Total Synthesis Of Natural Products Research Articles

Current Applications of Organocatalysis in Total Synthesis of Natural Products at Room Temperature

Current Applications of Organocatalysis in Total Synthesis of Natural Products at Room Temperature

Highly efficient construction of angular polycycles

Angular tricyclic and polycyclic skeletons feature typical cores in an intriguing type of natural products. We herein report the Lewis acids-catalyzed dearomative (3 + 2) cycloadditions of donor-acceptor cyclopropanes with benzene ring, by which structurally complex and diverse angular tricyclic and polycyclic carbocycles were efficiently constructed from cheap and easily available feedstock and with convenient operation. This is also the example of (3 + 2) cycloaddition of a C3-synthon with the C = C of benzene. We believe this will demonstrate its potential in the total syntheses of natural products and drug discovery.

Metathesis Mastery: Crafting Linear Triquinane Frameworks for Natural Product Synthesis

AbstractOrganic and medicinal chemists have shown great interest in developing simple approaches for creating linear triquinane structures, as they are crucial for synthesizing both natural and synthetic products. Linear triquinane shows various biological characteristics like being commonly used for antitumor, antibacterial, and antimalarial purposes, making it a popular subject of study among synthetic chemists. These come from different sources like marine organisms, plants, and fungi and make up a significant group of sesquiterpenoids. These can be classified as cis‐syn‐cis or cis‐anti‐cis based on the stereochemistry at the ring junction, with cis‐anti‐cis being the most common type and exhibiting significant biological activity. In this review, we summarized different methods using a combination of photothermal and olefin metathesis strategy to construct a triquinane framework by utilizing both traditional heat and microwave radiation. Some commonly used synthetic methods, including metathesis protocol and key reactions like Grignard reaction and Diels–Alder reaction, were utilized together with ring‐closing, ring‐opining, and ring‐rearrangement metathesis to create the linear triquinane core for use in total synthesis of natural products. Additionally, the use of photothermal olefin metathesis along with Hosomi‐Sakurai reaction conditions allows for the creation of intricate polyquinanes, which can be used to produce complex natural compounds and for designing unique molecules theoretically.

Copper-catalyzed three-component reaction to construct thietane ring using elemental sulfur

Thietanes are vital aliphatic four-membered rings associated with various pharmaceuticals, building blocks and synthons of intermediates used in the total synthesis of natural products and biomolecules. Also, 4-thiazolidinone is a core pharmacophore of many drug molecules. Based on their various applications in medicinal chemistry and organic synthesis, an effort has been made to achieve a thietane ring on 4-thiazolidinone nucleus via quasi-benzylic acid-type intramolecular rearrangement using elemental sulfur, benzyl bromide and Cu(I). The designed methodology is environmentally benign, cheap, and easily accessible, with a broad range of substrate scopes and carried out by the employment of earth-abundant metal catalysts like copper.

Palladium-Catalyzed γ-C–H Arylation of Unsaturated Carbonyl Compounds: An Emerging Remote Buchwald–Hartwig–Miura Arylation

AbstractAs an important complement to the Buchwald–Hartwig–Miura arylation, Pd-catalyzed γ-C–H arylations, including γ-C(sp3)–H and γ-C(sp2)–H arylations, provide a more direct route to install an aryl group on the less reactive γ-site of unsaturated carbonyl compounds, and have attracted considerable interest from the chemistry community in recent years. This review summarizes the applications of this method with both cyclic and linear unsaturated carbonyl compounds (aldehydes, ketones, esters, amide, and nitriles), as well as in the total synthesis of natural products (NPs), natural product skeletons, and bioactive analogues.1 Introduction2 γ-C–H Arylation of Cyclic Unsaturated Carbonyl Substrates2.1 Exocyclic γ-Arylation2.1.1 Unsaturated Ketones and the Corresponding Silyl-Dienol Ethers2.1.2 Unsaturated Lactones2.2 Endocyclic γ-C–H Arylation2.2.1 Unsaturated Ketones and the Corresponding Silyl-Dienol Ethers2.2.2 Unsaturated Lactones2.2.3 Unsaturated Nitriles3 γ-C–H Arylation of Linear Unsaturated Carbonyl Substrates3.1 Unsaturated Aldehydes3.2 Unsaturated Ketones3.3 Unsaturated Amides3.4 Unsaturated Nitriles3.5 Silyl Ketene Acetals of α,β-Unsaturated Esters4 Conclusion

Total synthesis of Comfreyn A and structural analogues via two photochemical key steps.

In this work the influence of o-fluorine substituents on the photo-dehydro-Diels-Alder (PDDA) reaction was investigated and the findings of this study were applied to the total synthesis of natural products. The reactant molecules consisted of two alkyl arylpropiolates, connected by a suberic acid tether and bearing fluorine substituents in each of the o-positions. While quantum chemical calculations suggested that a fluorine substituent prevents an attack of the adjacent carbon atom in the second C-C bond forming step of the PDDA reaction, this attack took place nevertheless. The subsequent fluoride elimination, assisted by protic solvents or trialkylsilanes, resulted in an "Umpolung" of the 4-position of the cycloallene intermediate enabling the introduction of nucleophiles at this position. The nucleophilic replacement of the second fluorine substituent could also be triggered photochemically. After removal of the tether, the two arene moieties stand nearly perpendicular to each other and a selective excitation of the naphthalene moiety was possible. This led to an intramolecular photoinduced electron transfer (PET) followed by a nucleophilic replacement of the fluoride according to a SR+N1Ar* mechanism. The formed phenolic hydroxyl group underwent spontaneous lactonization with the adjacent ester group. Based on these results, the first total synthesis of the lignan Comfreyn A and some structural analogues were developed.

Development of Organocatalytic Reactions for the Synthesis of Natural Products and Pharmaceuticals

This review describes novel organocatalytic methods for the enantioselective construction of spiroindans and spirochromans and the application of the methods to the total synthesis of natural products. We developed an intramolecular Friedel-Craftstype 1,4-addition in which the substrates were a resorcinol derivative and 2-cyclohexenone linked by an alkyl chain. The reaction proceeded smoothly in the presence of a cinchonidine-based primary amine (30 mol%) with water and p-bromophenol as additives. A variety of spiroindanes were obtained with high enantioselectivity under these conditions. The reaction was applied in the first total synthesis of the unusual proaporphine alkaloid (-)-misramine, which included the key steps of enantioselective spirocyclization and double reductive amination of the keto-aldehyde to form a piperidine ring toward the end of the synthesis. The total synthesis of misrametine was achieved by selective demethylation of the methoxy group from the precursor to misramine. Next, a method for highly enantioselective organocatalytic construction of spirochromans containing a tetrasubstituted stereocenter was developed. An intramolecular oxy-Michael addition was catalyzed by a bifunctional cinchona alkaloid thiourea catalyst. A variety of spirochroman compounds containing a tetrasubstituted stereocenter were obtained with excellent enantioselectivity of up to 99% enantiomeric excess. The reaction was applied to the asymmetric formal synthesis of (-)-(R)-cordiachromene.

Chemo-enzymatic total synthesis: current approaches toward the integration of chemical and enzymatic transformations.

A steadily increasing number of reports have been published on chemo-enzymatic synthesis methods that integrate biosynthetic enzymatic transformations with chemical conversions. This review focuses on the total synthesis of natural products and classifies the enzymatic reactions into three categories. The total synthesis of five natural products: cotylenol, trichodimerol, chalcomoracin, tylactone, and saframycin A, as well as their analogs, is outlined with an emphasis on comparing these chemo-enzymatic syntheses with the corresponding natural biosynthetic pathways.

Recent Advance in the β‐Stereoselective Synthesis of 2‐Deoxy Glycosides

AbstractCompounds containing a 2‐deoxy β‐glycoside linkage play important roles in carbohydrate chemistry, serving as potential therapies with significant biological properties. From the viewpoint of synthesis, many strategies developed in recent years targeted the stereoselective construction of 2‐deoxy glycosides. This review aims to summarise recent advances in the synthetic routes toward 2‐deoxy β‐glycosides developed over the last decade. Where associated, practical applications of these strategies in the total synthesis of natural products are highlighted.

Natural hypoglycaemic bioactives: Newer avenues and newer possibilities.

The incidences of endocrine and metabolic disorders like diabetes have increased worldwide. Several proposed molecular pathways mechanisms for the management of diabetes have been identified, but glycaemic control is still a challenging task in the drug discovery process. Most of the drug discovery processes lead to numerous scaffolds that are prominent in natural products. The review deals with the natural bioactives as an α-amylase inhibitors, α-glucosidase inhibitors, protein tyrosine phosphatase-1B inhibitors, dipeptidyl peptidase-IV inhibitors, G-protein coupled receptors-40 agonists, PPAR-γ agonists and the activators of 5'-adenosine monophosphate-activated protein kinase and glucokinase. So, in this review, we focused on the hypoglycaemic bioactives, which will assist scientific developers, traditional medicinal practitioners, and readers to discover some potent antidiabetic molecules. Strategies like chemometric approaches, scaffold hopping, and total synthesis of natural products by group modification or ring opening/closing mechanism could be useful for the development of novel hit/lead antidiabetic molecules. The study concludes that each phyto molecule inherits a potential to get explored by repurposing techniques for various antidiabetic targets and offer an alternative antidiabetic therapeutic medicinal potential.

Aerobic Oxidation of PMB Ethers to Carboxylic Acids.

The first aerobic protocol of direct transformation of p-methoxybenzyl (PMB) ethers to carboxylic acids efficiently with Fe(NO3)3 ⋅ 9H2O and TEMPO as catalysts at room temperature has been developed. The reaction accommodates C-Br bond, terminal/non-terminal C-C triple bond, amide, cyano, nitro, ester, and trifluoromethyl groups. Even highly selective oxidative deprotection of different benzylic PMB ethers has been realized. The reaction has been successfully applied to the total synthesis of natural product, (R)-6-hydroxy-7,9-octadecadiynoic acid, demonstrating the practicality of the method. Based on experimental studies, a possible mechanism involving oxygen-stabilized benzylic cation has been proposed.

1,2-trans-Diaminocyclohexane (DACH) in Asymmetric Catalysis: Nearing Fifty Years of Faithful Service and Counting

AbstractThis review highlights the use of DACH as a versatile ligand in catalytic asymmetric transformations providing mechanistic rationales and relevant comments presented in chronological order for each of the 21 reaction types with references up to December 25, 2023. Intended to be as practically comprehensive as possible, this review assembles useful examples of using DACH as a ligand in organocatalytic or as metal complexes in asymmetric transformations. The resulting enantiomerically enriched, if not pure, chiral non-racemic small molecules are of great utility as value added intermediates in the total synthesis of natural products, in the design and synthesis of medicinally important compounds, and in other areas in organic and bioorganic chemistry where chirality plays a role. The graphic image depicts Spartacus with his arms folded in the same sense of chirality as (R,R)-DACH.1 Introduction2 DACH: A Brief Historical Narrative3 Catalytic Asymmetric Hydrogenation of Alkenes4 Catalytic Asymmetric Dihydroxylation of Alkenes5 Catalytic Asymmetric Sulfoxidation and Sulfimidation6 Catalytic Asymmetric 1,4-Conjugate Addition6.1 Using Jacobsen’s DACH Metal–salen Complexes as Catalysts6.2 Using Takemoto’s Bifunctional H-Bonding DACH Thiourea Organocatalyst6.3 Using DACH Ni(II) Complexes as Catalysts6.4 Using DACH H-Bonding Catalysis7 Catalytic Asymmetric Epoxidation of Alkenes8 Catalytic Asymmetric Claisen Rearrangement9 Catalytic Asymmetric 1,2-Nucleophilic Addition to Carbonyl Compounds9.1 Catalytic Asymmetric Addition of Dialkylzinc to Aldehydes and Ketones9.2 Catalytic Asymmetric Alkynylation of Aldehydes and Ketones9.3 Catalytic Asymmetric Addition of Cyanide to Aldehydes and Ketones10 Catalytic Asymmetric Allylic Alkylation11 Catalytic Asymmetric Cyclopropanation of Alkenes12 Catalytic Asymmetric Cycloaddition Reactions13 Catalytic Asymmetric Aziridination of Alkenes14 Catalytic Asymmetric Hydrogenation of Prochiral Ketones and Imines15 Catalytic Asymmetric Aldol Reactions16 Catalytic Asymmetric Opening of Small Ring Systems16.1 Desymmetrization of meso-Epoxides and meso-Aziridines16.2 Kinetic Resolution of Racemic Epoxides16.3 Enantioselective Addition of CO2 to Epoxides16.4 Enantioselective Ring Opening of Oxetanes17 Catalytic Asymmetric Strecker Reactions18 Catalytic Asymmetric Mannich Reactions19 Catalytic Asymmetric Henry and Aza-Henry Reactions20 Catalytic Asymmetric Morita–Baylis–Hillman and Rauhut–Currier Reactions21 Catalytic Asymmetric Petasis Reactions22 Organocatalytic Asymmetric Cascade Reactions23 Miscellaneous Catalytic Reactions24 Conclusion and Outlook25 DACH Catalysts and Ligands List

Heavy Atom Quantum Mechanical Tunneling in Total Synthesis.

Contributions from quantum mechanical tunneling to the rates of several radical coupling reactions between carbon sp2 centers used as key steps in natural product total syntheses were computed using density functional theory. Contributions ranging from ∼15-52% from tunneling were predicted at room temperature, thereby indicating that tunneling plays an important role in the rates of these reactions and should perhaps be considered when designing complex synthetic schemes.

Recent advances in palladium‐catalyzed α‐arylation reactions

The indispensable role of α‐arylated compounds in chemistry can be accounted from its presence in various pharmaceuticals we use in our daily life. Chemists are establishing diverse methods for the synthesis of various α‐arylated compounds by considering their applications in different fields including biology, medicine, agrochemicals, material science, etc. Diverse pharmacologically active compounds, natural products, and drugs contain α‐arylated carbonyl groups in their structure. The impact of transition metal catalysis in chemistry is overwhelming, among which palladium is the predominant due to its high reactivity as well as catalytic potential. α‐Arylation reactions with palladium catalysts have been successful in producing a variety of desired chemicals. The formation of active pharmaceutical ingredients and total synthesis of natural products can now be achieved by the development of novel pathways through the α‐arylation of carbonyl compounds, catalyzed by palladium. Wide variety of simple arylating agents could be used under the condition of palladium catalysis. Syntheses that utilize α‐arylation methods often offer advanced ways that improve overall yields, expand the scope of the synthesis, and reduce the steps. One of the synthetic achievements is the increased selectivity obtained with lower amounts of the catalyst. Gentle reaction conditions were employed, and broad substrate scope was accomplished. Recent advances in the α‐arylation reactions of various compounds, catalyzed by palladium, is discussed in this review covering literature from 2016 to 2022.

Relevant Developments in the Use of Three-Component Reactions for the Total Synthesis of Natural Products. The last 15 Years.

Multicomponent reactions (MCRs) offer a highly useful and valuable strategy that can fulfill an important role in synthesizing complex polysubstituted compounds, by simplifying otherwise long sequences and increasing their efficiency. The total synthesis of selected natural products employing three-component reactions as their common strategic MCR approach, is reviewed on a case-by-case basis with selected targets conquered during the last 15 years. The revision includes detailed descriptions of the selected successful sequences; relevant information on the isolation, and bioactivity of the different natural targets is also briefly provided.

Strategies for the Construction of Benzobicyclo[3.2.1]octane in Natural Product Synthesis.

Benzobicyclo[3.2.1]octane is a cage-like unique motif containing a bicyclo[3.2.1]octane structure fused with at least one benzene ring. It is found in various natural products that exhibit structural complexities and important biological activities. The total synthesis of natural products possessing this challenging structure has received considerable attention, and great advances have been made in this field during the past 15 years. This review summarizes thus far achieved chemical syntheses and synthetic studies of natural compounds featuring the benzobicyclo[3.2.1]octane core. It focuses on strategic approaches constructing the bridged structure, aiming to provide a useful reference for inspiring further advancements in strategies and total syntheses of natural products with such a framework.

Cluster Preface: Biomimetic Synthesis

Jun Deng (left) received his B.Sc. from Lanzhou University and his Ph.D. from the Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences (2014) with Professor Ang Li. After a short period of postdoctoral research in the lab of Professor Andrew Myers at Harvard University (2014–2016), he was appointed a Pioneer ‘Hundred Talents Program’ Researcher at Kunming Institute of Botany, Chinese Academy of Sciences in 2017. In December 2020, he moved to Nankai University where he is a professor at the College of Chemistry. He received the Thieme Journals Award (2020). His research focuses on natural product total synthesis and medicinal chemistry. Yefeng Tang (right) earned his B.S. from Lanzhou University (1995–1999) and his M.S. from the Institute of Materia Medica, Chinese Academy of Medical Science (1999–2002). From 2003 to 2006, he pursued his Ph.D. under the guidance of Professor Zhen Yang and Professor Jiahua Chen at Peking University. Subsequently, he conducted postdoctoral research with Prof. K. C. Nicolaou at The Scripps Research Institute between 2006 and 2009. In 2010, he commenced his independent career at the School of Pharmaceutical Sciences, Tsinghua University, where he is now a tenured professor. His primary research interests encompass the total synthesis of natural products, the development of synthetic methodologies, and the discovery of antiviral and anti-aging drugs.

Indolyl‐Ynones: Building Blocks for Molecular Diversity

AbstractThis review centers on the synthetic strategies employed with indolyl‐ynones. Indolyl‐ynone, owing to its highly reactive ynone moiety, frequently partakes in dearomatizing spirocyclization reactions and subsequent rearrangement reactions when subjected to various reaction conditions. Hence, various heterocycles such as densely functionalized spiroindolenines, carbazoles, quinolines and carbo‐and hetero‐cycle substituted indoles are synthesized from indolyl‐ynones. In addition to this, the versatile spirocyclic indole scaffold exhibits the capability to produce tetracyclic and polyclic structures through intricate skeletal rearrangement processes. Moreover, the total synthesis of natural products using the indolyl‐ynone moiety was also compiled in this review.

Total Synthesis of Tetracyclic Spirooxindole Alkaloids via a Double Oxidative Rearrangement/Cyclization Cascade.

Skeleton rearrangement could rapidly transfer simple molecules to complex structures and has significant potential in the total synthesis of natural products. We developed a one-pot reaction cascade of double oxidative rearrangement of furan and indole followed by a nucleophilic cyclization that was successfully applied for the formal synthesis of rhynchophylline/isorhynchophylline and the first total synthesis of (±)-7(R)-geissoschizol oxindole/(±)-7(S)-geissoschizol oxindole. In addition, the geissoschizol oxindoles were revised to their C3 epimers, and the mechanism for the reversed stereochemistry through the retro-Mannich/Mannich cascade was proposed and supported by density functional theory calculations.

Microwave-Promoted Total Synthesis of Puniceloid D for Modulating the Liver X Receptor.

A growing global health concern is metabolic syndrome, which is defined by low HDL, diabetes, hypertension, and abdominal obesity. Nuclear receptors are attractive targets for treatment of diseases associated with metabolic syndrome. Liver X receptors (LXRs) have become one of the most significant pharmacological targets among nuclear receptors. Multiple research studies emphasize the essential function of the liver X receptor (LXR) in the pathophysiology of metabolic syndrome. Puniceloid D, among natural products, demonstrated promising effects on LXRα. However, attempts at the total synthesis of natural products were faced with challenges, including long synthetic steps and low yields, requiring a more efficient approach. In this study, for the first time, we successfully synthesized puniceloid D through a seven-step process and conducted docking studies to gain a comprehensive understanding of the interactions involved in the binding of puniceloid D to LXR within different heterodimeric contexts. Our understanding of the pathophysiology of metabolic syndrome could be improved by these findings, which might assist with the development of novel treatment strategies.