Enantioselective biotransformation of 1-isopropylnaphthalene in rabbits

1-Isopropylnaphthalene (1) was administered orally to rabbits and the following eight metabolites, 2-(1-naphthyl)-2-propanol (7), 2-(1-naphthyl)-1-propanol (8: R/S = 83:17), 2-(1-naphthyl)-1,2-propanediol (9:R/S = 40:60), 4-isopropyl-1,2-naphthoquinone (10), 4-isopropyl-1-naphthol (11), 4-isopropyl-2-naphthol (12), 5-isopropyl-2-naphthol (13), and 2-(1-naphthyl)propanoic acid (14') as its methyl ester (14: R/S = 52:48), were isolated from urine. Among them, three metabolites (8, 9, and 14), possessing an asymmetric carbon atom in the molecule, were formed enantioselectively and five metabolites (7, 10, 11, 12, and 13) were formed regioselectively. The presumed metabolic pathways of 1-isopropylnaphthalene (1) in rabbits leading to these metabolites are discussed.