December 2010
1645
Experimental
partitioned between water and ether. After the ether layer was dried with an-
hydrous sodium sulfate overnight, the solvent was evaporated. The remain-
General Melting points were determined on a Yanagimoto MP 500D
1
and were uncorrected. H-NMR spectra were recorded on a Brucker WH ing residue was subjected to silica gel column chromatography (n-
300 MHz spectrometer and chemical shifts were expressed as d values hexane/dichloromethane (DCM)ϭ15 : 1) to yield compound 5 as pale yellow
(ppm) using tetramethylsilane (TMS) as an internal standard. Column chro-
matography was carried out on a Merck Si gel 60 (0.2—0.5 mM). Purity of
the compounds was checked by TLC. Compound 1 was supplied from BBP 1H, H-5Ј), 7.52—7.65 (m, 5H, H-2, 3, 4, 5, 6), 7.28 (d, 1H, Jϭ16.0 Hz, Ca-
(China) and other reagents were obtained from Sigma-Aldrich (St. Louis, H), 7.61 (d, 1H, Jϭ2.0 Hz, OCHϭCH), 7.68 (d, 1H, Jϭ16.0 Hz, Cb-H),
needles; yield 77.0% (1.16 mmol, 0.342 g); mp 112—116 °C; 1H-NMR
(CDCl3) d: 3.87 (s, 3H, OCH3), 6.99 (d, 1H, Jϭ2.0 Hz, OCHϭCH), 7.22 (s,
MO, U.S.A.).
13.01 (s, 1H, OH); Anal. Calcd for C18H14O4: C, 73.46; H, 4.79. Found: C,
Preparation of 1-(4-Allyloxy-2-hydroxyl-6-methoxyphenyl)ethanone 73.61; H, 4.67.
(2) 2,4-Dihydroxy-6-methoxyacetophenone (1) (6 g, 0.033 mol) in acetone
Synthesis of 5-Methoxy-2-phenyl-4H-furo[2,3-h]chromen-4-one (6)
(60 ml) was refluxed with allyl bromide (4.5 g, 0.037 mol) and anhyd. K2CO3 Compound 5 (441 mg, 1.5 mmol) in dry dioxane (75 ml) was added with
(20 g, 0.15 mol) for 6 h. After completion of the reaction, it was acidified DDQ (340 mg, 1.5 mmol) and the solution was refluxed for 3 h. Following
with dil. HCl and the mixture was partitioned between water and ether. Ether removal of dioxane, the residue was subjected to silica gel column chro-
was evaporated, and the residue was subjected to silica gel column chro- matography (n-hexane/ethyl acetateϭ9 : 1), providing the desired compound
matography (n-hexane/dichloromethaneϭ20 : 1), affording compound 2 as 6 as colorless needles; yield 83% (1.25 mmol, 0.364 g); mp 178—180 °C
1
an oily liquid; yield 51.0% (0.017 mol, 3.74 g); H-NMR (CDCl3) d: 2.58 (lit.5) mp 176 °C); 1H-NMR (CDCl3) d: 3.91 (s, 3H, OCH3), 6.89 (s, 1H, H-
(3H, s, COCH3), 3.91 (3H, s, OCH3), 4.98 (2H, d, Jϭ6.9 Hz, OCH2), 6.01 3), 7.02 (s, 1H, H-6), 7.12 (d, 1H, Jϭ2.0 Hz, OCHϭCH), 7.59—7.67 (m,
(1H, m, CHϭCH2), 5.61 (1H, dd, Jϭ7.9, 2.66 Hz, CHϭCHaHb), 5.68 (1H, 5H, H-2Ј, 3Ј, 4Ј, 5Ј, 6Ј), 7.79 (d, 1H, Jϭ2.0 Hz, OCHϭCH). Anal. Calcd for
dd, Jϭ13.1, 2.66 Hz, CHϭCHaHb), 6.93 (1H, d, Jϭ2.4 Hz, H-3), 7.01 (1H,
d, Jϭ2.4 Hz, H-5), 12.69 (1H, s, OH). Anal. Calcd for C12H14O4: C, 64.85;
H, 6.35. Found: C, 64.94; H, 6.41.
C18H12O4: C, 73.97; H, 4.14. Found: C, 73.88; H, 4.26.
Antibacterial Screening The antibacterial effect was determined by the
filter paper disc diffusion method.12) Discs with only dimethyl sulfoxide
Preparation of 1-(3-Allyl-2,4-dihydroxy-6-methoxyphenyl)ethanone (DMSO) were used as control, and ciprofloxacin and kanamycin were used
(3) Compound 2 (3 g, 0.014 mol) was heated cautiously in an oil-bath at as positive controls. Inhibitory activity was measured (in mm) as the diame-
150—160 °C and worked up as usual to give 3 as colorless needles; yield ter of the observed inhibition zones in triplicate. The minimum inhibitory
1
85% (0.012 mol, 2.64 g), mp 89—91 °C. H-NMR (CDCl3) d: 2.62 (3H, s, concentration (MIC, in mg/ml) was determined against S. dysenteriae (GϪ)
COCH3), 3.29 (2H, d, Jϭ7.2 Hz, CH2), 3.91 (3H, s, OCH3), 6.55 (1H, m, and S.-b-haemolyticus (Gϩ) using nutrient broth medium (DIFCO) by serial
CHϭCH2), 5.21 (1H, dd, Jϭ8.1, 2.67 Hz, CHϭCHaHb), 5.30 (1H, dd, dilution technique.12) MIC was considered to be the lowest concentration of
Jϭ13.1, 2.67 Hz, CHϭCHaHb), 7.03 (1H, s, H-3), 6.48 (1H, s, C4–OH), the tested compound (in DMSO) that inhibits the growth of bacteria.
12.58 (1H, s, C2–OH). Anal. Calcd for C12H14O4: C, 64.85; H, 6.35. Found:
C, 64.92; H, 6.29.
References
Preparation of 5-Acetyl-4-methoxy-6-hydroxybenzofuran (4) Com-
pound 3 (500 mg, 2.3 mmol) was dissolved in orthophosphoric acid (150 ml)
and an equal volume of water and osmium tetraoxide (75 mg, 0.034 mmol)
was added. The mixture was stirred on a magnetic stirrer for 1.5 h during
which period potassium periodate (2.5 g, 11 mmol) was added and the mix-
ture was stirred for two more hours. The reaction mixture was partitioned
between water and ether; the ether layer was then dried with anhydrous
sodium sulfate overnight. The solvent was evaporated, and the residue was
subjected to silica gel column chromatography (n-hexane/ethyl
acetateϭ20 : 1) to furnish 4 as colorless needles; yield 78% (1.8 mmol,
0.37 g), mp 72—73 °C. 1H-NMR (CDCl3) d: 2.59 (3H, s, COCH3), 3.93
(3H, s, OCH3), 7.12 (1H, s, H-5), 6.92 (1H, d, Jϭ2.0 Hz, OCHϭCH), 7.56
(1H, d, Jϭ2.0 Hz, OCHϭCH), 12.89 (1H, s, OH). Anal. Calcd for C11H10O4:
C, 64.07; H, 4.89. Found: C, 64.21; H, 4.95.
1) Wagner H., Farkas L., “The Flavonoids,” ed. by Harborne J. B., Mabry
T. J., Mabry H., Academic Press, New York, 1975.
2) Maurya R., Yadav P. P., Nat. Prod. Rep., 22, 400—424 (2005).
3) Kuhnau J., World Rev. Nutr. Diet., 24, 117—191 (1976).
4) Harborne J. B., “The Flavonoids, Advances in Research Since 1986,”
Chapman and Hall, London, 1994.
5) Talapatra S. K., Malik A. K., Talapatra B., Ind. J. Chem., 59, 534—536
(1982).
6) Pavanaram S. K., Row L. R., Austral. J. Chem., 9, 132—136 (1956).
7) Aneja R., Khanna R. N., Seshadri T. R., J. Chem. Soc., 163—168
(1963).
8) Rangswami S., Narayanaswmi S., Seshadri T. R., J. Chem. Soc.,
1871—1873 (1954).
9) Alam S., Sarkar Z., Islam A., J. Chem. Sci., 116, 29—32 (2004).
Synthesis of (E)-1-(4-Hydroxy-6-methoxybenzofuran-5-yl)-3-phenyl- 10) Baker W., Lothin O. M., J. Chem. Soc., 628—631 (1935).
prop-2-en-1-one (5) A mixture of compound 4 (310 mg, 1.5 mmol) and
benzaldehyde (320 mg, 3 mmol) in ethanolic solution of KOH (5%, 15 ml)
was kept at room temperature for about 72 h. The reaction mixture was di-
luted with ice cold water, acidified with cold dil. HCl, and the mixture was
11) Alam S., Acta Chim. Slov., 51, 447—452 (2004).
12) Mostahar S., Alam S., Islam A., Ind. J. Chem., 45B, 1478—1486
(2006).