Reversal of regioselection in the sharpless asymmetric aminohydroxylation of aryl ester substrates

[GRAPHICS] The asymmetric synthesis of beta-hydroxy-alpha-amino acids is reported whic h relies on the use of alpha,beta-unsaturated aryl eater substrates and the dihydroquinyl alkaloid ligand system (DHQ)(2)-AQN to control the regio- an d enantioselectivity of the asymmetric aminohydroxylation (AA) process. alp ha,beta-unsaturated ester substrates of type 1 have a significant effect on the substrate-ligand recognition event which results in a reversal of regi oselectivity in the AA reaction.