THE CONSTITUENTS OF MARINE SPONGES .9. NEW NORDITERPENOIDS FROM APLYSILLA-PALLIDA

Four novel norditerpenoids were isolated from a new encrusting sponge, conveniently labelled Aplysilla pallida. The structures of aplypallid enone (1), aplypallidoxone (2), aplypallidione (3) and aplypallidioxon e (4) were elucidated by spectroscopic studies and the crystal structu res of aplypallidenone and aplypallidoxone have been determined by X-r ay diffraction methods. The structure of (1) was refined to a residual of 0.040 for 1665 independent observed reflections and the structure of (2) was refined to a residual of 0.031 for 1699 independent observe d reflections. The crystals of (1) are orthorhombic, space group P2(1) 2(1)2(1), a 7.728(2), b 10.838(4), c 24.880(5) Angstrom, Z 4. Those of (2) are monoclinic, space group C2, a 23.927(7), b 6.674(2), c 14.033 (3) Angstrom, Z 4.