Acetogenic Isoquinoline Alkaloids, L. The Synthesis of All Possible Isomeric 6,8‐Dioxygenated 1,3‐Dimethyl‐1,2,3,4‐tetrahydroisoquinoline Methyl Ethers – Useful Chiral Building Blocks for Naphthylisoquinoline Alkaloids

The practicable synthesis of all imaginable isomeric heterocyclic moieties 8 – 11 and ent ‐ 8 – ent ‐ 11 of the naphthylisoquinoline alkaloids is described. The stereoinformation at C‐3 is induced by asymmetric reductive amination, using 1‐phenylethylamines of either enantiomeric series as chiral auxiliaries. The key step of the stereocontrolled construction of the stereocenter at C‐1 is the diastereoselective reduction of the corresponding dihydroisoquinolines, as obtained by Bischler‐Napieralski synthesis, or the regio‐ and stereoselective Pictet‐Spengler reaction of arylisopropylamines with acetaldehyde, respectively.