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 o
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/TOFMS.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’-
2
H3] kynurenine-d3,
while the tetra-deuterium-substituted product was L-[β, β, 3’, 5’-
2
H4] 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.