Developing Molecular Diversity in the Construction of a Family of Bicyclic Isoxazolines Scaffolds: Control of Regio‐and Diastereoselectivities

Abstract

A completely regioselective approach to bicyclic isoxazolines has been found starting from 4‐cyclopentene‐1,3‐dione or 2‐cyclopentenones. 1,3‐Dipolar cycloaddition with nitrile oxides gave different semirigid bicyclic scaffolds with at least four points of elaboration for molecular diversity. From these intermediates, two families of regioisomer isoxazolines can be prepared with complete control of their relative stereochemistry. Further elaboration of functional groups was demonstrated in order to exploit a successive parallel preparation of arrays of compounds. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Studies of Stereo-Selective Cyclo-Additions and Transformations of Substituted 2-Cyclopenten-1-one with Chiral Anthracene Templates.

“…2). These were supported the previous study 19 that cyclopentene-3,5-dione itself in refluxing benzene was present exclusively as the keto tautomer. The X-ray crystallography also showed the orientation of the methoxy group away from the approaching dienophile.…”

Synthesis of Bicyclic Isoxazoles and Isoxazolines via Intramolecular Nitrile Oxide Cycloaddition

“…The most common methods for generating nitrile oxides are the dehydrohalogenation of hydroximoyl chlorides [20,21,22,23,24], the oxidation of aldoximes [25,26,27,28,29,30,31,32], and the dehydration of nitroalkanes [33,34,35,36]. Although a wide variety of procedures are available for the synthesis of diverse isoxazole and isoxazoline derivatives, few of them address the preparation of carbocyclic fused isoxazole/isoxazoline derivatives [37,38,39,40,41,42]. The dehydration of the nitroalkanes followed by intramolecular dipolar cycloaddition is the most popular method for the construction of carbocycle fused isoxazole/isoxazoline derivatives.…”

Sensible Improvements Induced by Ionic Liquids in the Reaction of Modified Carbasugars with Bases for the Building of Constrained Carbanucleosides

“…Following our interest in the synthesis of functionalized cyclopentanols, , we embarked on the synthesis of a new family of conformationally locked nucleoside analogues in view of their potential biological relevance, using as starting material the easily available 4-hydroxy-4-methyl-2-cyclopentenone, 4 . The proposed strategy was to elaborate 4 toward a common intermediate suitably functionalized for the introduction of different nucleobases.…”