Structure determination of baeckeins C and D
1160, 1075, 1010, 948, 896, 808, 731, and 623; CD (c = 0.10, MeOH):
281 nm ( Δe -5.50), 307 nm ( Δe +4.32), 332nm ( Δe -4.38), and
378 nm ( Δe +2.51); 1H- and 13C-NMR data, see Table 1; ESI-
MS m/z 791 [M–H]–, HR-ESI-MS m/z 791.1463 [M–H]– (calcu-
lated for C38H31O19, 791.1465).
of Natural Medicinal Chemistry, China Pharmaceutical University),
and Mr. L. Feng (Simcere Pharmaceutical Group) for providing
assistance in technology and equipment.
References
Baeckein D (compound 2)
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Acid hydrolysis and GC analysis
Each compound (2mg) was hydrolyzed with 10% HCl–dioxane (1 :
1, 5 ml) at 80 ꢁC for 4 h. After extraction with ethyl acetate (5mlꢀ 3),
the sugar component in the aqueous layer was evaporated under
reduced pressure and then examined by silica gel TLC with
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pyridine, and 2 mg of L-cysteine methyl ester hydrochloride was
added, followed by heating at 60 ꢁC for 2 h. The reaction mixture
was concentrated to dryness with N2 gas, and then trimethylsilyl
imidazole was added to the residue, followed by stirring at 60 ꢁC
for 1 h. Finally, the resulted solution was extracted with cyclohex-
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same reaction and GC analysis under the same conditions.
Computational
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phase. The ECD spectra were then simulated by overlapping
Gaussian functions for each transition.
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Acknowledgements
This work was supported by grants from a project funded by the
Priority Academic Program Development of Jiangsu Higher Edu-
cation Institutions. The authors appreciate the kind help of Dr K.
Zan (State Key Laboratory of Natural and Biomimetic Drugs,
Peking University Health Science Center), Dr J. Luo (Department
Magn. Reson. Chem. 2011, 49, 757–761
Copyright © 2011 John Wiley & Sons, Ltd.
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