An Unexpected Lewis Acid-Catalyzed Cascade during the Synthesis of the DEF-Benzoxocin Ring System of Nogalamycin and Menogaril: Mechanistic Elucidation by Intermediate Trapping Experiments and Density Functional Theory Studies.

An unexpected Lewis acid-catalyzed carbohydrate rearrangement of a 1,5-bis-glycopyranoside to the product of a formal intramolecular