Organizing Principle of Complex Reactions and Theory of Coarctate Transition States

Herges, Rainer

doi:10.1002/anie.199402551

Cited by 105 publications

(102 citation statements)

References 174 publications

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“…[123] The carbene rearrangement is believed to proceed through a coarctate transition state (TS) that requires strict orbital alignment of the divalent carbon with the cyclopropane ring. [124] A bilateral symmetry and an endocyclic configuration are requiredϪboth of which are exemplified by carbene 28. [125] Scheme 7.…”

Section: 4-ch Insertionmentioning

confidence: 99%

Constrained Carbenes

Rosenberg

Brinker

2006

Eur J Org Chem

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Carbenes traditionally have been used for cyclopropane synthesis but little else, since their reactions are difficult to control. However, the burgeoning discipline of supramolecular carbene chemistry—reactions in which highly reactive, divalent carbon intermediates are generated within the confines of host compounds—is making steady progress towards solving this problem. Various carbenes generated within cyclodextrins, hemicarcerands, and zeolites demonstrate increased selectivities and lifetimes since their usual decay pathways are blocked. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

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Section: 4-ch Insertionmentioning

confidence: 99%

Constrained Carbenes

Rosenberg

Brinker

2006

Eur J Org Chem

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“…This type of mapping was inspired by the fact that many enzymes catalyze a reaction by stabilizing its transition state and the work on reaction classification systems, in particular Fujita's imaginary transition structures (ITS) approach [33], in which cycles also play a central role. All common homo-and ambivalent reactions, which account for over 90% of all known reactions [59], can be described by a monocyclic ITS [22]. The rest of the reactions are usually composites of successive mono-cyclic reactions in sequence (rarely more than two [60]) with unstable intermediates like carbene or nitrene.…”

Section: Artificial Biochemistry: Ribozyme Catalysismentioning

confidence: 99%

Evolution of metabolic networks: a computational frame-work

et al. 2010

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Background: The metabolic architectures of extant organisms share many key pathways such as the citric acid cycle, glycolysis, or the biosynthesis of most amino acids. Several competing hypotheses for the evolutionary mechanisms that shape metabolic networks have been discussed in the literature, each of which finds support from comparative analysis of extant genomes. Alternatively, the principles of metabolic evolution can be studied by direct computer simulation. This requires, however, an explicit implementation of all pertinent components: a universe of chemical reaction upon which the metabolism is built, an explicit representation of the enzymes that implement the metabolism, of a genetic system that encodes these enzymes, and of a fitness function that can be selected for. Results: We describe here a simulation environment that implements all these components in a simplified ways so that large-scale evolutionary studies are feasible. We employ an artificial chemistry that views chemical reactions as graph rewriting operations and utilizes a toy-version of quantum chemistry to derive thermodynamic parameters. Minimalist organisms with simple string-encoded genomes produce model ribozymes whose catalytic activity is determined by an ad hoc mapping between their secondary structure and the transition state graphs that they stabilize. Fitness is computed utilizing the ideas of metabolic flux analysis. We present an implementation of the complete system and first simulation results. Conclusions: The simulation system presented here allows coherent investigations into the evolutionary mechanisms of the first steps of metabolic evolution using a self-consistent toy universe.

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“…In contrast, an acyclic but contiguous delocalised system (constricted or coarctate cycle) is characteristic of a coarctate reaction. Herges [7] has thus defined such coarctate reactions as reactions that proceed through the breaking and making of two bonds at one or more atoms at a time. Like the pericyclic reactions, they form an independent and coherent class of concerted reactions.…”

Section: Introductionmentioning

confidence: 99%

“…Herges [7] has characterised a special class of concerted reactions: the coarctate reactions. Pericyclic reactions were defined by Woodward and Hoffmann [8] as "reactions in which all first-order changes in bonding relationships take place in concert on a closed curve": that is, the bonds are made and broken in a cyclic array.…”

Section: Introductionmentioning

confidence: 99%

A DFT Study of the Concerted Cyclisation of 3‐Azidopropenal to Isoxazole:Is it a Pseudopericyclic Reaction According to Its Magnetic Properties?

2005

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Keywords: Ab initio calculations / Aromaticity / Magnetic properties / Pericyclic/pseudopericyclic reactions / Coarctate/ pseudocoarctate reactionsA comprehensive B3LYP/6-31+G(2d,p) study of the nature of the concerted cyclisation of 3-azidopropenal to isoxazole was conducted. For this purpose, the complete pathway was determined and changes in different magnetic properties [magnetic susceptibility (χ), magnetic susceptibility anisotropy (χ anis ) and the nucleus-independent chemical shifts (NICS)] were monitored along the reaction profile with a view to esti-

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Organizing Principle of Complex Reactions and Theory of Coarctate Transition States

Cited by 105 publications

References 174 publications

Constrained Carbenes

Constrained Carbenes

Evolution of metabolic networks: a computational frame-work

A DFT Study of the Concerted Cyclisation of 3‐Azidopropenal to Isoxazole:Is it a Pseudopericyclic Reaction According to Its Magnetic Properties?

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