The mechanism by which the ribosome catalyzes peptide bond formation remains controversial. Here we describe the synthesis of a nucleoside that can be used in Brønsted experiments to assess the transition state of ribosome catalyzed peptide bond formation. This substrate is the nucleoside 3'-amino-3'-deoxy-3'-[(3''R)-3-fluoro-l-phenyl-alanyl]-N(6),N(6)-dimethyladenosine, which was prepared from (1R,2R)-2-amino-1-phenylpropane-1,3-diol. This substrate is active in peptide bond formation on the ribosome and is a useful probe for Brønsted analysis experiments on the ribosome.