Figure 3.

The reaction of 25 mm oxazolone 1 with 5 mm 5’‐AMP in the presence of 5 mm DIEA in DMF for 3 days at room temperature. HPLC profile (bottom) of a sample of the reaction mixture (20 μL) diluted in 1 mL of 100 mm MES buffer pH 6.5 (method A, detection 248 nm). The identity of peaks 5 and 5’ with those observed in the experiment described in Figure 2 was demonstrated by co‐injection (top).