Total synthesis of complex terpenoids employing radical cascade processes

Hung, Kevin; Hu, Xirui; Maimone, Thomas J.

doi:10.1039/c7np00065k

Cited by 149 publications

(66 citation statements)

References 198 publications

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“…[1][2][3][4] The unique combination of high reactivity and high selectivity associated with open-shell intermediates makes radical processes 5,6 ideal for cascade reactions in which simple substrates undergo a series of changes involving bond formation (and bond cleavage) to give complex, high value products and single electron transfer (SET) is commonly used to generate the radical character that drives such processes. [7][8][9] The well-known reductant samarium(II) diiodide (SmI 2 , Kagan's reagent) 10 is arguably one the most important and widely used SET reagents 11,12 and it has proved adept at unlocking the total synthesis of numerous high profile and complex natural products (Fig. 1A).…”

Section: Introductionmentioning

confidence: 99%

SmI2-catalysed cyclization cascades by radical relay

2019

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Radical cyclization cascades are powerful tools used to construct the complex three-dimensional structures of some of society's most prized molecules. Since its first use forty years ago, SmI 2 has been used extensively for reductive radical cyclizations. Unfortunately, SmI 2 must almost always be used in significant excess thus raising issues of cost and waste. Here we have developed radical cyclization cascades that are catalyzed by SmI 2 and that exploit a radical relay/electron-catalysis strategy. The approach negates the need for a super-stoichiometric co-reductant and requires no additives. Complex cyclic products, including products of dearomatization, containing up to four contiguous stereocenters are obtained in excellent yield. Mechanistic studies support a single-electron transfer radical mechanism. Our strategy provides a long-awaited solution to the problem of how to avoid the need for stoichiometric amounts of SmI 2 and establishes a conceptual platform upon which other catalytic radical processes using the ubiquitous reducing agent can be built.

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Section: Introductionmentioning

confidence: 99%

SmI2-catalysed cyclization cascades by radical relay

2019

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“…Most importantly, C 2 -symmetric bis-THF B-RR was immediatelya ssembled from the simple carbohydrate derivative without damaging the preexisting oxygen functionalities. [12] We envisioned implementing this powerful, yet mild, radical dimerization for expeditious access to the central C 2 -symmetric bis-THF substructure of asimicin (1)( Scheme 1A). Thus, 1 was retrosynthetically simplified into C 2 -symmetric dimer 3-SS.…”

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confidence: 99%

Convergent Total Synthesis of Asimicin via Decarbonylative Radical Dimerization

Kawamata

Yamaguchi

Nagatomo

et al. 2018

Chemistry A European J

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Asimicin (1) exhibits potent antitumor activity and comprises a central C2‐symmetric bis‐tetrahydrofuran and two aliphatic side‐chains, one of which terminates with (S)‐methyl‐2(5H)‐furanone. This work reports a convergent total synthesis of 1 in 17 steps from d‐gulose derivative 4. Decarbonylative radical‐radial homo‐coupling of α‐alkoxyacyl telluride 12 a efficiently produced the C2‐symmetric core 3‐SS, which was transformed into 1 through stepwise attachment of the two side‐chains and functional group manipulations.

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“…[61][62][63][64][65][66] In general, radical approach [67][68][69][70][71][72] is widely applied in the field of organic synthesis for the rapid construction of complex molecular architectures [73][74][75] and the total synthesis of natural products under safe and mild conditions. [76][77][78][79][80][81] Even in nature many of oxidation processes catalyzed by heme proteins and metalloporphyrins have proceeded through a radical mechanism. [82] These attractive features are the reason why we focus in this review on the promising powerful and highly selective radical cross-coupling reactions which have been applied for the asymmetric synthesis of challenging unusual non-proteinogenic AAs.…”

Section: Introductionmentioning

confidence: 99%

Advances in Asymmetric Amino Acid Synthesis Enabled by Radical Chemistry

2020

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Chiral amino acids (AAs), being the main "building" blocks of the living organisms, are also an important class of organic compounds which broadly applied in synthetic chemistry, biochemistry, catalysis and the designing of new drugs. According to the industrial-commodity market, chiral non-proteinogenic AAs containing various functional groups come to the fore. To date, radical cross-coupling reactions are becoming an option as an attractive powerful tool for AA syntheses. Owing to mild reaction conditions and high functional-group tolerance, radical chemistry represents an ideal strategy for the synthesis of challenging complex non-proteinogenic AAs. Moreover, the radical cross-coupling allows introducing AA residue into drug scaffolds and natural compounds. In the present review, we wish to summarize and discuss all the reported to date methods of the asymmetric synthesis of AAs using radical chemistry by presenting a comprehensive account of the literature in this field going back to 1990. We especially emphasize on a radical chemistry approach and, exclusively, on stereoselective synthesis of various α-, β-, γ-AAs and derivatives employing a different type of radical initiators starting from AIBN and organostannes and ending with powerful photoredox catalysis. Furthermore, the mechanism of the reported reactions will be discussed. Radicals Generated from AA Derivatives in Conjugate Additions 6.1. Radicals Generated from α-Substituted Glycine Derivatives in AA Synthesis 6.2. Modification of Chiral AA Side Chain by Radical Chemistry 7.

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Total synthesis of complex terpenoids employing radical cascade processes

Cited by 149 publications

References 198 publications

SmI2-catalysed cyclization cascades by radical relay

SmI2-catalysed cyclization cascades by radical relay

Convergent Total Synthesis of Asimicin via Decarbonylative Radical Dimerization

Advances in Asymmetric Amino Acid Synthesis Enabled by Radical Chemistry

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