Abstract
The active metabolite of dicloxacillin was isolated from human urine, and its structure was investigated. The 1H-nuclear magnetic resonance (NMR) and 13C-NMR spectra indicated that one proton had been lost from the 5-methyl group of dicloxacillin. Fast atom bombardment mass spectra showed that one oxygen atom had been added to dicloxacillin by the biotransformation. These results confirmed that hydroxylation of the methyl group at the 5-position of the isoxazolyl moiety of dicloxacillin occurs to yield the active metabolite.
