-intensive and time-consuming. In this arena, the quest for ever more step-economical and efficient methods and strategies, useful and important goals in their own right, takes on added importance, and the most useful syntheses will combine high levels of step-economy with efficiency and scalability. The nonaromatic polyketide natural product zincophorin methyl ester has attracted significant attention from synthetic chemists due primarily to the historically synthetically challenging C(8)-C(12) all-anti stereopentad. While great progress has been made in the development of new methodologies to more directly address this problem and as a result in the development of more highly step-economical syntheses, a synthesis that combines high levels of step economy with high levels of efficiency and scalability has remained elusive. To address this problem, we have devised a new synthesis of zincophorin methyl ester that proceeds in just nine steps in the longest linear sequence and proceeds in 10% overall yield. Additionally, the scalability and practicability of the route have been demonstrated by performing all of the steps on a meaningful scale. This synthesis thus represents by a significant margin the most step-economical, efficient, and practicable synthesis of this stereochemically complex natural product reported to date, and is well suited to facilitate the synthesis of analogues and medicinal chemistry development efforts in a time- and resource-efficient manner.
- Chen, Liang-An,Ashley, Melissa A.,Leighton, James L.
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supporting information
p. 4568 - 4573
(2017/04/03)
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- Enantioselective hydroformylation of N-vinyl carboxamides, allyl carbamates, and allyl ethers using chiral diazaphospholane ligands
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Rhodium complexes of diazaphospholane ligands catalyze the asymmetric hydroformylation of N-vinyl carboxamides, allyl ethers, and allyl carbamates; products include 1,2- and 1,3-aminoaldehydes and 1,3-alkoxyaldehydes. Using glass pressure bottles, short reaction times (generally less than 6 h), and low catalyst loading (commonly 0.5 mol %), 20 substrates are successfully converted to chiral aldehydes with useful regioselectivity and high enantioselectivity (up to 99% ee). Chiral Roche aldehyde is obtained with 97% ee from the hydroformylation of allyl silyl ethers. Commonly difficult substrates such as 1,1- and 1,2-disubstituted alkenes undergo effective hydroformylation with 89-97% ee and complete conversion for six examples. Palladium-catalyzed aerobic oxidative amination of allyl benzyl ether followed by enantioselective hydroformylation yields the β3-aminoaldehyde with 74% ee.
- McDonald, Richard I.,Wong, Gene W.,Neupane, Ram P.,Stahl, Shannon S.,Landis, Clark R.
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supporting information; experimental part
p. 14027 - 14029
(2011/01/04)
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- NOVEL COMPOUNDS AS CANNABINOID RECEPTOR LIGANDS
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The present application relates to isothiazolylidene containing compounds of Formula (I) wherein R1, R2, R3, R4, and L are as defined in the specification, compositions comprising such compounds, and methods for treating conditions and disorders using such compounds and compositions.
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Page/Page column 71
(2010/06/11)
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- NOVEL COMPOUNDS AS CANNABINOID RECEPTOR LIGANDS
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The present application relates to isothiazolylidene containing compounds of Formula (I) wherein R1, R2, R3, R4, and L are as defined in the specification, compositions comprising such compounds, and methods of treating conditions and disorders using such compounds and compositions.
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Page/Page column 54-55
(2008/12/08)
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- Self-condensation of N-tert-butanesulfinyl aldimines: Application to the rapid asymmetric synthesis of biologically important amine-containing compounds
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(Chemical Equation Presented) Highly diastereoselective intra- and intermolecular self-condensation reactions of N-tert-butanesulfinyl aldimines have been developed and applied to the rapid, asymmetric synthesis of frans-2-aminocyclopentanecarboxylic acid and the drug candidate SC-53116. Key to both syntheses is a novel microwave-assisted reaction in which N-sulfinyl aldimines are cleanly converted into nitrites in high-yielding concerted elimination processes.
- Schenkel, Laurie B.,Ellman, Jonathan A.
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p. 3621 - 3624
(2007/10/03)
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- Electroactive and luminescent polymers: New fluorene-heterocycle-based hybrids
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The synthesis, characterization, and electrochromic properties of copolymers derived from 9,9-dialkyl-2,7-dibromofluorene (18a, alkyl = C10H21; 24, alkyl = Et) and pyrrole, thiophene, 3,4- ethylenedioxythiophene, and furan are described. Two synthetic routes to 9,9- diethyl-2,7-bis(pyrrol-2-yl)fluorene (30) afford product in 30% and 20% yields, respectively. Monomer 30 undergoes electropolymerization to yield electroactive polymer films. The lowest monomer oxidation potential (E(p,m) = 0.4 V vs. Ag/Ag+) is found in tetraethylammonium tosylate (TEATOS)-CH3CN, but film formation is slow. Spectroelectrochemical analysis of poly(30) reveals a band gap at 2.4 eV and upon polymer oxidation, two low energy absorptions peaking at 1.2 and 2.2 eV appear. This phenomenon is attributed to formation of bipolaron bands between the valence and conduction bands. Soluble fluorene-heterocycle polymers 34a-d have been synthesized by the Stille coupling reaction of 18a and 2,5-bis(trimethylstannyl)thiophene (21a), 5,5'-bis(trimethylstannyl)-2,2'-bithiophene (21b), 2,5- bis(trimethylstannyl)-3,4-ethylenedioxythiophene (21c), and 2,5- bis(trimethylstannyl)furan (22), respectively, in high yields. The NMR spectra are consistent with the proposed structures of the polymers 34a-d, and no evidence of ring opening of the furyl unit in 34d is seen in the NMR and IR spectra. The molecular weights of 34a-d are in the range of 8000 g mol-1 with polydispersity indices (PDI) of 2. Polymers 34a-c have band gaps measured at 2.4 eV, while polymer 34d has its gap at 2.6 eV. Polymers 34a-c undergo solution doping with SbCl5 to form new low energy bipolaron bands at the expense of the absorption in the UV-VIS. However, polymer 34d does not oxidatively dope with SbCl5.
- Tsuie, Barbara,Reddinger, Jerry L.,Sotzing, Gregory A.,Soloducho, Jadwiga,Katritzky, Alan R.,Reynolds, John R.
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p. 2189 - 2200
(2007/10/03)
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- A simple way to sequentially connected polycycles containing terminal pyrrole rings: Synthesis of possible precursors of materials for nonlinear optics
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the readily available 1,3-dioxolane-2-propanal allows the transformation of aromatic and heteroaromatic mono and dilithioderivatives into polycycles containing one or two pyrrole rings. Organolithiums bearing electron acceptor groups can be also employed affording possible precursors of materials for nonlinear optics.
- Lucchesini, Francesco
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p. 9951 - 9966
(2007/10/02)
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- Synthesis of Δ3-1-Methylene-1-carbacephems
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The total synthesis of (+/-)-1-methylene-2,2-dimethyl-7-amino-1-carbacephem-4-carboxylic acid (1) is described.The reaction scheme was essentially that described by Christensen et al. for the synthesis of (+/-)-1-carbacephems.In vitro antibacterial activities of the 7-phenoxyacetyl and 7-D-α-phenylglycyl derivatives of 1 were compared with those of 7-(phenoxyacetamido)desacetoxycephalosporanic acid and cefalexin.Derivatives of 1 were 2-4 times less active against most of the sensitive organisms than the corresponding 7-aminodesacetoxycephalosporanic acid analogues.The activity of the 7-D-α-phenylglycyl derivative of 1 however was about 20 times lower than that of cefalexin when measured against Staphylococcus aureus ATCC 6538P.
- Herdewijn, Piet,Claes, Paul J.,Vanderhaeghe, Hubert
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p. 661 - 664
(2007/10/02)
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