Asymmetric Total Synthesis of Gymnothespirolignan A via a Bioinspired Double Cyclization Approach
Hao Yang1, Zhengyi Qin1, Xinyu Liang1
1State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, Gansu, P. R. China.
Abstract:
The first asymmetric total synthesis of gymnothespirolignan A is disclosed in 11 steps. The salient feature of the synthesis is construction of the spirocyclic moiety through a bioinspired acid-promoted double cyclization of an acyclic gymnothebutyllignan A-like precursor, which involves a deprotection, hemiketalization, dehydrative oxonium formation, and Friedel-Crafts cyclization cascade transformation. This study provides a general approach to the asymmetric syntheses of novel spirocyclic gymnothelignans.
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