1: [131I]-Uracil With N,O-bis-(trimethylsilyl)-acetamide in acetonitrile T=20°C; 0.5 h; 2: 2,3,5-tri-O-acetyl-D-ribofuranosyl 1-(N-phenyl)-2,2,2-trifluoroacetimidate With trimethylsilyl trifluoromethanesulfonate in 1,2-dichloro-ethane T=20°C; Further stages.;