Syntheses of enantioenriched homoallylic hydroxylamines and ß-lactams using sugar template as the chiral auxiliary.

Abstract

The extensive occurrence of nitrogenated compounds in the nature and the promising outlook of synthesizing enantiomerically pure compounds in asymmetric reactions, the stereoselective additions to C=N bonds are now considered salient and fundamental reactions.The C=N functionalities are possible to determine the final products to be either amines (from imines and iminium salts) or hydroxylamines (from nitrones and oximes), which could later be transformed into useful building blocks like amino alcohols, amino acids and nitrogenated heterocycles such as isoxazolidine. A variety of nitrogen containing functional groups can be prepared by introducing the allyl moiety such as Grignard reagent or stannane reagent. The diastereoselective allylations can be performed in the presence of either a chiral lewis acid or a chiral auxiliary group. The discoveries of chiral Lewis acid systems and its applications are widely demonstrated in many papers; however, a very few examples of diastereoselective allylations are performed via chiral auxiliary group have been reported so far. Therefore, the development of allylation of nitrones using sugar template as a chiral auxiliary is highly desirable.