- Structural elucidation of dendritic host-guest complexes by X-ray crystallography and molecular dynamics simulations
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The multiple monovalent binding of adamantyl-urea poly(propyleneimine) dendrimers with carboxylic acid-urea guests was investigated using molecular dynamics simulations and X-ray crystallography to better understand the structure and behavior of the dynam
- Chang, Theresa,Pieterse, Koen,Broeren, Maarten A.C.,Kooijman, Huub,Spek, Anthony L.,Hilbers, Peter A.J.,Meijer
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- Regio- and Diastereoselective and Enantiospecific Metal-Free C(sp3)-H Arylation: Facile Access to Optically Active 5-Aryl 2,5-Disubstituted Pyrrolidines
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Optically active 5-aryl 2,5-disubstituted pyrrolidines are the principal structural moiety of many bioactive compounds including natural products and catalysts for asymmetric synthesis. A highly regio- and diastereoselective and enantiospecific method for direct C-H arylation of aliphatic amine has been developed. Structurally diverse enantiopure arylated pyrrolidines were synthesized from commercially available starting materials, through a single-step three-component reaction under metal- and oxidant-free conditions. Furthermore, the complex analogous structure of CCK antagonist RP 66803 and angiotensin-converting enzyme inhibitors was easily constructed using the synthesized arylated pyrrolidine derivative. Detailed theoretical calculations (M06-2X/TZVPP/SMD//M06-2X/6-31+G(d,p) level) were also carried to investigate the mechanism and high level of stereocontrol involved in this direct sp3 C-H arylation reaction. Preference for a given regio- and stereoselectivity in the arylated product can be explained through elucidation of the mechanism for dehydration, generating azomethine ylide, and for the final re-aromatization step. The calculated energies reveals that the re-aromatization step is essentially rate determining, accompanying an activation barrier of Δ≠GSL=25.6 kcal mol-1. On arylated note: A novel, regio- and diastereoselective and enantiospecific direct C-H arylation reaction has been developed whereby enantiopure arylated pyrrolidines are synthesized in a single operation under metal- and oxidant-free conditions, starting from commercially available materials. The mechanistic pathway that results in high stereoselectivity is studied by using DFT.
- Haldar, Surajit,Roy, Subhra Kanti,Maity, Bholanath,Koley, Debasis,Jana, Chandan K.
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Read Online
- Ethyl 2-cyano-2-(4-nitrophenylsulfonyloxyimino)acetate-mediated lossen rearrangement: Single-pot racemization-free synthesis of hydroxamic acids and ureas from carboxylic acids
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Ethyl 2-cyano-2-(4-nitrophenylsulfonyloxyimino)acetate (4-NBsOXY) mediated Lossen rearrangement and its application for the synthesis of ureas is demonstrated. Required hydroxamic acids for the Lossen rearrangements were synthesized from carboxylic acids using the same reagent. Finally, reaction of an amine with the produced isocyanate resulted in urea. Good yields without racemization were achieved under milder and simpler reaction conditions. Reactions are compatible with common N-protecting groups, such as Boc, Fmoc, Cbz, and benzyl, as well as various OH protecting groups, such as tBu and Bzl. Conversion from carboxylic acid to urea is achieved in one pot. Most importantly, byproducts Oxyma [ethyl 2-cyano-2-(hydroxyimino)acetate] and 4-nitrobenzenesulfonic acid can be recovered easily and can be recycled to prepare the reagent. Thus, the method is environmentally friendly and cost-effective.
- Thalluri, Kishore,Manne, Srinivasa Rao,Dev, Dharm,Mandal, Bhubaneswar
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p. 3765 - 3775
(2014/05/20)
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- A facile synthesis of N-carbamoylamino acids
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N-Carbamoylamino acids were obtained through the alkylation of monosubstituted parabanic acids followed by hydrolysis of the intermediate products. This new methodology furnishes structurally and functionally diverse N-carbamoylamino acids in high preparative yields and excellent purity. Georg Thieme Verlag Stuttgart.
- Bogolubsky, Andrey V.,Ryabukhin, Sergey V.,Pakhomov, Gennadiy G.,Ostapchuk, Eugeniy N.,Shivanyuk, Alexander N.,Tolmachev, Andrey A.
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experimental part
p. 2279 - 2282
(2009/05/30)
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- Novel malonamide derivatives as potent κ opioid receptor agonists
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A novel series of malonamide derivatives was synthesized. These amides were shown to be potent and selective κ opioid receptor agonists.
- Chu, Guo-Hua,Gu, Minghua,Cassel, Joel A.,Belanger, Serge,Graczyk, Thomas M.,DeHaven, Robert N.,Conway-James, Nathalie,Koblish, Michael,Little, Patrick J.,DeHaven-Hudkins, Diane L.,Dolle, Roland E.
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p. 1951 - 1955
(2008/02/02)
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- Amide derivatives and methods of their use
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Amide derivatives of the general formulae Ia and Ib: are disclosed. Pharmaceutical compositions containing these compounds, and methods for their use, inter alia, for treating and/or preventing gastrointestinal disorders, pain, and pruritus are also disclosed.
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Page/Page column 38
(2008/06/13)
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- Carboxamide derivatives and their use in the treatment of thromboembolic diseases and tumours
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Compounds of the formula (I), in which the variables have the following meaning, D is phenyl or pyridyl, each of which is unsubstituted or monosubstituted or polysubstituted by Hal, A, OR2, N(R2)2, NO2, CN, COOR
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- A large gem-dimethyl effect in the cyclization of ω-phenylhydantoic acids: Computational modeling of the gem-dimethyl effect on the acid- or base-catalyzed cyclization of hydantoic acids and esters
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The rates of the cyclization of methyl-substituted 5-phenylhydantoic acids were measured in acid solutions. A particularly strong gem-dimethyl effect (GDME) was observed with the N-methyl compounds amounting to an acceleration of six powers of ten for the 2,2,3-trimethyl derivative. The variations in the free energies of activation for the cyclization of hydantoic acids and esters were modeled by the strain energies of the tetrahedral intermediates and of the reactants calculated by the MM3 force field. The neutral tetrahedral intermediate T0 was used for reaction series involving acid catalysis and the negatively charged intermediate T- for base catalysis. Very good agreement with the experimental GDME was obtained for the acid-catalyzed cyclizations of the complete series of the N-methyl-substituted substrates, showing that the accelerations result from a greater strain increase in the reactants. The results with T- are closely parallel, indicating that the loss of GDME observed under base catalysis with 2,2,3-trimethylhydantoate esters is not due to intramolecular strain in T-. A linear correlation (slope 1.22, r=0.934) is obtained for a plot of the free energy variations against strain energies for the reaction series of 5-phenylhydantoic acids when the data for the strongly deviating parent acid is excluded. Excellent LFERs are obtained between the reaction series of esters and acids. The observed large rate enhancements induced by N-substituents explain the switches to cyclization routes in synthetic reactions. Copyright
- Ivanov,Pojarlieff,Blagoeva,Jaime,Angelova,Koedjikov
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p. 423 - 430
(2007/10/03)
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- 2-Polystyrylsulfonyl ethanol supports for the solid-phase syntheses of hydantoins and ureas
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Reaction of sodium polystyrylsulfinate 1 with 2-chloroethanol gave the 2-arylsulfonyl ethanol resin 2, which was converted to the polymer-supported amine 5. Amine 5 was coupled with an isocyanate or an isothiocyanate to give the polymer-supported urea der
- Huang, Wenqiang,Cheng, Shaoling,Sun, Weimin
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p. 1973 - 1974
(2007/10/03)
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- PARABANIC ACID DERIVATIVES AND PHARMACEUTICAL COMPOSITIONS THEREOF
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Parabanic acid compound of the formula (I): wherein R is hydrogen or a lower alkyl group, X is hydrogen, an alkyl group, a cycloalkyl group, a lower alkylcycloalkyl group, a phenyl group or a phenalkyl group, and n represents an integer of 1 to 4, exhibit
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- SYNTHESIS OF UREIDOCARBOXYLIC ACIDS AND HYDANTOINS BY REACTION OF AMINOCARBOXYLIC ACIDS OR THEIR ESTERS WITH TRICHLOROACETAMIDES.
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The reactivity of N-aryltrichloroacetamides as in situ generating isocyanates is used in the reaction with aminocarboxylic acids and their esters.N-aryl ureidocarboxylic acids, their esters or hydantoins are the obtained compounds.
- Atanassova, I. A.,Petrov, J. S.,Balabanova, A. N.,Mollov, N. M.
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p. 2947 - 2954
(2007/10/02)
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