Synthetic Approaches to Natural and Unnatural Tetraquinanes

Kotha, Sambasivarao; Fatma, Ambareen

doi:10.1002/ajoc.202100595

Cited by 7 publications

(5 citation statements)

References 75 publications

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“…Cyclopentanoids consists of fused cyclopentane rings which can be further classified as di-, tri-, [1] tetra-, [2][3][4][5][6] and pentaquinane etc. based on the number of cyclopentane rings fused in a specific entity.…”

Section: Introductionmentioning

confidence: 99%

Linear Tetraquinanes by Microwave Assisted [3+2] Cycloaddition and Ring‐Rearrangement Metathesis

Kotha

Agrawal

2023

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Herein, an improved synthetic strategy to linear tetraquinanes is reported via a [3 + 2] cycloaddition and ring-rearrangement metathesis as key steps. The linear tetraquinanes reported earlier were synthesized in a nine step sequence with an overall yield of 9 % while the same tetraquinanes are now prepared in four steps with a 3-fold increase in overall yield of 29 %. Failure of the conventional [3 + 2] cycloaddition using allyltriisopropyl-silane was overcome by using microwave irradiation (MWI) conditions which is performed for the first time for this purpose. The strategy reported here does not involve any protection and deprotection steps and can be helpful for the synthesis of polyquinane based natural products and synthesis of medicinally important targets.

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Section: Introductionmentioning

confidence: 99%

Linear Tetraquinanes by Microwave Assisted [3+2] Cycloaddition and Ring‐Rearrangement Metathesis

Kotha

Agrawal

2023

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“…Crinipellins A ( 1 ), B ( 2 ), and related natural congeners (cf. 3 - 7 ) belong to the polyquinane diterpene natural products (Scheme A) . Crinipellins A and B were isolated by Steglich and co-workers from the fungus Crinipellis stipitaria (Agaricales) .…”

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Concise Total Syntheses of (−)-Crinipellins A and B Enabled by a Controlled Cargill Rearrangement

Xu,

Zhang,

Tantillo

et al. 2024

J. Am. Chem. Soc.

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Herein, we report concise total syntheses of diterpene natural products (−)-crinipellins A and B with a tetraquinane skeleton, three adjacent all-carbon quaternary centers, and multiple oxygenated and labile functional groups. Our synthesis features a convergent Kozikowski β-alkylation to unite two readily available building blocks with all the required carbon atoms, an intramolecular photochemical [2 + 2] cycloaddition to install three challenging and adjacent all-carbon quaternary centers and a 5− 6−4−5 tetracyclic skeleton, and a controlled Cargill rearrangement to rearrange the 5−6−4−5 tetracyclic skeleton to the desired tetraquinane skeleton. These strategically enabling transformations allowed us to complete total syntheses of (−)-crinipellins A and B in 12 and 13 steps, respectively. The results of quantum chemical computations revealed that the Bronsted acid-catalyzed Cargill rearrangements likely involve stepwise paths to products and the AlR 3 -catalyzed Cargill rearrangements likely involve a concerted path with asynchronous alkyl shifting events to form the desired product.

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“…Polyquinanes, consisting of fused five-membered rings in diverse connection patterns, belong to an important class of carbocyclic skeletons prominent in terpenoids and steroids . Besides intriguing biological properties, these molecules continue to attract attention from the synthetic community due to their congested architectures and overall stereochemical complexity, which have stimulated a number of innovative tactics and methodologies toward the construction of the core structures.…”

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Total Synthesis of (−)-Retigeranic Acid A: A Reductive Skeletal Rearrangement Strategy

et al. 2023

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The asymmetric total synthesis of (−)-retigeranic acid A was described, which relies on a crucial reductive skeletal rearrangement cascade for the controllable assembly of diverse angular triquinane subunits. Taken together with an intramolecular Michael/aldol cyclization, an ODI-[5 + 2] cycloaddition/pinacol rearrangement cascade, a Wolff ring contraction and a stereoselective HAT reduction, our synthetic approach has enabled the access to (−)-retigeranic acid A in a concise and practical manner.

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Synthetic Approaches to Natural and Unnatural Tetraquinanes

Abstract: Dedicated to Prof. J. M. Cook in appreciation of his contribution to polyquinane area.

Cited by 7 publications

References 75 publications

Linear Tetraquinanes by Microwave Assisted [3+2] Cycloaddition and Ring‐Rearrangement Metathesis

Linear Tetraquinanes by Microwave Assisted [3+2] Cycloaddition and Ring‐Rearrangement Metathesis

Concise Total Syntheses of (−)-Crinipellins A and B Enabled by a Controlled Cargill Rearrangement

Total Synthesis of (−)-Retigeranic Acid A: A Reductive Skeletal Rearrangement Strategy

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