5-8-5 ring systems are widely occurring in nature but
their syntheses have been hampered by inherent ring
strain and transannular interactions of the eight-membered
ring system. A novel strategy, which involves
a [2+2]-photocycloaddition of highly functionalized
cyclobutenes and cyclopentenones, followed by a thermolytic
fragmentation of the resulting strained photoadducts
was developed in our laboratory. With this
the desired 5-8-5 ring systems can be constructed in
as few as six steps from commercially available materials.
Currently, the intramolecular modification of
the methodology is being applied to the total synthesis
of a diterpenoid natural product, cycloaraneosene.
Fragmentation Approach toward 5-8-5 Ring Systems”
Priscilla C.-K. Lo, Marc L. Snapper Org. Lett.
2001, 3, 2819-2821.
A New Entry into Functionalized 5-8-5 Ring Systems”
Michele L. Randall, Priscilla C.-K. Lo, Peter J. Bonitatebus,
Jr., Marc L. Snapper J. Am. Chem. Soc. 1999,