Chelated Enolates of Amino Acid Esters − New and Efficient Nucleophiles for Isomerization-Free, Stereoselective Palladium-Catalyzed Allylic Substitutions
Chelated amino acid ester enolates were found to be suitable nucleophiles for palladium-catalyzed allylic alkylations. Unlike stabilized soft nucleophiles, the chelatedenolates react under very mild reaction conditions, even at −78 °C. If TFA-protected amino acid tert-butyl esters are used as nucleophiles, the anti-configured products are obtained in a highly diastereoselective fashion. This protocol
发现螯合氨基酸酯烯醇化物是钯催化烯丙基烷基化的合适亲核试剂。与稳定的软亲核试剂不同,螯合的烯醇化物在非常温和的反应条件下反应,甚至在 -78 °C 下也是如此。如果使用 TFA 保护的氨基酸叔丁酯作为亲核试剂,则会以高度非对映选择性的方式获得反构型产物。因此,该协议是螯合烯醇克莱森重排的一个很好的补充,它产生了相应的 syn 产品。使用烯丙基碳酸酯作为底物可获得特别好的结果,因为它们很容易在低至 -78 °C 的温度下形成所需的 π-烯丙基钯配合物。在这个温度范围内,π-烯丙基中间体的 π−σ−π 异构化不发挥重要作用,因此,高反应性螯合烯醇化物的应用允许在 (Z)-烯丙基底物的烯丙基烷基化中使用 C-亲核试剂,首次完全保持烯烃的几何形状。由于 (Z)-烯丙基碳酸酯在烯丙基末端带有两个相同的取代基,亲核试剂对中间体 π-烯丙基钯配合物的攻击仅发生在反位,产生 (E)-构型的取代产物。如果使
Synthesis of protected α-amino acids <i>via</i> decarboxylation amination from malonate derivatives
作者:Hui Fu、Peihe Li、Zheng Wang、Xiaoying Li、Qipu Dai、Changwen Hu
DOI:10.1039/d0ob00677g
日期:——
A general and efficient strategy for the synthesis of protected α-aminoacids is reported. The method uses malonate derivatives as the starting materials and Cs2CO3 as a base at 60 degrees, giving α-aminoacidderivatives in moderate yields by releasing CO2. This methodology shows broad substrate scope (primary and secondary acids), excellent functional group tolerance and high efficiency to give the
报道了一种合成保护的α-氨基酸的通用有效策略。该方法以丙二酸酯衍生物为起始原料,以Cs 2 CO 3为碱在60度下,通过释放CO 2,以中等收率得到α-氨基酸衍生物。该方法学显示了广泛的底物范围(伯酸和仲酸),出色的官能团耐受性和高效率,可在温和的反应条件下提供所需的产物。它还允许构建β和γ-氨基酸以及其他非天然产物。
Complementary to the Claisen rearrangement, the title reaction-which when carried out with chelatedenolates of amino acid esters as nucleophiles gives rise to unsaturated amino acids-preferentially provides anti instead of syn products. This palladium-catalyzed reaction proceeds under very mild conditions and is suitable for the synthesis of enantiomerically pure amino acids (see reaction scheme)
An object of the present invention is to provide methods of discovering drugs effective for tough targets, which have conventionally been discovered only with difficulty. The present invention relates to novel methods for cyclizing peptide compounds, and novel peptide compounds and libraries comprising the same, to achieve the above object.