Molecular rearrangement of photoparthenin by BF₃-etherate-acetic acid complex: X-ray crystal structure of a novel product

Abstract

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 dimensionsa=8.444(1),b=9.964(2),c=16.239(2) Å,V=1366.3(2) ų,Z=4,M_r =262.3,D _o=1.29,D x=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.