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Monday, August 29, 2016
Douglass F. Taber
University of Delaware

Carbocyclic Construction: Aquatolide (Hiemstra), Spongiolactone (Romo), Ar-Tenuifolene (Ávila-Zárraga), Antroquinonol (Weng/Chen), (Z)-2β-Hydroxy-14-hydro-β-Santalol (Ishigami), Cortistatin A (Chiu)

The structure of Aquatolide, isolated from the Mediterranean flower Asteriscus aquaticus, was recently corrected to 3. Henk Hiemstra of the University of Amsterdam devised (Org. Lett. 2015, 17, 3892. ) a synthesis of 3 based on the elegant photocyclization of 1 to 2.

Spongiolactone (7), isolated from Spongionella gracilis, shows antineoplastic activity. The key step in the synthesis of 7 reported (Chem. Eur. J. 2015, 21, 1425. ) by Daniel Romo of Texas A&M was the diastereoselective cyclization of 4 to 6, mediated by 5.

In the course of a synthesis of Ar-Tenuifolene (10), José Gustavo Ávila-Zárraga of the Universidad Autónoma de México reported (Tetrahedron Lett. 2015, 56, 5321. ) the remarkable thermal rearrangement of 8 to 9. It would be interesting to explore the generality of this transformation.

Antroquinonol (13), from Antrodia camphorata, is an effective anti-diabetic agent. In the course of a synthesis of 13, Ching-Feng Weng and Chinpiao Chen of the National Dong Hwa University observed (J. Org. Chem. 2015, 80, 6044. ) significant diastereoselectivity in the radical cyclization of 11 to 12.

The sesquiterpene (Z)-2β-Hydroxy-14-hydro-β-santalol (16) is a potent inhibitor of Helicobacter pylori, a major causitive factor of gastric ulcers and cancer. En route to 16, Ken Ishigami of the University of Tokyo effected (Tetrahedron Lett. 2015, 56, 5816. ) the cascade radical cyclization of 14 to 15.

Cortistatin A (19), isolated from the marine sponge Corticium simplex, has potent antiangiogenic activity. Pauline Chiu of the University of Hong Kong designed (Chem. Eur. J. 2015, 21, 14287. ) the intramolecular dipolar cycloaddition of the oxallyl cation derived from 17 to prepare 18, that could be carried on to 19.

D. F. Taber, Org. Chem. Highlights 2016, August 29.
URL: http://www.organic-chemistry.org/Highlights/2016/29August.shtm