Total Synthesis of a PPAP, Nemorosonol, Using a Tandem Michael Addition–Intramolecular Aldol Reaction

A strategy for constructing a tricyclo[4.3.1.03,7]decane skeleton, which is common to many polycyclic polyprenylated acylphloroglucinols, has been established. The key step was a tandem Michael addition-intramolecular aldol reaction with 3-ethoxy-1-phenyl-2-proyn-1-one, which affords a tricyclo[4.3.1.03,7]decane skeleton having a benzoyl group at the C8 position and an appropriate oxygen functional group at the C9 position. This synthetic strategy led to the total synthesis of nemorosonol, which was accomplished in 12 steps from 2-methyl-2-cyclopenten-1-one.