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2007, 1161, 334–337.
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TFA)-CH3CN (68:32) gave the derivative S-1. The HRESIMS of S-1
gave a quasimolecular ion [M + H]+ peak at m/z 447.1245 (calcd for
C18H27N2O7S2, 447.1254), which was consistent with the reference.12
L-Rhamnose was treated similarly and gave the derivative S-2, the
HRESIMS of which indicated an [M + H]+ peak at m/z 431.1298 (calcd
for C18H27N2O6S2, 431.1305), consistent with ref 12.
Compound 1 was hydrolyzed with HCl and extracted with CH2Cl2.
The aqueous layer was passed through a Sephadex LH-20 column, and
the eluate was concentrated. The residue was dissolved in pyridine (0.4
mL) and stirred with L-cysteine methyl ester (10 mg) for 1.5 h at 60
°C, and then o-tolyl isothiocyanate (40 µL) was added to the mixture,
which was heated at 60 °C for 1.5 h. The reaction mixture was analyzed
by HPLC detected at 250 nm. Analytical HPLC was performed on a
Phenomenex C18 column (4.6 × 250 mm) at 25 °C using a gradient of
CH3CN-0.2% TFA in H2O [0-23 min (32:68), 23-30 min (32:68 to
70:30), 30-60 min (70:30)] as the mobile phase. Peaks were detected
with an Agilent DAD detector. D-Glucose and L-rhamnose were
identified as the sugar moieties of 1, as they had the same retention
times as S-1 (tR 11.4 min) and S-2 (tR 18.7 min), respectively
(Supporting Information).6,12 D-Glucose and L-rhamnose moieties were
identified in 2, and an L-rhamnose unit in 3 and 4 by the same method.
Calculation Details. All calculations were performed at 298 K by
the Gaussian03 program package.18 Ground-state geometries of 1a were
optimized at the B3LYP/6-31+G* level, and the transition structure
of the atropisomerization was located using the synchronous transit-
guided quasi-Newton (STQN) method.19,20 Frequency analyses were
done to identify the nature (minima or transition state) of the optimized
geometries. Then, the relevant energies were refined using the B3LYP/
6-311++G** single-point calculations at the B3LYP/6-31+G* geom-
etries. All energies are corrected by ZPVE.
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S.; Yang, Y.; Shi, J. J. Nat. Prod. 2008, 71, 905–909.
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Lou, H. X. Toxicol. In Vitro 2009, 23, 29–36.
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M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.; Kudin,
K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone,
V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.;
Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa,
J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene,
M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Bakken, V.;
Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev,
O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala,
P. Y.; Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.;
Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.; Farkas,
O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.;
Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.;
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Acknowledgment. Financial support from the National Natural
Science Foundation of China (No. 30730109 and 30672611) and
Science Foundation of Shandong Province (No. JQ200806) is gratefully
acknowledged.
Supporting Information Available: Copies of the 1D and 2D NMR,
MS, and IR spectra of 1-4 and 1a, detailed information concerning
the sugar identification, and the experimental details of the cytotoxic
assay. This material is available free of charge via the Internet at http://
pubs.acs.org.
References and Notes
(1) Wu, Z. Y.; Li, X. W. Flora of China (Zhongguo Zhiwu Zhi); Science
Press: Beijing, 1977; Vol. 65 (2), p 353.
(2) Wang, B. Q. National Tibetan Medicine; Chinese Medical Multimedia
Press: Beijing, 2004; Vol. 1, p 161.
(3) Ren, D. M.; Guo, H. F.; Yu, W. T.; Wang, S. Q.; Ji, M.; Lou, H. X.
Phytochemistry 2008, 69, 1425–1433.
(19) Peng, C.; Schlegel, H. B. Isr. J. Chem. 1993, 33, 449–454.
(20) Peng, C.; Ayala, P. Y.; Schlegel, H. B.; Frisch, M. J. J. Comput. Chem.
1996, 17, 49–56.
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