Perfluoro-Tagged Benzyloxycarbonyl Protecting Group and Its Application in Fluorous Biphasic Systems

Schwinn, Dominik; Bannwarth, Willi

doi:10.1002/1522-2675(200201)85:1<255::aid-hlca255>3.0.co;2-5

Cited by 45 publications

(14 citation statements)

References 18 publications

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“…After extraction, only the labeled product is found in the fluorous phase, whereas all the other organic compounds remain in the organic phase. [138] Fluorous labeling was employed by Theil and co-workers in the kinetic resolution of 1-phenylethanol. The organic compounds are eluted with a polar organic solvent (methanol/ water, acetonitrile/water), while more fluorophilic solvents (diethyl ether, perfluoroalkanes) elute the perfluoro-tagged product.…”

Section: Perfluoro-tagged Productsmentioning

confidence: 99%

Modern Separation Techniques for the Efficient Workup in Organic Synthesis

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Märkert

Bannwarth

et al. 2002

Angew. Chem. Int. Ed.

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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: Perfluoro-tagged Productsmentioning

confidence: 99%

Modern Separation Techniques for the Efficient Workup in Organic Synthesis

Tzschucke

Märkert

Bannwarth

et al. 2002

Angew. Chem. Int. Ed.

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339

133

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“…Reaction between 2-hydroxythioxanthene-9H-one (24) [41] and 21b in the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDCI) and N,N-dimethylpyridin-4-amine (DMAP) [42 ± 44] in 64% yield. The MEM protecting group was removed with 3m aqueous HCl in THF under reflux [45] [46] to yield the alcohol 25b. Reaction with diphosgene, and reaction of the resulting chloroformate with thymidine, analogous to the method described above, proceeded in 58% yield.…”

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Synthesis of Caged Nucleosides with Photoremovable Protecting Groups Linked to Intramolecular Antennae

Smirnova

Wöll

Pfleiderer

et al. 2005

Helvetica Chimica Acta

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Based on the [2-(2-nitrophenyl)propoxy]carbonyl (nppoc) group, six new photolabile protecting groups (2, 8, 9b, 16b, 25b, and 26), each covalently linked to a 9H-thioxanthen-9-one (Tx) unit functioning as an intramolecular triplet sensitizer, were synthesized. Linkers were introduced between the Me group or the aromatic ring of nppoc and the 2-position of Tx by means of classical organic synthesis combined with Pd catalyzed CÀC coupling reactions. The new photolabile protecting groups to be used in light-directed synthesis of DNA chips were attached to the 5'-O-atom of thymidine via a carbonate linkage, giving rise to the caged nucleosides 7, 11, 13, 19, 20, and 30. Introduction. ± Light-directed, massive parallel combinatorial synthesis with photoremovable protecting groups allows the fabrication of high-density DNA chips [1] [2], i.e., arrays of up to 1 million spots of different oligonucleotides on an area of ca. 1 cm 2 . Such high-density DNA chips represent highly effective diagnostic tools for a variety of genomic applications such as genotyping [3], gene-expression profiling [4], and sequencing by hybridization [5]. Several reviews on DNA chips and their application have been published [6 ± 12].The efficiency of the photolithographic technique for producing high-density DNA chips critically depends on the performance, i.e., the light sensitivity and the uniformity of the photochemical cleavage reaction of the photolabile protecting groups blocking either the terminal 5'-OH or the 3'-OH group in the growing oligonucleotides. Among the photolabile protecting groups currently in use for photolithographic DNA-chip synthesis [13], the [2-(2-nitrophenyl)propoxy]carbonyl (nppoc) group (1) developed by Pfleiderer and co-workers is a prominent example [14] [15]. It reacts in excellent yield and gives rise to a good quantum yield, the only draw-back for a higher light sensitivity being its low absorption coefficient in the near UV, where illumination is usually performed with the 366-nm Hg line. It has been shown that this problem can be overcome by triplet sensitization, e.g., with 9H-thioxanthen-9-one ( thioxanthone ), which has a high absorption coefficient at 366 nm and, on diffusional encounters, transfers its triplet energy to the photoreactive nitrobenzyl chromophore [16]. In O 2 -free solution, the rate of photodeprotection of nppoc-protected thymidine is enhanced by a factor of ca. ten, when thioxanthone is added as a sensitizer. However, since intermolecular energy transfer is rate-limited by diffusion, in the presence of O 2 , the sensitizer is mostly quenched, and the enhancement of the photoreactivity is only weak or even absent. To avoid the diffusional step in energy transfer, we synthesized new

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“…Die jeweiligen Zwischenprodukte werden durch Flüssig‐flüssig‐Extraktion mit FC‐72 isoliert, abschließend spaltet man das Chinazolindion 26 durch intramolekulare Cyclisierung von der Fluormarkierung ab. Da nur das gewünschte Produkt cyclisiert, behalten alle nichtumgesetzten Moleküle ihre Markierungsgruppe und können daher durch Extraktion vom Produkt abgetrennt werden 138. Theil et al beschrieben die Verwendung von fluorierten Schutzgruppen zur kinetischen Racematspaltung von 1‐Phenylethanol.…”

Section: Flüssig‐flüssig‐phasentrennungunclassified

Moderne Trennverfahren zur effizienten Aufarbeitung in der organischen Synthese

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Die kombinatorische Synthese [1,2] wird als eine der Schl¸s-seldisziplinen f¸r den konstanten Nachschub an chemischen Verbindungen angesehen, die auf biologische Aktivit‰t gegen¸ber der immens wachsenden Zahl biologischer Zielmolek¸le getestet werden kˆnnen. Zusammen mit dem Hochdurchsatz-Screening und einem effizienten Datenmanagement wird ihre Anwendung den Prozess der Wirkstoffentdeckung zweifelsohne beschleunigen. Urspr¸nglich konzentrierte sich die Kombinatorische Chemie auf die schnelle Synthese von hochkomplexen Gemischen mit winzigen An-

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Perfluoro-Tagged Benzyloxycarbonyl Protecting Group and Its Application in Fluorous Biphasic Systems

Cited by 45 publications

References 18 publications

Modern Separation Techniques for the Efficient Workup in Organic Synthesis

Modern Separation Techniques for the Efficient Workup in Organic Synthesis

Synthesis of Caged Nucleosides with Photoremovable Protecting Groups Linked to Intramolecular Antennae

Moderne Trennverfahren zur effizienten Aufarbeitung in der organischen Synthese

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