Polyamide based nucleic acid analogs — synthesis of δ-amino acids with nucleic acid bases bearing side chains

Nucleoamino acids of type I – III have been synthesized, which can serve as building blocks for novel polyamide based nucleic acid analogs. Key steps in the syntheses are the alkylation of serinol 1 and homoserinol 18 with tert-butyl bromoacetate or tert-butyl bromopropionate under phase transfer conditions and the introduction of thymine or uracil into the amino acid side chains by way of a Mitsunobu reaction. Cytosine derivatives were prepared through uracil → cytosine base conversion at the stage of Nδ-BOC protected amino acid tert-butyl esters.