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

Shatskiy, Andrey; Stepanova, Elena V.; Kärkäs, Markus D.

doi:10.1038/s41570-022-00422-5

Cited by 31 publications

(21 citation statements)

References 221 publications

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“…Photoredox/hydrogen atom transfer (HAT) co-catalysis has emerged as a powerful method for the functionalization of carbohydrates through the formation of carbon-centered radicals. Once formed, sugar-derived radicals display versatile reactivity that can be exploited to achieve useful modifications, including alkylation, epimerization, oxidation, and deoxygenation. , Several of these processes mimic enzymatic transformations of sugars that have been shown to proceed through radical mechanisms . In general, the pathway for the synthetic catalyst systems involves an electron transfer between the excited-state photocatalyst and HAT co-catalyst, which generates a radical from the latter species.…”

Section: Introductionmentioning

confidence: 99%

Understanding the Origins of Site Selectivity in Hydrogen Atom Transfer Reactions from Carbohydrates to the Quinuclidinium Radical Cation: A Computational Study

2023

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The use of quinuclidine as a hydrogen atom transfer (HAT) mediator, along with a light-absorbing photoredox catalyst, has proved to be a powerful and general approach for achieving site-selective radical formation from carbohydrate substrates. Despite numerous literature reports documenting the scope and limitations of such processes, a general rationale for the origins of site selectivity in the key HAT step has not been advanced. In this study, density functional theory calculations (M06-2X/def2-TZVP/PCM(acetonitrile)) were used to model transition states for HAT to the quinuclidinium radical cation from pyranosides and furanosides having various configurations and substitution patterns. The data set (>120 transition state geometries and energies) has allowed for a detailed examination of the factors that influence the relative rates, augmented by additional analysis using the atoms in molecules (AIM) and distortion/interaction–activation strain frameworks. The trends that have emerged regarding the effects of configuration, conformation, substitution, and noncovalent interactions are consistent with experimental observations and reveal a key role for C–H···O hydrogen bonds in stabilizing transition states for HAT to the quinuclidinium radical cation.

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Section: Introductionmentioning

confidence: 99%

Understanding the Origins of Site Selectivity in Hydrogen Atom Transfer Reactions from Carbohydrates to the Quinuclidinium Radical Cation: A Computational Study

2023

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“…This could, in principle, be explained based upon stability grounds of the products, Dudding, Lectka and co-workers reported that fluorinated cyclic acetals (137.2) are not only stable, but can also be accessed via a HAT/Selectfluor manifold in excellent site-selectivity (Scheme 137A). 548 In the presence of xanthone and compact fluorescent light irradiation, N-radical dications 404 promoted the hydrogen-atom abstraction process with sugar acetonides, 363 such as of fructose, glucose, mannose and galactose. The nonketal α-oxy positions, for instance in galactose diacetonide or triamcinolone acetonide derivative, remained unaffected.…”

Section: Late-stage C(sp 3 )−C(sp) Bond Formationmentioning

confidence: 99%

“…The chemical similarity of the secondary hydroxy groups renders their selective functionalization, while of high interest, prohibitive. 363 As MacMillan beautifully highlighted (Scheme 87A), 346 hydrogen-bond interactions can override the formation of the more stable anomeric α,α′-oxy radical and elicit a preference for the primary α-hydroxy C−H bond. Based on the same catalytic system, Witte, Minnaard, and co-workers achieved the C3 selective αalkylation of unprotected carbohydrates (90.1) with complete equatorial selectivity (Scheme 90A).…”

Section: Late-stage Alkenyl C(sp 2 )−H Functionalizationmentioning

confidence: 99%

“…Particularly, positions other than the anomeric and the primary hydroxyl are difficult to target. The chemical similarity of the secondary hydroxy groups renders their selective functionalization, while of high interest, prohibitive . As MacMillan beautifully highlighted (Scheme A), hydrogen-bond interactions can override the formation of the more stable anomeric α,α′-oxy radical and elicit a preference for the primary α-hydroxy C–H bond.…”

Section: Late-stage Aliphatic C(sp3)–h Bond Functionalizationmentioning

confidence: 99%

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Photocatalytic Late-Stage C–H Functionalization

et al. 2023

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The emergence of modern photocatalysis, characterized by mildness and selectivity, has significantly spurred innovative late-stage C–H functionalization approaches that make use of low energy photons as a controllable energy source. Compared to traditional late-stage functionalization strategies, photocatalysis paves the way toward complementary and/or previously unattainable regio- and chemoselectivities. Merging the compelling benefits of photocatalysis with the late-stage functionalization workflow offers a potentially unmatched arsenal to tackle drug development campaigns and beyond. This Review highlights the photocatalytic late-stage C–H functionalization strategies of small-molecule drugs, agrochemicals, and natural products, classified according to the targeted C–H bond and the newly formed one. Emphasis is devoted to identifying, describing, and comparing the main mechanistic scenarios. The Review draws a critical comparison between established ionic chemistry and photocatalyzed radical-based manifolds. The Review aims to establish the current state-of-the-art and illustrate the key unsolved challenges to be addressed in the future. The authors aim to introduce the general readership to the main approaches toward photocatalytic late-stage C–H functionalization, and specialist practitioners to the critical evaluation of the current methodologies, potential for improvement, and future uncharted directions.

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“…Conversely, visible light photoredox catalysis emerged as a mild and operationally simple approach for the preparation of a wide variety of modified C -glycosides. 16 For non-anomeric saccharides, N -hydroxyphthalimide-derived (NHP) redox-active esters have recently been used as effective glycosyl radical precursors in both electron donor–acceptor complex (EDA) 17 a and single electron transfer (SET) 17 b strategies for C(sp 3 )–H glycosylation, affording a variety of C -glycoamino acids and glycopeptides (Scheme 1B).…”

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confidence: 99%

Synthesis of non-anomeric C-glycosyl pyrazolidinone derivatives via visible-light photoredox catalysis

Paixão¹,

Gonçalves²,

Oliveira³

et al. 2023

Org. Biomol. Chem.

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

Cited by 31 publications

References 221 publications

Understanding the Origins of Site Selectivity in Hydrogen Atom Transfer Reactions from Carbohydrates to the Quinuclidinium Radical Cation: A Computational Study

Understanding the Origins of Site Selectivity in Hydrogen Atom Transfer Reactions from Carbohydrates to the Quinuclidinium Radical Cation: A Computational Study

Photocatalytic Late-Stage C–H Functionalization

Synthesis of non-anomeric C-glycosyl pyrazolidinone derivatives via visible-light photoredox catalysis

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