3-Hydroxybenzidine, a metabolite of benzidine

Previously, it was reported and generally held that 3,3′-dihydroxybenzidine is the principal metabolite of benzidine. The present investigation has disclosed that following intraperitoneal injection of benzidine, the urine of dogs contains 3-hydroxybenzidine in a conjugated form and unchanged benzidine. The metabolite was isolated and identified by comparison with an authentic synthetic preparation of 3-hydroxybenzidine. A convenient synthesis of 3-hydroxybenzidine was also developed.