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 303 K and MS.