STRUCTURE OF CHELONAPLYSIN-C - A SPONGIAN DITERPENOID FROM NUDIBRANCH CHROMODORIS-LUTEOROSEA

8-[ 1 -(Octahydro-4,4,7a-trimethyl- 1 H-inden-1 -yl)ethenyl]-3-oxo-2,7-dioxabicyclo[3.2. 1 ]octan-6-yl acetate, C22H32O5, M(r) = 376.5, orthorhombic, P2(1)2(1)2(1), a = 8.3737 (8), b = 10.6469 (8), c = 22.429 (2) angstrom, V = 1999.7 (3) angstrom3, Z = 4, D(x) = 1.251 Mg m -3, lambda(Cu Kalpha) = 1.54178 angstrom, mu = 0.67 mm-1, F(000) = 816, room temperature, final R = 0.046 for 2181 reflections with I greater-than-or-equal-to 2.5sigma(I) and 245 variables. The X-ray analysis confirms the novel rearranged diterpenoid skeleton proposed by Bobzin & Faulkner [J. Nat. Prod. (1991), 54, 225-232] on the basis of spectral data and chemical correlations.