In view of developing alternatives to classical peptidesynthesis strategies that suffer from low efficacy and negative environmental impact, the reactivity of N-protected α-amino acids, amino esters, and N-ethyl-N′-(3-dimethylaminopropyl)carbodiimide was studied under liquid-assisted grinding (LAG) conditions. The optimal reaction conditions enabled the intensive and environmentally benign mechanosynthesis
TCFH–NMI: Direct Access to <i>N</i>-Acyl Imidazoliums for Challenging Amide Bond Formations
作者:Gregory L. Beutner、Ian S. Young、Merrill L. Davies、Matthew R. Hickey、Hyunsoo Park、Jason M. Stevens、Qingmei Ye
DOI:10.1021/acs.orglett.8b01591
日期:2018.7.20
Challenging couplings of hindered carboxylic acids with non-nucleophilic amines to form amide bonds can be accomplished in high yields, and in many cases, with complete retention of the adjacent stereogenic centers using the combination of N,N,N′,N′-tetramethylchloroformamidinium hexafluorophosphate (TCFH) and N-methylimidazole (NMI). This method allows for in situ generation of highly reactive acyl imidazolium
Efficient coupling of α,α-dimethyl amino acid using a new chloro imidazolidium reagent, CIP
作者:Kenichi Akaji、Naohiro Kuriyama、Yoshiaki Kiso
DOI:10.1016/s0040-4039(00)76895-x
日期:1994.5
CIP (2-chloro- 1,3-dimethylimidazolidium hexafluorophosphate) was an efficient coupling agent for Nα-protected a-aminoisobutyric acid (Aib) in the presence of an additive. The reactivity was enhanced markedly by a catalytic amount of additive in the order of HOAt∼HODhbt > DMAP> HOBt. These couplings occurred without detectable racemization.
K-Oxyma: a Strong Acylation-Promoting, 2-CTC Resin-Friendly Coupling Additive
作者:Prabhakar Cherkupally、Gerardo A. Acosta、Lidia Nieto-Rodriguez、Jan Spengler、Hortensia Rodriguez、Sherine N. Khattab、Ayman El-Faham、Marina Shamis、Yoav Luxembourg、Rafel Prohens、Ramon Subiros-Funosas、Fernando Albericio
DOI:10.1002/ejoc.201300777
日期:2013.10
Here we present a new formulation of the recently introduced OxymaPure additive for peptide bond formation, in which the N-hydroxylamine group is replaced by a potassium salt. The complete suppression of its acidity converts KOxyma into the most suitable coupling choice when peptides are assembled on highly acid-labile solid-supports. The cou
The uncommon amino-acid 2-methylalanine (α-aminoisobutyric acid, Aib) was investigated by 13C-NMR. The chemical shifts of amino- or carboxy-protected derivatives of Aib and of protected oligopeptides are discussed with respect to neighbouring groups and amino acids. The pH-dependence of the 13C-NMR spectra of Aib, Aib-Ala, Ala-Aib, Aib-Ala-Aib and Aib-Ala-Aib-Ala-Aib was studied. Using these examples