Construction of the Skeleton of Lucidumone

Photoinduced formal [4 + 2] cycloaddition of two electron-deficient olefins and its application to the synthesis of lucidumone

Electronically mismatched Diels-Alder reaction between two electron-deficient components is synthetically useful and yet underdeveloped under thermal conditions. Herein, a photoinduced formal [4 + 2] cycloaddition of enone with a variety of electron-deficient dienes is described. Key to the success of this stepwise methodology relies on a C - C bond cleavage/rearrangement of the cyclobutane based overbred intermediate via diversified mechanistic pathways. Based on this annulation method, total synthesis of lucidumone is achieved in nine steps.

Insights into Ganoderma fungi meroterpenoids opening a new era of racemic natural products in mushrooms

Ganoderma meroterpenoids (GMs) containing 688 structures to date were discovered to have multiple remarkable biological activities. 65.6% of meroterpenoids featuring stereogenic centers from Ganoderma species are racemates. Further, GMs from different Ganoderma species seem to have their own characteristics. In this review, a comprehensive summarization of GMs since 2000 is presented, including GM structures, structure corrections, biological activities, physicochemical properties, total synthesis, and proposed biosynthetic pathways. Additionally, we especially discuss the racemic nature, species-related structural distribution, and structure-activity relationship of GMs, which will provide a likely in-house database and shed light on future studies on GMs.

Enantioselective total synthesis of (‒)-lucidumone enabled by tandem prins cyclization/cycloetherification sequence

The Ganoderma meroterpenoids are a growing class of natural products with architectural complexity, and exhibit a wide range of biological activities. Here, we report an enantioselective total synthesis of the Ganoderma meroterpenoid (‒)-lucidumone. The synthetic route features several key transformations, including a) a Cu-catalyzed enantioselective silicon-tethered intramolecular Diels-Alder cycloaddition to construct the highly functionalized bicyclo[2.2.2]octane moiety; b) Brønsted acid promoted tandem O-deprotection/Prins cyclization/Cycloetherification sequence followed by oxidation to install concurrently the tetrahydrofuran and the fused indanone framework; c) Fleming-Tamao oxidation to generate the secondary hydroxyl; d) an iron-catalyzed Wacker-type oxidation of hindered vinyl group to methyl ketone.

Structural diversity, hypothetical biosynthesis, chemical synthesis, and biological activity of Ganoderma meroterpenoids

Covering: 2018 to 2022Meroterpenoids found in fungal species of the genus Ganoderma and known as Ganoderma meroterpenoids (GMs) are substances composed of a 1,2,4-trisubstituted benzene and a polyunsaturated side chain. These substances have attracted the attention of chemists and pharmacologists due to their diverse structures and significant bioactivity. In this review, we present the structures and possible biosynthesis of representative GMs newly found from 2018 to 2022, as well as chemical synthesis and biological activity of some interesting GMs. We propose for the first time a plausible biosynthetic pathway for GMs, which will certainly motivate further research on the biosynthetic pathway in Ganoderma species, as well as on chemical synthesis of GMs as important bioactive compounds for the purpose of drug development.

Pd-Catalyzed intermolecular asymmetric allylic dearomatization of 1-nitro-2-naphthols with MBH adducts

An asymmetric allylic dearomatization reaction of 1-nitro-2-naphthol derivatives with Morita-Baylis-Hillman (MBH) adducts has been developed. By utilizing Pd catalyst derived from Pd(OAc)₂ and Trost ligand (R,R)-L1, the reaction proceeded smoothly in 1,4-dioxane at room temperature, affording substituted β-naphthalenones in good yields (up to 92%) and enantioselectivity (up to 90% ee). A range of substituted 1-nitro-2-naphthols and MBH adducts were found to be compatible under the optimized conditions. This reaction provides a convenient method for the synthesis of enantioenriched 1-nitro-β-naphthalenone derivatives.

Retro-[4+2]/Intramolecular Diels–Alder Cascade Allows a Concise Total Synthesis of Lucidumone

Lucidumone is a recently isolated meroterpenoid displaying interesting biological activity. This natural product possesses a complex structure, including a bicyclo[2.2.2]octane possessing 6 contiguous stereogenic centers. Herein, we discuss strategies to solve this synthetic challenge. In particular, we developed a new method for the inverse electron-demand Diels–Alder cycloaddition between 2-pyrones and acyclic enol ethers, as a mean to obtain a ‘masked’ cyclohexadiene. This method allowed an expeditious enantioselective synthesis of (+)-lucidumone through a retro-[4+2]/intramolecular Diels–Alder reaction cascade.

1 Introduction

2 Retrosynthetic Considerations on the Bicyclo[2.2.2]octane

3 Development of a Methodology for Enantioselective IEDDA Cycloadditions

4 Enantioselective Total Synthesis of (+)-Lucidumone

5 Conclusion

Gram-Scale Enantioselective Synthesis of (+)-Lucidumone

The first enantioselective total synthesis of (+)-lucidumone is described through a 13-step synthetic pathway (longest linear sequence). The key steps involve the formation of a bridged bicyclic lactone by an enantioselective inverse-electron-demand Diels-Alder cycloaddition, C-O bond formation to assemble two fragments, and a one-pot retro-[4 + 2]/[4 + 2] cycloaddition cascade. The synthesis is scalable, and more than one gram of natural product was synthesized in one batch.