Synthetic catalytic oligonucleotide structures

An oligonucleotide structure with a catalytically active center which has a hammerhead structure, having the general structural formula (II):

• ##STR12## wherein x and y can be the same or different and x.gtoreq.1 and y.gtoreq.2,
• N.sub.5 and N.sub.6 are in each case nucleotides which are complementary to one another and * represents a base pairing,
• N' and N" either represent two nucleotide sequences which contain nucleotides which are at least partially complementary to one another so as to enable a stable base pairing between the two nucleotide sequences or
• N' and N" together represent a single nucleotide sequence whereby at least part of the sequence can form a double-stranded stem by base pairing between complementary nucleotides,
• wherein, at least one additional nucleotide N can be inserted after N.sub.7 or/and N.sub.9 ;
• and
• N in each case represents a nucleotide according to the general structural formula (I) ##STR13## in which B represents a nucleoside base which is in particular selected from the group consisting of adenin-9-yl (A), cytosin-1-yl (C), guanin-9-yl (G), uracil-1-yl (U), uracil-5-yl (.psi.), hypoxanthin-9-yl (I), thymin-1-yl (T) and 2-aminoadenin-9-yl,
• N.sub.1 :
• B=A or an A-analogue
• N.sub.2 :
• B=A or an A-analogue
• N.sub.3 :
• B=A or an A-analogue
• N.sub.4 :
• B=G or an G-analogue
• N.sub.7 :
• B=A or an A-analogue
• N.sub.8 :
• B=G or an G-analogue
• N.sub.9 :
• B=U
• N.sub.10 :
• B=A or an A-analogue
• N.sub.11 :
• B=G or an G-analogue
• N.sub.12 :
• B=U
• N.sub.13 :
• B=C
• N.sub.14 :
• B=U
• V in each nucleotide is independently an O or a CH.sub.2 group,
• X and W can in each nucleotide be the same or different and are independently O, S, NH.sub.2, alkyl or alkoxy groups with 1 to 10 carbon atoms, and
• R is hydrogen or a straight-chained or branched alkyl, alkenyl or alkinyl group with 1 to 10 carbon atoms which is unsubstituted or substituted with halogen, cyano, isocyano, nitro, amino, carboxyl, hydroxyl or/and mercapto groups,
• wherein in at least one of the nucleotides the residue R in formula (I) is different from hydrogen.