[Synthesis]
((2R,3R)-3-(Benzoyloxy)-4,4-difluoro-5-hydroxytetrahydrofuran-2-yl)methyl benzoate (4.14 g, 10.9 mmol) was dissolved in anhydrous dichloromethane (52 mL), anhydrous triethylamine (2.4 mL) was added and the solution was cooled to 0 °C. Methylsulfonyl chloride (1.23 mL, 15.8 mmol) was added slowly and dropwise with stirring. The reaction mixture was stirred at room temperature for 18 hours. Upon completion of the reaction, the mixture was transferred to a partition funnel and partitioned with methylene chloride (140 mL) and saturated sodium bicarbonate solution (56 mL). The organic phase was separated, dried over anhydrous sodium sulfate, and concentrated under reduced pressure to give an oily product as a mixture of isoheads (5.03 g, quantitative yield). The chemical shifts were analyzed by 19F NMR (CDCl3, 471 MHz) and were δ -107.770, -108.22, -120.65, -121.17, -122.21, -122.73, -123.76, -124.45.1H NMR (CDCl3, 500 MHz) data of the main isocaprolite (60%): δ 8.13-8.04 (m, 4H, benzoyl), 7.65-7.54 (m, 2H, benzoyl), 7.50-7.41 (m, 4H, benzoyl), 6.17 (d, J=5.6 Hz, 1H, H-1), 5.62 (dd, J1=4.2 Hz, J2=16.4 Hz, 1H, H-3), 4.91 (q, J= 3.9 Hz, 1H, H-4), 4.81-4.61 (m, 2H, H-5), 3.17 (s, 3H, CH3). 1H NMR (CDCl3, 500MHz) data of the minor isohead (40%): δ 8.13-8.04 (4H, m, benzoyl), 7.65-7.54 (m, 2H, benzoyl), 7.50-7.41 (m, 4H, benzoyl), 6.09 (d, J=6.4Hz, 1H, H-1), 5.98 (dt, J1 = 7.3 Hz, J2=15.0 Hz, 1H, H-3), 4.81-4.61 (m, 3H, H-4, H-5), 3.03 (s, 3H, CH3).13C NMR (CDCl3, 126 MHz) data: δ 40.09, 40.20 (CH3), 62.52, 63.08 (C-5), 69.61 (dd ), 71.04 (dd, J1C-F=15.7 Hz, J2C-F=26.0 Hz, C-3), 79.68, 79.75, 82.59 (C-4), 98.81 (dd, J1C-F=25.0 Hz, J2C-F=41.8 Hz, C-1), 99.52 (dd, J1C-F=25.0 Hz, J2C-F=41.8 Hz, C-1), 99.52 (dd, J1C-F=25.0 Hz, J2C-F=41.8 Hz C-1), 99.52 (dd, J1C-F=24.5Hz, J2C-F=46.3Hz, C-1), 120.61 (dd, J1C-F=253.5Hz, J2C-F=269.8Hz, C-2), 120.91 (dd, J1C-F=249.3Hz, J2C-F=276.3Hz, C-2) , 128.42, 128.58, 128.63, 128.70, 128.76, 128.79 (benzene ring), 129.18, 129.25 ('ipso' benzene ring), 129.76, 130.07, 130.14, 133.51, 133.63, 134.19, 134.26 (benzene ring), 164.89 , 165.03, 165.81, 165.90 (carbonyl). |