reacting 6-chloronicotinates with the corresponding amine building block. The Boc-protected N-heterocycles piperazine 23, isonipecotic acid 26 and 3-azetidinecarboxylic acid 27 were used as starting materials to synthesise amine building blocks for the amino linker (Scheme 1). Bocprotected piperazine 23 reacted with 4-fluorobenzyl isocyanate to amide 24 in 53% yield, followed by Boc-deprotection with HCl in dioxane to give the free amine in 68% yield.