After optimization of the reaction conditions, optically pure S(+) DABA is obtained in more than 80% overall yield. A model is proposed to explain the dependence of asymmetric induction on the nature of the counter ion (Li + , Mg ++ , Bu 4 N + ). ... Optically pure S(+) DABA (100% AI in the key step) is obtained in more than 80% yield. A model is proposed to explain the dependence of asymmetric induction on the nature of the counter ion (Li + , Mg ++ , Bu 4 N + ).