Y. Hua et al. / Chinese Chemical Letters 21 (2010) 846–849
847
Fig. 1. Structures of compounds 1 and 2.
33:67, v/v) to afford compound 1 (15 mg). Fraction 1 was further subjected to silica gel (200–300 mesh) column
chromatography using mixtures of chloroform/methanol (20:1, v/v) and petroleum ether/acetone (3:1, v/v) as eluents
to yield pure 2 (11 mg) (Fig. 1).
2. Result and discussion
26
Compound 1, ½aꢁD ꢂ 60.3 (c 0.25, MeOH), was obtained as white powder, and analyzed for C38H56O14 by
negative-ion HRFABMS (m/z 735.4263 [M ꢂ H]ꢂ, calcd. for C38H55O14, 735.4251). Its IR spectrum exhibited
absorption bands for hydroxyl (3438 cmꢂ1), carbonyl (1742 and 1737 cmꢂ1), and olefinic groups (1630 cmꢂ1). The
1H and 13C NMR spectra showed signals due to one acetyl group [dC 21.0 (q), 170.9 (s)], one carbonyl group [dC 171.2
(s)], two olefinic carbons [dC 173.9 (s), 116.9 (d)], two angular methyl groups [dC 16.3 (q), 15.1 (q)], and two anomeric
carbons and their corresponding anomeric protons [dC 94.9 (d), 105.2 (d); dH 5.32 (br d, 1H, J = 3 Hz), 5.27 (d, 1H,
J = 7.5 Hz)]. In the negative FABMS, significant peaks occurred at m/z 573 [M ꢂ H ꢂ 162]ꢂ, 429
1
[M ꢂ H ꢂ 162 ꢂ 144]ꢂ, and indicated the elimination of two hexosyl moieties. Comparison of the H- and 13C-
NMR data of the aglycone with those of 5a-adynerin, 3b-b-D-diginopyranosyloxy-8,14b-epoxy-5a-card-20 (22)-
enolide showed that the structures of the two aglycones were very similar except that 1 had one additional acetoxyl
group [5]. The downfield resonance of H ꢂ 4 [dH 5.46 (br s, 1H)] and long-range correlations between the deshielded
H-4 and the acetyl carbonyl carbon [dC 170.9 (s)], suggested that the acetoxyl group was attached at C-4. 5a-Structure
was suggested by Me-19 of 1 which was shifted upfield to dC 15.1 [6]. The stereochemistry of H ꢂ 3 was determined to
be a-oriented by the ROESY correlation between Ha ꢂ 5 and H ꢂ 3 which indicated their cis relationship. The
configuration of AcO ꢂ 4 could be determined by the signal of H ꢂ 4. For a chair-like conformation of the A-ring,
when the substituent at C-4 is b-oriented, Ha ꢂ 4 appears a broad singlet. So the signal of H ꢂ 4 (br s, 1H) confirmed
the b-orientation of AcO ꢂ 4. This was further supported by the evidence that there was no correlation between H ꢂ 4
and Me-19 in the ROESY spectrum. The stereochemistry of H ꢂ C(17) was determined to be a-oriented by the
ROESY correlation between Ha ꢂ 12 (dH 0.90) and H ꢂ C(17) (dH 2.35) which indicated their cis relationship
(Table 1).
Acid hydrolysis of 1 with 1 mol/L HCl furnished two monosaccharides, which were determined to be D-glucose
and D-oleandrose by TLC comparison with authentic samples. The 13C NMR spectral data of D-oleandrose were
consistent with those reported [4,7]. Sugar proton and carbon signals in the NMR spectra of compound 1 were
assigned by 1H-1H COSY, HMQC, and HMQC-TOCSY spectra. In the HMBC spectrum, long-range couplings were
observed for H ꢂ 10 of the oleandrosyl unit to C-3 of the aglycone, H ꢂ 100 of the glucosyl unit to C-40 of the
oleandrosyl unit. The anomeric configurations of D-glucosyl and D-oleandrosyl were determined to be b and a,
respectively, from the coupling constants of the anomeric proton signals. On the basis of the above evidence, the
structure of 1 was elucidated as (17R)-4b-acetoxy-3b-[(O-b-D-glucopyranosyl-(1 ! 4)-a-D-oleandropyranosyl)-
oxy]-8, 14b-epoxy-5a-card-20(22)-enolide, and was named funingenoside U.
26
Compound 2, ½aꢁD ꢂ 31.2 (c 0.36, MeOH), was obtained as colorless needles (MeOH), mp 220–225 8C, and
analyzed for C25H34O6 by negative-ion HRFABMS (m/z 429.3155 [M ꢂ H]ꢂ, calcd. for C25H33O6, 429.3139).
Comparison of the 1H and 13C NMR spectral data of 2 with those of 1 showed that the two structures were very similar
except that there were no sugar moieties in compound 2. The stereochemistry at the chiral centers in 2 were identical to
Hua, Yan
