Organic & Biomolecular Chemistry
Paper
= 9.2 Hz, 1H), 3.85 (s, 3H), 3.83 (s, 6H), 3.77 (s, 3H), 3.46–3.38 13C NMR (100 MHz, CDCl3): δ = 148.8, 148.7, 147.13, 147.10,
(m, 2H), 3.16 (q, J = 6.8 Hz, 1H), 2.19 (br, 1H, –OH), 2.07 (q, J = 137.6, 137.1, 119.6, 119.5, 111.2, 111.1, 111.03, 110.98, 66.9,
6.8 Hz, 1H), 1.10 (s, 9H), 0.80 (d, J = 6.8 Hz, 3H), 0.76 (d, J = 55.8 (3C), 55.7 (2C), 36.0, 35.9, 11.8, 9.6 ppm; HRMS (ESI):
6.8 Hz, 3H) ppm; 13C NMR (100 MHz, CDCl3): δ = 148.5 (2C), calcd for C22H30O5Na+ [M + Na]+: 397.1985, found: 397.1979.
147.3 (2C), 140.7, 139.6, 135.6 (2C), 135.5 (2C), 133.7, 133.6,
129.7, 129.6, 127.7 (2C), 127.6 (2C), 118.1, 117.5, 110.6, 110.5,
(Alternative procedure for kadangustin J)
(3R*,4R*)-2,2-Bis(3,4-dimethoxyphenyl)-3,4-dimethyl tetra-
109.4, 109.3, 81.7, 67.9, 55.8 (4C), 38.5, 34.7, 26.9 (3C), 19.3, hydrofuran (17). To a stirred solution of the above tertiary
12.3, 8.5 ppm; HRMS (ESI): calcd for C38H48O6SiNa+ [M + Na]+: alcohol 16 (28 mg, 0.072 mmol) in CH2Cl2 (2 mL) was added
651.3112, found: 651.3101.
Et3SiH (0.06 mL, 0.36 mmol, 5.0 equiv.) at 0 °C followed by the
((2R*,3S*)-4,4-Bis(3,4-dimethoxyphenyl)-2,3-dimethyl butoxy)- addition of BF3·Et2O (0.02 mL, 0.144 mmol, 2.0 equiv.) drop-
(tert-butyl)diphenylsilane (20). To a stirred solution of the wise. After 2 min, the reaction was quenched by saturated
above tertiary alcohol 19 (5.8 g, 9.24 mmol) in CH2Cl2 (70 mL) aqueous Na2CO3 (1 mL) and extracted with CH2Cl2 (20 mL).
was added Et3SiH (7.4 mL, 46.2 mmol, 5.0 equiv.) at 0 °C fol- The organic layers were washed with water (3 × 5 mL) and
lowed by the addition of BF3·Et2O (2.3 mL, 18.5 mmol, brine (5 mL), then dried over Na2SO4, filtered and concen-
2.0 equiv.) dropwise. After 20 min, the reaction was quenched trated under reduced pressure. The resulting crude residue
by saturated aqueous Na2SO3 (10 mL) and extracted with was purified by flash column chromatography (petroleum
CH2Cl2 (200 mL). The organic layers were washed with water ether–EtOAc = 1 : 1) on silica gel to afford the undesired tetra-
(3 × 30 mL) and brine (50 mL), then dried over Na2SO4, filtered hydrofuran 17 (26 mg, 98% yield) as a colorless oil. Rf = 0.60
and concentrated under reduced pressure. The resulting crude (petroleum ether–EtOAc = 1 : 1); IR (film): νmax = 2998, 2958,
O-silyl ether 20 (5.6 g) as a colorless oil could be used directly 2932, 2871, 2835, 1604, 1590, 1511, 1463, 1409, 1327, 1258,
1
without further purification. The small amount of this sample 1240, 1168, 1141, 1029, 913, 859, 803, 763, 732, 647 cm−1; H
was isolated for characterization. Rf = 0.53 (petroleum ether– NMR (400 MHz, CDCl3): δ = 7.02 (dd, J = 2.0, 8.4 Hz, 1H), 6.91
EtOAc = 1 : 1); IR (film): νmax = 3066, 2957, 2930, 2857, 1590, (d, J = 2.0 Hz, 1H), 6.84 (d, J = 8.4 Hz, 1H), 6.75 (d, J = 2.0 Hz,
1513, 1463, 1262, 1143, 1111, 1078, 1029, 817, 742, 704 cm−1
;
1H), 6.73 (d, J = 8.4 Hz, 1H), 6.62 (dd, J = 2.0, 8.4 Hz, 1H), 4.31
1H NMR (400 MHz, CDCl3): δ = 7.64 (t, J = 8.0 Hz, 4H), 7.41 (q, (t, J = 8.0 Hz, 1H), 3.89 (s, 3H), 3.84 (s, 3H), 3.81 (s, 3H), 3.80
J = 7.2 Hz, 2H), 7.35 (t, J = 7.2 Hz, 4H), 6.91 (d, J = 8.4 Hz, 1H), (s, 3H), 3.46 (dd, J = 8.4, 10.8 Hz, 1H), 2.41 (qd, J = 2.8,
6.85 (d, J = 9.2 Hz, 1H), 6.84 (s, 2H), 6.80 (d, J = 9.2 Hz, 1H), 10.8 Hz, 1H), 2.07–1.95 (m, 1H), 1.01 (d, J = 6.4 Hz, 3H), 0.86
6.78 (d, J = 7.6 Hz, 1H), 3.86 (s, 3H), 3.84 (s, 3H), 3.83 (s, 3H), (d, J = 6.8 Hz, 3H) ppm; 13C NMR (100 MHz, CDCl3): δ = 148.7,
3.78 (s, 3H), 3.54 (d, J = 11.6 Hz, 1H), 3.48 (d, J = 7.6 Hz, 2H), 148.0, 147.8, 147.5, 139.8, 137.7, 119.8, 118.4, 110.9 (2C),
2.88–2.81 (m, 1H), 1.93 (q, J = 7.2 Hz, 1H), 1.09 (s, 9H), 0.66 (d, 109.93, 109.87, 90.3, 73.8, 55.83 (2C), 55.76 (2C), 49.4, 40.6,
J = 7.2 Hz, 3H), 0.63 (d, J = 6.8 Hz, 3H) ppm; 13C NMR 15.6, 14.5 ppm; ESI-MS: m/z 373.3 [M + H]+; HRMS (ESI): calcd
(100 MHz, CDCl3): δ = 148.9, 148.8, 147.2, 147.1, 138.1, 137.3, for C22H29O5+ [M + H]+: 373.2010, found: 373.2007.
135.6 (2C), 135.5 (2C), 134.0, 133.8, 129.6, 129.5, 127.60 (2C),
4,4-Bis(3,4-dimethoxyphenyl)-2,3-dimethylbut-3-en-1-ol (18).
127.57 (2C), 119.7 (2C), 111.22 (2C), 111.18, 110.9, 67.1, 55.9, To a stirred solution of the above diol 16 (200 mg, 0.51 mmol)
55.8 (2C), 55.7 (2C), 35.4, 35.3, 26.9 (3C), 19.4, 11.6, 9.3 ppm; in EtOH (10 mL) was added conc. HCl (0.8 mL) dropwise at
HRMS (ESI): calcd for C38H48O5SiNa+ [M + Na]+: 635.3163, reflux. After 3 h, the reaction mixture was cooled to room
found: 635.3155.
temperature and diluted with CH2Cl2 (60 mL). The organic
( )-Kadangustin J (1). To a stirred solution of the above layers were washed with saturated aqueous Na2CO3 (10 mL),
O-silyl ether 20 (5.6 g, 9.15 mmol) in THF (60 mL) was added water (3 × 10 mL) and brine (10 mL), then dried over Na2SO4,
n-Bu4NF (11.9 g, 45.7 mmol, 5.0 equiv.) portionwise at 30 °C. filtered and concentrated under reduced pressure. The result-
After 16 h, the reaction mixture was diluted with CH2Cl2 ing crude residue was purified by flash column chromato-
(300 mL) and poured into a separatory funnel. The organic graphy (petroleum ether–EtOAc = 1 : 1) on silica gel to afford
layers were washed with water (3 × 50 mL) and brine (50 mL), 3-butene-1-ol 18 (120 mg, 63% yield) as a colorless oil. Rf =
then dried over Na2SO4, filtered and concentrated under 0.20 (petroleum ether–EtOAc = 1 : 1); IR (film): νmax = 3523,
reduced pressure. The resulting crude ( )-kadangustin J (1) 3000, 2958, 2935, 2871, 2835, 1601, 1581, 1511, 1464, 1408,
(3.38 g) as a colorless oil could be used directly without further 1316, 1251, 1167, 1184, 1138, 1029, 913, 863, 802, 760,
1
purification. The small amount of this sample was isolated for 733 cm−1; H NMR (400 MHz, CDCl3): δ = 6.80 (d, J = 7.6 Hz,
characterization. Rf = 0.28 (petroleum ether–EtOAc = 1 : 1); IR 2H), 6.71 (dd, J = 3.2, 8.0 Hz, 2H), 6.70 (s, 1H), 6.64 (s, 1H),
(film): νmax = 3513, 2960, 2935, 2835, 1591, 1514, 1464, 1417, 3.86 (s, 6H), 3.82 (s, 3H), 3.81 (s, 3H), 3.62 (t, J = 10.0 Hz, 1H),
1380, 1263, 1144, 1028, 912, 732 cm−1 1H NMR (400 MHz, 3.50 (dd, J = 6.4, 10.8 Hz, 1H), 2.93 (sext, J = 6.8 Hz, 1H), 1.71
;
CDCl3): δ = 6.88 (dd, J = 1.6, 8.0 Hz, 1H), 6.86 (dd, J = 1.6, (s, 3H), 1.34 (br, 1H, –OH), 1.03 (d, J = 7.2 Hz, 3H) ppm;
8.0 Hz, 1H), 6.84 (d, J = 1.6 Hz, 1H), 6.81 (d, J = 1.6 Hz, 1H), 13C NMR (100 MHz, CDCl3): δ = 148.4, 148.3, 147.44, 147.38,
6.78 (d, J = 8.0 Hz, 1H), 6.77 (d, J = 8.0 Hz, 1H), 3.87 (s, 3H), 139.9, 135.9, 135.7, 134.8, 121.9, 121.5, 112.8, 112.7, 110.8,
3.86 (s, 3H), 3.82 (s, 6H), 3.54 (d, J = 12.0 Hz, 1H), 3.50–3.43 110.6, 66.0, 55.81 (2C), 55.75 (2C), 39.7, 15.5, 14.0 ppm;
(m, 2H), 2.66–2.58 (m, 1H), 1.82–1.72 (m, 1H), 1.39 (br, 1H, ESI-MS: m/z 373.4 [M + H]+; HRMS (ESI): calcd for C22H29O5
+
–OH), 0.76 (d, J = 7.2 Hz, 3H), 0.69 (d, J = 6.8 Hz, 3H) ppm; [M + H]+: 373.2010, found: 373.2004.
This journal is © The Royal Society of Chemistry 2013
Org. Biomol. Chem., 2013, 11, 7574–7586 | 7581