First example of samarium diiodide-promoted sequential cyclization and ring-expansion reactions of α-bromomethyl cyclic β-keto esters to homologated γ-keto esters

Hasegawa, Eietsu; Kitazume, T.; Suzuki, Kimihito; Tosaka, Emi

doi:10.1016/s0040-4039(98)00658-3

Cited by 45 publications

(12 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Recently, a mechanism on the ring-expansion of a-bromomethyl benzocyclic b-keto ester with SmI 2 has been proposed. 21 Although the reaction mechanism is not clear, there are two possible pathways. The first is a radical pathway similar to the tin induced radical ring expansion.…”

Section: Methodsmentioning

confidence: 99%

Facile Ring Expansions of α-Halomethyl β-Keto Esters Mediated with SmI2

Chung

Cho

Choi

et al. 2001

Synlett

View full text Add to dashboard Cite

show abstract

Section: Methodsmentioning

confidence: 99%

Facile Ring Expansions of α-Halomethyl β-Keto Esters Mediated with SmI2

Chung

Cho

Choi

et al. 2001

Synlett

View full text Add to dashboard Cite

show abstract

“…Ring expansion of the cyclohexenone moiety in ketone 2 was accomplished using the method reported by Hasegawa[21] to generate the requisite γ‐keto ester 20 . Compound 2 was converted to its corresponding β‐keto ester using Mander's reagent,[22] and subsequent iodomethylation[23] afforded iodide 19 in 75% yield as a single isomer.…”

Section: Total Synthesis Of (+)‐Allocyathin B2[14a]mentioning

confidence: 99%

“…The next task in the synthesis was to construct the [5‐6‐7] cyathane core from 27 , which required a one‐carbon ring‐expansion reaction. The ring‐expansion method described by Hasegawa[21] was employed because it had been successfully applied in our enantioselective total synthesis of (+)‐allocyathin B 2 [14a]. Therefore, 27 was converted to the corresponding β‐keto ester using Mander's reagent, and subsequent iodomethylation and treatment with samarium diiodide in the presence of HMPA gave the desired γ‐keto ester 31 in 42% yield over three steps.…”

Section: Total Synthesis Of (−)‐Erinacine B[14i]mentioning

confidence: 99%

Enantioselective Total Syntheses of Cyathane Diterpenoids

Nakada

2014

The Chemical Record

View full text Add to dashboard Cite

A Personal Account describing the enantioselective total syntheses of cyathane diterpenoids achieved in the Nakada group. A convergent approach to the cyathane scaffold, the [5-6-7] tricyclic carbon skeleton commonly found in cyathane diterpenoids, has been developed using the catalytic asymmetric intramolecular cyclopropanation (CAIMCP) and baker's yeast reduction. This approach has been successfully applied for the enantioselective total syntheses of (+)-allocyathin B2 , (-)-erinacine B, and (-)-erinacine E. The total synthesis of (-)-erinacine E has been achieved via the acyl group migratory intramolecular aldol reaction, which prevents the retro-aldol reaction and allows the construction of the strained structure. The highly efficient and stereoselective total syntheses of (-)-scabronines G, A, D, and (-)-episcabronine A have been achieved via the oxidative dearomatization/inverse electron demand Diels-Alder reaction cascade. Cascade reactions comprising three and five consecutive reactions were employed for the highly efficient total syntheses of (-)-scabronine A and (-)-episcabronine A, respectively.

show abstract

“…29 Upon exposure to SmI 2 in THF, alkyl iodide 75 is converted in 71% yield to the one-carbon ring expanded product 76 . This process smoothly forms the seven-membered C-ring, and thus completes the tricyclic cyathane core.…”

Section: Cyathane Total Synthesesmentioning

confidence: 99%

“…After dehydration, tricycle 94 was isolated as the major product of the reaction sequence. In seven additional steps ketone 94 was transformed into alkyl iodide 95 , an intermediate designed to undergo the samarium-mediated one-carbon ring expansion developed by Hasegawa and similar to that employed by Piers for the synthesis of Sarcodonin G (Scheme 17, Section 5.3) 29. When 95 was exposed to SmI 2 in the presence of HMPA, the expected migratory ring-expansion occurred in excellent yield to generate the completed cyathane core structure in the form of γ-keto ester 96 .…”

Section: Cyathane Total Synthesesmentioning

confidence: 99%

Synthetic efforts toward cyathane diterpenoid natural products

Enquist

Stoltz

2009

Nat. Prod. Rep.

View full text Add to dashboard Cite

An overview of synthetic efforts toward cyathane diterpenoid natural products from the year 2000 to present is provided. The emphasis of this review is the various ring-constructing and stereoforming strategies employed in these synthetic routes. 1 Introduction 2 Overview of the cyathane diterpenoids 2.1 Isolation 2.2 Bioactivity 2.3 Biosynthesis 3 Strategy summary 4 Cyathane core syntheses 4.1 Wender's cyathane core synthesis 4.2 Desma€ ele's cyathane core synthesis 4.3 Takeda's cyathane core synthesis 5Cyathane total syntheses 5.1 Snider's (AE)-allocyathin B 2 and (+)-erinacine A 5.2 Tori's (AE)-allocyathin B 2 5.3 Piers' (AE)-sarcodonin G 5.4 Ward's (AE)-allocyathin B 3 5.5 Ward's (À)-cyathin A 3 5.6 Nakada's (+)-allocyathin B 2 5.7 Nakada's (À)-erinacine B 5.8 Nakada's (À)-erinacine E 5.9 Trost's (+)-allocyathin B 2 5.10 Danishefsky's (À)-scabronine G 5.11 Phillip's (+)-cyanthiwigin U, (+)-cyanthiwigin W, and (À)-cyanthiwigin Z 5.12 Reddy's (+)-cyanthiwigin AC 5.13 Stoltz's (À)-cyanthiwigin F 6 Conclusions 7 Acknowledgements 8 References

show abstract

First example of samarium diiodide-promoted sequential cyclization and ring-expansion reactions of α-bromomethyl cyclic β-keto esters to homologated γ-keto esters

Cited by 45 publications

References 16 publications

Facile Ring Expansions of α-Halomethyl β-Keto Esters Mediated with SmI2

Facile Ring Expansions of α-Halomethyl β-Keto Esters Mediated with SmI2

Enantioselective Total Syntheses of Cyathane Diterpenoids

Synthetic efforts toward cyathane diterpenoid natural products

Contact Info

Product

Resources

About