Fig. 3.
Bar graphs illustrating the role of the lactone intermediate on the NH3 amidation and MeNH2 amidation step in EtOH (a) or DMSO (b) using an α2,3-sialyllactitol standard. Native reaction conditions refer to the application of either EE or DMA reagent in the first step of the reaction and the addition of NH4OH or MeNH2 in the second step. The direct conditions mimic the NH3 amidation or MeNH2 amidation step by the immediate addition of NH4OH or MeNH2 in the first step. The control conditions refer to the use of control-reagents without EDC and HOBt following the two-step reaction. The average and SDs for triplicate measurements are shown as stacked bars and error bars, respectively. The pH of the conditions was evaluated in triplicate using narrow range pH indicator strips (Supplementary Table 1)