Determination of Absolute Stereochemistry and an Alternative Synthesis of Homopumiliotoxin 223G: Identification on Chiral GC Columns with the Natural Alkaloid
作者:Chihiro Kibayashi、Sakae Aoyagi、Tzu-Chueh Wang、Kosuke Saito、John W. Daly、Thomas F. Spande
DOI:10.1021/np990641b
日期:2000.8.1
The same sequence using (+/-)-4 was applied to the synthesis of racemic 223G. Gas chromatography of a sample of racemic 223G showed no separation into enantiomers on four different cyclodextrin-based chiral GC columns. We found, however, that the O-acetates of (+/-)-223G gave a nearly baseline separation on either a beta-cyclodextrin column or a permethylated beta-cyclodextrin column. The O-acetate of
通过(1R,2R,9aS)-1-(苄氧基)-2-羟基-1-甲基-3 [[[E) -异丁烯基] ++ +喹啉基二烯(4),其根据分子内镍(II)/铬(II)介导的N-(碘烯基)醛2的环化反应合成。将化合物4转化为乙酸酯并进行处理用氨中的锂还原,然后在一次操作中使O-苄基脱保护并除去乙酰氧基,得到(+)-全铝毒素223G。使用(+/-)-4的相同序列应用于外消旋223G的合成。消旋223G样品的气相色谱分析表明,在四种基于环糊精的手性GC色谱柱上未分离成对映体。但是,我们发现 (+/-)-223G的O-乙酸盐在β-环糊精色谱柱或过甲基化的β-环糊精色谱柱上产生了接近基线的分离。合成(+)-223G的O-乙酸盐在这两根色谱柱中均相同,首先是从乙酰化(+/-)-223G洗脱出O-乙酸盐,然后是蛙皮提取物中存在的乙酰化223G。使我们能够明确确认天然223G的1S,9aS绝对构型。