Abstract: Two trideoxynucleotides incorporated with 3'-(S)- (thymin-1-yl)-4'-(R) -hydroxy-5' -(S)-hydroxymethyl tetrahydrofuran in the 3' end (3) or in center (4) were synthesized via phos-photriester method in solution.Compounds 3 and 4 are stable towards Nuclease S1 compared withthe normal trideoxynucleotides (2).

Key words: Trideoxynucleotide, 3 '-(S)-(thymin^-1-yl)-4'-(R)-hydroxy-5' -(S)-hydro-xymethyltetrahydrofuran, Oligonucleotide, Enzymatic stability