Semisynthesis and antitumor activity of endertiin B and related triterpenoids from Ganoderma lucidum

Ganoderma lucidum, a fungus used in traditional Chinese medicine, is known for its medicinal value attributed to its active components called Ganoderma triterpenoids (GTs). However, the limited isolation rate of these GTs has hindered their potential as promising drug candidates. Therefore, it is imperative to achieve large-scale preparation of GTs. In this study, four GTs were effectively synthesised from lanosterol. The antitumor activity of these GTs was evaluated in vivo. Endertiin B exhibited potent inhibitory activity against breast cancer cells (9.85 ± 0.91 μM and 12.12 ± 0.95 μM). Further investigations demonstrated that endertiin B significantly upregulated p21 and p27 and downregulated cyclinD1 expression, arresting the cell cycle at the G0/G1 phase and inducing apoptosis by decreasing BCL-2 and increasing BAX and BAK levels. Additionally, endertiin B was found to reduce the expression of proteins associated with the PI3K-AKT signaling pathway. To summarize, endertiin B effectively inhibited cell proliferation by blocking the cell cycle and inducing apoptosis through the PI3K-AKT pathway.

Synthesis of obtusifoliol and analogues as CYP51 substrates

Sterol 14α-demethylases (CYP51s) are a ubiquitous superfamily of cytochrome P450 enzymes that play an essential role in sterol biosynthesis. As fungal CYP51s are the target of azole-based antifungal agents, which are facing the problem of increasing resistance, the substrate specificity of this enzyme subclass has recently garnered significant attention. Herein we report the first chemical synthesis of the final endogenous substrate of this enzyme class, obtusifoliol, in 1.3% yield across ten steps from a commercially available lanosterol mixture. Intermediates along this pathway provide a basis for further derivatisation of the sterol skeleton and future investigation into CYP51 inhibition to overcome pathogens' azole resistance.

Synthesis of Sea Cucumber Saponins with Antitumor Activities

Holostane glycosides are characteristic metabolites of sea cucumbers, which possess various biological activities. Here, we report the synthesis of two representative congeners, namely, pervicoside B and C, starting from lanosterol with the longest linear sequence of both 34 steps and in 0.3% overall yields. The flexible synthetic approach has enabled us to expeditiously prepare 16 analogues for preliminary studies on the key structural features influencing their antiproliferative activities against tumor cells. A simplified disaccharide is found to be as potent as natural tetrasaccharides, which can be used as a lead for future studies.

Chemical synthesis of marine saponins

Covering: 1989-2017 Saponins are characteristic metabolites of starfish and sea cucumbers, and occasionally are also found in sponges, soft coral, and small fish. These steroid or triterpenoid glycosides often show remarkable biological and pharmacological activities, such as antifungal, antifouling, shark repellent, antitumor and anti-inflammatory activities. Over one thousand marine saponins have been characterized; the majority of them can be categorized into three major structural types, i.e., asterosaponins, polyhydroxysteroid glycosides, and holostane glycosides. Thus far, only 12 marine saponins have been synthesized; those representing the major types were successfully synthesized recently. The syntheses involve preparation of the aglycones from the terrestrial steroid or triterpene materials, installation of the carbohydrate units, and manipulation of the protecting groups. Herein, we provide a comprehensive review on these syntheses.

Transition-metal free oxidative C-H etherification of acylanilines with alcohols through a radical pathway

A transition metal free approach for the synthesis of methyl/ethyl aryl ether via oxidative C-H etherification of acylanilines with alcohols has been developed. Various acylanilines are compatible under standard conditions, giving the corresponding products in moderate to good yields. This strategy avoids transition-metal catalyst and excessive alcohol, providing a simple and reliable alternative method for the synthesis of methyl/ethyl aryl ether. Control experiments reveal that a radical mechanism is involved in this transformation.