[CH3:1][C:2]1([CH3:19])[O:6][C@@H:5]([CH2:7][C:8]([O:10][Si:11]([C:14]([CH3:17])([CH3:16])[CH3:15])([CH3:13])[CH3:12])=[O:9])[C:4](=[O:18])[O:3]1.[Br:20]N1C(=O)CCC1=O.N(C(C)(C)C#N)=NC(C)(C)C#N>C(Cl)(Cl)(Cl)Cl>[Br:20][C:5]1([CH2:7][C:8]([O:10][Si:11]([C:14]([CH3:17])([CH3:16])[CH3:15])([CH3:13])[CH3:12])=[O:9])[C:4](=[O:18])[O:3][C:2]([CH3:19])([CH3:1])[O:6]1A solution of (S)-(+)-2,2-dimethyl-5-oxo-1,3-dioxolane4-acetic acid, t-butyldimethylsilyl ester (20.9 g, 72.4 mmol) in carbon tetrachloride (200 ml) was treated with N-bromosuccinimide (14.18 g, 79.6 mmol) and 2,2′-azobisisobutyronitrile (0.30 g) and the resulting mixture was heated under reflux while irradiating with a 500 W lamp. After ˜5 minutes, a mild exothermic reaction was observed and the mixture was heated for an additional 5 minutes. The reaction mixture was then cooled in an ice bath and the floating succinimide was filtered and washed with a small amount of carbon tetrachloride. The filtrate was used immediately as such for the next step. 1H NMR (400 MHz, CDCl3) δ: 0.27 (s, 3), 0.28 (s, 3), 0.94 (s, 9), 1.66 (s, 3), 1.84 (s, 3), 3.62 (m, 2).
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