Stereochemistry of protected ornithine side chains ingramicidin S derivatives and their resistance to N-methylation

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• 作者：Kawai ; Masao ; Yamamoto ; Tatsuo ; Yamada ; Keiichi ; Yamaguchi ; Masashi ; Kurobe ; Shigehiro ; Yamamura ; Hatsuo ; Araki ; Shuki ; Butsugan ; Yasuo ; Kobayashi ; Kyoko ; Katakai ; Ryoichi ; Saito ; Kazuki ; Nakajima ; Terumi
• 刊名：Letters in Peptide Science
• 出版年：1998
• 出版时间：1998
• 年：1998
• 卷：5
• 期：1
• 页码：5-12
• 全文大小：105 KB

文摘

Derivatives of gramicidin S (GS) and its mono- anddi-d-cyclohexylalanine (d-Cha) analogs possessing various protecting groupson Orn side chains were prepared. $^1$H NMR spectra of theunsymmetrically protected analogs[Orn(X)$^2$,Orn(X′)$^2\prime$,d-Cha$^4$]GS were similar to the composites of the spectra of the symmetricalderivatives [Orn(X)$^2,2\prime$,d-Cha$^4,4\prime$]GSand [Orn(X′)$^2,2\prime$]GS, revealing the proximity ofthe protecting groups of N$^\delta$H of Orn residues at the 2and 2$^\prime$ positions to the side chains of d-Phe (or d-Cha)residues at the 4 and 4$^\prime$ positions, respectively. Theresults indicated the presence of H-bonds between theN$^\delta$H of Orn and the carbonyl of d-Phe residues in the i→ i + 2 sense and not in i → i – 3, which was also supportedby the ROESY analysis. The substantially strong H-bonds can explain theobserved resistance of the urethane NH of the Orn side chains in the GSderivatives to the N-methylation withCH$\_3$I–Ag$\_2$O in DMF.