Catalytic Asymmetric Synthesis of (R)-(-)-Calycotomine, (S)-(-)-Salsolidine and (S)-(-)-Carnegine

A simple and efficient procedure for a synthesis of isoquinoline alkaloids is described. The key step of the synthesis was a hydrocyanation of 6,7-dimethoxy-3,4-dihydroisoqunoline giving the corresponding 1-cyano-1,2,3,4-tetrahydroisoquinoline. The asymmetric Strecker reaction was accomplished in high yield and high enantiomeric excess using Jacobsen’s thiourea-containing ­catalyst. The 1-cyanoisoquinoline thus obtained was transformed to natural products, (R)-(-)-calycotomine, (S)-(-)-salsolidine and (S)-(-)-carnegine.