1. 2) J. Asakawa, R. Kasai, K. Yamasaki and O. Tanaka, Tetrahedron, 33, 1935 (1977).
2. 3) J.B. Stothers, "Carbon-13 NMR Spectroscopy," Academic Press, New York, 1972.
3. 4) H. Beierbeck, J.K. Saunders and J.W. ApSimon, Can. J. Chem. 55, 2813 (1977).
4. 5) A negative sign denotes an upfield shift on substitution.
5. 6) S. Seo, Y. Tomita and K. Tori, Tetrahedron Lett., 1975, 7.