A general, concise, ‘collective’ approach to eudesmanolide sesquiterpenoids: total synthesis of bioactive atractylenolides I–IV and related natural products

Natural products as IL-6 inhibitors for inflammatory diseases: Synthetic and SAR perspective

Interleukin-6 (IL-6), a pleiotropic cytokine, plays a pivotal role in the pathophysiology of various diseases including diabetes, atherosclerosis, Alzheimer's disease, multiple myeloma, rheumatoid arthritis, and prostate cancer. The signaling pathways associated with IL-6 offer promising targets for therapeutic interventions in inflammatory diseases and IL-6-dependent tumors. Although certain anti-IL-6 monoclonal antibodies are currently employed clinically, their usage is hampered by drawbacks such as high cost and potential immunogenicity, limiting their application. Thus, the imperative arises to develop novel small non-peptide molecules acting as IL-6 inhibitors. Various natural products derived from diverse sources have been investigated for their potential to inhibit IL-6 activity. Nevertheless, these natural products remain inadequately explored in terms of their structure-activity relationships. In response, our review aims to provide syntheses and structure activity perspective of natural IL-6 inhibitors. The comprehensive amalgamation of information presented in this review holds the potential to serve as a foundation for forthcoming research endeavors by medicinal chemists, facilitating the design of innovative IL-6 inhibitors to address the complexities of inflammatory diseases.

Neurotrophic Natural Products

Neurotrophins (NGF, BDNF, NT3, NT4) can decrease cell death, induce differentiation, as well as sustain the structure and function of neurons, which make them promising therapeutic agents for the treatment of neurodegenerative disorders. However, neurotrophins have not been very effective in clinical trials mostly because they cannot pass through the blood-brain barrier owing to being high-molecular-weight proteins. Thus, neurotrophin-mimic small molecules, which stimulate the synthesis of endogenous neurotrophins or enhance neurotrophic actions, may serve as promising alternatives to neurotrophins. Small-molecular-weight natural products, which have been used in dietary functional foods or in traditional medicines over the course of human history, have a great potential for the development of new therapeutic agents against neurodegenerative diseases such as Alzheimer's disease. In this contribution, a variety of natural products possessing neurotrophic properties such as neurogenesis, neurite outgrowth promotion (neuritogenesis), and neuroprotection are described, and a focus is made on the chemistry and biology of several neurotrophic natural products.

BF3·Et2O-Mediated annulation of α-keto acids with aliphatic ketones for the synthesis of γ-hydroxy-butenolides and γ-alkylidene-butenolides

Annulation reaction of α-keto acids with cyclic or acyclic aliphatic ketones is reported herein to divergently access γ-hydroxy-butenolides and γ-alkylidene-butenolides depending on the amount of BF₃·Et₂O. This protocol features good functional tolerance and ease of operation, to open a route to access butenolides via an annulation and dehydration process.

An efficient approach to divergently access γ-hydroxy-butenolides and γ-alkylidene-butenolides via annulation reaction of α-keto acids with simple aliphatic ketones is reported herein.

Atractylenolides, essential components of Atractylodes-based traditional herbal medicines: Antioxidant, anti-inflammatory and anticancer properties

The rhizome of the plant Atractylodes macrocephala Koidz is the major constituent of the Traditional Chinese Medicine Baizhu, frequently used to treat gastro-intestinal diseases. Many traditional medicine prescriptions based on Baizhu and the similar preparation Cangzhu are used in China, Korea and Japan as Qi-booster. These preparations contain atractylenolides, a small group of sesquiterpenoids endowed with antioxidant and anti-inflammatory properties. Atractylenolides I, II and III also display significant anticancer properties, reviewed here. The capacity of AT-I/II/IIII to inhibit cell proliferation and to induce cancer cell death have been analyzed, together with their effects of angiogenesis, metastasis, cell differentiation and stemness. The immune-modulatory properties of ATs are discussed. AT-I has been tested clinically for the treatment of cancer-induced cachexia with encouraging results. ATs, alone or combined with cytotoxic drugs, could be useful to treat cancers or to reduce side effects of radio and chemotherapy. Several signaling pathways have been implicated in their multi-targeted mechanisms of action, in particular those involving the central regulators TLR4, NFκB and Nrf2. A drug-induced reduction of inflammatory cytokines production (TNFα, IL-6) also characterizes these molecules which are generally weakly cytotoxic and well tolerated in vivo. Inhibition of Janus kinases (notably JAK2 and JAK3 targeted by AT-I and AT-III, respectively) has been postulated. Information about their metabolism and toxicity are limited but the long-established traditional use of the Atractylodes and the diversity of anticancer effects reported with AT-I and AT-III should encourage further studies with these molecules and structurally related natural products.

TiCl4-n-Bu3N-mediated cascade annulation of ketones with α-ketoesters: a facile synthesis of highly substituted fused γ-alkylidene-butenolides

A facile protocol for the synthesis of highly substituted fused γ-alkylidene butenolides using direct annulation of ketones with α-ketoesters, which proceeds through TiCl4-n-Bu3N mediated aldol addition followed by an intramolecular enol-lactonization/cyclization cascade, is reported. Diverse 6-5, 7-5 and 8-5 fused bicyclic γ-ylidene butenolides and highly substituted monocyclic analogs related to biologically relevant natural products were prepared from readily accessible ketone and α-ketoester building blocks. The highly step-economic cascade nature, good substrate scope, easy access to complex products with good to excellent yields, gram-scalability, demonstration of synthetic utility, and unambiguous structural confirmation through X-ray crystallography analyses and analogy are the salient features of this work.