Imidazolium salt-supported Mukaiyama reagent: an efficient condensation reagent for amide bond formation
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Abstract:
A novel imidazolium salt-supported Mukaiyama reagent has been synthesized and utilized as a coupling agent for the synthesis of amides.Keywords:
Amide
Peptide bond
Condensation reaction
Salt lake
To independently assess the contribution of ground-state pseudoallylic strain to the enormous rates of amide bond cleavage in tertiary amide derivatives of Kemp's triacid, we have studied four amide derivatives of (1α-3α-5β)-5-tert-butyl-1,3-cyclohexanedicarboxylic acid. Our results demonstrate that absent pseudoallylic strain, a 1,3-diaxial interaction of an amide with a carboxylic acid leads to only a 2400-fold increase in the rate of amide bond cleavage as compared with the rate of hydrolysis of an unactivated peptide bond.
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Peptide bond
Cleavage (geology)
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An unusual hydrolysis/solvolysis of the classical acyclic amide bond, derived from N-troponylaminoethylglycine (Traeg) and α-amino acids, is described under mild acidic conditions. The reactivity of this amide bond is possibly owed to the protonation of the troponyl carbonyl functional group. The results suggest that the Traeg amino acid is a potential candidate for protecting and caging of the amine functional group of bioactive molecules via a cleavable amide bond.
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Unconstrained amides that undergo fast hydrolysis under mild conditions are valuable sources of information about how amide bonds may be activated in enzymatic transformations. We report a compound possessing an unconstrained amide bond surrounded by an amino and a carboxyl group, each mounted in close proximity on a bicyclic scaffold. Fast amide hydrolysis of this model compound was found to depend on the presence of both the amino and carboxyl functions, and to involve a proton transfer in the rate-limiting step. Possible mechanisms for the hydrolytic cleavage and their relevance to peptide bond cleavage catalyzed by natural enzymes are discussed. Experimental observations suggest that the most probable mechanisms of the model compound hydrolysis might include a twisted amide intermediate and a rate-determining proton transfer.
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Amide
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Limiting
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In this Microreview, we describe the recent exciting developments in the burgeoning area of amide N–C cross‐coupling enabled by amide bond twist of N ‐acyl‐glutarimides. Since the initial reports in 2015, these amides have been demonstrated to be by far the most reactive amide derivatives in the biologically‐relevant manifold of N–C activation/cross‐coupling, thus stimulating the development of more than 10 previously unknown catalytic modes of reactivity of the amide bond. The capacity of N ‐acyl‐glutarimides as privileged scaffolds to expedite acyl and decarbonylative cross‐couplings by amide N–C cleavage is discussed.
Amide
Peptide bond
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Cleavage (geology)
Bond cleavage
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Abstract Progress in the condensation of lignin is believed to interfere with delignification in alkaline pulping processes without any clear evidence, which motivated us to revisit it quantitatively. This study is the 3rd in the series which evaluates the condensation reactions of lignin in model systems of soda cooking processes using 4-(1-hydroxyethyl)-2-methoxyphenol (apocynol, Ap) and 2-methoxy-4-methylphenol (creosol, Cr). Ap was primarily converted to 2-methoxy-4-vinylphenol (vinylguaiacol, Vg) via the quinone methide intermediate to establish equilibrium before condensation reactions proceeded. Only the α -5-type condensation product between Ap and Cr (ApCr, 1-(4-hydroxy-3-methoxyphenyl)-1-(2-hydroxy-3-methoxy-5-methylphenyl)ethane) and the α - β -type condensation product between Ap and Vg or two molecules of Vg (ApVg, trans -1,3-bis(4-hydroxy-3-methoxyphenyl)but-1-ene) were identified without detecting any self-condensation products of Ap. The α - β -type condensation has not been well known and is an important finding of this study. The formation of ApVg was over 10 times faster than that of ApCr, which demonstrates that the α - β -type condensation is a major mode in soda cooking. However, because origins of α - β -type condensation substructures, such as C 6 -C 2 -type enol ethers, do not exist in native lignin, the results support our previous conclusion that the condensation reactions of lignin progress less frequently than previously believed.
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The influence of Fmoc-protected amino acid,substitution and particle size of Wang resin and stirring modes on the condensation reaction efficiency of Fmoc-protected amino acid and Wang resin were studied.It is found that the molecular size of Fmoc-protected amino acid affected the efficiency of condensation reaction,the small the amino acid is,the higher the efficiency of condensation reaction will be;when the substitution of Wang resin is higher,Fmoc-protected amino acid conjoined before hindering the later condensation reaction,so that the hindered condensation reaction efficiency decrease.
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Efficient hydrolysis of amide bonds has long been a reaction of interest for organic chemists. The rate constants of proteases are unmatched by those of any synthetic catalyst. It has been proposed that a dipeptide containing serine and histidine is an effective catalyst of amide hydrolysis, based on an apparent ability to degrade a protein. The capacity of the Ser-His dipeptide to catalyze the hydrolysis of several discrete ester and amide substrates is investigated using previously described conditions. This dipeptide does not catalyze the hydrolysis of amide or unactivated ester groups in any of the substrates under the conditions evaluated.
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Peptide bond
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