Two-directional synthesis and stereochemical assignment toward a C2 symmetric oxasqualenoid (+)-intricatetraol

The Tetrahydrofuran Motif in Marine Lipids and Terpenes

Heterocycles are particularly common moieties within marine natural products. Specifically, tetrahydrofuranyl rings are present in a variety of compounds which present complex structures and interesting biological activities. Focusing on terpenoids, a high number of tetrahydrofuran-containing metabolites have been isolated during the last decades. They show promising biological activities, making them potential leads for novel antibiotics, antikinetoplastid drugs, amoebicidal substances, or anticancer drugs. Thus, they have attracted the attention of the synthetics community and numerous approaches to their total syntheses have appeared. Here, we offer the reader an overview of marine-derived terpenoids and related compounds, their isolation, structure determination, and a special focus on their total syntheses and biological profiles.

Synthetic endeavours towards oxasqualenoid natural products containing 2,5-disubstituted tetrahydrofurans – eurylene and teurilene

Given the unique structural features of oxasqualenoid natural products and their cytotoxicity, representative examples from oxasqualenoids, eurylene and teurilene have been briefly reviewed. Both compounds possess cis- and trans-2,5-disubstituted tetrahydrofuran rings and represent chiral and achiral facets found in this class of natural products.

Canthin-6-one Alkaloids and a Tirucallanoid from Eurycoma longifolia and Their Cytotoxic Activity against a Human HT-1080 Fibrosarcoma Cell Line

Phytochemical investigation of the stems of Eurycoma longifolia Jack led to the isolation of two new canthin-6-one alkaloids, 4,9-dimethoxycanthin-6-one (1) and 10-hydroxy-11-methoxycanthin-6-one (2), and a new tirucallane-type triterpenoid, 23,24,25-trihydroxytirucall-7-en-3,6-dione (3), along with 37 known compounds. Among these, an oxasqualenoid (4) was isolated as a natural product for the first time. The structures of the isolates were elucidated by spectroscopic and mass spectrometric means. All the isolates were evaluated for their cytotoxic activity against a HT-1080 human fibrosarcoma cell line. Among them, 9,10-dimethoxycanthin-6-one (14, IC50 = 5.0 μM), 10-hydroxy-9-methoxycanthin-6-one (15, IC50 = 7.2 μM), dihydroniloticin (18, IC50 = 8.2 μM), and 14-deacetyleurylene (34, IC50 = 3.2 μM) displayed stronger activity than the positive control 5-FU (IC50 = 9.2 μM).