Stereochemistry of protected ornithine side chains of gramicidin S derivatives: X-ray crystal structure of the bis-Boc-tetra-N-methyl derivative of gramicidin S.

@article{Yamada2002StereochemistryOP,
  title={Stereochemistry of protected ornithine side chains of gramicidin S derivatives: X-ray crystal structure of the bis-Boc-tetra-N-methyl derivative of gramicidin S.},
  author={Keiichi Yamada and Masafumi Unno and Kyoko Hillman Kobayashi and Hiroyuki Oku and Hatsuo Yamamura and Shuki Araki and Hideyuki Matsumoto and Ryoichi Katakai and Masanobu Kawai},
  journal={Journal of the American Chemical Society},
  year={2002},
  volume={124 43},
  pages={
          12684-8
        }
}
An X-ray crystallographic analysis of the bis-Ndelta-Boc-tetra-Nalpha-methyl derivative of gramicidin S, cyclo(-Val-MeOrn(Boc)-Leu-d-MePhe-Pro-)2, was undertaken successfully (R-factor = 0.088). As expected, the main chain adopts an antiparallel pleated beta-sheet conformation, but the pleated sheet is slightly twisted, and the sense of twisting is opposite to that found in the reported crystal structures of the gramicidin S-urea complex and the bis-Ndelta-(trichloroacetyl) and bis-Ndelta-(m… CONTINUE READING
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