title: Synthesis and in vitro reactivity of 3-carbamoyl-2-phenylpropionaldehyde and 2-phenylpropenal: putative reactive metabolites of felbamate.
abstract: We propose that 3-carbamoyl-2-phenylpropionaldehyde is an intermediate in the metabolism of felbamate, an anti-epileptic drug with a unique profile of the therapeutic activity, and undergoes a cascade of chemical reactions responsible for the toxic properties of the parent drug. To test this hypothesis, we have synthesized 3-carbamoyl-2-phenylpropionaldehyde and evaluated its in vitro reactivity. This molecule was found to be highly unstable at physiological pH (t1/2 < or = 30 s) and to undergo facile elimination to 2-phenylpropenal, an alpha, beta-unsaturated aldehyde commonly termed atropaldehyde. However, the predominant reaction pathway for 3-carbamoyl-2-phenylpropionaldehyde was reversible cyclization to generate 4-hydroxy-5-phenyltetrahydro-1,3-oxazin-2-one, a urethane that has a considerably longer half-life at physiological pH (t1/2 > or = 5 h) and may serve as a stable reservoir of the reactive aldehyde both in vitro and in vivo. Atropaldehyde is a potent electrophile and was found to exhibit cytotoxicity to cultured fibroblasts (50% growth inhibition (GI50) = 4.1 +/- 1.1 microM) comparable to the known unsaturated aldehyde toxins, 4-hydroxy-2-nonenal and acrolein. 3-Carbamoyl-2-phenylpropionaldehyde also exhibited significant cytotoxicity (GI50 = 53 +/- 8 microM), whereas 2-phenyl-1,3-propanediol monocarbamate (GI50 > 500 microM) and 3-carbamoyl-2-phenylpropionic acid (GI50 > 500 microM) were nontoxic. We have additionally demonstrated the formation of a glutathione-atropaldehyde conjugate from the in vitro incubation of 3-carbamoyl-2-phenylpropionaldehyde with glutathione. Thus, the potent cytotoxicity and potential allergenicity of atropaldehyde implicate this unsaturated aldehyde as a possible causative agent in the toxicities observed with felbamate treatment.
authors.affiliation: Chemistry Department, University of Virginia, Charlottesville 22901, USA.
authors.forename: C D
authors.initials: CD
authors.lastname: Thompson
authors.forename: M T
authors.initials: MT
authors.lastname: Kinter
authors.forename: T L
authors.initials: TL
authors.lastname: Macdonald
mesh_terms: D000447:Aldehydes / Q000138:chemical synthesis / Q000737:chemistry* / Q000633:toxicity; D000818:Animals; D000927:Anticonvulsants / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D006224:Cricetinae; D000078328:Felbamate; D005347:Fibroblasts / Q000187:drug effects; D006168:Guinea Pigs; D006207:Half-Life; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D048448:Phenylcarbamates; D011409:Propylene Glycols / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity
chemical_list: C104537:3-carbamoyl-2-phenylpropionaldehyde; D000447:Aldehydes; D000927:Anticonvulsants; D048448:Phenylcarbamates; D011409:Propylene Glycols; C013026:hydratropic aldehyde; D000078328:Felbamate