| Abstract
| - Three new bicyclic peptides, celogentins A (1), B (2), and C (3), have been isolated together with aknown-related peptide, moroidin (4), from the seeds of Celosia argentea, and their structuresincluding absolute stereochemistry were determined by using extensive NMR methods and chemicalmeans. Celogentins A (1), B (2), and C (3) inhibited the polymerization of tubulin, and celogentinC (3) was four times more potent than moroidin (4) in the inhibitory activity. Structure−activityrelationship study using moroidin derivatives 5−7 and analogue 8 as well as celogentins A−C(1−3) and moroidin (4) indicates that the bicyclic ring system including unusual non-peptideconnections among βs-Leu, Trp, and His residues characteristic of celogentins and moroidin, withring size and conformations suitable for interaction with tubulin would be important for theirbiological activity.
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