14‐Membered Cyclopeptides from <i>Paliurus ramosissimus</i> and <i>P. hemsleyanus</i>

Abstract

Abstract Six 14‐membered cyclopeptide alkaloids, i.e. , ramosines A–C, mucronine J, and lotusines A and D, were isolated from the roots of Paliurus ramosissimus , and an additional four, hemsines A–D, from the roots of P. hemsleyanus. Among these, ramosines A–C ( 1, 5 , and 6 , resp.) and hemsines A and B ( 7 and 8 , resp.) are new bases of the amphibine‐B type, and hemsines C and D ( 9 and 10 , resp.) are new integerrine‐type alkaloids. Additionally, ramosine C ( 6 ) represents the first 14‐membered cyclopeptide alkaloid possessing a substitution (OH) at C(13′). Their structural elucidations were based on spectral analysis and molecular‐modeling studies. Pronounced solvent effects in the 1 H‐ and 13 C‐NMR spectra of these two types of alkaloids were observed.