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Concise asymmetric synthesis of (-)-Bao Gong Teng A via Evans chiral auxiliary-based 1,3-dipolar cycloaddition
Yi-Wen Zhao1, Jun-Fei Wang1, Jianrong Xu2
1The Research Center of Chiral Drugs, Innovation Research Institute of Traditional Chinese Medicine, Shanghai University of Traditional Chinese Medicine, 1200 Cailun Road, Shanghai 201203, China. tanyx1993@shutcm.edu.cn.
Abstract:
We present a concise asymmetric synthesis of (-)-Bao Gong Teng A, a 2-hydroxylated tropane alkaloid with hypotensive and miotic activities isolated from the Chinese herb Erycibe obtusifolia Benth. Using an Evans chiral auxiliary, we achieve a regio- and stereoselective 1,3-dipolar cycloaddition between p-chlorobenzyl pyridinium salt and (R)-3-acryloyl-4-phenyloxazolidin-2-one, efficiently generating the tropane skeleton on a decagram scale. This methodology provides a rapid and practical synthesis of optically active (-)-Bao Gong Teng A for further biological studies.
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