PAPER
C8-Prenylation of Flavonols and Flavanones
1313
FT-IR (KBr): 3503, 2918, 2055, 1769, 1683, 1605, 1515, 1436,
1412, 1371, 1325, 1274, 1203, 1127, 1087, 972, 945, 901, 861, 812,
770, 723 cm–1.
1H NMR (400 MHz, CDCl3): δ = 7.26 (dd, J = 8.4, 2.0 Hz, 1 H),
7.13 (d, J = 2.0 Hz, 1 H), 7.00 (d, J = 8.4 Hz, 1 H), 6.52 (s, 1 H),
5.42 (dd, J = 13.2, 2.8 Hz, 1 H), 5.08–5.04 (m, 1 H), 3.86 (s, 3 H),
3.24 (d, J = 7.2 Hz, 2 H), 3.00 (dd, J = 16.4, 13.2 Hz, 1 H), 2.77 (dd,
J = 16.4, 2.8 Hz, 1 H), 2.37 (s, 3 H), 2.33 (s, 3 H), 2.31 (s, 3 H), 1.66
(d, J = 0.4 Hz, 3 H), 1.58 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 189.6 (C), 169.4 (C), 168.7 (C),
168.2 (C), 153.9 (C), 151.4 (C), 148.5 (C), 139.8 (C), 132.6 (C),
130.9 (C), 124.7 (CH), 121.3 (C), 120.9 (CH), 120.7 (CH), 112.4
(CH), 111.8 (C), 111.1 (CH), 78.7 (CH), 56.0 (CH3), 44.8 (CH2),
25.6 (CH3), 23.2 (CH2), 21.0 (CH3), 20.9 (CH3), 20.6 (CH3), 17.8
(CH3).
6.36 (s, 1 H), 5.33–5.37 (m, 1 H), 3.94 (s, 3 H), 3.59 (br d, J = 6.4
Hz, 2 H), 1.81 (s, 3 H), 1.67 (br s, 3 H).
13C NMR (75 MHz, acetone-d6): δ = 177.0 (C), 162.3 (C), 160.2
(C), 155.3 (C), 149.9 (C), 148.5 (C), 146.9 (C), 136.8 (C), 132.5
(C), 124.1 (C), 123.7 (CH), 123.0 (CH), 116.3 (CH), 112.1 (CH),
107.4 (C), 104.3 (C), 99.0 (CH), 56.4 (CH3), 25.8 (CH3), 22.2
(CH2), 18.1 (CH3).
8-(3,3-Dimethylallyl)tamarixetin (1c)
Following the typical procedure for 1a using 8c (2.8 g, 5.0 mmol)
gave 1c (1.9 g, 5.0 mmol, >99%) as pale yellow needles; mp 211–
213 °C (MeOH–H2O).
FT-IR (KBr): 3285, 2910, 1844, 1653, 1605, 1562, 1522, 1424,
1317, 1260, 1152, 1120, 1068, 1031, 1008, 983, 924, 878, 849, 796,
770 cm–1.
1H NMR (400 MHz, acetone-d6): δ = 12.08 (s, 1 H, OH), 9.64–9.54
(br s, 1 H, OH), 8.06–7.96 (br s, 1 H, OH), 7.94 (br s, 1 H, OH), 7.84
(dd, J = 9.2, 2.0 Hz, 1 H), 7.83 (d, J = 2.0 Hz, 1 H), 7.16 (d, J = 9.2
Hz, 1 H), 6.36 (s, 1 H), 5.31–5.27 (m, 1 H), 3.95 (s, 3 H), 3.58 (d,
J = 6.8 Hz, 2 H), 1.84 (s, 3 H), 1.68 (d, J = 0.8 Hz, 3 H).
13C NMR (75 MHz, acetone-d6): δ = 176.8 (C), 162.1 (C), 159.9
(C), 155.1 (C), 150.1 (C), 147.3 (C), 146.6 (C), 136.9 (C), 132.2
(C), 125.2 (C), 123.5 (CH), 121.1 (CH), 115.2 (CH), 112.1 (CH),
107.2 (C), 104.2 (C), 98.8 (CH), 56.3 (CH3), 25.8 (CH3), 22.2
(CH2), 18.2 (CH3).
2-(4-Acetoxyphenyl)-8-(3-methylbut-2-enyl)-4-oxochroman-
5,7-diyl Diacetate (8e)
Following the typical procedure for 8a using 7e (2.1 g, 5.0 mmol)
gave 8e (2.0 g, 4.2 mmol, 84%) as colorless sticks; mp 122–123 °C
(hexane–EtOAc).
FT-IR (KBr): 3501, 2964, 2924, 1771, 1697, 1604, 1510, 1371,
1189, 1067, 909, 848, 778, 721, 668 cm–1.
1H NMR (400 MHz, CDCl3): δ = 7.45 (d, J = 8.4 Hz, 2 H), 7.16 (d,
J = 8.4 Hz, 2 H), 6.53 (s, 1 H), 5.48 (dd, J = 13.6, 2.4 Hz, 1 H), 5.09–
5.04 (m, 1 H), 3.25 (d, J = 7.2 Hz, 2 H), 3.01 (dd, J = 16.8, 13.6 Hz,
1 H), 2.78 (dd, J = 16.8, 2.4 Hz, 1 H), 2.37 (s, 3 H), 2.32 (s, 3 H),
2.31 (s, 3 H), 1.65 (d, J = 0.8 Hz, 3 H), 1.58 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 189.4 (C), 169.5 (C), 169.3 (C),
168.2 (C), 161.1 (C), 153.9 (C), 150.8 (C), 148.5 (C), 135.9 (C),
132.6 (C), 127.2 (2 CH), 122.0 (2 CH), 121.3 (C), 120.7 (CH),
111.8 (C), 111.2 (CH), 78.9 (CH), 45.0 (CH2), 25.6 (CH3), 23.2
(CH2), 21.1 (CH3), 21.0 (CH3), 20.9 (CH3), 17.8 (CH3).
8-(3,3-Dimethylallyl)hesperetin (1d); Typical Procedure
To a soln of 8d (2.5 g, 5.0 mmol) in MeOH (100 mL) was added
NH4OAc (3.9 g, 50 mmol) at r.t. and the suspension was stirred for
24 h at 50–55 °C. After cooling to r.t., the resulting mixture was
concentrated in vacuo. The residue was partitioned between EtOAc
(200 mL) and H2O (100 mL). The aqueous phase was extracted with
EtOAc (2 × 100 mL). The combined organic layers were washed
with H2O (100 mL), brine (100 mL), dried (Na2SO4), and concen-
trated in vacuo. The residue was recrystallized (MeOH–H2O) to
give 1d (1.8 g, 5.0 mmol, >99%) as a white powder; mp 144–145
°C (MeOH–H2O).
8-(3,3-Dimethylallyl)quercetin (1a); Typical Procedure
To a soln of 8a (2.9 g, 5.0 mmol) in MeOH (100 mL) was added
NH4OAc (3.9 g, 50 mmol) at r.t. and the suspension was stirred for
24 h at reflux. After cooling to r.t., the resulting mixture was con-
centrated in vacuo. The residue was partitioned between EtOAc
(200 mL) and H2O (100 mL). The aqueous phase was extracted with
EtOAc (2 × 100 mL). The combined organic layers were washed
with H2O (100 mL), brine (100 mL), dried (Na2SO4), and concen-
trated in vacuo. The residue was recrystallized (MeOH–H2O) to
give 1a (1.9 g, 5.0 mmol, >99%) as pale yellow needles; mp 238–
239 °C (MeOH–H2O).
FT-IR (KBr): 3391, 2915, 1830, 1636, 1517, 1444, 1367, 1274,
1152, 1080, 1026, 989, 966, 892, 868, 834, 796, 765, 704 cm–1.
1H NMR (300 MHz, CDCl3): δ = 12.00 (s, 1 H, OH), 7.05 (d, J =
1.8 Hz, 1 H), 6.92 (dd, J = 8.4, 1.8 Hz, 1 H), 6.88 (d, J = 8.4 Hz, 1
H), 6.29 (s, 1 H, OH), 6.02 (s, 1 H), 5.73 (s, 1 H, OH), 5.33 (dd, J =
12.6, 3.0 Hz, 1 H), 5.24–5.18 (m, 1 H), 3.92 (s, 3 H), 3.31 (d, J = 7.2
Hz, 2 H), 3.04 (dd, J = 17.1, 12.6 Hz, 1 H), 2.80 (dd, J = 17.1, 3.0
Hz, 1 H), 1.73 (s, 6 H).
FT-IR (KBr): 3461, 2970, 2341, 1654, 1624, 1556, 1524, 1438,
1323, 1268, 1234, 1155, 1115, 1066, 1005, 981, 883 cm–1.
13C NMR (75 MHz, CDCl3): δ = 196.4 (C), 163.7 (C), 162.1 (C),
159.7 (C), 146.8 (C), 145.8 (C), 134.8 (C), 131.8 (C), 121.6 (CH),
117.8 (CH), 112.5 (CH), 110.6 (CH), 106.3 (C), 103.1 (C), 96.8
(CH), 78.6 (CH), 56.0 (CH3), 43.1 (CH2), 25.8 (CH3), 21.8 (CH2),
17.8 (CH3).
1H NMR (400 MHz, acetone-d6): δ = 12.10 (s, 1 H, OH), 9.68–9.42
(br m, 1 H, OH), 8.60–8.25 (br m, 2 H, 2 × OH), 7.97 (br s, 1 H,
OH), 7.88 (d, J = 2.0 Hz, 1 H), 7.74 (dd, J = 8.5, 2.0 Hz, 1 H), 7.02
(d, J = 8.5 Hz, 1 H), 6.35 (s, 1 H), 5.33–5.26 (m, 1 H), 3.57 (br d,
J = 6.9 Hz, 2 H), 1.83 (s, 3 H), 1.66 (s, 3 H).
13C NMR (75 MHz, acetone-d6): δ = 176.8 (C), 162.0 (C), 159.9
(C), 155.0 (C), 148.3 (C), 145.9 (C), 136.6 (C), 132.2 (C), 124.1
(C), 123.4 (CH), 121.4 (CH), 116.2 (CH), 115.8 (CH), 107.2 (C),
104.2 (C), 101.4 (C), 98.8 (CH), 25.9 (CH3), 22.2 (CH2), 18.1
(CH3).
8-(3,3-Dimethylallyl)naringenin (1e)
Following the typical procedure for 1d using 8b (2.3 g, 5.0 mmol)
gave 1e (1.3 g, 3.8 mmol, 76%) as a white powder; mp 206–207 °C
(MeOH–H2O).
FT-IR (KBr): 3355, 1607, 1520, 1456, 1395, 1305, 1173, 1077,
1014, 978, 944, 878, 829, 650 cm–1.
1H NMR (400 MHz, acetone-d6): δ = 12.14 (s, 1 H, OH), 9.52 (s, 1
H, OH), 8.49 (s, 1 H, OH), 7.42 (d, J = 8.4 Hz, 2 H), 6.91 (d, J = 8.4
Hz, 2 H), 6.03 (s, 1 H), 5.46 (dd, J = 12.4, 3.2 Hz, 1 H), 5.21–5.17
(m, 1 H), 3.22 (d, J = 7.2 Hz, 2 H), 3.16 (dd, J = 16.8, 12.4 Hz, 1 H),
2.78 (dd, J = 16.8, 2.8 Hz, 1 H), 1.61 (d, J = 0.8 Hz, 3 H), 1.60 (s, 3
H).
8-(3,3-Dimethylallyl)isorhamnetin (1b)
Following the typical procedure for 1a using 8b (2.8 g, 5.0 mmol)
gave 1b (1.8 g, 4.7 mmol, 93%) as pale yellow needles; mp 219–221
°C (MeOH–H2O).
FT-IR (KBr): 3447, 1653, 1624, 1559, 1540, 1507, 1457, 1320 cm–1.
1H NMR (400 MHz, acetone-d6): δ = 12.09 (s, 1 H, OH), 9.57 (br s,
1 H, OH), 8.31 (br s, 1 H, OH), 8.03 (br s, 1 H, OH), 7.90 (d, J = 2.0
Hz, 1 H), 7.86 (dd, J = 2.0, 8.4 Hz, 1 H), 7.36 (d, J = 8.4 Hz, 1 H),
13C NMR (75 MHz, acetone-d6): δ = 197.6 (C), 164.9 (C), 163.0
(C), 161.1 (C), 158.5 (C), 131.2 (C), 131.1 (C), 128.8 (2 CH), 123.7
© Georg Thieme Verlag Stuttgart · New York
Synthesis 2012, 44, 1308–1314