5-[N-(2-Aminoethyl)-3-(E)-acrylamido]-5''-O-(dimethoxytrityl)-2''-deoxyuridine can be used as reactant/reagent in preparation of 5- and 6-haptenated 2''-deoxyuridine phosphoramidites for use as mol. diagnostics in immunodetection nucleic acid testing assays.