14‐Membered Cyclopeptides from Paliurus ramosissimus and P. hemsleyanus

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 (ÀOH) 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.

Isolation and structure elucidation of cyclopeptide alkaloids from Ziziphus nummularia and Ziziphus spina-christi by HPLC-DAD-MS and HPLC-PDA-(HRMS)-SPE-NMR

“…The NMR data of compound 1 (Table 1 and 2) showed great similarity with the NMR data previously reported for ramosine-A (Lin et al, 2003). Ramosine-A contains a paracyclophane.…”

Isolation and Structure Elucidation by LC-DAD-MS and LC-DAD-SPE-NMR of Cyclopeptide Alkaloids from the Roots of Ziziphus oxyphylla and Evaluation of Their Antiplasmodial Activity

“…The configuration of nummularine-R ( 1 ) has been described in 2010 by Nisar et al, based on NOESY interactions, and indeed the l -configuration was found for the three amino acid units present in this cyclopeptide alkaloid . The l -configuration was also reported for hemsine-A ( 4 ) and ramosine-A ( 6 ) . In oxyphylline-C ( 8 ) the two ring-bound amino acid units were found to be present in the l -configuration as well .…”

“…Compound 6 was identified as ramosine-A, mainly based on the NMR data obtained. This cyclopeptide alkaloid was previously reported from Paliurus ramosissimus , but this is the first time it has been isolated from Z. oxyphylla (batch 2). Compound 7 was reported in Z. oxyphylla by Kaleem et al and was isolated from the first batch of plant material.…”

Highly Regioselective 5‐endo‐tet Cyclization of 3,4‐Epoxy Amines into 3‐Hydroxypyrrolidines Catalyzed by La(OTf)3

“…[8] The use of this reaction was demonstrated by the synthesis of ap yrrolidine-derived bioactive compound via the construction of 3-hydroxy-2-alkyl-pyrrolidine, which is ap ivotal scaffold contained in various alkaloids and bioactive agents. [9][10][11] Unfortunately,t he net yield of the 3-hydroxy-2-alkylpyrrolidine wasm oderate owingt ot he modestr egioselectivity of the Eu(OTf) 3 -catalyzed aminolysis of the 3,4-epoxy alcohol, indicatingt here is room for further improvement.…”

“…1 [b] Eu(OTf) 3 (1) PhMe (0.05) 88 %( 1h)12:1 2 [b] La(OTf) 3 (1) PhMe (0.05) 87 %( 2h)13:1 3 [b] TfOH 10PhMe (0.05) 75 %( 24 h) 11:1 4 [b] none PhMe (0.05) NR (24 h) -5La(OTf) 3 (10) MeCN (0.05) 88 %( 6h)10:1 6La(OTf) 3 (10) THF (0.05) 90 %( 18 h) 12:1 7La(OTf) 3 (10) ( endo-tet cyclization smoothly proceededi nt he presence of electron-rich and electron-deficient benzyl groups( 2ba, 2ca).…”