Simultaneous measurement of metabolic stability and metabolite identification of 7-methoxymethylthiazolo[3,2-a]pyrimidin-5-one derivatives in human liver microsomes using liquid chromatography/ion-trap mass spectrometry.
A liquid chromatography/mass spectrometry (LC/MS) method using an atmospheric pressure chemical ionisation source was used to measure the metabolic stability and metabolite identification of 7-methoxymethylthiazolo[3,2-a]pyrimidin-5-one derivative (1) in human liver microsomes. After 15 min incubation with human liver microsomes, compound 1 exhibited metabolic turnover of 44%. Data-dependent tandem mass spectrometry (MS/MS) scanning was used to generate product ion spectra from the protonated ions of the compound and its metabolites. An unusual metabolite at m/z 407 corresponding to the [M-24+H]+ ion was identified for compound 1. Interestingly, the formation of the [M-24+H]+ ion was not observed in the analogues wherein the fused thieno double bond was substituted (2) and the thieno group replaced by a fused benzo derivative (3). Compounds 2 and 3 exhibited metabolic turnovers of 24 and 30%, yielding oxidative metabolites corresponding to [M+16] and [M+32]+, respectively. Based on these facts the mechanism for [M-24]+ formation in compound 1 through an initial epoxide formation on the double bond of the fused thieno ring followed by hydrolytic ring opening and deacylation is envisaged.
Kantharaj
E
E
In Vitro Pharmacokinetics, Department of ADME/Tox, Johnson & Johnson Pharmaceutical Research and Development, A Division of Janssen Pharmaceutica, Beerse, Belgium. kethiraj@prdbe.jnj.com
Ehmer
Peter B
PB
Tuytelaars
An
A
Van Vlaslaer
Anne
A
Mackie
Claire
C
Gilissen
Ron A H J
RA
D014150:Antipsychotic Agents / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D008862:Microsomes, Liver / Q000378:metabolism*; D011744:Pyrimidinones / Q000032:analysis / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013844:Thiazoles / Q000032:analysis / Q000378:metabolism*
C501558:7-methoxymethylthiazolo(3,2-a)pyrimidin-5-one; D014150:Antipsychotic Agents; D011744:Pyrimidinones; D013844:Thiazoles