Unveiling the 6,8-Rearrangement in 8-Phenyl-5,7-dihydroxyflavylium and 8-Methyl-5,7-dihydroxyflavylium through Host-Guest Complexation
作者:Nuno Basílio、João Carlos Lima、Luís Cruz、Victor de Freitas、Fernando Pina、Hiroki Ando、Yuki Kimura、Kin-Ichi Oyama、Kumi Yoshida
DOI:10.1002/ejoc.201701009
日期:2017.10.10
quinoidal bases are the stable species and some evidence for the 6,8-rearrangement was obtained, but the respective spectral variations are very small. This was overcome by using a modified cyclodextrin (captisol), which favors the formation of the trans-chalcone at the expense of the quinoidal bases. The trans-chalcone was isolated and dissolved in CD3OD/DCl (pD < 1) to give a mixture of the two flavylium
合成了 8-Phenyl-5,7-dihydroxyflavylium 和 8-methyl-5,7-dihydroxyflavylium 以观察 6,8-重排。通过 8-碘黄素的 Suzuki-Miyaura 反应引入 8-苯基和 8-甲基残基,然后用 LiAlH4 还原得到相应的 3-脱氧花色素。在 pH 1.0 时,稳定形式是两种化合物中的 8-取代黄鎓阳离子。在较高的 pH 值下,醌型碱是稳定的物种,并且获得了 6,8-重排的一些证据,但各自的光谱变化非常小。这可以通过使用改性环糊精(captisol)来克服,该环糊精有利于反式查耳酮的形成,而牺牲了醌型碱。将反式查耳酮分离并溶解在 CD3OD/DCl (pD < 1) 中,得到两种黄鎓异构体的混合物。这通过 HPLC 分离后两种异构体的 ESI-MS 分析(以正离子模式记录)得到证实,得到相同的峰 ([M]+ m/z 253)。6