Solid-Phase Synthesis of Isoxazoles and Isoxazolines:  En Route to a New Class of Ionophores

Kantorowski, Eric J.; Kurth, Mark J.

doi:10.1021/jo970712g

Cited by 45 publications

(18 citation statements)

References 25 publications

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“…This technique has found extensive application in the organic synthesis [78] and was applied to the 1,3dipolar cycloadditions which are perhaps the most useful method to prepare heterocyclic 5-membered rings. Usually the 1,3-dipoles were generated in situ from the hydroximoyl chlorides and immediately trapped with suitable dipolarophiles [79,80]. Usually the 1,3-dipoles were generated in situ from the hydroximoyl chlorides and immediately trapped with suitable dipolarophiles [79,80].…”

Section: Synthetic Applications In the Solid Phase Chemistrymentioning

confidence: 99%

Synthesis and Synthetic Applications of 1,2,4-Oxadiazole-4-Oxides

Quadrelli¹,

Caramella

2007

COC

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The first 1,2,4-oxadiazole-4-oxide was prepared by Wieland a century ago, but this compound remained largely a chemical curiosity until very recently. 1,2,4-Oxadiazole-4-oxides are a family of heterocycles closely related to the chemistry of nitrile oxides which were actively studied in the past half century and provided the basic knowledge on 1,2,4-oxadiazole-4-oxides. The dimerizations of nitrile oxides under acidic or basic conditions were thoroughly studied by different research groups, and offer the more common entries to the symmetrical substituted 1,2,4-oxadiazole-4-oxides. A more general route to symmetrical and unsymmetrical substituted 1,2,4-oxadiazole-4-oxides is based on the nitrile oxide cycloadditions to amidoximes. A variety of other 1,2,4-oxadiazole-4-oxides forming reactions are also known in the literature. Many of these reactions were neither fully exploited nor mechanistically understood since they require unusual starting reagents, often difficult to prepare, or take place affording complex mixtures of products. Some of these methods still await for improved procedures and proper mechanistic attention to be of general use and will be reviewed shortly.The chemistry of 1,2,4-oxadiazole-4-oxides is related to the fragility of the heterocyclic ring, which undergoes thermal or photochemical cycloreversion to nitriles and nitrosocarbonyl intermediates. Trapping of the nitrosocarbonyls takes place easily with dienes and enes, affording a variety of hetero Diels-Alder and ene adducts, which attract great interest because of their useful synthetic elaboration toward many natural products of potential pharmaceutical applications.The high efficiency of the photochemical cleavage of 1,2,4-oxadiazole-4-oxides at room temperature or well below affords the softest entry to the nitrosocarbonyls and allows for the study of their chemistry under convenient and simple experimental conditions. The photochemical cleavage have been applied successfully to Solid Phase chemistry, allowing for a safe and environmental friendly methodology for the synthesis of important intermediates.This report is comprehensive of the synthesis and synthetic applications of the 1,2,4-oxadiazole-4-oxides. R R' O 1 2 3 960 Quadrelli and Caramella 12 + 11 10 9 + 4 5 6 8 7 -HX 16 a N=O 13 b NH 2 _ X 9 N=O 7 NH 2

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Section: Synthetic Applications In the Solid Phase Chemistrymentioning

confidence: 99%

Synthesis and Synthetic Applications of 1,2,4-Oxadiazole-4-Oxides

Quadrelli¹,

Caramella

2007

COC

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“…3 Consequently, isoxazoles are prized as potential drug candidates and biological probes. There have been several reports relating to the synthesis of functionalized isoxazoles by combinatorial techniques, 4 although the use of 4-iodoisoxazoles as the key intermediate for library generation is thus far unreported. Many of the reported libraries have been limited to the preparation of disubstituted isoxazoles.…”

Section: Introductionmentioning

confidence: 99%

Solution Phase Synthesis of a Diverse Library of Highly Substituted Isoxazoles

et al. 2008

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The iodocyclization of O-methyloximes of 2-alkyn-1-ones affords 4-iodoisoxazoles, which undergo various palladium-catalyzed reactions to yield 3,4,5-trisubstituted isoxazoles. The palladium-catalyzed processes have been adapted to parallel synthesis utilizing commercially available boronic acid, acetylene, styrene, and amine sublibraries. Accordingly, a diverse 51-member library of 3,4,5-trisubstituted isoxazoles has been generated.

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“…However, the solid‐phase synthesis of isoxazoles has been rarely used to access peptides containing an isoxazole ring in the backbone. Although the solid‐phase synthesis of 3,5‐disubstituted isoxazoles over a duration of a few minutes to several hours without the need for a metal catalyst has already been described, this approach was not applied directly within a peptide chain. Several groups have reported the synthesis of isoxazole‐containing amino acids subsequently inserted within the peptide chain using conventional solid phase peptide syntheses (SPPS) , , .…”

Section: Introductionmentioning

confidence: 99%

Regioselective Solid‐Phase Synthesis of Peptide Analogues Containing 3,4‐ or 3,5‐Disubstituted Isoxazole as s‐cis or s‐trans Peptide Bond Mimics

2019

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A method for regioselective solid‐phase synthesis of disubstituted peptidoisoxazoles is reported. Improved conditions for the synthesis of 3,5‐disubstituted isoxazoles (mimicking s‐trans peptide bond) without metal catalysts were implemented. New conditions enabling the synthesis of 3,4‐disubstituted isoxazoles (mimicking s‐cis peptide bond) using ruthenium catalysts were developed. This study provides a means for the regioselective preparation of new libraries of peptidomimetic molecules containing an isoxazole moiety within the backbone.

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Solid-Phase Synthesis of Isoxazoles and Isoxazolines: En Route to a New Class of Ionophores

Cited by 45 publications

References 25 publications

Synthesis and Synthetic Applications of 1,2,4-Oxadiazole-4-Oxides

Synthesis and Synthetic Applications of 1,2,4-Oxadiazole-4-Oxides

Solution Phase Synthesis of a Diverse Library of Highly Substituted Isoxazoles

Regioselective Solid‐Phase Synthesis of Peptide Analogues Containing 3,4‐ or 3,5‐Disubstituted Isoxazole as s‐cis or s‐trans Peptide Bond Mimics

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