MOLECULAR REARRANGEMENT OF PHOTOPARTHENIN BY BF3-ETHERATE-ACETIC ACID COMPLEX - X-RAY CRYSTAL-STRUCTURE OF A NOVEL PRODUCT

The structure of a novel compound, Iupac name: bicyclo [2.4.0]-octa-1,3-dimethyl-2,3-pentan-9-methylene-8, 10-butan-diolide, which resulted on treatment of photoparthenin with BF3-etherate acetic acid, has been established uniquely by X-ray crystallography. C15H18O4 is orthorhombic, space group P212121, with the cell dimensions a=8.444(1), b=9.964(2), c=16.239(2) Å, V=1366.3(2) Å3, Z=4, Mr=262.3, Do=1.29, Dx=1.28 g cm-3, F(000)=560, T=293K, R=0.065 for 818 observed reflections. δ-lactone ring has a skew-boat, γ-lactone ring has an envelope, and the remaining six-membered ring has a distorted chair conformation. The four-membered ring is nonplanar. There are two intramolecular and one intermolecular short C-H⋯O interactions 2.819, 2.834, and 3.259 Å, respectively, which stabilize the crystal structure. © 1990 Plenum Publishing Corporation.