4414
T. Narender et al. / Tetrahedron Letters 49 (2008) 4409–4415
OMe
OMe
OMe
HO
OH
OMe
O
O
HCOOH
O
O
30
29
OMe
OMe
OMe
NaOAc, EtOH
AcO
OH
OMe
HO
O
Reflux, 20 h
74%
O
O
18a
31
Scheme 2. Synthesis of prenylated flavanone 31.
was dried over anhyd Na2SO4 and filtered, the solvent was evapo-
rated under reduced pressure. The crude mixture was purified by
silica gel column chromatography using hexane–ethyl acetate
(95:5) as a mobile phase to afford compound 25 (205 mg, 82%);
IR (neat) 2977, 2931, 1766, 1672, 1591, 1421, 1367, 1203, 1162,
the solvent was evaporated under reduced pressure. The residue
was purified by column chromatography using hexane–ethyl
acetate (90:10) solvent system to afford flavanone 31 (66 mg,
74%); mp: 136–138 °C; IR (KBr) 3021, 2973, 2930, 1669, 1609,
1516, 1459, 1374, 1217, 1033, 759 cmꢂ1
;
1H NMR (CDCl3,
1046, 908 cmꢂ1
;
1H NMR (CDCl3, 300 MHz) d 7.66 (d, J = 8.55 Hz,
200 MHz) d 7.69 (s, 1H), 6.99 (m, 2H), 6.90 (s, 1H), 6.47 (s, 1H),
5.34 (m, 2H), 3.91 (s, 3H), 3.89 (s, 3H), 3.31 (d, J = 7.01 Hz, 2H),
3.05 (dd, J = 3.82, 16.99 Hz, 1H), 2.82 (m, 1H), 1.75 (s, 6H); 13C
NMR (CDCl3, 50 MHz) d 191.7, 162.5, 162.4, 149.8, 149.7, 135.5,
131.8, 128.8, 122.7, 121.7, 119.3, 114.9, 111.5, 109.8, 104.0, 80.2,
56.4 (2C), 44.7, 30.1, 26.3, 18.3; MS (ESI) m/z 369.2 (M+H)+; HRMS
(ESI) calcd for C22H25O5 (M+H)+: 369.17020, found. 369.17185.
1H), 6.66 (d, J = 8.55 Hz, 1H), 2.63 (t, J = 6.51 Hz, 2H), 2.61 (s, 3H),
2.33 (s, 3H), 1.84 (t, J = 6.51 Hz, 2H), 1.41 (s, 6H); 13C NMR (CDCl3,
75 MHz) d 199.3, 168.8, 155.3, 152.8, 129.1, 126.2, 115.2, 113.4,
75.8, 32.3, 31.6, 27.1 (2C), 21.1, 17.8; MS (ESI) m/z 263.0 (M+H)+;
HRMS (ESI) calcd for
263.12770.
C
15H19O4 (M+H)+: 263.12833, found.
Acknowledgements
2.3. Representative procedure for the preparation of 1-(5-
hydroxy 2,2-dimethyl-chroman-8-yl)-3-(4-methoxy-phenyl)
propenone (26)
The authors are thankful to the Director, CDRI for support on
the synthesis of antiparasitic agents and the SAIF Division of CDRI
for spectral data and CSIR, New Delhi for financial support.
To a solution of 25 (150 mg, 0.57 mmol) and KOH (200 mg dis-
solved in 5 mL of aqueous ethanol) was added p-methoxybenzal-
dehyde (117 mg, 0.85 mmol). The mixture was kept at room
temperature for 24 h. The resultant mixture was quenched in ice-
cold water and acidified with 1 N HCl. The crude product was fil-
tered under suction and extracted with ethyl acetate (3 ꢁ 25 mL).
The combined extract was washed with water (2 ꢁ 10 mL). The
organic layer obtained after extraction was dried over anhyd
Na2SO4 and filtered, the solvent was evaporated under reduced
pressure. The crude mixture was purified by silica gel column chro-
matography using hexane–ethyl acetate (90:10) solvent system to
afford compound 26 (110 mg, 56%); mp: 184–186 °C; IR (KBr)
3019, 2928, 2854, 1641, 1592, 1512, 1440, 1244, 1217, 1172,
Supplementary data
Spectral data of all the synthetic compounds. Supplementary
data associated with this article can be found, in the online version,
References and notes
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1071, 758 cmꢂ1
;
1H NMR (CDCl3, 300 MHz)
d
8.32 (d,
J = 15.15 Hz, 1H), 7.69 (m, 3H), 7.36 (d, J = 15.15 Hz, 1H), 7.01 (d,
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