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.