Synthesis of an enantiomerically pure indolosesquiterpene

Sarragiotto, María Helena; Gower, Adriana E.; Marsaioli, Anita Jocelyne

doi:10.1039/p19890000559

Cited by 10 publications

(8 citation statements)

References 3 publications

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“…First we examined the preparation of the keto ketal 12 from 10 by means of the hydration of the triple bond and subsequent selective ketalization of the initially formed diketone 11. Thus, mercury-catalyzed hydration of 10 gave the previously known (17) diketone 11 in nearly quantitatively yield, which upon treatment with 1 equiv of ethylene glycol and a catalytic amount of pyridinium />-toluenesulfonate (PPTS) in refluxing C6H6 afforded a mixture of products from which the required keto ketal 12 was isolated in only 7 5 % yield after careful cc (17). The modest yield obtained for this simple transformation and the difficulties we encountered in the separation of the reaction mixture led us to search for a more efficient method for accomplishing this transformation.…”

Section: Resultsmentioning

confidence: 97%

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Studies on the Synthesis of Scoparic Acid A and Related Labdane Diterpenoids. Synthesis of (E)-6β-Hydroxylabda-8-(17),13-dien-15-oic Acid

Abad¹,

Arnó²,

Agulló³

et al. 1993

J. Nat. Prod.

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~STRACT.-A general strategy for a successful approach to labdanes of the type 3-5 is described. This methodology, which makes use of the known Eschenmoser fragmentation of 9, 1,3-oxidative rearrangement of allylic tertiary alcohol 14, and photochemical double bond isomerization ofallylic acetate 17 as key synthetic steps, is used to prepare optically pure labdane 5 from readily available (+)-podocarpenone 8.

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Section: Resultsmentioning

confidence: 97%

“…The final stage to complete the elaboration of the B-ring functionality of the target molecule required isomerization of the 7(8) double bond to the thermodynamically less stable 8 (17) exocyclic position. This isomerization was attempted photochemically.…”

Section: Resultsmentioning

confidence: 99%

Studies on the Synthesis of Scoparic Acid A and Related Labdane Diterpenoids. Synthesis of (E)-6β-Hydroxylabda-8-(17),13-dien-15-oic Acid

Abad¹,

Arnó²,

Agulló³

et al. 1993

J. Nat. Prod.

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“…54 During the manuscript revision two new contributions have appeared in the literature, one describing the synthesis of lecanindole D 15, 61 another reporting the synthesis of drimentines A 27, F 30, G 31 and indotertine A 35. 62 Several syntheses of analogues, of the natural sesquiterpenyl indoles, polyalthenol 37 and polyveoline 5, that is, 12-epi-ent-polyalthenol 60, 55 12-epi-ent-pentacyclindole 61 52 and polyveoline analogue 62, 56 have also been reported, as well as a couple of synthetic approaches towards a non-natural drimanyl indole 63 57 and sespendole 16. 58…”

Section: Syntheses and Synthetic Approximationsmentioning

confidence: 99%

Sesquiterpenyl indoles

et al. 2013

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The natural product sesquiterpenyl indoles are structural hybrids from farnesyl pyrophosphate and tryptophan or its precursors, often with unusual and complex structural features, many of them with interesting biological activities. In this review the compounds of this class known until now are classified, a biosynthetic approach of each group is proposed and a review of the synthesis or synthetic approaches is communicated.

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“…The mixture was stirred at room temperature overnight and the solvent evaporated under vacuum, affording a crude mixture (0.53 g), which after flash column chromatography (hexane-ether, 7:3) gave 450 mg (90%) of 7. 17 …”

Section: Methodsmentioning

confidence: 99%

A New Route toward 7-Oxo-13-hydroxy-8,11,13-podocarpatrienes from Labdane Diterpenes

2006

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Trinorlabdane 1,5-diketones (7, 10a,b, 13a,b), which are easily prepared from labdane diterpenes, are directly converted into the corresponding 7-oxo-13-hydroxy-8,11,13-podocarpatrienes, immediate precursors of bioactive compounds, under basic treatment. Utilizing this strategy, the first enantiospecific synthesis of 13-hydroxy-8,11,13-podocarpatriene (20), a constituent of Taiwania cryptomerioides, was achieved starting from (-)-sclareol (5) after a seven-step sequence in 55% overall yield.Podocarpane diterpenes do not occur extensively in nature but are present in several genera, such as Azadirachta, 1 Humirianther, 2 Micrandropsis, 3 and Podocarpus. 4 During recent years, some biologically active podocarpane phenols have been isolated. Representative examples are 1, a highly fungistatic agent, 5,6 and the aminophenol 3, a potent 5-lipoxygenase inhibitor. 7 Recently, some nor-dehydroabietic acid derivatives, such as 4, have been patented as potential antiviral agents. 8 Due to their natural scarcity, the synthesis of these terpenoids has become the object of increased interest. Some enantiospecific syntheses starting from diterpenes have been reported, but these usually involve many steps and low yields. 9,10 A synthesis based on the enantioselective cyclization of homogeranylbenzene derivatives was recently reported. 11In this paper we report a short and efficient route to 7-oxo-13-hydroxy-8,11,13-podocarpatrienes from labdane diterpenes. The key step involves the intramolecular aldol condensation of a trinorlabdane 1,5-diketone, aromatization of the resulting -enone, and benzylic oxidation. Results and DiscussionDuring our research into the C ring construction of pentacyclic quassinoids starting from communic acids (8a-c), 12 via aldol condensation of the corresponding 1,5-diketones, small quantities of phenol derivatives were obtained together with the required -enones. To explore the synthetic usefulness of this side reaction and its utilization in preparing bioactive podocarpatriene derivatives, several diketones bearing different functionalities in the A-and B-rings were prepared. 1,5-Diketones 7, 10a,b, and 13a,b were synthesized from (-)-sclareol (5), the main component of SalVia sclarea, 13 and communic acids (8a-c), widely found in species of the genus Juniperus, 14 respectively (Scheme 1). 7 was obtained by ozonolysis of enone 6. 15 10a,b resulted from the ozonolysis of dienes 9a and 9b, prepared by 1,4-reduction of the conjugated diene in 8a-c. 13a,b were synthesized after allylic oxidation of 11a,b.Next, the reaction of these diketones to different basic reagents was investigated, and K 2 CO 3 in refluxing MeOH was found to be the most favorable medium to obtain phenol derivatives (Table 1). All diketones gave the expected tricyclic -enones resulting from the intramolecular aldol condensation, utilizing a diluted base solution for a short period of time. 13a,b were transformed in good yields into phenols 19a,b when a concentrated base and a prolonged reaction time were utilized. Aromatization and...

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Synthesis of an enantiomerically pure indolosesquiterpene

Cited by 10 publications

References 3 publications

Studies on the Synthesis of Scoparic Acid A and Related Labdane Diterpenoids. Synthesis of (E)-6β-Hydroxylabda-8-(17),13-dien-15-oic Acid

Studies on the Synthesis of Scoparic Acid A and Related Labdane Diterpenoids. Synthesis of (E)-6β-Hydroxylabda-8-(17),13-dien-15-oic Acid

Sesquiterpenyl indoles

A New Route toward 7-Oxo-13-hydroxy-8,11,13-podocarpatrienes from Labdane Diterpenes

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