Abstract
Background: After the hydrolysis of daptomycin in deuterated hydrochloric acid, the deuterium-substituted kynurenine was found, but the structure of deuterium-substituted kynurenine has not been reported.
Introduction: The deuterium-substituted kynurenines were simply synthesized and confirmed to be tri- and tetra-substituted products by high resolution mass spectrum and NMR. In further, the deuterium-substituted kynurenines were used to determine the conformation of kynurenine to be L-type in daptomycin through conformation analysis combined with derivation and high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (HPLCQ/ TOF-MS).
Methods: In the present study, a simple synthesis method was developed for deuteriumsubstituted kynurenine, and its structure was confirmed by high resolution mass spectrometry and NMR. L-kynurenine was mixed with the deuterated hydrochloric acid and heated at 110 °C for 7 h. The hydrogen/deuterium exchange products of L-kynurenine were obtained through the hydrogen/deuterium exchange method. After the derivation of deuterium-substituted L-kynurenine by Marfey’s reagent, the conformation of kynurenine in daptomycin was deduced by HPLC-Q/TOF-MS.
Results: The deuterium-substituted kynurenines were confirmed to be tri- and tetra-substituted products by high resolution mass spectrum. Further, Hydrogen NMR spectrum indicated that the deuterium-substitution positions were β-position on amino acid and 3’ and 5’ positions on the benzene ring. Thus, the tri-deuterium-substituted product was L-[β, 3’, 5’-2H3] kynurenine-d3, while the tetra-deuterium-substituted product was L-[β, β, 3’, 5’-2H4] kynurenine-d4. Furthermore, the deuterium-substituted kynurenines were used to determine the conformation of kynurenine to be L-type in daptomycin through conformation analysis combined with derivation and HPLC-Q/TOF-MS.
Conclusion: The synthesis, structures, and application of tri- or tetra- deuterium-substituted kynurenine were reported in this study.
Keywords: L-[β, 3’, 5’- 2 H3] kynurenine-d3, L-[β, β, 5’- 2 H4] Kynurenine-d4, H/D exchange, NMR, HPLC-Q/TOF-MS, Daptomycin
Graphical Abstract
[http://dx.doi.org/10.1021/acs.analchem.5b01934] [PMID: 26020678]
[http://dx.doi.org/10.1038/s41589-018-0128-y] [PMID: 30224694]
[http://dx.doi.org/10.1021/ac0708893] [PMID: 17822305]
[http://dx.doi.org/10.1073/pnas.55.3.453] [PMID: 5221231]
[http://dx.doi.org/10.1021/jo01350a058] [PMID: 5978078]
[http://dx.doi.org/10.1016/0005-2795(76)90014-3] [PMID: 990287]
[http://dx.doi.org/10.1021/acscatal.0c01885]
[http://dx.doi.org/10.1002/ejoc.201300405]
[http://dx.doi.org/10.1126/science.aaf9794] [PMID: 28751584]
[http://dx.doi.org/10.1007/s10337-020-03882-3]
[http://dx.doi.org/10.1016/j.ijms.2020.116499]
[http://dx.doi.org/10.1021/acs.analchem.8b00676] [PMID: 29871488]
[http://dx.doi.org/10.1016/j.chroma.2018.05.062] [PMID: 29859685]
[http://dx.doi.org/10.1016/j.jchromb.2011.05.058] [PMID: 21737363]
[http://dx.doi.org/10.1016/0021-9673(95)00352-N] [PMID: 7633594]