(a), (b) Examples of spectra obtained with Effelsberg between 4 and 8 GHz toward Sgr B2(N) resulting from averaging both polarizations. In each panel, the vertical dashed line marks a velocity of 64 km s⁻¹. The red curve shows the baseline fitted with a 5th-order polynomial function. The boxes at the bottom show the windows avoided to perform the baseline fit. The average continuum level used to compute the synthetic spectrum is indicated in the top left corner. (c), (d) Synthetic spectra (orange) used to derive the upper limit to the column density of glycolamide, overlaid on observed spectra after baseline subtraction (black). The rms noise level is indicated in the top left corner. The horizontal dotted lines show the 4σ and −4σ levels. The components of each hyperfine multiplet are labeled and marked with vertical dotted lines. The velocity axis shown at the top was computed relative to the strongest component of each hyperfine multiplet.