[Oligonucleotides and their analogs. II. Spectra of the circular dichroism of dinucleoside phosphate analogs containing 4-thiouracil].

The dinucleoside phosphates analogues APpSU, SUPpA and UPpSU have been synthesised by direct thionation of DNP analogues, containing cytosine. The structure of compounds prepared was proved by UV- and PMR-spectra. The CD spectra of the DNP analogues were examined. It has been demonstrated that the "induced" dichroism contribution in the Cotton-effect of DNP was substantial in the case of stacking conformations and negligible for unstacking conformations.