1. F. Cafieri, E. Fattorusso, S. Magno, C. Santacroce andD. Sica, Tetrahedron29, 4259 (1973).
2. E. Fattorusso, S. Magno, L. Mayol, C. Santacroce andD. Sica, Tetrahedron31, 269 (1975).
3. Mass spectra and accurate mass measurements were obtained with an AEI MS 902 spectrometer by using the direct inlet technique.
4. IR spectra were recorded on a Perkin-Elmer 157 instrument in CCl4.
5. NMR spectra were taken in CCl4 on a Perkin-Elmer R 32 apparatus (internal reference TMS); s denotes a singlet, d a doublet, m a multiplet, broad.