Figure 2. Synthesis of chloroalkane tag.

The first step is a nucleophilic acyl substitution with ditertbutyl-dicarbonate to protect the free amine of 2-(2-aminoethoxy)-ethanol with Boc protecting group, to obtain compound 1. The second step is an SN2 reaction under basic conditions to obtain compound 2. Then the Boc group is deprotected under acidic conditions to yield the free amine, compound 3. Compound 3 can be used for conjugation to a molecule or interest, or it can be reacted with succinic anhydride under basic conditions to yield ct-COOH, or it can be reacted with a dibenzocyclootyne-succinimidyl ester to yield ct-DBCO, or it can be reacted with a tetramethylrhodamine succinimidyl ester to yield ct-TMR (not shown).