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Volumn 47, Issue 13, 2008, Pages 2475-2479

Exploiting neighboring-group interactions for the self-selection of a catalytic unit

Author keywords

Catalysis; Combinatorial chemistry; Supramolecular chemistry; Thermodynamics; Transition states

Indexed keywords

ESTERS; ORGANIC COMPOUNDS; THERMODYNAMICS;

EID: 46149100860     PISSN: 14337851     EISSN: None     Source Type: Journal    
DOI: 10.1002/anie.200703857     Document Type: Article
Times cited : (42)

References (56)
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    • For theoretical discussions on the amplification in dynamic libraries: a
    • For theoretical discussions on the amplification in dynamic libraries: a) J. S. Moore, N. W. Zimmerman, Org. Lett. 2000, 2, 915-918;
    • (2000) Org. Lett , vol.2 , pp. 915-918
    • Moore, J.S.1    Zimmerman, N.W.2
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    • Angew. Chem. Int. Ed. 2003, 42, 3821-3825;
    • (2003) Angew. Chem. Int. Ed , vol.42 , pp. 3821-3825
  • 9
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    • For representative examples see: a
    • For representative examples see: a) J.-M. Lehn, A. Eliseev, Science 2001, 291, 2331-2332;
    • (2001) Science , vol.291 , pp. 2331-2332
    • Lehn, J.-M.1    Eliseev, A.2
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    • Angew. Chem. Int. Ed. 2005, 44, 5736-5739;
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    • Angew. Chem. Int. Ed. 2005, 44, 7935-7938.
    • (2005) Angew. Chem. Int. Ed , vol.44 , pp. 7935-7938
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    • Angew. Chem. Int. Ed. 2003, 42, 1270-1273;
    • (2003) Angew. Chem. Int. Ed , vol.42 , pp. 1270-1273
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    • (2003) Angew. Chem. Int. Ed , vol.42 , pp. 2171-2173
  • 36
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    • In principle, the amplification may also be affected by the occurrence of repulsive or intermolecular interactions
    • In principle, the amplification may also be affected by the occurrence of repulsive or intermolecular interactions.
  • 37
    • 53549084404 scopus 로고    scopus 로고
    • 13C HSQC spectroscopy can also be used to follow the kinetics of hydrazone exchange. This allows a full evaluation of both the kinetic and thermodynamic parameters of a dynamic, multicomponent library and, in addition, eliminates any problem in peak assignment. This methodology will be published in due course.
    • 13C HSQC spectroscopy can also be used to follow the kinetics of hydrazone exchange. This allows a full evaluation of both the kinetic and thermodynamic parameters of a dynamic, multicomponent library and, in addition, eliminates any problem in peak assignment. This methodology will be published in due course.
  • 38
    • 53549129315 scopus 로고    scopus 로고
    • The lowest concentrations are in the order of 0.25 mM. T he errors in the amplification factors are estimated to be around 15%.
    • The lowest concentrations are in the order of 0.25 mM. T he errors in the amplification factors are estimated to be around 15%.
  • 39
    • 53549120701 scopus 로고    scopus 로고
    • The amplification in this kind of systems depends on the number of equivalents of hydrazides added,[12] which might explain the slightly different amplification factors between the two methods of screening
    • [12] which might explain the slightly different amplification factors between the two methods of screening.
  • 40
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    • [12] maximum amplification is observed under very dilute conditions (0.2 mM), as under these conditions, competing intermolecular interactions are minimal. However, at such concentrations the exchange kinetics are very slow. Therefore, for practical reasons we decided to work at an intermediate 5 mM concentration of scaffold. From our previous studies, this implies a drop in amplification from the maximum value of 3.1 to the observed intermediate value of 1.8.
    • [12] maximum amplification is observed under very dilute conditions (0.2 mM), as under these conditions, competing intermolecular interactions are minimal. However, at such concentrations the exchange kinetics are very slow. Therefore, for practical reasons we decided to work at an intermediate 5 mM concentration of scaffold. From our previous studies, this implies a drop in amplification from the maximum value of 3.1 to the observed intermediate value of 1.8.
  • 44
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    • Angew. Chem. Int. Ed. 2005, 44, 965-969.
    • (2005) Angew. Chem. Int. Ed , vol.44 , pp. 965-969
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    • The pH refers to the value of the pure aqueous component, and was not corrected for the mixture
    • The pH refers to the value of the pure aqueous component, and was not corrected for the mixture.
  • 46
    • 53549116269 scopus 로고    scopus 로고
    • In principle, the enhanced hydrolysis rate of 3B compared to 3A could also be a result of an enhanced local concentration of OH, If this would have been the case, a plot of logk obs vs pH would be nonlinear. Therefore, the hydrolysis rates of both 3A and 3B were determined at pH 7-11 see Supporting Information, The analysis showed that for pH 9-11, logkobs increases linearly with the pH with logk3B and logk3a increasing linearly with pH with the same slope. Based on these results, we conclude that the higher hydrolysis rate of 3B is indeed due to transition-state stabilization. Interestingly, for pH values below 9, the difference in hydrolysis rates between 3A and 3B vanishes, and the slope of the curve by plotting logkobs versus pH changes dramatically for 3A. We ascribe this to the protonation of the tertiary amine in
    • obs versus pH changes dramatically for 3A. We ascribe this to the protonation of the tertiary amine in both 3A and 3B which, for both structures, results in a positive charge located very close to the carboxylic ester moiety. Consequently, at more acidic pH values the "catalytic" effect of the ammonium group in 3B is taken over by the protonated tertiairy amine.
  • 49
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    • In a structurally related system, Anslyn et al. observed a 40-fold acceleration of a phosphate diester cleavage by a neighbouring guanidinium-group. See: A. M. Piatek, M. Gray, E. V. Anslyn, J. Am. Chem. Soc. 2004, 126, 9878-9879
    • In a structurally related system, Anslyn et al. observed a 40-fold acceleration of a phosphate diester cleavage by a neighbouring guanidinium-group. See: A. M. Piatek, M. Gray, E. V. Anslyn, J. Am. Chem. Soc. 2004, 126, 9878-9879.
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    • T. C. Bruice, F. C. Lightstone, Acc. Chem. Res. 1999, 32, 127-136. For the importance in a dynamic system see also ref. [10d].
    • e) T. C. Bruice, F. C. Lightstone, Acc. Chem. Res. 1999, 32, 127-136. For the importance in a dynamic system see also ref. [10d].
  • 55
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    • We have also synthesized an analogous compound containing an ethylene spacer 3B2, Regrettably it is not stable enough to carry out the hydrolysis studies: addition of base very rapidly leads to the elimination of trimethylamine
    • 2). Regrettably it is not stable enough to carry out the hydrolysis studies: addition of base very rapidly leads to the elimination of trimethylamine.
  • 56
    • 0001564594 scopus 로고    scopus 로고
    • This is in accord with what has been found by studying charge-charge interactions in flexible systems: Y. Chevalier, P. Perchec, J. Phys. Chem. 1990, 94, 1768-1774
    • This is in accord with what has been found by studying charge-charge interactions in flexible systems: Y. Chevalier, P. Perchec, J. Phys. Chem. 1990, 94, 1768-1774.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.