Edge Article
Chemical Science
isopropenyl group in 24 (highlighted in red) proved to be totally
inert toward RCM conditions, ensuring high topological selec-
tivity for the desired ring closure. Interestingly, the crystal
structure of 24 reveals that one of the double bonds (highlighted
in purple) prefers to lie out of conjugation with the remainder of
the pi system, likely due to the considerable strain it imposes on
the central ring. Strategies to advance intermediate 24 to curcu-
sone C (3) and its structural congeners are currently under
thorough investigation in our group.
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Scheme 7 Construction of tricycle 24 via an RCM approach.
11564–11567.
1
1
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Conclusions
2446–2449.
In summary, we have presented recent progress toward the 13 S. G. Levine, J. Am. Chem. Soc., 1958, 80, 6150–6151.
synthesis of curcusones A–D. In our efforts, we have notably 14 W. C. Still, J. Am. Chem. Soc., 1978, 100, 1481–1487.
achieved the rst synthesis of the carbocyclic framework 15 O. H. Oldenziel, D. Van Leusen and A. M. Van Leusen, J. Org.
embedded in curcusones A–J in only nine steps. Crucial to the
success of this route is a cross-electrophile coupling approach, 16 E. J. Kantorowski and M. J. Kurth, Tetrahedron, 2000, 56,
which can be performed on multigram scales. In light of these
4317–4353.
results, we anticipate that this reductive coupling protocol will 17 N. Marion, S. D ´ı ez-Gonz ´a lez and S. P. Nolan, Angew. Chem.,
Chem., 1977, 42, 3114–3118.
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18 The following 1,2-adducts were obtained in roughly equal
proportions:
Conflicts of interest
There are no conicts to declare.
Acknowledgements
Caltech and the NSF (1800511) are thanked for supplying
funding. Dr Scott Virgil is gratefully acknowledged for puri-
cation and crystallization expertise. We thank Dr Michael
Takase and Dr Lawrence Henling for collecting X-ray crystallo-
graphic data. Dr Steven Loskot and Nicholas Hafeman are
acknowledged for helpful discussions.
1
9 (a) J. H. Babler and M. J. Coghlan, Synth. Commun., 1976, 6,
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2
0 The following aldehyde isomer was continually observed as
a minor byproduct from the oxidative transposition:
Notes and references
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Chem. Sci., 2019, 10, 10562–10565 | 10565