Unique cyclolignan’s architecture obtained via acid catalyzed cyclization/intramolecular Friedel-Crafts tandem reaction

We examine the cyclization of chiral bis-benzylidenesuccinate 6 (precursor to podophyllotoxin-related cyclolignans) in different conditions. Under acid catalysis, a new type of cyclolignan was obtained via cyclization/intramolecular Friedel-Crafts tandem reaction. The structure of the product was confirmed by spectroscopic data and X-ray diffraction. Also, a plausible mechanism of this transformation was proposed.