The aromatic bisabolene sesquiterpene of marine origin (+)-7,11-helianane (1) and its moderately cytotoxic halogenated relative (+)-5-chloro-7,11-helianane (3) have been synthesized by a concise, stereoselective route. By capitalizing on a palladium-catalyzed asymmetric allylic alkylation (Pd-AAA)reaction, followed by a thermal(uncatalyzed) aromatic Claisen rearrangement, which allowed for the installation of the required benzylic stereocenter, the aforementioned natural products were secured in 80%ee, with almost complete transfer of stereochemical information during the [3,3] sigmatropic process. The enantioselective total synthesis confirmed the recently proved (S) absolute configuration for (+)-7,11-helianane (1) and demonstrated the same configuration, for the first time, in the case of (+)-5-chloro-7,11-helianane (3).
Total Synthesis of (+)-7,11-Helianane and (+)-5-Chloro-7,11-helianane through Stereoselective Aromatic Claisen Rearrangement / F. Quartieri, L. E. Mesiano, D. Borghi, V. Desperati,C. Gennari,G. Papeo. - In: EUROPEAN JOURNAL OF ORGANIC CHEMISTRY. - ISSN 1434-193X. - 2011:33(2011), pp. 6794-6801. [10.1002/ejoc.201100706]
Total Synthesis of (+)-7,11-Helianane and (+)-5-Chloro-7,11-helianane through Stereoselective Aromatic Claisen Rearrangement
C. GennariPenultimo
;
2011
Abstract
The aromatic bisabolene sesquiterpene of marine origin (+)-7,11-helianane (1) and its moderately cytotoxic halogenated relative (+)-5-chloro-7,11-helianane (3) have been synthesized by a concise, stereoselective route. By capitalizing on a palladium-catalyzed asymmetric allylic alkylation (Pd-AAA)reaction, followed by a thermal(uncatalyzed) aromatic Claisen rearrangement, which allowed for the installation of the required benzylic stereocenter, the aforementioned natural products were secured in 80%ee, with almost complete transfer of stereochemical information during the [3,3] sigmatropic process. The enantioselective total synthesis confirmed the recently proved (S) absolute configuration for (+)-7,11-helianane (1) and demonstrated the same configuration, for the first time, in the case of (+)-5-chloro-7,11-helianane (3).Pubblicazioni consigliate
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