Total Synthesis of Colchicine. α-Methoxy-Substituted Oxyallyl [4 + 3] Cycloaddition Approach

Lee, Jae Chol; Jin, Sun; Kun, Jin

doi:10.1021/jo980220j

Cited by 63 publications

(19 citation statements)

References 15 publications

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“…Methylation of the parent tropolone is not regioselective and produces both colchicine and isocolchicine. Chas strategy [16] avoided this difficulty by placing the methyl group prior to formation of the tropolone. Cha constructed an annulated furan intermediate 42 and reacted it in a [4C+3C] cycloaddition reaction with silyl enolether 43.…”

Section: Scheme 7 Vinyl Cyclopropanes In [5c+2c] Annulation Reactionmentioning

confidence: 99%

The Cycloaddition Strategy for the Synthesis of Natural Products Containing Carbocyclic Seven‐Membered Rings

Battiste¹,

Pelphrey²,

Wright³

2006

Chemistry A European J

250

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Highly substituted carbocyclic seven-membered rings are frequently found in natural products and their synthesis represents a significant challenge to the synthetic chemist. Direct intramolecular cyclization of these systems often proves difficult and this fact has catalyzed the development of a variety of strategies based on a convergent intermolecular cycloaddition strategy. This concept article discusses the major cycloaddition approaches utilized to access these types of structures and primarily focuses on examples employed in the synthesis of natural products.

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Section: Scheme 7 Vinyl Cyclopropanes In [5c+2c] Annulation Reactionmentioning

confidence: 99%

The Cycloaddition Strategy for the Synthesis of Natural Products Containing Carbocyclic Seven‐Membered Rings

Battiste¹,

Pelphrey²,

Wright³

2006

Chemistry A European J

250

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“…249 Cha applied this method to the synthesis of colchicine 250–251 and tropoloisoquinolines. 252 The key [4+3] cycloaddition between substituted furan 69-3 and silyl enol ether 69-1 was carried out in the presence of TMSOTf.…”

Section: Synthesis Of Naturally Occurring Tropones and Tropolonesmentioning

confidence: 99%

Synthesis of naturally occurring tropones and tropolones

et al. 2014

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Tropones and tropolones are an important class of seven-membered non-benzenoid aromatic compounds. They can be prepared directly by oxidation of seven-membered rings. They can also be derived from cyclization or cycloaddition of appropriate precursors followed by elimination or rearrangement. This review discusses the types of naturally occurring tropones and tropolones and outlines important methods developed for the synthesis of tropone and tropolone natural products.

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“…[15] Similarly, [4+3] cycloadditions between rhodium vinyl carbenoids [16] or a-methoxy-substituted oxyallyl derivatives and electron-rich dienes [17] allowed the direct construction of the seven-membered ring.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of 4‐Aminotropones from [(Sulfinyl or Sulfonyl)methyl]‐Substituted p‐Quinamines

Carreño¹,

Ortega-Guerra²,

Ribagorda³

et al. 2007

Chemistry A European J

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An efficient synthesis of 4-aminotropones has been achieved in excellent yields by simple treatment of 4-amino-4-[(p-tolylsulfinyl)methyl]-2,5-cyclohexadienones (p-quinamines) with NaH. The method allowed regiocontrolled access to 3-methyl, 5-methyl- and 3,5-dimethyl-substituted derivatives starting from p-quinamines with adequate substituents at the cyclohexadienone moiety and/or at the carbon linked to the sulfur function. The p-quinamines in turn were easily accessible from N-Boc p-anisidines (Boc=tert-butoxycarbonyl) by electrochemical oxidation in MeOH to quinone imine monoketals, followed by addition of a alpha-lithium sulfinyl carbanion to the imino group, and ketal hydrolysis. Oxidation of the sulfoxide gave the sulfonyl-substituted p-quinamines that, upon basic treatment, behave similarly. The p-quinamine 55 and bis-p-quinamine 56, resulting in the addition of the anion derived from dimethyl sulfone to the p-quinonimine ketal 14, also gave the 4-aminotropone. The mechanism involves the initial formation of a alpha-sulfonyl carbanion, which intramolecularly attacks the cyclohexadienone giving a norcaradiene-like enolate intermediate, the evolution of which through a ring-expansion process, pushes off a methyl sulfinate anion or SO2. This efficient process fulfils the criteria of atom economy. The introduction of a proline substituent in the nitrogen of the starting p-quinamine allowed the synthesis of an enantiopure 4-aminotropone, the asymmetric Diels-Alder reactions of which with maleimide occurred in a highly endo and pi-facial diastereoselective manner.

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Total Synthesis of Colchicine. α-Methoxy-Substituted Oxyallyl [4 + 3] Cycloaddition Approach

Cited by 63 publications

References 15 publications

The Cycloaddition Strategy for the Synthesis of Natural Products Containing Carbocyclic Seven‐Membered Rings

The Cycloaddition Strategy for the Synthesis of Natural Products Containing Carbocyclic Seven‐Membered Rings

Synthesis of naturally occurring tropones and tropolones

Synthesis of 4‐Aminotropones from [(Sulfinyl or Sulfonyl)methyl]‐Substituted p‐Quinamines

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