Development of Efficient Chiral Synthetic Process of Bioactive Compounds.

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1.Development of Diastereoselective Procedures.(1) 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) The 2-oxazolidinones were hydrolyzed to conformationally fixed 2-amino alcohols of synthetic significance. The lithium salts of N-sulfonyl derivative of amino alcohols thus obtained cleaved meso-dicarboxylic anhydrides to the half esters with almost perfect diastereoselectivity. In contrast, zinc salts reacted with the anhydrides with opposite selectivity.2.Development of Enantioselective Procedures.N,N-Dialkylamino alcohols and N-sulfonylamino alcohols which were derived from ringcleavage of the 2-oxazolidinones served as equally effective catalysts in ethylation of aldehydes with ZnEt_2, but interestingly showed completely reversed enantioselectivity.