- What Is the True Structure of D609, a Widely Used Lipid Related Enzyme Inhibitor?
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(Chemical Equation Presented) D609 (1) has been used as a lipid-related enzyme inhibitor during the past three decades. Although it has eight possible stereoisomers, no systematic research considering its chirality has been performed. In this paper, eight possible chiral alcohols as direct precursors of D609 were synthesized, and their stereochemistries were elucidated by a vibrational circular dichroism (VCD) technique. Phosphatidylcholine-specific phospholipase C and sphingomyelin synthase inhibition assays of these isomers showed considerable differences in their activities.
- Kato, Mikako,Hammam, Mostafa A. S.,Taniguchi, Tohru,Suga, Yoshiko,Monde, Kenji
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supporting information
p. 768 - 771
(2016/03/01)
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- The anisotropic effect of functional groups in 1H NMR spectra is the molecular response property of spatial nucleus independent chemical shifts (NICS) - Conformational equilibria of exo/endo tetrahydrodicyclopentadiene derivatives
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The inversion of the flexible five-membered ring in tetrahydrodicyclopentadiene (TH-DCPD) derivatives remains fast on the NMR timescale even at 103 K. Since the intramolecular exchange process could not be sufficiently slowed for spectroscopic evaluation, the conformational equilibrium is thus inaccessible by dynamic NMR. Fortunately, the spatial magnetic properties of the aryl and carbonyl groups attached to the DCPD skeleton can be employed in order to evaluate the conformational state of the system. In this context, the anisotropic effects of the functional groups in the 1H NMR spectra prove to be the molecular response property of spatial nucleus independent chemical shifts (NICS).
- Kleinpeter, Erich,Laemmermann, Anica,Kuehn, Heiner
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p. 1098 - 1111
(2011/04/15)
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- Synthesis and Reactions of Tricyclic Monocarboxylic Acid Esters
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A convenient and efficient method for preparing tricyclic esters has been developed on the basis of addition of C1-C3 monocarboxylic acids to tricyclo2,6>deca-3,8-diene and its dimethyl derivatives in the presence of p-toluenesulfonic acid.The orientation of the ester group in the products has been determined.Some reactions of the resulting esters have been studied, and their possible applications have been proposed.
- Mamedov, M. K.
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p. 485 - 488
(2007/10/03)
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- Ion-molecule complexes in 1,2 alkyl shifts
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The internal return of neutral leaving groups was studied in rearrangements of polycyclic systems (2-norpinyl → 2-norbornyl, endo- → exo-tricyclo[5.2.1.02.6]dec-8-yl, bicyclo[3.2.0]hept-2-yl → 7-norbornyl, and 4-protoadamantyl → 2-adamantyl). Acid catalysis was applied to 18O-labeled alcohols in aqueous organic solvents, to alcohols in methanol, and to ethers R-O-R′ in alcohols R″-OH. The leaving group was found to attack the migration origin in competition with solvent molecules. Return:exchange ratios were obtained from product distributions, either directly or by kinetic simulation (in cases of partial exchange prior to rearrangement). If departure and return of the leaving group occur on the same side of the carbon framework, return:exchange ratios ranging from 1 to 11.5 were observed. Less internal return was found for bridged than for open carbocations. Migration of the departing molecule to the opposite face (exo ? endo) or to a β carbon is a minor process (return:exchange ~ 0.1), in accordance with previous reports on inverting displacements and allylic 1,3 shifts. These data are rationalized in terms of short-lived ion-molecule (ion-dipole) complexes whose collapse competes with ligand exchange.
- Gappa, Andrea,Herpers, Ekkehard,Herrmann, Roland,Hülsewede, Volker,Kappert, Wilhelm,Klar, Matthias,Kirmse, Wolfgang
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p. 12096 - 12106
(2007/10/03)
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- Linearly Fused vs Bridged Regioselection in the Intramolecular 1,3-Diyl Trapping Reaction
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The intramolecular diyl trapping reaction can now be used to obtain synthetically useful quantities of either bridged or linearly fused cycloadducts in a selective manner and by design.Bridged cycloadducts arise by intercepting the triplet diyl, while linearly fused products can be produced from either the singlet or the triplet.When an electron-withdrawing group is attached to the diylophile , the singlet diyl leads selectively to fused cycloadducts.On the other hand , the presence of a large alkyl group attached to the internal carbon of the diylophile affords bridged cycloadducts selectively from cycloaddition with the triplet.Four diazenes, 4-7, differing only in the electronic and steric properties of the substituent located on the internal carbon of the diylophile, were studied.The diyl trapping reactions were conducted using ca. 1 mM solutions of diazene in THF at reflux for periods of 3-4h; cycloadduct yields ranged from 68percent ( beginning with the dimethyl ketal 7) to 98percent ( from keto diazene 4).To determine the origin of the bridged cycloadducts, the effect of oxygen upon the product distribution was examined.The results show that the rate of the intramolecular triplet diyl cycloaddition is slower than the rate of the intermolecular reaction of the triplet with oxygen.The rate of triplet intramolecular cycloaddition can be estimated to be less than 4 x 106 to 4 x 107 s-1.
- Masjedizadeh, Mohammad R.,Dannecker-Doering, Ingeborg,Little, R. Daniel
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p. 2742 - 2752
(2007/10/02)
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