Polyoxypregnane glycosides from the flowers of Dregea volubilis

Article abstract of DOI:10.1016/S0031-9422(02)00260-1

Three novel polyoxypregnane glycosides, volubiloside A, B and C (1-3), were isolated from the flowers of Dregea volubilis Linn., and their structures were elucidated as drevogenin D-3-O-β-D-glucopyranosyl (1→4)-6-deoxy-3-O-methyl-β-D-allopyranosyl (1→4)-β-D-cymaropyranosyl (1→4)-β-D-cymaropyranoside, drevogenin D-3-O-β-D-glucopyranosyl (1→4)-6-deoxy-3-O-methyl-β-D-allopyranosyl (1→4)-β-D-cymaropyranosyl (1→4)-β-D-digitoxopyranoside and drevogenin P-3-O-β-D-glucopyranosyl (1→4)-6-deoxy-3-O-methyl-β-D-allopyranosyl (1→4)-β-D-cymaropyranosyl (1→4)-β-D-cymaropyranoside, respectively, on the basis of extensive NMR experiments, MALDI-TOF MS, and some chemical strategies.

Full text of DOI:10.1016/S0031-9422(02)00260-1

Phytochemistry 61 (2002) 383–388
www.elsevier.com/locate/phytochem
Polyoxypregnane glycosides from the flowers of Dregea volubilis
Niranjan P. Sahua,*, Nilendu Pandaa, Nirup B. Mandala,
a
SukdebBanerjee , Kazuo Koikeb, Tamotsu Nikaidob
aIndian Institute of Chemical Biology, 4 Raja SC Mullick Road, Jadavpur, Kolkata-700032, India
bDepartment of Pharmacognosy, School of Pharmaceutical Sciences, Toho University,
2-2-1 Miyama, Funabashi, Chiba 274-8510, Japan
Received 7 February 2002; received in revised form 21 June 2002
Abstract
Three novel polyoxypregnane glycosides, volubiloside A, B and C (1–3), were isolated from the flowers of Dregea volubilis Linn.,
and their structures were elucidated as drevogenin d-3-O-b-d-glucopyranosyl (1!4)-6-deoxy-3-O-methyl-b-d-allopyranosyl (1!4)-
b-d-cymaropyranosyl (1!4)-b-d-cymaropyranoside, drevogenin d-3-O-b-d-glucopyranosyl (1!4)-6-deoxy-3-O-methyl-b-d-allo-
pyranosyl (1!4)-b-d-cymaropyranosyl (1!4)-b-d-digitoxopyranoside and drevogenin P-3-O-b-d-glucopyranosyl (1!4)-6-deoxy-
3-O-methyl-b-d-allopyranosyl (1!4)-b-d-cymaropyranosyl (1!4)-b-d-cymaropyranoside, respectively, on the basis of extensive
NMR experiments, MALDI-TOF MS, and some chemical strategies.
# 2002 Elsevier Science Ltd. All rights reserved.
Keywords: Dregea volubilis; Wattakaka volubilis; Marsdenia volubilis; Asclepiadaceae; Polyhydroxypregnane glycoside; Volubiloside A, B and C;
Drevogenin D; Drevogenin P; Conduritol A; Quercetin; Quercetin-3-O-rutinoside, 2D NMR
1. Introduction
Dregea volubilis (L. f.) Benth. ex Hook. f. (Syn. Wat-
takaka volubilis (L. f.) Stapf., Marsdenia volubilis
Cooke) (Family: Asclepiadaceae) commonly known as
‘‘Jukti’’ is a tall, woody climber occurring throughout
the hotter parts of India. The alcoholic extract of the
plant is reported (Chadha, 1976) to show activity on the
central nervous system, as well as anticancer activity
against sarcoma 180 in the mice. Previous chemical
investigations (Yoshimura et al., 1983, 1985) on the
ground stems of the plant D. volubilis collected from
Thailand led to the isolation of a number of C/D-cis-
polyoxypregnane glycoside derivatives. However, no
detailed chemical investigation has appeared on the
plant growing in India. The present paper reports the
isolation and characterization of three new poly-
oxypregnane glycosides, named volubiloside A, B and C
(1–3) along with conduritol A, quercetin, and quercetin-
3-O-rutinoside from the flowers of the plant.
* Corresponding author. Fax: +91-33-473-5197.
E-mail address: npsahu@iicb.res.in (N.P. Sahu).
0031-9422/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S0031-9422(02)00260-1

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N.P. Sahu et al. / Phytochemistry 61 (2002) 383–388
2. Results and discussion
from its physical and spectral data (Singhal et al., 1980;
Yoshimura et al., 1985). Paper chromatography of the
acid hydrolyzate revealed the existence of three different
kinds of monosaccharides, two of which were identified
as glucose and cymarose by direct comparison with
authentic samples. Interpretation of the COSY and
TOCSY spectra revealed that three of the sugar units
belonged to 6-deoxy sugars (systems B, C, and D). The
other sugar was identified to be b-d-glucopyranose based
on the acid hydrolysis experiment and the all trans-diaxial
disposition of the ring protons (Table 2). The spin systems
of the C and D sugars each contained four methines, one
methylene and a terminal methyl group, and both of them
displayed a correlation pattern in the COSY spectrum
characteristic of 2,6-deoxy sugars (Jia et al., 2002). The
location of a methoxy group at C-3 was determined from
the long-range HMBC couplings (ꢀ 3.60/78.1 and 4.03/
58.9 for C; 3.61/78.0 and 4.03/59.0 for D). In combination
with the information from the 13C NMR spectrum and
NOESY, the C and D sugar units were identified as
2,6-dideoxy-3-O-methyl-b-allopyranose (cymarose).
Volubiloside A (1) displayed a quasimolecular ion
peak at m/z 999 [M+Na]+ in the MALDI-TOF mass
spectrum indicating the molecular weight to be 976.
This information, together with the data from the ele-
mental analysis and 13C NMR DEPT spectrum, sug-
gested the molecular formula to be C48H80O20. The
isolate gave positive Liebermann–Burchard and Keller–
Kiliani tests indicating the presence of Á5-steroid and
2-deoxy sugar(s) moieties in the molecule. The carbon
and proton signals of 1 in the NMR spectra were
1
assigned by extensive studies of H–1H COSY, HET-
COR, TOCSY and HMBC spectra (Tables 1 and 2).
The 1H and 13C NMR spectra displayed signals for four
anomeric protons at d 4.98 (d, J=7.8 Hz), 5.08 (d,
J=7.8 Hz), 5.09 (dd, J=1.7, 9.4 Hz), and 5.28 (dd,
J=1.6, 9.6 Hz) (labeled A–D respectively) and corre-
sponding carbons at ꢀ 106.5, 104.0, 100.4 and 96.3,
respectively (Tables 1 and 2). Acid hydrolysis of 1
afforded an aglycone, identified as drevogenin D (4)
Table 1
13C NMR chemical shifts of 1–5 in pyridine-d5
a
Carbon
1
2
3
4
5
1
2
3
Aglycone part
1.
Sugar moiety
Digitoxose:
39.8
30.6
77.8
39.4
39.8
30.6
77.8
40.0
40.0
30.7
77.9
40.1
40.2
33.0
70.6
44.2
40.1
32.8
70.8
44.1
C-1
C-2
96.3
37.3
67.8
83.4
69.0
18.6
2.
3.
C-3
C-4
4.
5.
140.7
122.3
28.3
38.2
49.9
39.5
71.6
80.5
54.1
84.3
34.1
27.1
54.7
11.5
19.0
70.5
23.7
140.7
122.3
28.3
38.2
50.0
39.5
71.6
80.5
54.1
84.3
34.1
27.1
54.7
11.6
19.0
70.5
23.7
140.7
122.4
28.4
37.5
49.9
39.5
71.9
78.5
55.7
84.9
35.3
24.5
58.8
11.0
19.1
216.7
32.6
141.7
121.8
28.4
38.5
50.2
39.6
71.8
80.7
54.2
84.5
34.3
27.3
55.0
11.7
19.3
71.8
23.8
141.2
121.9
28.2
38.5
49.9
39.5
71.4
78.2
56.0
85.0
34.9
24.7
58.6
10.9
19.2
216.2
32.5
C-5
C-6
6.
7.
Cymarose:
Cymarose:
Allose:
C-1
C-2
96.3
37.3
78.0
83.2
69.0
18.6
59.0
100.4
39.0
78.1
83.5
69.3
18.6
58.8
96.4
37.3
78.2
83.5
69.2
18.7
59.2
8.
9.
C-3
C-4
10.
11.
12.
13.
14.
15
16.
17.
18.
19.
20.
21.
C-5
C-6
ÀOMe
C-10
C-20
C-30
C-40
C-50
C-60
–OMe0
C-1
100.4
37.1
78.1
83.4
69.2
18.5
58.9
104.0
72.5
83.0
83.0
69.3
18.3
61.8
106.5
75.5
78.4
71.9
100.5
37.5
78.3
83.5
69.4
18.4
59.0
104.2
72.7
83.4
83.4
69.4
18.7
61.9
106.7
75.6
78.5
72.1
103.6
72.3
83.0
83.0
68.8
18.3
61.8
106.5
75.5
78.4
71.9
C-2
C-3
C-4
C-5
C-6
–OMe0
C-1
Glucose:
C-2
C-3
C-4
C-5
78.4
78.0
78.4
C-6
63.0
63.0
63.2
aAssignments based upon COSY, TOCSY, HETCOR, NOESY, DEPT and HMBC.

N.P. Sahu et al. / Phytochemistry 61 (2002) 383–388
385
Table 2
1H NMR chemical shifts for the sugar unitsa
Sugar units
1
2
1
2
Digitoxose
H-1
H-2
Allose
5.28 dd (1.7, 9.6)
1.88 m
H-1
H-2
5.08 d (7.8)
3.80 dd like
5.14 d (7.8)
3.76 m
2.29 dd like
4.63
H-3
H-4
H-5
H-6
H-3
H-4
H-5
H-6
OMe
4.45 t (2.8)
4.43 t (2.75)
3.68 dd (2.5, 9.8)
4.27 m
3.48 dd (2.5, 9.4)
4.20 m
1.33 d (6.1)
3.72 dd (2.5, 9.9)
4.26 dd (6.0, 9.9)
1.63 d (6.1)
3.84 s
1.58 d (6.2)
3.84 s
Cymarose
H-1
H-2
Glucose
H-1
H-2
5.28 dd (1.6, 9.6)
2.29
1.89 m
5.31 dd (1.6, 9.7)
2.40 dd like
1.96 m
4.98 d (7.8)
4.03 m
4.97 d (7.8)
4.03 m
4.26 m
H-3
H-4
4.26 t (9.0)
4.20 m
H-3
H-4
4.03 m
3.47 dd (2.5, 9.9)
4.21 m
4.05 m
3.48 dd (2.5, 9.4)
4.28 m
4.20 dd (6.6, 9.4)
H-5
H-6
H-5
H-6
4.0 m
4.38 dd (5.2, 11.4)
4.54 dd (2.1, 11.4)
3.99 m
4.36 m
4.54 d
1.34 d (6.1)
3.61 s
1.49 d (6.2)
3.6 s
OCH3 (11.5)
Cymarose
H-1
H-2
5.09 dd (1.7, 9.4)
2.29
1.81
H-3
H-4
4.03 m
3.45 dd (2.5, 9.9)
4.15 m
H-5
H-6
1.45 d (6.0)
3.60 s
OCH3
aAssignments based upon COSY, TOCSY, HETCOR, DEPT, NOESY and HMBC experiments. Coupling constants (in Hz) are given in parentheses.
The remaining spin-system displayed five ring
methines and a terminal methyl group. Starting from
the anomeric proton, all of the protons belonging to this
spin system were delineated (Table 2) using COSY and
TOCSY. The large coupling constants between H-1 and
H-2 (7.8 Hz) and H-4 and H-5 (9.9 Hz) indicated a
trans-diaxial relationship between these protons. A
coupling constant of 2.8 Hz between H-2 and H-3 indi-
cated a gauche disposition between these two protons.
The same relationship was also true for H-3 and H-4
(2.5 Hz). NOESY showed significant through-space
interaction between H-1 and H-5, as well as H-2 and H-
4. As in cymarose, a methoxy group was present at C-3
of B as deduced from the long range HMBC corre-
lations. The above information suggested that the sys-
tem B was 6-deoxy-3-O-methyl-b-allopyranose. The
identity of the sugar was further confirmed by compar-
ing its 13C NMR chemical shifts with those reported in
the literature (Yoshimura et al., 1983). All of the
monosaccharides were in a b-configuration as inferred
from the J values of the respective anomeric protons.
The determination of the inter-sugar linkages was
accomplished from the following HMBC correlations:
H-1 of spin system A (glucose) with C-4 of B (6-deoxy-
3-O-methyl-b-d-allopyranose); H-1 of B with C-4 of C
(cymarose); and H-1 of C with C-4 of D (cymarose).
The absolute configurations of the monosaccharides
were not determined, but are suggested in keeping with
those most commonly encountered among plant steroid
glycosides. The attachment of the tetrasaccharide moi-
ety to C-3 of the aglycone was deduced from the long-
range correlation shown between H-1 of D with C-3 of
the aglycone. In addition, a 13C NMR spectral com-
parison of 1 with its aglycone 4 revealed a glycosylation
shift (Kasai et al., 1977; Seo et al., 1978) in the reso-
nances of C-2 (À2.4 ppm), C-3 (+7.2), and C-4 (À4.8)
of the aglycone moiety. These data further supported
that the sugar moiety was located only at the C-3 posi-
tion of the aglycone. Support was also inferred from a
phase-sensitive NOESY experiment. Thus H-1 (ꢀ 4.98)
of the terminal glucose (A) was correlated with H-4 (ꢀ
3.72) of 6-deoxy-3-O-methyl-b-d-allopyranosyl (B), H-1
(ꢀ 5.08) of B with H-4 (ꢀ 3.45) of the inner cymarose (C),
H-1 (ꢀ 5.09) of C with H-4 (ꢀ 3.47) of the second cym-
arose (D), whose anomeric proton (d 5.28) showed
correlation with H-3 (ꢀ 3.89) of the aglycone. From the
foregoing evidence, the structure of volubiloside A (1)
was elucidated as drevogenin d-3-O-b-d-glucopyranosyl
(1!4)-6-deoxy-3-O-methyl-b-d-allopyranosyl-(1!4)-
b-d-cymaropyranosyl-(1!4)-b-d-cymaropyranoside.
Volubiloside B (2) showed a [M+Na]+ ion peak at
m/z 985 in the MALDI-TOF MS suggesting a molecular

386
N.P. Sahu et al. / Phytochemistry 61 (2002) 383–388
weight of 962, 14 mass units less than that of 1. Com-
bined with the results of an elemental analysis and the
13C NMR spectrum, the molecular formula of 2 was
deduced to be C47H78O20. Comparison of the 13C NMR
spectrum of 2 with that of 1 indicated that the aglycone
was identical with that of volubiloside A (1), but that
the compounds differed in the carbohydrate moiety. On
acid hydrolysis, 2 furnished drevogenin D (4) as the
aglycone, and the four monosaccharides were identified
as digitoxose, cymarose, glucose and 6-deoxy-3-O-
methyl allose. The b-linkages of the sugars of 2 were
indicated from the coupling constants of the anomeric
proton signals at ꢀ 5.28 (dd, J=1.7, 9.6 Hz, 1-H of
digitoxose), 5.31 (dd, J=1.6, 9.7 Hz, 1-H of cymarose),
5.14 (d, J=7.8 Hz, 1-H of 6-deoxy-3-O-methyl allose),
and 4.97 (d, J=7.8 Hz, 1-H of glucose). Inter-sugar and
sugar-aglycone linkages were deduced from the HMBC
and NOESY spectra. HMBC correlations were
observed between the following carbons and protons in
the oligosaccharide moieties of 2. Thus, H-1 of glucose
correlated with C-4 of 6-deoxy-3-O-methyl allose, H-1
of 6-deoxy-3-O-methyl allose with C-4 of cymarose, and
H-1 of cymarose with C-4 of digitoxose. The HMBC
relationship between C-3 (d 77.8) of the aglycone and
H-1 of digitoxose and a glycosylation shift (ꢀ+7.2 ppm)
indicated that the sugar moiety was linked to C-3 of the
aglycone. Thus the structure of volubiloside B (2) was
established as drevogenin d-3-O-b-d-glucopyranosyl
(1!4)-6-deoxy-3-O-methyl-b-d-allopyranosyl-(1!4)-
b-d-cymaropyranosyl-(1!4)-b-d-digitoxopyranoside.
Volubiloside C (3) showed a peak at m/z 997
[M+Na]+ in its MALDI-TOF MS two mass units less
than 1. In combination with the information from ele-
mental analysis and DEPT spectrum it was concluded
that the molecular formula of 3 was C48H78O20. The IR
spectrum of the compound displayed an absorption at
1690 cmÀ1 indicating the presence of a carbonyl group.
Comparison of the 13C NMR signals of 3 with 1
revealed that the sugar moiety at C-3 was identical,
while the aglycone moiety was different. Acid hydrolysis
of 3 furnished an aglycone, identified as drevogenin P
(5) from its physical data (Sauer et al., 1966) and com-
parison with an authentic sample. Thus the structure of
volubiloside C (3) was determined to be drevogenin P-3-
O-b-d-glucopyranosyl(1!4)-6-deoxy-3-O-methyl-b-d-
allopyranosyl - (1!4) - b - d - cymaropyranosyl(1!4) -
b-d-cymaropyranoside.
1985) are mainly in the sapogenin part. In the Indian
variety the sapogenin constituents are drevogenins D
and P while in that of Thailand the sapogenin con-
stituents are drevogenin A, dervyssogenin K2, marsecto-
hexol, and derbyssogenin G, and the similarities are more
or less the same in the carbohydrate moiety. Moreover,
flavonol constituents are found only in the Indian variety.
3. Experimental
3.1. General procedures
All melting points were measured on a Yanagimoto
1
micromelting point apparatus and are uncorrected. H
and 13C NMR spectra were recorded at 500 MHz and 125
MHz respectively using a Jeol ECP-500 spectrometer in
C5D5N with TMS as internal standard. MALDI-TOF
MS (positive) were performed on a Perspective Biosystem
Voyager DE-STR spectrometer with 2,5-dihydroxy-
benzoic acid as matrix. Paper chromatography was per-
formed on Whatman paper No. 1 (46ꢀ57 cm) with
solvent system BuOH–C5H5N–H2O (6:4:3); a saturated
solution of aniline oxalate in water was used as staining
agent and the spots were visualized after heating at 100 ꢁC.
3.2. Plant material
The plant material was collected from the suburbs of
Kolkata, India and identified by Dr. (Ms.) Debjani Basu,
Botanist, at Indian Botanic Garden, Howrah, West Ben-
gal, India. A voucher specimen (No. 305) was deposited
at the Steroids and Terpenoids Chemistry Department,
Indian Institute of Chemical Biology, Kolkata.
3.3. Extraction and isolation
The defatted, air-dried, powdered flowers (2.5 kg) of
D. volubilis were successively extracted with MeOH
(3ꢀ5 l) at ambient temperature. The combined MeOH
extract was concentrated (500 ml) under reduced pres-
sure and extracted with water-saturated n-BuOH (2ꢀ1
l). The organic layer was evaporated to dryness under
reduced pressure to give a residue (15.2 g). This was
chromatographed on silica gel (450 g). Graded elution
was carried out with chloroform followed by various
mixtures of CHCl3–MeOH (9:1, 17:3, and 4:1). A total
of 50 fractions (each 250 ml) were collected and frac-
tions giving similar spots on TLC were combined.
Fractions eluted with CHCl3–MeOH (9:1) were com-
bined together and subjected to rechromatography over
silica gel (15 g). Earlier fractions (collected in 30 ml lots)
eluted with CHCl3–MeOH mixture (93:7) eluted volu-
biloside A (150 mg) while later fractions eluted a mix-
ture of volubiloside B and volubiloside C. Repeated
fractional crystallization furnished volubiloside B (90
Repeated chromatographic purification furnished
conduritol A, quercetin, and quercetin-3-O-rutinoside
which were characterized from their physical and spec-
troscopic data in comparison with those reported (Pol-
lock and Stevens, 1965; Harborne and Mabry, 1985) for
authentic samples.
It is noteworthy to mention that the differences
between the constituents of the Indian variety and the
plant growing in Thailand (Yoshimura et al., 1983,

N.P. Sahu et al. / Phytochemistry 61 (2002) 383–388
387
mg). The mother liquor was chromatographed repeat-
edly over silica gel and eluted with various mixtures of
CHCl3–MeOH. Later fractions eluted with CHCl3–
MeOH (92:8) furnished 45 mg of volubiloside C. Frac-
tions eluted with CHCl3–MeOH (17:3) (2.25 g) was
rechromatographed over a column of silica gel (75 gm).
Earlier fractions eluted with CHCl3–MeOH (88:12)
yielded conduritol A (180 mg) whereas later fractions
furnished quercetin (120 mg), and fractions eluted with
CHCl3–MeOH (85:15) gave quercetin-3-O-rutinoside
(60 mg) identified by comparison of their physical and
spectral data with those reported in the literature (Pol-
lock and Stevens, 1965; Harborne and Mabry, 1985).
9.4 Hz, H-1 of cymarose); (13C NMR: Table 1). (Found:
C, 58.89; H, 8. 32; C48H78O20 requires: C, 59.12; H,
8.06%).
3.7. Acid hydrolysis of 1–3
A sample of 1, 2, or 3 (30 mg) was heated in 1 M HCl
ꢁ
(3 ml, dioxane–water 1:1) at 75 C for 1.5 h on an oil
bath, cooled, and 3 ml water was added. Dioxane was
distilled off under reduced pressure and the solution was
extracted with EtOAc (5 mlꢀ3). The EtOAc layer was
washed with water (3 mlꢀ4), dried and the residue was
crystallized from methanol–ether to furnish drevogenin
D, mp 223–225 ꢁC, [a]D25 À7.8ꢁ (c 0.14, MeOH) for 1 and
2 (Found: C, 68.69; H, 9.41; calc. for C21H34O5:ꢁC,
68.82; H, 9.35%); and drevogenin P, mp 208–210 C,
[a]2D5 À32.8ꢁ (c 0.18, MeOH) for 3. (Found: C, 69.34; H,
8.94; calc. for C21H32O5: C, 69.20; H, 8.85%). The acid
hydrolyzate was worked up as described by Mahato et
al. (1989). The monosaccharides were identified as glu-
cose and cymarose for 1; glucose, cymarose, and digi-
toxose for 2; and, glucose and cymarose for 3 by paper
chromatography on comparison with authentic sam-
ples. The monosaccharide 6-deoxy-3-O-methyl-b-allose
for 1–3 was confirmed from extensive NMR studies
(vide results and discussion) and comparison of its 13C
NMR data with those reported in the literature (Yoshi-
mura et al., 1983).
3.4. Volubiloside A (1)
Colourless needles from MeOH, mp 181–182 ꢁC
(dec.), [a]D25 À16.7ꢁ (c 0.2, MeOH); IR: ꢁmax cmÀ1 (KBr):
3413, 1645, 1373, 1162, 1079 cmÀ1; MALDI-TOF-MS
1
(positive): m/z 999 [M+Na]+; H NMR: ꢀ 1.33 (3H, s,
19-CH3), 1.49 (3H, d, J=6.6 Hz, 21-CH3), 1.72 (3H, s,
18-CH3), 2.65 (1H, m, 17a-H), 3.55 (1H, d, J=9.7 Hz,
12a-H), 3.89 (1H, m, 3a-H), 4.15 [1H, m (overlapped
with other signals), 11b-H] and 5.53 (1H, d, J=5.7 Hz,
6-H). (1H and 13C NMR: Tables 1 and 2). (Found: C,
58.69; H, 8.32; C48H80O20 requires: C, 59.00; H,
8.25%).
3.5. Volubiloside B (2)
The compound crystallized from MeOH–CH3CN in
needles, mp 178–179 ꢁC (dec.), [a]2D5 À17.6ꢁ (c 0.2,
MeOH); IR: ꢁmax cmÀ1 (KBr): 3424, 1646, 1375, 1165,
1080 cmÀ1; MALDI-TOF-MS (positive): m/z 985
Acknowledgements
We thank Dr. Debjani Basu, Scientist, Botanical Sur-
vey of India, Howrah for identification of the plant
material and Shri Rajendra Mahato, Helper of this
Department for collection of the plant materials.
1
[M+Na]+; H NMR: ꢀ 1.33 (3H, s, 19-CH3), 1.49 (3H,
d, J=6.2 Hz, 21-CH3), 1.72 (3H, s, 18-CH3), 2.65 (1H,
m, 17a-H), 3.55 (1H, d, J=9.4 Hz, 12a-H), 3.89 (1H, m,
3a-H), 4.15 [1H, m (overlapped with other signals),
11b-H] and 5.53 (1H, d, J=5.7 Hz, 6-H). (1H and 13C
NMR: Tables 1 and 2). (Found: C, 58.52; H, 8.26;
C47H78O20 requires: C, 58.61; H, 8.16%).
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The isolate crystallized from MeOH–CH3CN in fine
25
ꢁ
micro needles, mp 218–220 C (dec.), [a]D +23.8ꢁ (c
0.14, MeOH); IR: ꢁmax cmÀ1 (KBr): 3414, 1690, 1370,
1164, 1080 cmÀ1; MALDI-TOF-MS (positive): m/z 997
1
[M+Na]+; H NMR: ꢀ 1.26 (3H, s, 18-CH3), 1.33 (3H,
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