AbstractRacemic 1‐(5‐benzyloxy‐4‐methoxy‐2‐methylbenzyl)‐1,2,3,4‐tetrahydro‐6‐methoxyisoquinoline (rac.3) was synthesized (Scheme 1). Resolution with (+)‐ and with (‐)‐6,6′‐dinitrobiphenyl‐2,2′‐dicarboxylic acid yielded (‐)‐ and (+)‐3, respectively. By a Birch reduction, followed byN‐formylation, and by acid‐catalysed cyclization, we obtained in high yield racemic, (‐)‐, and (+)‐N‐formyl‐1‐methylnordihydrothebainone (6), respectively. In two ways, by direct reduction and by deformylation followed by reductive methylation,6could be converted selectively into racemic, and (‐)‐, and (+)‐1‐methyldihydrothebainone (7).Synthetic (‐)‐7was found to be identical with (‐)‐1‐methyldihydrothebainone prepared from natural material. This completes the p