Structural Revision of the Hancock Alkaloid (-)-Galipeine.
Davies SG., Fletcher AM., Houlsby ITT., Roberts PM., Thomson JE.
The 1H and 13C NMR data of synthetic samples of (S)-N(1)-methyl-2-[2'-(3″-hydroxy-4″-methoxyphenyl)ethyl]-1,2,3,4-tetrahydroquinoline, the originally proposed structure of the Hancock alkaloid (-)-galipeine, do not match those of the natural product. Herein, the preparation of the regioisomer (S)-N(1)-methyl-2-[2'-(3″-methoxy-4″-hydroxyphenyl)ethyl]-1,2,3,4-tetrahydroquinoline is reported, the 1H and 13C NMR data of which are in excellent agreement with those of (-)-galipeine. Comparison of specific rotation data enables assignment of the absolute (S)-configuration of the alkaloid, and together, these data engender the structural revision of (-)-galipeine to (S)-N(1)-methyl-2-[2'-(3″-methoxy-4″-hydroxyphenyl)ethyl]-1,2,3,4-tetrahydroquinoline.