Synthesis of 4-thia-[6-13C]lysine from [2-13C]glycine: access to site-directed isotopomers of 2-aminoethanol, 2-bromoethylamine and 4-thialysine
作者:Amarendra Nath Maity、Ajam C. Shaikh、Sankareswaran Srimurugan、Chi-Ju Wu、Chinpiao Chen、Shyue-Chu Ke
DOI:10.1007/s00726-010-0808-8
日期:2012.1
alternative substrate for lysine in enzymatic reactions. Site-directed isotopomers are often needed for elucidation of mechanism of reactions. 4-Thialysine can be synthesized by reacting cysteine with 2-bromoethylamine, an important reagent in chemical-modification rescue (CMR) of proteins. Here, we present the synthesis of 4-thia-[6-13C]lysine, one of the isotopomers of 4-thialysine, from commercially
for nuclei farther from the iron ion. As a result, it is also the dominant mechanism for the relaxation of the porphyrin protons. The π spin distribution on the porphyrin ring has been derived from the dipolar contribution to the linewidth for the carbon nuclei. Furthermore, the experimental β proton resonance linewidth can be interpreted only by considering a normalized iron spin density lower than unity
高同位素氯(5,10,15,20-四苯基卟啉铁)(III)的13 C nmr光谱已使用在选定位置同位素富集的卟啉明确分配。卟啉核碳共振的意外线宽由碳核与配体不成对的π电子自旋密度的偶极相互作用解释。这种相互作用是介观弛豫的主要机制碳和吡咯β碳。对于远离铁离子的原子核,此机制的相对贡献增加。结果,它也是卟啉质子弛豫的主要机理。卟啉环上的π自旋分布是由偶极对碳核线宽的贡献得出的。此外,仅考虑低于1的归一化铁自旋密度,才能解释实验性β质子共振线宽。提出3.5 / 5的值与早期的分子轨道计算非常吻合。该分析提供了一组自洽的数据,用于定量描述对观察到的位移的各种贡献,包括以配体为中心的伪接触贡献以及对质子和碳核的线宽。
Highly Enantioselective Ruthenium/PNNP-Catalyzed Imine Aziridination: Evidence of Carbene Transfer from a Diazoester Complex
asymmetric aziridination. Aziridine yields were overall moderate to low (up to 33% isolated yield of the cis isomer) because of the competitive formation of diethyl maleate (7). The scope of the catalyst was studied with p- and m-substituted imines. NMR spectroscopic studies with 13C- and 15N-labeled EDA indicate that aziridine 6a is formed by carbenetransferfrom an EDA complex, [RuCl(EDA)(PNNP)]PF6