Synthesis of Natural Products with Polycyclic Systems

Yokoshima, Satoshi

doi:10.1248/cpb.c12-01031

Cited by 13 publications

(3 citation statements)

References 68 publications

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“…Polycyclic natural products and the underlying scaffolds display promising target structures for synthetic endeavors [1][2][3][4] and drug discovery. [5][6][7][8] Two fascinating examples are the clifednamides A-J 1a-e and spinosyn A and D 2a,b which are both of current synthetic interest (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

Chasing Polycyclic Natural Products: 5/6/5‐ or 5/6/6‐Carbotricyclic Scaffold Construction via Stereodivergent Diels‐Alder Reaction of Chiral Hydrindanes and Their Boron Complexes

et al. 2022

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Chiral trans-hydrindanes (bicyclo[4.3.0]nonanes) are important building blocks of polycyclic natural products. In order to access 5/6/5-and 5/6/6-carbotricyclic scaffolds scope and limitation of [4 + 2] cycloadditions of tetrahydroindanones with various dienes were studied. Cyclopentadiene gave a tetracylic endo-(R,R)-diastereomer under acid-catalysis, whereas thermal conditions provided the endo-(S,S)-diastereomer with the opposite diastereofacial selectivity. The stereodivergent outcome was rationalized by high-level quantum-chemical computations which revealed the acid-catalysis to be a kinetically controlled reaction and the thermal cycloaddition to be under thermody-namic control. Stereochemical assignment of the cycloadducts was facilitated by conversion of the 1,3-dicarbonyls with BF 3 • OEt 2 into BF 2 -chelate complexes. Subsequent thermal Diels-Alder reaction of BF 2 -or BBN-chelates (from 9-BBN-OTf) gave endo/exo-mixtures of the (R,R)-and (S,S)-diastereomers, while more elevated temperatures yielded primarily the endo/exo-(S,S)-diastereomers. Thermal [4 + 2] cycloadditions with 2,3dimethylbutadiene proceeded with lower diastereoselectivity as the reaction was kinetically controlled according to calculations. Attempted Diels-Alder-reactions with furan gave furyl-substituted indanones rather than cycloadducts.

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Section: Introductionmentioning

confidence: 99%

Chasing Polycyclic Natural Products: 5/6/5‐ or 5/6/6‐Carbotricyclic Scaffold Construction via Stereodivergent Diels‐Alder Reaction of Chiral Hydrindanes and Their Boron Complexes

et al. 2022

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“…A widely used method to access four-membered rings is the ring expansion of in situ generated cyclopropylmethyl cations via the Wagner–Meerwein rearrangement . One of the efficient ways of generating cyclopropylmethyl cations is using methylenecyclopropanes (MCPs) as precursors. − The MCP ring expansion can be directly triggered by transition-metal (such as Pt, Pd, and Au) coordination to the alkene part of MCPs .…”

Section: Introductionmentioning

confidence: 99%

Asymmetric Synthesis of Azepine-Fused Cyclobutanes from Yne-Methylenecyclopropanes Involving Cyclopropanation/C–C Cleavage/Wagner–Meerwein Rearrangement and Reaction Mechanism

2019

J. Org. Chem.

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Ring expansion of in situ generated cyclopropylmethyl cations via Wagner–Meerwein rearrangement to cyclobutanes is widely used in synthesis. However, the cyclopropylmethyl cations generated are planar, which would lead to loss of chiral information in the case of chiral precursors, making an asymmetric version of such ring expansion difficult. In the present work, a gold(I)-catalyzed asymmetric cyclopropanation/C–C cleavage/Wagner–Meerwein rearrangement of easily affordable yne-methylenecyclopropanes (1,6-yne-MCPs) has been developed to synthesize 3-azabicyclo[5.2.0]nonadiene, a bicyclic 7/4 ring (azepine fused with cyclobutane) with a bridgehead aryl substituent. This reaction overcomes the challenging loss of chirality from the Wagner–Meerwein rearrangement. Density functional theory calculations indicate that the chirality of the final product comes from the first cyclopropanation step in this reaction. The chirality in the resultant cyclopropane is lost in the following C–C cleavage step, generating rigid, planar cyclopropylmethyl carbocation intermediate. Then, only one carbon of the cyclopropyl group in the cyclopropylmethyl carbocation intermediate can migrate via ring expansion in the Wagner–Meerwein rearrangement process, and consequently, the chirality in the cyclopropane generated in the first step is transferred to the final product.

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“…Many natural products, pharmaceuticals, and bioactive molecules generally consist of complex indole units, and the chelation-assisted C–C σ bond amination strategy provides a possible access to directly reorganizing complex indole skeletons through a simple one-step process. Therefore, we initiated the study by employing 1-(2-pyridyl)-2-( n -butyryl)-3-phenylindole ( 1a ) as the model indolylalkylketone, TsN 3 ( A ) as the “N” source to screen different transition-metal catalysts (5 mol %) including Co(III), Mn(I), Ir(III), Rh(I), and Rh(III)-catalysts for exploring the direct Csp 2 –Csp 2 σ bond amination in 1.0 mL of 1,2-dichoroethane (DCE) under Ar atmosphere at 85 °C for 24 h (Table , entries 1–7).…”

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confidence: 99%

Direct Carbon–Carbon σ Bond Amination of Unstrained Arylalkylketones

Shao

Xie

et al. 2020

ACS Catal.

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Described herein is the development of an unprecedented approach to direct amination of unstrained aryl-ketone Csp2–Csp2 sigma bonds with sulfonylazides via Rh(III)-catalyzed Csp2–Csp2 cleavage. This methodology provides an efficient strategy for acyl groups/amino groups switch at the C2-position of indoles in a straightforward fashion. The combination of experimental and computational studies indicates that beta-aryl elimination derived from enole-based cyclorhodiumates is a key step, while the formation of rhodum nitrene is the rate-limiting process.

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Synthesis of Natural Products with Polycyclic Systems

Cited by 13 publications

References 68 publications

Chasing Polycyclic Natural Products: 5/6/5‐ or 5/6/6‐Carbotricyclic Scaffold Construction via Stereodivergent Diels‐Alder Reaction of Chiral Hydrindanes and Their Boron Complexes

Chasing Polycyclic Natural Products: 5/6/5‐ or 5/6/6‐Carbotricyclic Scaffold Construction via Stereodivergent Diels‐Alder Reaction of Chiral Hydrindanes and Their Boron Complexes

Asymmetric Synthesis of Azepine-Fused Cyclobutanes from Yne-Methylenecyclopropanes Involving Cyclopropanation/C–C Cleavage/Wagner–Meerwein Rearrangement and Reaction Mechanism

Direct Carbon–Carbon σ Bond Amination of Unstrained Arylalkylketones

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