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A solution of furanone (13) (1.2 g, 5.88 mmols) and benzophenone (108 mg, 0.588 mmols) in [1,3]-dioxolane (108 mg) was degassed for 40 min in a stream of argon. The mixture then was irradiated using one 450 watt ACE glass medium pressure mercury lamp, from a distance of 15 cm, for 9 hours. Progress of this reaction was observed via 1H-NMR. As the reaction mixture was degassed, and throughout all of the irradiation time, the reaction flask was held in a water cooled cooling mantel. The temperature of the cooling water was constantly maintained near 0° C. Upon completion of the reaction, solvent was removed under reduced pressure, followed by column chromatography on silica gel (35% EtOAc in hexanes as the eluent), yielding the title compound (1.34 g, 82%) as a clear oil, Rf=0.14 (30% EtOAc in hexanes), [α]25D 16.5° (c 1.2, CHCl3); 1H-NMR (500 MHz, CDCl3) δ: 2.50 (dd, 1H, J=3.9, 12.9 Hz), 2.70-2.79 (m, 2H), 3.58 (dd, 1H, J=3.5, 7.2 Hz), 3.75 (dd, 1H, J=2.8, 7.9 Hz), 3.87-3.92 (m, 2H), 3.97-4.00 (m, 2H), 4.51 (d, 1H, J=11.9 Hz), 4.57-4.61 (m, 2H), 4.88 (d, 1H, J=3.6 Hz), 7.26-7.36 (m, 5H); 13C-NMR (125.8 MHz, CDCl3) δ: 30.39, 40.53, 65.77, 71.74, 73.99, 79.52, 104.14, 128.00, 128.89, 138.07, 176.79.

1. customThe mixture then was irradiated
2. customAs the reaction mixture was degassed
3. temperaturecooled
4. temperaturecooling mantel
5. customUpon completion of the reaction, solvent
6. customwas removed under reduced pressure