Reaktionsschritte
Diodobenzene diacetate (2.44 g, 7.58 mmol, 1.78 Equiv.) and 2,2,6,6-tetramethylpiperidine nitroxyl (TEMPO) (133 mg, 0.85 mmol, 0.2 Equiv.) were added to a stirred solution of 25 (2.49 g, 4.26 mmol; 1.0 Equiv.) in dry DCM (40 mL). The mixture was stirred at room temperature for 18 h and the reaction mixture was diluted with DAM (50 mL). The organic phase was washed with said sodium bisulphite (2×25 mL), brine (40 mL), dried (MgSO4) and concentrated in vacuo. Purification by flash chromatography (EtOAc/Petroleum ether 6:4) afforded 26 as a white glass. (2.26 g, 91%): [α]D22=+95.0° (c=0.795, CHCl3); 1H NMR (CDCl3, 500 MHz) δ 0.22, 0.23 (two s, 6H, Si(CH3)2), 0.86 (s, 9H, C(CH3)3), 2.56 (dd, 1H, J=3.12, 19.60, H1b), 2.96 (dd, 1H, J=10.29, 18.9, H1a), 3.90 (s, 3H, CH3O8), 3.95-3.99 (m, 5H, H3b, H11a and CH3O7), 4.21 (d, 1H, J=12.02 Hz, Cl3CCH2), 4.32 (d, 1H, J=20.93 Hz, H3a), 5.24 (d, 1H, J=12.03 Hz, Cl3CCH2), 5.83 (d, 1H, J=9.26 Hz, H11), 6.77 (s, 1H, H9), 7.25 (s, 1H, H6); 13C NMR (CDCl3, 125 MHz) δ 207.8 (C2), 168.0 (C5), 153.7 (OC═ONH), 151.4 (C8), 149.2 (C7), 128.0 (C9-10), 124.5 (C5-6), 113.0 (C9), 110.4 (C6), 95.1 (Cl3C), 87.4 (C11), 74.8 (Cl3CCH2), 58.9 (C11a), 56.2 (CH3O7), 56.0 (CH3O8), 52.8 (C3), 40.3 (C1), 25.5 (C(CH3)3), 17.8 (Cquat), −4.2 and −5.3 (Si(CH3)2); IR (film) 2934, 1763 (C═O), 1720 (OC═ON), 1649 (NC═O), 1604, 1515, 1402, 1274, 1217, 1120, 1075, 1002, 866, 834, 756, 712 cm−1; MS (EI) m/z (relative intensity) 615 ([M+MeOH]+., 100).
