Artemisians A–D, Diseco-guaianolide Involved Heterodimeric [4 + 2] Adducts from Artemisia argyi

Abstract

Artemisians A-D (1-4), the first examples of [4 + 2] Diels-Alder type adducts presumably biosynthesized from a rare 1, 10-4, 5-diseco-guaianolide and a guaianolide diene, along with their possible precursor 5, were isolated from the traditional Chinese medicine Artemisia argyi. The structures of 1-4 were elucidated by extensive spectroscopic analyses and calculated electronic circular dichroism. Compound 2, with an IC value of 3.21 μM, exhibited significant antiproliferative activity via apoptosis induction and G2/M arrest in MDA-MB-468 cells.

Three Pairs of New Spirocyclic Alkaloid Enantiomers From the Marine-Derived Fungus Eurotium sp. SCSIO F452

“…With the advancements in whole-genome sequencing and searching tools of biosynthetic gene clusters of secondary metabolites, some Diels-Alderases, such as SpnF, PyrE3, Pyrl4, AbyU, and PvhB, have been identified and substantiated to be of great importance in the biosynthesis of NPs (Takao et al, 2005; Kim et al, 2011; Fage et al, 2015; Tian et al, 2015; Byrne et al, 2016; Tan et al, 2019). Besides, some NPs like spirotriscoumarins A and B (Tang et al, 2016), artemisians A–D (Xue et al, 2017), and alpininoids A–E (Liu et al, 2018) are proposed to be biosynthesized by spontaneous DA cycloaddition. A plausible biogenetic route of 1 – 4 is proposed in Scheme 1.…”

Taicrypnacids A and B, a Pair of C37 Heterodimeric Diterpenoid Stereoisomers from Taiwania cryptomerioides

“…Although podocarpane ( a ) was not obtained from the leaves of this plant, the synthesis of 1 and 2 seemed to occur via an HDA cycloaddition between the podocarpane ( a ) unit and trans -ozic acid ( 3 ) (Scheme ). Because of the steric repulsions caused by the labdane moiety, the terminal double bond in 3 would attack the α,β-unsaturated carbonyl group in podocarpane ( a ) from its α and β sides to generate the pair of stereoisomers 1 and 2 , respectively. ,− A few natural products have been proposed to be biosynthesized via HDA cycloaddition, such as artemisians A–D, rhodomyrtials A and B, and hyperjaponaols A–D, while taicrynacids A ( 1 ) and B ( 2 ) are the first reported C 37 heterodimeric diterpenoids.…”

“…Some important chemical components including diterpenoids, sesquiterpenoids, and bisflavones have been isolated from the leaves, bark, and wood of this plant . Among them, taiwaniadducts, including various novel dimeric diterpenoids (DDs) and a cycloaddition product of a monoterpene and a diterpenoid, have attracted much attention from organic chemists due to their complex structures and varied linkage types. − To data, no less than 180 DDs have been obtained from natural sources, and nine taiwaniadducts have been isolated from T. cryptomerioides . , These taiwaniadducts are connected with a labdane unit and an abietane unit with characteristic [2 + 2], [4 + 2] (Diels–Alder, DA), and [5 + 2] cycloaddition linkage types. − The DA cycloadducts are synthesized via regular cycloaddition reactions between the conjugated Δ 12(13),14(15) double bonds of the isoprene unit in the labdane moiety and the Δ 7(8) electron-deficient double bond in the abietane unit to generate a six-membered ring. , In a search for structurally diverse DDs and potent bioactive components, a pair of unique C 37 heterodimeric diterpenoid stereoisomers, taicrynacids A ( 1 ) and B ( 2 ), have been obtained from the leaves of T. cryptomerioides . These possess an uncommon decalino­[1,2,3- de ]­benzopyran heterotetracyclic core formed by a hetero [4 + 2] (Hetero-Diels–Alder, HDA) cycloaddition. , The HDA cycloaddition reaction generates a pyranoid D-ring via the α,β-unsaturated carbonyl group in the podocarpane (trinorabietane) unit (diene) and the double bond of the labdane unit to form the unique heterotetracyclic core.…”

Artematrovirenolides A—D and Artematrolides S—Z, Sesquiterpenoid Dimers with Cytotoxicity against Three Hepatoma Cell Lines from Artemisia atrovirens

“…Sesquiterpenoid dimers are an uncommon subclass of sesquiterpenoids due to their structural diversity and the wide range of bioactivities, and have attracted more and more research interests at the present time. Up to now, a variety of sesquiterpenoid dimers with potential in the treatment of liver cancer [ 6‐7 ] and antiinflammatory activities have been isolated from Artemisia species. [ 8‐19 ] Guaiane‐type sesquiterpenoid dimers are the main classes of sesquiterpenoid dimers in this genus, predominantly composed of two alike or unlike monomeric sesquiterpene lactone units through different connecting model.…”