ISSN:
0947-3440
Schlagwort(e):
Cyclic heptapeptide, 2D-NMR, conformation of
;
Chemistry
;
Organic Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
Recently, a cyclic heptapeptide with cytostatic activity was isolated from marine sources by three different groups independently. The sequence of the isolated peptide was ambiguous, since two different isomers have been proposed: cyclo(-Asn1-Pro2-Phe3-Val4-Val5-Pro6-Val7-) (1) also called axinastatin 1 resp. pseudoaxinellin and cyclo(-Asn1#-Pro2#-Pro3# -Phe4#-Val5#-Val6#-Val7#-) (2) called malaysiatin. We synthesized both peptides 1 and 2 and compared their optical rotation, FAB-MS, 1H- and 13C-NMR data with those of the native compounds. Our results prove that peptide 1 has been assigned correctly, whereas the data of 2 differ significantly from those of the natural peptide. Peptide 1 adopts two conformations (90:10 ratio) in DMSO, interconverting slowly on the NMR time scale. According to MD simulations, using NOEs and J couplings as experimental restraints, a βVIa-turn with a cis peptide bond between Val5-Pro6 and a βI-turn in the Asn1-Val4 region are the characteristic secondary structural elements of the major conformer. Its backbone conformation is very similar to the X-ray structure of a related peptide cyclo(-Asna-Leub-Serc-Phed-Leue-Prof-Valg-) called evolidine.
Zusätzliches Material:
8 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/jlac.1995199505112
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