Studies on flavans. 1. Facile synthesis of (+/-)-7-hydroxy-3',4'-methylenedioxyflavan and (+/-)-4'-hydroxy-7-methoxyflavan by a BF3.Et2O-mediated pyran cyclization.
A facile approach for the synthesis of flavans was developed by employing a BF3.Et2O-catalyzed pyran cyclization in an aprotic polar solvent as a key step, by which concise total syntheses of (+/-)-7-hydroxy-3',4'-methylenedioxyflavan (1) and (+/-)-4'-hydroxy-7-methoxyflavan (2), two naturally occurring flavans, were achieved.
Li
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National Laboratory of Applied Organic Chemistry & Institute of Organic Chemistry, Lanzhou University, Lanzhou, Gansu 730000, People's Republic of China. liyl@lzu.edu.cn
Yang
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Li
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WZ
Hou
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Xue
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Li
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D003500:Cyclization; D005419:Flavonoids / Q000138:chemical synthesis*; D008956:Models, Chemical
C433580:4'-hydroxy-7-methoxyflavan; C107721:7-hydroxy-3',4'-(methylenedioxy)flavan; D005419:Flavonoids