1. D. R. Hirschfeld, W. Fenical, G. H. Y. Lin, R. M. Wing, P. Radlick and J. J. Sims, J. Am. chem. Soc.95, 4049 (1973).
2. L. Minale and R. Riccio, Tetrahedron Lett.1976, 2711.
3. E. Fattorusso, S. Magno, L. Mayol, C. Santacroce, D. Sica, V. Amico, G. Oriente, M. Piattelli and C. Tringali, J. C. S. Chem. Commun.1976, 575.
4. 20 g of crude extract from the digestive glands of 3 adult sea hares yielded 170 mg of dictyol C (4) and 250 mg of dictyol D (5);4 and5 were also obtained from D. dichotoma in 0.1 and 0.01% yield of the dry material, respectively; D, ligutatus furnished dictyol E (6) in 0.5% yield.
5. Mass spectral data;4, m/e 306 (2, M+), 288 (18), 270 (49), 177 (71), 175 (51), 159 (47) and 69 (100);5, m/e 304 (3, M+), 286 (2), 268 (3), 175 (7), 173 (6), 157 (10) and 69 (100).