Clausenlanins A and B, Two Leucine-Rich Cyclic Nonapeptides from Clausena lansium

Two new cyclic nonapeptides, named clausenlanins A (1) and B (2), were isolated from the roots and rhizomes of Clausena lansium. Their structures were elucidated as cyclo-(Gly1-L-Leu2-L-Ile3-L-Leu4-L-Leu5-L-Leu6-L-Leu7-L-Leu8-L-Leu9) (1) and cyclo-(Gly1-L-Leu2-L-Val3-L-Leu4-L-Leu5-L-Leu6-L-Leu7-L-Leu8-L-Leu9) (2) respectively on the basis of extensive spectroscopic analysis, particularly 2D NMR spectra taken at the temperature of 338 or 303K and MS.