CHELATE-CONTROLLED AND NON-CHELATE-CONTROLLED REDUCTIONS OF BETA-AMINO KETONES - SYNTHESIS OF NON-RACEMIC 1,3-AMINO ALCOHOLS WITH PYRROLIDINE STRUCTURE

[摘要] The reduction of the amidoketones (R)-1 and (S)-2 has been achieved in a stereocontrolled manner giving either the product with like- or unlike configuration depending upon the reducing agent employed. Thus with Li(O(t)Bu)3AlH the amidoalcohols (R,R)-3 and (S,S)-5 were the major diastereomers formed whereas with K((s)Bu)3BH (R,S)-4 and (S,R)-6 dominated. Stereoselectivities up to 98/2 were observed. As a mechanistic rationale for the change of direction in the asymmetric induction a chelate- and non-chelate-model have been envoked. By including (rac)-9 in this study having a non chiral acyl group it was found that the chiral auxiliary in (R)-1/(S)-2 is essential for a high asymmetric induction under chelate- but not under non-chelate-control. Hydrolysis of the amidoalcohols provided the corresponding 1,3-aminoalcohols (R,R)-12, (S,S)-12, (R,S)-13 and (S,R)-13. The configuration of these compounds has been assigned by means of H-1 NMR spectroscopy.

[发布日期] 1991-03-11