Department of Materials Chemistry and Bioengineering, Oyama National College of Technology, Oyama, Tochigi 323-0806, Japan.
Chirality. 2012 Feb;24(2):188-92. doi: 10.1002/chir.21982. Epub 2011 Dec 16.
Preferential crystallization of amino acid derivatives by seeding a pure enantiomer into racemic amino acid solutions has been studied for many years. However, few examples of valine derivatives have been reported so far. Although there have been some reports using valine hydrogen chloride with preferential crystallization, it is difficult to obtain optical isomers for valine derivatives using preferential crystallization. In this study, repeated preferential crystallization of p-toluenesulfonate valine benzyl ester with a 20% e.e. in 2-propanol gave a 94% e.e. on sonication. Sonication accelerated crystallization rate, but there was not a big difference in e.e. between with and without sonication. However, this research demonstrates the first preferential crystallization of p-toluenesulfonate of valine benzyl esters with an acceleration of crystallization using sonication.
多年来，人们一直在研究通过向外消旋氨基酸溶液中接种纯对映异构体来优先结晶氨基酸衍生物。然而，到目前为止，只有少数缬氨酸衍生物的例子被报道。虽然有一些使用盐酸缬氨酸进行优先结晶的报道，但使用优先结晶很难获得缬氨酸衍生物的光学异构体。在这项研究中，用 2-丙醇对 20%ee 的对甲苯磺酸盐缬氨酸苄酯进行重复优先结晶，超声处理后得到 94%ee。超声处理加速了结晶速率，但有无超声处理的ee 值没有很大差异。然而，这项研究证明了使用超声处理加速结晶，首次实现了对甲苯磺酸盐缬氨酸苄酯的优先结晶。
