Total synthesis of demethylwedelolactone and wedelolactone by Cu-mediated/Pd(0)-catalysis and oxidative-cyclization
作者:Chia-Fu Chang、Ling-Yi Yang、Shiao-Wei Chang、Yu-Ting Fang、Yean-Jang Lee
DOI:10.1016/j.tet.2008.02.031
日期:2008.4
Hedysarimcoumestan B, which can be isolated from Chinese herbal medicine, is achieved, in which the longest linear sequence is only eight steps, in 50% overall yield from commercially available phloroglucinol. The key transformations in the synthesis are Cu-mediated/Pd(0)-catalysis and I-2/pyridine oxidative-cyclization reactions. This synthetic strategy can be applied to give access to the demethylwedelolactone (4) and wedelolactone (5), which were afforded from commercially available phloroglucinol in high 38 and 33% yields, respectively. (c) 2008 Elsevier Ltd. All rights reserved.
Synthesis of Coumestan Derivatives via FeCl<sub>3</sub>-Mediated Oxidative Ring Closure of 4-Hydroxy Coumarins
A concise and efficient approach to the syntheses of coumestan analogues has been developed. The underpinning strategy involves a FeCl3-mediated direct intramolecular oxidative annellation of 4-hydroxy-3-phenyl-2H-chromen-2-one derivatives. Utilizing this synthetic protocol, a variety of coumestan derivatives were conveniently obtained from readily available reagents.