Synthesis of novel pipecolic acid derivatives. Part 2. Addition of trimethylsilyl cyanide to 3,4,5,6-tetrahydropyridines
作者:Ole Westerhoff、Arne Lützen、Wolfgang Maison、Marc Kosten、Jürgen Martens
DOI:10.1039/b009112j
日期:——
The synthesis of alkyl- and aryl-substituted derivatives of pipecolic acid (piperidine-2-carboxylic acid) by a modified Strecker protocol is described. Addition of trimethylsilyl cyanide (TMSCN) to various tetrahydropyridines 1 and subsequent hydrolysis of the obtained α-amino nitriles 2 yielded pipecolic acid derivatives 3. Addition of TMSCN to cyclic imines 1 proceeded rapidly and led to α-amino nitriles in excellent yields without any necessary further purification. Almost quantitative diastereoselectivity for the formation of 2,6-trans-substituted amino nitrile 2g was observed at low temperature, when chiral imine 1g was used as reactant. Acidic hydrolysis of α-amino nitriles 2 yielded the corresponding amino acids 3 in good to excellent yields. Furthermore, an efficient protocol for the optical resolution of N-formylated derivatives of pipecolic acid by separation of diastereomeric norephedrinium salts is described.
描述了一种通过改进的斯特雷克合成法合成烷基-和芳基取代的哌啶-2-羧酸(皮啶酸)衍生物。将三甲基硅基氰化物(TMSCN)添加到各种四氢吡啶1中,经过水解得到的α-氨基腈2生成了哌啶酸衍生物3。TMSCN与环状亚胺1的反应迅速进行,生成了α-氨基腈,产率极佳,无需进一步净化。在低温下,当使用手性亚胺1g作为反应物时,观察到2,6-反式取代的氨基腈2g的绝对立体选择性几乎是定量的。α-氨基腈2的酸性水解得到相应的氨基酸3,产率良好到优秀。此外,还描述了一种有效的光学分辨法,用于通过分离二醇异构体盐来分离N-甲酰化的哌啶酸衍生物。