We have synthesised two guanosine derivatives that are linked to biotinylated adenosine moieties by using two different strategies, one that includes synthetic steps on the solid phase and another one that is performed entirely in solution. The synthesised derivatives were shown to function as initiator molecules in transcription priming experiments. The incorporation efficiency was determined to be approximately 2%. Even though this value is rather low, the use of either molecule in selection experiments seems reasonable. Basically, RNA libraries with sequence complexities of 10(15) to 10(16) can be generated. Labelling of such a library with our initiator molecule would still produce 10(13) to 10(14) labelled/functionalised sequences, and thus sufficient sequence space for selection.