Structure, biosynthetic relationships and chemical synthesis of the icetexane diterpenoids

Simmons, Eric M.; Sarpong, Richmond

doi:10.1039/b908984e

Cited by 79 publications

(76 citation statements)

References 81 publications

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“…[11] These compounds exhibit aunique carbon skeleton consisting of a6 -7-6 tricyclic core structure ( Figure 2). [11] These compounds exhibit aunique carbon skeleton consisting of a6 -7-6 tricyclic core structure ( Figure 2).…”

Section: Resultsmentioning

confidence: 99%

“…The systematic name 9(10!20)-abeo-abietane given to icetexanes indicates that an abietanep recursor such as 4 could be involved in the biosynthetic origin of icetexanes (Scheme 3). [11] Scheme3.Hypothetical biogeneticabietane ring expansion to icetexanes. [13] Hydride abstraction from the angular methyl group (X = H) or solvolysis of the primary alcohol (X = OH) of abietane 4 generates ap rimary cation that can immedi- Examples of icetexane natural products.…”

Section: Resultsmentioning

confidence: 99%

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Collective Syntheses of Icetexane Natural Products Based on Biogenetic Hypotheses

Thommen

Neuburger

Gademann

2016

Chemistry A European J

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A divergent synthesis of 10 icetexane natural products based on a proposed biogenetic cationic ring expansion of a reduced carnosic acid derivative is described. Of these icetexanes, (+)-salvicanol, (-)-cyclocoulterone, (-)-coulterone, (-)-obtusinone D, and (-)-obtusinone E have been synthesized for the first time. In addition, the hypothesis for the non-enzymatic biogenesis of benzo[1,3]dioxole natural products has been experimentally investigated. Additional experimental evidence for the abiotic formation of the methylenedioxy unit is provided, as photolysis of the quinone (+)-komaroviquinone resulted in the formation of the [1,3]dioxole-containing natural product (-)-cyclocoulterone and (+)-komarovispirone.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Collective Syntheses of Icetexane Natural Products Based on Biogenetic Hypotheses

Thommen

Neuburger

Gademann

2016

Chemistry A European J

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“…[19] To obtain some insight into the reaction mechanism, radical-trapping experiments were conducted by employing 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) and 1,4-benzoquinone (BQ). To further exemplify the synthetic importance of azido group in the product, the PPh 3 -promoted intramolecular Staudinger/aza-Wittig reaction of 16D,f ollowed by selective reduction with sodium cyanoborohydride (NaBH 3 CN) generated the bridged amine 21 in 40 %y ield (Scheme 3d).…”

Section: Angewandte Chemiementioning

confidence: 99%

Radical‐Mediated 1,2‐Formyl/Carbonyl Functionalization of Alkenes and Application to the Construction of Medium‐Sized Rings

Wang

et al. 2016

Angewandte Chemie

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An ovel radical 1,2-formylfunctionalization of alkenes involving 1,2(4,5)-formyl migration triggered by addition of various carbon-and heteroatom-centered radicals to alkenes has been developed for the first time,thus providing straightforwarda ccess to diverse b-functionalized aldehydes with good efficiency,r emarkable selectivity,a nd excellent functional group tolerance.A nalogous transformations mediated by ak eto-carbonyl migration have also been effected under similar conditions.This method was used to access ring systems including various benzannulated nine-, ten-, and eleven-membered rings,c omplex 6-5(6,7)-6(5) fused rings, and bridged rings with diverse functionalities.

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“…1 for numbering). 1 Of these groups, the icetexones are the most complex, exhibiting oxygenation at the C11, C12, and C14 positions, as well as possessing a lactone or ether linkage between C19 and either the C10 or C6 position. Members of the highly oxygenated icetexone subclass have been isolated from different plants of the Salvia genus.…”

Section: Introductionmentioning

confidence: 99%

Synthetic studies on the icetexones: enantioselective formal syntheses of icetexone and epi-icetexone

et al. 2013

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Two strategies for the synthesis of the icetexane diterpenoids icetexone and epi-icetexone that rely on Ga(III)-catalyzed cycloisomerization of alkynyl indene substrates to yield fused [6-7-6] tricycles have been explored. In the first approach, access to a tricycle bearing a gem-dimethyl group paved the way for explorations of C–H functionalization of one of the methyl groups in close proximity to a hydroxyl-directing group. This approach was ultimately unsuccessful and led only to ring cleaved products. In the second approach, an alkynyl indene substrate bearing a cyano substituent was utilized, which was effective in providing a functional handle to access the icetexone subclass of diterpenoids. A key epoxide opening/diazene rearrangement sequence was utilized to complete a formal synthesis of icetexone and epi-icetexone, which is discussed in detail. Furthermore, the cyano-containing substrate has been prepared in enantioenriched form using a Rh-catalyzed conjugate addition reaction, which now provides a route to the enantioselective synthesis of these natural products.

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Structure, biosynthetic relationships and chemical synthesis of the icetexane diterpenoids

Cited by 79 publications

References 81 publications

Collective Syntheses of Icetexane Natural Products Based on Biogenetic Hypotheses

Collective Syntheses of Icetexane Natural Products Based on Biogenetic Hypotheses

Radical‐Mediated 1,2‐Formyl/Carbonyl Functionalization of Alkenes and Application to the Construction of Medium‐Sized Rings

Synthetic studies on the icetexones: enantioselective formal syntheses of icetexone and epi-icetexone

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