Nucleotides. Part LVII.. Synthesis of phosphoramidite building blocks of 2′-amino-2′-deoxyribonucleosides: New compounds for oligonucleotide synthesis

The chemical synthesis of 2′‐amino‐2′‐deoxyribonucleosides of uracil, cytosine, adenine, and guanine, and their conversion into suitably protected 3′‐phosphoramidite building blocks 35–40 for oligonucleotide synthesis are described. The aglycone and the 2′‐amino functions were protected using the 2‐(4‐nitrophenyl)ethoxycarbonyl (npeoc) group. The synthesis of the 3′‐O‐succinyl (3′‐O‐(3‐carboxypropanoyl))‐substituted starting nucleoside 41 is described and its behavior examined in solution and on solid phase with regard to an anticipated migration during 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) deprotection. Oligonucleotides were prepared using the new building blocks, and their hybridization properties were studied by UV‐melting techniques.