The invention relates to a compound of general formula (I): where X=0 or 1, Z=O, S or CH2, R1 and R2 independently=OH or OY, where Y=a protecting group, OR3, where R3=a monosaccharide or disaccharide group, A1-CH2—N+(CH3)3, X′, where X=halogen, A1=an amide (NHC(O)) or ester (OC(C)) bond, OPO(OM)2, where M=an alkyli or alkyli earth metal, OP(O)O−—O(CH2)2—N+(CH3)3, A2-(PEGX1-A3)n-R4, where n=0 or 1, PEGX1=a polyethyleneglycol of molecular weight X1, where X1 being less than or equal to 5,000 daltons, A2 and A3 independently=a ether (O), ester (OC(O)), amide (NHC(O)), urea (NHC(O)NH), thiourea (NHC(S)NH), or thioether (S) bond R4=a directing agent.