Amezinium metilsulfate (, sold under the brand name Regulton, is a sympathomimetic drug which is widely used in the treatment of orthostatic hypotension in Japan.
Amezinium metilsulfate has a unique mechanism of action of acting as a dual monoamine oxidase inhibitor (MAOI) and norepinephrine reuptake inhibitor (NRI).
This drug is made from 2-butyne-1,4-diol starting material with as an intermediate.
The halogenation of 2-butyne-1,4-diol (1) with chlorine gives mucochloric acid (2). Treatment with phenylhydrazine (3) gives 1-phenyl-4,5-dichloro-6-pyridazone (4). Addition of ammonia leads to chloridazon (5). Catalytic hydrogenation yields 5-amino-2-phenylpyridazin-3-one (6). Alkylation with dimethyl sulfate completes the synthesis of amezinium metisulfate (7).