The crystal state conformation of Aib-rich segments of peptaibol antibiotics

✍ Scribed by André Aubry; Daniel Bayeul; Hans Brückner; Norbert Schiemann; Ettore Benedetti

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 263 KB
• Volume: 4
• Category: Article
• ISSN: 1075-2617
• DOI: 10.1002/(sici)1099-1387(199812)4:8<502::aid-psc171>3.0.co;2-n

✦ Synopsis

Ac-(Aib-Ala) 3 -OH (a protected segment of the peptaibols gliodeliquescin and paracelsin), Z-Leu-Aib-Val-Aib-Gly-OtBu (a segment of [Leu] 7 -gliodeliquescin), Z-Val-Aib-Aib-Gln-OtBu (a common segment of alamethicin, paracelsin, and hypelcin), and Ac-Aib-Pro-(Aib-Ala) 2 -OMe and Z-Aib-Pro-(Aib-Ala) 2 -OMe, which represent differently N h -protected 1-6 segments of alamethicin and hypelcin, have been synthesized by solution methods. The crystal-state conformations of these five Aib-containing peptides have been determined by X-ray diffraction analysis. We have confirmed that the 3 10 -helical structure is preferentially adopted by Aib-rich short peptides. An experimentally unambiguous proof for the 3 10 h-helix conversion has been provided by the two differently N-blocked -Aib-Pro-(Aib-Ala) 2 -OMe hexapeptides. The i-bend ribbon conformation, commonly observed in the (Aib-Pro) n sequential oligopeptides, is not found in the -Aib-Pro-Aib-Ala-Aib-Ala-sequence. As expected on the basis of the L-configuration of the C h -monoalkylated residues, a right-handed helix screw sense was found in all peptides investigated.