§Selected data for O-4-nitrophenylsulfonyl-2,4,6-tri-tert-butylphenylhydroxamic acid 9a: EI-MS (M+) 506.20771 C25H34N2O7S requires 506.20867; mp 190°C (decomp.); 1H NMR (250 MHz, CDCl3) 1.15 (s, 18H, o-But), 1.25 (s, 9H, p-But), 8.28 (AB quartet, 4H, -SO2C6H4-NO2), 8.59 (bs, 1H, NH); 13C NMR (62.5 MHz, CDCl3) 154.1 (C=O), 152.9, 151.2, 148.2, 144.2, 141.1, 138.8, 131.2, 124.0, 123.6, 35.4, 34.7, 31.3; FTIR max 3277 (s, NH), 1792 (s, C=O), 1527, 1394 (s, NO2), 1350, 1192 (s, SO2) cm-1.