Total Synthesis of Highly Oxygenated Bisabolane Sesquiterpene Isolated from Ligularia lankongensis: Relative and Absolute Configurations of the Natural Product

Inhibitory Activity of N- and S-Functionalized Monoterpene Diols Towards Monoamine Oxidases A and B

Monoamine oxidase B (MAO-B) inhibitors are widely used as part of combination drug therapy for Parkinson's disease. As demonstrated in both in vitro and in vivo experiments, the monoterpenoid Prottremine and some of its derivatives exhibit high antiparkinsonian activity. In this study, the inhibitory activity of Prottremine and its derivatives (including 14 new 9-N- and S-derivatives) against MAO-A and MAO-B enzymes has been investigated for the first time. Compounds containing fragments of substituted anilines have demonstrated the highest activity against MAO-A; for example, compound 28 had an IC50 of 178 ± 44 μM. A significant proportion of the compounds tested, including Prottremine, exhibited moderate inhibitory activity towards MAO-B, with the most active being the o-aminoacetophenone derivative, which had an IC50 of 95 ± 5 μM. A molecular docking method for studying murine MAO-A and -B enzymes was developed using AlphaFold2 (v2.3.2), with further improvements. For the MAO-B enzyme, a strong correlation was observed between the molecular docking data and the measured activity of the compounds, with the maximum binding affinity registered for the most active compound. It is conceivable that the antiparkinsonian activity of Prottremine and some of its derivatives may be partially mediated, among other mechanisms, by MAO-B enzyme inhibition.

Discovery of N-X anomeric amides as electrophilic halogenation reagents

Electrophilic halogenation is a widely used tool employed by medicinal chemists to either pre-functionalize molecules for further diversity or incorporate a halogen atom into drugs or drug-like compounds to solve metabolic problems or modulate off-target effects. Current methods to increase the power of halogenation rely on either the invention of new reagents or activating commercially available reagents with various additives such as Lewis or Brønsted acids, Lewis bases and hydrogen-bonding activators. There is a high demand for new reagents that can halogenate otherwise unreactive compounds under mild conditions. Here we report the invention of a class of halogenating reagents based on anomeric amides, taking advantage of the energy stored in the pyramidalized nitrogen of N-X anomeric amides as a driving force. These robust halogenating methods are compatible with a variety of functional groups and heterocycles, as exemplified on over 50 compounds (including 13 gram-scale examples and 1 flow chemistry scale-up).

Bisabolane-type sesquiterpenoids: Structural diversity and biological activity

Bisabolane-type sesquiterpenoids, a class of monocyclic sesquiterpenoids, are widely distributed in nature and have a variety of biological activities. To provide a reference for the further research and development of these compounds, the phytochemical and biological properties of natural bisabolane-type sesquiterpenoids (356 compounds in total) isolated between 1985 and 2020 from 24 families, primarily Compositae, Zingiberaceae, Aspergillaceae, Halichondriidae, and Aplysiidae were reviewed. In vitro and in vivo studies have indicated that antibacterial, anti-inflammatory, and cytotoxic effects are the most commonly reported pharmacological properties of bisabolane-type sesquiterpenoids. Owing to their extensive significant effects, a lot of traditional medicines containing this type of compounds have been used for a long history. Thus, bisabolane-type sesquiterpenoids are a rich source of important natural products, which show great potential for the development of new drugs.

Chemical Constituents of Ligularia Species (Asteraceae) and Their Diversity in East Asia

More than 100 Ligularia species and those of several related genera (Cremanthodium, Cacalia, Senecio, and others) in the plant family Senecioneae grow in East Asia. For many years, researchers have studied the chemical constituents of these plants, and terpenoids, flavonoids, sterols, alkaloids, and aromatic compounds have been isolated. Among these, in particular, numerous sesquiterpenoids were reported. In this contribution, relevant chemical studies are described mainly from literature reports appearing since 2000, inclusive of investigations performed by the present authors, on the diversity in secondary metabolites of Ligularia growing in the Hengduan Mountains area of China, focusing on eremophilane sesquiterpenoids and other metabolites. Terpenoids and aromatic compounds (totaling 1049), both new and known, are listed. Genetic studies and synthesis investigations are also reviewed briefly.

Reactions of Allylmagnesium Reagents with Carbonyl Compounds and Compounds with C═N Double Bonds: Their Diastereoselectivities Generally Cannot Be Analyzed Using the Felkin-Anh and Chelation-Control Models

This review describes the additions of allylmagnesium reagents to carbonyl compounds and to imines, focusing on the differences in reactivity between allylmagnesium halides and other Grignard reagents. In many cases, allylmagnesium reagents either react with low stereoselectivity when other Grignard reagents react with high selectivity, or allylmagnesium reagents react with the opposite stereoselectivity. This review collects hundreds of examples, discusses the origins of stereoselectivities or the lack of stereoselectivity, and evaluates why selectivity may not occur and when it will likely occur.

Chemical Studies of Cremanthodium (Asteraceae) Species; Sesquiterpenoids and Related Compounds

Chemical constituents of Cremanthodium angustifolium, C. brunneopilosum, C. campanulatum, C. daochengense, C. discoideum, C. ellisii, C. helianthus, C. lineare, C. nobile, C. potaninii, C. principis, C. pulchrum, C. rhodocephalum, C. stenactinium, C. pleurocaule, and C. stenoglossum were reviewed. They produced mainly sesquiterpenoids–bicyclic and/or tricyclic eremophilanes, bisabolanes, bakkanes–and related compounds. Cremanthodium was shown to be close to Ligularia in chemical constituents.

Bisabolane, Oplopane, and Lignan Constituents of Cremanthodium campanulatum Collected in China

The chemical constituents in the roots of 3 Cremanthodium campanulatum Diels (Asteraceae) samples collected in Yunnan and Sichuan Provinces, China, were chemically investigated. A total of 8 bisabolane-type sesquiterpenoids, 2 of which were new, and a new oplopane-type sesquiterpenoid, along with a new lignan were isolated and their structures elucidated based on spectroscopic analyses. This is the first report on the chemical study of C. campanulatum.

Biotransformation of (+)-Carvone and (-)-Carvone by the Common Cutworm Spodoptera litura Larvae

Biotransformation of (+)- and (-)-carvone (1 and 2) by the larvae of common cutworm (Spodoptera litura) has been investigated. (+)-Carvone was transformed to (+)-(4S)-10-hydroxycarvone (1-1), (+)-(4S)-7- hydroxycarvone (1-2), and (-)-(4S)-8,9-dihydroxy-8,9-dihydrocarvone (1-3). (-)-Carvone (2) was transformed to (-)-(4R)-10-hydroxycarvone (2-1), (-)-(4R)-7-hydroxycarvone (2-2), (+)-(4R)-8,9-dihydroxy-8,9- dihydrocarvone (2-3), and (-)-(2R,4R)-10-hydroxycarveol (2-4). The results indicate that the main metabolic reaction of carvones by S. litura larvae is oxidation at vinyl group (C-8 and C-9).