- Fragmentation-Rearrangement of Peptide Backbones Mediated by the Air Pollutant NO2.
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The fragmentation-rearrangement of peptide backbones mediated by nitrogen dioxide, NO2., was explored using di-, tri-, and tetrapeptides 8-18 as model systems. The reaction, which is initiated through nonradical N-nitrosation of the peptide bond, shortens the peptide chain by the expulsion of one amino acid moiety with simultaneous fusion of the remaining molecular termini through formation of a new peptide bond. The relative rate of the fragmentation-rearrangement depends on the nature of the amino acids and decreases with increasing steric bulk at the α carbon in the order Gly>Ala>Val. Peptides that possessed consecutive aromatic side chains only gave products that resulted from nitrosation of the sterically less congested N-terminal amide. Such backbone fragmentation-rearrangement occurs under physiologically relevant conditions and could be an important reaction pathway for peptides, in which sections without readily oxidizable side chains are exposed to the air pollutant NO2.. In addition to NO2.-induced radical oxidation processes, this outcome shows that ionic reaction pathways, in particular nitrosation, should be factored in when assessing NO2. reactivity in biological systems.
- Gamon, Luke F.,Nathanael, Joses G.,Taggert, Bethany I.,Henry, Fraser A.,Bogena, Jana,Wille, Uta
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- Preparation and biological evaluation of soluble tetrapeptide epoxyketone proteasome inhibitors
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A series of novel tetrapeptidyl epoxyketone inhibitors of 20S proteasome was designed and synthesized. To fully understand the SAR, various groups at R1, R2, R3, R4 and R5 positions, including aromatic and aliphatic substituents were designed, synthesized and biologically assayed. Based on the enzymatic results, seven compounds were selected to evaluate their cellular activities and soluble compound 36 showed strong potency against human multiple myeloma (MM) cell lines. Microsomal stability results indicated that compound 36 was more stable in mice, rat and human microsomes than marketed carfilzomib. The in vivo activities of this compound were evaluated with the xenograft mice models of MM cell lines ARH77 and RPMI-8226 with luciferase expression and the T/C value of the two models were 49.5% and 37.6%, respectively. To evaluate the potential cardiovascular toxicity, inhibition of hERG ion channel in HEK293 cells by compound 36 and carfilzomib was carried out. The results indicated that 36 had no binding affinity for the hERG ion channel while carfilzomib could bind it with IC50 of 92.1 μM.
- Lei, Meng,Zhang, Haoyang,Miao, Hang,Du, Xiao,Zhou, Hui,Wang, Jia,Wang, Xueyuan,Feng, Huayun,Shi, Jingmiao,Liu, Zhaogang,Shen, Jian,Zhu, Yongqiang
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p. 4151 - 4162
(2019/08/07)
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- Pd-Catalyzed Site-Selective C(sp2)-H Olefination and Alkynylation of Phenylalanine Residues in Peptides
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Pd-catalyzed site-selective C(sp2)-H olefination and alkynylation of phenylalanine residues in peptides are described. The amino acids within the peptides are used as native bidentate directing groups to facilitate C-H functionalization. This p
- Zheng, Yong,Song, Weibin
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- Diphenylsilane as a coupling reagent for amide bond formation
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A simple procedure for amide bond formation using diphenylsilane as a coupling reagent is described. This methodology enables the direct coupling of carboxylic acids with primary and secondary amines, releasing only hydrogen and a siloxane as by-products. Only one equivalent of each partner is needed, providing a more sustainable amidation method producing minimal wastes. This methodology was also extended to the synthesis of peptides and lactams by addition of Hünig's base (DIPEA) and 4-dimethylaminopyridine (DMAP).
- Sayes, Morgane,Charette, André B.
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p. 5060 - 5064
(2017/11/09)
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