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-(Gly 1 - l -Leu 2 - l -Ile 3 - l -Leu 4 - l -Leu 5 - l -Leu 6 - l -Leu 7 - l -Leu 8 - l -Leu 9 ) ( 1 ) and cyclo-(Gly 1 - l -Leu 2 - l -Val 3 - l -Leu 4 - l -Leu 5 - l -Leu 6 - l -Leu 7 - l -Leu 8 - l -Leu 9 ) ( 2 ) respectively on the basis of extensive spectroscopic analysis, particularly 2D NMR spectra taken at the temperature of 338 or 303 K and MS. Graphical Abstract