NUCLEOSIDE PIRO-4.4-PENTAMETHYLENE-1.3.2-OXATHIAPHOSPHOLANE)S - MONOMERS FOR STEREOCONTROLLED SYNTHESIS OF OLIGO(NUCLEOSIDE PHOSPHOROTHIOATE PHOSPHATE)S/

Attempts at synthesis of ''chimeric'' oligonucleotide constructs (PO/P S-Oligos) possessing phosphate and P-stereodefined phosphorothioate in ternucleotide linkages via combined phosphoramidite/oxathiaphospholane methods were unsuccessful. Therefore, novel monomers for oxathiaphosp holane method, namely 5'-O-DMT-deoxyribonucleoside iro-4.4-pentamethyl ene-1.3.2-oxathiaphospholane)s, were prepared and used together with t heir diastereomerically pure 2-thio analogues for the stereocontrolled synthesis off ''chimeric'' oligonucleotide constructs (PO/PS-Oligos).