SmI<sub>2</sub>-Mediated Couplings of α-Amino Acid Derivatives. Formal Synthesis of (−)-Pumiliotoxin 251D and (±)-Epiquinamide

Pinho, Vagner D.; Procter, David J.; Burtoloso, Antonio C. B.

doi:10.1021/ol400903n

Cited by 25 publications

(13 citation statements)

References 52 publications

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“…7 For example, a [3 + 1] type intermolecular cycloaddition reaction based on the generation of carbon radicals using a strong single-electron reductant such as SmI 2 was reported by Fukuzawa and Procter (Scheme 1, middle). 8 Furthermore, various intermolecular [2 + 2] type reactions such as the C–C/C–O bond formation of an alkene with an acetyl unit have also been investigated. Among them is a common and powerful method based on the generation of carbon radicals in a one-electron oxidation process using heavy metals (Scheme 1, bottom).…”

Section: Introductionmentioning

confidence: 99%

trans-Diastereoselective Syntheses of γ-Lactones by Visible Light-Iodine-Mediated Carboesterification of Alkenes

2019

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This study aims to develop an intermolecular lactonization reaction of alkenes with carbonyls mediated by visible light and molecular iodine. The one-step reaction involved the carboesterification of alkenes to produce the corresponding lactones in moderate to good yield. It was also revealed that it is possible to control the diastereoselectivity of the reaction by altering the base used and the reaction conditions. When water was added as a solvent, the reaction resulted in the formation of lactones with trans-selectivity. A mechanistic investigation was undertaken and it was found that the reaction requires the generation of an iodine radical from molecular iodine, driven by visible light irradiation, and proceeds via the formation of an iodine radical alkene adduct. The proposed reaction is an example of a rare-metal free intermolecular addition cyclization reaction, which is an environment-friendly chemical process that only uses molecular iodine. In addition, since diastereoselectivity was observed without the use of any specific reagents, the developed methodology is an example of a novel stereoselective transformation using only cost-effective reagents.

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Section: Introductionmentioning

confidence: 99%

trans-Diastereoselective Syntheses of γ-Lactones by Visible Light-Iodine-Mediated Carboesterification of Alkenes

2019

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“…Reduction of the double bond and the N−O bond using Pd/C in methanol under H 2 atmosphere gave the lactone 11 (Scheme ). The lactone 11 has already been used for the synthesis of Pumilotoxin 251D and other indolizidine alkaloids ,,…”

Section: Resultsmentioning

confidence: 99%

Synthesis of 1‐Deoxy‐8,8a–di–epi–castanospermine, 1‐Deoxy‐6,7,8a–tri–epi–castanospermine and Formal Synthesis of Pumilotoxin 251D

Chacko

Ramapanicker

2016

ChemistrySelect

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An efficient synthesis of 1‐deoxy‐8,8a‐di‐epi‐castanospermine and 1‐deoxy‐6,7,8a‐tri‐epi‐castanospermine through the use of proline‐catalyzed asymmetric α‐aminoxylation of an N‐Boc derivative of L‐homoprolinal is reported. The configuration of the proline catalyst used for the asymmetric aminoxylation step ultimately controls the absolute configuration of three adjacent stereogenic centers in the final products. The method is also used to achieve a formal synthesis of Pumilotoxin 251D.

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“…Interestingly, Burtoloso recently engaged a related group of α-aminocarbonyl substrates in the intermolecular cross-coupling with methyl acrylate to form γ-aminomethyl-γ-butyrolactones using SmI 2 /H 2 O ( Scheme 16 A) [ 70 ]. The reaction proceeds in high yields and with excellent diastereoselectivity.…”

Section: Synthesis Of Nitrogen Heterocycles Via Fragmentation/cyclmentioning

confidence: 99%

Synthesis of Nitrogen Heterocycles Using Samarium(II) Iodide

Shi

Szostak

2017

Molecules

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Nitrogen heterocycles represent vital structural motifs in biologically-active natural products and pharmaceuticals. As a result, the development of new, convenient and more efficient processes to N-heterocycles is of great interest to synthetic chemists. Samarium(II) iodide (SmI2, Kagan’s reagent) has been widely used to forge challenging C–C bonds through reductive coupling reactions. Historically, the use of SmI2 in organic synthesis has been focused on the construction of carbocycles and oxygen-containing motifs. Recently, significant advances have taken place in the use of SmI2 for the synthesis of nitrogen heterocycles, enabled in large part by the unique combination of high reducing power of this reagent (E1/2 of up to −2.8 V) with excellent chemoselectivity of the reductive umpolung cyclizations mediated by SmI2. In particular, radical cross-coupling reactions exploiting SmI2-induced selective generation of aminoketyl radicals have emerged as concise and efficient methods for constructing 2-azabicycles, pyrrolidines and complex polycyclic barbiturates. Moreover, a broad range of novel processes involving SmI2-promoted formation of aminyl radicals have been leveraged for the synthesis of complex nitrogen-containing molecular architectures by direct and tethered pathways. Applications to the synthesis of natural products have highlighted the generality of processes and the intermediates accessible with SmI2. In this review, recent advances involving the synthesis of nitrogen heterocycles using SmI2 are summarized, with a major focus on reductive coupling reactions that enable one-step construction of nitrogen-containing motifs in a highly efficient manner, while taking advantage of the spectacular selectivity of the venerable Kagan’s reagent.

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SmI₂-Mediated Couplings of α-Amino Acid Derivatives. Formal Synthesis of (−)-Pumiliotoxin 251D and (±)-Epiquinamide

Cited by 25 publications

References 52 publications

trans-Diastereoselective Syntheses of γ-Lactones by Visible Light-Iodine-Mediated Carboesterification of Alkenes

trans-Diastereoselective Syntheses of γ-Lactones by Visible Light-Iodine-Mediated Carboesterification of Alkenes

Synthesis of 1‐Deoxy‐8,8a–di–epi–castanospermine, 1‐Deoxy‐6,7,8a–tri–epi–castanospermine and Formal Synthesis of Pumilotoxin 251D

Synthesis of Nitrogen Heterocycles Using Samarium(II) Iodide

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SmI2-Mediated Couplings of α-Amino Acid Derivatives. Formal Synthesis of (−)-Pumiliotoxin 251D and (±)-Epiquinamide

Cited by 25 publications

References 52 publications

trans-Diastereoselective Syntheses of γ-Lactones by Visible Light-Iodine-Mediated Carboesterification of Alkenes

trans-Diastereoselective Syntheses of γ-Lactones by Visible Light-Iodine-Mediated Carboesterification of Alkenes

Synthesis of 1‐Deoxy‐8,8a–di–epi–castanospermine, 1‐Deoxy‐6,7,8a–tri–epi–castanospermine and Formal Synthesis of Pumilotoxin 251D

Synthesis of Nitrogen Heterocycles Using Samarium(II) Iodide

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SmI₂-Mediated Couplings of α-Amino Acid Derivatives. Formal Synthesis of (−)-Pumiliotoxin 251D and (±)-Epiquinamide