NATURAL PRODUCT RESEARCH
1
3
d 1.64 (3 H, d, J ¼ 6.0 Hz), d 1.52 (3 H, d, J ¼ 6.3 Hz) in the H NMR spectrum and two
H
H
13
methyl signals at d 18.9, 17.4 in the C NMR spectrum suggested two of them were
C
deoxyhexoses. The identification of six sugar moieties arabinose, xylose, rhamnose,
apiose, glucose and fucose was carried out by NMR analyses and acid hydrolysis
results. The HMBC spectrum allowed to establish the sequence of all sugar units by
long-range correlations between the proton signal of H-1 of arabinosyl group and C-1
of the aglycone, between H-1 of xylosyl group and C-3 of arabinosyl group, between
H-1 of rhamnosyl group and C-2 of arabinosyl group, between H-1 of apiosyl group
and C-3 of rhamnosyl group. In the HMBC spectrum, the correlations between H-24 of
the aglycone and C-1 of fucosyl group, between the proton signal of H-4 of fucosyl
group and C-1 of glucosyl group indicated that fucosyl group was connected to C-24
of the aglycone, and glucosyl group was linked at C-4 of fucosyl group. The linkage of
the sugar moieties was further confirmed by the correlations in NOESY spectrum
between H-1 of arabinosyl group and H-1 of the aglycone, between H-1 of xylosyl
group and H-3 of arabinosyl group, between H-2 of arabinosyl group and H-1 of
rhamnosyl group, between H-3 of rhamnosyl group and H-1 of apiosyl group, between
H-24 of the aglycone and H-1 of fucosyl group, between H-1 of glucosyl group
1
13
and H-4 of fucosyl group. By a detailed analysis of H, C NMR, DEPT, COSY, HSQC,
NOESY, and HMBC spectra, the structure of 1 was defined as (23S,24S)-21-acetyloxy-
2
4-{[O-b-D-glucopyranosyl-(1!4)-b-D-fucopyranosyl]oxy}-3b,23-dihydroxyspirosta-5,25(27)-
diene-1b-O-b-D-apiofuranosyl-(1!3)-O-(a-L-rhamnopyranosyl)-(1!2)-O-[b-D-xylopyranosyl-
(1!3)]-a-L-arabinopyranoside named thibetanoside E.
Compound 2 was obtained as a white amorphous solid. It was found to have
þ
a molecular formula of C H O from the peak at m/z 1301.5410 [M þ Na] in the
59 90 30
13
HR-ESI-MS and C NMR data. IR spectrum revealed the presence of hydroxy groups at
ꢁ
1
ꢁ1
3402 cm and carbonyl group at 1728 cm . A detailed comparison of the NMR data
of 2 with those of 1 revealed that 2 shared the same aglycone part with 1. The signals
at dH 1.89, 1.98 and dC 170.9, 170.8 showed two acetyl groups in compound 2.
Comparing with 1, the chemical shift of C-3 (d 70.0) of rhamnosyl group in 2 moved
C
an upfield shift of 9.6 ppm suggested there was no sugar at C-3 of rhamnosyl group
in 2. One acetyl group was at C-4 of rhamnosyl group on the basis of the correlation
between H-4 (d 5.73) of rhamnosyl group and C¼O (d 170.8) in the HMBC spectrum,
H
C
which was also confirmed by the downfield shift of 4.0 ppm for C-4 (d 76.5) of rham-
C
nosyl group in 2 compared with 1. Acid hydrolysis of 2 gave arabinose, xylose, rham-
1
13
nose, glucose and fucose. Through analysis of H, C NMR, DEPT, COSY, HSQC, HMBC
and NOESY data of 2, its structure was elucidated as (23S,24S)-21-acetyloxy-24-{[O-b-D-
glucopyranosyl-(1!4)-b-D-fucopyranosyl]oxy}-3b,23-dihydroxyspirosta-5,25(27)-diene-
1
b-O-(4-O-acetyl-a-L-rhamnopyranosyl)-(1!2)-O-[b-D-xylopyranosyl-(1!3)]-a-L-arabi-
nopyranoside named thibetanoside F.
Compound 3 was obtained as a white amorphous solid. It was assigned the
molecular formula C H O on the basis of its positive HR-ESI-MS at m/z 1215.5040
5
5 84 28
þ
13
–1
[
1
M þ Na] and C NMR data. Its IR spectrum revealed absorptions at 3391 cm and
–1
1
730 cm due to hydroxy and carbonyl groups, respectively. Comparison of the H
1
3
and C NMR signals of 3 with those of 1, revealed that the aglycone structure of 3
was similar to that of 1, except for one hydroxy group at C-21 in 3 instead of an