Fig. 7. Gravity-driven column chromatography over silica gel for N-acetylated amines 27,7–9 N-acetyl β-amino acid esters 28,15 and N-acetyl α-amino acid esters 296d,9,11 as well as sulfoxides 306e,17,18 and perfluoroalkyl-containing compounds such as 31–33.4,10 .