the latter is less active than the endogeneous catecholamines , ( r ) -norepinephrine and ( r ) -epinephrine , but the stereospecific competition for [ 3h ] prazosin binding sites by the catecholamine isomers with the beta r configuration is additional evidence that ( alpha s ) -erythro-alpha-methylepinephrine may be a biologically active metabolite of l-alpha-methyl-3,4-dihydroxyphenylalanine .
C0028351
norepinephrine
C0014563
epinephrine