Synthesis of 2'-deoxy-2',3'-secothymidine t and its dimer t*t, where the two 2'-deoxy-2',3'-secothymidine t units are connected via a carbamate, *=3'-NH-CO-O-5', internucleoside linkage has been achieved. These building blocks were protected in the 5'-position, converted into their phosphoramidites, or attached onto CPG, and then used for ''chimeric oligonucleotide'' synthesis.