The Curtin-Hammett principle and the Winstein-Holness equation: new definition and recent extensions to classical concepts

Seeman, Jeffrey I.

doi:10.1021/ed063p42

Cited by 196 publications

(149 citation statements)

References 20 publications

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“…Hence both linear and branched allylic esters can be used as starting materials to obtain the same protected b-hydroxy aldehydes. Reaction monitoring by 1 H NMR spectroscopy indicated that the Curtin-Hammett principle [47] applied in this case. The selectivity towards the branched aldehyde product resulted from the low rate at which the thermodynamically more stable linear allylic alcohol underwent oxidation and the relatively rapid palladium(II)-catalyzed interconversion between the branched and linear allylic alcohols.…”

Section: Anti-markovnikov Oxidations In Alcohols As the Solventmentioning

confidence: 85%

Palladium‐Catalyzed anti‐Markovnikov Oxidation of Terminal Alkenes

2014

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The palladium-catalyzed oxidation of alkenes, the Wacker-Tsuji reaction, is undoubtedly a classic in organic synthesis and provides reliable access to methyl ketones from terminal alkenes under mild reaction conditions. Methods that switch the selectivity of the reaction to provide the aldehyde product are desirable because of the access they provide to a valuable functional group, however such methods are elusive. Herein we survey both the methods which have been developed recently in achieving such selectivity and discuss common features and mechanistic insight which offers promise in achieving the goal of a general method for anti-Markovnikov-selective olefin oxidations.

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Section: Anti-markovnikov Oxidations In Alcohols As the Solventmentioning

confidence: 85%

Palladium‐Catalyzed anti‐Markovnikov Oxidation of Terminal Alkenes

2014

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“…Therefore, use of high temperature and long reaction time favor the formation of the thermodynamic product. Further details on thermodynamic and kinetic control and the Curtin-Hammet principle is available elsewhere [63][64][65].…”

Section: Reversible Competitive First-order Reactionsmentioning

confidence: 99%

Practical Chemical Kinetics in Solution

Seoud

Baader

Bastos

2016

Encyclopedia of Physical Organic Chemistry, 5 Volume Set

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“…The pseudoaxial and pseudoequatorial conformations of penicillin G bind with very similar geometries, but the energies of the two complexes differ by 2.73 kcal/mol. Since these are conformational isomers, the Curtin-Hammett principle applies (57), and only this energy difference is needed. It follows that the pseudoaxial conformation ofpenicillin G is bound preferentially to 17.…”

Section: Binding Of Penicillins To the Pbp Model 17mentioning

confidence: 99%

Conformation–activity relationships and the mechanism of action of penicillin

Wolfe¹,

Yang²,

Khalil³

1988

Can. J. Chem.

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. Can. J. Chem. 66, 2733Chem. 66, (1988. Using the MMPEN parameters of Allinger's MMP2(85) force field, a conformational analysis has been performed on four biologically active penicillins: D-ampicillin, L-a-phenoxyethylpenicillin, penicillin G, and penicillin V, and on five biologically inactive or much less active penicillins: L-ampicillin, D-a-phenoxyethylpenicillin, N-methylpenicillin G, 6a-methylpenicillin G, and bisnorpenicillin G. Antibacterial activity is found to be associated with the existence of a global minimum having a compact structure, whose convex face is accessible to a penicillin binding protein (PBP), with the C3-carboxyl group and the side-chain N-H exposed on this face. Using the MMPEP parameters of MMP2(85), a conformational analysis has been performed on phenylacetyl-D-Ala-D-Ala-0-, a peptide model of the normal substrate of a PBP. Labischinski's global minimum has been reproduced, along with structures that correspond to Tipper and Strominger's proposal that the N4-C7 bond of a penicillin corresponds to the Ala-Ala peptide bond, and to Hasan's proposal that the N4-C5 bond of penicillin corresponds to the peptide bond. For both models, conformations of the peptide related to the pseudoaxial and pseudoequatorial conformations of the thiazolidine ring of penicillin G have been examined. It is concluded that penicillin is not a structural analog of the global minimum of the peptide; however, comparisons based on unbound conformations of PBP substrates are unable to determine which model is more appropriate, or which conformation of penicillin G is the biologically significant one. Using the ECEPPIMMPEP strategy, a model of the active site of a PBP has been obtained, following a search of 200,000 structures of the peptide Ac-NH-Val-Gly-Ser-Val-Thr-Lys-NH-Me. This peptide contains the sequence at the active site of a PBP of Streptomyces R61, for which it is also known that the C3-carboxyl group of penicillin binds to the €-amino group of lysine, and the p-lactam reacts chemically with the serine OH. The lysine and serine side chains and the C-terminal carbonyl group are found to occupy the concave face of the active site model.A strategy for the docking of penicillins or peptides to this model, with full minimization of the conformational energies of the complexes, has been devised. All active penicillins bind through strong hydrogen bonds to the C3-carboxyl group and the side-chain N-H, and with a four-centered relationship between the O-H of serine and the (0)C-N of the p-lactam ring. The geometrical parameters of this relationship are reminiscent of those found in the gasphase transition state of neutral hydration of a carbonyl group. When the energies of formation and geometries of the pseudoaxial and pseudoequatorial penicillin G complexes areexamined, there is now a clear preference forthe binding of the pseudoarial conformation, which is the global minimum of the uncomplexed penicillin in this case. A similar examination of the peptide complexes reveals that only the conformation of t...

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The Curtin-Hammett principle and the Winstein-Holness equation: new definition and recent extensions to classical concepts

Cited by 196 publications

References 20 publications

Palladium‐Catalyzed anti‐Markovnikov Oxidation of Terminal Alkenes

Palladium‐Catalyzed anti‐Markovnikov Oxidation of Terminal Alkenes

Practical Chemical Kinetics in Solution

Conformation–activity relationships and the mechanism of action of penicillin

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