Molecules 2010, 15
5613
(1.28 g, 11.22 mmol, 2.4 eq.). The mixture was kept at 0–5 °C for 24 hours. Upon consumption of the
starting material, the reaction was quenched by addition of Et3N (1.5 mL) and cold H2O (50 mL). The
organic layer was separated and washed with brine (50 mL), dried (Na2SO4), filtered and the solvent
removed in vacuo. The crude product was then purified by silica gel chromatography
(heptane/CH2Cl2/EtOAc, 25/25/1, v/v/v) to afford 27 (1.75 g, 57%), and 28 (440 mg, 14%).
5,7,3’,4’-Tetra-O-benzyl-(+)-thiocatechin (27). []20 D = +55.2 (c 1, CH2Cl2); Chemical purity = 97%
1
(AUC); Optical purity = 96% ee; H-NMR (CDCl3) = 2.0 (d, 1H, J = 5.5 Hz), 2.7 (dd, 1H, J = 8.4,
17.2 Hz), 3.1 (dd, 1H, J = 4.5, 17.2 Hz), 4.1 (d, 1H, J = 8.5 Hz), 4.15-4.3 (m, 1H), 4.95 (s, 4H), 5.1 (s,
2H), 5.12 (s, 2H), 6.4 (s, 2H), 6.85–6.95 (m, 2H), 7.01 (d, 1H, J = 1.5 Hz), 7.2–7.5 (m, 20H);
13C-NMR (CDCl3) = 29.8, 31.9, 51.3, 70.0, 70.2, 70.3, 71.3, 71.4, 77.5, 97.4, 103.3, 113.8, 115.2,
115.4, 121.9, 127.3, 127.5, 127.6, 127,9, 127.9, 127.9, 128.1, 128.5, 128.5, 128.6, 128.6, 130.62,
133.9, 136.8, 136.8, 137.0, 137.2, 148.1, 149.2, 157.1, 158.1; MS (m/z) = 667.5 (M++1). Anal. calcd
for C43H38O5S, C 77.45, H 5.74, S 4.81 Found C 77.36, H 5.59, S 4.62.
5,7,3’,4’-Tetra-O-benzyl-(+)-thioepicatechin (28). []20
= +61.3 (c 1, CH2Cl2); Optical
D
purity = 96.6% ee; Chemical purity = 100% (AUC); 1H-NMR (CDCl3) = 2.2 (d, 1H, J = 9.6 Hz), 2.9
(q, ABq, JA = 3.9, 4.1, 17.4 Hz, JB = 4.9, 5.3 Hz), 4.3–4.42 (m, 2H), 4.95 (s, 2H), 5.12 (s, 2H), 5.14 (s,
2H), 6.3 (s, 2H), 6.82 (d, 1H, J = 8.3 Hz), 6.98 (dd, 1H, J = 2, 8.3 Hz), 7.12 (d, 1H, J = 2 Hz), 7.2–7.5
(m, 20H); 13C-NMR (CDCl3) = 31.4, 31.9, 49.8, 66.4, 70.0, 70.3, 71.3, 71.4, 77.5, 97.7, 102.3, 112.3,
114.9, 115.65, 121.7, 127.2,. 127.3, 127.5, 127.6, 127.8, 127.9, 128.1, 128.5, 128.5, 128.6, 128.6,
131.4, 133.7, 136.8, 136.8, 137.2, 137.3, 148.4, 148.9, 158.1, 158.5; MS (m/z) = 667.5 (M++1). Anal.
calcd for C43H38O5S, C 77.45, H 5.74, S 4.81 Found C 77.28, H 5.63, S 4.66.
5,7,3’,4’-Tetra-O-benzyl-(-)-thiocatechin (31) and 5,7,3’,4’-tetra-O-benzyl-(-)-thioepicatechin (32). To
a cold solution (0–5 °C) of 30 (1.26 g, 1.62 mmol, 1 eq.) in CH2Cl2 (60 mL) was added TFA
(300 L, 3.89 mmol, 2.4 eq.). The mixture was kept at 0–5 °C. Upon consumption of the starting
material, the reaction was quenched by addition of Et3N (515 L) and cold H2O (25 mL). The organic
layer was separated and washed with brine (25 mL), dried (Na2SO4), filtered and the solvent removed
in vacuo. The crude product was then purified by silica gel chromatography (heptane/CH2Cl2/EtOAc,
1/1/0 to 25/25/1, v/v/v) to afford the desired compounds 31 (0.82 g, 76%), and 32 (170 mg, 16%).
5,7,3’,4’-Tetra-O-benzyl-(-)-thiocatechin (31). []20 D= -62.5 (c 1, CH2Cl2); Chemical purity = 98.6%
(AUC); Optical purity = 96% ee; 1H-NMR (CDCl3) = 1.95 (d, 1H, J = 4.4 Hz), 2.7 (dd, 1H, J = 8.4,
17.2 Hz), 3.12 (dd, 1H, J = 4.5, 17.2 Hz), 4.15 (d, 1H, J = 8.5 Hz), 4.18–4.32 (m, 1H), 4.98 (s, 4H), 5.1
(s, 2H), 5.12 (s, 2H), 6.3 (s, 2H), 6.8–6.92 (m, 2H), 7.02 (d, 1H, J = 1.5 Hz), 7.2–7.5 (m, 20H);
13C-NMR (CDCl3) = 29.8, 51.3, 70.0, 70.2, 70.3, 71.3, 71.4, 77.5, 97.4, 102.3, 113.8, 115.4, 121.9,
127.3, 127.5, 127.6, 127.9, 127.9, 127.9, 128.1, 128.2, 128.5, 128.5, 128.6, 128.6, 129.1, 130.6, 133.9,
136.8, 136.9, 137., 137.2, 149.2, 149.2, 157.8, 159.0; MS (m/z) = 667.5 (M++1). Anal. calcd for
C43H38O5S, C 77.45, H 5.74, S 4.81 Found C 77.41, H 5.66, S 4.78.