Reliable assignment of absolute configuration of chiral amines based on the analysis of 1H NMR spectra of their CFTA amide diastereomers
摘要:
Applications of the CFTA method, a new and reliable procedure for the determination of the absolute configuration of chiral primary amines, are described in detail. In addition to the very high reactivity of CFTA chloride, the stable anti-periplanar conformers of CFTA amides, associated with the chiral structure of fluorine atom on a stereogenic center, are the key factors that make the technique of using H-1 NMR analysis of the CFTA diastereomers very reliable. In particular, this method is useful for the determination of the absolute stereochemistry of isotopically multi-labeled amino acid derivatives. (C) 2008 Elsevier Ltd. All rights reserved.
质谱仪上的Reaktionen vonGlutaminsäure二甲酸酯。21.药理学原理Verhalten von Stickstoffverbindungen † ‡
摘要:
谷氨酸二甲酯(1)及其氘代衍生物1a,1b和1c的质谱裂解已得到研究。通过从分子离子中损失甲氧基羰基,产生了m / e 116的离子。后者分离出甲醇(m *),得到的m / e 84片段增加了光谱的基峰。如前所述[2] [3],转移到离去基团的氢只有一部分来自氨基。基于氘代化合物的实验,我们提出了另一种反应机理,即氢从C(3)转移到甲氧基。通过这两个过程生成的碎片很可能是吡咯烷鎓离子。质谱仪中的热副反应(焦谷氨酸酯的形成)继而发生碎裂可能导致相同的离子。-讨论了N-乙酰基谷氨酸二酯的质谱碎片被支持的机制3,图3a,图3b和3D的N,N-二甲基衍生物的和4和4a中。–研究的断裂反应类似于某些1,3-三亚甲基二胺衍生物[7]。这意味着,无论官能团的性质如何,双官能化合物的质谱碎裂都存在相似之处。
The one-pot syntheses of N-protected Δ1- and Δ2-dehydrodipeptide esters by the coupling of N-carboxy α-dehydroamino acid anhydride (ΔNCA) with several kinds of C- or N-protected L-α-amino acids are described. In addition, it was found that a similar coupling of ΔNCA with both C- and N-protected α-amino acids also took place to give Δ2-dehydrotripeptide derivatives, involving eight kinds of important