[Oligonucleotide analogues containing internucleotide C3'-CH2-C(O)-NH-C5' bonds]

A dinucleoside bearing an amide internucleotide C3'-CH2-C(O)-NH-C5' bond was synthesized by the interaction of 3'-deoxy-3'-carboxylmethylribothymidine-2',3'-lactone obtained by hydrolysis of 2'-O-acetyl-5'-O-benzoyl-3'-deoxy-3'-ethoxycarboxylmethylribothymidine with 5'-deoxy-5'-amino-3'-O-(tert-butyldimethylsilyl)thymidine. After standard manipulations with protective groups, the dinucleoside was converted into 3'-O-(2-cyanoethyl-N,N'-diisopropylphosphoroamidite), which was used for the synthesis of modified oligonucleotides on an automatic synthesizer. Duplex melting curves formed by modified and complementary natural oligonucleotides were measured and the melting temperatures and thermodynamic parameters of duplex formation were calculated. The introduction of one modified bond into oligonucleotides caused only an insignificant decrease in the duplex melting temperatures compared with the nonmodified ones.