Tetrahydroisoquinoline alkaloids are often selected as synthetic targets due to their various physiological activities and structural properties. In the process, it was thought that the introduction of an electrophilic carbon unit at C-1 position would be of immense use due to its applicability as a reaction site of nucleophiles. Thus, we studied catalytic addition of a carbon unit at C-1 of 6,7-dimethoxy-3,4-dihydroisoquinoline, and Jacobsen's thiourea-containing organocatalyst was found to be efficient for asymmetric Strecker reaction. The reaction was accomplished in high yield and high enantiomeric excess to give a 1-cyanoisoquinoline. The 1-cyanoisoquinoline thus obtained was readily transformed to natural products. Applications of nucleophilic addition of an isoquinolinecarbaldehyde, which was converted from the 1-cyanoisoquinoline, to synthesis of other alkaloids were examined, and (+)-laudanosine was synthesized via Grignard reaction.
