4
Z.-L. ZhouA eT AL.
and 6 quaternary carbons. e characteristic resonances due to the aglycone moiety were
observed for an isolated methylene of the cyclopropane system at δH/C 3.02, 2.76/45.3,
six tertiary methyl groups at δH/C 0.68/17.0, 0.69/15.1, 0.76/15.7, 1.05/24.4, 1.61/17.6, and
1.69/25.7, a secondary methyl at δH/C 0.92/18.2, two oxygenated methines at δH/C 3.98 /78.8
and 4.13/83.1, and three double bonds at δC 118.9, 120.3, 125.0, 130.9, 136.8, and 139.7
indicating a cycloartane-like triterpene skeleton [6]. e NMR data of the aglycone of
1 resembled those of rotundusolide C (1a)[6]. Typical difference was the presence of an
additional oxygenated carbon in the aglycone of 1. e 1H and 13C NMR spectra of 1 clearly
displayed that C-7, which was presented as a methylene in 1a [1H NMR: δ 1.92 (1H, m) and
1.33 (1H, m); 13C NMR: δ 27.9 (CH2)], was modified to an oxygenated methine in 1 [1H
NMR: δ 4.13 (1H, ddd, J = 11.8, 7.3, 4.4 Hz); 13C NMR: δ 83.1 (–CHOH)]. e chemical shif
values of C/H-7 and detailed 2D NMR analysis of COSY, ROESY, and HMBC correlations
also implied that the aglycone moiety of 1 had one more hydroxyl group attached at C-7
(Figures 2 and 3). is was further established from the observation of the downfield shifs
of C-6 and C-8 signals from δ 27.0 and 47.1 in 1a to δ 34.4 and 55.1 in 1 and the upfield
shif of C-30 signal from δ 20.1 in 1a to δ 15.7 in 1. e ROESY correlations of H-7 to H-5,
H-28, and H-21 established the stereochemistry of H-7α and 7-OHβ (Figure 3). us, the
structure of the aglycone moiety of 1 was determined as 9, 10-seco-9, 19-cycloartan-1(10),
9(11), 24(25)-triene-3α, 7β-diol. Anomeric region in the 1H NMR and 13C NMR spectra
of 1 displayed signals for four anomeric protons at δH 5.55 (1H, d, J = 7.8 Hz), 5.08 (1H,
d, J = 7.6 Hz), 4.78 (1H, d, J = 7.9 Hz), and 4.91 (1H, d, J = 7.8 Hz) with their correspond-
ing anomeric carbons at δ 105.1, 105.4, 100.8, and 102.2, respectively. Acid hydrolysis of
1 afforded D-glucose, D-xylose, and L-arabinose by GC analysis. HMBC spectrum dis-
played the correlations of anomeric proton H-1′ (δH 4.91) of D-glucopyranosyl unit with
C-3 (δC 78.8) of the aglycone, H-1″ (δH 5.55) of D-xylopyranosyl unit with C-4′ (δ 79.9)
of D-glucopyranosyl unit, H-1′′′ (δH 5.08) of L-arabinopyranosyl unit with C-6′ (δ 68.3) of
D-glucopyranosyl unit, and H-1′′′′ (δH 4.78) of D-glucopyranosyl unit with C-7 (δ 83.1) of
the aglycone, clearly indicating the location of sugar moieties. e coupling constants of
anomeric protons and 13C NMR data of the sugar moieties revealed the glucose and xylose
have a β-configuration, while the arabinose has an α-configuration. In conclusion, the
structure of 1 was elucidated as 9, 10-seco-9, 19-cycloartan-1(10), 9(11), 24(25)-triene-3α,
7β-diol 3-O-β-D-xylopyranosyl-(1→4)-[α-L-arabinopyranosyl-(1→6)]-β-D-glucopyrano-
syl-7-O-β-D-glucopyranoside, named cyprotuside A.
Cyprotuside B (2) was obtained as a white amorphous powder. HRESIMS gave a qua-
si-molecular ion peak at m/z 889.4931 [M + Na]+, corresponding to an empirical molecular
formula C46H74O15. Acid hydrolysis of 2 gave D-glucose, D-xylose, and L-arabinose by GC
analysis. ree anomeric protons were observed at δH 4.90 (1H, d, J = 8.0 Hz), 5.09 (1H, d,
J = 7.6 Hz), and 5.56 (1H, d, J = 7.6 Hz), which implied the presence of three monosaccha-
rides. e 1H and 13C NMR spectra of 2 indicated that the structure of the aglycone moiety
corresponded to 1 (Table 1). Comparison of the 1H and 13C NMR spectra of 2 with those of
1 indicated that 2 also contained a same trisaccharide chain: Ara-(1→6)-[Xyl-(1→4)]-Glc-,
which was attached at C-3 of the aglycone of 2 by HMBC spectrum and 13C NMR analysis.
erefore, 2 was determined as 9, 10-seco-9, 19-cycloartan-1(10), 9(11), 24(25)-triene-3α,
7β-diol 3-O-β-D-xylopyranosyl-(1→4)-[ α-L-arabinopyranosyl-(1→6)]-β-D-glucopyrano-
side, named cyprotuside B.