The reaction of N-(tert-butoxycarbonyl)-L-4-fluorophenylalanine (I) with 4-hydroxypiperidine (II) by means of triethylamine, EDC and HOBT in dichloromethane gives the expected piperidide (III), which is deprotected with with HCl in dioxane to afford (IV) with a free amino group that is condensed with 5-chloro-1H-indole-2-carboxylic acid (V) by means of triethylamine, EDC and HOBT as before.