[C:1]([O:6][CH3:7])(=O)[C@@H:2](C)O.[H-].[Na+].[C:10]([O:14][CH3:15])(=[O:13])[CH:11]=[CH2:12].S(=O)(=O)(O)[OH:17]>C(OCC)C.CS(C)=O>[CH3:15][O:14][C:10]([CH:11]1[CH2:7][O:6][C@H:1]([CH3:2])[C:12]1=[O:17])=[O:13]
A solution of methyl (R)-(+)-lactate (30 g) in diethyl ether (60 ml) was added dropwise to a stirred mixture of sodium hydride (65%, 10.42 g) and diethyl ether (180 ml) which had been cooled to -35° C. The mixture was allowed to warm to 0° C. and stirred for 20 minutes. The mixture was evaporated. To the residue so obtained there was added a solution of methyl acrylate (29.2 ml) in DMSO (120 ml) which had been cooled to 10° C. The mixture was stirred in an ice-bath for 30 minutes and at ambient temperature for 2 hours. The mixture was poured into cold dilute (5%) aqueous sulphuric acid and extracted with diethyl ether. The organic phase was washed with a cold aqueous sodium bicarbonate solution and with brine, dried (MgSO4) and evaporated. The residue was distilled to give (2R)-4-methoxycarbonyl-2-methyltetrahydrofuran-3-one (16.5 g, 37%), b.p. 66°-68° C. (0.5 mm Hg), [alpha]20 =+55.3° (conc.=1.16 g per 100 ml of chloroform).
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