1. A. N. Tackie, D. Dwuma-Badu, T. Okarter, J. E. Knapp, D. J. Slatkin andP. L. Schiff, jr., Lloydia37, 1 (1974).
2. I. R. C. Bigk andA. R. Todd, J. chem. Soc.1950, 1606.
3. Y. Inubushi andK. Nomura, Tetrahedron Lett.1962, 1133.
4. I. R. C. Bick, J. B. Bremner, H. M. Leow andP. Wiriyachitra, J. chem. Soc. Perkin I1972, 2884.
5. M. Shamma,The Isoquinoline Alkaloids (Academic Press, New York 1972), p. 81.