Stereochemistry of cycloaddition of (S)-N-(1-phenylethyl)-C-diethoxyphosphorylated nitrone with vinyl acetate. Studies on mutarotation of 3-(O,O-diethylphosphoryl)-5-hydroxyisoxazolidines
作者:Dorota G. Piotrowska
DOI:10.1016/j.tetasy.2008.01.009
日期:2008.2
Three enantiomerically pure diethyl 5-acetoxy-2-[(S)-1-phenylethyl]isoxazolidinyl-3-phosphonates were obtained by 1,3-dipolar cycloaddition of the title nitrone and vinyl acetate. Each of them was subsequently transformed into the respective 5-hydroxy derivatives, which exist as equilibrium mixtures of C5-anomers. Detailed mutarotation studies on a 3-(O,O-diethylphosphoryl)-5-hydroxyisoxazolidine system
通过标题腈和乙酸乙烯酯的1,3-偶极环加成反应得到三种对映体纯的5-乙酰氧基-2-[((S)-1-苯基乙基)异恶唑啉基-3-膦酸二乙酯]。随后将它们各自转化成各自的5-羟基衍生物,它们以C5-端基异构体的平衡混合物形式存在。上的3-详细变旋研究(ø,ö -diethylphosphoryl)-5- hydroxyisoxazolidine系统显示,反式-异构体(3小号,5 - [R )在固体状态下是有利的,而在后氯仿48小时d溶液它epimerises在C5为(3 S,5 S)-和(3 S,5 R)-异构体。主要的(3 S,5 S)异构体采用单个E 3构象,并通过C3-P(O)⋯HO-C5氢键稳定。基于使用1 H,13 C和31 P NMR数据进行的构象分析,确定了环加合物的绝对构型,并通过将(3 S,5 R)-异构体转化为已知的(S)-(+)-磷酸高丝氨酸来确认。