Total Synthesis of Aryl C-Glycoside Natural Products: Strategies and Tactics
TL;DR: The aryl C-glycoside structure is, among the plenty of biologically active natural products, one of the distinct motifs embedded, and the synthetic strategies and tactics employed in the total synthesis of this class of natural products.
Abstract: The aryl C-glycoside structure is, among the plenty of biologically active natural products, one of the distinct motifs embedded. Because of the potential bioactivity as well as the synthetic challenges, these structures have attracted considerable interest, and extensive research toward the total synthesis has been performed. This Review focuses on the synthetic strategies and tactics employed in the total synthesis of this class of natural products. The Introduction describes the historical background, structural features, and synthetic problems associated with aryl C-glycoside natural products. Next the Review summarizes the methods for constructing the aryl C-glycoside bonds. Completed total syntheses—and, in some cases, selected examples of incomplete syntheses—of natural aryl C-glycosides are also summarized. Finally described are the strategies for constructing polycyclic structures, which were utilized in the total syntheses.
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TL;DR: The total syntheses of polycyclic natural products by exploiting an aryne as the key reactive species are reviewed and early examples and recent reports on the use of arynes in multistep syntheses are described.
Abstract: The total syntheses of polycyclic natural products by exploiting an aryne as the key reactive species are reviewed. A short introduction summarizes the basic reactivities of aryne species as well as the methods for its generation. In the main part, early examples and the recent reports (mainly 2012–present) on the use of arynes in multistep syntheses are described.
166 citations
01 Sep 2019
TL;DR: A simple and powerful bioinspired strategy for the stereoselective synthesis of C-aryl glycosides via palladium-catalysed ortho-directed C(sp2)−H functionalization of arenes and heteroarenes with easily accessible glycosyl chloride donors using a palladium catalyst is reported.
Abstract: C-aryl glycosides are widely found in nature and play important roles in drug design. Despite the significant progress made over the past few decades, efficient and stereoselective synthesis of complex C-aryl glycosides remains challenging, lagging far behind the state of the art of the synthesis of O- or N-glycosides. Here, we report a simple and powerful bioinspired strategy for the stereoselective synthesis of C-aryl glycosides via palladium-catalysed ortho-directed C(sp2)−H functionalization of arenes and heteroarenes with easily accessible glycosyl chloride donors. The catalytic palladacycle intermediate generated via C−H palladation provides a soft aryl nucleophile that can react with glycosyl oxocarbenium ion partners with high efficiency and excellent stereocontrol. The method can be applied to a wide range of arene and heteroarene substrates, glycosyl chloride donors and auxiliary groups. It can simplify the synthesis of a variety of complex C-aryl glycosides and offers a tool for late-stage modification of drug molecules. C-aryl glycosides are present in many natural products and of interest in drug design, but their chemical synthesis is challenging. This work reports an efficient and diastereoselective ortho-directed C−H glycosylation of arenes and heteroarenes with glycosyl chloride using a palladium catalyst.
75 citations
TL;DR: The progress of glycosyl radical-based C-glycoside synthesis between 1999-2020 is summarized, focusing on the stereoselectivity and recently developed methodologies such as α-alkoxyacyl telluride-related, photo-mediated and transition-metal catalysed reactions.
Abstract: C-Glycosylation involving glycosyl radical intermediates is a particularly effective approach to access C-glycosides, which are core units of a great number of natural products, bioactive compounds and marketed drugs. In this review, we summarize the progress of glycosyl radical-based C-glycoside synthesis between 1999-2020, focusing on the stereoselectivity and recently developed methodologies such as α-alkoxyacyl telluride-related, photo-mediated and transition-metal catalysed reactions. Metal-mediated reductive cross coupling is also covered due to its close relationship with the latter approaches. To introduce several strategies for achieving uncommon β-stereoselective C-glycosylation, we also briefly described organotin-based methods.
66 citations
TL;DR: The technology developed herein represents an unprecedented example of Catellani-type alkylation involving a SN1 pathway and is showcased by preparing glycoside-pharmacophore conjugates and a dapagliflozin analogue.
Abstract: In this work, we describe a Catellani-type C–H glycosylation to provide rapid access to various highly decorated α-C-(hetero)aryl glycosides in a modular and stereoselective manner (>90 examples). ...
52 citations
TL;DR: Diastereoselective direct hydroarylation of glycals with aromatic compounds was realized by use of an iridium/binap catalyst, giving the corresponding C-glycosyl compounds in high yields.
Abstract: Diastereoselective direct hydroarylation of glycals with aromatic compounds was realized by use of an iridium/binap catalyst, giving the corresponding C-glycosyl compounds in high yields. The use o...
41 citations
References
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TL;DR: In this paper, a rapid and mild esterification method using carboxylic 2,4,6-trichlorobenzoic anhydrides in the presence of 4-dimethylaminopyridine was developed.
Abstract: A rapid and mild esterification method using carboxylic 2,4,6-trichlorobenzoic anhydrides in the presence of 4-dimethylaminopyridine was developed. The method was also successfully applied to the synthesis of large-ring lactones, including DL-2,4,6-tridemethyl-3-deoxymethynolide.
1,882 citations
TL;DR: The Diels-Alder reaction has both enabled and shaped the art and science of total synthesis over the last few decades to an extent which has yet to be eclipsed by any other transformation in the current synthetic repertoire as mentioned in this paper.
Abstract: The Diels-Alder reaction has both enabled and shaped the art and science of total synthesis over the last few decades to an extent which, arguably, has yet to be eclipsed by any other transformation in the current synthetic repertoire. With myriad applications of this magnificent pericyclic reaction, often as a crucial element in elegant and programmed cascade sequences facilitating complex molecule construction, the Diels-Alder cycloaddition has afforded numerous and unparalleled solutions to a diverse range of synthetic puzzles provided by nature in the form of natural products. In celebration of the 100th anniversary of Alder's birth, selected examples of the awesome power of the reaction he helped to discover are discussed in this review in the context of total synthesis to illustrate its overall versatility and underscore its vast potential which has yet to be fully realized.
1,427 citations
TL;DR: All reports of total syntheses that utilize arynes in ways that build complexity or introduce motifs essential to the completion of their targets are recounted.
Abstract: Within 14 years of the seminal experiments of J. D. Roberts
leading to the first proposal of the structure of benzyne (1), synthetic organic chemists recognized the potential to exploit this highly reactive intermediate (and its substituted variants) in the total synthesis of natural products. More specifically, it was recognized that arynes offered the strategic advantage of rapidly functionalizing an aromatic ring by forming multiple carbon− carbon or carbon−heteroatom bonds in a single operation, often in a regioselective manner. Initially, the scope of synthetic
applications was somewhat limited by the harsh conditions
required to produce the aryne species. Many of these methods required strong bases, such as n-BuLi, or high temperatures (Scheme 1). However, with the development of milder methods for the generation of arynes came increased interest in employing them in the synthesis of more complex polycyclic systems. Most recently, the use of o-silyl aryl triflates as aryne precursors has allowed generation of the reactive intermediate under almost neutral conditions.
To date, over 75 individual natural products have been
prepared using arynes to generate key synthetic intermediates. Herein are recounted the reports of total syntheses that utilize arynes in ways that build complexity or introduce motifs essential to the completion of their targets. The methods by which the authors featured in this review accomplish this task reflect the versatility of arynes as reactive intermediates for synthesis (Scheme 2). For the purposes of organization, the syntheses are divided into subgroups on the basis of the type of aryne transformation: (i) nucleophilic additions or multicomponent reactions, (ii) σ-bond insertion reactions, (iii) [4 + 2]- and [2 + 2]-cycloaddition strategies, and (iv) metal-catalyzed aryne reactions.
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