Purity of crude 2-acetylnoviosamine 1 was determined in three independent quantitative 1 H-NMR analyses with 1,3,5-trimethoxybenzene (Sigma-Aldrich, ≥99%) as internal standard. The measurements were conducted on a 500 MHz spectrometer in CD3OD. Inversion recovery experiments were carried out (figure ) to estimate the T1 times of the resonances at 4.92 ppm (d, J = 6.9 Hz, 1H, C4H, compound 1) and 6.09 ppm (s, 3H, CH arom., 1,3,5trimethoxybenzene). 1 H-NMR measurements were then conducted with a relaxation delay of 47.2 s (7 times longest T1 (τ / ln2) minus the acquisition time (3.3 s)) so that more than 99.9% of the spin magnetization is relaxed. The weight of internal standard and compound 1 for each measurement is summarized in table . The integrals and their absolute values used for purity calculation are depicted in figure to figure S9. Reasonable integration borders were estimated and set by hand and do not include C satellites. The results of the purity determination are summarized in table .