Total synthesis of cyclodepsipeptide spiruchostatin A on silyl-linked polymer-support

Article abstract of DOI:10.1016/j.tet.2015.07.064

Solid-phase total synthesis of cyclodepsipeptide spiruchostatin A (1) has been achieved. Initially, immobilization of the Boc-d-Val-statine derivative 3 via the hindered β-hydroxy group was efficiently achieved using polymer-supported silyl triflate. Subs

Full text of DOI:10.1016/j.tet.2015.07.064

Accepted Manuscript
Total synthesis of cyclodepsipeptide spiruchostatin A on silyl-linked polymer-support
Masahito Yoshida, Ken-ichi Sasahara, Takayuki Doi
PII:
S0040-4020(15)01141-2
10.1016/j.tet.2015.07.064
TET 27009
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 10 July 2015
Revised Date: 24 July 2015
Accepted Date: 25 July 2015
Please cite this article as: Yoshida M, Sasahara K-i, Doi T, Total synthesis of cyclodepsipeptide
spiruchostatin A on silyl-linked polymer-support, Tetrahedron (2015), doi: 10.1016/j.tet.2015.07.064.
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Total
synthesis
of
cyclodepsipeptide
Leave this area blank for abstract info.
spiruchostatin A on silyl-linked polymer-
support
Masahito Yoshida, Ken-ichi Sasahara and Takayuki Doi
Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aza-Aoba, Aramaki, Aoba-ku, Sendai
980-8578, Japan
O
O
Et
Si
O
Et
Et
OH
1) Macrolactonization
on polymer-support
HN
N
Si
O
HN
N
H
O
Et
BocHN
H
O
S
O
S
2) Cleavage;
Disulfide formation
TrtS
STrt
O
NH
O
NH
O
OH
OAllyl
O
OH
O
Polymer-supported
Cyclization precursor 2
Spiruchostatin A (1)
Boc- -Val-statine derivative 5
D
17% overall yield
10 steps from polymer-supported
Boc- -Val-statine derivative 5
D

1
ACCEPTED MANUSCRIPT
Tetrahedron
journal homepage: www.elsevier.com
Total synthesis of cyclodepsipeptide spiruchostatin A on silyl-linked polymer-support
Masahito Yoshidaa, Ken-ichi Sasaharaa and Takayuki Doia, *
aGraduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aza-Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan
* Corresponding author. E-mail: doi_taka@mail.pharm.tohoku.ac.jp
ARTICLE INFO
ABSTRACT
Article history:
Received
Solid-phase total synthesis of cyclodepsipeptide spiruchostatin A (1) has been achieved.
Initially, immobilization of the Boc-D-Val-statine derivative 3 via the hindered β-hydroxy group
Received in revised form
Accepted
Available online
was efficiently achieved using polymer-supported silyl triflate. Subsequently, the peptide chain
was successfully extended on the polymer-support to yield the tetrapeptide cyclization precursor
2 with high purity. 2-Methyl-6-nitrobenzoic anhydride (MNBA)-mediated macrolactonization of
2 proceeded smoothly on the polymer-support to provide macrolactone 12. Finally, release of
the macrolactone from the polymer-support followed by in situ disulfide formation furnished
spiruchostatin A (1) in 17% overall yield.
Keywords:
Solid-phase synthesis
Silyl linker
Macrolactonization
Histone deacetylase
Cyclodepsipeptide
2009 Elsevier Ltd. All rights reserved
.
performed entirely on a polymer-support,9 allowing for the
combinatorial synthesis of spiruchostatin analogs, was
envisioned.10 Here we describe the solid-phase total synthesis of
spiruchostatin A (1), wherein 2-methyl-6-nitrobenzoic anhydride
(MNBA)-mediated macrolactonization was performed on the
polymer-supported intermediate and the final disulfide forming
reaction was performed in situ after cleaving the macrocycle
from the polymer-support.
1. Introduction
Histone deacetylases (HDACs) are attractive targets for cancer
therapy, because inhibition of HDACs can lead to apoptosis, cell
cycle arrest, and inhibition of angiogenesis and metastasis.1
Naturally occurring and synthetic HDAC inhibitors, such as
romidepsin (FK228),2 vorinostat (SAHA),3 and belinostat
(Beleodaq),4 have recently been approved for clinical use as
anticancer agents; several naturally occurring cyclodepsipeptides
exhibiting HDAC inhibitory activity have also been evaluated in
preclinical trials.5 These advances indicate that inhibitors of
HDAC activity can be viable candidates for the treatment of
cancer. Spiruchostatin A (1), isolated from Pseudomonas sp. by
Shin-ya et al. in 2001, is a 15-membered cyclodepsipeptide with
an intramolecular disulfide bond and exhibits potent HDAC
inhibitory activity (IC50 = 3.3 nM).6 The structure of 1 bears
similarities with that of the approved cyclodepsipeptide FK228;
therefore, 1 is an attractive lead compound for the development
of a drug for treating HDAC-dependent diseases. Because of its
unique biological activity, spiruchostatin A (1) has been the
target of total syntheses with efforts by our and other research
group(s).7, 8 We have synthesized 1 and its derivatives utilizing
both solution- and solid-phase synthesis, in addition to the use of
automated laboratory technologies.8 Our previous solid-phase
synthesis commenced with the immobilization of the C-terminus
2. Results and Discussion
The nature and position of the amino acid residue immobilized
on the polymer support is a critical factor that ensures the
successful total synthesis of 1 on the polymer-support. The
retrosynthetic scheme for the polymer-supported synthesis of 1 is
illustrated in Figure 1. We planned to immobilize the Boc-D-Val-
statine derivative 3 via the β-hydroxy group onto the polymer-
support using a trialkylsilyl linker,11 because the silyl linker can
be readily cleaved under mild acidic conditions without leading
to decomposition of the cleaved product.12, 13 Furthermore, such a
scheme allows for the use of the Boc group for the protection of
the amino group in 3, thereby precluding the formation of the
lactam under basic conditions. It is worth noting here that the
peptide chain on the polymer-support can be elongated either
from the N- or C-terminus of the
Based on our prior experience,8 we considered elongating the
peptide at the N-terminus of the immobilized -Val-statine
D-Val-statine derivative 3.
of the Fmoc-D-Val-statine derivative onto a polymer-support.
D
The advanced intermediate, i.e., the precursor for the cyclization
reaction, was prepared on the polymer-support using standard
peptide synthesis protocols and then cleaved prior to in-solution
cyclization. Therefore, the final macrolactonization and disulfide
formation steps were performed in a stepwise fashion in the
solution phase. Subsequently, a more concise synthesis of
derivative. We envisioned that elongation of the linear peptide on
the polymer-support followed by macrolactonization of 2 and
subsequent disulfide formation with concomitant cleavage from
the polymer-support will afford the desired spiruchostatin A (1).
spiruchostatin analogs incorporating
a
radioactive probe

2
Tetrahedron
3) Cleavage
2) Disulfide formation
HN
diisopropylethylamine (DIEA). Epimerization at the α-position
ACCEPTED MANUSCRIPT
of the cysteine residue or the formation of a 5-membered lactam
O
O
Et
Si
O
was not observed under these conditions (entry 4). Similar yields
were observed when the reaction was performed utilizing 1H-
benzotriazol-1-yloxy-tri(pyrrolidino)phosphonium
O
N
OH
HN
Et
N
H
O
H
O
TrtS
STrt
S
S
NH
O
hexafluorophosphate (PyBoP)16/DIEA (entry 3). Further
investigations revealed that when utilizing HATU/DIEA, the
reaction was completed within 3 h and the desired intermediate 6
was obtained in 85% yield (entry 5).17
NH
OH
O
OH
O
1) Macro-
lactonization
Cyclization precursor 2
O
Spiruchostatin A (1)
2) Amidation
D
-Cys
O
Et
Et
Si
Table 1. Optimizing the reaction conditions for the synthesis
of polymer-supported dipeptide 6
FmocHN
OH
BocHN
OH
X
1) Immobilization
O
STrt
HO
O
1) TMSOTf (0.3 M)
2,6-lutidine (0.9 M)
CH2Cl2, rt, 3 h
Et
O
OAllyl
Boc-
Et
Si
Si
FmocHN
N
O
D
-Val-statine derivative 3
STrt
Et
BocHN
O
H
D
-Ala
Et
NHFmoc
HO
O
STrt
2) Fmoc-D-Cys-OH (0.1 M)
Conditions, listed
O
OH
O
β-Hydroxy acid 4
OAllyl
OAllyl
5
6
Figure 1. Retrosynthesis of spiruchostatin A (1)
Entry
Reagent (M)
Additive (M)
Time (h)
Yield (%)a)
To immobilize the Boc-D
-Val-statine derivative 38 onto the
polymer support (Scheme 1), commercially available PS-DES
resin was first converted to PS-DES-OTf according to a reported
protocol.14 The modified resin was then treated with 3 under
1
2
3
4
5
DIC (0.1)
HOBt (0.15)
HOAt (0.15)
DIEA (0.15)
DIEA (0.15)
DIEA (0.15)
12
12
12
12
3
39
57
81
82
85
DIC (0.1)
PyBoP (0.1)
HATU (0.1)
HATU (0.1)
basic conditions to afford polymer-supported Boc-D-Val-statine
5. The loading of resin-bound 5 was determined to be 0.532
mmol·g−1 by post-cleavage gravimetric analysis.
a) Isolated yield was determined after cleavage from the polymer-support
(HF-Pyridine, THF-MeCN, rt, 2 h)
1) TMSCl, CH2Cl2
Et
Si
rt, 30 min
O
BocHN
Et
Et
PS-DES resin
1.47 mmol/g
Et
Si
2) TfOH, CH2Cl2
rt, 30 min
3) 3, 2,6-lutidine
CH2Cl2, rt, 12 h
H
Further elongation of dipeptide 6 to afford polymer-supported
tetrapeptide 9 was performed according to a protocol established
by us previously. The details concerning the reaction conditions
are displayed in Scheme 2. Removal of the Fmoc group in 6
under basic conditions (20% piperidine in DMF, rt, 30 min)
O
OAllyl
5: 0.532 mmol/g
OH
BocHN
followed by coupling of the resulting amine 7 with Fmoc-D-Ala-
O
3
OH utilizing DIC/HOBt afforded polymer-supported tripeptide 8.
Removal of the Fmoc group in 8 and acylation with the β-
hydroxy acid derivative 48 in the presence of PyBoP/DIEA at
room temperature provided 9 with high purity.
OAllyl
Scheme 1. Immobilization of the Boc-
D-Val-statine derivative
3 onto the polymer-support
Next, we investigated the conditions for the coupling of 5 with
Fmoc- -Cys-OH to obtain polymer-supported dipeptide 6.
Et
O
Et
O
Si
Si
FmocHN
H2N
D
N
20% piperidine
DMF, rt, 30 min
N
O
O
Et
Et
H
H
Selective removal of the Boc group in 5 in the presence of the
acid-labile silyl ether linkage was carried out by treating 5 with
TMSOTf/2,6-lutidine, followed by addition of MeOH for
removal of the TMS group on the resulting amine.15 It was
necessary to use excess 2,6-lutidine (0.9 M) for the selective and
efficient removal of the Boc group. The resulting free amine was
immediately used in the next reaction to preclude any potential γ-
STrt
STrt
O
O
OAllyl
OAllyl
6
7
Fmoc-
D-Ala-OH (0.1 M)
DIC (0.1 M)
HOBt (0.15 M)
DMF, rt, 4 h
Et
O
Si
N
O
HN
Et
H
O
lactamization. As Fmoc-D-Cys-OH is readily epimerized under
STrt
O
the conditions typically used for condensation, we explored
different reaction conditions to couple the polymer-supported
amine with Fmoc-D-Cys-OH (Table 1). Our initial attempt based
NHFmoc
OAllyl
8
on our previous solid-supported synthesis [N, N’-
diisopropylcarbodiimide (DIC)/1-hydroxybenzotriazole (HOBt),
Table 1, entry 1]8 yielded the desired dipeptide 6 in low yields. It
is likely that acylation of the amino group is hindered by the
bulkiness of both the isopropyl group at the γ-position and the
trialkylsilyl group on the β-hydroxy group. The use of 1-
hydroxy-7-azabenzotriazole (HOAt) instead of HOBt modestly
increased the yield of 6 up to 57% (entry 2). Higher yield (82%)
of the desired dipeptide 6 was successfully obtained with the use
Et
O
Si
1) 20% piperidine, DMF
rt, 30 min
O
Et
HN
O
N
H
2) β-Hydroxy acid 4
PyBoP, DIEA, DMF
rt, 5 h
TrtS
STrt
O
NH
OAllyl
OH
O
9
Scheme 2. Scheme for the synthesis of polymer-supported
tetrapeptide 9
of
O-(7-aza-1H-benzotriazol-1-yl)-N,
N,
N’,
N’-
tetramethyluronium hexafluorophosphate (HATU)/N, N-

3
After obtaining the desired tetrapeptide 9, we next explored
Table 2. Optimization of the conditions for
macrolactonization on the polymer-support
ACCEPTED MANUSCRIPT
the conditions for the removal of the allyl group in 9 and
subsequent macrolactonization of the polymer-supported
cyclization precursor 2 (Scheme 3). The allyl group was readily
removed by treatment with morpholine18 in the presence of
Pd(PPh3)4. The polymer-supported cyclization precursor 2 was
then subjected to macrolactonization in the presence of
O
1) Pd(PPh3)4 (0.01 M)
Phenylsilane (0.1 M)
THF, rt, 2 h
Et
O
Si
O
Et
Et
Si
O
HN
N
O
Et
HN
N
H
O
H
O
TrtS
STrt
TrtS
STrt
2) Macrolactonization
Conditions, listed
O
NH
NH
O
OAllyl
(DMAP).19
However,
O
MNBA/4-(dimethylamino)pyridine
OH
O
analysis of the products after cleavage of the reaction products
from the polymer-support revealed an inseparable mixture of the
desired macrolactone 10 and the unexpected amide 11 that was
formed by condensation of the free carboxylic acid with the
residual morpholine (left over from the allyl deprotection
reaction). It is likely that the polymer-supported deallylated
carboxylic acid retained morpholine through ionic interactions,
which subsequently resulted in the amidation reaction. Therefore,
we considered that use of amines was unsuitable for removal of
the allyl group owing to the difficulty associated with the
efficient removal of the amine on washing with organic solvents
after completion of the reaction.
9
12
Conditions
Conv.(%)a)
Puritya)
Entry
MNBA (0.01 M)
DMAP (0.1 M), rt, 3 h
-
-
1
60
77
MNBA (0.01 M)
DMAP (0.1 M), rt, 6 h
2
MNBA (0.01 M)
DMAP (0.1 M), rt, 12 h
3
>95
>95
>99
60
74
MNBA (0.04 M)
DMAP (0.1 M), rt, 12 h
4
MNBA (0.04 M)
DMAP (0.1 M), rt, 12 h
5b)
86 (17)c)
a) Determined by HPLC with UV peak area at 214 nm
after cleavage from the polymer-support.
b) A solution of sodium diethyldithiocarbamate was used for washing
out a trace amount of Pd catalyst after removal of the allyl group.
c) Isolated yield (9 steps from the polymer-supported 5)
O
O
Et
Et
Et
Si
Pd(PPh3)4 (0.01 M)
morpholine (0.1 M)
Si
O
O
HN
HN
N
N
Et
H
H
O
O
THF, rt, 3 h
TrtS
TrtS
STrt
STrt
O
O
NH
NH
Finally, we explored the reaction conditions leading to the
formation of the intramolecular disulfide bond on the polymer-
support and resulting in polymer-supported total synthesis of
spiruchostain A (1). Initial attempts to form the disulfide under
oxidative conditions as reported previously (I2 in CH2Cl2/MeOH,
rt)7, 8 did not yield 1 reproducibly on cleavage from the polymer-
support (Table 3, entry 1). Despite extensive investigations,
efficient conditions for solid-supported formation of the
intramolecular disulfide bond were not identified. Therefore, we
decided to pursue the intramolecular disulfide bond-forming
reaction after first releasing the macrolactone from the polymer
support. The silyl ether link between the polymer support and
macrolactone in 12 was cleaved using a solution of HF-pyridine
in THF, and the resulting solution, containing the released
macrolactone 10, was directly added to a solution of iodine in
CH2Cl2/MeOH. Unexpectedly, a complex mixture, with no clear
indication for the presence of 1, was obtained (entry 2). It is
likely that the pyridine retained in the solution from the prior
reaction inhibits the disulfide-forming reaction.
OAllyl
OH
OH
OH
O
O
9
2
O
O
1) MNBA (0.01 M)
DMAP (0.1 M)
CH2Cl2, rt, 12 h
OH
N
OH
HN
HN
N
H
H
O
O
+
TrtS
STrt
TrtS
STrt
2) HF-Pyridine
THF-MeCN
rt, 2 h
O
O
NH
NH
N
O
OH
Amide 11
O
O
O
Macrolactone 10
Scheme 3. Removal of the allyl group in
macrolactonization on the polymer-support.
9 and
Owing to the presence of the unexpected amidation product,
the conditions for the removal of the allyl group were re-
evaluated. After extensive investigations, a combination of
Pd(PPh3)4 and phenylsilane20 was found to be effective in
affording 2 in a pure form. Macrolactonization of the polymer-
supported cyclization precursor 2 was subsequently performed
utilizing MNBA/DMAP to afford macrolactone 12.
Macrolactonization of 2 was sluggish (a conversion of 60% in 3
h, Table 2, entry 1) when compared with that in the solution
phase, which was completed within 1 h.8 Extending the reaction
time improved the conversion of the macrolactonization reaction
(6 h, 77% conversion, entry 2). The reaction was complete in 12
h with >95% conversion, affording macrolactone 12 with 60%
purity (Table 2, entry 3). It should be noted here that its dimer
was not observed, therefore, performing the reaction at high
dilutions is not necessary. Efforts directed at improving the purity
of the macrolactonization product revealed that increasing the
concentration of MNBA improved the purity of 12 (74%, entry 4
vs 60%, entry 3). Further improvement in the purity of the
macrolactonization product was achieved when the polymer-
support was washed with a solution of the carbamic acid sodium
salt21 (efficiently removes any residual Pd catalyst). With the
wash step included in the protocol, the purity of released
macrolactone from 12 increased to 86%. In summary,
macrolactone 10 (17% overall yield, isolated) was synthesized in
Table 3. Optimization of the intramolecular disulfide
formation
O
O
Et
Si
OH
HN
N
O
HN
N
Conditions
H
Et
H
O
O
S
S
TrtS
STrt
O
NH
O
NH
O
O
O
O
12
Spiruchostatin A (1)
Conditions
Yielda)
Entry
1
I2, CH2Cl2-MeOH, rt, 30 min
<2
HF-Pyridine (0.01 M), THF, rt, 2 h;
filtered;
I2, CH2Cl2-MeOH, rt, 30 min
2
3
Complex mixture
5% aqueous HF, CH2Cl2-MeOH, rt, 2 h;
addition of CaCO3, then filtered;
I2, CH2Cl2-MeOH, rt, 30 min
17
a) Isolated yield (10 steps from the polymer-supported 5)
9 steps starting from the polymer-supported Boc-D-Val-statine
derivative 5 (entry 5).

4
Tetrahedron
Therefore, we utilized 5% aqueous HF/CH2Cl2/MeOH to
respectively, in the indicated solvent. Chemical shifts are
ACCEPTED MANUSCRIPT
release the macrolactone from the polymer support, and the
resulting resin-free cleavage solution was neutralized by addition
of CaCO3.22 Finally, the macrolactone-containing neutralized
reaction mixture was filtered and the filtrate was directly added
to a solution of iodine in CH2Cl2/MeOH to afford 1 in 17%
overall yield. Because the precursor macrolatone 12 was obtained
in 17% overall yield (see, Table 2), the yield of the disulfide
formation was quantitative. Spectral data, including specific
rotation, of the synthesized spiruchostatin A (1) were identical to
those of the natural product.6
reported in units parts per million (ppm) relative to
1
tetramethylsilane (0.00 ppm for H), chloroform (7.26 ppm for
1H) and chloroform-d (77.0 ppm for 13C) when internal standard
is not indicated. Multiplicities are reported by the following
abbreviations: s; singlet, d; doublet, t; triplet, q; quartet, dd;
double doublet, dt; double triplet, ddt; double double triplet, m;
multiplet, br; broad, J; coupling constants in Hertz. Mass spectra
and high-resolusion mass spectra were measured on
ThermoScientificTM ExactiveTM Plus Orbitap Mass Spectrometer
(for ESI). IR spectra were recorded on a JASCO FTIR-8400.
Only the strongest and/or structurally important absorption are
reported as the IR data afforded in cm–1. Optical rotations were
measured with a JASCO P-1010 polarimeter.
3. Conclusion
We have established a protocol for the solid-supported total
synthesis of spiruchostatin A (1). The salient features of the
4.2 Immobilization of Boc-
DES resin
D-Val statine derivative 3 onto PS-
synthesis include immobilization of the Boc-
derivative 3 via a silyl linker on the polymer support, sequential
coupling of Fmoc- -Cys-OH, Fmoc- -Ala-OH, and β-hydroxy
D-Val-statine
4.2.1 Immobilization of 3 onto PS-DES resin
D
D
acid 4 at the N-terminus of 5 to provide polymer-supported
tetrapeptide 9, use of the PhSiH3/Pd catalyst combination for the
removal of the allyl group at the C-terminus in 9, and MNBA-
mediated macrolactonization of polymer-supported 2 to provide
the advanced intermediate macrolactone 12. It is noteworthy that
use of a Pd scavenger for washing the polymer support after
removal of the allyl group is a critical factor for improving the
purity of the released macrolactone 10. Finally, two sequential
reactions, release of the macrolactone from the polymer support
and subsequent disulfide formation, furnished the desired
spiruchostatin A (1) in 17% overall yield. It should be noted here
that this protocol, in addition to the synthesis of the linear peptide
as demonstrated previously, allows for macrolactonization to take
place on the polymer support; this approach can therefore be used
for the synthesis of spiruchostatins, related natural products and
their analogues. The synthesis and biological evaluation of
spiruchostatin analogs are underway in our laboratory and the
results will be reported in due course.
To a PS-DES resin (500 mg) in a 20 mL syringe-shaped vessel
(Varian Reservoir) was added CH2Cl2 (5.0 mL), and the mixture
was shaken for 3 min and filtered. To this resin was added
chlorotrimethylsilane (191 µL, 1.50 mmol, 0.3 M) in CH2Cl2 (5.0
mL) at room temperature. After the mixture was shaken for 30
min, the resin was filtered and washed three times with CH2Cl2.
The resulting resin was treated with trifluoromethanesulfonic
acid (132 µL, 1.5 mmol, 0.3 M) in CH2Cl2 (5.0 mL) at room
temperature. After the mixture was shaken for 30 min, the resin
was filtered and washed three times with CH2Cl2. To this resin
was added a solution of 3 (452 mg, 1.50 mmol, 0.3 M) and 2,6-
lutidine (230 µL, 2.0 mmol, 0.4 M) in CH2Cl2 (5.0 mL) at room
temperature. After the mixture was shaken for 12 h, the resin was
filtered and washed 10% triethylamine in CH2Cl2 x 3, THF/H2O
(1:1) x 3, MeOH x 3 and ether x 3. The resulting resin was dried
under reduced pressure to give polymer-supported Boc-D-Val-
statine-derivative 5. IR (resin) 3451, 3372, 3026, 2925, 1738,
1722, 1494, 1454, 1235, 1176, 836, 768 cm–1.
4.2.2 Cleavage of 5
4. Experimental Section
4.1 General Techniques
To a polymer-supported 5 (30 mg) in a 6 mL syringe-shaped
vessel (Varian Reservoir) was added THF (1.5 mL), and the
mixture was shaken for 3 min and filtered. To the suspension in
THF acetonitrile (300 µL, 2:1) was added HF-pyridine (100 µL)
at room temperature. After the mixture was shaken for 2 h, the
resin was filtered and washed with THF x 3. The filtrate was
quenched with saturated aqueous NaHCO3. The aqueous layer
was extracted with ethyl acetate. The combined organic layers
were washed with 1 M aqueous HCl, saturated aqueous NaHCO3,
brine and dried over MgSO4, and filtered. The filtrate was
concentrated in vacuo. The residue was purified by column
chromatography on silica gel (25% ethyl acetate in hexane) to
All commercially available reagents were used as received.
Dry THF and CH2Cl2 (Kanto Chemical Co.) were obtained by
passing commercially available pre-dried, oxygen-free
formulations through activated alumina columns. All reactions
were monitored by thin-layer chromatography carried out on 0.2
mm E. Merck silica gel plates (60F-254) with UV light,
visualized by p-anisaldehyde solution, phosphomolybdic acid
solution. Column chromatography and flash column
chromatography were carried out with silica gel 60 N (Kanto
Chemical Co. 100–210 µm) and silica gel 60 N (Kanto Chemical
Co. 40–50 µm), respectively. Gel Permeation Chromatography
was performed on LC-9201 (recycling preparative HPLC), with
RI-50 refractive index detector and s-3740 ultra violet detector
with polystyrene gel column (JAIGEL-1H, 20 mm x 600 mm),
using chloroform as a solvent (3.5 mL/min). Preparative HPLC
purification was performed on reversed-phase HPLC (Waters
HPLC system), and the purity was determined with peak area at
UV 214 nm. The column used was Waters X BridgeTM C18 5
µm, 10 x 150 mm. Analysis of the synthetic peptides was
performed on reversed-phase HPLC (Waters LC/MS system ZQ-
2000), and the purity was determined with peak area at UV 214
or 254 nm. The column used was Waters X BridgeTM C18 3.5
give Boc-D-Val-statine derivative 3 (5.41 mg, 19.2 mol) as a
colorless oil, and the loading amount was determined to be 0.532
1
mmol•g–1. H NMR (400 MHz, CDCl3) δ 5.92 (ddt, 1H, J =
16.8, 10.0, 6.0 Hz), 5.33 (dd, 1H, J = 16.8, 1.2 Hz), 5.26 (m, 1H),
4.62 (d, 2H, J = 6.0 Hz), 4.41 (d, 1H, J = 9.6 Hz, NH), 3.94 (m,
1H), 3.54 (m, 1H), 3.22 (brs, 1H, OH), 2.64 (dd, 1H, J = 16.4, 3.2
Hz), 2.51 (dd, 1H, J = 16.4, 11.2 Hz), 2.12 (m, 1H), 1.44 (s, 9H),
0.95 (d, 3H, J = 6.8 Hz), 0.87 (d, 3H, J = 6.8 Hz); 13C NMR (100
MHz, CDCl3) δ 172.8, 156.4, 131.8, 118.5, 79.5, 69.1, 65.4, 58.8,
38.3, 28.3, 27.5, 20.1, 16.2; IR (CHCl3) 3444, 3372, 2964, 1717,
21
1695, 1521, 1367, 1171, 1068, 988 cm–1; [α]D
–8.42 (c 1.00,
CHCl3); HRMS(ESI) calcd for C15H27NO5Na [M+Na]+ 324.1787,
found 324.1776.
1
µm, 4.6 x 75 mm. H NMR spectra (400 MHz) and 13C NMR
spectra (100 MHz and 150 MHz) were recorded on JEOL JNM-
AL400 spectrometers and JEOL ECA-600 spectrometers,

5
4.3 Synthesis of polymer-supported dipeptide 6
afforded Fmoc-deprotected resin, and the resulting resin was
immediately used for the next reaction.
ACCEPTED MANUSCRIPT
4.3.1 Amidation with Fmoc-
To a polymer-supported Boc-
D
-Cys(Trt)-OH
To the resin was added DMF (1.0 mL) and the mixture was
shaken for 3 min and filtered. To a mixture of resin, Fmoc- -Ala-
D-Val-statine derivative 5 (50
D
mg) in a 6 mL syringe-shaped vessel (Varian Reservoir) was
added CH2Cl2 (1.0 mL) and the mixture was shaken for 3 min
and filtered. To the mixture of resin and 2,6-lutidine (79 µL, 0.68
OH (15 mg, 0.045 mmol, 0.1 M), HOBt (9.2 mg, 0.068 mmol,
0.15 M) and DIEA (15 µL, 0.090 mmol, 0.2 M) in DMF (0.45
mL) was added DIC (7.0 µL, 0.045 mmol, 0.1 M) at room
temperature. After the mixture was shaken for 4 h, the resin was
filtered and washed three times with DMF and THF,
respectively. The resulting resin was dried under reduced
pressure to give polymer-supported tripeptide 8. IR (resin) 3396,
3304, 3028, 2920, 1727, 1685, 1677, 1665, 1494, 1453, 1386,
1251, 1064, 1034, 844, 752 cm–1.
mmol) in CH2Cl2 (0.45 mL) was added
a solution of
trimethylsilyl trifluoromethanesulfonate (41 µL, 0.23 mmol) in
CH2Cl2 (0.30 mL) at room temperature. After the mixture was
shaken for 3 h, MeOH (0.15 mL) was added to the mixture at
room temperature. After the mixture was shaken for 10 min, the
resin was filtered and washed with CH2Cl2 x 3 and DMF x 3 to
afforded Boc deprotected resin. The resulting resin was
immediately used for the next reaction.
4.4.2 Cleavage of 8
To a polymer-supported tripeptide 8 (50 mg) in a 6 mL
syringe-shaped vessel (Varian Reservoir) was added THF (1.0
mL) and the mixture was shaken for 3 min and filtered. To a
suspension in THF acetonitrile (300 µL, 2:1) was added
HF pyridine (100 µL) at room temperature. After the mixture
was shaken for 2 h, the resin was filtered and washed three times
with THF. The filtrate was quenched with saturated aqueous
NaHCO3. The aqueous layer was extracted with ethyl acetate.
The combined organic layers were washed with 1 M aqueous
HCl, saturated aqueous NaHCO3, brine and dried over MgSO4,
and filtered. The filtrate was concentrated in vacuo. The residue
was purified by column chromatography on silica gel (50% ethyl
acetate in hexane) to give tripeptide S2 (19.5 mg, 23.3 mol,
88%, 5 steps from 5) as a white amorphous. 1H NMR (400 MHz,
To the above resin was added DMF (1.0 mL) and the mixture
was shaken for 3 min and filtered. To a suspension of resin,
Fmoc-D-Cys(Trt)-OH (44 mg, 0.075 mmol, 0.1 M) and DIEA
(26 µL, 0.15 mmol, 0.2 M) in DMF (0.75 mL) was added HATU
(29 mg, 0.075 mmol, 0.1 M) at room temperature. After the
mixture was shaken for 3 h, the resin was filtered and washed
with DMF x 3, THF x 3. The resulting resin was dried under
reduced pressure to give polymer-supported dipeptide 6. IR
(resin) 3310, 3025, 2919, 1732, 1683, 1668, 1494, 1454, 1252,
1071, 1030, 839, 752 cm–1.
4.3.2 Cleavage of 6
To a polymer-supported dipeptide 6 (50 mg) in a 6 mL
syringe-shaped vessel (Varian Reservoir) was added THF (1.0
mL) and the mixture was shaken for 3 min and filtered. To a
suspension in THF acetonitrile (300 µL, 2:1) was added
HF pyridine (100 µL) at room temperature. After the mixture
was shaken for 2 h, the resin was filtered and washed three times
with THF. The filtrate was quenched with saturated aqueous
NaHCO3. The aqueous layer was extracted with ethyl acetate.
The combined organic layers were washed with 1 M aqueous
HCl, saturated aqueous NaHCO3, brine and dried over MgSO4,
and filtered. The filtrate was concentrated in vacuo. The residue
was purified by column chromatography on silica gel (50% ethyl
acetate in hexane) to give dipeptide S1 (17.4 mg, 22.6 mol,
CDCl3) δ
(d, 2H, J = 7.2 Hz), 7.51 (t, 2H, J = 6.8
Hz), 7.10–7.46 (m, 19H), 6.24 (m, 2H, NH x 2), 5.92 (ddt, 1H, J
= 17.2, 11.2, 5.0 Hz), 5.29 (d, 1H, J = 17.2 Hz), 5.21 (d, 1H, J =
11.2 Hz), 5.08 (d, 1H, J = 4.8 Hz, NH), 4.56 (d, 2H, J = 5.0 Hz),
4.36 (m, 2H), 3.95–4.14 (m, 4H), 3.83 (m, 1H), 3.23 (brs, 1H,
OH), 2.94 (m, 1H), 2.59 (d, 1H, J = 16.0 Hz), 2.49 (m, 1H), 2.41
(dd, 1H, J = 16.0, 10.0 Hz), 2.13 (m, 1H), 1.30 (d, 3H, J = 6.8
Hz), 0.80 (m, 6H); 13C NMR (100 MHz, CDCl3) δ 172.9, 172.1,
170.2, 156.1, 144.3, 143.7, 143.4, 141.3, 141.3, 131.9, 129.4,
128.1, 127.8, 127.8, 127.1, 126.9, 125.0, 120.0, 118.3, 68.7, 67.2,
67.1, 65.3, 57.7, 52.6, 51.0, 47.0, 38.1, 32.7, 27.5, 20.2, 18.3,
16.6; IR (CHCl3) 3289, 3245, 3063, 2961, 1718, 1706, 1701,
1
85%, 3 steps from 5) as a colorless oil. H NMR (400 MHz,
26
1647, 1540, 1401, 1245, 1077, 1034, 741, 701 cm–1; [α]D
CDCl3) δ
(t, 2H, J = 7.6 Hz), 7.54 (t, 2H, J = 8.0 Hz),
7.16 7.45 (m, 19H), 5.84 (m, 1H), 5.80 (d, 1H, J = 9.6 Hz, NH),
5.28 (d, 1H, J = 17.2 Hz), 5.20 (d, 1H, J = 10.4 Hz), 4.89 (d, 1H,
J = 6.8 Hz, NH), 4.54 (m, 2H), 4.40 (m, 2H), 4.17 (t, 1H, J = 6.0
Hz), 3.87 (m, 1H), 3.78 (m, 1H), 3.69 (m, 1H), 3.23 (d, 1H, J =
4.4 Hz, OH), 2.66 (d, 2H, J = 7.6 Hz), 2.54 (d, 1H, J = 16.0 Hz),
2.40 (dd, 1H, J = 16.0, 10.0 Hz), 2.08 (m, 1H), 0.81 (d, 3H, J =
6.4 Hz), 0.80 (d, 3H, J = 6.4 Hz); 13C NMR (100 MHz, CDCl3) δ
172.8, 170.7, 156.1, 144.3, 143.6, 143.6, 141.3, 131.7, 129.5,
128.1, 127.9, 127.8, 127.1, 126.9, 124.9, 124.9, 120.0, 118.6,
68.7, 67.5, 67.0, 65.5, 57.3, 54.2, 47.0, 38.1, 33.1, 27.3, 20.1,
(c 0.85, CHCl3); HRMS(ESI) calcd for C50H53N3O7SNa
[M+Na]+ 862.3502, found 862.3476.
4.5 Synthesis of polymer-supported tetrapeptide 9
4.5.1 Amidation with β -hydroxy acid derivative 4
To a polymer-supported tripeptide 8 (50 mg) in a 6 mL
syringe-shaped vessel (Varian Reservoir) was added DMF (1.0
mL) and the mixture was shaken for 3 min and filtered. The resin
was treated with a solution of 20% piperidine in DMF (1.0 mL)
at room temperature. After the mixture was shaken for 30 min,
the resin was filtered and washed three times with DMF to
afforded Fmoc-deprotected resin, and the resulting resin was
immediately used for the next reaction.
16.2; IR (CHCl3) 3311, 3026, 2959, 1703, 1699, 1661, 1528,
26
1446, 1033, 987, 741, 701 cm–1; [α]D
+
(c 0.60, CHCl3);
HRMS(ESI) calcd for C47H48N2O6SNa [M+Na]+ 791.3131, found
791.3105.
To the above resin was added DMF (1.0 mL) and the mixture
was shaken for 3 min and filtered. To a suspension of resin, β-
hydroxy acid 48 (31 mg, 0.075 mmol, 0.10 M) and DIEA (26 µL,
0.15 mmol, 0.20 M) in DMF (0.75 mL) was added PyBoP (59
mg, 0.11 mmol, 0.15 M) at room temperature. After the mixture
was shaken for 12 h, the resin was filtered and washed three
times with DMF and THF, respectively. The resulting resin was
dried under reduced pressure to give polymer-supported
tetrapeptide 9. IR (resin) 3628, 3307, 3026, 2920, 1735, 1671,
1510, 1493, 1250, 1183, 1072, 1014, 843, 759, 698 cm–1.
4.4 Synthesis of polymer-supported tripeptide 8
4.4.1 Amidation with Fmoc-D-Ala-OH
To a polymer-supported dipeptide 6 (50 mg) in a 6 mL
syringe-shaped vessel (Varian Reservoir) was added DMF (1.0
mL) and the mixture was shaken for 3 min and filtered. The resin
was treated with a solution of 20% piperidine in DMF (1.0 mL)
at room temperature. After the mixture was shaken for 30 min,
the resin was filtered and washed three times with DMF to

6
Tetrahedron
ACCEPTED MANUSCRIPT
4.5.2 Cleavage of 9
was shaken for 2 h, the resin was filtered and washed three times
with THF. The filtrate was quenched with saturated aqueous
NaHCO3. The aqueous layer was extracted with ethyl acetate.
The combined organic layers were washed with 1 M aqueous
HCl, saturated aqueous NaHCO3, brine and dried over MgSO4,
and filtered. The filtrate was concentrated in vacuo. The residue
was purified by column chromatography on preparative TLC (9%
methanol in chloroform) to give macrolactone 10 (4.2 mg, 4.4
mol, 17%, 9 steps from 5) as a white amorphous. 1H NMR (400
MHz, CDCl3) δ 7.18–7.50 (m, 30H), 6.92 (d, 1H, J = 7.2 Hz,
NH), 6.77 (m, 1H, NH), 5.91 (m, 1H, NH), 5.58–5.69 (m, 2H),
5.34 (dd, 1H, J = 15.6, 6.4 Hz), 4.39 (m, 1H), 4.23 (m, 1H), 3.78
(m, 1 H), 3.22–3.41 (m, 1H), 2.39–2.69 (m, 5H), 2.21 (t, 2H, J =
7.2 Hz), 2.03–2.12 (m, 3H), 1.36 (d, 3H, J = 7.2 Hz), 0.96 (d, 3H,
J = 6.4 Hz), 0.88 (d, 3H, J = 6.8 Hz); 13C NMR (150 MHz,
CDCl3) δ 172.8, 171.9, 170.4, 169.9, 144.4, 144.5, 132.8, 132.1,
132.0, 129.6, 129.5, 128.0, 127.9, 126.9, 126.7, 70.9, 68.2, 66.8,
66.6, 60.7, 50.0, 41,1, 37.5, 32.0, 31.3, 31.1, 29.7, 28.8, 20.4,
To a polymer-supported tetrapeptide 9 (50 mg) in a 6 mL
syringe-shaped vessel (Varian Reservoir) was added THF (1.0
mL) and the mixture was shaken for 3 min and filtered. To the
suspension in THF acetonitrile (300 µL, 2:1) was added
HF pyridine (100 µL) at room temperature. After the mixture
was shaken for 2 h, the resin was filtered and washed three times
with THF. The filtrate was quenched with saturated aqueous
NaHCO3. The aqueous layer was extracted with ethyl acetate.
The combined organic layers were washed with 1 M aqueous
HCl, saturated aqueous NaHCO3, brine and dried over MgSO4,
and filtered. The filtrate was concentrated in vacuo. The residue
was purified by column chromatography on preparative TLC
(10% methanol in chloroform) to give tetrapeptide S3 (14.2 mg,
13.9 mol, 52%, 7 steps from 5) as a white amorphous. 1H NMR
(400 MHz, CDCl3) δ 7.15–7.47 (m, 30H), 6.97 (d, 1H, J = 7.6
Hz, NH), 6.18 (d, 1H, J = 9.6 Hz, NH), 6.09 (d, 1H, J = 6.4 Hz,
NH), 5.87 (ddt, 1H, J = 17.6, 10.8, 5.6 Hz), 5.41 (m, 1H), 5.29
(m, 2H), 5.20 (d, 1H, J = 10.8 Hz), 4.57 (m, 2H), 4.32 (m, 1H),
4.26 (t, 1H, J = 6.8 Hz), 3.98–4.12 (m, 2H), 3.81 (m, 1H), 3.79
(d, 1H, J = 4.8 Hz, OH), 2.78 (brs, 1H, OH), 2.73 (dd, 1H, J =
13.2, 6.8 Hz), 2.59 (dd, 1H, J = 16.8, 2.4 Hz), 2.39–2.47 (m, 2H),
2.22 (dd, 1H, J = 14.0, 2.4 Hz), 2.16–2.24 (m, 3H), 2.02–2.12 (m,
2H), 1.34 (d, 3H, J = 7.2 Hz), 0.88 (d, 3H, J = 6.8 Hz), 0.88 (d,
3H, J = 6.8 Hz); 13C NMR (100 MHz, CDCl3) δ 172.8, 172.1,
171.8, 170.5, 144.8, 144.2, 132.3, 131.9, 130.4, 129.5, 129.4,
128.1, 127.9, 126.9, 126.6, 118.3, 69.8, 68.7, 66.9, 66.6, 65.3,
57.9, 52.7, 50.0, 43.9, 38.0, 33.0, 31.3, 31.2, 27.7, 20.1, 17.4,
19.2, 17.8; IR (CHCl3) 3301, 2926, 1734, 1669, 1540, 1444,
1260, 1182, 1034, 743, 700 cm–1; [α]D
– 6.0 (c 0.300,
25
CHCl3); HRMS(ESI) calcd for C58H61N3O6S2Na [M+Na]+
982.3899, found 982.3876.
4.7 Synthesis of spiruchostatin A (1)
To a polymer-supported macrolactone 12 (50 mg) in a 6 mL
syringe-shaped vessel (Varian Reservoir) was added CH2Cl2 (1.0
mL) and the mixture was shaken for 3 min and filtered. The resin
was treated 5% hydrogen fluoride solution (47% aqueous
hydrogen fluoride was attenuated with CH2Cl2/MeOH (2:1)) at
room temperature. After the mixture was shaken for 2 h, to the
mixture was added CaCO3 (150 mg) at room temperature. After
the mixture was shaken for 20 min, the resin was filtered. The
filtrate was subsequently added to a solution of iodine (48 mg,
0.38 mmol) in CH2Cl2 (10 mL) at room temperature. After being
stirred for 30 min, the reaction mixture was quenched with 10%
aqueous Na2S2O3 and the aqueous layer was extracted with
CH2Cl2. The combined organic layers were washed with brine,
dried over MgSO4, and filtrated. The filtrate was concentrated in
vacuo. The residue was purified by reverse-phase HPLC to give
spiruchostatin A (1) (2.1 mg, 4.4 mol, 17%, 10 steps from 5) as
a white amorphous. 1H NMR (400 MHz, CDCl3) δ 7.40 (d, 1H,
J = 6.8 Hz, NH), 6.70 (d, 1H, J = 9.2 Hz, NH), 6.40 (m, 1H),
5.84 (m, 1H, NH), 5.65 (d, 1H, J = 15.2 Hz), 5.50 (m, 1H), 4.93
(dt, 1H, J = 8.8, 4.0 Hz), 4.60 (m, 1H), 4.28 (dq, 1H, J = 7.2, 4.0
Hz), 3.39 (m, 2H), 3.24 (m, 1H), 3.15 (m, 1H), 2.69–2.80 (m,
5H), 2.56 (d, 2H, J = 13.2 Hz), 2.36–2.51 (m, 2H), 1.52 (d, 3H, J
16.9; IR (CHCl3) 3275, 2959, 2929, 1735, 1623, 1529, 1443,
1260, 1032, 744, 699 cm–1; [α]D
(c 0.38, MeOH);
28
HRMS(ESI) calcd for C61H67N3O7S2Na [M+Na]+ 1040.4318,
found 1040.4296.
4.6 Synthesis of polymer-supported macrolactone 12
4.6.1 Removal of the protecting groups in 9 and
macrolactonization on polymer-support
To a polymer-supported tetrapeptide 9 in a 6 mL syringe-
shaped vessel (Varian Reservoir) was added THF (degassed, 1.0
mL) and the mixture was shaken for 3 min and filtered. To a
suspension of resin and phenylsilane (9.2 µL, 0.075 mmol, 0.10
M)
in
THF
(degassed,
0.75
mL)
was
added
tetrakis(triphenylphosphine)palladium(0) (8.7 mg, 0.0075 mmol,
0.010 M) at room temperature. After the mixture was shaken for
2 h, the resin was filtered and washed three times with THF, 3%
(w/v) sodium diethyldithiocarbamate in DMF, DMF and
dichloromethane, respectively. The resulting resin was
immediately used for the next reaction.
= 7.2 Hz), 1.04 (d, 3H, J = 6.8 Hz), 0.93 (d, 3H, J = 6.8 Hz); 13
C
NMR (100 MHz, CDCl3) δ 171.9, 170.9, 170.6, 169.0, 133.6,
128.6, 70.5, 69.3, 63.8, 63.7, 52.3, 52.2, 40.8, 40.7, 39.6, 29.6,
20.6, 20.6, 19.6, 16.6; IR (CHCl3) 3368, 3333, 2954, 2924, 1733,
To the crude resin was added CH2Cl2 (1.0 mL) and the
mixture was shaken for 3 min and filtered. To the suspension of
resin and DMAP (9.2 mg, 0.075 mmol, 0.1 M) in CH2Cl2 (0.75
mL) was added MNBA (10 mg, 0.03 mmol, 0.04 M) at room
temperature. After the mixture was shaken for 12 h, the resin was
filtered and washed three times with CH2Cl2. The resulting resin
was dried under reduced pressure to give polymer-supported
macrolactone 12. IR (resin) 3287, 3026, 2921, 1735, 1647, 1493,
1452, 1250, 1074, 1032, 842, 737, 694 cm–1.
1667, 1660, 1652, 1537, 1432, 1265, 1160, 752 cm–1; [α]D –60
29
(c 0.045, MeOH) [lit.6 [α]D –63.6 (c 0.14, MeOH)]; HRMS(ESI)
calcd for C20H31N3O6S2Na [M+Na]+ 496.1552, found 496.1534.
Acknowledgments
This work was supported by a Grant-in-Aid for Scientific
Research on Innovative Areas “Chemical Biology of Natural
Products” from The Ministry of Education, Culture, Sports,
Science and Technology, Japan (No. 2301). This work was
partially supported by Platform for Drug Discovery, Informatics,
and Structural Life Science from the Ministry of Education,
Culture, Sports, Science and Technology, Japan.
4.6.2 Cleavage of 12
To a polymer-supported macrolactone 12 (50 mg) in a 6 mL
syringe-shaped vessel (Varian Reservoir) was added THF (1.0
mL) and the mixture was shaken for 3 min and filtered. To a
suspension in THF acetonitrile (300 µL, 2:1) was added
HF pyridine (100 µL) at room temperature. After the mixture

7
Tanaka, H.; Takahashi, T. Synlett 2001, 1101–1104. i) Hijikuro,
References and Notes
ACCEPTED MANUSCRIPT
I.; Doi, T.; Takahashi, T. J. Am. Chem. Soc. 2001, 123, 3716–3722.
j) Paterson, I.; Temal-Laieb, T. Org. Lett. 2002, 4, 2473–2476. k)
Gu, W.; Liu, S.; Silverman, R. B. Org. Lett. 2002, 4, 4174–4174. l)
Kobori, A.; Miyata, K.; Ushioda, M.; Seio, K.; Sekine, M. J. Org.
Chem. 2002, 67, 476–485. m) Kobori, A.; Miyata, K.; Ushioda, M.;
Seio, K.; Sekine, M. Chem. Lett. 2002, 31, 16–17. n) Moura-letts,
G.; DiBlasi, H. M.; Bauer, R. A.; Tan, D. S. P. Natl. Acad. Sci.
USA 2011, 108, 6745–6750. o) Strack, M.; Metzler-Nolte, N.;
Albaba, H. B. Org. Lett. 2013, 15, 3126–3129.
1. a) Bolden, J. E.; Peart, M. J.; Johnstone, R. W. Nat. Rev. Drug
Discov. 2006, 5, 769–784. b) Xu, W. S.; Parmigiani, R. B.; Marks,
P. A. Oncogene 2007, 26, 5541–5552.
2. Furumai, R.; Matsuyama, A.; Kobashi, N.; Lee, K.–H.; Nishiyama,
M.; Nakajima, H.; Tanaka, A.; Komatsu, Y.; Nishino, N.; Yoshida,
M.; Horinouchi, S. Cancer Res. 2002, 62, 4916–4921.
3. Finnin, M. S.; Donigian, J. R.; Cohen, A.; Richon, V. M.; Rifkind,
R. A.; Marks, P. A.; Breslow, R.; Pavletich, N. P. Nature 1999,
401, 188–193.
4. Plumb, J. A.; Finn, P. W.; Williams, R. J.; Bandara, M. J.; Romero,
M. R.; Watkins, C. J.; La Thangue, N. B.; Brown, R. Mol. Cancer
Ther. 2003, 2, 721–728.
5. Mottamal, M.; Zheng, S.; Huang, T. L.; Wang, G. Molecules 2015,
20, 3898–3941.
6. Masuoka, Y.; Nagai, A.; Shin-ya, K.; Furihata, K.; Nagai, K.;
Suzuki, K.; Hayakawa, Y.; Seto, H. Tetrahedron Lett. 2001, 42,
41–44.
7. a) Yurek-George, A.; Habens, F.; Brimmell, M.; Packham, G.;
Ganesan, A. J. Am. Chem. Soc. 2004, 126, 1030–1031. b)
Takizawa, T.; Watanabe, K.; Narita, K.; Kudo, K.; Oguchi, T.; Abe,
H.; Katoh, T. Heterocycles 2008, 76, 275–290. c) Calandra, N. A.;
Cheng, Y. L.; Kocak, K. A.; Miller, J. S. Org. Lett. 2009, 11, 1971–
1974. d) Narita, K.; Kikuchi, T.; Watanabe, K.; Takizawa, T.;
Oguchi, T.; Kudo, K.; Matsuhara, K.; Abe, H.; Yamori, T.;
Yoshida, M.; Katoh, T. Chem. Eur. J. 2009, 15, 11174–11186.
8. a) Doi, T.; Iijima, Y.; Shin-ya, K.; Ganesan, A.; Takahashi, T.
Tetrahedron Lett. 2006, 47, 1177–1180. b) Iijima, Y.; Munakata,
A.; Shin-ya, K.; Ganesan, A.; Doi, T.; Takahashi, T. Tetrahedron
Lett. 2009, 50, 2970–2972. c) Fuse, S.; Okada, K.; Iijima, Y.;
Munakata, A.; Machida, K.; Takahashi, T.; Takagi, M.; Shin-ya,
K.; Doi, T. Org. Biomol. Chem. 2011, 9, 3825–3833. d) Doi, T.;
Otaka, H.; Umeda, K.; Yoshida, M. Tetrahedron 2015,
doi:10.1016/j.tet.2015.05.051.
9. Solid-phase synthesis is also useful tool for preparation of
radiolabelled peptidic molecules because the labeling reagent
would be readily recovered after the coupling reaction. a) Wiegand,
H.; Wirz, B.; Schweitzer, A.; Gross, G.; Perez, M. I. R.; Andres, H.
Chem. Biodivers. 2004, 1, 1812–1828. b) Marik, J.; Hausner, S. H.;
Fix, L. A.; Gagnon, M. K. J.; Sutcliffe, J. L. Bioconjugate Chem.
2006, 17, 1017–1021.
13. Silyl linker has also been utilized for the peptide synthesis, see: a)
Lee, Y.; Silverman, R. B. J. Am. Chem. Soc. 1999, 121, 8407–8408.
b) Lee, Y.; Silverman, R. B. Org. Lett. 2000, 2, 303–306. c) Gu,
W.; Liu, S.; Silverman, R. B. Org. Lett. 2002, 4, 4171–4174. d) Gu,
W.; Silverman, R. B. J. Org. Chem. 2003, 68, 8774–8779. e) Liu,
S.; Gu, W.; Lo, D.; Ding, X.–Z.; Ujiki, M.; Adrian, T. E.; Soff, G.
A.; Silverman, R. B. J. Med. Chem. 2005, 48, 3630–3638. f) Doi,
T.; Hoshina, Y.; Mogi, H.; Yamada, Y.; Takahashi, T. J. Comb.
Chem. 2006, 8, 571–582. g) Hoshina, Y.; Yamada, Y.; Tanaka, H.;
Doi, T.; Takahashi, T. Bioorg. Med. Chem. Lett. 2007, 17, 2904–
2907.
14. a) Smith, E. M. Tetrahedron Lett. 1999, 40, 3285–3288. b) Hu, Y.;
Porco, Jr. J. A. Tetrahedron Lett. 1999, 40, 3289–3292.
15. a) Sakaitani, M.; Ohfune, Y. Tetrahedron Lett. 1985, 26, 5543–
5546. b) Sakaitani, M.; Ohfune, Y. J. Org. Chem. 1990, 55, 870–
876. c) Zhang, A. J.; Russell, D. H.; Zhu, J.; Burgess, K.
Tetrahedron Lett. 1998, 39, 7439–7442.
16. PyBoP:
benzotriazolyloxy-tris(pyrrolidino)phosphonium
hexafluorophosphate. Coste, J. Le-Nguyen, D.; Castro, B.
Tetrahedron Lett. 1990, 31, 205–208.
17. When the coupling of Fmoc-D-Cys-OH and Boc-D-Val-statine
derivative was performed in solution-phase, we have observed that
yield of dipeptide was gradually decreased in a time-dependent
manner due to removal of the Fmoc group under basic conditions.
Therefore, it is conceivable that yield of 6 in 12 h would be slightly
lower than that in 3 h (entry 5 vs entry 4).
18. Lloyd–Williams, P.; Lou, G.; Albericio, F.; Giralt, E. Tetrahedron
Lett. 1991, 32, 4207–4210.
19. a) Shiina, I.; Ibuka, R.; Kubota, M. Chem. Lett. 2002, 286–287. b)
Shiina, I. Kubota. M. Ibuka, R. Tetrahedron Lett. 2002, 43, 7535–
7539. c) Shiina, I.; Kubota, M.; Oshiumi, H.; Hashizume, M. J.
Org. Chem. 2004, 69, 1822–1830. d) Shiina, I.; Hashizume, M.;
Yamai, Y.; Oshiumi, H.; Shimazaki, T.; Takasuna, Y.; Ibuka, R.
Chem. Eur. J. 2005, 11, 6601–6608. e) Shiina, I. Bull. Chem. Soc.
Jpn. 2014, 87, 196–233.
20. Dessolin, M.; Guillerez, M.–G.; Thieriet, F.; Guibé, F.; Loffet, A.
Tetrahedron Lett. 1995, 36, 5741–5744.
21. Kates, S. A.; de la Torre, B. G.; Eritja, R.; Albericio, F.
Tetrahedron Lett. 1994, 35, 1033–1034.
10. a) Flanigan, E.; Marshall, G. R. Tetrahedron Lett. 1970, 27, 2403–
2406. b) Isied, S. S.; Kuehn, C. G.; Lyon, J. M.; Merrifield. R. B. J.
Am. Chem. Soc. 1982, 104, 2632–2634. c) Rovero, P.; Quartara, L.;
Fabbri, G. Tetrahedron Lett. 1991, 32, 2639–2642. d) Lloyd-
Williams, P.; Jou, G.; Albericio, F.; Giralt, E. Tetrahedron Lett.
1991, 32, 4207–4210. e) Tizeciak, A.; Bannwarth, W. Tetrahedron
Lett. 1992, 33, 4557–4560. f) Kates, S. A.; Solé, N. A.; Johnson, C.
R.; Hudson, D.; Barany, G.; Albericio, F. Tetrahedron Lett. 1993,
34, 1549–1552.
22. Kaburaki and Kishi reported that the use of calcium carbonate is
effective to scavenge hydrogen fluoride (HF) and the resulting CaF2
and H2O are readily removed by filtration and evaporation, see;
Kaburagi, Y.; Kishi, Y. Org. Lett. 2006, 9, 723–726.
11. Hu, Y.; Porco, Jr. J. A.; Labadie, J. W.; Gooding, O. W.; Trost, B.
M. J. Org. Chem. 1998, 63, 4518–4521.
12. a) Plunkett, M. J.; Ellman, J. A. J. Org. Chem. 1995, 60, 6006–
6007. b) Doi, T.; Hijikuro, I.; Takahshi, T. J. Am. Chem. Soc. 1999,
121, 6749–6750. c) Doi, T.; Sugiki, M.; Yamada, H.; Takahashi,
T.; Porco, J. A. Jr. Tetrahedron Lett. 1999, 40, 2141–2144. d)
Spring, D. R.; Krishnan, S.; Schreiber, S. L. J. Am. Chem. Soc.
2000, 122, 5656–5657. e) Briehn, C. A.; Kirschbaum, T.; Baeuerle,
P. J. Org. Chem. 2000, 65, 352–359. f) Ishii, A.; Hojo, H.;
Kobayashi, A.; Nakamura, K.; Nakahara, Y.; Ito, Y.; Nakahara, Y.
Tetrahedron 2000, 42, 1463–1466. g) Wang, B.; Chen, L.; Kim, K.
Tetrahedron Lett. 2001, 42, 1463–1466. h) Matsuda, A.; Doi, T.
Supplementary data
Copies of 1H and 13C NMR spectra for the synthetic
spiruchostatin A (1) and the cleavage products. This material is
available free of charge via the Internet.