Selected data for 4c: 1H NMR (250 MHz, CS2-CDCl3) 1.7 (s, 9H, But); 13C NMR (62.5 MHz, CDCl3) 154.4 (C=O), 144.9 (4C), 144.8 (4C), 144.5 (4C), 144.3 (2C),144.2 (4C), 143.7 (4C), 143.4 (2C), 142.8 (8C),142.7 (8C), 142.5 (2C), 141.9 (4C), 141.8 (4C), 140.7 (4C), 139.6 (4C), 83.3 (quat. C), 80.9 (2C), 27.6 (But); FTIR max 2960 (m, CH), 1738 (s, C=O), 526 (fullerene) cm-1; UV-VIS (DCM) 257.5 ( = 1.38x105), 324 ( = 3.47x104), 410 ( = 3.30x103), 421 ( = 2.66x103) nm.