Mechanism of enamine hydrolysis

Sollenberger, Paula Y.; Martin, Robert B.

doi:10.1021/ja00717a021

Cited by 71 publications

(28 citation statements)

References 5 publications

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“…With the acyclic analogue PhCH=C(SMe),, the exchange was only 3-fold as rapid as the hydrolysis under similar conditions, although the kinetic reversibility of the protonation in terms of k2/kPl (0.36) was greater in mostly aqueous solutions (2 Stability and reactivity The equilibrium constants K1 for protonation of the double bond refer to carbon basicity. Similar determinations of which we are aware are those with 1,l-diarylethylenes (6,11) and enarnines of propiophenone (12). The most basic is the enarnine (log K1 = 10) (12).…”

Section: Isotope Exchangesupporting

confidence: 55%

Acid-catalyzed hydrolysis of 2-methylene-1,3-dithiolane. 2. Remarkable effects of β substitution on reversibility of the carbon protonation

Okuyama¹,

Toyoda²,

Fueno³

1986

Can. J. Chem.

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This paper is dedicated to Professor Arthur N . Bourns TADASHI OKUYAMA, MASAYOSHI TOYODA, and TAKAYUKI FUENO. Can. J. Chem. 64, 11 16 (1986).Hydrolyses of Zethylidene-( l b ) , 2-isopropylidene-( l c ) , and 2-benzylidene-l,3-dithiolane ( I d ) were kinetically investigated in aqueous solution. All the individual rate constants involved in this three-step reaction were evaluated. Initial carbon protonation is only partially reversible (k2/k-1 = 1.33,0.68, and 1.02 for l b , l c , and Id, respectively) at higher pH, while the protonation becomes completely reversible below pH 2 where the thud step is rate determining. Complete H-D isotopeexchange at the P-carbon of l b and Id was observed in deuterium media before appreciable hydrolysis took place. It was demonstrated that reversion from the tetrahedral intermediate 3 to 1 occurs extensively during the reaction in the latter acidity range. Relative stabilities and reactivities of the olefinic substrates 1 are discussed. que, au cours de la rCaction, la transformation de l'intenntdiaire tCtraidrique 3 en 1 ne se produit que dans le dernier intervalle de pH. On discute des stabilitCs et des rtactivitts relatives des substrats olCfiniques 1.[Traduit par la revue]

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Section: Isotope Exchangesupporting

confidence: 55%

Acid-catalyzed hydrolysis of 2-methylene-1,3-dithiolane. 2. Remarkable effects of β substitution on reversibility of the carbon protonation

Okuyama¹,

Toyoda²,

Fueno³

1986

Can. J. Chem.

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“…Then, the leader peptide is removed by the protease ElxP producing an N-terminal enamine (dehydroalanine, Dha) present in equilibrium with the corresponding imine that can be hydrolyzed to produce dehydro-epilancin 15X. Although enamine hydrolysis is fast (Sollenberger and Martin, 1970), enzymatic assistance ( e.g. by ElxP) cannot be ruled out at present.…”

Section: Discussionmentioning

confidence: 99%

Biosynthesis of the Antimicrobial Peptide Epilancin 15X and Its N-Terminal Lactate

Velásquez

Zhang

Donk

2011

Chemistry & Biology

106

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SUMMARY Lantibiotics are ribosomally synthesized and posttranslationally modified antimicrobial peptides. The recently discovered lantibiotic epilancin 15X produced by Staphylococcus epidermidis 15X154 contains an unusual N-terminal lactate group. To understand its biosynthesis, the epilancin 15X biosynthetic gene cluster was identified. The N-terminal lactate is produced by dehydration of a Ser residue in the first position of the core peptide by ElxB, followed by proteolytic removal of the leader peptide by ElxP, and hydrolysis of the resulting new N-terminal dehydroalanine. The pyruvate group thus formed is reduced to lactate by an NADPH dependent oxidoreductase designated ElxO. The enzymatic activity of ElxB, ElxP, and ElxO were investigated in vitro or in vivo and the importance of the N-terminal modification for peptide stability against bacterial aminopeptidases was assessed.

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“…23,35,36 None of these products, however, can be assigned to the observed signal in the mass spectrum. 37 …”

Section: Papermentioning

confidence: 99%

The chemical fate of paroxetine metabolites. Dehydration of radicals derived from 4-(4-fluorophenyl)-3-(hydroxymethyl)piperidine

et al. 2013

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Quantum chemical calculations have been used to model reactions which are important for understanding the chemical fate of paroxetine-derived radicals in the environment. In order to explain the experimental observation that the loss of water occurs along the ( photo)degradation pathway, four different mechanisms of radical-induced dehydrations have been considered. The elimination of water from the Ncentered radical cation, which results in the formation of an imine intermediate, has been calculated as the most feasible process. The predicted energy barrier (ΔG # 298 = 98.5 kJ mol −1 ) is within the barrier limits set by experimental measurements. All reaction intermediates and transition state structures have been calculated using the G3(MP2)-RAD composite procedure, and solvent effects have been determined using a mixed (cluster/continuum) solvation model. Several new products, which comply with the available experimental data, have been proposed. These structures could be relevant for the chemical fate of antidepressant paroxetine, but also for biologically and environmentally related substrates.

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Mechanism of enamine hydrolysis

Abstract: The rates of hydrolysis of the morpholine, dimethylamine, piperidine, and pyrrolidine enamines of propiophenone have been investigated in the pH range -3 to 14 at 25°. Hammett

Cited by 71 publications

References 5 publications

Acid-catalyzed hydrolysis of 2-methylene-1,3-dithiolane. 2. Remarkable effects of β substitution on reversibility of the carbon protonation

Acid-catalyzed hydrolysis of 2-methylene-1,3-dithiolane. 2. Remarkable effects of β substitution on reversibility of the carbon protonation

Biosynthesis of the Antimicrobial Peptide Epilancin 15X and Its N-Terminal Lactate

The chemical fate of paroxetine metabolites. Dehydration of radicals derived from 4-(4-fluorophenyl)-3-(hydroxymethyl)piperidine

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