Identification of the principal circulating metabolite of a synthetic 5,4'-diaminoflavone (NSC 686288), an antitumor agent, in the rat.
During the course of our study to develop analytical methodology for quantitating the investigative antitumor agent 5-amino-2-(4-amino-3-fluorophenyl)-6,8-difluoro-7-methyl-4H-1-benzopyran -4-one (DAF; NSC 686288) in plasma, a significant concentration of a metabolite was observed in a post-dosed rat. The results of electron-ionization (EI) mass spectrometric analysis of the metabolite suggested that N-acetylation had occurred, but, interestingly, that only one of the compound's two primary amino groups had been transformed. Comparing the mass spectra and gas chromatographic retention times of a mono-acetylated sample of DAF and that of the metabolite showed both to be the same. A retro-Diels-Alder (RDA) fragmentation of the B ring of DAF results in formation of two abundant product ions, each retaining one of the amino groups. The EI mass spectrum of mono-N-acetamido-d3 DAF shows loss of ketene-d2, leading to formation of an -NHD group. The ensuing RDA fragmentation easily identifies which of the two product ions contains the deuterium, thereby allowing us to assign the site of N-acetylation as the amino group on ring C (the 4' position) of DAF.
Phillips
L R
LR
Laboratory of Drug Discovery, Research and Development, Developmental Therapeutics Program, Division of Cancer Treatment, Diagnosis and Centers, National Cancer Institute, Frederick, MD 21701, USA. 1p5q@nih.gov
Bramhall
C
C
Buckley
J
J
Wolfe
T
T
House
T L
TL
Stinson
S F
SF
D000107:Acetylation; D000818:Animals; D000970:Antineoplastic Agents / Q000097:blood* / Q000737:chemistry; D003903:Deuterium; D005419:Flavonoids / Q000097:blood* / Q000737:chemistry; D013058:Mass Spectrometry; D015394:Molecular Structure; D051381:Rats
D000970:Antineoplastic Agents; D005419:Flavonoids; C413760:aminoflavone; D003903:Deuterium