3244
Y. R. Lee, L. Xia
PAPER
oration of EtOH and extraction with EtOAc (3 × 50 mL), then
washing with 2 N HCl (30 mL) and brine (30 mL), drying (MgSO4),
and removal of the solvent followed by flash column chromatogra-
phy on silica gel (hexane–EtOAc, 10:1) gave 15 (129 mg, 96%) as
a solid; mp 92–93 °C.
tion mixture was refluxed for 10 h and then cooled to r.t. H2O (30
mL) was added and the soln was extracted with EtOAc (3 × 30 mL).
Evaporation of the solvent and purification by column chromatog-
raphy on silica gel (hexane–EtOAc, 7:1) gave 12 (282 mg, 89%) as
an oil.
IR (KBr): 2975, 1636, 1603, 1555, 1447, 1256, 1225, 1154, 1121,
1040, 990, 878, 818, 766 cm–1.
IR (neat): 2926, 2855, 1613, 1588, 1447, 1366, 1285, 1208, 1165,
1119, 1076, 962, 816, 775 cm–1.
1H NMR (300 MHz, CDCl3): d = 14.29 (s, 1 H), 8.11 (d, J = 15.7
Hz, 1 H), 7.76 (d, J = 15.7 Hz, 1 H), 7.61–7.58 (m, 2 H), 7.41–7.24
(m, 3 H), 6.57 (d, J = 9.9 Hz, 1 H), 6.05 (s, 1 H), 5.45 (d, J = 9.9 Hz,
1 H), 3.81 (s, 3 H), 1.53 (s, 6 H).
1H NMR (300 MHz, CDCl3): d = 13.8 (s, 1 H), 6.56 (d, J = 10.0 Hz,
1 H), 6.00 (s, 1 H), 5.35 (d, J = 10.0 Hz, 1 H), 5.09–5.04 (m, 1 H),
3.80 (s, 3 H), 2.63 (s, 3 H), 2.12–2.05 (m, 2 H), 1.85–1.77 (m, 2 H),
1.63 (s, 3 H), 1.54 (s, 3 H), 1.37 (s, 3 H).
13C NMR (75 MHz, CDCl3): d = 193.3, 172.6, 168.8, 161.7, 156.1,
142.7, 136.0, 134.2, 130.6, 129.7, 129.4, 128.9, 128.7, 127.8, 125.1,
117.1, 93.1, 78.4, 56.2, 28.3.
13C NMR (75 MHz, CDCl3): d = 203.1, 166.3, 160.9, 156.3, 132.0,
123.6, 123.1, 117.0, 105.7, 102.4, 92.0, 80.6, 55.7, 41.4, 33.1, 26.5,
25.6, 23.0, 17.6.
MS (EI): m/z (%) = 336 (35) [M+], 322 (16), 321 (74), 218 (13), 217
MS (EI): m/z (%) = 316 (10) [M+], 234 (14), 233 (100), 215 (8), 109
(100), 160 (9), 103 (7).
(5), 97 (6), 95 (7), 81 (6).
HRMS: m/z [M+] calcd for C21H20O4: 336.1362; found: 336.1365.
HRMS: m/z [M+] calcd for C19H24O4: 316.1675; found: 316.1674.
1-(7-Hydroxy-5-methoxy-2,2-dimethyl-2H-chromen-8-yl)-3-[4-
(methoxymethoxy)phenyl]-2-propen-1-one (16)
Boesenbergin A (2)
To a soln of 12 (158 mg, 0.5 mmol) in EtOH (10 mL) was added
KOH (140 mg, 2.5 mmol) and benzaldehyde (13) (64 mg, 0.6
mmol) at r.t. The reaction mixture was stirred for 48 h at r.t. Evap-
oration of EtOH and extraction with EtOAc (3 × 50 mL), then
washing with 2 N HCl (30 mL) and brine (30 mL), drying (MgSO4),
and removal of the solvent followed by flash column chromatogra-
phy on silica gel (hexane–EtOAc, 10:1) gave 2 (194 mg, 96%) as a
solid; mp 89–90 °C.
To a soln of 11 (124 mg, 0.5 mmol) in EtOH (10 mL) was added
KOH (140 mg, 2.5 mmol) and aldehyde 14 (100 mg, 0.6 mmol) at
r.t. The reaction mixture was stirred for 48 h at r.t. Evaporation of
EtOH and extraction with EtOAc (3 × 50 mL), then washing with 2
N HCl (30 mL) and brine (30 mL), drying (MgSO4), and removal of
the solvent followed by flash column chromatography on silica gel
(hexane–EtOAc, 10:1) gave 16 (178 mg, 90%) as an oil.
IR (neat): 2922, 2851, 1604, 1551, 1510, 1346, 1225, 1152, 1121,
1082, 992, 831, 774 cm–1.
IR (KBr): 2924, 2855, 1634, 1603, 1555, 1449, 1345, 1231, 1208,
990, 897, 818, 768, 737 cm–1.
1H NMR (300 MHz, CDCl3): d = 14.34 (s, 1 H), 8.03 (d, J = 15.7
Hz, 1 H), 7.73 (d, J = 15.7 Hz, 1 H), 7.54 (d, J = 8.5 Hz, 2 H), 7.05
(d, J = 8.5 Hz, 2 H), 6.56 (d, J = 9.9 Hz, 1 H), 6.04 (s, 1 H), 5.44 (d,
J = 9.9 Hz, 1 H), 5.21 (s, 2 H), 3.84 (s, 3 H), 3.48 (s, 3 H), 1.53 (s,
6 H).
1H NMR (300 MHz, CDCl3): d = 14.25 (s, 1 H), 8.11 (d, J = 15.6
Hz, 1 H), 7.76 (d, J = 15.6 Hz, 1 H), 7.60–7.57 (m, 2 H), 7.39–7.34
(m, 3 H), 6.62 (d, J = 10.0 Hz, 1 H), 6.04 (s, 1 H), 5.41 (d, J = 10.0
Hz, 1 H), 5.09–5.05 (m, 1 H), 3.81 (m, 3 H), 2.20–2.08 (m, 2 H),
1.90–1.71 (m, 2 H), 1.62 (s, 3 H), 1.48 (s, 6 H).
HRMS: m/z [M+] calcd for C23H24O6: 396.1573; found: 396.1571.
13C NMR (75 MHz, CDCl3): d = 193.2, 167.6, 161.5, 156.2, 142.3,
135.9, 132.5, 130.2, 129.1, 128.5, 127.9, 123.7, 123.5, 117.3, 106.3,
103.1, 92.5, 80.0, 55.7, 41.5, 26.6, 25.6, 23.1, 17.6.
Citrunobin (1)
To a soln of 16 (158 mg, 0.4 mmol) in EtOH (10 mL) was added 3
N HCl (5 drops) and the reaction mixture was heated at 50 °C for 1
h. The mixture was cooled, diluted with H2O (20 mL), and extracted
with EtOAc (3 × 30 mL). The combined organic phases were
washed with sat. NaHCO3 soln (30 mL) and H2O (30 mL), and dried
(MgSO4). Removal of the solvent under reduced pressure left an
oily residue, which was then purified by column chromatography
on silica gel (hexane–EtOAc, 4:1) to give 1 (134 mg, 95%) as a sol-
id; mp 183–184 °C.
HRMS: m/z [M+] calcd for C26H28O4: 404.1988; found: 404.1990.
1-[5-Hydroxy-7-methoxy-2-methyl-2-(4-methyl-3-pentenyl)-
2H-chromen-6-yl]ethanone (18)
To a soln of 2,4-dihydroxy-6-methoxyacetophenone (17) (182 mg,
1.0 mmol) and citral (304 mg, 2.0 mmol) in xylene (20 mL) was
added ethylenediamine diacetate (18 mg, 0.1 mmol) at r.t. The reac-
tion mixture was refluxed for 10 h and then cooled to r.t. H2O (30
mL) was added and the soln was extracted with EtOAc (2 × 30 mL).
Evaporation of the solvent and purification by column chromatog-
raphy on silica gel (hexane–EtOAc, 7:1) gave 18 (285 mg, 90%) as
an oil.
IR (KBr): 3343, 2926, 1630, 1605, 1547, 1514, 1445, 1348, 1221,
1155, 1121, 1042, 986, 833, 737 cm–1.
1H NMR (300 MHz, CDCl3): d = 14.34 (s, 1 H), 8.01 (d, J = 15.6
Hz, 1 H), 7.74 (d, J = 15.6 Hz, 1 H), 7.50 (d, J = 8.5 Hz, 2 H), 6.85
(d, J = 8.5 Hz, 2 H), 6.57 (d, J = 10.0 Hz, 1 H), 6.06 (s, 1 H), 5.45
(d, J = 10.0 Hz, 1 H), 3.84 (s, 3 H), 1.52 (s, 6 H).
13C NMR (75 MHz, CDCl3): d = 193.2, 167.3, 161.2, 158.2, 155.7,
142.6, 130.3, 128.4, 125.0, 124.5, 116.7, 116.2, 104.5, 103.3, 92.7,
78.3, 55.7, 28.1.
IR (neat): 2924, 2855, 1622, 1591, 1377, 1267, 1165, 1142, 1123,
883, 835, 812, 733 cm–1.
1H NMR (300 MHz, CDCl3): d = 14.29 (s, 1 H), 6.68 (d, J = 10.0
Hz, 1 H), 5.85 (s, 1 H), 5.37 (d, J = 10.0 Hz, 1 H), 5.10–5.06 (m, 1
H), 3.82 (s, 3 H), 2.57 (s, 3 H), 2.21–2.04 (m, 2 H), 1.79–1.64 (m, 2
H), 1.61 (s, 3 H), 1.56 (s, 3 H), 1.39 (s, 3 H).
HRMS: m/z [M+] calcd for C21H20O5: 352.1311; found: 352.1310.
13C NMR (75 MHz, CDCl3): d = 203.0, 163.0, 161.8, 160.5, 131.8,
124.0, 123.8, 116.4, 105.5, 102.4, 80.6, 55.5, 41.7, 33.0, 29.7, 27.2,
22.6, 17.6, 14.1.
MS (EI): m/z (%) = 316 (8) [M+], 234 (14), 233 (100), 215 (12), 109
(5), 97 (8), 95 (7), 85 (5), 83 (7), 81 (6).
1-[7-Hydroxy-5-methoxy-2-methyl-2-(4-methyl-3-pentenyl)-
2H-chromen-8-yl]ethanone (12)
To a soln of 2,6-dihydroxy-4-methoxyacetophenone (10) (182 mg,
1.0 mmol) and citral (304 mg, 2.0 mmol) in xylene (20 mL) was
added ethylenediamine diacetate (18 mg, 0.1 mmol) at r.t. The reac-
HRMS: m/z [M+] calcd for C19H24O4: 316.1675; found: 316.1677.
Synthesis 2007, No. 20, 3240–3246 © Thieme Stuttgart · New York