2. Results and discussionAs depicte

2. Results and discussion
As depicted in the retrosynthetic Scheme 2, an ene reaction
based approach was conceived for the construction of the sevenmembered
ring of aciphyllenes 1, 5e7 starting from the readily
available monoterpene (R)-limonene 8. It was anticipated that type
II carbonyl ene reaction of the aldehyde 9 would generate the bicyclic
alcohol 10, which could be further elaborated into aciphyllenes.
The aldehyde 9 could be obtained from the ester 11,
which in turn could be obtained from the aldehyde 12. A two-step
(controlled ozonolysis followed by intramolecular aldol condensation)
conversion of (R)-limonene 8 into the aldehyde 12 has
already been developed by us.11a