129867-29-4Relevant academic research and scientific papers
Formation of N-Acylureas During the Peptide Coupling with the Use of Unsymmetrical Carbodiimides
Izdebski, J.,Pelka, J.,Orlowska, A.
, p. 523 - 528 (2007/10/02)
A study was concucted to determine the effect of alkyl groups of N,N'-dialkylcarbodiimides on the formation of N-acylureas during the peptide coupling.The use of carbodiimides of the structure Bu-t-N=C=N-R, where R=Me, Et and Pr-i, resulted in the formation of two isomeric N-acylureas.The proportion of the two compounds in the mixture was determined by 1H NMR spectroscopy and confirmed by chromatographic isolation.It was established that it is the least hindered O-acylurea nitrogen atom that attacks intramolecularly the amino acid activated by the unsymmetrical carbodiimide to form the major rearrangement product. Key words: carbodiimide, coupling reagent, peptide synthesis
64. N-Acylureas in Peptide-Synthesis: An X-Ray Diffraction and IR-Absorption Study
Toniolo, Claudio,Valle, Giovanni,Crisma, Marco,Moretto, Vittorio,Izdebski, Jan,et al.
, p. 626 - 634 (2007/10/02)
An X-ray diffraction analysis of two N-acyl derivatives of symmetrical dialkylureas, N-α-(benzyloxycarbonyl)-L-valyl>-N,N'-diisopropylurea (1) and N-α--L-valyl>-N,N'-dicyclohexylurea (2), and one N-acyl derivative of an unsymmetrical N,N'-dialkylurea, N-α-(benzyloxycarbonyl)-L-valyl>-N'-(tert-butyl)-N-ethylurea (3), has been performed.It was established that it is the least hindered O-acylisourea N-atom that attacks intramolecularly the carbonyl group of the Nα-protected amino acid activated by the unsymmetrical carbodiimide to form the major rearrangement product.The occurrence and nature of intra- and intermolecularly H-bonded forms of the N-acylureas in the crystal state were also assessed.It was also shown that soluble N-acylureas may complete with ine intermolecular (petptide)N-H...O=C(peptide) H-bonds in CH2Cl2.
