Application 5′-Amino-5′-deoxythymidine may be used as a substrate in the synthesis of amide-conjugated nucleosides and their analogues. 5′-Amino-5′-deoxythymidine may be used for DNA 5′-terminal site-specific modification. 5′-Amino-5′-deoxythymidine is used to produce modified thymidine dimer oligonucleotide building units (squaryl groups) to create new oligonucleotide analogues.