Synthesis of both kinetically and thermodynamically controlled diastereomeric pairs of bis-isoxazolidines from dibenzylideneacetone : Their reactivity and biological activity

Reactions of C-aryl-N-phenyl-nitrones with dibenzylideneacetone yielded pairs of diastereomeric bis-isoxazolidines in good to moderate yields. Both types of cycloadducts possessed identical regio- and stereo-selectivity. Molecular modeling studies revealed small difference in energy between the two isomers. Less stable isomer was converted to more stable one via partial cycloreversion followed by re-cycloaddition pathway. Zinc mediated acid catalyzed cycloreversion was observed for more stable diastereomer whereas less stable one yielded corresponding bis-1,3-aminoalcohols in similar condition. Some cycloadducts were screened for anticancer and antibacterial activity.