Asymmetric bias generated by protected vicinal diol controller and its application to asymmetric nitrone-olefin cycloaddition reactions

In order to achieve the diastereo-differentiation of pi-faces, we have developed the protected vicinal-diol controller. The striking successes in stereocontrol of diverse organic reactions have been recorded for which the diastereofacial bias constructed by such diol controller should be responsible. We refer to this topological situation as "outside-inside bias". This review summarizes the application of this concept to nitrone-olefin [3+2] cycloaddition reactions which resulted in considerable successes in stereocontrol again, and covers three topics, (1) the substrate-controlled intermolecular asymmetric cycloaddition reactions, (2) intramolecular 1,3-dipolar cycloaddition reactions of chiral alkenylnitrones, and (3) the synthesis of cyclic chiral nitrones and its intermolecular asymmetric cycloaddition reactions with various olefins. The role of the vicinal diol controller in these processes has been delineated.