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.
Multicomponent synthesis of tripeptides containing pipecolic acid derivatives: selective induction of cis- and trans-imide bonds into peptide backbones
A simple approach to several tripeptides consisting of two terminal glycine fragments and a central pipecolic acid derivative was found via a multicomponent reaction starting from tetrahydropyridines. The protected peptides 2a–g were formed in high yields and with different substitution patterns of the central heterocyclic amino acid. In cases where chiral imines were used the target compounds were obtained with remarkable diastereoselectivity. The influence of different substituents attached to the pipecolic acid fragment on N-terminal amide isomerism was investigated using X-ray crystallography and NMR spectroscopic methods.
通过以四氢吡啶为起点的多组分反应,我们找到了一种简单的方法来制备由两个末端甘氨酸片段和一个中心哌啶醇酸衍生物组成的多种三肽。受保护的肽 2a-g 产量很高,而且中心杂环氨基酸的取代模式各不相同。在使用手性亚胺的情况下,获得的目标化合物具有显著的非对映选择性。利用 X 射线晶体学和核磁共振光谱法研究了连接在哌啶醇酸片段上的不同取代基对 N 端酰胺异构体的影响。
Boranes Paving the Way to Anionic Cyclic (Alkyl)(amino)carbenes (Ani‐cAACs)
作者:Ludwig Zapf、Sven Peters、Udo Radius、Maik Finze
DOI:10.1002/anie.202300056
日期:——
First examples of anionic cAACs (Ani-cAACs) bearing B(CN)3 or C2F5BF2 as N-substituents are reported and their stereo-electronic parameters have been evaluated. These anionic carbenes can replace anionic substituents as exemplified by the formation of selenium adducts and [Ani-cAAC-Au-PPh3].
报道了带有 B(CN) 3或 C 2 F 5 BF 2作为N-取代基的阴离子 cAAC (Ani-cAAC) 的第一个例子,并评估了它们的立体电子参数。这些阴离子卡宾可以取代阴离子取代基,例如形成硒加合物和 [Ani-cAAC-Au-PPh 3 ]。
Synthesis of novel pipecolic acid derivatives: a multicomponent approach from 3,4,5,6-tetrahydropyridines
A simple approach to several derivatives of pipecolic acid is via a multicomponent reaction starting from cyclic imines 2, which are synthesized on a large scale and with different substitution patterns. The protected amino acids 3 are formed in high yields. In cases where chiral imines are used the target compounds are obtained with remarkable diastereoselectivity. Bisamides 3 serve as versatile precursors for the preparation of a wide range of amino acid derivatives. Different methods of hydrolysis of 3 lead to the free pipecolic acids or its derivatives. Employment of methanol or ethanethiol as a nucleophile in the acid-mediated conversion of enamides 3 results in N-acylated amino acid esters 5. Furthermore a method for the resolution of the obtained racemic α-amino acids via diastereomeric salt formation is described.
homopipecolic acid are prepared by α-amino alkylation of malonic acid with cyclic imines 6 and 7. These are prepared on a large scale and with different substitution patterns. The β-aminoacids 8 and 9 were formed in high yield and with remarkable diastereoselectivity if chiral imines are used as starting materials. The diastereoselectivity of the amino alkylation leading to homopipecolic acid analogues