C(=[C:4]([CH:6]([CH2:8][OH:9])[OH:7])[OH:5])(C)C.[Cl:10][C:11]([O:13]C(Cl)(Cl)Cl)=O.CN(C)[C:20]1[CH:25]=CC=C[CH:21]=1.Cl>C1(C)C=CC=CC=1>[Cl:10][C:11]([O:9][CH2:8][CH:6]1[CH2:4][O:5][C:20]([CH3:25])([CH3:21])[O:7]1)=[O:13]To a mixture comprising 6.6 g (0.05 mol) of isopropylideneglycerol, 5.9 g (0.03 mol) of trichloromethyl chloroformate and 50 ml of toluene was slowly added dropwise 7.3 g (0.06 mol) of N,N-dimethylaniline dissolved in 20 ml of toluene. After stirring at room temperature for 4 hours, the reaction mixture was poured into diluted hydrochloric acid, extracted with ethyl acetate, washed with water, and dried over magnesium sulfate. After distilling off the solvent, 10.4 g of 2,2-dimethyl-1,3-dioxolan-4-ylmethyl chloroformate was obtained as a colorless liquid. This product showed a single spot in thin layer chromatography (silica gel, benzene: ethyl acetate=10:3) and was satisfactory in NMR data [(60 MHz, CDCl3) α; 1.25, 1.30 (s×2, 6H), 3.1-3.7 (m, 4H), 3.8-4.1 (m, 2H), 3.6 (s, 1H, disappeared by adding D2O)]. Thus it was not purified but directly used in the subsequent step.
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