Stephanotic acid, a novel cyclic pentapeptide from the stem of Stephanotis floribunda

The stem of Stephanotis floribunda afforded a new cyclic pentapeptide stephanotic acid (1), possessing a novel 6-(leucin-3'-yl) tryptophan skeleton. The structure of 1 was assigned on the basis of extensive NMR experiments and a chemical reaction and shown to be closely related to the bicyclic octapeptide moroidin (3), a toxin from Laportea moroides.