Stereochemistry of protected ornithine side chains in gramicidin S derivatives and their resistance to N-methylation.

Autor: Kawai, Masao, Yamamoto, Tatsuo, Yamada, Keiichi, Yamaguchi, Masashi, Kurobe, Shigehiro, Yamamura, Hatsuo, Araki, Shuki, Butsugan, Yasuo, Kobayashi, Kyoko, Katakai, Ryoichi, Saito, Kazuki, Nakajima, Terumi
Zdroj: Letters in Peptide Science; Jan1998, Vol. 5 Issue 1, p5-12, 8p
Abstrakt: Derivatives of gramicidin S (GS) and its mono- and di- d-cyclohexylalanine d-Cha) analogs possessing various protecting groups on Orn side chains were prepared.H NMR spectra of the unsymmetrically protected analogs [Orn(X), Orn(X), d-Cha]GS were similar to the composites of the spectra of the symmetrical derivatives [Orn(X), d-Cha]GS and [Orn(X)]Gs, revealing the proximity of the protecting groups of NH of Orn residues at the 2 and 2 positions to the side chains of d-Phe (or d-Cha) residues at the 4 and 4 positions, respectively. The results indicated the presence of H-bonds between the NH of Orn and the carbonyl of d-Phe residues in the i→i+2 sense and not in i→i-3, which was also supported by the ROESY analysis. The substantially strong H-bonds can explain the observed resistance of the urethane NH of the Orn side chains in the GS derivatives to the N-methylation with CHI−AgO in DMF. [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index
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