1 , 1 - diurea , 2 - carbobenzoxy - 8 - fluoro - 5 -- 2 , 3 , 4 , 5 - tetrahydro - 1h - pyridoindole , an efficient process for converting the former to the latter , further comprising conversion of the latter to 8 - fluoro - 5 -- 2 -- 4 - hydroxybutyl )-] 2 , 3 , 4 , 5 - tetrahydro - 1h - pyridoindole or to 8 - fluoro - 5 -- 2 , 3 , 4 , 5 - tetrahydro - 1h - pyridoindole .