1696-20-4Relevant articles and documents
Heterocyclic Deformations from Molecular Enlargement
Lambert, Joseph B.,Wharry, Stephen M.
, p. 3890 - 3893 (1982)
The ease of distortion of saturated nitrogen heterocycles has been examined by progressively increasing the bulk of the substituent at nitrogen.The heterocycles included the pharmacophoric piperidine and morpholine six-membered rings, as well as the five-membered oxazolidine ring.Response to increased bulk of substitution was intended to be a crude model for distortions within the drug-receptor complex.Substitution at nitrogen included methyl, (1-adamantyl)methyl, and 6-substituted β-cyclodextrin within a tetrahedral series, and acetyl and (1-adamantyl)carbonyl within a trigonal series.With methyl and acetyl serving as standards for the undistorted rings, we have found that the NCH2CH2X dihedral angle within all three heterocycles is decreased anly by about 1 deg on introduction of adamantyl groups.In agreement with this flattening distortion, the barrier to ring reversal of the piperidine is decreased by 1.4 kcal/mol on replacement of N-methyl by N-adamantylmethyl.The β-cyclodextrin ring imposes a much more severe distortion, as this same dihedral angle in the piperidine and morpholine rings decreases 5-6 deg.The barrier to rotation about the amide bond decreases 5-6 kcal/mol in all three heterocycles on going from acetyl to adamantylcarbonyl.These studies show that the response of these heterocycles to incresed steric bulk of N substitution is a flatter and hence more flexible ring.
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Horten et al.
, p. 2425 (1948)
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Electrophilic Sulfonium-Promoted Peptide and Protein Amidation in Aqueous Media
Wan, Chuan,Feng, Yuan,Hou, Zhanfeng,Lian, Chenshan,Zhang, Liang,An, Yuhao,Sun, Jinming,Yang, Dongyan,Jiang, Chenran,Yin, Feng,Wang, Rui,Li, Zigang
supporting information, p. 581 - 586 (2022/01/20)
A novel amidation strategy using electrophilic sulfonium, which is soluble and stable in aqueous conditions, was developed. The sulfoniums could activate thioacid and carboxyl acid to efficiently react with amines to afford amides. This method enables applications in amidation in both aqueous media and solid-phase peptide synthesis, peptide/protein modifications, and reactive lysines of a proteome at pH 10 with activity-based protein profiling. A peptide ligand-directed labeling of the USP7-UBL2 domain was also performed using this method.
A CO2-Catalyzed Transamidation Reaction
Yang, Yang,Liu, Jian,Kamounah, Fadhil S.,Ciancaleoni, Gianluca,Lee, Ji-Woong
, p. 16867 - 16881 (2021/11/18)
Transamidation reactions are often mediated by reactive substrates in the presence of overstoichiometric activating reagents and/or transition metal catalysts. Here we report the use of CO2as a traceless catalyst: in the presence of catalytic amounts of CO2, transamidation reactions were accelerated with primary, secondary, and tertiary amide donors. Various amine nucleophiles including amino acid derivatives were tolerated, showcasing the utility of transamidation in peptide modification and polymer degradation (e.g., Nylon-6,6). In particular,N,O-dimethylhydroxyl amides (Weinreb amides) displayed a distinct reactivity in the CO2-catalyzed transamidation versus a N2atmosphere. Comparative Hammett studies and kinetic analysis were conducted to elucidate the catalytic activation mechanism of molecular CO2, which was supported by DFT calculations. We attributed the positive effect of CO2in the transamidation reaction to the stabilization of tetrahedral intermediates by covalent binding to the electrophilic CO2
IrIII-Catalyzed direct syntheses of amides and esters using nitriles as acid equivalents: A photochemical pathway
Talukdar, Ranadeep
supporting information, p. 5303 - 5308 (2020/04/17)
An unprecedented IrIII[df(CF3)ppy]2(dtbbpy)PF6-catalyzed simple photochemical process for direct addition of amines and alcohols to the relatively less reactive nitrile triple bond is described herein. Various amides and esters are synthesized as the reaction products, with nitriles being the acid equivalents. A mini-library of different types of amides and esters is made using this mild and efficient process, which uses only 1 mol% of photocatalyst under visible light irradiation (λ = 445 nm). The reaction strategy is also efficient for gram-scale synthesis.
