Solid phase synthesis of diverse isoxazolidines via 1,3-dipolar cycloaddition
摘要:
Diverse substituted isoxazolidines 2-4 are assembled on solid phase by condensing hydroxylamines with aldehydes and trapping the resulting nitrones with various dipolarophiles. The one-pot three-component cycloaddition reaction yields the isoxazolidines in good to excellent yield. Three different reaction pathways - each dealing with one of the three components attached to the solid support - are evaluated with respect to versatility and yield of the synthesized isoxazolidines. Structures and relative configurations of representative isoxazolidines are elucidated with H-1-NMR, TOCSY, HSQC and NOESY. The reaction of polymer-bound hydroxylamines with aldehydes and alkenes is found to be the most successful. The kinetics of the solid phase reaction are determined by FT-IR-ATR spectroscopy. polymer-bound nitrones are stable for the split/combine synthesis. A library of isoxazolidines is synthesized by the split/combine method and analyzed by means of HPLC-MS. (C) 1998 Elsevier Science Ltd. All rights reserved.