- Detection and determination of p-coumaroylated units in lignins
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The derivatization followed by reductive cleavage (DFRC) method cleaves α- and β-ethers in lignins but leaves lignin γ-esters intact. When applied to grasses, which contain p-coumarate esters on their lignins, esterified monolignol derivatives are release
- Lu, Fachuang,Ralph, John
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Read Online
- Preparation process of dihydrooat alkaloid D
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The invention relates to a preparation process of dihydrooat alkaloid D. The preparation process comprises the following three steps: phenolic hydroxyl group protection, acylating chlorination and amidation, and hydrolysis deprotection, wherein p-hydroxyp
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Paragraph 0029; 0045; 0053-0054; 0065; 0070; 0071
(2021/06/13)
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- Preparation method of avenanthramide and derivative thereof
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The invention provides a preparation method of avenanthramide and a derivative thereof. The avenanthramide and the derivative thereof are synthesized and obtained by mainly utilizing an organic acid and aminobenzoic acid as major reactants. The method is
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Paragraph 0015
(2017/08/19)
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- Hypervalent iodine(III)-mediated tandem oxidative reactions: Application for the synthesis of bioactive polyspirocyclohexa-2,5-dienones
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In 2002, we reported the first total syntheses of potent antimalarial natural products, the aculeatins, employing the concept of tandem oxidative reactions mediated by hypervalent iodine(III) reagent to access to polyspirocyclohexa-2,5-dienone cores in ve
- Traoré, Mariam,Ahmed-Ali, Soumeth,Peuchmaur, Marine,Wong, Yung-Sing
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experimental part
p. 5863 - 5872
(2010/09/08)
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- Stereoselectivity control by oxaspiro rings during Diels-Alder cycloadditions to cross-conjugated cyclohexadienones: The syn oxygen phenomenon
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The diastereofacial selectivity operating in Diels-Alder additions involving spirocyclic cross-conjugated cyclohexadienones with dienes of varying reactivity has been investigated. The study has included the ether series 1a-c as well as the lactone/ketone pair 2a/2b. In all cases, the preferred [4+2] cycloaddition pathway consisted of bonding from that π-surface syn to the oxygen atom. 4-Substituted-4-methyl-2,5-cyclohexadienones (monocyclic systems) were also examined and found to undergo bond formation preferentially from the face bearing the more electron-withdrawing of the two groups at the 4 position. Kinetic parameters were determined for the cycloaddition of 1a and 2a to cyclopentadiene. The rate acceleration profile of solvents was in the order CF3CH2OH ? CH3CN~CH2Cl 2 for the production of 9a from 1a and CF3CH2OH ? CH2Cl2 > CH3CN for the production of 21a from 2a, respectively. This spread in polarity had no major impact on product distribution, a phenomenon also reflected in the behavior of 4-substituted-4-methyl-2,5-cyclohexadienones under comparable conditions. Theoretical assessment of these experimental facts was undertaken at the HF/6-31G* level. The facial selectivity is understandable in terms of the secondary interaction between the HOMO of the diene and LUMO of the dienophile as well as the effective hyperconjugation between the newly forming bond and the 4-anti-C-C σ-orbital due to the more electron-donating bond, as defined by the Cieplak model.
- Ohkata, Katsuo,Tamura, Yukiko,Shetuni, Brandon B.,Takagi, Ryukichi,Miyanaga, Wataru,Kojima, Satoshi,Paquette, Leo A.
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p. 16783 - 16792
(2007/10/03)
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- Design, synthesis, and proposed active site binding analysis of monocyclic 2-azetidinone inhibitors of prostate specific antigen
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A homology derived molecular model of prostate specific antigen (PSA) was created and refined. The active site region was investigated for specific interacting functionality and a binding model postulated for the novel 2-azetidinone acyl enzyme inhibitor 1 (IC50 = 8.98 ± 0.90 μM) which was used as a lead compound in this study. A single low energy conformation structure II (Figure 2) was adopted as most likely to represent binding after minimization and dynamics calculations. Systematic analysis of the binding importance of all three side chains appended to the 2-azetidinone was conducted by the synthesis of several analogues. A proposed salt bridge to Lys-145 with 4 (IC50 = 5.84 ± 0.92 μM) gave improved inhibition, but generally the binding of the N-1 side chain in a specific secondary aromatic binding site did not tolerate much structural alteration. A hydrophobic interaction of the C-4 side chain afforded inhibitor 6 (IC50 = 1.43 ± 0.19 μM), and polar functionality could also be added in a proposed interaction with Gln-166 in 5 (IC50 = 1.34 ± 0.05 μM). Reversal of the C-4 ester connectivity furnished inhibitors 7 (IC50 = 1.59 ± 0.15 μM), 11 IC50 = 3.08 ± 0.41 μM) and 13 (IC50 = 2.19 ± 0.36 Mμ) which were perceived to bind to PSA by a rotation of 180° relative to the C-4 ester of normal connectivity. Incorporation of hydroxyl functionality into the C-3 side chain provided 16 IC50 = 348 ± 50 nM) with the greatest increase in PSA inhibition by a single modification. Multiple copy simultaneous search (MCSS) analysis of the PSA active site further supported our model and suggested that 18 would bind strongly. Asymmetric synthesis yielded 18 (IC50 = 226 ± 10 nM) as the most potent inhibitor of PSA reported to date. It is concluded that our design approach has been successful in developing PSA inhibitors and could also be applied to the inhibition of other enzymes, especially in the absence of crystallographic information.
- Adlington,Baldwin,Becker,Chen,Cheng,Cooper,Hermann,Howe,McCoull,McNulty,Neubauer,Pritchard
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p. 1491 - 1508
(2007/10/03)
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- Regioselective intramolecular oxidation of phenols and anisoles by dioxiranes generated in situ
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A novel method for regioselective oxidation of phenols and anisoles has been developed in which dioxiranes, generated in situ from ketones and Ozone, oxidize phenol derivatives in an intramolecular fashion. A series of ketones with electron-withdrawing groups, such as CF3, COOMe, and CH2Cl, were attached to phenols, anisoles, or aryl rings via a C2 or C3 methylene linker. In a homogeneous solvent system of CH3CN and H2O, oxidation of phenol derivatives 1-10 afforded spiro 2-hydroxydienones in 24-55% yields regardless of the presence of other substituents (ortho Me, meta Me or Br) on the aryl ring and the length of the linker. Experimental evidences were provided to support the mechanism that involves a regioselective π bond epoxidation of aryl rings followed by epoxide rearrangement and hemiketal formation.
- Yang, Dan,Wong, Man-Kin,Yan, Zheng
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p. 4179 - 4184
(2007/10/03)
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- Design and synthesis of novel monocyclic β-lactam inhibitors of prostate specific antigen
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A novel series of monocyclic β-lactam analogues was designed using a homology derived model of prostate specific antigen (PSA) and by application of a multiple copy simultaneous search technique. Syntheses were conducted by assembly of the β-lactam core v
- Adlington, Robert M.,Baldwin, Jack E.,Chen, Beining,Cooper, Stephen L.,McCoull, William,Pritchard, Gareth J.,Howe, Trevor J.,Becker, Gerald W.,Hermann, Robert B.,McNulty, Ann M.,Neubauer, Blake L.
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p. 1689 - 1694
(2007/10/03)
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- STUDIES ON THE SYNTHESES OF SPIRO-DIENONE COMPOUNDS. VII. NOVEL SYNTHESIS OF THE SPIRODECANE CARBON FRAMAWORK
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Copper(I) halide-catalyzed decompositio of phenolic α-diazoketones gave spirodeca-6,9-diene-2,8-dione in high yield.Keywords - spiro-dienone; spirodecane; spiro annelation reaction; phenolic α-diazoketone; carbenoid
- Iwata, Chuzo,Yamada, Minoru,Shinoo, Yasutaka,Kobayashi, Kazue,Okada, Hideko
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p. 1932 - 1934
(2007/10/02)
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