Synthesis and biological evaluation of 20-hydroxytriptonide and its analogues

Discovery of a novel water-soluble, rapid-release triptolide prodrug with improved drug-like properties and high efficacy in human acute myeloid leukemia

In this work, a series of water-soluble triptolide prodrugs were synthesized, and their triptolide release rate, pharmacokinetic characteristics and anti-tumor effect were measured. We found that inserting glycolic acid as a linker between triptolide and the cyclic amino acid accelerated the release of triptolide from prodrugs into the plasma while preserving its safety. Among them, prodrug TP-P1 was significantly better than Minnelide (the only water-soluble triptolide prodrug in clinical trials) in terms of release rate in plasma and synthetic yield. In mouse models of human acute myeloid leukemia (AML), TP-P1 was effective in reducing xenograft tumors at dose levels as low as 25 μg/kg, and eliminating tumors at dose 100 μg/kg. Furthermore, TP-P1 could significantly enhance the efficacy of FLT3 inhibitors in the treatment of AML. These experimental results showed the potential of TP-P1 as water-soluble prodrugs of triptolide.

Click Chemistry in Natural Product Modification

Click chemistry is perhaps the most powerful synthetic toolbox that can efficiently access the molecular diversity and unique functions of complex natural products up to now. It enables the ready synthesis of diverse sets of natural product derivatives either for the optimization of their drawbacks or for the construction of natural product-like drug screening libraries. This paper showcases the state-of-the-art development of click chemistry in natural product modification and summarizes the pharmacological activities of the active derivatives as well as the mechanism of action. The aim of this paper is to gain a deep understanding of the fruitful achievements and to provide perspectives, trends, and directions regarding further research in natural product medicinal chemistry.

Synthesis of celastrol derivatives as potential non-nucleoside hepatitis B virus inhibitors

A series of para-quinone methide (pQM) moiety and C-20- modified derivatives of celastrol were synthesized and evaluated for their inhibitory effect on the secretion of HBsAg and HBeAg as well as the inhibitory effect against HBV DNA replication. The results suggested that amidation of C-20 carboxylic group could generate derivatives with good anti-HBV profile, among them compound 14 showed the best inhibitory activity on the secretion of HBsAg (IC₅₀  = 11.9 µμ) and HBeAg (IC₅₀  = 13.1 µμ) with SI of 3.3 and 3.0, respectively. In addition, 14 also showed potent inhibitory effect against HBV DNA replication (48.5 ± 15.1%, 25 µM). This is, to our knowledge, the first report of celastrol derivatives as potential non-nucleoside HBV inhibitors.

An Overview of Saturated Cyclic Ethers: Biological Profiles and Synthetic Strategies

Saturated oxygen heterocycles are widely found in a broad array of natural products and other biologically active molecules. In medicinal chemistry, small and medium rings are also important synthetic intermediates since they can undergo ring-opening and -expansion reactions. These applications have driven numerous studies on the synthesis of oxygen-containing heterocycles and considerable effort has been devoted toward the development of methods for the construction of saturated oxygen heterocycles. This paper provides an overview of the biological roles and synthetic strategies of saturated cyclic ethers, covering some of the most studied and newly discovered related natural products in recent years. This paper also reports several promising and newly developed synthetic methods, emphasizing 3-7 membered rings.

A review of the total syntheses of triptolide

Triptolide is a complex triepoxide diterpene natural product that has attracted considerable interest in the organic chemistry and medicinal chemistry societies due to its intriguing structural features and multiple promising biological activities. In this review, progress in the total syntheses of triptolide are systematically summarized. We hope to gain a better understanding of the field and provide constructive suggestions for future studies of triptolide.

Identification of a diverse synthetic abietane diterpenoid library and insight into the structure-activity relationships for antibacterial activity

A diverse natural product-like (NPL) synthetic abietane diterpenoid library containing 86 compounds were obtained and the SARs were studied based on their antibacterial potential. Further in vitro cytotoxic and in silico drug-like properties evaluation showed that the potent antibacterial compound 84 had good drug-like properties and displayed low cytotoxicity toward noncancerous mammalian cells, indicating the study of AA and DHAA might be a good starting point for the search of novel antimicrobial molecules. Future work should be focused on the optimization of their potency and selectivity.

Click chemistry-based synthesis and anticancer activity evaluation of novel C-14 1,2,3-triazole dehydroabietic acid hybrids

A concise and efficient synthetic approach has been established to readily access a series of novel C-14 1,2,3-triazole-tethered dehydroabietic acid derivatives in moderate to high yields. In vitro antiproliferative activity evaluation indicated that most of the hybrids exhibited potent inhibitory activities in a variety of cancer cell lines with low micromolar to submicromolar IC₅₀ values. Further studies demonstrated that some of these analogues such as 20, 21, and 24 were also effective against adriamycin-resistant MCF-7 clone at low concentrations in a dose-dependent manner. Notably, the most potent compound 24, which possesses a 3-(tert-butoxycarbonylamino)phenyl-substituted triazole moiety, not only exhibited obviously improved IC₅₀ values ranging from 0.7 to 1.2 μM against a panel of tested cancer cells, but also showed very weak cytotoxicity on normal cells. Preliminary mechanism studies indicated that compound 24 could induce apoptosis in MDA-MB-231 cells and was worth developing into a novel natural product-like anticancer lead by proper structure modification.

Identification of a diverse synthetic abietane diterpenoid library for anticancer activity

A diverse natural-product-like synthetic abietane diterpenoid library contains about 56 compounds were obtained, and evaluated for their potential in vitro cytotoxic or antitumor activity against A549, PC-3 and SKOV-3 tumor cell lines by SRB assay. Treatment of A549 cells with the most potent compound ketone 19 showed induction of apoptosis, as revealed by JC-1 mitochondrial membrane potential staining, TUNNEL assay, western blotting analysis and flow cytometry assay.

Diterpenoids of terrestrial origin

This review covers the isolation and chemistry of diterpenoids from terrestrial as opposed to marine sources and includes, labdanes, clerodanes, pimaranes, abietanes, kauranes, gibberellins, cembranes and their cyclization products. The literature from January to December, 2014 is reviewed.

Divergent total synthesis of triptolide, triptonide, tripdiolide, 16-hydroxytriptolide, and their analogues

A divergent route was developed for the formal total synthesis of triptolide, triptonide, and tripdiolide, as well as a total synthesis of 16-hydroxytriptolide and their analogues in an enantioselective form. Common advanced intermediate 5 was concisely assembled by employing an indium(III)-catalyzed cationic polycyclization reaction and a palladium-catalyzed carbonylation-lactone formation reaction as key steps. This advanced intermediate was readily converted to the above natural products by using palladium-catalyzed cross-coupling or the Claisen rearrangement reaction as key steps. Additionally, preliminary structure-cytotoxic activity relationship studies of C13 suggested that it might be a new modification site that could still retain the cytotoxicity.