摘要：

Thiol and disulfide derivatives of ephedrine have been shown previously to catalyse in high enantiomeric excess (ee) the reaction of diethyl zinc with benzaldehyde. We find that this reaction involves non-linear correlations between the ee of product and catalyst. Osmotic measurements indicate a high degree of aggregation of the zinc thiolates. The behaviour of the thiol derivatives deviates sharply from that of the oxygen analogue, N-methyl ephedrine.

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