D. Y. W. Lee et al. / Tetrahedron Letters 44 (2003) 6857–6859
6859
unsuccessful. For instance, treatment of (19) with
BBr3,11 BCl3,12 Ph2PLi in THF,13 pyridinium tribromide
in xylene,14 EtSNa in DMF,15 refluxing in concentrated
HBr,16 48% HBr with NaI at 110°C,17 NaCN in DMSO
at 125°C,18 and AlBr3 in refluxing EtSH.19 We noticed
that upon refluxing of (19) with Me3SiI in CHCl3 for
4 days gave a small amount of 7-O-methylpuerarin
6. Lin, R. C.; Li, T. K. Am. J. Clin. Nutrition 1998, 68 (6
Suppl), 1512S.
7. (a) Eade, R. A.; McDonald, F. J.; Simes, J. J. H. Aust. J.
Chem. 1975, 28, 2011; (b) Eade, R. A.; McDonald, F. J.;
Pham, H. P. Aust. J. Chem. 1978, 31, 2699.
8. Du, Y.; Linhardt, R. J. Tetrahedron 1998, 54, 9913.
9. (a) Calzada, E.; Clarke, C. A.; Roussin-Bouchard, C.;
Wightman, R. H. J. Chem. Soc., Perkin Trans. 1 1995,
517; (b) Kraus, G. A.; Molina, M. T. J. Org. Chem. 1988,
53, 752.
10. Qiu, D.; Wang, Y.; Cai, M. Chem. J. Chinese Univ. 1989,
5, 158.
11. McOmie, J. F. W.; West, D. E. Org. Synth. Coll. Vol. V.
1973, 412.
12. Carvalho, C. F.; Sargent, M. V. J. Chem. Soc., Chem.
Commun. 1984, 4, 227.
13. Ireland, R. E.; Walba, D. M. Org. Synth. 1977, 56, 44.
14. Ijaz, A. S.; Alam, M.; Ahmad, B. Indian J. Chem. Sect. B
1994, 33B, 288.
15. Feutrill, G. I.; Mirrington, R. N. Tetrahedron Lett. 1970,
16, 1327; Aust. J. Chem. 1972, 25, 1719, 1731.
16. Kawasaki, I.; Matsuda, K.; Kaneko, T. Bull. Chem. Soc.
Jpn. 1971, 44, 1986.
20
(21), unfortunately,
a prolonged reflux failed to
improve the yield and further demethylation at C-7
position never happened. Finally, when CH3CN was
used as solvent, refluxing with Me3SiI for 5 days,
starting material 19 was consumed and converted to the
desired target compound (1)21 in 35% yield along with
partially demethylated 7-O-methylpuerarin (21) in 39%
yield after column chromatography. Further prolong-
ing the reaction time did not improve the yield. The
overall yield of the synthesis of (1) was 10%. The
spectroscopic and physical data were identical to the
natural sample of puerarin (1). In order to improve the
yield at the final step, other protecting groups are being
examined.
Acknowledgements
17. Li, G.; Patel, D.; Hruby, V. J. Tetrahedron Lett. 1993, 34,
5393.
18. McCarthy, J. R.; Moore, J. L.; Cregge, R. J. Tetrahedron
Lett. 1978, 52, 5183.
19. Node, M.; Nishide, K.; Fuji, K.; Fujita, E. J. Org. Chem.
1980, 45, 4275.
Financial support from National Institute of Alcohol
Abuse and Alcoholism (N44AA02006) is greatly
acknowledged.
20. Jung, M. E.; Lyster, M. A. J. Org. Chem. 1977, 42, 3761.
21. Spectral data for compound 1: solid, mp: 184–186°C;
HRMS m/e for C21H20O9+H calcd 417.1185, found
417.1174, 1H NMR (CD3OD, 300 MHz, ppm), l 3.40–
3.60 (3H, m), 3.72–3.87 (2H, m), 4.12 (1H, s, br), 5.09
(1H, d, J=9.9 Hz, H-1¦), 6.85 (2H, d, J=8.7 Hz, H-2%
and H-6%), 6.99 (1H, d, J=9 Hz, H-6), 7.37 (2H, d, J=8.4
Hz, H-3% and H-5%), 8.06 (1H, d, J=8.7 Hz, H-5), 8.20
(1H, s, H-2); 13C NMR (CD3OD, 75.4 MHz, ppm), l
62.74, 71.68, 72.98, 75.63, 79.98, 82.72, 113.1, 116.23,
116.58, 118.45, 124.16, 125.48, 128.07, 131.34, 154.46,
158.64, 162.97, 178.25.
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