Rapid, high-yield synthesis of the marine sesquiterpenes debromoaplysin and aplysin via the acid-catalyzed rearrangement of a cyclobutachromanol

Nath, Asoke; Ghosh, Arun K.; Venkateswaran, Ramanathapuram V.

doi:10.1021/jo00031a026

Cited by 33 publications

(19 citation statements)

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“…A unique example is the total synthesis of isocomene 59 by Pirrung [45] through Cargil rearrangement [46] of the cyclobutane derivative 58 (Scheme 31) obtained from intramolecular photocycloaddition of the dienone 57. The synthesis of 1-debromoaplysin by the group of Venkateswaran [47] is another classic example of the construction of five membered ring through acid catalyzed Wagner-Meerwein rearrangement of cyclobutyl carbinols 95 (Scheme 32). Tandem [2+2] photocycloadditions followed by ring fragmentation provides routes for constructing complex mediumsized ring skeletons.…”

Section: [2+2] Photocycloaddition In the Synthesis Of Structurally Comentioning

confidence: 99%

[2+2] Photochemical Cycloaddition in Organic Synthesis

2019

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The century old [2+2] photocycloaddition reaction appeared as the most synthetically useful reaction amongst all photochemical reactions. It provides not only cyclobutane ring systems, but at the same time it provides access to medium rings through facile ring expansion/fragmentation of the strained cyclobutane ring. The high regio‐and stereoselectivity observed during cycloaddition has made it an attractive tool for synthesis of multicyclic structurally complex natural products. The vast majority of [2+2] photocycloaddition reactions involves enone–alkene cycloaddition which is conveniently achieved through direct excitation or sensitization by UV irradiation. Substantial progress has also been made in [2+2] cycloaddition between two unactivated alkenes using transition metal salts especially copper(I) salts. Sometimes Cu(I)‐catalyzed cycloaddition is advantageous over enone–alkene photocycloaddition. Search for an alternative source to environmentally harmful high energy UV light has led to the discovery of transition metal salts which can be used to excite alkenes by visible light. This causes alkenes to undergo [2+2] cycloaddition and has been used for synthesis of cyclobutane derivatives. This review aims to give an overview about different aspects of [2+2] photocycloaddition reaction with an emphasis in the stereoselective synthesis of selected complex natural products and related molecules where cycloaddition has been used as the key step.

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Section: [2+2] Photocycloaddition In the Synthesis Of Structurally Comentioning

confidence: 99%

[2+2] Photochemical Cycloaddition in Organic Synthesis

2019

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“…[344] Beispiele für die erstgenannte Sequenz finden sich in der Synthese von (À)-Hibaen [345] und in der formalen Totalsynthese von (AE )-Verrucarol. [346] Bei letzterem fand jedoch keine 1,2-Alkylwanderung statt, sondern das intermediär gebildete Kation [347] (AE )-Debromoaplysin und (AE )-Aplysin [348] oder (AE )-Trichodien (272). [349] [350] und (AE )-3-Oxosilphinen gezeigt.…”

Section: Sesquiterpens (Ae )-B-himachalen (263) (Abbildung 8)unclassified

Photochemische Reaktionen als Schlüsselschritte in der Naturstoffsynthese

2011

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Photochemische Reaktionen bereichern in signifikanter Weise das Repertoire zur Knüpfung von Kohlenstoff‐Kohlenstoff‐Bindungen und machen ungewöhnliche, auf herkömmlichem Weg nicht erhältliche Molekülgerüste zugänglich. In diesem Aufsatz werden die wichtigsten Umsetzungen der Photochemie vorgestellt, die auf breiter Front Einzug in die Naturstoffsynthese gehalten haben. Beispielhaft werden einzelne Totalsynthesen diskutiert, wobei besonderes Augenmerk auf den photochemischen Schlüsselschritt sowie dessen Stereoselektivität gerichtet ist. Dabei wird das photochemisch erzeugte Molekül in Relation zur Struktur des Naturstoffs gebracht, und Folgereaktionen werden, wo notwendig, illustriert und klassifiziert.

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“…Hanifin and Cohen reported the photoreactions of chromone with tetramethylethylene, 1-dimethoxyethylene, cyclopentene, and 2-butyne to obtain a variety of cycloadducts [17,18]. Nath et al employed the photocycloaddition reaction of 2, 3, 7-trimethylchromone with ethylene as a key reaction in the synthesis of two marine natural products [19]. Studies from Valiulin and Kutateladze showed that the Diels-Alder adducts of chromones could undergo an intramolecular [2p + 2p] alkene-arene photocyclization reaction [20].…”

Section: Introductionmentioning

confidence: 99%

Modulating the reactivity of chromone and its derivatives through encapsulation in a self-assembled phenylethynylene bis-urea host

Salpage

Donevant

Smith

et al. 2016

Journal of Photochemistry and Photobiology A: Chemistry

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A B S T R A C TThis manuscript reports on the modulation of the photoreactivity of a series of chromones, also known as benzo-g-pyrones, by absorption into a porous self-assembled host formed from phenylethynylene bisurea macrocycles. Chromone and four derivatives namely 6-fluorochromone, 6-bromochromone, 7-hydroxy-4-chromone, and 3-cyanochromone are unreactive in the solid-state. Each of these derivatives was loaded into the nanochannels of self-assembled phenylethynylene bis-urea macrocycles to form solid hostÁguest complexes, which were subsequently UV-irradiated at room temperature under argon atmosphere. We observed that chromone and 6-fluorochromone underwent selective [2 + 2] photodimerization reactions to produce anti-HT dimers in high selectivity and conversion. The 6-bromochromone also reacted in high selectivity and conversion to afford an aryl coupling adduct. In each case, the products were extracted, and the crystalline host recovered. In comparison, 7-hydroxy-4-chromone, and 3-cyanochromone were unreactive within the complex. Simple GCMC simulation studies suggest that chromone, 6-fluorochromone, and 6-bromochromone were loaded in orientations that facilitate photoreaction, and correctly predicted that the anti-HT dimer would be favored in the chromone case. In contrast, syn-HH dimers were predicted by GCMC simulations for the halogen containing derivatives but were not observed. The simulations with 7-hydroxy-4-chromone were in agreement with the observed reactivity. We compare these computational and experimental findings and suggest future methods for optimizing simulation parameters. Our goal is to expand the scope and accuracy of the simulations to be able to predict the reactivity of guests encapsulated within columnar nanotubes.

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Rapid, high-yield synthesis of the marine sesquiterpenes debromoaplysin and aplysin via the acid-catalyzed rearrangement of a cyclobutachromanol

Cited by 33 publications

References 0 publications

[2+2] Photochemical Cycloaddition in Organic Synthesis

[2+2] Photochemical Cycloaddition in Organic Synthesis

Photochemische Reaktionen als Schlüsselschritte in der Naturstoffsynthese

Modulating the reactivity of chromone and its derivatives through encapsulation in a self-assembled phenylethynylene bis-urea host

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