Concise Construction of the Tricyclic Core of Bullataketals Enabled by a Biomimetic Intermolecular (3+3) Type Cycloaddition

A remarkable TFA-mediated method for the construction of a biologically interesting tricyclic ketal skeleton was uncovered by starting from a variety of readily available acylphloroglucinol and diacylphloroglucinol substrates. This approach, which mimics a biosynthetic olefin isomerization/hemiacetalization/dehydration/(3 + 3) type cycloaddition sequence through a 2H-furan-1-ium intermediate, establishes a viable synthetic strategy for efficient synthesis of bullataketals analogs.