according to formula iii by appropriate selection of the substituents of the cyclic precursor and of the specific linker and of the specific phosphoramidite moiety according to a specifically desired embodiment of a formula iii protected linker compound for example analogous methods of production for synthesizing amino linker building blocks are also applicable to cyclic imides other than to substituted or non substituted phthalimides variations and combinations of different embodiments are within the scope of the invention the third aspect of the invention relates to the method of coupling protected linker compounds and more specifically to the coupling of protected amino linker phosphoramidite building blocks to a nucleic acid molecule or derivative thereof and furthermore to the deprotection of the protected amino group removing the amino protecting group off the nucleic acid molecule or derivative thereof in an exemplary method of preparing a 5 u2032 amino modified nucleic acid a building block of the exemplary formula ix is coupled to a previously assembled immobilized and protected oligonucleotide containing a free 5 u2032 oh group at the 5 u2032 end followed by oxidation to the corresponding phosphoric acid triester and deprotecting with methylamine or ammonia methylamine mixtures in solution or in the gas phase in fig4 an exemplary method of preparing a 5 u2032 amino modified nucleic acid according to formula xiii by coupling an exemplary protected amino linker phosphoramidite building block of formula ix to a previously assembled immobilized and protected nucleic acid molecule containing a free 5 u2032 oh group at.