at phosphorus and subsequently was attacked by a carbamate anion formed from CO2 and a secondary amine. It was found that rear attack of nucleophilic substitution with stereoinversion at pentacoordinate phosphorus was the preferred route, although front attack happened for sterically hindered reactants. The configuration of the CO2 insertion product depended mainly upon the original phosphorus configuration
研究了五配位氢螺膦与胺的Atherton-Todd型反应,并开发了在温和条件下将新的CO 2插入五配位P-N键的反应。通过碳13标记实验,31 P NMR示踪实验和X射线衍射分析,提出了氢螺膦与仲胺之间CO 2插入反应的机理和立体化学。首先在磷上立体保留构型,然后生成氯代螺正膦中间体,然后被CO 2形成的氨基甲酸酯阴离子攻击。和仲胺。已经发现,尽管在位阻反应物上发生了前向攻击,但在五配位磷上进行了具有立体倒置的亲核取代的后向攻击是优选的途径。CO 2插入产物的构型主要取决于氢螺膦的原始磷构型。
A Simple and Economical Method for the Production of <sup>13</sup>C,<sup>18</sup>O-Labeled Fmoc-Amino Acids with High Levels of Enrichment: Applications to Isotope-Edited IR Studies of Proteins
作者:James Marecek、BenBen Song、Scott Brewer、Jenifer Belyea、R. Brian Dyer、Daniel P. Raleigh
DOI:10.1021/ol701913p
日期:2007.11.1
Isotope-edited IR of proteins has generated considerable interest. Double labeling with C-13 and O-18 with high levels of isotopic enrichment is required for residue-specific resolution. Current methods for the preparation of doubly labeled amino acids give modest O-18 enrichment, limiting the utility of the approach. We report a simple and economical method for preparing C-13,O-18-doubly labeled N-(9-fluorenylmethoxycarbonyl)-amino acids with high levels of enrichment for residues that do not require acid-labile side-chain protecting groups.
Expeditious, Potentially Primordial, Aminoacylation of Nucleotides
作者:Jean-Philippe Biron、Alastair L. Parkes、Robert Pascal、John D. Sutherland
DOI:10.1002/anie.200501591
日期:2005.10.21
Late-stage deuteration of<sup>13</sup>C-enriched substrates for<i>T</i><sub>1</sub>prolongation in hyperpolarized<sup>13</sup>C MRI
作者:Céline Taglang、David E. Korenchan、Cornelius von Morze、Justin Yu、Chloé Najac、Sinan Wang、Joseph E. Blecha、Sukumar Subramaniam、Robert Bok、Henry F. VanBrocklin、Daniel B. Vigneron、Sabrina M. Ronen、Renuka Sriram、John Kurhanewicz、David M. Wilson、Robert R. Flavell
DOI:10.1039/c8cc02246a
日期:——
Deuteration on13C-enriched substrates led to increases inT1, yielding improvements in imaging parameters.