Enantiomerically pure isoxazolines by stereoselective 1,3-dipolar cycloaddition of silyl nitronates

✍ Scribed by Guido Galley; Peter G. Jones; Michael Pätzel

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 556 KB
• Volume: 7
• Category: Article
• ISSN: 0957-4166
• DOI: 10.1016/0957-4166(96)00250-9

✦ Synopsis

The cycloaddition reactions of in situ generated silyl nitronates 3 to chiral enone la or enoate l b proceed with high stereoselectivity to give enantiomericaUy pure N-silyloxyisoxazolidines 4, which can easily be transformed into A2-isuxazolines 5.

Based on an X-ray analysis the major diastereomers were assigned as the synderivatives, thus differing from diastereofacial selectivity found with nltrile oxides. The base-catalyzed ring-opening reaction of isoxazoline 5a affords the chiral 13-hydroxy nltrile 6, which was cyclized to the sugar-like tetrahydrofuran 7.