Recent efforts to construct the B-ring of bryostatins

L, Gao; Lu, Ji; Song, Zhenlei

doi:10.1039/c3cc45947k

Cited by 10 publications

(1 citation statement)

References 116 publications

(19 reference statements)

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“…Owing to the increased reactivity of allylsilanes and the facile control of product formation, the Hosomi–Sakurai reaction has also been employed in total synthesis (Scheme ). The synthesis of bryostatin 1 ( 137 ), published by Wender in its entirety in 2017, − showcases the macrocyclization of an allylsilane onto an enal ( 135 ) (Scheme a). Herein, the aldehyde is activated by pyridinium p -toluenesulfonate in combination with trimethyl orthoformate and the in situ TES-deprotected alcohol, forming an oxocarbenium ion which is readily attacked by the nucleophilic alkene, now in close proximity.…”

Section: Addition To Carbonylsmentioning

confidence: 99%

Unconventional Macrocyclizations in Natural Product Synthesis

2020

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Over the past several decades, macrocyclic compounds have emerged as increasingly significant therapeutic candidates in drug discovery. Their pharmacological activity hinges on their rotationally restricted three-dimensional orientation, resulting in a unique conformational preorganization and a high enthalpic gain as a consequence of high-affinity macrocycle–protein binding interactions. Synthetic access to macrocyclic drug candidates is therefore crucial. From a synthetic point of view, the efficiency of macrocyclization events commonly suffers from entropic penalties as well as undesired intermolecular couplings (oligomerization). Although over the past several decades ring-closing metathesis, macrolactonization, or macrolactamization have become strategies of choice, the toolbox of organic synthesis provides a great number of versatile transformations beyond the aforementioned. This Outlook focuses on a selection of examples employing what we term unconventional macrocyclizations toward the synthesis of natural products or analogues.

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Section: Addition To Carbonylsmentioning

confidence: 99%

Unconventional Macrocyclizations in Natural Product Synthesis

2020

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Olefin‐Bildung durch eliminierende Dimerisierung und eliminierende Kreuzkupplung von Carbenoiden: eine stereochemische Herausforderung

Blakemore

Hoffmann

2017

Angewandte Chemie

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Bei der Dimerisierung von Carbenoiden entstehen Olefine, und zwar über die Bildung eines At‐Komplexes, eine nachfolgende 1,2‐Metallat‐Umlagerung und eine abschließende β‐Eliminierung. Da jeder dieser Schritte stereospezifisch ist, kann man das stereochemische Endergebnis nachvollziehen und – im Prinzip – auch steuern, vorausgesetzt, die absolute Konfiguration der reagierenden Carbenoide ist festgelegt. Eine eliminierende Kreuzkupplung zweier unterschiedlicher Carbenoide ermöglicht eine Aufbaureaktion, bei der im Unterschied zu bekannten Olefin‐Synthesen die Geometrie der Doppelbindung unabhängig von der Art der Reste an der Doppelbindung festgelegt werden kann. Die Bildung von Olefinen durch eliminierende Dimerisierung/Kreuzkupplung von Carbenoiden wird an einer Reihe von typischen Beispielen illustriert, etwa an Reaktionen von α‐lithiierten Halogenalkanen, Epoxiden und Carbamaten. Dabei gilt das Augenmerk auch der Erzeugung von sp3‐hybridisierten Carbenoiden mit definierter Konfiguration und deren stereochemischer Zuordnung.

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Formation of Olefins by Eliminative Dimerization and Eliminative Cross‐Coupling of Carbenoids: A Stereochemical Exercise

Blakemore

Hoffmann

2017

Angew Chem Int Ed

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Two carbenoids combine to generate an olefin by a mechanism involving formation of an ate complex, 1,2-metalate rearrangement, and β-elimination. As each stage of this eliminative coupling is stereospecific, the overall stereochemical outcome can be understood and, in principle fully controlled, providing that the absolute stereochemical configurations of the reacting carbenoid species are defined. In contrast to traditional alkene syntheses, the eliminative cross-coupling of carbenoids offers a connective approach to olefins capable of precisely targeting a given isomer regardless of the nature of the features distinguishing the isomers. The formation of olefins by the eliminative dimerization and eliminative cross-coupling of carbenoids is reviewed with a range of illustrative examples, including the reactions of α-lithiated haloalkanes, epoxides, and carbamates. An emphasis is placed on stereochemical analysis and methods to generate sp -hybridized carbenoids in stereodefined form are surveyed.

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Recent efforts to construct the B-ring of bryostatins

Cited by 10 publications

References 116 publications

Unconventional Macrocyclizations in Natural Product Synthesis

Unconventional Macrocyclizations in Natural Product Synthesis

Olefin‐Bildung durch eliminierende Dimerisierung und eliminierende Kreuzkupplung von Carbenoiden: eine stereochemische Herausforderung

Formation of Olefins by Eliminative Dimerization and Eliminative Cross‐Coupling of Carbenoids: A Stereochemical Exercise

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