Synthesis of OSW-1 analogs with modified side chains and their antitumor activities

Article abstract of DOI:10.1016/j.bmcl.2004.03.081

Four analogs of OSW-1 (1-4) with modified side chains on the steroidal skeleton were synthesized following modification of our previous route for the total synthesis of OSW-1. Testing of the analogs against growth of tumor cells demonstrated that the 22-one function and the full length of the side chain of OSW-1 were not required for the antitumor action of OSW-1.

Full text of DOI:10.1016/j.bmcl.2004.03.081

Bioorganic & Medicinal Chemistry Letters 14 (2004) 2781–2785
Synthesis of OSW-1 analogs with modified side chains and their
antitumor activities
Lehua Deng,a Hao Wu,b Biao Yu,a,* Manrong Jiangb and Jiarui Wub
aState Key Laboratory of Bio-organic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, Shanghai 200032, China
bInstitute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences,
Shanghai 200031, China
Received 1 March 2004; accepted 22 March 2004
Abstract—Four analogs of OSW-1 (1–4) with modified side chains on the steroidal skeleton were synthesized following modification
of our previous route for the total synthesis of OSW-1. Testing of the analogs against growth of tumor cells demonstrated that the
22-one function and the full length of the side chain of OSW-1 were not required for the antitumor action of OSW-1.
ꢀ 2004 Elsevier Ltd. All rights reserved.
Since 1992, a small family of cholestane saponins fea-
turing a novel 3b,16b,17a-trihydroxycholest-5-en-22-
one aglycone with a sugar residue at the 16-OH has been
disclosed, by the group of Sashida and co-workers, from
the bulbs of Ornithogalum saudersiae and taxonomically
related plants of the lily family.1;2 Those saponins have
attracted a great attention due to their potent antitumor
activities.2 As the major and representative member,
OSW-1 was tested against the NCI (the US National
Cancer Institute) 60 cell lines, showing 10–100 times
more potency compared to those of the clinically applied
anticancer agents, for example, cisplatin, as positive
controls.2a Comparing the structure–activity relation-
ship (SAR) of OSW-1 and its natural congeners,
requirement of the 16-O-disaccharide moiety of OSW-1
for its significant cytotoxic activity was clearly revealed;
those with modified sugar residue showed much less
activities.2 Especially, removal of the acetyl (Ac) and the
4-methoxybenzoyl (MBz) groups on the disaccharide
moiety diminished the cytotoxicity by three order of
magnitude.2 Substitution with a glucose on the 3-OH, a
site remote to the 16-O-disaccharide, did not affect
apparently the cytotoxic activity.2 However, synthetic
glycosides bearing the acyl disaccharide but disparate
steroid aglycones of OSW-1 did not show any cytotox-
icity.3 Inversion of the C-16 configuration, where the
disaccharide is attached, was also not allowed to retain
the significant cytotoxic activity of OSW-1.4 Consider-
ing the similarity of the cytotoxicity profile and molec-
ular structure of the OSW-1 aglycone with that of the
cephalostatins, a related mechanism of action involving
formation of C22-oxocarbenium ions was suggested.5
To examine the importance of the side chain, especially
of the 22-one function, we synthesized OSW-1 analogs
1–4 (Fig. 1) with modified side chains on the steroidal
skeleton and tested their antitumor activities.
Three routes toward the total synthesis of OSW-1 have
been developed, with the major differences being in the
preparation of the aglycone.6–9 Adopting modification
of our own procedure,6 we synthesized the desired
R
OH
O
O
17
16
O
O
O
OH
O
3
HO
O
O
HO
O
HO
R = -C(=O)CH2CH2CH(CH3)2 (OSW-1)
-CH2CH2CH2CH(CH3)2 (1)
-CH(OH)CH2CH2CH(CH3)2 (2)
-CH(=O)CH2CH2CH3 (3)
-CH(=O)CH3 (4)
Keywords: OSW-1; Analogs; Side chain; Synthesis; Antitumor.
* Corresponding author. E-mail: byu@mail.sioc.ac.cn
Figure 1. OSW-1 and its analogs (1–4) with modified side chains.
0960-894X/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2004.03.081

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L. Deng et al. / Bioorg. Med. Chem. Lett. 14 (2004) 2781–2785
OH
O
a, b
TBSO
c
TBSO
HO
7
6
5
OR
O
H
g
e
d
TBSO
TBSO
TBSO
9 R = H
8
f
10 R= Ts
OH
OH
h
TBSO
11
12
1
OH
OH
i, j
k, l
TBSO
13
+
OTES
O
O
O
CCl3
TESO
TESO
O
OAc
NH
OMBz
14
Scheme 1. Synthesis of the 22-deoxy-OSW-1 (1). Reagents and conditions: (a) Ph3PþEtBrÀ, t-BuOK, THF, reflux, 88%; (b) TBSCl, imidazole, DMF,
rt, 97%; (c) (CH2O)n, BF3ÆEt2O, CH2Cl2, rt, 73%; (d) Dess–Martin periodinane, CH2Cl2, rt, 94%; (e) 3-methylbutyl magnesium bromide, Et2O, rt,
77%; (f) TsCl, pyridine, 0 ꢁC to rt; (g) LiAlH4, THF, reflux, 45% (two steps); (h) OsO4, pyridine–THF, )35 ꢁC to rt; then H2S (gas), 51%; (i) Swern
ꢀ
oxidation, 79%; (j) NaBH4, CeCl3Æ7H2O, THF, 0 ꢁC, 52%; (k) 14, TMSOTf (0.05 equiv), 4 A MS, CH2Cl2, )40 ꢁC, 58%; (l) Pd(CN)2Cl2, acetone–
water (v/v, 20:1), rt, 51%.
OSW-1 analogs 1–4 (Schemes 1–3). Depicted in Scheme
1 is the preparation of compound 1, an OSW-1 analog
with the 22-one being reduced into CH2. Starting from
5-androsten-3b-ol-17-one 5, a similar sequence as that
employed in the OSW-1 synthesis was followed to
introduce the C-17 side to provide 22-ol 9, that is, Wittig
reaction, protection of the 3-OH with TBS ether, Prins
reaction, oxidation of the resulting 22-OH into 22-
aldehyde, followed by a Grignard addition. A difference
from the previous synthesis is the use of TBS protection
(instead of TBDPS protection) on the 3-OH, which
tolerated the Prins reaction (6 fi 7) under controlled
conditions. Removal of the 22-OH (on 9) was achieved
via reduction of its tosylate 10 with LiAlH4, albeit in a
moderate yield (45% for two steps). Again, a similar
sequence as that employed in the OSW-1 synthesis was
used to convert diene 11 into 16b,17a-diol 13, that is,
selective dihydroxylation of the 16,17-ene with OsO4
(1.0 equiv), Swern oxidation of the 16a-OH, and
reduction of the resulting 16-one. Guo and Fuchs have
found that the yields for the dihydroxylation of the
16,17-ene and the stereoselectivity for the reduction of
the 16-one were highly dependent on the substitution on
the C-22.9 Fortunately, treatment of 11 with OsO4
(1.0 equiv) provided the 16a,17a-diol 12 in a satisfactory
51% yield; and reduction of the 16-one with NaBH4/
CeCl3 gave the desired 16b-ol 13 as a major product
(52%), with the 16a isomer (12) being obtained in 18%
yield. The final coupling and deprotection procedures
were also borrowed from those in the OSW-1 synthesis.
Thus, coupling of diol 13 with disaccharide trichloro-
acetimidate 14 provided the corresponding glycoside in
58% yield, which was subjected to deprotection of the
silyl groups with Pd(CN)2Cl2,10 affording the desired
compound 1 in 51% yield.
OR
OTBS
OH
OH
b
TBSO
TBSO
OTBS
9 R = H
16
a
15 R = TBS
c, d
e, f
14
OH
OH
2
17
TBSO
Scheme 2. Synthesis of the 22-hydroxy-OSW-1 (2). Reagents and
conditions: (a) TBSCl, imidazole, DMF, rt, 97%; (b) OsO4, pyridine–
ꢀ
THF, )35 ꢁC to rt; then H2S (gas), 78%; (c) TPAP, NMO, 4 A MS,
CH2Cl2, rt, 95%; (d) NaBH4, CeCl3Æ7H2O, THF, 0 ꢁC, 64%; (e) 14,
TMSOTf (0.05 equiv), 4 A MS, CH2Cl2, )40 ꢁC, 70%; (f) Pd(CN)2Cl2,
acetone–water (v/v, 20:1), rt, 71%.
ꢀ
The desired 22-OH analog of OSW-1 (2) was synthe-
sized from 22a-ol 9, which was the only stereoisomer

L. Deng et al. / Bioorg. Med. Chem. Lett. 14 (2004) 2781–2785
2783
OH
O
R
H
b, c
a
19 R = n-propyl
20 R = methyl
TBDPSO
TBDPSO
TBDPSO
18
O
O
R
O
O
R
f
d, e
TBSO
23 R = n-propyl
24 R = methyl
21 R = n-propyl
22 R = methyl
O
O
O
O
R
R
OH
OH
OH
OH
g, h
TBSO
TBSO
25 R = n-propyl
26 R = methyl
27 R = n-propyl
28 R = methyl
i, j
3 and 4
14
Scheme 3. Synthesis of the OSW-1 analogs with shorter side chains (3 and 4). Reagents and conditions: (a) n-propyl (or methyl) magnesium bromide,
ꢀ
Et2O, 0 ꢁC, 84% (for 19); 83% (for 20); (b) PDC, 4 A MS, CH2Cl2–DMF, rt, 79% (for oxidation of 19); 75% (for oxidation of 20); (c)
HOCH2CH2OH, CH(OEt)3, p-TsOHÆH2O, rt, 86% (for 21); 98% (for 22); (d) TBAF, THF, rt; (e) TBSCl, imidazole, DMF, rt, 62% (for 23, two
ꢀ
steps); 90% (for 24, two steps); (f) OsO4, pyridine–THF, )40 ꢁC to rt; then H2S (gas), 34% (for 25); 38% (for 26); (g) TPAP, NMO, 4 A MS, CH2Cl2,
rt, 72% (for substrate 25); 97% (for substrate 26); (h) NaBH4, CeCl3Æ7H2O, THF, 0 ꢁC, 54% (for 27); 53% (for 28); (i) 14, TMSOTf (0.05 equiv),
ꢀ
4 A MS, CH2Cl2, )40 ꢁC, 75% (for glycosylation of 27); 74% (for glycosylation of 28); (j) Pd(CN)2Cl2, acetone–water (v/v, 20:1), rt, 53% (for 3); 51%
(for 4).
being isolated in the Grignard addition (8 fi 9)6 (Scheme
2). Protection of the 22-OH on 9 with TBS ether gave
diene 15. Then, a similar route for the preparation of 1
from 11 (Scheme 1) was adopted for conversion of 15 to
2. Dihydroxylation of 15 with OsO4 (1.0 equiv) gave
16a,17a-diol 16 in a better yield (78%) compared to that
for 11 fi 12. Reduction of the corresponding 16-one
with NaBH4/CeCl3 afforded the desired 16b-ol product
17 in 64% yield, with the 16a isomer (16) being isolated
in 29% yield. A modification in the synthesis is the use of
TPAP/NMO11 for oxidation of the 16a-OH (of diol 16),
which was more convenient to perform than the previ-
ous Swern oxidation and gave excellent yield of the
16-one (95%).
Then, similar transformations as those used in the
OSW-1 synthesis were followed to furnish analogs 3 and
4. The use of TPAP/NMO for oxidation of the 16a-OH
(of diols 25 and 26) avoided the cleavage of the
22-ethylene glycol ketal, which occurred in the previous
Swern oxidation conditions in the OSW-1 synthesis. In
the reduction of the resulting 16-ones with NaBH4/
CeCl3, the desired 16b-ols (27 and 28) were obtained in
54% and 53% yields, respectively, with considerable
amount of the 16a isomers (25 and 26) being recovered
(29% and 18%, respectively).
The in vitro antitumor activities of the synthetic OSW-1
and its analogs 1–4 against AGS (stomach cancer cells),
7404 (liver carcinoma cells), and MCF-7 (breast cancer
cells) were evaluated by the standard MTT assay12 using
cisplatin as a positive control. The results are listed in
Table 1. The IC50 values of cisplatin against these three
cell lines used in our assays are consistent with those
determined by others.13–15 OSW-1 showed 70–170 times
OSW-1 analogs with shorter side chains on the steroidal
skeleton (3 and 4) were prepared starting from aldehyde
18, an intermediate in the OSW-1 synthesis6 (Scheme 3).
Grignard addition of 18 with n-propyl or methyl mag-
nesium bromide provided 22-ol 19 or 20 in good yield.
Table 1. Cytotoxic activities of OSW-1, its analogs 1–4,16 and cisplatin against tumor cellsa
Tumor cellsb
IC50 (lM)
1
2
3
4
OSW-1
Cisplatin
AGS
7404
MCF-7
1.38
0.063
0.060
7.26
1.86
1.79
1.92
0.032
0.020
6.98
1.42
0.10
0.27
24.1
8.37
18.7
2.90
6.61
a The standard MTT assay was followed.12
b AGS: human stomach cancer cell line; 7404: human liver carcinoma cell line; MCF-7: human breast cancer cell line.

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L. Deng et al. / Bioorg. Med. Chem. Lett. 14 (2004) 2781–2785
9. For the first synthesis of the aglycone of OSW-1, see: Guo,
C.; Fuchs, P. L. Tetrahedron Lett. 1998, 39, 1099.
10. Lipshutz, B. H.; Pollart, D.; Monforte, J.; Kotsuki, H.
Tetrahedron Lett. 1985, 26, 705.
11. Paquette, L. A.; Wang, H.; Su, Z.; Zhao, M. J. Am. Chem.
Soc. 1998, 121, 5213.
12. Kuroda, M.; Mimaki, Y.; Sashida, Y.; Hirano, T.; Oka,
K.; Dobashi, A.; Li, H.; Harada, N. Tetrahedron 1997, 53,
11549.
13. Shen, D.; Akiyama, S.; Schoenlein, P.; Pastan, P.;
Gottesman, M. Br. J. Cancer 1995, 71, 676.
14. Kim, Y.; Song, R.; Chung, H.; Jun, M.; Sohn, Y. J. Inorg.
Biochem. 2004, 78, 78.
higher potency than cisplatin. Surprisingly, analog 1,
with the 22-one (of OSW-1) being saturated into a CH2,
thus formation of the putative C22-oxocarbenium is
impossible, was slightly more potent than OSW-1
against the tested three cancer cell lines. While the 22-
OH analog 2 was less potent by 30-fold (for 7407 and
MCF-7) than 1. The full length of the cholestane side
chain was also not essential to the antitumor activity;
congener 3, with the two terminal methyl groups (of
OSW-1) being removed, was slightly more potent than
OSW-1. However, the shorter congener 4, with the ter-
minal iso-butyl group (of OSW-1) being removed, was
significantly less potent than OSW-1.
15. Kwon, Y.; Whang, K.; Park, Y.; Kim, K. Bioorg. Med.
Chem. 2003, 11, 1669.
25
D
16. Analytical data for compounds 1–4. Compound 1: ½aŠ
In summary, OSW-1 analogs (1–4) with modified side
chains on the steroidal skeleton were synthesized fol-
lowing modification of our previous procedure for the
total synthesis of OSW-1. Antitumor activity test of
these compounds demonstrated that the side chain of
OSW-1 tolerated certain modifications without affecting
apparently the significant antitumor potency of OSW-1.
Especially, the antitumor activity of OSW-1 was inde-
pendent of the 22-one function, which was previously
proposed to be crucial to the antitumor action of OSW-
1 saponins (and the cephalostatins).5
1
)17.2 (c 0.40, CH3OH); H NMR (300 MHz, C5D5N): d
8.28 (d, J ¼ 8:8 Hz, 2H), 7.04 (d, J ¼ 8:8 Hz, 2H), 6.54 (br
d, J ¼ 5:3 Hz, 1H), 6.21 (s, 1H), 6.15 (br s, 1H), 5.84 (t,
J ¼ 6:8 Hz, 1H), 5.67 (t-like, J ¼ 8:4, 7.8 Hz, 1H), 5.34 (br
d, J ¼ 3:9 Hz, 1H), 5.08 (d, J ¼ 8:0 Hz, 1H), 4.77 (s, 1H),
4.74 (d, J ¼ 7:1 Hz, 1H), 4.44 (br s, 1H), 3.70 (s, 3H), 2.57
(br d, J ¼ 6:6 Hz, 2H), 2.44 (m, 1H), 2.35 (q, J ¼ 6:9 Hz,
1H), 1.93 (s, 3H), 1.20 (d, J ¼ 6:8 Hz, 3H), 1.05 (s, 3H),
1.02 (s, 3H), 0.90 (d, J ¼ 6:5 Hz, 2H), 0.89 (d, J ¼ 6:3 Hz,
2H); 13C NMR (75 MHz, C5D5N): d 169.16, 165.51,
163.84, 141.97, 132.39, 121.22, 114.06, 103.51, 102.43,
87.95, 86.24, 80.70, 76.19, 75.11, 71.79, 71.32, 70.80, 68.49,
66.96, 66.19, 55.46, 50.48, 49.42, 47.11, 43.54, 40.49, 37.82,
36.91, 36.03, 35.67, 34.13, 33.25, 32.27, 28.26, 25.67, 23.07,
22.83, 21.02, 19.59, 14.33, 13.19; HRMS (MALDI) calcd
for C47H70O14Na (M+Naþ): 881.46654; found: 881.46578.
Acknowledgements
25
D
Compound 2: ½aŠ )13.6 (c 0.60, CH3OH); 1H NMR
(300 MHz, C5D5N): d 8.28 (dd, J ¼ 8:8, 1.4 Hz, 2H), 7.03
(dd, J ¼ 9:0, 1.4 Hz, 2H), 6.54 (br d, J ¼ 5:3 Hz, 1H), 6.21
(s, 1H), 6.25–6.05 (br s, 1H), 5.79 (t, J ¼ 7:9 Hz, 1H), 5.66
(t-like, J ¼ 7:6, 8.8 Hz, 1H), 5.34 (br d, J ¼ 3:9 Hz, 1H),
5.12 (d, J ¼ 7:7 Hz, 1H), 4.75 (d, J ¼ 6:5 Hz, 1H), 4.42 (br
s, 1H), 3.70 (s, 3H), 2.58 (br d, J ¼ 7:6 Hz, 2H), 2.45 (m,
1H), 2.35 (q, J ¼ 6:9 Hz, 1H), 1.92 (s, 3H), 1.33 (d,
J ¼ 7:0 Hz, 3H), 1.05 (br s, 6H), 0.95 (d, J ¼ 6:6 Hz, 3H),
0.89 (d, J ¼ 6:6 Hz, 3H); 13C NMR (75 MHz, C5D5N): d
169.13, 165.46, 163.84, 141.97, 132.36, 121.19, 114.06,
103.24, 102.02, 88.77, 88.24, 80.50, 76.02, 74.99, 74.49,
71.80, 71.29, 70.70, 68.28, 66.81, 66.07, 55.44, 50.45, 48.92,
47.00, 43.51, 38.08, 37.78, 36.90, 36.18, 35.55, 34.07, 33.33,
32.60, 32.25, 28.64, 23.05, 22.86, 20.90, 19.59, 13.21, 8.50;
This work is supported by the National Natural Science
Foundation of China (20372070, 20321202, and
29925203) and the Chinese Academy of Sciences
(KGCX2-SW-209).
References and notes
1. Kubo, S.; Mimaki, Y.; Terao, M.; Sashida, Y.; Nikaido,
T.; Ohmoto, T. Phytochemistry 1992, 31, 3969.
2. (a) Mimaki, Y.; Kuroda, M.; Kameyama, A.; Sashida, Y.;
Hirano, T.; Oka, K.; Maekawa, R.; Wada, T.; Sugita, K.;
Beutler, J. A. Bioorg. Med. Chem. Lett. 1997, 7, 633; (b)
Kuroda, M.; Mimaki, Y.; Yokosuka, A.; Sashida, Y.;
Beutler, J. A. J. Nat. Prod. 2001, 64, 88; (c) Kuroda, M.;
Mimaki, Y.; Yokosuka, A.; Sashida, Y. Chem. Pharm.
Bull. 2001, 49, 1042; (d) Kuroda, M.; Mimaki, Y.;
Yokosuka, A.; Hasegawa, F.; Sashida, Y. J. Nat. Prod.
2002, 65, 1417.
3. (a) Ma, X.; Yu, B.; Hui, Y.; Xiao, D.; Ding, J. Carbohydr.
Res. 2000, 329, 495; (b) Ma, X.; Yu, B.; Hui, Y.; Miao, Z.;
Ding, J. Carbohydr. Res. 2001, 334, 159.
4. Ma, X.; Yu, B.; Hui, Y.; Miao, Z.; Ding, J. Bioorg. Med.
Chem. Lett. 2001, 11, 2153.
5. Guo, C.; LaCour, T. G.; Fuchs, P. L. Bioorg. Med. Chem.
Lett. 1999, 9, 419.
6. Deng, S.; Yu, B.; Lou, Y.; Hui, Y. J. Org. Chem. 1999, 64,
202.
7. (a) Yu, W.; Jin, Z. J. Am. Chem. Soc. 2001, 123, 3369; (b)
Yu, W.; Jin, Z. J. Am. Chem. Soc. 2002, 124, 6576.
8. (a) Morzycki, J. W.; Gryszkiewicz, A.; Jastrzebska, I.
Tetrahedron Lett. 2000, 41, 3751; (b) Morzycki, J. W.;
Wojtkielewicz, A. Carbohydr. Res. 2002, 337, 1269.
HRMS (MALDI) calcd for C47H70O15Na (M+Naþ):
25
D
897.46125; found: 897.46070. Compound 3: ½aŠ )38.6 (c
1
0.25, CH3OH); H NMR (300 MHz, C5D5N): d 8.31 (d,
J ¼ 8:8 Hz, 2H), 7.06 (d, J ¼ 8:8 Hz, 2H), 5.66 (t,
J ¼ 8:1 Hz, 1H), 5.50 (t-like, J ¼ 7:1, 6.6 Hz, 1H), 5.36
(d, J ¼ 4:1 Hz, 1H), 5.09 (d, J ¼ 7:4 Hz, 1H), 4.76 (s, 1H),
4.55 (d, J ¼ 5:8 Hz, 1H), 4.35 (br s, 1H), 4.32–4.06 (m,
6H), 3.72 (s, 3H), 3.12 (q, J ¼ 7:2 Hz, 1H), 2.59 (d,
J ¼ 7:4 Hz, 2H), 1.93 (s, 3H), 1.23 (d, J ¼ 7:1 Hz, 3H),
1.05 (s, 3H), 0.97 (s, 3H), 0.81 (d, J ¼ 7:3 Hz, 3H); 13C
NMR (75 MHz, C5D5N): d 218.68, 169.28, 165.43, 163.91,
141.94, 132.43, 121.08, 114.16, 103.75, 100.78, 88.54,
85.74, 81.18, 76.40, 75.16, 72.05, 71.30, 70.73, 67.10,
65.22, 55.52, 50.19, 48.54, 46.52, 42.95, 37.79, 36.88, 34.65,
32.74, 32.25, 29.99, 20.82, 19.61, 17.04, 13.66, 11.73;
HRMS (MALDI) calcd for C45H64O15Na (M+Naþ):
25
D
867.41448; found: 867.41375. Compound 4: ½aŠ )30.0 (c
1
0.30, CH3OH); H NMR (300 MHz, C5D5N): d 8.29 (d,
J ¼ 8:5 Hz, 2H), 7.03 (d, J ¼ 8:5 Hz, 2H), 5.67 (t,
J ¼ 8:4 Hz, 1H), 5.59 (t-like, J ¼ 8:2, 6.9 Hz, 1H), 5.36
(d, J ¼ 4:4 Hz, 1H), 5.11 (d, J ¼ 7:7 Hz, 1H), 4.64 (s, 1H),
4.59 (d, J ¼ 6:6 Hz, 1H), 4.42 (br s, 1H), 4.35–4.10

L. Deng et al. / Bioorg. Med. Chem. Lett. 14 (2004) 2781–2785
2785
(m, 6H), 3.69 (s, 3H), 3.14 (q, J ¼ 7:4 Hz, 1H), 2.58 (d,
J ¼ 7:4 Hz, 2H), 2.07 (s, 3H), 1.92 (s, 3H), 1.18 (d,
J ¼ 7:1 Hz, 3H), 1.04 (s, 3H), 0.92 (s, 3H); 13C NMR
(75 MHz, C5D5N): d 216.82, 169.34, 165.51, 163.87,
141.95, 132.42, 121.04, 114.10, 103.61, 101.02, 89.12,
85.55, 81.27, 76.36, 75.19, 71.88, 71.30, 70.80, 68.19,
67.04, 65.93, 55.49, 50.13, 48.51, 46.47, 43.50, 37.76, 36.87,
33.94, 32.63, 32.25, 29.96, 28.88, 20.92, 19.58, 13.66, 11.67;
HRMS (MALDI) calcd for C43H60O15Na (M+Naþ):
839.38300; found: 839.38245.