Asymmetric synthesis of (S)-1-(5-hydroxy-2-methoxy-benzyl)-7-hydroxy-6-methoxy-2-methyl-1,2,3,4-tetrahydroisoquinoline (so-called ''dehassiline'')

Optically active, (S)-1-(5-hydroxy-2-methoxybenzyl)-7-hydroxy-6-methoxy-2-methyl-1,2,3,4-tetrahydroisoquinoline (so-called ''dehassiline'') (1) was synthesized via highly stereoselective reduction of the 3,4-dihydroisoquinolinium ion possessing a chiral auxiliary by Polniaszek's method. The synthetic compound (1) was shown to be different from natural dehassiline, the structure of which should be revised.