A novel asymmetric synthesis of 1-aryl-1,2,3,4-tetrahy-sodium in liquid ammonia and ammonium cerium(IV) nitrate, respectively, to yield the primary amines 35 and 36. The acid-droisoquinolines has been developed. The key step in this synthesis is the diastereoselective addition of homochiral (2-catalysed cyclization of the sulfonamides 26d and 27d and the carbamates 37 and 38, prepared from 35 and 36, leads lithiophenyl)acetaldehyde acetals to the sulfonylimine 25 and to the arylimines 28 and 31. The best diastereoselectivity to the enantiomerically pure dihydroisoquinolines 40 and 41, respectively. During the cyclization of the sulfonamides 26d, is obtained by addition of the bis(2-methoxypropan-2-yl)substituted 1,3-dioxolane 6e to benzylidene-p-anisidine (31) 27d and the carbamates 37, 38 the chiral auxiliary -the diol 39 -is cleaved unchanged and can be recovered in good with an HPLC-determined diastereomeric ratio 32c/33c = 92.1:7.9. The N-tosyl and the N-(4-methoxyphenyl) groups of yields. the addition products 26d, 27d, 32c, and 33c are cleaved with [ ] Part 3: Ref. [20] [a] Pharmazeutisches Institut der Universität Freiburg, (TADDOLs) [16] was elaborated. Reaction of the p-meth-Hermann-Herder-Straße 9, D-79104 Freiburg i. Br., Germany oxybenzaldehyde acetal 18 with excess ethylmagnesium