The reaction of 4-fluorophenylhydrazine, hydrochloride (I) with 4-piperidone hydrochloride hydrate (II) in refluxing ethanol afforded 8-fluoro-2,3,4,5-tetrahydro-1H-pyrido[4,3-b] indole (III) in 82% yield. Compound (III) was reacted with 4-vinylpyridine in THF in the presence of acetic acid to give WY-47,791 free base in 85% yield which was converted to the hydrochloride salt.