The present invention relates to a compound represented by formula (I) wherein X is selected from the group of formulae (II) to (IV) wherein R 1 is H or C 1 -C 50 chain which may be branched or linear and which may be saturated or unsaturated and which may optionally be interrupted and/or substituted by one or more hetero atom(s) (Het1) and/or functional group(s)(G1)； or R 1 is a C 3 -C 28 moiety which comprises at least one cyclic structure and which may be saturated or unsaturated and which may optionally be interrupted and/or substituted by one or more hetero atom(s) (Het1) and functional group(s)(G1)； R 2 is H； or R 2 is a Mono-phosphate, Di-phosphate, Tri-phosphate or phosphoramidite moiety； or R 2 is -Y-X or -Y-L-Y 1 - X； Y and Y 1 are independently from each other a single bond or a functional connecting moiety, X is a colloid-active compound (CA) or a fluorescence marker (FA) or a polynucleotide moiety having up to 50 nucleotide residues, preferably 10 to 25 nucleotides, especially a polynucleotide having an antisense or antigen effect； L is a linker by means of which Y and X are covalently linked together； R 3 and R 4 represent independently from each other a C 1 -C 28 -alkyl moiety which may optionally be substituted or interrupted by one or more heteroatom(s) and/or functional group(s)；or R 3 and R 4 form a ring having at least 5 members, preferably a ring having 5 to 8 carbon atoms and wherein the ring may be substituted or interrupted by one or more hetero atom(s) and/or functional group(s)； or R 3 and R 4 represent independently from each other a C 1 -C 28 -alkyl moiety substituted with one or more moieties selected from the group -Y-X or -Y-L-Y 1 -X； or R 3 and R 4 represent independently from each other -Y-X or -Y-L-Y 1 - X； R 5 and R 6 represent independently from each other a C 1 -C 28 -alkyl moiety which may optionally be substituted or interrupted by one or more heteroatom(s) and/or functi
