Synthesis and structure revision of tyroscherin, and bioactivities of its stereoisomers against IGF-1-dependent tumor cells

Article abstract of DOI:10.1016/j.tet.2009.03.003

Synthesis of the proposed structure of tyroscherin, a growth inhibitor of IGF-1-dependent cancer cells, was succeeded by one-pot Julia coupling. However, spectral data of the synthetic compound were not identical with those of natural tyroscherin. The stereochemistry of tyroscherin is revised to be 2S,3R,8R,10R by syntheses of stereoisomers. Synthetic tyroscherin showed more potent activity than its stereoisomers against IGF-1-dependent cancer cells.

Full text of DOI:10.1016/j.tet.2009.03.003

Tetrahedron 65 (2009) 3629–3638
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis and structure revision of tyroscherin, and bioactivities of its
stereoisomers against IGF-1-dependent tumor cells
a
a
a
b
a,
c
*
´
Ken Ishigami , Ryo Katsuta , Chie Shibata , Yoichi Hayakawa , Hidenori Watanabe , Takeshi Kitahara
a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
b Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
c School of Pharmacy, Teikyo Heisei University, 2289 Uruido, Ichihara City, Chiba 290-0193, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Synthesis of the proposed structure of tyroscherin, a growth inhibitor of IGF-1-dependent cancer cells,
was succeeded by one-pot Julia coupling. However, spectral data of the synthetic compound were not
identical with those of natural tyroscherin. The stereochemistry of tyroscherin is revised to be
2S,3R,8R,10R by syntheses of stereoisomers. Synthetic tyroscherin showed more potent activity than its
stereoisomers against IGF-1-dependent cancer cells.
Received 5 February 2009
Received in revised form 27 February 2009
Accepted 1 March 2009
Available online 6 March 2009
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
Tyroscherin
Inhibitor of IGF-1-dependent cell growth
Structure revision
One-pot Julia coupling
1. Introduction
the synthesis, but now we decided to install N-methyl group at
earlier stage to avoid complicated sequence for methylation and to
Recently, mechanism-based drugs have been remarkably no-
ticed, since they will potentially provide selective treatments for
various diseases such as infections and cancers. Insulin-like growth
factor (IGF) plays a key role in human cancer progression,1 and
selective inhibitors of its signal transduction are thought to provide
a selective treatment against IGF-dependent tumor cells. In 2004,
Hayakawa et al. isolated tyroscherin from the mycelium of Pseu-
dallescheria sp. as a potent and selective inhibitor of IGF-1-de-
pendent growth of MCF-7 human breast cancer cell.2 Then, we
started the synthesis of tyroscherin with the intention of further
research on its biological activity and structure–activity relation-
ship. We have already published a rapid communication,3 in which
we revised the stereochemistry of tyroscherin as shown in Figure 1,
by syntheses of stereoisomers. Here, we wish to report a full ac-
count of our work.
revise total yield. Compound 1 would be obtained by one-pot Julia
coupling of sulfone A and known aldehyde B.4 Sulfone A would be
prepared from ketone C via stereoselective reduction. This ketone
would be given by C3 elongation of Weinreb amide D, which would
be able to be derived from D-tyrosine.
The synthesis of the proposed structure (1) is shown in Scheme 2.
-Tyrosine was protected in a usual manner to give ester 3. This
D
ester was converted to the corresponding Weinreb amide 4, which
was subjected to N-methylation5 to give 5 without any racemiza-
tion. C3 elongation of the Weinreb amide 5 afforded amino ketone
6. This ketone was subjected to stereoselective reduction6 to give
syn-amino alcohol 7, whose stereochemistry was confirmed by NOE
experiment after conversion into cyclic carbamate 13. After pro-
tection and deprotection, the primary alcohol 7 was converted to
PT-sulfone 10 via Mitsunobu reaction.7 Then one-pot Julia cou-
pling8,9 of the sulfone 10 and known aldehyde 117 gave (E)-olefin 12
selectively. Finally, deprotection of 12 gave the desired compound,
the proposed structure of tyroscherin (1). However, 1H NMR spec-
tral data of the synthetic compound 1 were not identical with those
reported for natural tyroscherin.2 Chemical shifts of 1-H, 2-H, and
3-H were much different between natural tyroscherin and syn-
thetic 1 as shown in Table 1. Hayakawa et al. have determined the
relative configuration at C-2 and C-3 by analysis of 1H–1H and
1H–13C coupling constants,2,10 after determination of the absolute
configuration at C-3 by modified Mosher’s method.11 We supposed
the appropriate relative stereochemistry of natural compound to be
2. Results and discussion
Our retrosynthesis of the proposed structure (1) is shown in
Scheme 1. We selected one-pot Julia coupling as a key step, which
could provide an easy way to synthesize other stereoisomers. In our
previous report,3 N-methyl group was introduced at later stage of
* Corresponding author. Fax: þ81 3 5841 8019.
E-mail address: ashuten@mail.ecc.u-tokyo.ac.jp (H. Watanabe).
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.03.003

3630
K. Ishigami et al. / Tetrahedron 65 (2009) 3629–3638
HO
HO
HNMe
HNMe
R
3
2
8
10
S
R
R
OH
OH
Proposed structure of tyroscherin (1)
Revised structure of tyroscherin (2)
Figure 1. Proposed and revised structures of tyroscherin.
MOMO
Boc
MeN
Proposed
structure
+
OHC
Boc
SO2PT
(1)
Ph
OTBS
A
B
N
N
N
PT =
N
Boc
MOMO
MOMO
MeN
MeN
Me
N
D-Tyrosine
OMe
OTBS
O
O
C
D
Scheme 1. Retrosynthetic analysis of the proposed structure of tyroscherin (1).
2,3-anti. To ascertain the correct structure of natural tyroscherin,
we started synthesis of 2,3-anti-stereoisomers of 1.
the absolute configuration of natural tyroscherin was revised to be
2S,3R,8R,10R.
Four possible 2,3-anti-stereoisomers (2, 14, ent-2, and ent-14)
are shown in Figure 2. In our previous report,3 a mixture of 14 and
ent-2 (2:1) was synthesized from enantiomerically poor material
(33% ee) and the relative configuration of natural tyroscherin was
determined to be same as the minor component (ent-2) by
comparing 1H NMR spectrum of the mixture (14/ent-2¼2:1) with
that of natural tyroscherin (Fig. 3 and Table 1). After that com-
pounds 2 and ent-2 were synthesized enantioselectively in order
to determine the absolute configuration of tyroscherin. 1H NMR
spectra of these compounds were completely identical with that
of natural tyroscherin (Fig. 3 and Table 1). The specific rotation
In this paper, we describe the enantioselective syntheses of all of
the four 2,3-anti-stereoisomers (2, 14, ent-2, and ent-14) in order to
examine the structure–activity relationship for tyroscherin.
At first, syntheses of (2R,3S,8S,10S)-isomer (ent-2) and
(2R,3S,8R,10R)-isomer (ent-14) are shown in Scheme 3. Weinreb
amide (5) derived from D-tyrosine was reduced to aldehyde 15,
whose enantiomeric purity was determined to be 97% ee by chiral
HPLC (Chiralpak AD-H, hex/i-PrOH¼19:1). The aldehyde 15 was
reacted with siloxypropyllithium in Et2O to afford a mixture of
anti- and syn-amino alcohols (16 and 7). After protection of the
hydroxy group, anti- and syn-isomers were separated by silica gel
chromatography (17/8¼5:1). The stereochemistry of 16 at C-3 was
confirmed by NOE experiment after conversion to cyclic carbamate
22. The anti-isomer 17 was converted to the corresponding sulfone
19 and then it was subjected to one-pot Julia coupling with 11 to
give (E)-olefin 20 selectively. Finally, deprotection was followed by
of 2 was identical to that of natural tyroscherin, while ent-2
25
showed opposite sign of specific rotation {2: [
a
]
D
ꢀ21 (c 0.35,
24
24
MeOH), ent-2: [
a
]
þ20 (c 0.35, MeOH), natural tyroscherin: [
a]
D
D
ꢀ21 (c 0.35, MeOH)2}. From these results, we finally concluded
that the correct stereostructure of natural tyroscherin is 2, that is,
Boc
O
MOMO
Boc
Boc
MOMO
MOMO
e
g
a, b, c
d
MeN
HN
RN
f
Me
OMe
D-Tyrosine
N
CO2Me
OTBS
O
3
4 (R = H)
6
5 (R = Me)
MOMO
Boc
Boc
OR
MOMO
h
Boc
MOMO
MeN
MeN
MeN
i
l
OTBS
X
OTBS
OTBS
12
7 (R = H)
9 (X = OH)
OHC
j, k
10 (X = SO2PT)
8 (R = TBS)
11
O
HO
HNMe
MOMO
n
m
O
MeN
7
OTBS
OH
Proposed structure of tyroscherin (1)
H
H
13
NOE
Scheme 2. Synthesis of the proposed structure (1) of tyroscherin. (a) SOCl2, MeOH, reflux; (b) NaOH, H2O, then (Boc)2O, THF, 0 ꢁC to rt; (c) MOMCl, DIPEA, CH2Cl2, rt, 93% in three
steps; (d) MeNHOMe$HCl, i-PrMgBr, THF, ꢀ20 ꢁC to rt, 82%; (e) NaH, MeI, DMF, ꢀ20 ꢁC, 76%; (f) TBSO(CH2)3I, t-BuLi, Et2O, ꢀ78 ꢁC to rt, 90%; (g) NaBH4, MeOH, EtOH, ꢀ20 ꢁC, 96%,
single isomer; (h) TBSOTf, 2,6-lutidine, CH2Cl2, rt, 83%; (i) Dowex-50, MeOH, H2O, rt, 62%; (j) PTSH, DEAD, PPh3, THF, 0 ꢁC to rt; (k) 35% H2O2, (NH4)6Mo7O24$4H2O, EtOH, 0 ꢁC to rt,
86% in two steps; (l) KHMDS, THF, ꢀ78 ꢁC to rt, 67%; (m) TFA, THF, MeOH, H2O, reflux, quant.; (n) NaH, THF, reflux, 76%.

K. Ishigami et al. / Tetrahedron 65 (2009) 3629–3638
3631
Table 1
Selected 1H NMR (500 MHz, CD3OD) data and specific rotations for natural tyroscherin and synthetic stereoisomers
1H NMR (ppm, multiplicity, Hz)
[a]
D
(c 0.35, MeOH)
1-Ha
1-Hb
2-H
3-H
12-H
8-Me
10-Me
Natural tyroscherin2
2.86,
dd, 14.0, 7.0
2.91,
dd, 14.0, 7.0
3.34,
ddd, 7.0, 7.0, 3.0
3.83,
dt, 10.0, 3.0
0.84,
t, 7.0
0.91,
d, 6.5
0.82,
d, 6.5
ꢀ21
Proposed structure (1)
2.87,
dd, 13.8, 8.3
2.96,
dd, 13.8, 6.0
3.22,
ddd, 8.3, 6.0, 4.7
3.62,
ddd, 6.8, 5.3, 4.7
0.85,
t, 70
0.89,
d, 6.2
0.81,
d, 6.5
þ11
Mixture of anti-isomers
(14/ent-2¼2:1)
Major (14)
2.86,
dd, 14.7, 7.9
2.86,
2.93,
dd, 14.7, 6.7
2.91,
3.32–3.38,
m, overlapped
3.32–3.38,
3.81–3.87,
m, overlapped
3.81–3.87,
0.84,
t, 7.3
0.84,
t, 7.3
0.92,
d, 6.8
0.91,
0.81,
d
d
d, 6.5
0.82,
d, 6.5
Minor (ent-2)
dd, 14.7, 7.9
dd, 14.7, 7.0
m, overlapped
m, overlapped
d, 6.8
(2S,3R,8R,10R)-Isomer (2)
2.86,
dd, 14.7, 7.9
2.91,
dd, 14.7, 7.0
3.34,
ddd, 7.9, 7.0, 3.0
3.83,
ddd, 9.4, 3.6, 3.0
0.84,
t, 7.3
0.91,
d, 6.8
0.82,
d, 6.5
ꢀ21
recrystallization to afford (2R,3S,8S,10S)-isomer (ent-2) in a dia-
stereomerically pure form. In a similar manner, (2R,3S,8R,10R)-
isomer (ent-14) was also obtained via one-pot Julia coupling of the
sulfone 19 with aldehyde ent-11.
stereoisomers, and it was found that (2S,3R)-stereochemistry was
important for the selective inhibition. We wish our study on these
compounds, which have potent and selective activities, would offer
any useful information for further investigation on the related fields.
On the other hand, syntheses of (2S,3R,8R,10R)-isomer (2) and
(2S,3R,8S,10S)-isomer (14) are shown in Scheme 4. L-Tyrosine was
3. Experimental
3.1. General
converted to Weinreb amide ent-5 in five steps. Reduction of ent-5
with LAH gave aldehyde ent-15 with no racemization and its en-
antiomeric purity was confirmed to be >99% ee by chiral HPLC. This
aldehyde was subjected to C3 elongation to afford ent-16 wherein
diastereoselectivity was improved by using THF as a solvent instead
of Et2O (anti/syn¼13:1 after separation of ent-17 and ent-8). In the
same manner as Scheme 3, ent-16 was transformed to give
(2S,3R,8R,10R)-isomer (2) and (2S,3R,8S,10S)-isomer (14) as color-
less crystals, respectively. The specific rotation, melting point, and
spectroscopic data of 2 were reconfirmed to be fully identical to
those of natural tyroscherin.2
Having succeeded in the total syntheses of all the four stereo-
isomers, our next interest came to structure–activity relationship of
tyroscherin. We examined the effects of tyroscherin and its de-
rivatives on IGF-1-dependent MCF-7 human breast cancer cells
(Table 2). Tyroscherin (2) inhibited the growth of MCF-7 cells in
a serum-free medium containing IGF-1with an IC50 of 3.4 nM. In
the presence of fetal bovine serum instead of IGF-1, tyroscherin
Melting points were measured with a Yanaco micro-melting
point apparatus and are uncorrected values. Optical rotations were
recorded with a JASCO DIP-1000 polarimeter. IR spectra were
measured with a JASCO FT/IR-230 spectrophotometer. 1H and 13C
NMR were recorded on JEOL JNM AL300 or JEOL JNM GSX500.
Chemical shifts (d) were referenced to the residual solvent peaks as
the internal standard (CDCl3: dH¼7.26; DMSO-d6: dH¼2.49; CD3OD:
dH¼3.30, dC¼49.0). Refractive indexes were measured with an Atago
1 T refractometer. Mass spectra were recorded on JEOL JMS SX102.
Column chromatography was performed using Kanto silica gel 60N
(0.060–0.200 mm). TLC was carried out on Merck glass plates pre-
coated with silica gel 60 F254 (0.25 mm). HPLC was performed using
Hitachi L-2130 and Hitachi L-2400 UV detector (254 nm).
3.2. Synthetic studies
exhibited no activity against MCF-7 cells at less than 1 mM. As
shown in Table 2, tyroscherin (2) showed more potent and selective
activity than other stereoisomers. Interestingly, the isomer 14 and
8,10-didemethyl-derivative 23 (Fig. 4), which had (2S,3R)-stereo-
chemistry, exhibited medium selectivities. The (2S,3R)-stereo-
chemistry should have important role for selective inhibition of
IGF-1-dependent growth of MCF-7 cells (Fig. 4).
3.2.1. Methyl (R)-N-(tert-butoxycarbonyl)-O-(methoxymethyl)-
tyrosinate (3)
To a mixture of D-tyrosine (10.9 g, 60 mmol) and MeOH (37 ml)
was added thionyl chloride (4.8 ml, 66 mmol) dropwise at 0 ꢁC. The
reaction mixture was refluxed for 4 h and concentrated in vacuo.
Crude white solids (14.0 g) were used for next reaction without
further purification.
In summary, we succeeded in the first synthesis of tyroscherin
and its stereoisomers, in 5.2–20.0% overall yield from D- and L-ty-
To a solution of crude material (13.9 g) in water (30 ml) were
added successively 6 M aqueous NaOH solution (10 ml), THF
(100 ml), and di-(tert-butyl)dicarbonate (20.1 ml, 60 mmol) at 0 ꢁC,
and the mixture was stirred at room temperature for 2 h. The
rosines, and revised the absolute configuration of tyroscherin to be
2S,3R,8R,10R. Inhibitory activity against IGF-1-dependent growth of
MCF-7 cells was evaluated using the synthesized tyroscherin and its
HO
HO
HNMe
R
HNMe
R
S
S
S
S
R
R
OH
2
OH
14
HO
HO
HNMe
S
HNMe
S
R
S
S
R
R
R
OH
ent-2
OH
ent-14
Figure 2. Structures of possible anti-isomers.

3632
K. Ishigami et al. / Tetrahedron 65 (2009) 3629–3638
8-Me (d) 12-H (t) 10-Me (d)
1-Hb (dd)
1-Ha (dd)
Natural Tyroscherin
Mixture of anti-isomers
[14 (major) + ent-2 (minor)]
(2S,3R,8R,10R)-isomer (2)
Figure 3. 1H NMR signals of natural and synthesized compounds (1-H2 and Me groups).
reaction mixture was filtered, poured into saturated aqueous am-
monium chloride solution, and extracted with ethyl acetate. The
organic layer was washed with 1 N HCl, saturated aqueous sodium
bicarbonate solution, and brine, dried over anhydrous magnesium
sulfate, and concentrated in vacuo. Residual crystals (17.9 g) were
used for next reaction without further purification.
To a solution of crude material (17.7 g) in dichloromethane
(200 ml) were added N,N-diisopropylethylamine (31.4 ml,
180 mmol) and chloromethyl methyl ether (13.7 ml, 120 mmol) at
0 ꢁC and the mixture was stirred at room temperature for 24 h. The
reaction mixture was poured into saturated aqueous ammonium
chloride solution and extracted with ethyl acetate. The organic
layer was washed with 1 N HCl, saturated aqueous sodium bi-
carbonate solution, and brine, and dried over anhydrous magne-
sium sulfate. After concentration in vacuo, the residue was
chromatographed over silica gel. Elution with hexanes/ethyl ace-
isopropyl bromide (10.1 g, 82.1 mmol) solution in ether (45 ml) was
slowly added to the reaction mixture at room temperature and it
was stirred for 1 h at the same temperature. The resultant solution
was added dropwise to a mixture of ester 3 (6.78 g, 20.0 mmol),
N,O-dimethylhydroxylamine hydrochloride (4.29 g, 44.0 mmol),
and THF (200 ml) at ꢀ20 ꢁC under argon atmosphere, and this
mixture was stirred for 30 min at room temperature. The reaction
mixture was poured into saturated aqueous ammonium chloride
solution and extracted with ethyl acetate. The organic layer was
washed with 1 N HCl, saturated aqueous sodium bicarbonate so-
lution, and brine, and dried over anhydrous magnesium sulfate.
After concentration in vacuo, the residue was chromatographed
over silica gel. Elution with hexanes/ethyl acetate (3:1 to 1:1) gave 4
25
(6.05 g, 82%) as colorless prisms. Mp¼69–72 ꢁC. [
a
]
D
ꢀ18 (c 1.0,
CHCl3). IR (Nujol):
(300 MHz, CDCl3):
n
¼3335, 1698, 1649, 1510, 1150 cmꢀ1
.
1H NMR
d
¼1.39 (9H, br s), 2.82 (1H, dd, J¼13.5, 6.9 Hz),
tate (3:1) gave 3 (19.0 g, 93% in three steps) as colorless prisms.
2.99 (1H, dd, J¼13.5, 6.0 Hz), 3.17 (3H, br s), 3.46 (3H, s), 3.68 (3H, s),
4.91 (1H, m), 5.14 (1H, m,), 5.14 (2H, s), 6.95 (2H, d, J¼8.4 Hz), 7.07
(2H, d, J¼8.4 Hz). ESI-TOFMS m/z calcd for C18H28N2NaO6 [MþNa]þ
391.1840, found 391.1827.
25
Mp¼67–69 ꢁC. [
a]
ꢀ48 (c 1.0, CHCl3). IR (Nujol):
n
¼3378, 1739,
D
1700, 1610, 1226 cmꢀ1. 1H NMR (300 MHz, CDCl3)
d
¼1.42 (9H, br s),
3.01 (1H, dd, J¼14.1, 6.3 Hz), 3.04 (1H, dd, J¼14.1, 6.0 Hz), 3.47 (3H,
s), 3.72 (3H, s), 4.55 (1H, m), 4.96 (1H, br d, J¼7.2 Hz), 5.15 (2H, s),
6.96 (2H, d, J¼8.4 Hz), 7.03 (2H, d, J¼8.4 Hz). ESI-TOFMS m/z calcd
for C17H25NNaO6 [MþNa]þ 362.1574, found 362.1591.
3.2.3. (R)-N-
a-(tert-Butoxycarbonyl)-N-methoxy-O-
(methoxymethyl)-N,N-
a-dimethyltyrosinamide (5)
To a solution of Weinreb amide 4 (4.42 g, 12.0 mmol) in DMF
(50 ml) was added portionwise a suspension of NaH (0.30 g,
12.6 mmol) in THF (5 ml) at ꢀ20 ꢁC under argon atmosphere. After
stirring for 2 h at same temperature, MeI (1.12 ml, 18.0 mmol) was
added dropwise to the reaction mixture. After stirring for 3 h, the
reaction mixture was poured into brine, and extracted with ether.
3.2.2. (R)-N-a-(tert-Butoxycarbonyl)-N-methoxy-O-
(methoxymethyl)-N-methyltyrosinamide (4)
To a mixture of magnesium turnings (2.19 g, 90.1 mmol) and
ether (5 ml) was added isopropyl bromide (1.0 g, 8.1 mmol) at room
temperature and the mixture was stirred for 5 min. A solution of
Boc
Boc
Boc
OR
Boc
MOMO
MOMO
MOMO
MOMO
MeN
MeN
MeN
MeN
Me
OMe
a
d
b
N
CHO
OTBS
X
O
OTBS
5
15
(97% e.e.)
16 (R = H)
18 (X = OH)
c
e, f
17 (R = TBS)
19 (X = SO2PT)
HO
Boc
MOMO
MOMO
MeN
HNMe
OH
g
h
19
16
OTBS
k
OHC
(2R,3S,8S,10S)-isomer (ent-2)
20
MeN
21
11
O
MOMO
MeN
O
HO
Boc
OTBS
HNMe
i
j
H H
19
22
NOE
OH
OTBS
OHC
(2R,3S,8R,10R)-isomer (ent-14)
ent-11
Scheme 3. Synthesis of (2R,3S,8S,10S)-isomer (ent-2) and (2R,3S,8R,10R)-isomer (ent-14). (a) DIBAL, Et2O, ꢀ20 ꢁC to rt, 97% ee; (b) TBSO(CH2)3I, t-BuLi, Et2O, ꢀ78 ꢁC to rt; (c) TBSOTf,
2,6-lutidine, CH2Cl2, 0 ꢁC, 61% in three steps, dr¼5:1; (d) Dowex-50, MeOH, H2O, rt, 75%; (e) PTSH, DEAD, PPh3, THF, 0 ꢁC to rt,; (f) 35% H2O2, (NH4)6Mo7O24$4H2O, EtOH, 0 ꢁC to rt,
83% in two steps; (g) KHMDS, THF, ꢀ78 ꢁC to rt, 73%; (h) TFA, THF, MeOH, H2O, 50 ꢁC, 86%; (i) KHMDS, THF, ꢀ78 ꢁC to rt, 56%; (j) TFA, THF, MeOH, H2O, 50 ꢁC, 89%; (k) NaH, THF,
reflux, 68%.

K. Ishigami et al. / Tetrahedron 65 (2009) 3629–3638
3633
MOMO
Boc
Boc
Boc
MOMO
MOMO
HN
RN
MeN
Me
L-Tyrosine
MOMO
g
a, b, c
d
f
N
CO2Me
CHO
OMe
O
ent-3
ent-4 (R = H)
ent-15
(>99% e.e.)
e
ent-5 (R = Me)
Boc
MOMO
Boc
OR
Boc
MOMO
MeN
MeN
MeN
i
l
OTBS
X
OTBS
ent-20
OTBS
ent-18 (X = OH)
OHC
ent-16 (R = H)
h
j, k
ent-11
ent-17 (R = TBS)
ent-19 (X = SO2PT)
HO
HO
Similarly:
HNMe
HNMe
n, o
m
ent-19
OH
(2S,3R,8R,10R)-isomer (2)
OH
(2S,3R,8S,10S)-isomer (14)
OHC
11
Scheme 4. Synthesis of (2S,3R,8R,10R)-isomer (2). (a) SOCl2, MeOH, reflux; (b) NaOH, H2O, then (Boc)2O, THF, 0 ꢁC to rt; (c) MOMCl, DIPEA, CH2Cl2, rt, 99% in three steps; (d)
MeNHOMe$HCl, i-PrMgBr, THF, ꢀ20 ꢁC to rt, 87%; (e) NaH, MeI, DMF, ꢀ20 ꢁC, 95%; (f) LiAlH4, ether, 0 ꢁC, >99% ee; (g) TBSO(CH2)3I, t-BuLi, THF, ꢀ78 ꢁC; (h) TBSOTf, 2,6-lutidine,
CH2Cl2, 0 ꢁC to rt, 55% in three steps, dr¼13:1; (i) Dowex-50, MeOH, H2O, rt, 82%; (j) PTSH, DEAD, PPh3, THF, 0 ꢁC to rt; (k) 35% H2O2, (NH4)6Mo7O24$4H2O, EtOH, 0 ꢁC to rt, 83% in
two steps; (l) KHMDS, THF, ꢀ78 ꢁC to rt, 70%; (m) TFA, THF, MeOH, H2O, 50 ꢁC, 87%; (n) KHMDS, THF, ꢀ78 ꢁC to rt, 58%; (o) TFA, THF, MeOH, H2O, 50 ꢁC, 71%.
The organic layer was washed with water and brine and dried over
anhydrous magnesium sulfate. After concentration in vacuo, the
residue was chromatographed over silica gel. Elution with hexanes/
DMSO-d6, 90 ꢁC):
d
¼0.03 (6H, s), 0.87 (9H, s),1.26–1.40 (2H, m),1.32
(9H, br s), 1.65–1.77 (2H, m), 2.59 (3H, s), 2.79 (1H, dd, J¼14.4,
8.4 Hz), 3.07 (1H, dd, J¼14.4, 4.8 Hz), 3.37 (3H, s), 3.58 (2H, t,
J¼6.3 Hz), 4.52 (1H, dd, J¼8.4, 4.8 Hz), 5.11 (2H, s), 6.91 (2H, d,
J¼8.4 Hz), 7.09 (2H, d, J¼8.4 Hz). ESI-TOFMS m/z calcd for
C26H45NNaO6Si [MþNa]þ 518.2908, found 518.2901.
acetone (8:1) gave 5 (3.48 g, 76%) as colorless prisms. Mp¼41–
26
44 ꢁC. [
a
]
þ93 (c 1.0, CHCl3). IR (Nujol): ¼1682, 1613, 1514, 1233,
n
1151 cmꢀD1. 1H NMR (300 MHz, DMSO-d6, 90 ꢁC):
d
¼1.27 (9H, br s),
2.73 (3H, s), 2.83 (1H, dd, J¼14.1, 9.3 Hz), 2.92 (1H, dd, J¼14.1,
6.0 Hz), 3.11 (3H, s), 3.37 (3H, s), 3.63 (3H, s), 5.11 (2H, s), 5.18 (1H,
m), 6.92 (2H, d, J¼7.8 Hz), 7.10 (2H, d, J¼7.8 Hz). ESI-TOFMS m/z
calcd for C19H30N2NaO6 [MþNa]þ 405.1996, found 405.1994.
3.2.5. tert-Butyl (1R,2R)-[5-(tert-butyldimethylsilyloxy)-2-
hydroxy-1-[4-(methoxymethoxy)benzyl]pentyl]methyl-
carbamate (7)
To a solution of ketone 6 (3.74 g, 7.54 mmol) in EtOH (30 ml) and
MeOH (100 ml) was added sodium borohydride (571 mg,
15.1 mmol) at ꢀ20 ꢁC and the mixture was stirred for 3 h at the
same temperature. The reaction mixture was poured into saturated
aqueous ammonium chloride solution and extracted with ether.
The organic layer was washed with brine and dried over anhydrous
sodium sulfate. After concentration in vacuo, the residue was
3.2.4. tert-Butyl (R)-[5-(tert-butyldimethylsilyloxy)-1-[4-
(methoxymethoxy)benzyl]-2-oxopentyl]methylcarbamate (6)
Under argon atmosphere, a solution of t-BuLi in pentane
(1.59 M, 29.4 ml, 46.8 mmol) was diluted with ether (35 ml). To this
solution was added dropwise a solution of 1-(tert-butyldime-
thylsilyloxy)-3-iodopropane (7.04 g, 23.4 mmol) in ether (15 ml) at
ꢀ78 ꢁC. After stirring for 30 min, the resultant lithium reagent was
added slowly to a solution of amide 5 (4.98 g, 13.0 mmol) in ether
(100 ml) at ꢀ78 ꢁC under argon. After stirring for 30 min, the re-
action mixture was allowed to warm to room temperature and
stirred for 15 min. This mixture was poured into ice-cold brine
and extracted with ether. The organic layer was washed with water
and brine and dried over anhydrous magnesium sulfate. After
concentration in vacuo, the residue was chromatographed over
chromatographed over silica gel. Elution with hexanes/ethyl ace-
20
tate (7:1) gave 7 (3.62 g, 96%) as a colorless oil. nD¼1.4781. [
(c 1.0, CHCl3). IR (film):
1010 cmꢀ1 1H NMR (300 MHz, DMSO-d6, 90 ꢁC):
a]
þ41
D
n
¼3439, 1668, 1613, 1512, 1234, 1151,
.
d
¼0.02 (6H, s),
0.87 (9H, s), 1.14–1.68 (4H, m), 1.25 (9H, br s), 2.70–2.85 (2H, m),
2.73 (3H, s), 3.37 (3H, s), 3.59 (2H, t, J¼6.3 Hz), 4.09 (1H, m), 4.38
(1H, m), 5.10 (2H, s), 6.89 (2H, d, J¼8.7 Hz), 7.08 (2H, d, J¼8.7 Hz).
ESI-TOFMS m/z calcd for C26H47NNaO6Si [MþNa]þ 520.3065, found
520.3092.
silica gel. Elution with hexanes/acetone (10:1) gave 6 (5.83 g, 90%)
25
as a colorless oil. nD¼1.4788. [
a
]
þ130 (c 1.0, CHCl3). IR (film):
D
n
¼1696, 1612, 1511, 1253, 1153, 1008 cmꢀ1
.
1H NMR (300 MHz,
3.2.6. tert-Butyl (1R,2R)-[2,5-bis(tert-butyldimethylsilyloxy)-1-[4-
(methoxymethoxy)benzyl]pentyl]methylcarbamate (8)
To a solution of alcohol 7 (2.01 g, 4.04 mmol) in dichloro-
methane (40 ml) were added 2,6-lutidine (1.18 ml, 10.1 mmol) and
TBSOTf (1.11 ml, 4.85 mmol) at 0 ꢁC. The reaction mixture was
Table 2
Selective cytotoxicity of tyroscherin and its derivatives against IGF-1-dependent
MCF-7 cells
Compound
IC50 (nM)
Selectivity index
þIGF-1
3.4
75
13
98
290
220
þFBS
6000
23,000
3900
4000
7700
4500
HO
HNMe
Tyroscherin (2)
1800
310
300
41
27
21
8,10-Didemethyltyroscherin (23)
(2S,3R,8S,10S)-Isomer (14)
(2R,3S,8R,10R)-Isomer (ent-14)
(2R,3R,8S,10S)-Isomer (1)
(2R,3S,8S,10S)-Isomer (ent-2)
OH
8,10-Didemethyltyroscherin (23)
Figure 4. 8,10-Didemethyl-derivative for bioassay.

3634
K. Ishigami et al. / Tetrahedron 65 (2009) 3629–3638
warmed to room temperature and stirred for 2 h. It was poured into
saturated aqueous ammonium chloride solution and extracted with
ether. The organic layer was washed with water and brine and dried
over anhydrous magnesium sulfate. After concentration in vacuo,
the residue was chromatographed over silica gel. Elution with
allowed to warm to room temperature and poured into saturated
aqueous ammonium chloride solution. The mixture was extracted
with ether, and organic layer was washed with water and brine.
After drying over anhydrous magnesium sulfate, the solution was
concentrated in vacuo. The residue was chromatographed over
hexanes/ethyl acetate (15:1) gave 8 (2.05 g, 83%) as a colorless oil.
silica gel. Elution with hexanes/ethyl acetate (8:1) gave 12 (173 mg,
25
25
nD¼1.4741. [
a
]
þ24 (c 1.0, CHCl3). IR (film):
n
¼1692, 1612, 1512,
67%) as a colorless oil. nD¼1.4794. [
a
]
þ17 (c 1.0, CHCl3). IR (film)
D
D
1254, 1151, 1011 cmꢀ1. 1H NMR (300 MHz, DMSO-d6, 90 ꢁC):
d
¼0.03
n
¼1692, 1612, 1512, 1253, 1152, 1011 cmꢀ1
.
1H NMR (300 MHz,
(6H, s), 0.09 (6H, s), 0.88 (9H, s), 0.91 (9H, s), 1.21 (9H, br s), 1.45–
1.65 (4H, m), 2.60–2.90 (2H, m), 2.72 (3H, s), 3.36 (3H, s), 3.50–3.65
(2H, m), 3.91 (1H, m), 4.25 (1H, m), 5.10 (2H, s), 6.89 (2H, d,
J¼8.4 Hz), 7.06 (2H, d, J¼8.4 Hz). ESI-TOFMS m/z calcd for
C32H61NNaO6Si2 [MþNa]þ 634.3930, found 634.3966.
DMSO-d6, 90 ꢁC):
d
¼0.09 (3H, s), 0.09 (3H, s), 0.82 (3H, d, J¼6.6 Hz),
0.82 (3H, t, J¼7.5 Hz), 0.91 (9H, s), 0.92 (3H, d, J¼6.9 Hz), 1.02 (1H,
ddd, J¼13.2, 7.8, 5.1 Hz), 1.05–1.45 (4H, m), 1.22 (9H, br s), 1.48–1.61
(2H, m), 1.93–2.22 (3H, m), 2.66 (1H, m), 2.73 (3H, s), 2.84 (1H, dd,
J¼14.1, 10.8 Hz), 3.36 (3H, s), 3.88 (1H, ddd, J¼10.8, 5.7, 5.7 Hz), 4.28
(1H, m), 5.10 (2H, s), 5.27 (1H, dd, J¼15.3, 7.2 Hz), 5.34 (1H, dt,
J¼15.3, 6.3 Hz), 6.90 (2H, d, J¼8.4 Hz), 7.07 (2H, d, J¼8.4 Hz). ESI-
TOFMS m/z calcd for C34H61NNaO5Si [MþNa]þ 614.4211, found
614.4251.
3.2.7. tert-Butyl (1R,2R)-[2-(tert-butyldimethylsilyloxy)-5-
hydroxy-1-[4-(methoxymethoxy)benzyl]pentyl]methyl-
carbamate (9)
Dowex-50 (0.75 g) was washed with deionized water three
times. To a solution of bis-TBS ether 8 (1.98 g, 3.24 mmol) in MeOH
(60 ml) was added a suspension of Dowex-50 in deionized water
(5 ml) and stirred for 36 h at room temperature. After filtration,
3.2.10. (2R,3R,6E,8S,10S)-1-(4-Hydroxyphenyl)-8,10-dimethyl-2-
(methylamino)dodec-6-en-3-ol (1, proposed structure of
tyroscherin)
triethylamine (200
m
l) was added to the filtrate. After concentration
To a solution of 12 (135 mg, 0.23 mmol) in THF (2 ml), MeOH
in vacuo, the residue was chromatographed over silica gel. Elution
(1 ml), and water (1 ml) was added trifluoroacetic acid (400 ml). The
with hexanes/ethyl acetate (4:1 to 2:1) gave 9 (1.00 g, 62%) as
reaction mixture was refluxed for 10 h and concentrated in vacuo.
The residue was chromatographed over silica gel. Elution with
21
a colorless oil. nD¼1.4817. [
a
]
þ29 (c 1.0, CHCl3). IR (film): ¼3449,
n
D
1739, 1690, 1612, 1512, 1253, 1152 cmꢀ1. 1H NMR (300 MHz, DMSO-
d6, 90 ꢁC):
chloroform/MeOH (7:1) gave 1 (76 mg, quant.) as a colorless oil.
25
d¼0.09 (6H, s), 0.91 (9H, s), 1.21 (9H, br s), 1.45–1.65 (4H,
nD¼1.4714. [
a]
þ11 (c 0.35, CH3OH). IR (KBr):
n
¼3382, 2958, 1681,
D
m), 2.70 (1H, m), 2.71 (3H, s), 2.81 (1H, dd, J¼14.1, 11.1 Hz), 3.35 (3H,
s), 3.35–3.45 (2H, m), 3.90 (1H, m), 4.25 (1H, m), 5.10 (2H, s), 6.90
(2H, d, J¼8.7 Hz), 7.07 (2H, d, J¼8.7 Hz). ESI-TOFMS m/z calcd for
C26H47NNaO6Si [MþNa]þ 520.3065, found 520.3092.
1517, 1202, 800 cmꢀ1
.
1H NMR (500 MHz, CD3OD):
d
¼0.81 (3H, d,
J¼6.5 Hz), 0.85 (3H, t, J¼7.0 Hz), 0.89 (3H, d, J¼6.2 Hz), 0.97 (1H,
ddd, J¼13.0, 8.6, 4.2 Hz), 1.13 (1H, m), 1.2–1.35 (2H, m), 1.21 (1H,
ddd, J¼13.0, 9.4, 4.7 Hz), 1.45–1.6 (2H, m), 1.95–2.15 (3H, m), 2.67
(3H, s), 2.87 (1H, dd, J¼13.8, 8.3 Hz), 2.96 (1H, dd, J¼13.8, 6.0 Hz),
3.22 (1H, ddd, J¼8.3, 6.0, 4.7 Hz), 3.62 (1H, ddd, 6.8, 5.3, 4.7 Hz), 5.16
(1H, dd, J¼15.1, 8.1 Hz), 5.27 (1H, dt, J¼15.1, 6.5 Hz), 6.77 (2H, quasi
d, J¼8.1 Hz), 7.11 (2H, quasi d, J¼8.1 Hz). 13C NMR (125 MHz,
3.2.8. tert-Butyl (1R,2R)-[2-(tert-butyldimethylsilyloxy)-1-[4-
(methoxymethoxy)benzyl]-5-[(1-phenyl-1H-tetrazol-5-
yl)sulfonyl]pentyl]methylcarbamate (10)
The solution of alcohol 9 (920 mg, 1.85 mmol) in THF (80 ml)
were added diethyl azodicarboxylate (387 mg, 2.22 mmol), PPh3
(582 mg, 2.22 mmol), and 5-mercapto-1-phenyl-1H-tetrazole
(396 mg, 2.22 mmol) at 0 ꢁC. The reaction mixture was stirred for
1 h at room temperature and concentrated in vacuo. The residue
was dissolved in 95% EtOH (40 ml), and ammonium molybdate
tetrahydrate (487 mg, 0.39 mmol) and 35% aqueous hydrogen
peroxide solution (3 ml) were added to the solution at 0 ꢁC. This
mixture was stirred for 24 h at room temperature, poured into 10%
aqueous Na2S2O3 solution, and extracted with EtOAc. Organic layer
was washed with brine and dried over anhydrous sodium sulfate.
After concentration in vacuo, the residue was chromatographed
CD3OD):
d
¼11.7, 19.3, 22.3, 29.3, 31.1, 31.8, 33.1, 34.1, 35.4, 35.7, 45.5,
65.9, 68.7, 116.8, 127.6, 128.3, 131.4, 138.6, 157.9. ESI-TOFMS m/z
calcd for C21H36NO2 [MþH]þ 334.2741, found 334.2773.
3.2.11. (4R,5R)-5-[3-(tert-Butyldimethylsilyloxy)propyl]-4-[4-
(methoxymethoxy)benzyl]-3-methyl-1,3-oxazolidin-2-one (13)
To a solution of amino alcohol 7 (98 mg, 0.20 mmol) in THF
(5 ml) was added NaH (13 mg, 0.32 mmol) at room temperature
and the resulting mixture was stirred for 16 h under reflux. The
reaction mixture was poured into saturated aqueous ammonium
chloride solution, and extracted with ethyl acetate. The organic
layer was washed with water and brine and dried over anhydrous
magnesium sulfate. After concentration in vacuo, the residue was
over silica gel. Elution with hexanes/ethyl acetate (4:1) gave 10
25
(1.10 g, 86% in two steps) as a colorless oil. nD¼1.5049. [
1.0, CHCl3). IR (film):
1009 cmꢀ1 1H NMR (300 MHz, DMSO-d6, 90 ꢁC):
a]
þ5 (c
chromatographed over silica gel. Elution with hexanes/acetone (3:1
D
21
n
¼1685, 1611, 1510, 1341, 1233, 1152,
¼0.08 (3H, s),
to 1:1) gave 13 (63 mg, 76%) as a colorless oil. nD¼1.4978. [
a]
þ3.5
D
.
d
(c 1.0, CHCl3). IR (Nujol):
NMR (300 MHz, CDCl3):
n
¼1752, 1612, 1512, 1236, 1152 cmꢀ1
.
1H
0.09 (3H, s), 0.89 (9H, s), 1.16 (9H, br s), 1.60–1.70 (2H, m), 1.82–2.00
(2H, m), 2.65 (1H, m), 2.70 (3H, s), 2.81 (1H, dd, J¼14.4, 11.1 Hz),
3.36 (3H, s), 3.78 (2H, m), 3.92 (1H, q, J¼5.4 Hz), 4.21 (1H, m), 5.10
(2H, s), 6.90 (2H, d, J¼8.4 Hz), 7.07 (2H, d, J¼8.4 Hz), 7.60–7.75 (5H,
m). ESI-TOFMS m/z calcd for C33H51N5NaO7SSi [MþNa]þ 712.3171,
found 712.3182.
d
¼0.00 (6H, s), 0.85 (9H, s), 1.35–1.6 (4H,
m), 2.66 (1H, dd, J¼13.8, 7.8 Hz), 2.86 (3H, s), 3.01 (1H, dd, J¼13.8,
4.5 Hz), 3.42–3.58 (3H, m), 3.48 (3H, s), 4.15 (1H, m), 5.16 (2H, s),
6.99 (2H, d, J¼8.7 Hz), 7.06 (2H, d, J¼8.7 Hz). ESI-TOFMS m/z calcd
for C22H37NNaO5Si [MþNa]þ 446.2333, found 446.2338.
3.2.12. tert-Butyl (1R,2S)-[2,5-bis(tert-butyldimethylsilyloxy)-1-[4-
(methoxymethoxy)benzyl]pentyl]methylcarbamate (17)
3.2.9. tert-Butyl (1R,2R,5E,7S,9S)-[2-(tert-butyldimethylsilyloxy)-1-
[4-(methoxymethoxy)benzyl]-7,9-dimethylundec-5-enyl]methyl-
carbamate (12)
To a solution of amide 5 (3.36 g, 8.79 mmol) in ether (100 ml) was
added dropwise a solution of DIBAL in hexane (1.02 M, 9.0 ml,
9.18 mmol) at ꢀ20 ꢁC and the resulting mixture was stirred for 2 h at
20 ꢁC. The reaction mixture was poured into ice-cold saturated
aqueous potassium sodium tartrate solution and stirred for 30 min
at 0 ꢁC. Then the mixture was allowed to warm to room temperature
and extracted with ether. The organic layer was washed with water
Under argon atmosphere, to a solution of sulfone 10 (300 mg,
0.43 mmol) in THF (8 ml) was added KHMDS solution in toluene
(0.5 M, 870
m
l, 0.44 mmol) at ꢀ78 ꢁC. After stirring for 2 min, the
solution of aldehyde 11 (111 mg, 0.87 mmol) in THF (2 ml) was
added to the reaction mixture. The resulting mixture was then

K. Ishigami et al. / Tetrahedron 65 (2009) 3629–3638
3635
and brine. After drying over anhydrous magnesium sulfate, the so-
lution was concentrated in vacuo. The residue was solved in ether
and filtered through silica gel. After washing with ether, the com-
bined solution was concentrated to give crude aldehyde 15 (2.44 g)
as a colorless oil. This material was used for next reaction without
further purification. Small amount of crude aldehyde was analyzed
by HPLC [column: Daicel Chiralpak AD-H (0.46 cmꢂ25 cm), eluent:
hexane/i-PrOH (19:1), flow rate: 0.8 ml/min, detection: UV
(254 nm), (S)-isomer:tR¼11.8 min, (R)-isomer: tR¼12.9 min]and the
enantiomeric purity was determined to be 97% ee.
To a solution of 1-(tert-butyldimethylsilyloxy)-3-iodopropane
(3.75 g, 12.5 mmol) in ether (50 ml) was slowly added a solution of
t-BuLi in pentane (1.58 M, 16.2 ml, 25.8 mmol) at ꢀ78 ꢁC and the
resulting mixture was stirred for 1 h at same temperature. The
resultant solution of lithium reagent was added to a solution of
crude aldehyde (2.25 g) in ether (80 ml) at ꢀ78 ꢁC and the reaction
mixture was slowly warmed to room temperature. After stirring for
1 h, it was poured into saturated aqueous ammonium chloride
solution and extracted with ether. The organic layer was washed
with water and brine, and dried over anhydrous magnesium sul-
fate. After concentration in vacuo, the residue was chromato-
graphed over silica gel. Elution with hexanes/ethyl acetate (5:1)
gave an inseparable mixture of 16 and 7 (3.04 g, 75% in two steps)
as a slightly yellow oil. This mixture was used for next reaction
without further purification.
(1.98 M, 804 ml, 1.59 mmol), PPh3 (417 mg, 1.59 mmol), and 5-mer-
capto-1-phenyl-1H-tetrazole (283 mg, 1.59 mmol) at 0 ꢁC. After
stirring for 1 h at room temperature, the reaction mixture was
concentrated in vacuo. The residue was chromatographed over
silica gel and elution with hexanes/ethyl acetate (4:1) gave crude
sulfide (1.3 g). To a solution of this crude material in 95% EtOH
(30 ml) were added ammonium molybdate tetrahydrate (160 mg,
0.13 mmol) and 35% hydrogen peroxide solution (1.5 ml) at 0 ꢁC.
The mixture was stirred for 24 h at room temperature and poured
into 10% Na2S2O3 solution. It was extracted with EtOAc and the
organic layer was washed with brine. The organic layer was dried
over anhydrous sodium sulfate and concentrated in vacuo. The
residue was chromatographed over silica gel. Elution with hexanes/
ethyl acetate (4:1) gave 19 (759 mg, 83% in two steps) as a colorless
26
oil. nD¼1.5010. [
a
]
D
þ6.6 (c 1.0, CHCl3). IR (film): ¼1690, 1612,
n
1510, 1345, 1233, 1152, 1081, 1010 cmꢀ1. 1H NMR (300 MHz, DMSO-
d6, 90 ꢁC):
d
¼0.11 (3H, s), 0.13 (3H, s), 0.91 (9H, s), 1.19 (9H, br s),
1.51–1.75 (2H, m), 1.84–2.00 (2H, m), 2.59 (3H, s), 2.61 (1H, m), 2.96
(1H, m), 3.36 (3H, s), 3.74 (2H, t, J¼7.5 Hz), 3.87–4.03 (2H, m), 5.10
(2H, s), 6.90 (2H, d, J¼8.4 Hz), 7.03 (2H, d, J¼8.4 Hz), 7.55–7.77 (5H,
m). ESI-TOFMS m/z calcd for C33H51N5NaO7SSi [MþNa]þ 712.3171,
found 712.3169.
3.2.15. tert-Butyl (1R,2S,5E,7S,9S)-[2-(tert-butyldimethylsilyloxy)-
1-[4-(methoxymethoxy)benzyl]-7,9-dimethylundec-5-
To a solution of crude mixture of 16 and 7 (1.59 g) in dichloro-
methane (50 ml) was added 2,6-lutidine (0.93 ml, 8.0 mmol) fol-
lowed by TBSOTf (0.88 ml 3.8 mmol) at 0 ꢁC. After stirring for 3 h, the
reaction mixture was poured into saturated aqueous ammonium
chloride solution, and extracted with ether. The organic layer was
washed with 1 N HCl, saturated aqueous sodium bicarbonate solu-
tion, water, and brine, and then dried over anhydrous magnesium
sulfate. After concentration in vacuo, the residue was chromato-
graphed over silica gel. Elution with hexanes/ethyl acetate (20:1)
enyl]methylcarbamate (20)
Under argon atmosphere, to a solution of sulfone 19 (321 mg,
0.47 mmol) in THF (10 ml) was added a solution of KHMDS in tol-
uene (0.5 M, 1.1 ml, 0.56 mmol) at ꢀ78 ꢁC. After stirring for 2 min,
a solution of aldehyde 11 (119 mg, 0.93 mmol) in THF (5 ml) was
added to the reaction mixture and it was stirred for another 5 min
at same temperature. The reaction mixture was then allowed to
warm to room temperature. This solution was poured into satu-
rated aqueous ammonium chloride solution and extracted with
ether. The organic layer was washed with water and brine. After
drying over anhydrous magnesium sulfate, the solution was con-
centrated in vacuo. The residue was chromatographed over silica
gave 17 (1.30 g, 50% in three steps) and 8 (0.28 g,10.8% in three steps)
22
as colorlessoils. nD¼1.4741. [
a
]
D
þ21 (c 1.0, CHCl3). IR (film):
n
¼1695,
1613, 1514, 1254 cmꢀ1. 1H NMR (300 MHz, DMSO-d6, 90 ꢁC):
d
¼0.02
(6H, s), 0.12 (3H, s), 0.12 (3H, s), 0.87 (9H, s), 0.93 (9H, s), 1.22 (9H, br
s),1.40–1.65 (4H, m), 2.59 (3H, s), 2.67(1H, m), 2.95 (1H, m), 3.36 (3H,
s), 3.57 (2H, t, J¼6.0 Hz), 3.94 (1H, m), 3.98 (1H, m), 5.10 (2H, s), 6.90
(2H, d, J¼8.4 Hz), 7.03 (2H, d, J¼8.4 Hz). ESI-TOFMS m/z calcd for
C32H61NNaO6Si2 [MþNa]þ 634.3930, found 634.3934.
gel. Elution with hexanes/ethyl acetate (8:1) gave 20 (200 mg, 73%)
23
as a colorless oil. nD¼1.4791. [
a
]
þ37 (c 1.0, CHCl3). IR (film):
D
n
¼1694, 1613, 1513, 1234, 1153, 1011 cmꢀ1
.
1H NMR (300 MHz,
DMSO-d6, 90 ꢁC):
d
¼0.12 (6H, s), 0.81 (3H, d, J¼6.6 Hz), 0.81 (3H, t,
J¼7.2 Hz), 0.91 (3H, d, J¼6.6 Hz), 0.93 (9H, s), 1.00 (1H, ddd, J¼13.2,
7.4, 5.4 Hz), 1.04–1.40 (4H, m), 1.22 (9H, br s), 1.48 (1H, m), 1.58 (1H,
m), 2.03–2.21 (3H, m), 2.60 (3H, s), 2.61 (1H, m), 2.95 (1H, m), 3.36
(3H, s), 3.90 (1H, ddd, J¼8.4, 4.2, 4.2 Hz), 4.02 (1H, m), 5.10 (2H, s),
5.24 (1H, dd, J¼15.3, 7.5 Hz), 5.34 (1H, dt, J¼15.3, 6.3 Hz), 6.90 (2H,
d, J¼8.4 Hz), 7.03 (2H, d, J¼8.4 Hz). ESI-TOFMS m/z calcd for
C34H61NNaO5Si [MþNa]þ 614.4211, found 614.4246.
3.2.13. tert-Butyl (1R,2S)-[2-(tert-butyldimethylsilyloxy)-5-
hydroxy-1-[4-(methoxymethoxy)benzyl]pentyl]methyl-
carbamate (18)
Dowex-50 (0.25 g) was washed with deionized water three
times. To a solution of TBS ether 17 (1.10 g, 1.80 mmol) in MeOH
(50 ml) was added a suspension of Dowex-50 in deionized water
(5 ml) and stirred for 36 h at room temperature. After filtration,
3.2.16. (2R,3S,6E,8S,10S)-1-(4-Hydroxyphenyl)-8,10-dimethyl-2-
(methylamino)dodec-6-en-3-ol (ent-2)
triethylamine (300 ml) was added to the filtrate. After concentration
in vacuo, the residue was chromatographed over silica gel. Elution
To a solution of 20 (58 mg, 0.13 mmol) in THF (2 ml), MeOH
with hexanes/ethyl acetate (5:1 to 1:1) gave 18 (0.67 g, 75%) as
(1 ml), and water (1 ml) was added trifluoroacetic acid (100 ml) and
24
a colorless oil. nD¼1.4882. [
a
]
þ34 (c 1.0, CHCl3). IR (film):
the mixture was stirred for 48 h at room temperature. The reaction
mixture was concentrated at 50 ꢁC in vacuo. The residue was
chromatographed over silica gel. Elution with chloroform/MeOH
D
n
¼3444, 1694, 1613, 1512, 1233, 1153 cmꢀ1
.
1H NMR (300 MHz,
DMSO-d6, 90 ꢁC):
d¼0.12 (6H, s), 0.94 (9H, s), 1.23 (9H, br s), 1.36–
1.62 (4H, m), 2.59 (3H, s), 2.63 (1H, m), 2.86 (1H, m), 3.30–3.44 (2H,
m), 3.36 (3H, s), 3.93 (1H, m), 4.02 (1H, m), 5.10 (2H, s), 6.90 (2H, d,
J¼8.4 Hz), 7.07 (2H, d, J¼8.4 Hz). ESI-TOFMS m/z calcd for
C26H47NNaO6Si [MþNa]þ 520.3065, found 520.3090.
(7:1) followed by recrystallization from hexanes/ether gave ent-2
25
(28 mg, 86%) as colorless needles. Mp¼122–127 ꢁC. [
a]
þ20 (c
D
0.35, CH3OH). IR (KBr):
n
¼3239, 2961, 1671, 1203, 1185, 1146 cmꢀ1
.
1H NMR (500 MHz, CD3OD):
d
¼0.82 (3H, d, J¼6.5 Hz), 0.84 (3H, t,
J¼7.3 Hz), 0.91 (3H, d, J¼6.8 Hz), 0.99 (1H, ddd, J¼13.5, 9.7, 4.8 Hz),
1.13 (1H, m), 1.22 (1H, ddd, J¼13.5, 9.7, 4.8 Hz), 1.25–1.35 (2H, m),
1.45–1.6 (2H, m), 1.99 (1H, m), 2.1–2.25 (2H, m), 2.62 (3H, s), 2.86
(1H, dd, J¼14.7, 7.9 Hz), 2.91 (1H, dd, J¼14.7, 7.0 Hz), 3.34 (1H, ddd,
J¼7.9, 7.0, 3.0 Hz), 3.83 (1H, ddd, J¼9.4, 3.6, 3.0 Hz), 5.22 (1H, dd,
J¼15.5, 8.3 Hz), 5.33 (1H, dt, J¼15.5, 6.7 Hz), 6.78 (2H, quasi d,
3.2.14. tert-Butyl (1R,2S)-[2-(tert-butyldimethylsilyloxy)-1-[4-
(methoxymethoxy)benzyl]-5-[(1-phenyl-1H-tetrazol-5-
yl)sulfonyl]pentyl]methylcarbamate (19)
To a solution of alcohol 18 (660 mg, 1.33 mmol) in THF (30 ml)
was added a solution of diethyl azodicarboxylate in toluene

3636
K. Ishigami et al. / Tetrahedron 65 (2009) 3629–3638
J¼8.5 Hz), 7.10 (2H, quasi d, J¼8.5 Hz). 13C NMR (125 MHz, CD3OD):
2.85 (1H, dd, J¼14.4, 7.2 Hz), 2.86 (1H, dd, J¼14.4, 7.2 Hz), 3.38 (3H,
s), 3.52–3.72 (2H, m), 3.97 (1H, q, J¼7.2 Hz), 4.50 (1H, m), 5.16 (2H,
s), 6.99 (2H, d, J¼8.4 Hz), 7.14 (2H, d, J¼8.4 Hz). ESI-TOFMS m/z calcd
for C22H37NNaO5Si [MþNa]þ 446.2333, found 446.2347.
d
¼11.7, 19.4, 22.3, 29.9, 31.1, 32.4, 33.1, 33.2, 35.8, 45.6, 66.8, 68.7,
116.9, 127.6, 128.4, 131.3, 138.8, 158.0. ESI-TOFMS m/z calcd for
C21H36NO2 [MþH]þ 334.2741, found 334.2763.
3.2.17. tert-Butyl (1R,2S,5E,7R,9R)-[2-(tert-butyldimethylsilyloxy)-
1-[4-(methoxymethoxy)benzyl]-7,9-dimethylundec-5-
enyl]methylcarbamate (21)
3.2.20. Methyl (S)-N-(tert-butoxycarbonyl)-O-(methoxymethyl)-
tyrosinate (ent-3)
In the same manner as the synthesis of 3 described above,
Under argon atmosphere, to a solution of sulfone 19 (126 mg,
0.18 mmol) in THF (5 ml) was added a solution of KHMDS in toluene
L-tyrosine (25.5 g, 140 mmol) was subjected to esterification, Boc-
protection, and MOM-protection to give ent-3 (40.9 g, 99% in three
21
(0.5 M, 438
m
l, 0.22 mmol) at ꢀ78 ꢁC. After stirring for 2 min, a so-
steps) as colorless prisms. Mp¼67–70 ꢁC. [
a
]
þ46 (c 1.0, CHCl3). Its
D
lution of aldehyde ent-11 (47 mg, 0.37 mmol) in THF (2 ml) was
added to the reaction mixture and it was stirred for another 5 min
at same temperature. The reaction mixture was then allowed to
warm to room temperature. This mixture was poured into satu-
rated aqueous ammonium chloride solution and extracted with
ether. The organic layer was washed with water and brine. After
drying over anhydrous magnesium sulfate, the solution was con-
centrated in vacuo. The residue was chromatographed over silica
IR and 1H NMR spectra were identical with those of 3. ESI-TOFMS
m/z calcd for C17H25NNaO6 [MþNa]þ 362.1574, found 362.1612.
3.2.21. (S)-N-a-(tert-Butoxycarbonyl)-N-methoxy-O-(methoxy-
methyl)-N-methyltyrosinamide (ent-4)
In the same manner as the synthesis of 4 described above, ester
ent-3 (8.48 g, 25.0 mmol) was treated with N,O-dimethylhydroxy-
lamine hydrochloride (5.36 g, 55.0 mmol) in THF (250 ml) in the
gel. Elution with hexanes/ethyl acetate (8:1) gave 21 (60 mg, 56%)
presence of isopropyl magnesium bromide to give ent-4 (7.97 g,
24
21
as a colorless oil. nD¼1.4779. [
a
]
D
þ14 (c 1.0, CHCl3). IR (film):
87%) as colorless prisms. Mp¼68–71 ꢁC. [
a
]
þ19 (c 1.0, CHCl3). Its
D
n
¼1694, 1613, 1512, 1234, 1154, 1010 cmꢀ1
.
1H NMR (300 MHz,
IR and 1H NMR spectra were identical with those of 4. ESI-TOFMS
m/z calcd for C18H28N2NaO6 [MþNa]þ 391.1840, found 391.1890.
DMSO-d6, 90 ꢁC):
d
¼0.12 (6H, s), 0.81 (3H, d, J¼6.0 Hz), 0.82 (3H, t,
J¼7.2 Hz), 0.91 (3H, d, J¼7.2 Hz), 0.93 (9H, s), 1.00 (1H, ddd, J¼13.2,
8.4, 5.7 Hz), 1.04–1.39 (4H, m), 1.23 (9H, br s), 1.42–1.56 (2H, m),
2.01–2.22 (3H, m), 2.60 (3H, s), 2.61 (1H, m), 2.95 (1H, m), 3.36 (3H,
s), 3.91 (1H, ddd, J¼8.4, 3.6, 3.6 Hz), 4.05 (1H, m), 5.10 (2H, s), 5.25
(1H, dd, J¼15.6, 7.5 Hz), 5.34 (1H, dt, J¼15.6, 6.3 Hz), 6.90 (2H, d,
J¼8.4 Hz), 7.03 (2H, d, J¼8.4 Hz). ESI-TOFMS m/z calcd for
C34H61NNaO5Si [MþNa]þ 614.4211, found 614.4234.
3.2.22. (S)-N-
(methoxymethyl)-N,N-
In the same manner as the synthesis of 4 described above, ent-4
(6.91 g, 18.8 mmol) was treated with NaH (0.79 g, 19.7 mmol), MeI
a
-(tert-Butoxycarbonyl)-N-methoxy-O-
a-dimethyltyrosinamide (ent-5)
(1.75 ml, 28.2 mmol) in DMF (80 ml), and THF (5 ml) to give ent-5
21
(6.78 g, 95%) as colorless prisms. Mp¼40–44 ꢁC. [
a
]
ꢀ103 (c 1.0,
D
CHCl3). Its IR and 1H NMR spectra were identical with those of 5.
ESI-TOFMS m/z calcd for C19H30N2NaO6 [MþNa]þ 405.1996, found
405.1989.
3.2.18. (2R,3S,6E,8R,10R)-1-(4-Hydroxyphenyl)-8,10-dimethyl-2-
(methylamino)dodec-6-en-3-ol (ent-14)
To a solution of 21 (40 mg, 0.07 mmol) in THF (1 ml), MeOH
(0.5 ml), and water (0.5 ml) was added trifluoroacetic acid (300
m
l)
3.2.23. tert-Butyl (1S,2R)-[2,5-bis(tert-butyldimethylsilyloxy)-1-
[4-(methoxymethoxy)benzyl]pentyl]methylcarbamate (ent-17)
To a solution of amide ent-5 (3.83 g,10.0 mmol) inTHF (75 ml) was
added lithium aluminum hydride (0.38 g, 10.0 mmol) at 0 ꢁC. After
stirring for 1 h at same temperature, the reaction mixture was cooled
down to ꢀ70 ꢁC. Saturated aqueous ammonium chloride solution
(30 ml) was added to the reaction mixture with vigorous stirring, and
the mixture was allowed to warm to room temperature. Dark gray
precipitates were filtered off through Celite and washed with ether.
After concentration, the residue was dissolved in ether and filtered
through silica gel. Concentration in vacuo gave crude aldehyde ent-15
(3.26 g) as a colorless oil. This material was used for next reaction
without further purification. Small amount of crude aldehyde was
analyzed by HPLC [column: Daicel Chiralpak AD-H (0.46 cmꢂ25 cm),
eluent: hexane/i-PrOH (19:1), flow rate: 0.8 ml/min, detection: UV
(254 nm), (S)-isomer: tR¼11.8 min, (R)-isomer: tR¼12.9 min] and the
enantiomeric purity was determined to be >99% ee.
To a solution of 1-(tert-butyldimethylsilyloxy)-3-iodopropane
(6.34 g, 21.1 mmol) in ether (100 ml) was slowly added a solution of
t-BuLi in pentane (1.58 M, 26.5 ml, 42.1 mmol) at ꢀ78 ꢁC and the
resulting mixture was stirred for 1 h at same temperature. The
resultant solution of lithium reagent was added to a solution of
crude aldehyde (3.25 g) in ether (50 ml) at ꢀ78 ꢁC and the reaction
mixture was slowly warmed to room temperature. After stirring for
1 h, it was poured into saturated aqueous ammonium chloride
solution and extracted with ethyl acetate. The organic layer was
washed with water and brine, and dried over anhydrous magne-
sium sulfate. After concentration in vacuo, the residue was chro-
matographed over silica gel. Elution with hexanes/ethyl acetate
(5:1) gave inseparable mixture of ent-16 and ent-7 (3.47 g) as
slightly yellow oil. This mixture was used for next reaction without
further purification.
and it was stirred for 48 h at room temperature. The reaction
mixture was concentrated at 50 ꢁC in vacuo. The residue was
chromatographed over silica gel. Elution with chloroform/MeOH
(7:1) followed by recrystallization from hexanes/ether gave ent-14
24
(20 mg, 89%) as colorless needles. Mp¼95–98 ꢁC. [
a]
ꢀ13 (c 0.35,
D
CH3OH). IR (KBr):
n
¼3232, 2961, 1672, 1241, 1186, 1146 cmꢀ1
.
1H
NMR (500 MHz, CD3OD):
d
¼0.81 (3H, d, J¼6.5 Hz), 0.85 (3H, t,
J¼7.3 Hz), 0.92 (3H, d, J¼6.8 Hz), 0.99 (1H, ddd, J¼13.5, 9.0, 5.3 Hz),
1.13 (1H, m), 1.24 (1H, ddd, J¼13.5, 9.6, 4.3 Hz), 1.24–1.35 (2H, m),
1.45–1.6 (2H, m), 2.00 (1H, m), 2.11–2.24 (2H, m), 2.62 (3H, s), 2.86
(1H, dd, J¼14.7, 7.9 Hz), 2.93 (1H, dd, J¼14.7, 7.0 Hz), 3.35 (1H, ddd,
J¼7.9, 7.0, 2.8 Hz), 3.84 (1H, ddd, J¼9.0, 4.3, 2.8 Hz), 5.23 (1H, dd,
J¼15.5, 8.2 Hz), 5.35 (1H, dt, J¼15.5, 6.7 Hz), 6.78 (2H, quasi d,
J¼8.5 Hz), 7.11 (2H, quasi d, J¼8.5 Hz). 13C NMR (125 MHz, CD3OD):
d
¼11.7, 19.4, 22.3, 29.9, 31.1, 32.4, 33.1, 33.2, 35.8, 45.6, 66.8, 68.7,
116.9, 127.6, 128.4, 131.3, 138.8, 158.0. ESI-TOFMS m/z calcd for
C21H36NO2 [MþH]þ 334.2741, found 334.2756.
3.2.19. (4R,5S)-5-[3-(tert-Butyldimethylsilyloxy)propyl]-4-[4-
(methoxymethoxy)benzyl]-3-methyl-1,3-oxazolidin-2-one (22)
To a solution of amino alcohol 16 (40 mg, 0.08 mmol) in THF
(3 ml) was added NaH (5 mg, 0.13 mmol) at room temperature and
it was stirred for 16 h under reflux. The reaction mixture was
poured into saturated aqueous ammonium chloride solution, and
extracted with ethyl acetate. The organic layer was washed with
water and brine and dried over anhydrous magnesium sulfate. After
concentration in vacuo, the residue was chromatographed over
silica gel. Elution with hexanes/acetone (3:1 to 1:1) gave 22 (23 mg,
18
68%) as a colorless oil. nD¼1.4978. [
a]
þ5.9 (c 1.0, CHCl3). IR
D
(Nujol):
CDCl3):
n
1747, 1611, 1512, 1234, 1152 cmꢀ1
¼0.02 (6H, s), 0.87 (9H, s), 1.45–1.85 (4H, m), 2.64 (3H, s),
.
1H NMR (300 MHz,
d

K. Ishigami et al. / Tetrahedron 65 (2009) 3629–3638
3637
To a solution of crude mixture of ent-16 and ent-7 (1.00 g) in
dichloromethane (30 ml) was added 2,6-lutidine (0.94 ml,
8.0 mmol) followed by TBSOTf (0.92 ml 4.0 mmol) at 0 ꢁC. After
stirring for 3 h, the reaction mixture was poured into saturated
aqueous ammonium chloride solution, and extracted with ether.
The organic layer was washed with 1 N HCl, saturated aqueous
sodium bicarbonate solution, water and brine, and then dried over
anhydrous magnesium sulfate. After concentration in vacuo, the
residue was chromatographed over silica gel. Elution with hexanes/
J¼8.5 Hz). 13C NMR (125 MHz, CD3OD):
d
¼11.7, 19.4, 22.3, 29.9,
31.1, 32.4, 33.1, 33.2, 35.8, 45.6, 66.8, 68.7, 116.9, 127.6, 128.4, 131.3,
138.8, 158.0. ESI-TOFMS m/z calcd for C21H36NO2 [MþH]þ
334.2741, found 334.2740.
3.2.28. (2S,3R,6E,8S,10S)-1-(4-Hydroxyphenyl)-8,10-dimethyl-2-
(methylamino)dodec-6-en-3-ol (14)
In the same manner as the synthesis of 21 described above, ent-
19 (154 mg, 0.22 mmol) was treated with a solution of KHMDS in
ethyl acetate (20:1) gave ent-17 (0.89 g, 51% in three steps) and ent-
toluene (0.5 M, 536 ml, 0.27 mmol) and aldehyde 11 (58 mg,
0.45 mmol) in THF (8 ml) to give ent-21 (76 mg, 58%) as colorless
26
8 (0.07 g, 4% in three steps) as colorless oils. nD¼1.4728. [
a
]
ꢀ27 (c
D
24
1.0, CHCl3). IR and 1H NMR spectra of ent-17 were identical with
those of 17. ESI-TOFMS m/z calcd for C32H61NNaO6Si2 [MþNa]þ
634.3930, found 634.3949.
oil. nD¼1.4789. [
a
]
D
ꢀ15 (c 1.0, CHCl3). Its IR and 1H NMR spectra
were identical with those of 21. ESI-TOFMS m/z calcd for
C34H61NNaO5Si [MþNa]þ 614.4211, found 614.4227.
In the same manner as the synthesis of ent-14 described above,
the solution of ent-21 (60 mg, 0.10 mmol) in THF (2 ml), MeOH
(1 ml), and water (1 ml) was treated with trifluoroacetic acid
3.2.24. tert-Butyl (1S,2R)-[2-(tert-butyldimethylsilyloxy)-5-
hydroxy-1-[4-(methoxymethoxy)benzyl]pentyl]methylcarbamate
(ent-18)
In the same manner as the synthesis of 18 described above, ent-
17 (820 mg, 1.34 mmol) was treated with Dowex-50 (0.2 g) in
(300
m
l) to give 14 (24 mg, 71%) as colorless needles. Mp¼97–99 ꢁC.
25
[a
]
þ11 (c 0.35, CH3OH). Its IR and 1H NMR spectra were identical
D
with those of ent-14. ESI-TOFMS m/z calcd for C21H36NO2 [MþH]þ
MeOH (25 ml) and water (3 ml) to give ent-18 (548 mg, 82%) as
334.2741, found 334.2758.
26
a colorless oil. nD¼1.4863. [
a
]
ꢀ36 (c 1.0, CHCl3). Its IR and 1H
D
NMR spectra were identical with those of 18. ESI-TOFMS m/z calcd
for C26H47NNaO6Si [MþNa]þ 520.3065, found 520.3089.
3.2.29. (2S,3R,6E)-1-(4-Hydroxyphenyl)-2-(methylamino)dodec-6-
en-3-ol (23)
In a similar manner to the synthesis of ent-2 via 20, ent-19
(70 mg, 0.10 mmol) was treated with a solution of KHMDS in tol-
3.2.25. tert-Butyl (1S,2R)-[2-(tert-butyldimethylsilyloxy)-1-[4-
(methoxymethoxy)benzyl]-5-[(1-phenyl-1H-tetrazol-5-
uene (0.5 M, 243 ml, 0.12 mmol) and 1-hexanal (25 ml, 0.20 mmol)
yl)sulfonyl]pentyl]methylcarbamate (ent-19)
in THF (5 ml) to give crude coupled product (20 mg) as a slightly
yellow oil. A solution of crude coupled product (20 mg) in THF
(2 ml), MeOH (1 ml), and water (1 ml) was treated with trifluoro-
In the same manner as the synthesis of 19 described above,
ent-18 (447 mg, 0.90 mmol) was reacted with 5-mercapto-1-
phenyl-1H-tetrazole (241 mg, 1.35 mmol) in THF (30 ml) under
Mitsunobu condition to give crude sulfide (0.6 g). This crude
sulfide (0.6 g) was treated with ammonium molybdate tetrahy-
drate (250 mg, 0.20 mmol) and 35% aqueous hydrogen peroxide
acetic acid (300
m
l) to give 23 (3.5 mg, 11% in two steps) as a col-
orless oil. 1H NMR (500 MHz, CD3OD):
d
¼0.89 (3H, t, J¼7.0 Hz),
1.24–1.37 (6H, m), 1.43–1.60 (2H, m), 1.93–2.04 (3H, m), 2.19 (1H,
m), 2.58 (3H, s), 2.83 (1H, dd, J¼14.7, 7.9 Hz), 2.87 (1H, dd, J¼14.7,
7.0 Hz), 3.24 (1H, m), 3.80 (1H, dt, J¼9.0, 3.5 Hz), 5.38 (1H, dt,
J¼15.5, 6.2 Hz), 5.44 (1H, dt, J¼15.5, 6.0 Hz), 6.77 (2H, quasi d,
J¼8.5 Hz), 7.09 (2H, quasi d, J¼8.5 Hz). ESI-TOFMS m/z calcd for
C19H32NO2 [MþH]þ 306.2428, found 306.2462.
solution (2 ml) in 95% EtOH (30 ml) to give ent-19 (512 mg, 83% in
26
two steps) as a colorless oil. nD¼1.5033. [
a
]
ꢀ5.7 (c 1.0, CHCl3).
D
Its IR and 1H NMR spectra were identical with those of 19. ESI-
TOFMS m/z calcd for C33H51N5NaO7SSi [MþNa]þ 712.3171, found
712.3147.
3.3. Biological studies
3.2.26. tert-Butyl (1S,2R,5E,7R,9R)-[2-(tert-butyldimethylsilyloxy)-
1-[4-(methoxymethoxy)benzyl]-7,9-dimethylundec-5-
enyl]methylcarbamate (ent-20)
In the same manner as the synthesis of 20 described above, ent-
19 (195 mg, 0.28 mmol) was treated with a solution of KHMDS in
MCF-7 human breast cancer cells were provided by Dr. Shin-
Ichiro Takahashi (Departments of Animal Sciences and Applied
Biological Chemistry, Graduate School of Agriculture and Life Sci-
ences, The University of Tokyo). The cells were maintained in
Dulbecco’s modified Eagle’s medium (DMEM) supplemented with
10% heat-inactivated fetal bovine serum (FBS) and were grown at
37 ꢁC in a humidified atmosphere of 5% CO2. Cell proliferation as-
says were carried out in serum-free DMEM containing 0.1% bovine
serum albumin (Sigma) and 30 ng/ml recombinant human insulin-
like growth factor-1 (IGF-1, Sigma) and DMEM containing 0.5% FBS.
The cells were plated in each well of 96-well plates at the density of
5ꢂ104 cells/ml. After incubation with various concentrations of
toluene (0.5 M, 678 ml, 0.34 mmol) and aldehyde ent-11 (73 mg,
0.57 mmol) in THF (10 ml) to give ent-20 (117 mg, 70%) as colorless
25
oil. nD¼1.4789. [
a]
ꢀ41 (c 1.0, CHCl3). Its IR and 1H NMR spectra
D
were identical with those of 20. ESI-TOFMS m/z calcd for
C34H61NNaO5Si [MþNa]þ 614.4211, found 614.4234.
3.2.27. (2S,3R,6E,8R,10R)-1-(4-Hydroxyphenyl)-8,10-dimethyl-2-
(methylamino)dodec-6-en-3-ol (2, revised structure of tyroscherin)
In the same manner as the synthesis of ent-2 described above,
the solution of ent-20 (98 mg, 0.17 mmol) in THF (2 ml), MeOH
(1 ml), and water (1 ml) was treated with trifluoroacetic acid
samples at 37 ꢁC for 72 h, the cells were treated with 0.5
mg/ml
of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide
(MTT) at 37 ꢁC for 4 h. Relative cell number was measured with
formazan formation at 540 nm using a microplate reader (SUNRISE
Remote, TECAN Inc.). IC50 values were calculated by linear in-
terpolation between the two drug concentrations above and below
the 50% inhibition line.
(100
126 ꢁC. [
1203, 1185, 1146 cmꢀ1. 1H NMR (500 MHz, CD3OD):
m
l) to give 2 (48 mg, 87%) as a colorless needle. Mp¼122–
25
a]
ꢀ21 (c 0.35, CH3OH). IR (KBr):
n
¼3239, 2961, 1671,
¼0.82 (3H, d,
D
d
J¼6.5 Hz), 0.84 (3H, t, J¼7.3 Hz), 0.91 (3H, d, J¼6.8 Hz), 0.99 (1H,
ddd, J¼13.5, 9.7, 4.8 Hz), 1.13 (1H, m), 1.22 (1H, ddd, J¼13.5, 9.7,
4.8 Hz), 1.25–1.35 (2H, m), 1.45–1.6 (2H, m), 1.99 (1H, m), 2.1–2.25
(2H, m), 2.62 (3H, s), 2.86 (1H, dd, J¼14.7, 7.9 Hz), 2.91 (1H, dd,
J¼14.7, 7.0 Hz), 3.34 (1H, ddd, J¼7.9, 7.0, 3.0 Hz), 3.83 (1H, ddd,
J¼9.4, 3.6, 3.0 Hz), 5.22 (1H, dd, J¼15.5, 8.3 Hz), 5.33 (1H, dt,
J¼15.5, 6.7 Hz), 6.78 (2H, quasi d, J¼8.5 Hz), 7.10 (2H, quasi d,
Acknowledgements
This work was partly supported by a Grant-in-Aid for Scientific
Research from the Japanese Ministry of Education, Culture, Sports,
Science and Technology.

3638
K. Ishigami et al. / Tetrahedron 65 (2009) 3629–3638
6. Reetz, M. T.; Drewes, M. W.; Lennick, K.; Schmitz, A.; Holdgru¨n, X. Tetrahedron:
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