14-Membered Cyclopeptides fromPaliurus ramosissimus andP. hemsleyanus

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 1H- and 13C-NMR spectra of these two types of alkaloids were observed.