Inhibitors of phenylethanolamine N-methyltransferase and epinephrine biosynthesis: I. Chloro-substituted 1,2,3,4-tetrahydroisoquinolines

Article abstract of DOI:10.1021/jm00179a007

In a search for inhibitors of epinephrine biosynthesis as potential therapeutic agents, a series of 13 ring-chlorinated 1,2,3,4-tetrahydroisoquinolines was prepared. These compounds were tested initially for their ability to inhibit rabbit adrenal phenylethanolamine N-methyltransferase (PNMT) in vitro. Enzyme-inhibitor dissociation constants, determined for the six most potent members of the series, indicated the following order of decreasing potency: 7,8-Cl₂>6,7,8-Cl₃>7-Cl~8-Cl>5,6,7,8-Cl₄>5,7,8-Cl₃. These compounds were subsequently examined for PNMT-inhibiting activity in intact rats and mice. 7,8-Dichloro-1,2,3,4-tetrahydroisoquinoline (SK&F 64139) was the most potent member of the series both in vitro and in vivo and is currently undergoing clinical investigation.