Asymmetric Total Synthesis of Spirostanol Bufospirostenin A

Tong, Zhenzhong; Ding, Hanfeng

doi:10.6023/cjoc202000080

Cited by 3 publications

(2 citation statements)

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“…In light of its scarcity in nature (only 1.9 mg was isolated) and interesting biological properties, a concise, efficient synthetic approach to this unusual steroid and its analogues would be highly desirable. In 2020, Li and co-workers reported the first synthesis of 4 , via an elegant route that employed a remarkable rhodium-catalyzed Pauson–Khand reaction of an alkoxyallene-yne to construct the rearranged A/B ring system …”

Section: Introductionmentioning

confidence: 99%

Gram-Scale Synthesis of Bufospirostenin A by a Biomimetic Skeletal Rearrangement Approach

2021

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Bufospirostenin A, which was the first spirostanol to be isolated from an animal, possesses an unprecedented 5/7/6/5/5/ 6 hexacyclic framework. Herein, we report two biomimetic syntheses of this natural product in just seven or nine steps from a readily available steroidal lactone. Key features of the syntheses include a photosantonin rearrangement and a Wagner−Meerwein rearrangement for rapid construction of the rearranged A/B ring system, as well as a cobalt-mediated olefin hydroselenylation and a selenide E2 reaction to accomplish a challenging olefin transposition. Our syntheses provide experimental support for the biogenetic pathway to 5(10→1)abeo-steroids that we have proposed.

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Section: Introductionmentioning

confidence: 99%

Gram-Scale Synthesis of Bufospirostenin A by a Biomimetic Skeletal Rearrangement Approach

2021

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“…For the total synthesis of 1 , the development of an efficient method to construct the complex ring system with high stereoselectivity, regioselectivity, and enantioselectivity is a critical challenge. As part of our ongoing endeavor toward the total synthesis of bioactive natural products with a seven-membered ring, we reported herein an efficient strategy for the enantioselective total synthesis of cerorubenic acid-III, which was enabled by a type II [5+2] cycloaddition reaction.…”

Section: Introductionmentioning

confidence: 99%

Enantioselective Total Synthesis of Cerorubenic Acid-III via Type II [5+2] Cycloaddition Reaction

Liu

et al. 2021

J. Org. Chem.

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The first enantioselective total synthesis of cerorubenic acid-III is described in detail. Different strategies and attempts, based on a type II [5+2] cycloaddition reaction, leading to the bicyclo[4.4.1] ring system with a strained bridgehead double bond, are depicted. Furthermore, sodium naphthalenide was found to be efficient in the chemoselective reduction of 8oxabicyclo[3.2.1]octene, with three transformations completed in one operation. An unusual S N 1 transannular cyclization reaction was applied to construct the synthetically challenging vinylcyclopropane moiety. This strategy enabled the total synthesis of cerorubenic acid-III in 19 steps.

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Evolution of Routes for Asymmetric Total Synthesis of Cyclocitrinol Enabled by Type II [5+2] Cycloaddition^†

Liu

Fan

et al. 2021

Chin. J. Chem.

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The asymmetric total synthesis of an unusual C25 steroid containing a unique bicyclo[4.4.1]undecene A/B ring system, resulting in the synthesis of cyclocitrinol (1) and its isomer  8,14 -cyclocitrinol (38), is reported. Initial attempts to construct the synthetically challenging bicyclo[4.4.1]undecene A/B ring system using a type II [5+2] cycloaddition showed that a chiral substituent at the allylic position of the alkene (C6, cyclocitrinol numbering) controlled the stereoselective outcome of the cycloaddition reaction. Late-stage migration of the tetrasubstituted C8-C14 double bond in  8,14 -cyclocitrinol ( 38) to obtain cyclocitrinol (1) proved challenging, inspiring an alternative approach. The chiral β-CH 2 OR group on the allylic substituent at C6 played a pivotal role both in controlling the diastereoselectivity of the type II [5+2] cycloaddition and retaining the C6 substituent under lithium-amine conditions.

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Asymmetric Total Synthesis of Spirostanol Bufospirostenin A

Cited by 3 publications

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Gram-Scale Synthesis of Bufospirostenin A by a Biomimetic Skeletal Rearrangement Approach

Gram-Scale Synthesis of Bufospirostenin A by a Biomimetic Skeletal Rearrangement Approach

Enantioselective Total Synthesis of Cerorubenic Acid-III via Type II [5+2] Cycloaddition Reaction

Evolution of Routes for Asymmetric Total Synthesis of Cyclocitrinol Enabled by Type II [5+2] Cycloaddition^†

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Asymmetric Total Synthesis of Spirostanol Bufospirostenin A

Cited by 3 publications

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Gram-Scale Synthesis of Bufospirostenin A by a Biomimetic Skeletal Rearrangement Approach

Gram-Scale Synthesis of Bufospirostenin A by a Biomimetic Skeletal Rearrangement Approach

Enantioselective Total Synthesis of Cerorubenic Acid-III via Type II [5+2] Cycloaddition Reaction

Evolution of Routes for Asymmetric Total Synthesis of Cyclocitrinol Enabled by Type II [5+2] Cycloaddition†

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Evolution of Routes for Asymmetric Total Synthesis of Cyclocitrinol Enabled by Type II [5+2] Cycloaddition^†