Stereoselective Solid-Phase Synthesis of -Lactams—A Novel Cyclization/Cleavage Step towards 1-Oxacephams

Furman, Bartłomiej; Thürmer, René; Kałuża, Zbigniew; Łysek, Robert; Voelter, Wolfgang; Chmielewski, Marek

doi:10.1002/(sici)1521-3773(19990419)38:8<1121::aid-anie1121>3.0.co;2-d

Cited by 40 publications

(14 citation statements)

References 6 publications

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“…Examples include benzazepinones, [262] benzodiazepinones, [258,263] diazepindiones, [264±266] hydantoins, [258, 263, 267±274] thiohydantoins, [268] thiazolylhydantoins, [275] benzopyrones, [276] benzoisothiazolones, [258] benzisoxazoles, [277,278] diketopiperazines, [265, 279±281] diketomorpholines, [280] quinazolindiones, [282,283] hydroxyquinolinones, [284] pyrazolones, [285±287] dihydropyridines, [288] dihydropyrimidindiones, [289] pyridine-fused heterocycles, [290] oxazines, [291,292] oxazolines, [291,292] oxazolidinones, [293±296] phthalides, [297] lactones, [298±300] lactams, [301] cyclic sulfonamides, [302] cyclic ethers, [303±306] cyclic imides, [307] tetrahydro-b-carbolines, [308,309] 2-quinolone, [310] coumarin, [310] indolyl diketopiperazine alkaloids, [311,312] and cyclic peptides. Examples include benzazepinones, [262] benzodiazepinones, [258,263] diazepindiones, [264±266] hydantoins, [258, 263, 267±274] thiohydantoins, [268] thiazolylhydantoins, …”

Section: Cyclative Cleavagementioning

confidence: 99%

Modern Separation Techniques for the Efficient Workup in Organic Synthesis

Tzschucke

Märkert

Bannwarth

et al. 2002

Angew. Chem. Int. Ed.

339

133

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The shift of paradigm in combinatorial chemistry, from large compound libraries (of mixtures) on a small scale towards defined compound libraries where each compound is prepared in an individual well, has stimulated the search for alternative separation approaches. The key to a rapid and efficient synthesis is not only the parallel arrangement of reactions, but simple work-up procedures so as to circumvent time-consuming and laborious purification steps. During the initial development stages of combinatorial synthesis it was believed that rational synthesis of individual compounds could only be achieved by solid-phase strategies. However, there are a number of problems in solid-phase chemistry: most notably there is the need for a suitable linker unit, the limitation of the reaction conditions to certain solvents and reagents, and the heterogeneous reaction conditions. Further disadvantages are: the moderate loading capacities of the polymeric support and the limited stability of the solid support. In the last few years several new separation techniques have been developed. Depending on the chemical problem or the class of compounds to be prepared, one can choose from a whole array of different approaches. Most of these modern separation approaches rely on solution-phase chemistry, even though some of them use solid-phase resins as tools (for example, as scavengers). Several of these separation techniques are based on liquid-liquid phase separation, including ionic liquids, fluorous phases, and supercritical solvents. Besides being benign with respect to their environmental aspects, they also show a number of advantages with respect to the work-up procedures of organic reactions as well as simplicity in the isolation of products. Another set of separation strategies involves polymeric supports (for example, as scavengers or for cyclative cleavage), either as solid phases or as soluble polymeric supports. In contrast to solid-phase resins, soluble polymeric supports allow reactions to be performed under homogeneous conditions, which can be an important factor in catalysis. At the same time, a whole set of techniques has been developed for the separation of these soluble polymeric supports from small target molecules. Finally, miscellaneous separation techniques, such as phase-switchable tags for precipitation by chemical modification or magnetic beads, can accelerate the separation of compounds in a parallel format.

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Section: Cyclative Cleavagementioning

confidence: 99%

Modern Separation Techniques for the Efficient Workup in Organic Synthesis

Tzschucke

Märkert

Bannwarth

et al. 2002

Angew. Chem. Int. Ed.

339

133

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“…Die Benzyletherbindung wird im Allgemeinen mit TFA gespalten,79a–79d die Spaltung gelingt aber auch mit 2,3‐Dichlor‐5,6‐dicyan‐1,4‐benzochinon (DDQ) 79e. Eine interessante Anwendung für derartige Linker beschreiben Chmielewski et al mit der Synthese von 1‐Oxacephamen (Schema ) 79f,79g. Durch Lewis‐Säure‐induzierte Abspaltung des Vinyloxysubstituenten entsteht ein Carbokation, das vom Benzylsauerstoffatom unter Cyclisierung und Abspaltung abgefangen wird.…”

Section: Bildung Von Alkoholen Und Thiolenunclassified

Utilization of BRCA1/2 genetic testing in the clinical setting

Lee

Bernhardt

Helzlsouer

2002

Cancer

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Heutzutage findet sich nur selten eine Ausgabe einer wichtigen Chemiezeitschrift, die nicht mindestens einen Artikel über die Festphasensynthese enthält. Das überrascht kaum, denn dieses Verfahren verspricht das Ende mühsamer Aufarbeitungen und die leichtere Herstellung riesiger Substanzbibliotheken mit kombinatorischen Methoden. Die Festphasentechnik ist inzwischen nicht mehr nur für die Peptidsynthese interessant: Mittlerweile gelang die Herstellung und Isolierung von zahlreichen Substanzklassen durch Festphasensynthese. Dieser Aufsatz beschäftigt sich mit dem „Linker“, der Ankergruppe zwischen polymerem Träger und Zielmolekül. Am Ende einer Synthese besteht die Aufgabe des Linkers darin, ein Produkt vom Träger in die Lösung freizusetzen: Dies geschieht ausnahmslos durch eine chemische Veränderung des Produkts an der vorherigen Verknüpfungsstelle. Einige Linker sind offenbar „spurlos“. Aber was genau ist „Spurlosigkeit“? Vor zwanzig Jahren, als die Spaltung eines Linkers eine polare Carbonsäure als Überrest (Spur) am Träger hinterließ, war diese Vorstellung sehr attraktiv. Heute stehen dem Chemiker zahllose neue Linker zur Verfügung, die Produkte mit den meisten Hauptfunktionalitäten an der früheren Verknüpfungsstelle abspalten können, und wir wollen zeigen, dass der Begriff „spurlos“ zwar derzeit weit verbreitet, aber ohne Bedeutung ist. Stattdessen schlagen wir eine Neuordnung der Linker vor, die sich nach den bei der Spaltung frei werdenden funktionellen Gruppen richtet, und empfehlen eine Nomenklatur, um diese Einteilung zu untermauern. Wir hoffen, mit diesem Aufsatz auch Gebiete der Linkertechnik hervorzuheben, die weiterer Forschung bedürfen.

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“…The benzylic ether bond is typically cleaved with TFA,79a–79d but 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ) has the same effect 79e. An interesting application of such a linker, the synthesis of 1‐oxacephams, has been reported by Chmielewski and co‐workers (Scheme ) 79f,79g. The Lewis acid induced loss of the vinyloxy substituent followed by trapping of the resulting carbocation by the benzylic oxygen atom results in cleavage and cyclization.…”

Section: Formation Of Alcohols and Thiolsmentioning

confidence: 99%

“… PACT H−OR linker. 1‐Oxacepham synthesis by nucleophilic displacement at the C4 position of the azetidine‐2‐one ring 79f,79g…”

Section: Formation Of Alcohols and Thiolsmentioning

confidence: 99%

Effect of bond‐length alternation on the dipole hyperpolarizability of phenol blue

Neto

Canuto

2002

Int J of Quantum Chemistry

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Phenol blue is a merocyanine dye that may exist in resonance between two extreme forms, a neutral keto form and a zwitterionic, charge-separated eno form. The keto form is stable in the gas phase, while the eno form can be stabilized by solvents. In this work, the bond-length alternation is used to monitor the change of the dipole hyperpolarizability of phenol blue continuously from the extreme eno to the other extreme keto forms. Intermediate structures were found to give the largest value for the first dipole hyperpolarizability. These values are compatible with the experimental results in different solvents and suggest that phenol blue undergoes structural changes in polar solvents.

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Stereoselective Solid-Phase Synthesis of -Lactams—A Novel Cyclization/Cleavage Step towards 1-Oxacephams

Cited by 40 publications

References 6 publications

Modern Separation Techniques for the Efficient Workup in Organic Synthesis

Modern Separation Techniques for the Efficient Workup in Organic Synthesis

Utilization of BRCA1/2 genetic testing in the clinical setting

Effect of bond‐length alternation on the dipole hyperpolarizability of phenol blue

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