Light-empowered contra-thermodynamic stereochemical editing

Nature Reviews Chemistry, Год журнала: 2022, Номер 7(1), С. 35 - 50

Опубликована: Ноя. 16, 2022

Язык: Английский

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Catalytic Approaches to Chemo- and Site-Selective Transformation of Carbohydrates

Chemical Reviews, Год журнала: 2023, Номер 123(10), С. 6793 - 6838

Опубликована: Апрель 26, 2023

Carbohydrates are a fundamental unit playing pivotal roles in all the biological processes. It is thus essential to develop methods for synthesizing, functionalizing, and manipulating carbohydrates further understanding of their functions creation sugar-based functional materials. is, however, not trivial such methods, since densely decorated with polar similarly reactive hydroxy groups stereodefined manner. New approaches chemo- site-selective transformations are, therefore, great significance revolutionizing sugar chemistry enable easier access sugars interest. This review begins brief overview innate reactivity carbohydrates. followed by discussions about catalytic enhance, override, or be orthogonal transformation avoids making list reactions, but rather focuses on summarizing concept behind each reported transformation. The literature references were sorted into sections based underlying ideas approaches, which we hope will help readers have better sense current state innovative field.

Язык: Английский

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Synergistic catalysis: An emerging concept for selective carbohydrate synthesis

Chem Catalysis, Год журнала: 2024, Номер 4(3), С. 100891 - 100891

Опубликована: Янв. 18, 2024

Harnessing modern catalytic concepts to address long-standing challenges in carbohydrate chemistry has garnered substantial interest from the synthetic community recent years. In particular, usage of multiple catalysts for sequential one-pot relay reactions already contributed major benefits accessing oligosaccharides past two decades. contrast, exploitation synergistic catalysis glycosciences is only its infancy. While methods combine stepwise into a single flask operation, they do not intrinsically alter reaction mechanisms. Conversely, involves creation unique mechanistic pathways by merging cycles. At nexus cycles, fertile opportunities arise bond-forming strategies that are possible within individual manifold. The realization underexploited potential expected accelerate developments field, thereby offering stereoselective entry points glycosidic chemical space was previously inaccessible.

Язык: Английский

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Stereochemical editing logic powered by the epimerization of unactivated tertiary stereocenters

Science, Год журнала: 2022, Номер 378(6618), С. 383 - 390

Опубликована: Окт. 27, 2022

The stereoselective synthesis of complex targets requires the precise orchestration chemical transformations that simultaneously establish connectivity and spatial orientation desired bonds. In this work, we describe a complementary paradigm for chiral molecules their isomers, which tunes three-dimensional structure molecule at late stage. Key to success strategy is development mild highly general photocatalytic method composed decatungstate polyanion disulfide cocatalysts, enable interconversion unactivated tertiary stereogenic centers were previously configurationally fixed. We showcase versatility method—and implementation stereoediting logic—by rapid construction scaffolds would be challenging access using existing tools by late-stage targets.

Язык: Английский

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Selective Axial-to-Equatorial Epimerization of Carbohydrates

Journal of the American Chemical Society, Год журнала: 2022, Номер 144(26), С. 11870 - 11877

Опубликована: Июнь 22, 2022

Radical-mediated transformations have emerged as powerful methods for the synthesis of rare and unnatural branched, deoxygenated, isomeric sugars. Here, we describe a radical-mediated axial-to-equatorial alcohol epimerization method to transform abundant glycans into isomers. The delivers highly predictable selective reaction outcomes that are complementary other sugar isomerization methods. synthetic utility isomer interconversion is showcased through expedient glycan synthesis, including one-step glycodiversification. Mechanistic studies reveal both site- diastereoselectivities achieved by H atom abstraction equatorially disposed α-hydroxy C–H bonds.

Язык: Английский

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Exploiting photoredox catalysis for carbohydrate modification through C–H and C–C bond activation

Nature Reviews Chemistry, Год журнала: 2022, Номер 6(11), С. 782 - 805

Опубликована: Сен. 21, 2022

Язык: Английский

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Catalytic Asymmetric Hydrogen Atom Transfer: Enantioselective Hydroamination of Alkenes

Journal of the American Chemical Society, Год журнала: 2023, Номер 145(29), С. 16118 - 16129

Опубликована: Июль 11, 2023

We report a highly enantioselective radical-based hydroamination of enol esters with sulfonamides jointly catalyzed by an Ir photocatalyst, Brønsted base, and tetrapeptide thiol. This method is demonstrated for the formation 23 protected β-amino-alcohol products, achieving selectivities up to 97:3 er. The stereochemistry product set through selective hydrogen atom transfer from chiral thiol catalyst prochiral C-centered radical. Structure–selectivity relationships derived structural variation both peptide olefin substrate provide key insights into development optimal catalyst. Experimental computational mechanistic studies indicate that hydrogen-bonding, π–π stacking, London dispersion interactions are contributing factors recognition enantioinduction. These findings further asymmetric catalysis contribute understanding noncovalent relevant such transformations.

Язык: Английский

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Multifaceted View on the Mechanism of a Photochemical Deracemization Reaction

Journal of the American Chemical Society, Год журнала: 2023, Номер 145(4), С. 2354 - 2363

Опубликована: Янв. 20, 2023

Upon irradiation in the presence of a chiral benzophenone catalyst (5 mol %), racemic mixture given imidazolidine-2,4-dione (hydantoin) can be converted almost quantitatively into same compound with high enantiomeric excess (80-99% ee). The mechanism this photochemical deracemization reaction was elucidated by suite mechanistic experiments. It corroborated nuclear magnetic resonance titration that binds two enantiomers two-point hydrogen bonding. In one diastereomeric complexes, atom at stereogenic carbon is ideally positioned for transfer (HAT) to photoexcited benzophenone. Detection protonated ketyl radical transient absorption revealed abstraction occur from only but not other hydantoin enantiomer. Quantum chemical calculations allowed us visualize HAT within complex and, more importantly, showed back does its oxygen atom. achiral enol formed process could directly monitored characteristic signal λ ≅ 330 nm. Subsequent tautomerization leads both enantiomers, them returns catalytic cycle, thus leading an enrichment data are fully consistent deuterium labeling experiments and deliver detailed picture synthetically useful reaction.

Язык: Английский

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Recent Advances in C–H Functionalisation through Indirect Hydrogen Atom Transfer

Molecules, Год журнала: 2023, Номер 28(16), С. 6127 - 6127

Опубликована: Авг. 18, 2023

The functionalisation of C–H bonds has been an enormous achievement in synthetic methodology, enabling new retrosynthetic disconnections and affording simple equivalents for synthons. Hydrogen atom transfer (HAT) is a key method forming alkyl radicals from substrates. Classic reactions, including the Barton nitrite ester reaction Hofmann–Löffler–Freytag reaction, among others, provided early examples HAT. However, recent developments photoredox catalysis electrochemistry have made HAT powerful tool capable introducing wide range functional groups into bonds. Moreover, greater mechanistic insights stimulated development increasingly site-selective protocols. Site-selectivity can be achieved through tuning electron density at certain using additives, judicious choice reagent, solvent system. Herein, we describe latest methods functionalizing C–H/Si–H/Ge–H indirect between 2018–2023, as well critical discussion reagents, aspects, substrate scopes, background contexts

Язык: Английский

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Covalent Organic Frameworks Based Photoenzymatic Nano‐reactor for Asymmetric Dynamic Kinetic Resolution of Secondary Amines

Angewandte Chemie International Edition, Год журнала: 2024, Номер 63(16)

Опубликована: Фев. 17, 2024

Abstract Bio‐catalysis represents a highly efficient and stereoselective method for the synthesis of valuable chiral compounds, however, poor stability limited reaction types free enzymes restrict their wide application in industrial production. In this work, to overcome these problems, multifunctional photoenzymatic nanoreactor CALB@COF‐Ir was developed through encapsulation Candida antarctica lipase B (CALB) photosensitive covalent organic framework COF‐Ir . This bio‐nanocluster serves as catalysts asymmetric dynamic kinetic resolution (DKR) secondary amines give series high yields (up 99 %) enantioselectivities % ee). The well‐designed not only acts safety cover prevent CALB from deactivation but promotes racemization via photo‐induced hydrogen atom transfer (HAT) process. Photoelectric characterization TDDFT calculation revealed that (ppy) 2 Ir units play crucial role photocatalytic system which enhance its photo‐redox properties facilitating separation between photoelectrons (e − ) holes (h + ). Furthermore, heterogeneous could be recycled five rounds with slight decline catalytic reactivity.

Язык: Английский

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