The Tandem Radical Cyclization Approach to Angular Triquinanes

Curran, Dennis P.; Kuo, Shen-Chun

doi:10.1016/s0040-4020(01)87744-9

Cited by 48 publications

(7 citation statements)

References 34 publications

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“…3b)32 that builds on a long-standing biosynthetic hypothesis allows access to complex polyether molecules (found in many marine natural products). Similar cascades have been reported that involve other reactive intermediates, including anions, carbenes3 and radicals33. Even cross-over processes, in which one reactive intermediate produces a second, different kind of intermediate34, are emerging as innovative features of step-economical syntheses.…”

Section: Towards the Ideal Synthesissupporting

confidence: 56%

Synthesis at the molecular frontier

Wender¹,

Miller²

2009

Nature

515

289

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Driven by remarkable advances in the understanding of structure and reaction mechanisms, organic synthesis will be increasingly directed to producing bioinspired and newly designed molecules. Molecular evolution on Earth over the past 3.8 billion years has produced an extraordinary library of chemical structures, unsurpassed in number, diversity and function. Each structure is a treasure-trove of information and inspiration, a molecular textbook encoded in the language of chemistry. Collectively, these molecules comprise the chemical genome of our planet, and represent a universe ripe for exploration. With modern analytical tools, each of these structural tomes can now be read, enabling an understanding of how structure relates to function. More significantly, we can now use organic synthesis not only to make copies of these molecules, but also to prepare bioinspired or designed compounds, some with functions unheard of in the natural world -compounds that will influence, if not shape, every facet of our existence.Our emerging molecular literacy is creating a revolution that will transform our world. The ability to design, create and control molecules has opened a vast frontier of research and an age of unprecedented opportunity. Scientists from every background are being drawn to this molecular frontier, creating a melting pot of disciplinary fusions and the resultant ability to address problems that transcend the boundaries of individual fields. From molecular biology to molecular computing, molecular medicine, molecular (nano) technology and even molecular gastronomy, science is becoming increasingly integrated and 'molecularized'.Chemists have been laying the foundations for this molecular revolution for the past two centuries. Before that, nature's archive was the sole or primary source of chemicals used by humans. This has now changed. Through extraordinarily innovative advances in tools, theories and methods, synthesis has provided a reliable supply of many natural compounds as well as others created by design. Indeed the question of whether a molecule from nature could be made is increasingly giving way to whether it could be made in a way that impacts on supply and science. Of increasing importance now is the question of what molecules to make. Naturally occurring molecules are produced in their ecosystems for uses other than what we seek or need. Their activities in humans are thus serendipitous and unoptimized but provide a rich source of information and inspiration. We are now on the cusp of a period in which we can use this inspiration to design molecules with superior or new functions and make them in increasingly efficient, practical and environmentally friendly ways [1][2][3][4][5][6][7][8][9][10][11] .

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Section: Towards the Ideal Synthesissupporting

confidence: 56%

Synthesis at the molecular frontier

Wender¹,

Miller²

2009

Nature

515

289

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“…The one‐ring template strategy was used by Curran and co‐workers in admirable CC syntheses of (±)‐silphiperfol‐6‐ene, (±)‐9‐episilphiperfol‐6‐ene,48 (±)‐modhephene, (±)‐epimodhephene,49 and the BCD ring section of crinipellin A ( 39 a ) 50. These preparations all required the cyclization of an allylic radical, which worked well, but gave the “wrong” isomer 39 b in a 5:1 ratio with 39 a (Scheme ).…”

Section: Two‐stage Unimolecular Free‐radical Cascadesmentioning

confidence: 99%

Programming Organic Molecules: Design and Management of Organic Syntheses through Free-Radical Cascade Processes

McCarroll

Walton

2001

Angew. Chem. Int. Ed.

233

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Cascade, domino, or tandem processes, that link together two or more transformations in one pot, are increasing in popularity because they lead to improvements in synthetic efficiency and decreases in environmental impact. Not only do these cascades contain choice mechanistic gems but they also deliver compact and elegant syntheses of complex natural products. Longer cascades require more functional groups precisely configured within carefully designed initial molecular architectures. Such “purposeful” molecules can be thought of as chemical algorithms.This article surveys the phenomenal range of unimolecular free‐radical cascades. A convenient system for classifying free‐radical cascades is described that is useful for evaluating and comparing cascades and aids the design of synthetic routes to polycyclic structures.Double cyclization cascades lead to cyclopentylcyclopentane or bicyclo[3.3.0]octane derivatives. Precursors that contain a ring as a template have been used to control stereochemistry in syntheses of triquinanes and many related compounds. Of the cascades containing ring‐cleavage steps, the most useful are the ring expansions which have opened up new synthetic routes to medium ring polycycles.The key design features of three‐stage unimolecular free‐radical cascades that yielded steroid structures, are linear arrays of radical acceptor units associated with methyl groups distributed every fifth C‐atom in the precursor polyenes. Ring cleavage is the reverse of cyclization. In special, symmetrical structures, therefore, this led to sequences that were reversible, thus launching endlessly repeating cascades supported by delightfully fluxional structures. The science of “programming” organic molecules to achieve particular target structures is maturing rapidly. Coordination and classification of the welter of information in this area is intended to facilitate design and hence to extend the range and complexity of attainable structures.

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“…Die Gruppe von Curran nutzte die Strategie mit einem Ring als Templat für bewundernswerte CC ‐Synthesen von (±)‐Silphiperfol‐6‐en, (±)‐9‐Episilphiperfol‐6‐en,48 (±)‐Modhephen, (±)‐Epimodhephen49 und dem BCD‐Ringteil von Crinipellin A 39 a 50. Bei all diesen Synthesen ist die Cyclisierung eines Allylradikals nötig, die zwar ausgezeichnet verläuft, aber das „falsche“ Isomer 39 b neben 39 a im Verhältnis 5:1 ergibt (Schema ).…”

Section: Unimolekulare Zweistufige Radikalische Kaskadenunclassified

Programmierung organischer Moleküle: Design und Management organischer Synthesen über radikalische Kaskaden

McCarroll

Walton

2001

Angew. Chem.

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1. Einleitung 1.1. Beschreibung, Anwendungsbereich und Nutzen von Kaskadenreaktionen Chemische Prozesse, bei denen zwei oder mehr molekulare Veränderungen räumlich und zeitlich eng verknüpft sind (¹Eintopfreaktionenª), wurden als Kaskaden-, Domino-oder Tandemreaktionen oder auch Reaktionsfolgen bezeichnet. Die Wahrnehmung und das chemische Verständnis solcher Prozesse lassen noch zu wünschen übrig, doch das Tempo der Entwicklung ist in letzter Zeit deutlich schneller geworden, da man ihre tatsächlichen und potentiellen Vorteile mehr und mehr erkennt. Mit ihrer Hilfe kann man die Zahl der für den Aufbau eines komplexen Moleküls nötigen Arbeitsschritte im Labor verringern und damit Arbeits-und Gerätezeit sparen und muss weniger Laborplatz beanspruchen. Damit einher geht ein geringerer Verbrauch von Lösungsmitteln und Chemikalien, und es fallen weniger unerwünschte Begleitprodukte an. All diese Faktoren können die Effizienz einer Synthese beträchtlich verbessern und die Umweltbelastung reduzieren. Dieses Potential im Hinblick auf rationelle Synthesen im Labor und im industriellen Maûstab garantiert den Kaskadenprozessen eine glänzende Zukunft.Je gröûer die Zahl der Kaskadenstufen ist, um so mehr Funktionalitäten müssen sich im sorgfältig entworfenen Startmolekül genau an der richtigen Position befinden. Diese Bedingung kann sehr wohl einige der möglichen Vorteile der Kaskadenmethode aufwiegen. Die Struktur der Vorstufe(n) muss sorgfältig ¹programmiertª werden, wenn eine komple-

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The Tandem Radical Cyclization Approach to Angular Triquinanes

Cited by 48 publications

References 34 publications

Synthesis at the molecular frontier

Synthesis at the molecular frontier

Programming Organic Molecules: Design and Management of Organic Syntheses through Free-Radical Cascade Processes

Programmierung organischer Moleküle: Design und Management organischer Synthesen über radikalische Kaskaden

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