A new method for the asymmetric synthesis of 1-substituted tetrahydroisoquinolines is presented. It is based on stereoselective addition reactions of organometalliccompounds to the intermediate N-acyliminium ion 6, which is provided with an N-acyl group as a chiral auxiliary. In addition reactions with organomagnesium and organozinc reagents diastereoselectivities from 70:30 to 95:5 (for 7/8) were