Synthesis of (±)-Vibralactone

Reductive alkylation of methyl 2-methoxybenzoate with prenyl bromide and hydrolysis afforded methyl 6-oxo-1-prenyl-2-cyclohexenecarboxylate.
Reduction of the ketone, hydrolysis, iodolactonization, ozonolysis, and intramolecular aldol reaction provided a spiro lactone cyclopentenal.
Retro-iodolactonization with activated Zn, formation of the β-lactone, and reduction of the aldehyde completed an efficient first synthesis of
(±)-vibralactone. No protecting groups were used except for the novel use of an iodolactone to protect both the prenyl double bond and
carboxylic acid.