A Novel Generation of Coupling Reagents. Enantiodifferentiating Coupling Reagents Prepared in Situ from 2-Chloro-4,6-dimethoxy-1,3,5-triazine (CDMT) and Chiral Tertiary Amines
作者:Zbigniew J. Kamiński、Beata Kolesińska、Janina E. Kamińska、Józef Góra
DOI:10.1021/jo0101499
日期:2001.9.1
enantiomeric enrichment depend on the structures of the amine and carboxylic acid. Calculated Kagan enantioselectivity parameters (s) are in the range 1.6-195. Chiral triazinylammonium chlorides formed in situ from CDMT and chiral tertiary amines are postulated as reactive intermediates involved in the process of enantioselective activation of N-protected amino acids.
Amino-acids and peptides. Part XXVIII. Determination of racemization in peptide synthesis by nuclear magnetic resonance spectroscopy
作者:Boris Weinstein、Arthur E. Pritchard
DOI:10.1039/p19720001015
日期:——
Diastereoisomeric aromatic alanyl peptides possess different n.m.r. spectra owing to a diamagnetic shielding phenomenon. Observation of the shifted methyl resonance is an excellent procedure for the study of racemization in peptidesynthesis. Eight alanyl dipeptides are available as models for the evaluation and testing of any N-acyl protecting group or coupling agent. The method is general, convenient
Four kinds of stereoisomeric Z-Ala-Ala-OMe and eight kinds of stereoisomeric Z-Ala-Ala-Ala-OMe were tested as substrates for human spleen fibrinolytic proteinase (SFP) in comparison with porcine pancreatic elastase. Both enzymes exhibited esterase activity towards not only Z-L-Ala-L-Ala-L-Ala-OMe (VI) but also Z-D-Ala-L-Ala-L-Ala-OMe (VII). The rate of esterolysis of VI by elastase was only about twice the rate of esterolysis by SFP although the rate of amidolysis of Suc-L-Ala-L-Ala-L-Ala-pNA (XVI) by elastase was tenfold faster than that by SFP.
A micro-flow rapid dual activation approach for urethane-protected α-amino acid <i>N</i>-carboxyanhydride synthesis
作者:Ren Okabe、Naoto Sugisawa、Shinichiro Fuse
DOI:10.1039/d2ob00167e
日期:——
the rapid dual activation (10 s, 20 °C) of a combination of an α-aminoacidN-carboxyanhydride and alkyl chloroformate in the synthesis of a urethane-protected α-aminoacidN-carboxyanhydride in a micro-flow reactor. The key to success was the combined use of two amines that activated both substrates with proper timing. Three amines, i-Pr2NEt, Me2NBn, or N-ethylmorpholine, were used with pyridine in