3630 Promsuwan et al.
Asian J. Chem.
Column chromatography was done with silica gel 0.063-0.200
mm or less than 0.063 mm. Preparative layer chromatography
was carried out on glass supported silica gel plates using silica
gel 60 PF254 for preparative layer chromatography.All solvents
were routinely distilled prior to use.
prenyloxyseselin (7) (340 mg, 89 %). 1H NMR (CDCl3, 400
MHz) δ 7.95 (1H, d, J = 9.6 Hz, H-4), 6.76 (1H, d, J = 10 Hz,
H-3'), 6.20 (1H, s, H-6), 6.07 (1H, d, J = 9.6 Hz, H-3), 5.54
(1H, d, J = 10 Hz, H-4'), 5.47 (1H, br t, H-2"), 4.52 (2H, d,
J = 6.4 Hz, H-1"), 1.78 (6H, s, 2CH3).1.43 (6H, s, 2CH3); 13C
NMR δ 161.4, 157.3, 155.9, 151.1, 139.3, 139.0, 127.4, 118.6,
115.0, 110.2, 103.9, 102.5, 96.3, 77.9, 28.1, 25.8, 18.2; MS
m/z 313.14 [M + H]+ (calcd. for C19H20O4+H, 313.14).
Synthesis
5,7-Dihydroxycoumarin (3):A mixture of phloroglucinol
(1) (2.00 g, 15.8 mmol), ZnCl2 (1.67 g, 12.3 mmol) and ethyl
propiolate (2) (1.9 mL) was mixed together and stirred for 2 h
at 100 ºC. Then the mixture was cooled and 5 % hydrochloric
acid (40 mL) was added. The precipitate was filtered off and
washed with boiling H2O and purified by flash column chroma-
tography using 10 % MeOH:CH2Cl2 to give 3 (1.29 g, 85 %).
1H NMR (CDCl3-CD3OD, 400 MHz) δ 7.99 (1H, d, J = 9.6
Hz, H-4), 6.23 (1H, s, H-8), 6.16 (1H, d, J = 2.4 Hz, H-6),
6.00 (1H, d, J = 9.6 Hz, H-3); 13C NMR (CDCl3) δ 163.4,
161.9, 156.5, 155.9, 140.4, 108.4, 102.8, 98.4, 94.6; MS m/z
179.04 [M + H]+ (calcd. for C9H6O4+H, 179.03).
7-Prenyloxyalloxanthyletin (8): Compound 8 (60 mg,
96 %) was synthesized with the same procedure as compound
1
7. H NMR (CDCl3, 400 MHz) δ 7.93 (1H, d, J = 9.6 Hz,
H-4), 6.12 (1H, d, J = 10 Hz, H-3'), 6.32 (1H, br s, OH), 6.12
(1H, d, J = 9.6 Hz, H-3), 5.52 (1H, d, J = 10 Hz, H-4'), 5.43
(1H, br t, H-2"), 4.54 (2H, d, J = 5.6 Hz, H-1"), 1.74 (6H, s,
13
2CH3), 1.43 (6H, s, 2CH3); C NMR δ 161.6, 157.6, 155.7,
150.2, 138.6, 127.4, 118.8, 116.3, 110.9, 106.7, 103.6, 96.3,
92.5, 77.6, 65.7, 27.9, 25.7, 18.3; MS m/z 313.14 [M + H]+
(calcd. for C19H20O4+H, 313.14).
5-Acetoxy-6-(1,1-dimethylallyl)seselin (9): A mixture
of 5-prenyloxyseselin (7) (340 mg, 1.09 mmol), NaOAc (465
mg, 9.7 mmol) and Ac2O (10 mL, excess) was refluxed with
stirring for 20 h. The cooled mixture was filtered and washed
with EtOAc. The combined filtrates were evaporated and
purified by flash column chromatograph with 5 % EtOAc:
hexane to give 5-acetoxy-6-(1,1-dimethylallyl)seselin (9) (365
mg, 94 %). 1H NMR (CDCl3, 400 MHz) δ 7.41 (1H, d, J = 9.6
Hz, H-4), 6.84 (1H, d, J = 10 Hz, H-3'), 6.25 (1H, dd, J = 17.4,
10.6 Hz, H-2"), 6.20 (1H, d, J = 9.6 Hz, H-3), 5.73 (1H, d, J =
10 Hz, H-4'), 4.92 (1H, d, J = 17.4 Hz, H-3"b), 4.86 (1H, d,
J = 10.6 Hz, H-3"a), 2.20 (3H, s, OAc), 1.50 (6H, s, 2CH3),
5-Hydroxyseselin (4), 7-hydroxyalloxanthyletin (5) and
dipetalolactone (6): To a solution of 5,7-dihydroxycoumarin
(3) (1.5 g, 8.4 mmol) in dry pyridine (3.0 mL) was added
3-methyl-2-butenal (1.7 mL, 17.6 mmol) and the reaction
mixture was stirred for 4 h at 115 ºC. Then, the reagents were
removed under reduced pressure. The solid residue was submi-
tted to flash column chromatography with gradient elution of
MeOH:CH2Cl2 (0.1-5.0 %) to afford 5-hydroxyseselin (4) (411
mg, 20 %) as the major product, 7-hydroxyalloxanthyletin (5)
(164 mg, 8 %) and dipetalolactone (6) (156 mg, 6 %) and
50 % recovered starting material.
1
5-Hydroxyseselin (4): H NMR (CDCl3-CD3OD, 400
13
1.25 (6H, s, 2CH3); C NMR δ 169.4, 160.4, 155.7, 149.1,
MHz) δ 7.96 (1H, d, J = 9.6 Hz, H-4), 6.71 (1H, d, J = 10 Hz,
H-3'), 6.12 (1H, s, H-6), 6.04 (1H, d, J = 9.6 Hz, H-3), 5.5
(1H, d, J = 10 Hz, H-4'), 1.38 (6H, s, 2CH3); 13C NMR δ 162.5,
157.3, 155.1, 150.8, 140.1, 127.2, 114.9, 109.2, 103.4, 101.9,
98.9, 77.7, 27.9; MS m/z 245.08 [M + H]+ (calcd. for
C14H12O4+H, 245.08).
148.9, 144.8, 138.4, 129.6, 125.4, 115.1, 113.0, 108.2, 106.9,
106.9, 78.4, 41.1, 27.8, 21.1; MS m/z 355.15 [M + H]+ (calcd.
for C21H22O5+H, 355.15).
7-Acetoxy-8-(1,1-dimethylallyl)alloxanthyletin (10):
Compound 10 (65 mg, 97 %) was synthesized in the same
procedure as compound 9. 1H NMR (CDCl3, 400 MHz) δ 8.03
(1H, d, J = 9.6 Hz, H-4), 6.27 (1H, dd, J = 17.4, 10.6 Hz,
H-2"), 6.28 (1H, d, J = 9.6 Hz, H-3), 6.13 (1H, d, J = 10 Hz,
H-3'), 5.61 (1H, d, J = 10 Hz, H-4'), 4.96 (1H, d, J = 17.4 Hz,
H-3"b), 4.89 (1H, d, J = 10.6 Hz, H-3"a), 2.24 (3H, s, OAc),
1
7-Hydroxyalloxanthyletin (5): H NMR (CDCl3-
CD3OD, 400 MHz) δ 7.91 (1H, d, J = 9.6 Hz, H-4), 6.57 (1H,
d, J = 10 Hz, H-3'), 6.25 (1H, s, H-8), 6.00 (1H, d, J = 9.2 Hz,
13
H-3), 5.47 (1H, d, J = 10 Hz, H-4'), 1.39 (6H, s, 2CH3); C
NMR δ 162.8, 157.0, 156.3, 150.7, 139.6, 127.1, 116.2, 109.5,
106.1, 102.9, 95.0, 77.7, 27.8; MS m/z 245.08 [M + H]+ (calcd.
for C14H12O4+H, 245.08).
13
1.61 (6H, s, 2CH3), 1.55 (6H, s, 2CH3); C NMR δ 168.9,
160.2, 153.4, 148.8, 148.6, 147.3, 138.4, 130.0, 120.3, 116.1,
113.4, 110.8, 108.1, 107.2, 77.8, 41.1, 21.1; MS m/z 355.15
[M + H]+ (calcd. for C21H22O5+H, 355.15).
Dipetalolactone (6): 1H NMR (CDCl3, 400 MHz) δ 7.93
(1H, d, J = 9.6 Hz, H-4), 6.78 (1H, d, J = 10 Hz, H-4'), 6.61
(1H, d, J = 10 Hz, H-4''), 6.11 (1H, d, J = 9.6 Hz, H-3), 5.57
(1H, d, J = 10 Hz, H-3'), 5.54 (1H, d, J = 10 Hz, H-3"), 1.45
(6H, s, 2CH3); 13C NMR δ 161.3, 151.9, 150.1, 138.8, 127.7,
127.5, 115.9, 115.2, 110.6, 105.9, 103.2, 102.3, 78.0, 28.2,
28.1; MS m/z 311.13 [M + H]+ (calcd. for C19H18O4+H, 311.13).
5-Prenyloxyseselin (7): A mixture of 5-hydroxyseselin
(4) (300 mg, 1.22 mmol), K2CO3 (765 mg, 9.5 mmol ), 3,3-
dimethylallyl bromide (0.2 mL, 1.73 mmol) and acetone (20
mL) was refluxed with stirring for 1 h. The solvent was evapo-
rated and the residue was partitioned between EtOAc and brine,
the organic layer was washed with 5 % Na2CO3, brine, dried
and evaporated. The residue was purified by flash column
chromatography with 90 % CH2Cl2: hexane and gave 5-
5-Hydroxy-6-(1,1-dimethylallyl)seselin (11): The
solution of 5-acetoxy-6-(1,1-dimethylallyl)seselin (9) (365 mg,
1.03 mmol) in MeOH (5 mL) and 1 % NaOH in MeOH (8.2
mL, 2.06 mmol) was stirred at room temperature for 3 h. The
solution was neutralized with 5 % HCl then evaporated and
the residue was partitioned between EtOAc and brine. The
EtOAc layer was washed with brine, dried, evaporated and
the residue was submitted to flash column chromatography
(CH2Cl2 to 5 % EtOAc:CH2Cl2) to give 5-hydroxy-6-(1,1-
dimethylallyl)seselin (11) (310 mg, 97 %). 1H NMR (CDCl3,
400 MHz) δ 7.88 (1H, d, J = 9.6 Hz, H-4), 6.74 (1H, d, J = 10
Hz, H-3'), 7.25 (1H, br s, OH), 6.63 (1H, dd, J = 17.8, 10.4
Hz, H-2"), 6.03 (1H, d, J = 9.6 Hz, H-3), 5.51 (1H, d, J = 10