[CH3:1][C:2]1([CH3:12])[O:6][C@H:5]([CH2:7][C:8]([OH:10])=O)[C:4](=[O:11])[O:3]1.[CH2:13]([SH:15])[CH3:14].C1CCC(N=C=NC2CCCCC2)CC1.C(O)(=O)C>C(Cl)Cl.CN(C)C1C=CN=CC=1.CCOCC>[CH3:12][C:2]1([CH3:1])[O:6][C@H:5]([CH2:7][C:8](=[O:10])[S:15][CH2:13][CH3:14])[C:4](=[O:11])[O:3]1(R)-2-(2,2-Dimethyl-5-oxo-1,3-dioxolan-4-yl)acetic acid (25 g, 144 mmol) was dissolved in CH2Cl2 (500 mL) and cooled in an ice bath. Ethanethiol (21.2 mL, 287 mmol) and N,N-dimethylpyridin-4-amine (0.351 g, 2.87 mmol) were added followed by DCC (35.5 g, 172 mmol). This mixture was stirred in ice bath for 1 hour, and then 2 hours at ambient temperature. Acetic acid (45 mL) was added and then stirred the mixture for 10 minutes. The reaction mixture was then poured into vigorously stirred ether (400 mL) and filtered. The filtrate was washed with 10% sodium carbonate, water, 0.5 N HCl, water and brine. The organic layer was dried over Na2SO4, filtered and concentrated. The residue was purified over silica gel (1-5-10% EtOAc in hexanes) to afford (R)—S-ethyl 2-(2,2-dimethyl-5-oxo-1,3-dioxolan-4-yl)ethanethioate (22.5 g, 103 mmol, 71.8% yield) as a clear colorless oil that solidified to a white solid.
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