Two New Retigerane‐Type Sesterterpenoids from the Lichen <i>Leprocaulon microscopicum</i>

Millot, Marion; Martin-de-Lassalle, Marie; Chollet-Krugler, Marylène; Champavier, Yves; Mambu, Lengo; Chulia, José-Albert; Lacaille‐Dubois, Marie‐Aleth

doi:10.1002/hlca.201500225

Cited by 10 publications

(1 citation statement)

References 20 publications

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“…The unique structure of retigeranic acid has attracted widespread attention, , and a number of synthetic studies on retigeranic acid have been reported. − In contrast, there have been few reports on its biosynthesis, though two plausible biosynthetic pathways have been proposed (Scheme ). ,, Shibata and co-workers proposed Route 1 . In this route, dissociation of the pyrophosphate of geranylfarnesyl diphosphate ( GFPP ) and sequential annulations (A-ring formation) yield a 5/15 bicyclic intermediate ( i ), which undergoes 1,5-hydrogen (H) shift to afford an allylic carbocation ( ii ).…”

mentioning

confidence: 99%

DFT Study on Retigerane-Type Sesterterpenoid Biosynthesis: Initial Conformation of GFPP Regulates Biosynthetic Pathway, Ring-Construction Order and Stereochemistry

Watanabe,

Hashishin,

Sato

et al. 2024

JACS Au

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Retigerane-type sesterterpenoids, which feature a unique 5/6/5/5/5 fused pentacyclic structure with an angular-type triquinane moiety, are biosynthesized via successive carbocationmediated reactions triggered by terpene cyclases. However, the precise biosynthetic pathways/mechanisms, wherein steric inversion of the carbon skeleton occurs at least once, remain elusive. Two plausible reaction pathways have been proposed, which differ in the order of ring cyclization: A → B/C → D/E-ring(s) (Route 1) and A → E → B → C/D-ring(s) (Route 2). Since the reaction intermediates of these complicated domino-type reaction sequences are experimentally inaccessible, we employed comprehensive density functional theory (DFT) calculations to evaluate these routes. The results indicate that retigeranin biosynthesis proceeds via Route 2 involving a multistep carbocation cascade, in which the order of ring cyclization (A → E → B → C/D) is the key to constructing the angular 5/5/5 triquinane structure with the correct stereochemistry at C3. The result also suggests that slight differences in the initial conformation have a significant effect on the order of cyclization and steric inversion. The computed pathway/mechanism also provides a rational basis for the formation of various related terpenes/terpenoids.

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mentioning

confidence: 99%

DFT Study on Retigerane-Type Sesterterpenoid Biosynthesis: Initial Conformation of GFPP Regulates Biosynthetic Pathway, Ring-Construction Order and Stereochemistry

Watanabe,

Hashishin,

Sato

et al. 2024

JACS Au

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Computational Studies on Biosynthetic Carbocation Rearrangements Leading to Quiannulatene: Initial Conformation Regulates Biosynthetic Route, Stereochemistry, and Skeleton Type

et al. 2018

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The results of quantum chemical calculations on the mechanism of the carbocation cascade of reactions in the biosynthetic pathways leading to the pentacyclic sesterterpenes quiannulatene and sesterfisherol provide reasonable answers to several persistent mechanistic questions in sesterterpene biosynthesis, including: 1) the reaction pathways of the multicyclic ring system construction and skeletal rearrangements, 2) the mechanism of triquinane skeleton formation, which requires more complicated rearrangements than previously proposed, 3) the stereochemistry of the final carbocation intermediate, and 4) the determining factor of biosynthetic selection for either 5/6/4/6/5 or 5/6/5/5/5 pentacyclic skeleton formation. This in‐depth mechanistic study on sesterterpene biosynthesis revealed that the shape of the final product and the type of triquinane skeleton formed are regulated by the stereochemistry and conformation of the common starting material, geranylfarnesyl diphosphate (GFPP).

show abstract

Computational Studies on Biosynthetic Carbocation Rearrangements Leading to Quiannulatene: Initial Conformation Regulates Biosynthetic Route, Stereochemistry, and Skeleton Type

et al. 2018

View full text Add to dashboard Cite

The results of quantum chemical calculations on the mechanism of the carbocation cascade of reactions in the biosynthetic pathways leading to the pentacyclic sesterterpenes quiannulatene and sesterfisherol provide reasonable answers to several persistent mechanistic questions in sesterterpene biosynthesis, including: 1) the reaction pathways of the multicyclic ring system construction and skeletal rearrangements, 2) the mechanism of triquinane skeleton formation, which requires more complicated rearrangements than previously proposed, 3) the stereochemistry of the final carbocation intermediate, and 4) the determining factor of biosynthetic selection for either 5/6/4/6/5 or 5/6/5/5/5 pentacyclic skeleton formation. This in-depth mechanistic study on sesterterpene biosynthesis revealed that the shape of the final product and the type of triquinane skeleton formed are regulated by the stereochemistry and conformation of the common starting material, geranylfarnesyl diphosphate (GFPP).

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Two New Retigerane‐Type Sesterterpenoids from the Lichen Leprocaulon microscopicum

Cited by 10 publications

References 20 publications

DFT Study on Retigerane-Type Sesterterpenoid Biosynthesis: Initial Conformation of GFPP Regulates Biosynthetic Pathway, Ring-Construction Order and Stereochemistry

DFT Study on Retigerane-Type Sesterterpenoid Biosynthesis: Initial Conformation of GFPP Regulates Biosynthetic Pathway, Ring-Construction Order and Stereochemistry

Computational Studies on Biosynthetic Carbocation Rearrangements Leading to Quiannulatene: Initial Conformation Regulates Biosynthetic Route, Stereochemistry, and Skeleton Type

Computational Studies on Biosynthetic Carbocation Rearrangements Leading to Quiannulatene: Initial Conformation Regulates Biosynthetic Route, Stereochemistry, and Skeleton Type

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