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Asymmetric Induction in 8π Electrocyclizations. Design of a Removable Chiral Auxiliary

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journal contribution
posted on 06.01.2012, 00:00 by Keunsoo Kim, Joseph W. Lauher, Kathlyn A. Parker
The pseudo C2 symmetric trans diphenyl oxazoline group acts as an effective chiral auxiliary in the 8π, 6π tandem electrocyclization of a substituted tetraene 1-carboxylic acid. Assignment of absolute stereochemistry to the [4.2.0] bicyclooctadiene product supports a model in which both s-cis and s-trans conformations favor the transition states with the same helical twist. This assignment prefaces the development of analogs of SNF4435 C and D. These natural products demonstrate activity as androgen receptor antagonists and as multidrug resistance (mdr) reversal agents.