1. B. Gilbert, L. D. Antonaccio, A. A. P. G. Archer, andC. Djerassi, Exper.16, 61 (1960).
2. For definition of δ, see1, as well asC. Djerassi, T. Nakano, A. N. James, L. H. Zalkow, E. J. Eisenbraun, andJ. N. Shoolery, J. org. Chem., in press.
3. SeeJ. R. Chalmers, H. T. Openshaw, andG. F. Smith, J. chem. Soc.1957, 115.
4. K. Biemann, Tetrahedron Letters No. 15, 9 (1960).
5. K. Biemann andM. Friedmann-Spitteler, Tetrahedron Letters, in press.