Divergent Total Synthesis of the Tricyclic Marine Alkaloids Lepadiformine, Fasicularin, and Isomers of Polycitorols by Reagent‐Controlled Diastereoselective Reductive Amination

In, Jinkyung; Lee, Seokwoo; Kwon, Yongseok; Kim, Sanghee

doi:10.1002/chem.201404316

Cited by 31 publications

(11 citation statements)

References 76 publications

(56 reference statements)

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“…Subsequent Wittig olefination by the treatment of 4a and 4b with in situ formed methylenetriphenylphosphorane afforded the desired terminal alkenes 5a and 5b , respectively. Ring-closing metathesis (RCM) with the second-generation Grubbs catalyst at low concentration successfully transformed 5a and 5b into cyclohexa-1,3-dienes 6a and 6b . Hydrogenation of the C–C double bonds and hydrogenolysis to remove the O -benzyl-protecting group enabled by Pd(OH) 2 /C catalysis, and followed by reduction of the amide functionality with lithium aluminum hydride (LiAlH 4 ), gave amines 7a and 7b .…”

Section: Resultsmentioning

confidence: 99%

Nucleophile-Dependent Z/E- and Regioselectivity in the Palladium-Catalyzed Asymmetric Allylic C–H Alkylation of 1,4-Dienes

et al. 2019

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The asymmetric allylic alkylation (AAA), which features employing active allylic substrates, has historical significance in organic synthesis. The allylic C−H alkylation is principally more atom-and step-economic than the classical allylic functionalizations and thus can be considered a transformative variant. However, asymmetric allylic C−H alkylation reactions are still scarce and yet underdeveloped. Herein, we have found that Z/E-and regioselectivities in the Pd-catalyzed asymmetric allylic C−H alkylation of 1,4-dienes are highly dependent on the type of nucleophiles. A highly stereoselective allylic C−H alkylation of 1,4-dienes with azlactones has been established by palladium-chiral phosphoramidite catalysis. The protocol proceeds under mild conditions and can accommodate a wide scope of substrates, delivering structurally divergent α,αdisubstituted α-amino acid surrogates in high yields and excellent levels of diastereo-, Z/E-, regio-, and enantioselectivities. Notably, this method provides key chiral intermediates for an efficient synthesis of lepadiformine marine alkaloids. Experimental and computational studies on the reaction mechanism suggest a novel concerted proton and two-electron transfer process for the allylic C−H cleavage and reveal that the Z/E-and regioselectivities are governed by the geometry and coordination pattern of nucleophiles.

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Section: Resultsmentioning

confidence: 99%

Nucleophile-Dependent Z/E- and Regioselectivity in the Palladium-Catalyzed Asymmetric Allylic C–H Alkylation of 1,4-Dienes

et al. 2019

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“…To this end, the sterically hindered tert -butyl ester group of 13 was first reduced with LiAlH 4 to the corresponding primary alcohol (Scheme ). We successfully converted the hydroxymethyl group of 14 to the allyl group in 16 via aziridinium intermediate 15 , the identity of which was confirmed by X-ray crystallography. The RCM of diene 16 was successfully performed with the Grubbs first generation catalyst, furnishing the azaspirocycle 17 .…”

mentioning

confidence: 88%

Total Synthesis and Structural Elucidation of (−)-Cephalezomine G

2019

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The first asymmetric synthesis and configurational elucidation of (−)-cephalezomine G was achieved. The highly functionalized Cα-substituted proline derivative was prepared from d-proline as the only chiral source via a C → N → C chirality transfer method consisting of stereoselective N-allylation and [2,3]-Stevens rearrangement. The azaspiranic tetracyclic backbone was constructed using ring-closing metathesis and the Friedel–Crafts reaction. Two contiguous hydroxyl groups were introduced in the later stages.

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“…In 2014, Kim and co-workers reported a divergent synthesis of these two natural products via a quinoline iminium salt 273 as the common intermediate (Scheme ). The key step of transforming starting material 268 into iminium salt 273 was the ester enolate Claisen rearrangement. Reagent-dependent stereoselective reduction of iminium salt 273 with NaCNBH 3 and l -selectride afforded 276 and 274 , respectively.…”

Section: Diversity From Different Redox Process Of Common Intermediatementioning

confidence: 99%

Divergent Strategy in Natural Product Total Synthesis

et al. 2018

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The divergent total syntheses of complex natural products from a common intermediate have attracted enormous attention in the chemical community in the past few years because it can improve the efficiency of chemical synthesis. A number of powerful and unified strategies have been developed by emulating the natural biosynthesis or through innovative transformations. This review focuses on the total synthesis of natural products by applying divergent strategies and the literature covering from 2013 to June 2017. On the basis of where the diversity comes from, the examples are grouped into three parts and discussed in detail. In each group, the examples that synthesize natural products belonging to the same subfamily are put together to contrast with one another.

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Divergent Total Synthesis of the Tricyclic Marine Alkaloids Lepadiformine, Fasicularin, and Isomers of Polycitorols by Reagent‐Controlled Diastereoselective Reductive Amination

Cited by 31 publications

References 76 publications

Nucleophile-Dependent Z/E- and Regioselectivity in the Palladium-Catalyzed Asymmetric Allylic C–H Alkylation of 1,4-Dienes

Nucleophile-Dependent Z/E- and Regioselectivity in the Palladium-Catalyzed Asymmetric Allylic C–H Alkylation of 1,4-Dienes

Total Synthesis and Structural Elucidation of (−)-Cephalezomine G

Divergent Strategy in Natural Product Total Synthesis

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