3'-desoxipentopiranosil-nucleic acid and preparation

Links 3'-desoxipentopiranosil-nucleosides of formula (I), wherein R1 is equal to OH, Hal Hal equal to Br or Cl, a radical chosen from i-Pr equal to isopropyl, or -O-PH - (> = O) (- O '), R2, R3 and R4 independently of one another, identical or different, are each H, NR5R6, OR7, SR8,> = O, CnH2n + 1 being an integer n 1-12, preferably 1-8, in particular 1-4, a leaving group in the beta position of formula -OCH2CH2R18 with R18 equal to cyano or a radical p-nitrophenyl radical or fluorenylmethyloxycarbonyl (Fmoc), or (CnH2n) NR10R11, with R10R11 = H, CnH2n + 1 or R10R11 linked via a radical of the formula wherein R12, R13, R14 and R15 independently of one another, identical or different, are each H, OR7, or CnH2n + 1 or CnH2n-1, n having the meaning given above, and wherein R5, R6, R7 and R8 independently of one another, identical or different, are each H, CnH2n + 1 or CnH2n-1 , n having the signif ied above, - (CO) R9 R9 equal to a linear or branched alkyl radical, optionally substituted, aryl, phenyl preferably.