Total synthesis as a resource in drug discovery: The first in vivo evaluation of panaxytriol and its derivatives

Article abstract of DOI:10.1021/jo0515475

We have conducted key preliminary studies into the in vitro and in vivo cytotoxicity of panaxytriol. Through total synthesis, we prepared and evaluated several synthetic panaxytriol analogues, each of which exhibited enhanced cytotoxicity relative to the

Full text of DOI:10.1021/jo0515475

Total Synthesis as a Resource in Drug Discovery: The First In
Vivo Evaluation of Panaxytriol and Its Derivatives
Heedong Yun,† Ting-Chao Chou,‡ Huajin Dong,‡ Yuan Tian,§ Yue-ming Li,§ and
Samuel J. Danishefsky*,†,
Department of Chemistry, Columbia University, 3000 Broadway, New York, New York, 10027 and
Laboratory for Bioorganic Chemistry, Preclinical Pharmacology Core Facility, and Laboratory of
Biochemistry and Pharmacology, Sloan-Kettering Institute for Cancer Research, 1275 York Avenue,
New York, New York 10021
s-danishefsky@ski.mskcc.org
Received July 25, 2005
We have conducted key preliminary studies into the in vitro and in vivo cytotoxicity of panaxytriol.
Through total synthesis, we prepared and evaluated several synthetic panaxytriol analogues, each
of which exhibited enhanced cytotoxicity relative to the natural product. Consequently, we have
begun to chart the first in vitro SAR map for the compound, which suggests that the C3 hydroxyl
functionality is not critical for biological activity and that, in fact, engagement of the C9-C10 diol
as an acetonide actually leads to notably enhanced cytotoxicity. Furthermore, through in vivo
investigations, we demonstrated that panaxytriol and panaxytriol acetonide (12) moderately
suppress tumor growth with little or no toxicity. Finally, preliminary in vitro evaluation of
panaxytriol indicates that it possesses neurotrophic activity.
Introduction
and panaxynol (3).5 Of these, we were particularly
interested in panaxytriol (1), which demonstrates in vitro
inhibitory activity against a range of tumor cells, includ-
ing human gastric carcinoma (MK-1),6 mouse lymphoma
(P388D1),7 and human breast carcinoma (Breast M25-
SF).8 In addition, in one in vivo investigation, panaxytriol
reportedly suppressed the growth of B16 melanoma cells
that had been transplanted into mice.9
Red ginseng, the steamed and dried root of Panax
ginseng C. A. Meyer, is widely used as folk medicine
throughout Asia. Numerous therapeutic benefits have
been ascribed to this popular dietary supplement, which
is commonly used for its purported analeptic, erythro-
poietic, and cytotoxic properties.1 The latter attribute, in
particular, has been corroborated through a number of
in vitro and in vivo biological studies of the red ginseng
extract. In addition, several components of red ginseng
have been isolated and evaluated for their antitumor
properties, including panaxytriol (1),2,3 panaxydol (2),4
† Columbia University.
‡ Preclinical Pharmacology Core Facility, Sloan-Kettering Institute
for Cancer Research.
§ Laboratory of Biochemistry and Pharmacology, Sloan-Kettering
Institute for Cancer Research.
Laboratory for Bioorganic Chemistry, Sloan-Kettering Institute
for Cancer Research.
(5) (a) Isolation: Bohlmann, F.; Niedballa, U.; Rode, K.-M. Chem.
Ber. 1966, 99, 3552. (b) For recent asymmetric synthesis, see ref 10h.
(6) (a) Matsunaga, H.; Katano, M.; Saita, T.; Yamamoto, H.; Mori,
M. Cancer Chemother. Pharmacol. 1994, 33, 291. (b) Saita, T.; Katano,
M.; Matsunaga, H.; Kouno, I.; Fujito, H.; Mori, M. Biol. Pharm. Bull.
1995, 18, 933.
(1) Saito, T.; Matsunaga, H.; Yamamoto, H.; Nagumo, F.; Fujito, H.;
Mori, M.; Katano, M. Biol. Pharm. Bull. 1994, 17, 798.
(2) Kitagawa, I.; Yoshikawa, M.; Yoshihara, M.; Hayashi, T.;
Taniyama, T. Yakugaku Zasshi 1983, 103, 612.
(3) Katagawa, I.; Taniyama, T.; Shibuya, H.; Noda, T.; Yoshikawa,
M. Yakugaku Zasshi 1987, 107, 495.
(4) (a) Isolation: Poplawski, J.; Wrobel, J. T.; Glinka, T. Phytochem-
istry 1980, 19, 1539. (b) See the recent asymmetric synthesis: Yu, H.-
J.; Sun, C.-M.; Chen, C.-C.; Wu, T.-C.; Wei, C.-L.; Shen, C.-C.
Heterocycles 2004, 62, 857.
(7) Kim, J. Y.; Lee, K. W.; Kim, S. H.; Wee, J. J.; Kim, Y. S.; Lee, H.
J. Planta Med. 2002, 68, 119.
(8) Matsunaga, H.; Saita, T.; Naguo, F.; Mori, M.; Katano, M. Cancer
Chemother. Pharmacol. 1995, 35, 291.
(9) Katano, M.; Yamamoto, H.; Matsunaga, H.; Mori, M.; Takata,
K.; Nakamura, M. Gan to Kagaku Ryoho 1990, 17, 1045.
10.1021/jo0515475 CCC: $30.25 © 2005 American Chemical Society
Published on Web 11/12/2005
J. Org. Chem. 2005, 70, 10375-10380
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Yun et al.
In launching our program toward the total synthesis
and biological evaluation of panaxytriol, we were mindful
of the unique attributes of this cytotoxic natural product.
It is, in fact, very rare to find a documented instance of
a tumor retardant isolated from a food product. Thus,
given the widespread availability of the source, red
ginseng, as well as the lack of toxicity that would be
expected from a food component, even a very moderate
cytotoxic effect would be considered to be particularly
noteworthy in the context of panaxytriol.
To date, a number of syntheses have been reported for
panaxytriol.10 We recently disclosed our own total syn-
thesis, which we hoped would allow access to significant
amounts of the natural product for extensive biological
investigations.10i We report, herein, the development of
a slightly modified route, which has allowed us to prepare
multigram quantities of synthetic panaxytriol. The syn-
thetic material was evaluated for its cytotoxic properties
in a number of in vitro and in vivo contexts. Using our
streamlined panaxytriol synthesis as a guide, we pre-
pared several synthetic analogues, whose activities were
compared to the natural product. With these results, we
have begun to chart an SAR map for panaxytriol.
Finally, we recently became aware of a disclosure from
the laboratory of Kurimoto et. al. on the in vitro neu-
rotrophic activity of the organic extracts of red ginseng.11
The authors did not attempt to identify the neurotrophi-
cally active components of the red ginseng extract;
however, with ample synthetic panaxytriol on hand, we
sought to determine whether this compound was a
contributor to the observed activity. This line of inves-
tigation is in keeping with a broad program in our
laboratory that is devoted to the total synthesis and
biological evaluation of nonpeptidyl small molecule neu-
rotrophic factors. We report the results of this prelimi-
nary investigation herein.
Modified Synthesis of Panaxytriol. As previously
reported,10i the defining transformation of our synthesis
of panaxytriol (1) is the Cadiot-Chodkiewicz coupling12
of alkynyl bromide 4 and alkyne 5, which constitutes the
final step of the synthesis. Despite the overall conver-
gence and efficiency of the original route, we found that
the preparation of intermediate 5 was not particularly
amenable to reaction scale-up. Our first task would be
to modify our synthesis of 5 to allow for the facile
preparation of multigram quantities of panaxytriol.
the corresponding TBS ether of 6 to afford 7 in ap-
proximately 99% ee. Protection of the resultant diol as
an acetonide, followed by cleavage of the TBS ether, and
subsequent bromination provided intermediate 8. The
latter was subjected to acid-induced deprotection followed
by epoxide formation to afford 9, which was then alky-
lated with Li/acetylide to give rise to coupling partner 5.
Unfortunately, the conversion of 7 to 8 was found to be
quite sluggish when the reaction was performed on a
large scale (∼20 mmol). We have developed an improved
route to 5 that converges on intermediate 9 from the
original synthesis. Thus, Sharpless asymmetric dihy-
droxylation of 6, followed by TBDPS protection of the
primary alcohol, furnished intermediate 10. Following
acetonide protection of the diol, the TBDPS group was
removed and the resultant primary alcohol was converted
to an iodide to afford 11. The latter was then deprotected
and epoxidized to provide intermediate 9 in good overall
yield from 6. The epoxide was converted to the terminal
alkyne (5), which was coupled with alkynyl bromide 4
according to the previously disclosed method, to provide
panaxytriol (1) in 51% overall yield from 6. This modified
route has been used to prepare up to 10 g of synthetic
panaxytriol.
Preparation of Synthetic Analogues of Panaxy-
triol. We next prepared several synthetic derivatives of
panaxytriol, in the hopes of constructing an SAR profile
with respect to antitumor activity. Thus, analogues were
prepared in which the C9-C10 glycol was protected as an
acetonide (12), the C3 alcohol was oxidized to a ketone
(13), and the C3 of the acetonide derivative was oxidized
to a ketone (14).
Biological Investigations: Antitumor Activity.
The in vitro cytotoxicities of panaxytriol (1) and its
derivatives (12, 13, and 14) were evaluated against
multidrug resistance (MDR)-sensitive (CCRF-CEM) and
MDR-resistant (CCRF-CEM/VBL) cell lines (Table 1). We
were interested to find that each of the panaxytriol
derivatives (12, 13, and 14) exhibited a stronger inhibi-
tory effect than did panaxytriol itself. On the basis of
these results, it would appear that the C3 alcohol function
is not required for biological activity (cf. 1 versus 13).
The acetonide derivative, 12, the most active analogue,
is roughly 6-fold more potent than panaxytriol. Impor-
tantly, each of the four compounds examined retained
its potency against the CCRF-CEM/VBL cell line, which
displays a multidrug resistance phenotype. These results
provide strong evidence that panaxytriol and its deriva-
tives are not substrates for the P-glycoprotein and thus
would not be vulnerable to multidrug resistance.
The previously described synthesis of alkyne 5 com-
menced with Sharpless asymmetric dihydroxylation13 of
(10) (a) Satoh, M.; Takeuchi, N.; Fujimoto, Y. Chem. Pharm. Bull.
1997, 45, 1114. (b) Lu, W.; Zheng, G.; Cai, J. Synlett 1998, 737. (c) Lu,
W.; Zheng, G.; Gao, D.; Cai, J. Tetrahedron 1999, 55, 7157. (d) Gurjar,
M. K.; Kumar, V. S.; Rao, B. V. Tetrahedron 1999, 55, 12563. (e) Kim,
S.-I.; Lee, Y.-H.; Ahn, B.-Z. Arch. Pharm. 1999, 332, 133. (f) Lu, W.;
Zheng, G. R.; Shen, J. S.; Cai, J. C. Chin. Chem. Lett. 1999, 10, 201.
(g) Yadav, J. S.; Maiti, A. Tetrahedron 2002, 58, 4955. (h) Mayer, S.
F.; Steinreiber, A.; Orru, R. V. A.; Faber K. J. Org. Chem. 2002, 67,
9115. (i) Yun, H.; Danishefsky, S. J. J. Org. Chem. 2003, 68, 4519.
(11) Mizumaki, Y.; Kurimoto, M.; Hirashima, Y.; Nishijima, M.;
Kamiyama, H.; Nagai, S.; Takaku, A.; Sugihara, K.; Shimizu, M.; Endo,
S. Brain Res. 2002, 950, 254.
(12) (a) Chodkiewicz, W. Ann. Chim. (Paris) 1957, 2, 819. (b)
Brandsma, L. Preparative Acetylenic Chemistry, 2nd ed.; Elsevier:
Amsterdam, 1988; pp 212-214. (c) For recent work in this area, see:
Siemsen, P.; Livingston, R. C.; Diederich, F. Angew. Chem., Int. Ed.
2000, 39, 2632.
(13) Kolb, H. C.; VanNieuwenhze, M. S.; Sharpless, K. B. Chem.
Rev. 1994, 94, 2483.
It is of note that the presence of the acetonide func-
tionality appears to confer an increase in cytotoxicity, as
evidenced by the fact that both acetonide derivatives (12
10376 J. Org. Chem., Vol. 70, No. 25, 2005

Total Synthesis as a Resource in Drug Discovery
SCHEME 1
SCHEME 2a
t
a Reaction conditions: (a) AD-mix-â, CH3SO2NH2, BuOH/H2O ) 1:1, 0 °C, 1 day, 85%, >99% ee; (b) TBDPSCl, TEA, DMAP, CH2Cl2,
90%; (c) (CH3)2C(OCH3)2, p-TsOH, CH2Cl2, 99%; (d) TBAF, THF, 0 °C to room temperature, 3 h, 100%; (e) PPh3, I2, Imidazole, CH2Cl2,
94%; (f) 1 N HCl, 3 days; (g) K2CO3, 91% for two steps; (h) Li/acetylide EDA complex, HMPA, THF, 0 °C to room temperature, 85%; (i)
CuCl, EtNH2, NH2OH‚HCl, MeOH, 0 °C, 92%.
TABLE 1. In Vitro Cytotoxicities against Tumor Cell
Linesa
IC50 (µM)
compound
CCRF-CEM
CCRF-CEM/VBLb
1
12.09 ( 1.57
1.98 ( 0.20
4.49 ( 0.41
3.23 ( 0.78
14.56 ( 6.92 (1.20x)
2.41 ( 0.05 (1.22x)
6.29 ( 1.41 (1.40x)
3.84 ( 0.08 (1.19x)
12
13
14
a XXT assay following 72-hr inhibition. CCRF-CEM is a human
T-cell acute lymphoblastic leukemia cell line. CCRF-CEM/VBL
overexpresses P-glycoprotein and displays an MDR phenotype to
MDR-associated oncolytics. b Resistance to vinblastine was 400-
fold as indicated by IC50 increases (0.0020 ( 0.0007 µM in CCRF-
CEM compared to 0.80 ( 0.10 µM in CCRF-CEM/VBL cell line).
and 14) exhibited greater in vitro activity than do their
diol counterparts (1 and 13). Hypothesizing that incor-
FIGURE 1. nOe effects of 1 and 12.
TABLE 2. Coupling Constants of 1 and 12
1
J(Hz)
12
J(Hz)
H8a/8b
H8a/9
17.09
5.97
5.61
4.01
6.51
5.83
13.71
H8a/8b
H8a/9
17.47
5.32
5.64
7.87
3.18
8.64
13.71
H8b/9
H8b/9
H9/10
H9/10
H10/11a
H10/11b
H11a/11b
H10/11a
H10/11b
H11a/11b
characteristic coupling constants for these two com-
pounds as shown in Table 2. On the basis of observed
2D nOe effects and gNMR simulation, Newman projec-
tions along the C9-C10 bond were obtained for 1 and 12.
As shown in Figure 2, panaxytriol (1) has a bent
poration of the acetonide moiety may alter the confor-
mational properties of the compound in solution, we set
out to evaluate the conformations of panaxytriol (1) and
the panaxytriol acetonide (12) through NMR spectroscopy
and computational techniques. An extensive 2D NMR
study was conducted, and selected nOe effects are shown
in Figure 1. Our computational analysis, using a quan-
tum mechanics-based gNMR program,14 projected the
(14) Proton spectra were simulated by using the gNMR program
(Cherwell Scientific Ltd., now Adept Scientific). The procedure is as
follows: initial guesses for chemical shifts and proton-proton couplings
were used to generate a theoretical multiplet band shape. Transitions
were assigned to observed peaks, and then using least-squares
methods, the theoretical band shape was fit to the experimental one.
Then, transitions were reassigned, and if needed, the procedure was
repeated until a best fit was obtained. As a final step, all proton
multiplets were compared with theoretical spectra generated by the
best-fit values.
J. Org. Chem, Vol. 70, No. 25, 2005 10377

Yun et al.
FIGURE 2. Newman projections of 1 and 12 along the C9-C10 bonds. Arrow indicates strong nOe effect.
FIGURE 3. Therapeutic effect of panaxytriol (1) in nude mice bearing MX-1 xenograft (iv injection). Black (b) Control (n ) 4).
Red (9) 1 30 mg/kg Q2Dx3, 50 mg/kg Q2Dx3, 75 mg/kg Q2Dx3. Blue (2) 1 50 mg/kg Q2Dx3, 75 mg/kg Q2Dx3, 100 mg/kg Q2Dx2.
Body weight is the difference between total weight and tumor weight.
structure, while the acetonide (12) has a fairly linear
structure in solution. These findings suggest that the
notable increase in biological activity of panaxytriol ace-
tonide (12) relative to that of panaxytriol (1) may reflect
the impact of the conformation of the C9-C10 region.
We next sought to investigate the in vivo efficacy of
panaxytriol (1) and panaxytriol acetonide (12). Thus,
nude mice bearing human mammary carcinoma xeno-
graft MX-1 were treated with panaxytriol (1) or panaxy-
triol acetonide (12) at various dosages through the slow
iv infusion protocol developed in our laboratories.15 Mice
treated with 30 mg/kg of panaxytriol exhibited some
suppression of tumor growth, but no appreciable reduc-
tion in tumor mass was observed (Figure 3). At elevated
dosage levels, improved inhibitory effects were observed.
The panaxytriol acetonide (12) demonstrated enhanced
in vivo potency, inhibiting tumor growth at levels as low
as 10 mg/kg (Figure 4). Once again, elevated dosages led
to enhanced tumor growth suppression, although treat-
ment with compound 12 did not lead to a shrinkage in
the tumor mass. Notably, even at the highest dosage
levels (100 mg/kg), no body weight decrease was observed
upon treatment with either compound 1 or 12. We
emphasize that these biological findings are particularly
noteworthy, not because of any remarkable level of
cytotoxic activity, but rather because appreciable levels
of in vivo tumor growth suppression have been observed
in a commonly used dietary supplement. Consequently,
the antitumor activity achieved with panaxytriol is
apparently not accompanied by any toxic side effects,
even at high dosage levels.
Biological Investigations: Neurotrophic Activity.
We sought to determine whether panaxytriol might be a
contributor to the neurotrophic activity observed in the
organic extracts of red ginseng. Thus, rat pheochromocy-
toma cells (PC12) were treated with 50 ng/mL NGF and
with 60 µM panaxytriol for 96 h. The cells were then
compared to a similarly prepared control, lacking only
panaxytriol. As shown in Figure 5, although neurite
growth was observed in the absence of panaxytriol, the
sample treated with 60 µM panaxytriol demonstrated
significantly enhanced neurite outgrowth. This finding
confirms that panaxytriol is a neurotrophically active
(15) Chou, T. C.; Zhang, X. G.; Harris, C.; Kuduk, S. D.; Balog, A.;
Savin, K. A.; Bertino, J. R.; Danishefsky, S. J. Proc. Natl. Acad. Sci.
U.S.A. 1998, 95, 15798.
10378 J. Org. Chem., Vol. 70, No. 25, 2005

Total Synthesis as a Resource in Drug Discovery
FIGURE 4. Therapeutic effect of panaxytriol acetonide (12) in nude mice bearing MX-1 xenograft (iv injection). Black (b) Control
(n ) 4). Red (9) 12 10 mg/kg Q2Dx3, 30 mg/kg Q2Dx3, 50 mg/kg Q2Dx2. Blue (2) 12 20 mg/kg Q2Dx3, 50 mg/kg Q2Dx3, 100
mg/kg Q2Dx2. Body weight is the difference between total weight and tumor weight.
FIGURE 5. Images of neurons.
compound that contributes to the neurotrophic activity
observed for red ginseng.
cooperativity between the various components of red
ginseng contributing to its overall activity profile? While
these questions remain presently unanswered, the re-
search described above already touches on potentially
important possibilities that invite more detailed explora-
tion. The style of chemotherapeutically based oncology
involves the use of very powerful cytotoxic agents. These,
of course, raise significant issues of selectivity of attack
on cancer cells and normal cells (i.e., therapeutic index).
Also, potent anticancer drugs are inactivated through the
phenomenon of MDR. The research described herein, by
implication, envisions an alternate direction. Perhaps
there may well be room for relatively weak antitumor
agents, provided that the toxicity risk factor is dramati-
cally reduced. In this view, a key determinant would be
the chronic nature of treatment that such agents might
well require.
Given the results described above, it may well be
appropriate to look for and investigate compounds of this
genre that offer mild antiproliferative properties in the
absence of toxicity. Studies along these lines as well as
studies dedicated to the discovery of the molecular targets
of panaxytriol, its analogues, and, more broadly, red
ginseng, are planned.
In summary, we have conducted key preliminary
studies into the in vitro and in vivo cytotoxicity of
panaxytriol. Through total synthesis, we prepared and
evaluated several synthetic panaxytriol analogues, each
of which exhibited enhanced cytotoxicity relative to the
natural product. Consequently, we have begun to chart
the first SAR map for the compound, which suggests that
the C3 hydroxyl functionality is not critical for biological
activity and that, in fact, engagement of the C9-C10 diol
as an acetonide actually leads to notably enhanced
cytotoxicity. On the basis of the results of in vitro studies,
we have obtained strong evidence that panaxytriol and
its derivatives are not substrates for the P-glycoprotein
and, therefore, are not vulnerable to the onset of multi-
drug resistance. Furthermore, through in vivo investiga-
tions, we demonstrated that panaxytriol (1) and panax-
ytriol acetonide (12) moderately suppress tumor growth
with little or no toxicity. Finally, preliminary in vitro
evaluation of panaxytriol indicates that it possesses
neurotrophic activity.
Obviously the research described above fosters a fresh
new range of questions: (i) Is there any relationship
between the manifestation of neurotrophic activity and
the anticancer activity exhibited by panaxytriol (and red
ginseng)? (ii) At the molecular level, what are the
biological targets for each of the activities? (iii) Is there
Experimental Section
Compound 12. To a THF solution of compound 1 (0.61 g,
2.191 mmol) were added Me2C(OMe)2 (3 mL, 21.91 mmol) and
J. Org. Chem, Vol. 70, No. 25, 2005 10379

Yun et al.
p-TsOH (42 mg, 0.2191 mmol) at room temperature. After
overnight, the reaction mixture was quenched with saturated
NaHCO3. After aqueous workup, it was purified by column
chromatography (hexane/ethyl acetate 15:1 to 7:1) to give
was removed. The concentrated reaction mixture was purified
by column chromatography (hexane/ethyl acetate 4:1 to 2:1)
to give compound 14 (18.4 mg, 62%) as a colorless oil: Rf 0.48
1
(hexane/ethyl acetate ) 8:1); [R]22.6 +8.6 (c 0.5, CHCl3); H
D
compound 12 (0.6567 g, 94%) as a colorless oil: Rf 0.19 (hexane/
NMR (300 MHz, CDCl3) δ 6.57 (d, 1H, J ) 17.3 Hz), 6.41 (dd,
1H, J ) 17.4, 10.0 Hz), 6.22 (d, 1H, J ) 10.0 Hz), 3.77 (m,
2H), 2.69 (m, 2H), 1.59 (m, 2H), 1.41 (s, 6H), 1.26-1.40 (m,
10H), 0.88 (t, 3H, J ) 6.6 Hz); 13C NMR (125 MHz, CDCl3) δ
178.1, 138.2, 134.7, 109.3, 85.6, 80.7, 78.2, 71.2, 66.2, 33.2, 32.2,
30.0, 29.5, 27.8, 27.4, 26.3, 24.2, 23.0, 14.5; IR (neat) ν 2985.9,
2929.1, 2857.5, 2236.0, 2153.0, 1734.0, 1717.0, 1645.5, 1616.4,
1456.5, 1379.2, 1290.0, 1243.0, 1163.6, 1070.0, 980.0, 789.3
cm-1; HRMS calcd for [M + H] 317.2117; found 317.2123.
1
ethyl acetate ) 8:1); [R]25.7 +5.0 (c 0.47, acetone); H NMR
D
(400 MHz, CDCl3) δ 5.95 (ddd, 1H, J ) 17.0, 10.1, 5.3 Hz),
5.46 (d, 1H, J ) 17.0 Hz), 5.25 (d, 1H, J ) 10.1 Hz), 4.91 (d,
1H, J ) 5.3 Hz), 3.80 (dt, 1H, J ) 7.7, 4.2 Hz), 3.72 (dt, 1H, J
) 7.9, 5.3 Hz), 2.60 (m, 2H), 1.2-1.7 (m, 12H), 1.37 (s, 6H),
0.89 (t, 3H, J ) 6.8 Hz); 13C NMR (125 MHz, CDCl3) δ 136.3,
117.6, 109.1, 80.9, 78.6, 77.2, 75.0, 71.5, 66.9, 64.0, 33.5, 32.4,
30.3, 29.8, 28.0, 27.7, 26.6, 24.2, 23.3, 14.8; IR (neat) ν 3434.8,
2927.4, 2856.3, 2256.2, 1716.7, 1458.2, 1377.4, 1242.1, 1220.6,
1066.2, 985.9, 930.6 cm-1; HRMS calcd for [M - CH3 - H]
303.1960; found 303.1946.
Acknowledgment. Dedicated with gratitude and
admiration to Professor Eun Lee at Seoul National
University on occasion of his 60th birthday. This work
was supported by the National Institutes of Health
(Grant No. HL25848). We thank Eli Lilly and Company
for the generous predoctoral fellowship awarded to H.Y.
Insightful discussion with Dr. Toshiharu Yoshino is
gratefully acknowledged. We thank Dr. William F.
Berkowitz for editorial assistance.
Compound 13. To a THF solution of compound 1 (6 mg,
0.02155 mmol) was added MnO2 (22 mg, 0.251 mmol) at room
temperature. After overnight, the reaction mixture was filtered
through a short column of Celite and the solvent was removed.
The concentrated reaction mixture was purified by column
chromatography (hexane/ethyl acetate 4:1 to 2:1) to give
compound 13 (4.5 mg, 76%) as a colorless oil: Rf 0.19 (hexane/
1
ethyl acetate ) 3:1); [R]20.7 +14.4 (c 0.44, CHCl3); H NMR
D
(300 MHz, CDCl3) δ 6.55 (d, 1H, J ) 17.3 Hz), 6.41 (dd, 1H, J
) 17.3, 10.0 Hz), 6.22 (d, 1H, J ) 10.0 Hz), 3.72 (m, 1H), 3.61
(m, 1H), 2.68 (d, 2H, J ) 6.2 Hz), 1.2-1.6 (m, 12H), 0.88 (t,
3H, J ) 6.6 Hz); 13C NMR (125 MHz, CDCl3) δ 178.1, 138.1,
134.8, 86.5, 77.6, 73.4, 72.3, 71.2, 66.1, 34.0, 32.3, 29.9, 29.6,
25.9, 25.7, 23.0, 14.9; IR (neat) ν 3300.3, 2945.4, 2850.4, 2231.9,
2150.6, 1650.8, 1607.1, 1463.4, 1400.9, 1257.2, 1163.5, 1132.3,
1094.8, 1026.0, 976.1, 938.6, 788.6 cm-1; HRMS calcd for [M
+ H] 277.1804; found 277.1808.
Note Added after ASAP Publication. In the Figure
4 caption Q2Dx2 incorrectly read Q2Dx3 in the version
published ASAP November 12, 2005; the corrected ver-
sion was published ASAP November 14, 2005.
Supporting Information Available: Characterization
data for compounds 1 and 12-14. 1H NMR and 13C NMR
spectra for 1, 5, 12-14. This material is available free of
charge via the Internet at http://pubs.acs.org.
Compound 14. To a THF solution of compound 12 (29.9
mg, 0.09389 mmol) was added MnO2 (81.6 mg, 0.9389 mmol)
at room temperature. After overnight, the reaction mixture
was filtered through a short column of Celite and the solvent
JO0515475
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