TRICOCCIN R2

In the title compound, (3'S-{3'alpha,3'alpha beta,5'alpha alpha,7'alph a[R-(R*)],8'b 'alpha-tetrahydro-5,5-dimethylspiro[furan-2(3H),7' (4'H )-1H,3H-3 lpha,8b]methanobenzo[1,2-b:3,4-c']difuran)-1'-one, C25H26O7, some C-C bonds and C-C-C angles deviate significantly from their expe cted values. Both the terminal five-membered rings are nearly planar. The fused five-membered rings, B, C and E, have half-chair, distorted envelope and half-chair conformations, respectively. The six-membered ring is in a slightly distorted sofa conformation. The structure is st abilized by van der Waals interactions.