(BA 0358) has been reported in the literature as a useful tool for the preparation of uridylated amino acid. Such modified amino acids have then been incorporated into nucleopeptides such as the uridylated viral genome-linked peptide found in the terminal protein of then poliovirus. In addition, this phosphoramidite can be used in the formation of nucleoside diphosphate sugars which are valuable tools in glycobiology. Nucleopeptides from poliovirus and coxsackie virus contain tyrosine residues modified with two uridine nucleotide units.