Abstract: Cyclo(L-Phe-L-His)prepared by a modified procedure showed high activity. and enan-tioselectivity in the asymmetric synthesis of aromatic Cyanohydrins from benzaldehyde andm-phenoxybenzaldehyde. The influence of the reaction conditions on the activity and sele-ctivity of the dipeptide has been investigated. The cyclodipeptide can be easily recoveredand reused without any loss of the catalytic activity. The optical and chemical stabilityas well as the relationship between the aggregation and properties of the catalyst have beendiscussed.

Key words: optically active cyanohydrin, cyclic dipeptide, asymmetric synthesis