Highly Effective Chirality Controlling Systems.

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1.Chiral 2-Oxazolidinones and 2-Imidazolidinones Auxiliaries.Both enantiomers of sterically congested 2-oxazolidinones and 2-imidazolidinones, which served as efficient chiral auxiliaries, were synthesized by [4+2] cycloaddition of cyclic dienes with 2-oxazolone and 2-imidazolone. The utilities of these auxiliaries in asymmetric synthetic reactions such as alkylations, the Diels-Alder reactions, michael reactions and aldol reactions were revealed.2.Conformationally Fixed 2-Amino Alcohols.The 2-oxazolidinones, mentioned above, were hydrolyzed to conformationally fixed 2-amino alcohols of synthetic significance.(1) N,N-Dialkylamino alcohols and N-sulfonylamino alcohols served as equally effective catalysts in ethylation of aldehydes with ZnEt_2, but showed completely reversed enantioselectivity.(2) Lithium salts of N-sulfonylamino alcohols cleaved meso-dicarboxylic anhydrides to the half esters with almost perfect diastereoselectivity. In contrast, zinc salts reacted with the anhydrides with opposite selectivity.