在这里,我们报道了3-氨基-1,2,4-恶二嗪(AOXD)支架的非对映选择性合成。环中存在一个N–O键可防止芳族系统的平面几何形状,并导致胍基团的碱性大大降低。尽管DIBAL-H由于表现出高非对映选择性而似乎是最有效的还原剂,但我们观察到Mitsunobu反应对所得β-氨基醇的各种行为,取决于附近的空间位阻,导致构型的转化或保留羟基。理化特性(p K a和log D)并通过实验确定了几种AOXD衍生物的肝稳定性,发现AOXD支架具有开发药物的前景。此外,我们合成了Alchornedine,这是带有AOXD支架的唯一天然产物。在对分析数据进行比较的基础上,我们发现报告的α-角豆碱的结构是不正确的,并假设了一种新的结构。
Eight members of a new family of fullerene derivatives, [60]fulleropyrrolidine-N-oxides, have been synthesized and characterized. Facile oxidation, by a peracid, of the parent [60]fulleropyrrolidine gave clean conversions into the product molecules, in which the tertiary amine is transformed into a quaternary amine bearing an oxygen atom. The reaction is very selective, favoring the nitrogen atom of the pyrrolidine ring in preference to epoxidation of the fullerene cage. The H-1 NMR shows an AB quartet splitting pattern, characteristic of nonequivalent hydrogens in the pyrrolidine ring and at a chemical shift displacement of 0.8 ppm downfield. Other methods of characterization are described, including MS, differential scanning calorimetry, thermogravimetric analysis, HPLC, UV/vis, and IR. Conclusive evidence for the formation of an N-oxide moiety is provided by the synthesis, oxidation, and NMR characterization of a novel [60]fulleropyrrolidine containing a N-15 isotope, showing an 85 ppm downfield heteroatom chemical shift. Preliminary details of the effects of substitution on the reactivity of the pyrrolidine ring are also reported.
Modular Oxime Formation by a <i>trans</i>‐AT Polyketide Synthase
作者:Hannah A. Minas、Romain M. M. François、Franziska Hemmerling、Amy E. Fraley、Cora L. Dieterich、Simon H. Rüdisser、Roy A. Meoded、Sabrina Collin、Kira J. Weissman、Arnaud Gruez、Jörn Piel
DOI:10.1002/anie.202304481
日期:2023.8.21
by a range of organisms, and constitute a family of cytotoxic natural products. Here, we determine how this capped oxime group is installed during assembly of the model polyketide lobatamide by a modular trans-AT polyketidesynthase and provide molecular insight into the responsible mono-oxygenase domain by X-ray crystallography.
promising properties for drug development. Moreover, we synthesized alchornedine, the only natural product with the AOXD scaffold. Based on a comparison of the analytical data, we found that the reported structure of alchornedine was incorrect and hypothesized a new one.
在这里,我们报道了3-氨基-1,2,4-恶二嗪(AOXD)支架的非对映选择性合成。环中存在一个N–O键可防止芳族系统的平面几何形状,并导致胍基团的碱性大大降低。尽管DIBAL-H由于表现出高非对映选择性而似乎是最有效的还原剂,但我们观察到Mitsunobu反应对所得β-氨基醇的各种行为,取决于附近的空间位阻,导致构型的转化或保留羟基。理化特性(p K a和log D)并通过实验确定了几种AOXD衍生物的肝稳定性,发现AOXD支架具有开发药物的前景。此外,我们合成了Alchornedine,这是带有AOXD支架的唯一天然产物。在对分析数据进行比较的基础上,我们发现报告的α-角豆碱的结构是不正确的,并假设了一种新的结构。
Eight members of a new family of fullerene derivatives, [60]fulleropyrrolidine-N-oxides, have been synthesized and characterized. Facile oxidation, by a peracid, of the parent [60]fulleropyrrolidine gave clean conversions into the product molecules, in which the tertiary amine is transformed into a quaternary amine bearing an oxygen atom. The reaction is very selective, favoring the nitrogen atom of the pyrrolidine ring in preference to epoxidation of the fullerene cage. The H-1 NMR shows an AB quartet splitting pattern, characteristic of nonequivalent hydrogens in the pyrrolidine ring and at a chemical shift displacement of 0.8 ppm downfield. Other methods of characterization are described, including MS, differential scanning calorimetry, thermogravimetric analysis, HPLC, UV/vis, and IR. Conclusive evidence for the formation of an N-oxide moiety is provided by the synthesis, oxidation, and NMR characterization of a novel [60]fulleropyrrolidine containing a N-15 isotope, showing an 85 ppm downfield heteroatom chemical shift. Preliminary details of the effects of substitution on the reactivity of the pyrrolidine ring are also reported.