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

ABSTRACT: 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: [Image: see text] ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s13659-017-0133-y) contains supplementary material, which is available to authorized users.