131322-68-4Relevant articles and documents
Novel tenofovir mixed ester-amide prodrugs
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Paragraph 0082-0084, (2020/04/17)
The invention relates to novel tenofovir mixed ester-amide prodrugs or pharmaceutically acceptable salts thereof, a preparation method thereof, pharmaceutical compositions containing the prodrug compounds, and application of the prodrugs in preparation of drugs for treating virus infection such as hepatitis B virus (HBV) or human immunodeficiency virus (HIV) infection.
Stable Nitrogen Isotope Analysis of Amino Acid Enantiomers by Gas Chromatography/Combustion/ Isotope Ratio Mass Spectrometry
Macko, Stephen A.,Uhle, Maria E.,Engel, Michael H.,Andrusevich, Vladimir
, p. 926 - 929 (2007/10/03)
The analysis of the stable nitrogen isotope compositions of individual amino acid stereoisomers through the use of gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) is presented. Nitrogen isotopic compositions of single amino acids or of their enantiomers is possible without the labor-intensive and time-consuming preparative-scale chromatographic procedures required for conventional stable isotope analysis. Following hydrolysis and derivatization, single-component isotope analysis is accomplished on nanomole quantities of each of the stereoisomers of an amino acid, utilizing the effluent stream of gas chromatographic separation. Nitrogen isotope fractionation is minimal during acylation of the amino acid, with no additional nitrogen being added stoichiometrically to the derivative. Thus, the isotopic composition of the nitrogen in the derivative is that of the original compound. Replicate stable nitrogen isotope analyses of 11 amino acids, and their trifluoroacetyl (TFA)/isopropyl (IP) ester derivatives, determined by both conventional isotope ratio mass spectrometry (IRMS) and GC/C/IRMS, indicate that the GC procedure is highly reproducible (standard deviations typically 0.3-0.4‰) and that isotopic differences between the amino acid and its TFA/IP derivative are, in general, less than 0.5‰.
Stable carbon isotope analysis of amino acid enantiomers by conventional isotope ratio mass spectrometry and combined gas chromatography/isotope ratio mass spectrometry
Silfer,Engel,Macko,Jumeau
, p. 370 - 374 (2007/10/02)
The application of a combined gas chromatography/isotope ratio mass spectrometry (GC/IRMS) method for stable carbon isotope analysis of amino acid enantiomers is presented. This method eliminates the numerous preparative steps integral to the isolation of amino acids and amino acid enantiomers from protein hydrolyzates that precede δ13C analysis by conventional isotope ratio mass spectrometry. Unlike hydrocarbons, amino acids require derivatization prior to GC/ IRMS analysis. Replicate δ13C analyses of trifluoroacetyl (TFA) isopropyl ester derivatives of 22 amino acids by IRMS revealed that the derivatization process is reproducible, with an average error (1 standard deviation) of 0.10‰ ± 0.09 ‰. The average analytical error for analysis of amino acid derivatives by GC/IRMS was 0.26‰ ± 0.09‰. In general, absolute differences between IRMS and GC/IRMS analyses were less than 0.5‰. The derivatization process introduces a distinct, reproducible isotopic fractionation that is constant for each amino acid type. The observed fractionations preclude direct calculation of underivatized amino acid δ13C values from their respective TFA isopropyl ester δ13C compositions through mass balance relationships. Derivatization of amino acid standards of known stable carbon isotope compositions in conjunction with natural samples, however, permits computation of the original, underivatized amino acid δ13C values through use of an empirical correction for the carbon introduced during the derivatization process.
