[CH3:1][C:2]1([CH3:12])[O:6][C@@H:5]([CH2:7][CH2:8][OH:9])[C:4]([CH3:11])([CH3:10])[O:3]1.C(N(CC)CC)C.[CH3:20][S:21](Cl)(=[O:23])=[O:22].O>ClCCl>[CH3:1][C:2]1([CH3:12])[O:6][C@@H:5]([CH2:7][CH2:8][O:9][S:21]([CH3:20])(=[O:23])=[O:22])[C:4]([CH3:11])([CH3:10])[O:3]1Step G To a solution of 2-((S)-2,2,5,5-tetramethyl-[1,3]dioxolan-4-yl)-ethanol (2.7 g, 15.8 mol) and triethylamine (4.6 g, 45 mmol) in dichloromethane (100 mL) at 0° C. was added methanesulfonyl chloride (2.7 g, 24 mmol) dropwise. The reaction mixture was stirred at 0° C. for 1.5 h, then water was added. The organic layer was separated, washed with water, brine, dried over MgSO4, concentrated to give methanesulfonic acid 2-((S)-2,2,5,5-tetramethyl-[1,3]dioxolan-4-yl)-ethyl ester as a yellow oil (2.5 g, 62%).
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