Absolute configuration of franganine

Chemical constituents of Antidesma bunius aerial parts and the anti-AGEs activity of selected compounds

Thirty-three natural products were isolated from the aerial parts of Antidesma bunius, Euphorbiaceae, a plant used in Vietnamese traditional medicine against rheumatoid arthritis. All compounds were reported the first time for this species, and nine constituents resembled undescribed natural products, noticeably three coumarinolignans with 2,2-dimethyl-1,3-dioxolane moiety, two cyclopeptides, and two furofuran-type lignans connected with a phenylpropanoid moiety. The individual structures were elucidated by combining NMR and MS data, and their configuration was established by NOESY and ECD experiments and NMR calculations. Compounds with sufficient amount were analyzed for their inhibition of advanced glycation endproducts (AGEs) formation, metabolites involved in many diseases like Alzheimer, joint diseases or diabetes. With IC₅₀ values below 0.2 mM rutin and p-hydroxyphenethyl trans-ferulate showed to be moderately active, both still being 10-times more active than the positive control aminoguanidine.

Isolation and Total Synthesis of Kinenzoline, an Antitrypanosomal Linear Depsipeptide Isolated from a Marine Salileptolyngbya sp. Cyanobacterium

Kinenzoline (1), a new linear depsipeptide, was isolated from a marine Salileptolyngbya sp. cyanobacterium. Its structure was elucidated by spectroscopic analyses and degradation reactions. In addition, we achieved a total synthesis of 1 and confirmed its structure. Kinenzoline (1) showed highly selective antiproliferative activity against the causative organism of sleeping sickness, Trypanosoma brucei rhodesiense (IC₅₀ 4.5 μM), compared to normal human cells (WI-38, IC₅₀ > 100 μM). Kinenzoline (1) is a promising lead compound for the development of new antitrypanosomal drugs.

Approaches to Cyclophane-Types of Cyclopeptide Alkaloids

The cyclopeptide alkaloids are cyclic depsipeptides incorporating cyclophanes with polyamide units 13-, 14- and 15-membered macrocyclic systems. Although various pharmacological activities have been ascribed to cyclopeptide alkaloids from plants of the Rhamnacea family, these studies have been hampered by their low availability due to the lack of reasonable amounts distributed in nature. Therefore, novel and efficient synthetic approaches should be an important aim, which inspired us to examine how to diversely construct the unique structures of this type of natural products. In this account, several typical strategies are presented in terms of efficient, stereocontrolled and regioselective synthesis of cyclopeptide alkaloids.

Isolation and structure elucidation of cyclopeptide alkaloids from the leaves of Heisteria parvifolia

Heisteria parvifolia Sm. is prescribed in traditional medecine against numerous diseases in Côte d'Ivoire. Due to the shortcoming in scientifical knowledge of use of this species, our investigations revealed five undescribed cyclopeptide alkaloids added to one known derivative namely anorldianine. These compounds were elucidated by 1D and 2D-NMR experiments and comparison with literature data, and confirmed by HR-ESI-MS. Cytotoxic activity evaluation of these compounds against the chronic myeloid leukemia (K565) cell line exhibited an antiproliferative activity with cell growth inhibition from 13% to 46%.

Total synthesis of the reported structure of ceanothine D via a novel macrocyclization strategy

The first total synthesis of the reported structure of ceanothine D, a cyclopeptide alkaloid found in red root, was achieved using a highly convergent synthetic strategy. Highlights of the synthesis include the first concomitant macrocyclization and formation of the unique chiral tertiary alkyl-aryl ether bond with complete regio- and stereo-control in the presence of a sensitive Z-enamide moiety to access the strained para-cyclophane present in its structure. This synthetic strategy may be broadly applicable in the generation of other structurally similar cyclopeptide alkaloids, enabling further biological and chemical investigations.