The chemical synthesis of the RP and SP diastereomers of thymidyl(3′-5′)thymidyl 0,0-phosphorothioate

The synthesis and separation of diastereomere of protected thymidyl(3′–5′)thymidyl 0,0-phosphoranilidate ($\text{4}$) allowed to obtain in the stereospecific manner title compounds $\text{5}$, whose absolute configuration at P atom was assigned enzymatically. T_P(S)T diastereomers ($\text{5}$) were obtained independently via “phosphite” procedure.