Based on the regio and stereoselectivity of 1,3-dipolar cycloaddition reactions of nitrones to alkenes the book has focus on - regio and stereoselectivity synthesis of N-nucleosides by 1,3-dipolar cycloaddition of sugar-derived nitrones with N-arylmaleimides. - 1,3-Dipolar cycloaddition of N-ribosylnitrones and N-arylmalaimides affords anti-isoxazolidine. - A series of novel nitrones were prepared and isolated in a pure state, and they cycloadded to some allyl derivatives to give isoxazolidine derivatives and studied the stereoselectivity of their cycloaddition reactions. - Lewis acid (MgBr2.Et2O) was applied as a catalyst for 1,3-dipolar cycloaddition reactions and it highly effect the rate of cycloaddition reaction. - we studied also the biological activity of nitrone and isoxazolidine compounds.