The present invention relates to novel nucleoside derivatives of general formula (I) ##STR00001## wherein R.sup.1=H, halogen, NO.sub.2, CN, OCH.sub.3, an alkyl, alkoxy or alkoxyalkyl residue having 1 to 4 C atoms, preferably a methyl, ethyl, propyl or butyl residue or an optionally substituted aryl residue or aliphatic acyl residue having 2 to 5 atoms, R.sup.2 to R.sup.7=H, NO.sub.2, CN, OCH.sub.3, a branched or unbranched alkyl, alkoxy or alkoxyalkyl residue having 1 to 5 C atoms or an optionally substituted aryl residue or an aliphatic acyl residue having 2 to 5 atoms, X is the group C.dbd.O or C.dbd.S, Y.dbd.S, O, NR', C(R').sub.2, wherein R' is H, or a branched or unbranched alkyl residue having 1 to 5 C atoms or an optionally substituted aryl residue, Z=SO.sub.2, OCO, OCS, SCS, and N is a nucleotide.