Total Synthesis of (+)-Herpotrichones A-C.

Epoxyquinoids herpotrichones A-C exhibit unique 6/6/6/6/3 pentacyclic frameworks and potent neuroprotective effects. Inspired by their proposed biosynthetic origins, we completed a total synthesis of herpotrichones A-C by devising a synthesis of epoxyquinol monomer and leveraging a key Diels-Alder (DA) reaction between epoxyquinol monomer-based dienophiles and delitpyrone C-derived dienes. DFT calculations anticipated competing pathways, including homodimerization and regio- and stereoisomers formation, necessitating precise control over reaction selectivity during the key DA reaction.

Discovery, structure revision, synthesis, and application of all known and even unknown securingine alkaloids.

Covering: up to 2025Natural product-based research encompasses the discovery, structure elucidation, biosynthesis, synthesis, and application of naturally occurring secondary metabolites. Securingine alkaloids, isolated from , have emerged as valuable molecular frameworks for exploring various aspects of natural product research due to their distinct chemical structures, characterized by unique oxidation and rearrangement patterns. Herein, we provide a comprehensive account of our journey in developing novel synthetic strategies and tactics for accessing all known and even unknown securingines and investigating the potential application of securingine B as a novel class of natural product-based molecular photoswitches.

α--phthalimido-oxy isobutyrate-mediated deoxygenative arylation: total synthesis of alanenses A and B.

Inspired by a biosynthetic hypothesis of alanense A, we developed two distinct methods for the deoxygenative arylation of α--phthalimido-oxy isobutyrate (NPIB), derived from hydroxyl groups adjacent to or conjugated with a carbonyl moiety. One approach utilizes photoredox catalysis to achieve a radical-mediated arylation reaction. The other approach involves an acid-mediated arylation method that proceeds through a cationic intermediate.

Total Synthesis of (-)-Elodeoidins A and B.

Biomimicry has long been a valuable approach for designing efficient synthetic strategies in complex natural product synthesis. However, abiotic yet powerful transforms can significantly streamline the synthesis by introducing greater convergence to the synthetic route. Herein, we delineate a convergent total synthesis of elodeoidins A and B, enabled by a cross-dehydrogenative coupling (CDC) reaction between an aldehyde and an electron-deficient olefin.

Total synthesis of (-)-flueggenine A and (-)-15'--flueggenine D.

Securinega alkaloids, known for their unique structures and neuroplasticity-inducing potential, are promising candidates for treating neurodegenerative diseases such as depression and substance use disorders (SUD). Herein, we delineate the total synthesis of two dimeric Rauhut-Currier (RC) reaction-based securinega alkaloids, (-)-flueggenine A and (-)-15'--flueggenine D. The key step involved a novel reductive Heck dimerization strategy, utilizing a silyl-tethered enone coupling partner to ensure the desired reactivity and stereoselectivity.

Synthesis and Structure Revision of Securingine E.

Chemical synthesis plays a crucial role in confirming and revising the structures of natural products. Through meticulous synthetic efforts, NMR spectroscopic and single-crystal X-ray diffraction analyses, DFT calculations, and mass spectrometric investigations, we revised the structure of securingine E. The revised structure of securingine E was unambiguously confirmed by its chemical synthesis.

Natural product anticipation via chemical synthesis: Discovery of two new securinega alkaloids.

The isolation of a natural product conventionally precedes its chemical synthesis. Often, the isolation and structure determination of a natural product present in minute quantities in its natural source pose formidable challenges, akin to finding "a needle in a haystack." On the other hand, leveraging plausible biosynthetic insights and biomimetic synthetic expertise would allow for the prior synthesis of presumed natural products, followed by their verification in natural sources.

A large-scale reaction dataset of mechanistic pathways of organic reactions.

Understanding organic reaction mechanisms is crucial for interpreting the formation of products at the atomic and electronic level, but still remains as a domain of knowledgeable experts. The lack of a large-scale dataset with chemically reasonable mechanistic sequences also hinders the development of reliable machine learning models to predict organic reactions based on mechanisms as human chemists do. Here, we present a high-quality and the first large-scale reaction dataset, denoted as mech-USPTO-31K, with chemically reasonable arrow-pushing diagrams validated by synthetic chemists, encompassing a wide spectrum of polar organic reaction mechanisms.

Development of an Easy-To-Handle Redox Active Group for Alcohols: Catalytic Transformation of Tertiary Alcohols to Nitriles.

The generation of radical intermediates via SET-mediated deoxygenation of activated alcohol derivatives is desirable, as alcohols can be utilized in various radical-mediated reactions. Herein, we introduce α--phthalimido-oxy isobutyrate (NPIB) as a novel activating group for alcohols. Essentially, it is a more chemically robust alternative to Overman's -phthalimidoyl oxalate group.

Total synthesis of (-)-securingine G.

In this study, we present the first total synthesis of (-)-securingine G. Diverging from the proposed biosynthetic pathway, our approach involves the addition of nucleophilic pyridine anion species to the electrophilic menisdaurilide congener. Crucially, incorporating a weakly basic yet nucleophilic tri(2-pyridinyl)lanthanum complex proved essential to circumvent undesired base-mediated pathways during the key coupling reaction.

Transformation of (allo)securinine to (allo)norsecurinine via a molecular editing strategy.

Securinega alkaloids have intrigued chemists since the isolation of securinine in 1956. This family of natural products comprises a securinane subfamily with a piperidine substructure and norsecurinane alkaloids featuring a pyrrolidine core. From a biosynthetic perspective, the piperidine moiety in securinane alkaloids derives from lysine, whereas the pyrrolidine moiety in norsecurinane natural products originates from ornithine, marking an early biogenetic divergence.

Synthesis of Suffranidine B.

Efficiently generating intricate molecular complexity is a coveted goal in organic synthesis. This can be realized through the implementation of inventive and audacious strategies coupled with the exploration and advancement of novel molecular reactivity pathways. Herein, we present a concise two-step synthesis of a high-oxidation state heterotrimeric securinega alkaloid, suffranidine B, from 2,3-dehydroallosecurinine and the vinylogous ketoaldehyde compound derived from kojic acid.

Synthesis of High-Order and High-Oxidation State Alkaloids.

alkaloids, composed of more than 100 members characterized by the compact tetracyclic scaffold, have fascinated the synthetic community with their structural diversity and notable bioactivities. On the basis of the structural phenotype, oligomerizations and oxidations are major biosynthetic diversification modes of the basic framework. Despite the rich history of synthesis of basic monomeric alkaloids, the synthesis of oligomeric alkaloids, as well as oxidized derivatives, has remained relatively unexplored because of their extra structural complexity.

Collective total synthesis of C4-oxygenated securinine-type alkaloids via stereocontrolled diversifications on the piperidine core.

Securinega alkaloids have fascinated the synthetic chemical community for over six decades. Historically, major research foci in securinega alkaloid synthesis have been on the efficient construction of the fused tetracyclic framework that bears a butenolide moiety and tertiary amine-based heterocycles. These "basic" securinega alkaloids have evolved to undergo biosynthetic oxidative diversifications, especially on the piperidine core.

Synthesis and structure-activity relationship study of saponin-based membrane fusion inhibitors against SARS-CoV-2.

We previously discovered that triterpenoid saponin platycodin D inhibits the SARS-CoV-2 entry to the host cell. Herein, we synthesized various saponin derivatives and established a structure-activity relationship of saponin-based antiviral agents against SARS-CoV-2. We discovered that the C3-glucose, the C28-oligosaccharide moiety that consist of (→3)-β-d-Xyl-(1 → 4)-α-l-Rham-(1 → 2)-β-d-Ara-(1 → ) as the last three sugar units, and the C16-hydroxyl group were critical components of saponin-based coronavirus cell entry inhibitors.

Alkylidene Carbene from Silyl Vinyl Iodide Provides Mechanistic Insights on Trimethylenemethane Diyl-Mediated Tandem Cyclizations.

We describe a method to generate alkylidene carbenes via tetramethylammonium-fluoride-induced desilylation of silyl vinyl iodides. The reversible carbene generation from an iodovinyl anion enabled us to unearth mechanistic aspects of the trimethylenemethane (TMM) diyl cyclization reaction that could not be explored via previous methods. We observed that a slow diyl-diylophile cycloaddition can induce the reversible formation of an alkylidene carbene from the TMM diyl intermediate via a retro-cyclopropanation at ambient temperature.

Synthesis of Dimeric Securinega Alkaloid Flueggeacosine B: From Pd-Catalyzed Cross-Coupling to Cu-Catalyzed Cross-Dehydrogenative Coupling.

We completed the synthesis of dimeric high-oxidation-state securinega alkaloid flueggeacosine B via two synthetic routes from allosecurinine. The first-generation synthesis (seven overall steps) involved a Liebeskind-Srogl cross-coupling reaction for the union of two functionalized fragments, the organostannane and the thioester. As a means to further streamline the synthetic route, we have developed a visible-light-mediated Cu-catalyzed cross-dehydrogenative coupling (CDC) reaction between an aldehyde and an electron-deficient olefin.

On the Erosion of Enantiopurity of Rhodonoids via Their Asymmetric Total Synthesis.

Rhodonoid natural products are found in nature as a scalemic mixture. This interesting phytochemical feature is presumed to originate from a reversible electrocyclic ring opening of the chromene core present in the biogenetic precursors of rhodonoids. Herein, we systematically investigated factors that are responsible for this racemization event.

Synthesis and Reactivity of 1-Hydroxyherquline A.

Herein, we present the synthesis of 1-hydroxyherquline A and describe its reactivity discovered during its attempted conversion to herquline A, a long-sought natural product target in the synthetic chemical community. The strategic installation of the C1 hydroxyl group enabled the key -Michael addition-mediated N10-C2 bond formation and eventually access to 1-hydroxyherquline A, the most advanced herquline A congener reported to date. Our attempted reductive transformation of 1-hydroxyherquline A to herquline A was challenged by the extremely strained bowl-shaped pentacyclic structures of key precursors that prevented either radical formation at C1 or protonation (or hydrogenation) from the desired face.

Biopatterned Reorganization of Alkaloids Enabled by Ring-Opening Functionalization of Tertiary Amines.

Biosynthetic processes often involve reorganization of one family of natural products to another. Chemical emulation of nature's rearrangement-based structural diversification strategy would enable the conversion of readily available natural products to other value-added secondary metabolites. However, the development of a chemical method that can be universally applied to structurally diverse natural products is nontrivial.

Synthesis of Pentacyclic Framework of Herquline A.

The highly strained bowl-shaped pentacyclic structure of herquline A has rendered it one of the most difficult problems in organic synthesis yet to be solved. The challenges associated with the synthesis of herquline A have been well documented in four Ph.D.

Total synthesis of dimeric alkaloids (-)-flueggenines D and I.

We describe the total synthesis of (-)-flueggenines D and I. This features the first total synthesis of dimeric alkaloids with a C(α)-C(δ') connectivity between two monomeric units. The key dimerization was enabled by a sequence that involves Stille reaction and conjugate reduction.

Platycodin D, a natural component of Platycodon grandiflorum, prevents both lysosome- and TMPRSS2-driven SARS-CoV-2 infection by hindering membrane fusion.

An ongoing pandemic of coronavirus disease 2019 (COVID-19) is now the greatest threat to global public health. Herbal medicines and their derived natural products have drawn much attention in the treatment of COVID-19, but the detailed mechanisms by which natural products inhibit SARS-CoV-2 have not been elucidated. Here, we show that platycodin D (PD), a triterpenoid saponin abundant in Platycodon grandiflorum (PG), a dietary and medicinal herb commonly used in East Asia, effectively blocks the two main SARS-CoV-2 infection routes via lysosome- and transmembrane protease serine 2 (TMPRSS2)-driven entry.

Total Synthesis of Cinnamodial-Based Dimer (-)-Capsicodendrin.

We describe the first total synthesis of cinnamodial-based dimer (-)-capsicodendrin. First, we developed a 12-step synthetic route to access (-)-cinnamodial from 1-vinyl-2,6,6-trimethylcyclohexene. We then showed that (-)-cinnamodial can selectively dimerize to (-)-capsicodendrin under kinetically controlled basic conditions.

Total Synthesis of (+)-Pestalofone A and (+)-Iso-A82775C.

We describe the total synthesis of epoxyquinoid natural products (+)-pestalofone A and (+)-iso-A82775C. The synthesis of (+)-16-oxo-iso-A82775C, the putative biosynthetic precursor of pestalofone C, is also presented. The allene moiety present in (+)-iso-A82775C and (+)-16-oxo-iso-A82775C was constructed from the ketodiene-yne group via a biosynthetically relevant sequence involving a conjugate reduction and a base-catalyzed tautomerization.