Novel non-azacyclo 1,2-aminoalcohols derived from L-Phe and highly enantio selective addition of diethylzinc to aryl aldehydes

A series of non-azacyclo beta-aminoalcohols derived from natural L-phenylalanine were readily synthesized in three steps. They were used as chiral ligands in the catalytic asymmetric addition of diethylzinc to aldehydes. The results showed that ligands with diethyl or dipropyl substituents on the carbinol carbons of the aminoalcohols favored higher enantioselectivities, and ligands with N,N-dimethyl groups gave better asymmetric induction than other NN-dialkyl substituted ligands. Compound 5b was the most optimal ligand among these aminoalcohols, allowing to obtain a 96% ee. The results showed that high en antioselection should be determined by the subtle combination of the carbinol parts and amino parts of the aminoalcohols. (c) 2005 Elsevier B.V. All rights reserved.