Enantioselective synthesis of isoquinoline alkaloids: phenylethylisoquinoline and aporphine alkaloids

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Abstract
A new and improved procedure for the preparation of (R)-2-alkoxycarbonyl-1-formyl-1,2,3,4-tetrahydro-6,7-dimethoxyisoquinolines has been developed beginning from D-(−)-tartaric acid. The utility of these aldehydes in the asymmetric synthesis of isoquinoline alkaloids of high enantiomeric purity has been extended to the synthesis of phenylethylisoquinolines, which have been further transformed in straightforward steps into the homoprotoberberine and homoaporphine ring systems. In this manner, (S)-homolaudanosine, (S)-5′-methoxyhomolaudanosine, (S)-2,3,9,10,11-pentamethoxyhomoprotoberberine, and (S)-O-methylkreysigine have been synthesized. The conversion of (S)-laudanosine to (S)-glaucine, an aporphine alkaloid, has also been realized.