Synthesis and biological activity of mycalolide analogs

Article abstract of DOI:10.1016/j.tet.2006.06.046

Mycalolide analog 4, consisting only of the side chain of mycalolide B (2), a trisoxazole macrolide of marine origin, was stereoselectively synthesized using Roush crotylboration, an Evans aldol reaction, and a Paterson aldol reaction as key steps. The an

Full text of DOI:10.1016/j.tet.2006.06.046

Tetrahedron 62 (2006) 8278–8290
Synthesis and biological activity of mycalolide analogs
Kiyotake Suenaga, ,y Tomoyuki Kimura, Takeshi Kuroda, Keita Matsui, Saori Miya,
*
*
Satomi Kuribayashi, Akira Sakakura and Hideo Kigoshi
Department of Chemistry, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan
Received 13 April 2006; revised 14 June 2006; accepted 15 June 2006
Available online 5 July 2006
Abstract—Mycalolide analog 4, consisting only of the side chain of mycalolide B (2), a trisoxazole macrolide of marine origin, was stereo-
selectively synthesized using Roush crotylboration, an Evans aldol reaction, and a Paterson aldol reaction as key steps. The analog 4 was found
to have strong actin-depolymerizing activity.
Ó 2006 Elsevier Ltd. All rights reserved.
1. Introduction
of two forms; one is polymeric F-actin and the other is
monomeric G-actin. Aplyronine A (1) not only inhibits
polymerization of actin by sequestering G-actin and forming
a 1:1 complex, but also depolymerizes F-actin to G-actin by
severing.3 We achieved the total synthesis of 1 and investi-
gated the structure–activity relationships of aplyronine A
(1) using natural and synthetic analogs: the side chain in 1
is essential to actin-depolymerizing activity, and analog 3,
which consists only of the side-chain moiety of 1, exhibits
strong activity.4 We recently determined the crystal structure
Actin-disrupting marine natural products are of interest
to natural products chemists and pharmacologists.1 These
natural products consist of macrolides, cyclic peptides, and
cyclodepsipeptides. Aplyronine A (1), an antitumor macro-
lide isolated from Aplysia kurodai,2 interacts with actin, the
major protein in cytoskeleton. Actin regulates various cell
functions such as muscle contraction, cell motility, and
cell division. Actin exists as a dynamic equilibrium mixture
* Corresponding authors. Tel./fax: +81 29 853 4313 (H.K.); e-mail: kigoshi@chem.tsukuba.ac.jp
Present address: Department of Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku, Yokohama 223-8522, Japan.
y
0040–4020/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2006.06.046

K. Suenaga et al. / Tetrahedron 62 (2006) 8278–8290
8279
of actin–aplyronine A complex via synchrotron X-ray anal-
ysis5 and obtained chemical evidence for the direct interac-
tion between actin and the side-chain portion of aplyronine
A by photoaffinity labeling experiments.6 These results
display the great importance of the side-chain moiety in
the activity against actin.
the stereochemistry. Cleavage of the benzyl-protecting
group in 9 gave alcohol 10, which was oxidized to aldehyde
11. The Evans aldol reaction between aldehyde 11 and imide
1215 gave hydroxy imide 13 as a single diastereomer, which
was converted into diol 14. Diol 14 was transformed with
(PhS)2-Bu3P16 into sulfide 15, which was oxidized with
m-chloroperoxybenzoic acid to sulfone 16. The secondary
hydroxy group in 16 was methylated to afford C22–C28
segment 5 (57% from 7).
Mycalolide B (2) is a cytotoxic and antifungal macrolide iso-
lated from a sponge of the genus Mycale sp.7 Mycalolide B
(2) inhibits actomyosin Mg2+-ATPase8 and also interacts
with actin in the same manner as 1.9 The total synthesis of
mycalolide A, which lacks the 2,3-di-O-methyl-D-glyceroyl
group at C30, has been achieved.10 Recently, several crystal
structures of trisoxazole macrolides with actin have been
reported.11 Since mycalolide B (2) possesses a similar side
chain to that of 1, analog 4 is expected to show actin-
depolymerizing activity. We have previously reported the
synthesis and actin-depolymerizing activity of analog 4.12
We describe herein details of the stereocontrolled synthesis
of mycalolide analog 4 and its biological activities, includ-
ing both its cytotoxicity and actin-depolymerizing activity,
along with those of aplyronine analog 3.
The synthesis of C29–C35 segment 6 is shown in Scheme 2.
While compound 6 with four contiguous syn–anti–anti
stereocenters was previously prepared using the Evans aldol
reaction and Sharpless epoxidation as the key steps,4a–c the
improved synthesis of 6 was developed by using the Paterson
aldol reaction17 as the key step. Thus, the Paterson aldol
reaction between ethyl ketone 17 and crotonaldehyde gave
hydroxy ketone 18.17b Stereoselective reduction of 18 with
tetramethylammonium triacetoxyborohydride18 afforded an
anti-1,3-diol exclusively, which was transformed into aceto-
nide 19. Its stereochemistry was confirmed to be anti by the
13C chemical shifts of two acetonide methyls (dC 25.8 and
23.7).19 The benzyl-protecting group in 19 was removed
with calcium in liquid ammonia to give alcohol 20, which
was converted into tosylate 21. One carbon homologation
with NaCN provided nitrile 22, the reduction of which
with DIBAL afforded aldehyde 23. Aldehyde 23 was treated
with PPTS in methanol to provide a separable mixture of
diastereomeric acetals, 24a and 24b, and the dimethyl acetal
24c.20 After chromatographic separation, two minor prod-
ucts, 24b and 24c, were subjected to equilibration (PPTS in
methanol) to afford a mixture of 24a, 24b, and 24c, from
which the major acetal 24a was again obtained. By repeating
this procedure, 24b and 24c could be transformed into 24a.
Protection of the hydroxy group in 24a gave benzyl ether 25,
the double bond of which was cleaved oxidatively to afford
the C29–C35 segment 6 (48% from 17).
2. Results and discussion
2.1. Chemical synthesis
The synthesis of mycalolide analog 4 has been carried out
according to a convergent synthetic methodology connect-
ing C22–C28 and C29–C35 segments, 5 and 6.
The synthesis of C22–C28 segment 5 is shown in Scheme 1.
While anti stereocenters between C23 and C24 of 5 was pre-
viously constructed by using an anti-selective aldol reaction
under Heathcock conditions,13 the improved synthesis of 5
was developed by using Roush crotylboration14 as the key
step. Thus, the Roush crotylboration between boronate 7
and 3-benzyloxypropanal afforded homoallylic alcohol 8
(91%) as a single diastereomer (Scheme 1). Oxidative cleav-
age of the olefin moiety of 8, reduction with NaBH4, and
silylation gave silyl ether 9. The spectral data of 9 were iden-
tical to those of previously synthesized 9,12 this confirmed
The Julia coupling reaction between 5 and 6 gave a hydroxy
sulfone, which was converted into olefin 26 by reduction
with sodium amalgam (Scheme 3). Removal of the benzyl-
protecting group in 26 with calcium in liquid ammonia
gave alcohol 27, catalytic hydrogenation of which provided
ꢁ
˚
Scheme 1. Reagents and conditions: (a) MS 4 A, toluene, ꢀ78 C, 91%; (b) OsO4, NMO, THF–t-BuOH–H2O, rt; then NaIO4, rt; (c) NaBH4, EtOH, rt; (d)
TBSCl, imidazole, DMF, 50 ꢁC, 79% (three steps); (e) H2, 10% Pd–C, NaHCO3, EtOAc, rt, 92%; (f) DMSO, (COCl)2, CH2Cl2, ꢀ78 ꢁC; Et3N, ꢀ78 ꢁC/
0 ꢁC, 89%; (g) 12, Bu2BOTf, Et3N, CH2Cl2, ꢀ78 ꢁC/0 ꢁC, 100%; (h) LiBH4, EtOH, Et2O, ꢀ10 ꢁC, 100%; (i) (PhS)2, Bu3P, DMF, rt, 96%; (j) m-CPBA,
NaHCO3, CH2Cl2, rt, 99%; (k) MeI, NaH, THF, rt, 94%.

8280
K. Suenaga et al. / Tetrahedron 62 (2006) 8278–8290
Scheme 2. Reagents and conditions: (a) Sn(OTf)2, Et3N, CH2Cl2, ꢀ78 ꢁC/ꢀ60 ꢁC, 85%; (b) Me4NBH(OAc)3, AcOH, MeCN, ꢀ25 ꢁC; (c) (MeO)2CMe2,
PPTS, acetone, rt, 84% (two steps); (d) Ca, liq. NH3, i-PrOH, THF, ꢀ78 ꢁC, 98%; (e) p-TsCl, pyridine, 0 ꢁC, 100%; (f) NaCN, DMSO, 50 ꢁC, 98%; (g) DIBAL,
CH2Cl2, hexane, ꢀ78 ꢁC, 95%; (h) PPTS, MeOH, rt, 82%; (i) BnBr, NaH, DMF, rt, 95%; (j) OsO4, NMO, H2O, acetone, rt; then NaIO4, rt, 99%.
alcohol 28.4a The hydroxyl group was protected to give
3,4-dimethoxybenzyloxymethyl ether 29. At this stage,
the TBS-protecting groups in 29 were changed to TBDPS
groups, because TBS group was sensitive to acidic condi-
tions at the later stage of the synthesis. Thus, deprotection
of two TBS-protecting groups in 29 afforded diol 30, which
was converted into TBDPS ether 31. The cyclic acetal
moiety of 31 was hydrolyzed under acidic conditions to
afford a hemiacetal, which was reduced with NaBH4 to
give diol 32. Selective protection of the primary hydroxyl
group in 32 provided trityl ether 33, the secondary hydroxyl
group of which was acetylated to afford acetate 34. The trityl
group of 34 was removed with formic acid to give alcohol
35, which was oxidized to aldehyde 36. Condensation
between 36 and N-methylformamide under acidic conditions
provided enamide 37. Deprotection of the 3,4-dimethoxy-
benzyloxymethyl group of 37 gave alcohol 38, which
was esterified with 2,3-di-O-methyl-D-glyceric acid under
Yamaguchi conditions to afford a mixture of diastereomeric
esters 39, which resulted from the racemization of 2,3-di-O-
methyl-D-glyceric acid. After removal of the silyl groups in
39, HPLC separation of the diastereomers provided analogs
4 and 40.21
2.2. Biological activities
The actin-depolymerizing activity and cytotoxicity against
HeLa S3 cells of aplyronine A (1), mycalolide B (2), and
their analogs 3, 4, and 40 are shown in Table 1. The mycalo-
lide analog 3 exhibited strong activity comparable to that of
Scheme 3. Reagents and conditions: (a) BuLi, THF–hexane, ꢀ78 ꢁC; (b) 5% Na–Hg, NaH2PO4, MeOH, 0 ꢁC, 72% (two steps); (c) Ca, liq. NH3, i-PrOH,
THF, ꢀ78 ꢁC, 89%; (d) H2, 5% Pd–C, NaHCO3, EtOH, 55 ꢁC, 95%; (e) 3,4-dimethoxybenzyloxymethyl chloride, i-Pr2NEt, CH2Cl2, rt, 84%; (f) Bu4NF,
THF, rt, 99%; (g) TBDPSCl, imidazole, DMF, rt, 75%; (h) 1 M HCl, DME, rt; (i) NaBH4, EtOH, rt, 70% (two steps); (j) TrCl, pyridine, 50 ꢁC, 95%; (k)
Ac2O, pyridine, DMAP, rt, 100%; (l) HCO2H, Et2O, rt, 77%; (m) Dess–Martin periodinane, pyridine, CH2Cl2, rt, 91%; (n) MeNHCHO, PPTS, hydroquinone,
˚
MS 3 A, benzene, reflux, 55%; (o) DDQ, 1 M phosphate buffer (pH 6), t-BuOH, CH2Cl2, rt, 90%; (p) 2,3-di-O-methyl-D-glyceric acid, 2,4,6-trichlorobenzoyl
chloride, Et3N, DMAP, CH2Cl2, rt, 74%; (q) HF$pyridine, pyridine, THF, rt; separation by HPLC, (4) 55%, (40) 34%.

K. Suenaga et al. / Tetrahedron 62 (2006) 8278–8290
8281
Table 1. Cytotoxicity and actin-depolymerizing activity of mycalolide B,
aplyronine A, and their analogs
gel 60 F254 (0.25 mm layer thickness). Fuji Silysia silica
gel BW-820 MH and FL-60D were used for column chro-
matography unless otherwise noted. Organic solvents for
moisture-sensitive reactions were distilled from the follow-
ing drying agents: THF and ether (Na-benzophenone ketyl),
benzene (Na), acetonitrile and triethylamine (calcium
hydride), DMSO (calcium hydride under reduced pressure),
CH2Cl2 (P2O5), acetone (anhydrous K2CO3), and MeOH
(Mg). All moisture-sensitive reactions were performed
under an atmosphere of nitrogen, and the starting materials
were azeotropically dried with benzene before use. All
new compounds were determined to be >95% pure by
1H NMR unless otherwise noted.
Compounds
Actin-depolymerizing
activitya
Cytotoxicity against
HeLa S3 cells
IC50
(mM)b
Relative
potencyc
IC50
(mg/mL)
Relative
potencyc
Aplyronine A (1) 1.6
Mycalolide B (2)d nd
100
nd
20
59
0.00048e 100
0.0035
>10
>10
14
3
7.9
2.7
4.4
<0.01
<0.01
<0.01
4
40
36
>10
a
Activity was monitored by measuring the fluorescent intensity of pyrenyl
actin. For the conditions of assay, see Section 4.2.
IC50 indicates the concentration required to depolymerize F-actin
(3.7 mM) to 50% of its control amplitude.
b
c
4.1.1. Homoallylic alcohol 8. Preparation of crotylboronate
7: To a stirred solution of potassium tert-butylalkoxide
(8.4 g, 75 mmol) in THF (60 mL) cooled at ꢀ78 ꢁC was
added liquefied trans-2-butene (7.2 mL, 78 mmol) cooled
at ꢀ78 ꢁC and then 1.56 M solution of BuLi in hexane
(48 mL, 75 mmol) so as to maintain the reaction temperature
below ꢀ65 ꢁC for 2 h. The mixture was stirred at ꢀ50 ꢁC for
15 min and re-cooled to ꢀ78 ꢁC, triisopropyl borate
(17.2 mL, 75.0 mmol) was added so as to keep the reaction
temperature below ꢀ65 ꢁC for 1 h. The mixture was stirred
for 15 min and poured into 1 M aqueous HCl saturated with
NaCl (220 mL). To the mixture D-(ꢀ)-diisopropyl tartrate
(17.5 g, 74.7 mmol) was added, and the mixture was ex-
tracted with ether (4ꢂ50 mL). The combined organic layers
were dried with MgSO4 and concentrated to give boronate 7
(25.4 g) as a colorless oil. Crotylboration: To a stirred mix-
The relative potencies were calculated from the IC50 values of the com-
pound (aplyronine A¼100).
d
e
Mycalolide B was purchased from Wako Pure Chemical Industries, Inc.
Ref. 4c.
aplyronine A (1). This result revealed that the side-chain
portion in mycalolide B (2) is responsible for the potent ac-
tivity of 2, as is the case with aplyronine A (1). Comparison
of the activities of 3, 4, and 40 revealed that both the struc-
ture and stereochemistry of the acyl group influenced activ-
ity. In contrast, analogs 3, 4, and 40 showed no cytotoxicity
at 10 mg/mL, thus indicating that the presence of the macro-
lide ring is essential to the strong cytotoxicity of 1 and 2, and
that actin-depolymerization is not directly related to the
cytotoxicity.
˚
ture of boronate 7 (1.2 g, 9.7 mmol) and MS 4 A (50 mg)
3. Conclusion
in toluene (10 mL) cooled at ꢀ78 ꢁC was added a solution
of 3-benzyloxypropanal (517 mg, 3.15 mmol) in toluene
(6 mL, 2ꢂ2 mL rinse). The mixture was stirred at ꢀ78 ꢁC
for 1.5 h and diluted with 2 M aqueous NaOH (50 mL).
The mixture was stirred at 0 ꢁC for 30 min and extracted
with EtOAc (3ꢂ10 mL). The extracts were dried with
MgSO4 and concentrated. The residual oil was purified by
column chromatography on silica gel (12 g, hexane–EtOAc
10:1) to give 8 (630 mg, 91%) as a colorless oil: TLC Rf
The stereocontrolled synthesis of mycalolide analog 4, con-
sisting only of the side chain of mycalolide B (2), was car-
ried out. The mycalolide analog 4 and aplyronine analog 3
were found to exhibit strong actin-depolymerizing activity.
In contrast, the analogs did not show cytotoxicity against
HeLa S3 cells. These results clearly indicated that the
side-chain portions of aplyronine A and mycalolide B are
essential to the actin-depolymerizing activity and that the
combination of the side-chain portion and the macrolactone
portion is responsible for the cytotoxicity.
1
0.46 (hexane–EtOAc 3:1); [a]2D0 3.38 (c 1.00, CHCl3) ; H
NMR (270 MHz, CDCl3) d 7.38–7.24 (m, 5H), 5.81 (m,
1H), 5.11 (m, 1H), 5.05 (m, 1H), 4.56 (s, 2H), 3.77–3.61
(m, 3H), 2.47 (br s, 1H, OH), 2.24 (m, 1H), 1.78–1.71 (m,
2H), 1.05 (d, J¼7.0 Hz, 3H); 13C NMR (67.8 MHz,
CDCl3) d 140.2, 137.8, 128.2, 127.5, 115.3, 74.0, 73.2,
69.1, 44.0, 33.6, 15.8.
4. Experimental
4.1. General
Melting points are uncorrected. Optical rotations were mea-
sured with a JASCO DIP-370 polarimeter or a JASCO DIP-
1000 polarimeter. 1H NMR spectra were recorded on
a JEOL JNM-EX270 (270 MHz) or a Bruker AVANCE-
400M (400 MHz) instrument. Chemical shifts are reported
in parts per million from internal standards [tetramethyl-
silane (0.00 ppm) for CDCl3 and C6D5H (7.16 ppm) for
C6D6] and J values are in hertz. 13C NMR spectra were
recorded on a JEOL JNM-EX270 instrument (67.8 MHz)
using CDCl3 as a solvent. Chemical shifts are reported in
parts per million from the solvent peak (77.0 ppm). FAB
mass spectra were recorded on a JEOL SX-102 instrument.
ESI mass spectra were recorded on a QStar/Pulsar i spec-
trometer (Applied Biosystems). Both TLC analysis and pre-
parative TLC were conducted on E. Merck precoated silica
4.1.2. Silyl ether 9. To a stirred solution of homoallylic
alcohol 8 (5.00 g, 22.7 mmol) in THF (65 mL) were added
a solution of N-methylmorpholine-N-oxide (4.05 g, 34.6
mmol) in H2O (13 mL) and a 0.078 M solution of osmium
tetroxide in tert-butyl alcohol (15 mL, 1.2 mmol). After
being stirred at room temperature for 2.5 h, sodium period-
ate (10.5 g, 49.1 mmol) was added. The reaction mixture
was stirred at room temperature for 1.5 h, diluted with satu-
rated aqueous Na2S2O3 (50 mL), and extracted with EtOAc
(3ꢂ50 mL). The combined extracts were washed with satu-
rated aqueous Na2S2O3 (3ꢂ20 mL) and brine (30 mL), dried
(Na2SO4), and concentrated to give a crude aldehyde (8.0 g).
To a stirred solution of the crude aldehyde (8.0 g) in EtOH
(230 mL) was added sodium borohydride (1.06 g, 28.0

8282
K. Suenaga et al. / Tetrahedron 62 (2006) 8278–8290
mmol), and the mixture was stirred at room temperature for
20 min. The reaction was quenched by addition of acetone
(50 mL) and the resulting mixture was stirred at room tem-
perature for 10 min and concentrated. The mixture was
diluted with H2O (30 mL) and extracted with EtOAc
(5ꢂ20 mL). The extracts were combined, washed with brine
(30 mL), dried (Na2SO4), and concentrated. The residual oil
was purified by column chromatography on silica gel (100 g,
hexane–EtOAc 1:1) to give a crude diol (4.77 g).
saturated aqueous NaHCO3 (20 mL), and brine (20 mL),
successively, dried (Na2SO4), and concentrated. The resi-
dual oil was purified by column chromatography on silica
gel (50 g, hexane–ether 50:1/25:1) to give 11 (1.07 g,
89%) as a colorless oil: TLC, Rf 0.55 (hexane–EtOAc 5:1);
[a]2D1 ꢀ4.56 (c 1.00, CHCl3); IR (neat) 2854, 1732, 1257,
1
1086, 837 cmꢀ1; H NMR (270 MHz, CDCl3) d 9.81 (t,
J¼2.6 Hz, 1H), 4.35 (dt, J¼4.9, 5.6 Hz, 1H), 3.48 (dd,
J¼5.9, 10.0 Hz, 1H), 3.43 (dd, J¼7.0, 10.0 Hz, 1H), 2.50
(dd, J¼2.6, 5.9 Hz, 2H), 1.92 (m, 1H), 0.89 (s, 9H), 0.87
(s, 9H), 0.86 (d, J¼7.0 Hz, 3H), 0.07 (s, 3H), 0.05 (s, 3H),
0.04 (s, 3H), 0.04 (s, 3H); 13C NMR (67.8 MHz, CDCl3)
d 202.4, 68.9, 64.8, 47.8, 41.7, 26.0, 25.9, 18.3, 18.1,
11.6, ꢀ4.4, ꢀ4.5, ꢀ5.3, ꢀ5.4; HRMS (ESI) calcd for
C18H40NaO3Si2 (M+Na)+ 383.2414, found 383.2367.
To a stirred solution of the crude diol (4.77 g) and imidazole
(12.7 g, 186 mmol) in DMF (10 mL) cooled at 0 ꢁC was
added tert-butyldimethylsilyl chloride (14.1 g, 93.6 mmol).
The resulting solution was stirred at 50 ꢁC for 11 h, cooled
to room temperature, and diluted with cold water (50 mL).
The mixture was extracted with EtOAc (3ꢂ50 mL). The
combined extracts were washed with H2O (3ꢂ30 mL) and
brine (30 mL), dried (Na2SO4), and concentrated. The resi-
dual oil was purified by column chromatography on silica
gel (FL60D 100 g, hexane–EtOAc 50:1) to give 9 (8.15 g,
79% in three steps) as a colorless oil : TLC, Rf 0.57 (hex-
ane–EtOAc 4:1); [a]D26 ꢀ7.2 (c 1.02, CHCl3); IR (neat)
4.1.5. Hydroxy imide 13. To a stirred solution of imide 12
(226 mg, 0.970 mmol) in CH2Cl2 (1.4 mL) cooled at 0 ꢁC
were added 1 M solution of dibutylboron triflate in CH2Cl2
(0.97 mL, 0.97 mmol) and triethylamine (0.19 mL,
1.3 mmol), successively. The reaction mixture was stirred
at 0 ꢁC for 40 min and cooled to ꢀ78 ꢁC. A solution of alde-
hyde 11 (212 mg, 0.587 mmol) in CH2Cl2 (0.3 mL,
2ꢂ0.2 mL rinse) was added, and the reaction mixture was
stirred at ꢀ78 ꢁC for 2 h and at 0 ꢁC for 20 min. After the re-
action was quenched by addition of 0.5 M phosphate buffer
(pH 7, 2 mL) and MeOH (3 mL), 30% aqueous hydrogen per-
oxide (1.5 mL) in MeOH (3 mL) was added slowly, and the
resulting solution was stirred at 0 ꢁC for 1 h. The organic sol-
vents were evaporated, and the mixture was cooled to 0 ꢁC.
Saturated aqueous Na2S2O3 (3 mL) was added slowly, and
the mixture was extracted with ether (3ꢂ5 mL). The extracts
were combined, washed with saturated aqueous NaHCO3
(5 mL) and brine (5 mL), dried (Na2SO4), and concentrated.
The residual oil was purified by column chromatography on
silica gel (60 g, hexane–EtOAc 15:1/10:1/5:1) to give
13 (358 mg, 100%) as a colorless oil along with recovered
12 (64 mg). Compound 13: TLC, Rf 0.40 (hexane–EtOAc
5:1); [a]2D2 ꢀ31.9 (c 1.00, CHCl3); IR (neat) 3525, 1783,
1
1471, 1255, 1092, 837 cmꢀ1; H NMR (270 MHz, CDCl3)
d 7.34–7.27 (m, 5H), 4.49 (s, 2H), 3.91 (dt, J¼4.5, 7.3 Hz,
1H), 3.59–3.52 (m, 2H), 3.52 (dd, J¼7.0, 9.9 Hz, 1H),
3.41 (dd, J¼6.4, 9.9 Hz, 1H), 1.88–1.78 (m, 2H), 1.71 (m,
1H), 0.88 (s, 9H), 0.87 (s, 9H), 0.85 (d, J¼7.0 Hz, 3H),
0.04 (s, 3H), 0.03 (s, 3H), 0.02 (s, 6H); HRMS (ESI) calcd
for C25H49O3Si2 (M+H)+ 453.3220, found 453.3204.
4.1.3. Alcohol 10. A mixture of silyl ether 9 (7.95 g,
17.6 mmol), NaHCO3 (1.79 g, 21.3 mmol), and 10% Pd on
carbon (1.32 g) in EtOAc (176 mL) was stirred under a
hydrogen atmosphere at room temperature for 11 h. The
mixture was filtered through a pad of Celite, and the residue
was washed with EtOAc. The filtrate and the washings
were combined and concentrated. The residual oil was
purified by column chromatography on silica gel (100 g,
hexane–EtOAc 20:1) to give 10 (5.88 g, 92%) as a colorless
oil: TLC Rf 0.55 (hexane–EtOAc 5:1); [a]2D8 ꢀ8.7 (c 0.992,
1
1697, 1387, 1251, 1209, 1091 cmꢀ1; H NMR (270 MHz,
CHCl3); IR (CHCl3) 3425, 1473, 1255 cmꢀ1
;
1H NMR
CDCl3) d 7.37–7.15 (m, 5H), 4.69 (m, 1H), 4.26–4.14 (m,
3H), 3.98 (dt, J¼4.0, 6.6 Hz, 1H), 3.75 (dq, J¼4.0, 7.0 Hz,
1H), 3.61 (dd, J¼6.0, 10.0 Hz, 1H), 3.53 (br s, 1H, OH),
3.47 (dd, J¼6.0, 10.0 Hz, 1H), 3.28 (dd, J¼3.3, 13.5 Hz,
1H), 2.77 (dd, J¼9.6, 13.5 Hz, 1H), 1.96 (dt, J¼6.0,
6.6 Hz, 1H), 1.67 (ddd, J¼4.0, 10.0, 14.0 Hz, 1H), 1.55
(ddd, J¼2.6, 6.6, 14.0 Hz, 1H), 1.27 (d, J¼7.0 Hz, 3H),
0.89 (s, 18H), 0.88 (d, J¼7.0 Hz, 3H), 0.10 (s, 3H), 0.08 (s,
3H), 0.04 (s, 6H); 13C NMR (67.8 MHz, CDCl3) d 176.2,
153.0, 135.1, 129.3, 128.9, 127.3, 68.6, 66.1, 65.9, 65.0,
55.3, 43.4, 40.7, 37.9, 36.2, 26.0, 26.9, 18.4, 18.1, 12.6,
11.3, ꢀ4.3, ꢀ4.6, ꢀ5.2, ꢀ5.3; HRMS (ESI) calcd for
C31H55NaO6Si2 (M+Na)+ 616.3466, found 616.3466.
(270 MHz, CDCl3) d 3.95 (dt, J¼5.3, 6.3 Hz, 1H), 3.72 (t,
J¼5.6 Hz, 2H), 3.42 (dd, J¼6.6, 9.9 Hz, 1H), 3.24 (dd,
J¼6.0, 9.9 Hz, 1H), 2.29 (br, 1H, OH), 1.98–1.82 (m, 2H),
1.66 (m, 1H), 0.87 (s, 9H), 0.86 (s, 9H), 0.82 (d,
J¼6.9 Hz, 3H), 0.06 (s, 3H), 0.05 (s, 3H), 0.01 (s, 6H);
13C NMR (67.8 MHz, CDCl3) d 72.4, 65.1, 60.7, 41.0,
33.8, 26.0, 25.9, 18.3, 18.1, 11.7, ꢀ4.4, ꢀ4.5, ꢀ5.3, ꢀ5.4;
HRMS (ESI) calcd for C18H43O3Si2 (M+H)+ 363.2751,
found 363.2751.
4.1.4. Aldehyde 11. To a stirred solution of oxalyl chloride
(0.44 mL, 5.0 mmol) in CH2Cl2 (12 mL) cooled at ꢀ78 ꢁC
was added a solution of DMSO (0.65 mL, 9.2 mmol) in
CH2Cl2 (1.5 mL) dropwise. The resulting solution was
stirred at ꢀ78 ꢁC for 30 min, and a solution of alcohol 10
(1.22 g, 3.35 mmol) in CH2Cl2 (1.5 mL, 3ꢂ0.5 mL rinse)
was added dropwise. The mixture was stirred at ꢀ78 ꢁC
for 40 min, and triethylamine (2.4 mL, 17.2 mmol) was
added. The resulting mixture was stirred at ꢀ78 ꢁC for 1 h,
warmed to 0 ꢁC, and stirred for 1 h. The mixture was diluted
with H2O (30 mL) and extracted with EtOAc (3ꢂ30 mL).
The combined extracts were washed with H2O (20 mL),
4.1.6. Alcohol 14. To a stirred solution of hydroxy imide 13
(878 mg, 1.48 mmol) in ether (26 mL) in the presence of
anhydrous ethanol (0.10 mL, 1.8 mmol) cooled at ꢀ10 ꢁC
was added a 2.0 M solution of lithium borohydride in
THF (0.90 mL, 1.8 mmol), and the solution was stirred
at ꢀ10 ꢁC for 30 min. The reaction was quenched by addi-
tion of 1 M aqueous NaOH (4 mL), and the mixture was
stirred at 0 ꢁC for 15 min. The mixture was diluted with
saturated aqueous Na2S2O3 (40 mL) and extracted with

K. Suenaga et al. / Tetrahedron 62 (2006) 8278–8290
8283
ether (4ꢂ20 mL). The combined extracts were washed with
brine (20 mL), dried (Na2SO4), and concentrated. The resid-
ual oil was purified by column chromatography on silica gel
(60 g, hexane–EtOAc 3:1/1:1/1:3) to give 14 (628 mg,
100%) as a colorless oil: TLC, Rf 0.54 (hexane–ether 1:3);
[a]1D9 +7.9 (c 1.00, CHCl3); IR (neat) 3392, 1471, 1255,
1064, 836 cmꢀ1; 1H NMR (270 MHz, CDCl3) d 4.07 (ddd,
J¼2.4, 2.4, 10.5 Hz, 1H), 3.89 (dt, J¼4.6, 7.3 Hz, 1H),
3.70–3.55 (m, 2H), 3.61 (dd, J¼5.4, 9.7 Hz, 1H), 3.45 (dd,
J¼5.4, 9.7 Hz, 1H), 3.14 (br s, 1H, OH), 1.94 (m, 1H),
1.77 (m, 1H), 1.72 (ddd, J¼4.6, 10.5, 12.4 Hz, 1H), 1.50
(ddd, J¼2.4, 4.6, 12.4 Hz, 1H), 0.89 (d, J¼7.0 Hz, 3H),
0.84 (s, 9H), 0.83 (s, 9H), 0.80 (d, J¼7.0 Hz, 3H), 0.07 (s,
3H), 0.03 (s, 3H), 0.00 (s, 3H), ꢀ0.01 (s, 3H); 13C NMR
(67.8 MHz, CDCl3) d 72.6, 72.0, 66.8, 65.9, 64.9, 39.9,
39.8, 35.1, 26.0, 25.4, 18.4, 18.1, 13.4, 11.2, ꢀ4.1, ꢀ4.7,
ꢀ5.2, ꢀ5.3; HRMS (ESI) calcd for C21H48NaO4Si2
(M+Na)+ 443.2989, found 443.2995.
14.3 Hz, 1H), 1.11 (d, J¼7.0 Hz, 3H), 0.98 (s, 9H), 0.94
(s, 9H), 0.88 (d, J¼7.0 Hz, 3H), 0.18 (s, 3H), 0.15 (s, 3H),
0.12 (s, 3H), 0.12 (s, 3H); 13C NMR (67.8 MHz, CDCl3)
d 140.0, 133.4, 129.1, 127.7, 72.3, 70.4, 64.8, 59.4, 39.7,
35.7, 34.5, 26.0, 25.9, 18.4, 18.0, 14.1, 13.4, ꢀ4.2, ꢀ4.7,
ꢀ5.2, ꢀ5.4; HRMS (ESI) calcd for C27H52NaO5Si2
(M+Na)+ 567.2972, found 567.2980.
4.1.9. C22–C28 segment 5. To a stirred solution of sulfone
16 (1.44 g, 2.64 mmol) in THF (26 mL) cooled at 0 ꢁC were
added methyl iodide (0.84 mL, 13.5 mmol) and NaH
(401 mg of 60% dispersion in mineral oil, 10.0 mmol), suc-
cessively. The mixture was stirred at room temperature for
16 h, and the reaction was quenched by addition of ice
(2 g) and saturated aqueous NH4Cl (30 mL). The mixture
was extracted with ether (3ꢂ30 mL). The combined extracts
were washed with saturated aqueous Na2S2O3 (30 mL) and
brine (30 mL), dried (Na2SO4), and concentrated. The resi-
dual oil was purified by column chromatography on silica
gel (75 g, benzene–ether 100:1/50:1) to give 5 (1.39 g,
95%) as a colorless oil: TLC, Rf 0.58 (benzene–ether
10:1); [a]2D6 ꢀ39.3 (c 1.00, CHCl3); IR (neat) 1471, 1306,
4.1.7. Sulfide 15. To a stirred solution of alcohol 14 (215 mg,
0.511 mmol) and diphenyl disulfide (197 mg, 0.904 mmol)
in DMF (2 mL) cooled at 0 ꢁC was added tributylphosphine
(0.25 mL, 1.0 mmol), and the resulting solution was stirred
at room temperature for 11 h. Water (0.5 mL) was added,
and the resulting mixture was concentrated. The residual
oil was purified by column chromatography on silica gel
(60 g, hexane–ether 10:1) to give 15 (254 mg, 99%) as a
colorless oil: TLC, Rf 0.46 (hexane–ether 5:1); [a]2D2 +11.1
(c 1.00, CHCl3); IR (neat) 3496, 1471, 1254, 1063,
1
1255, 1149, 1088, 837 cmꢀ1; H NMR (270 MHz, CDCl3)
d 7.97–7.94 (m, 2H), 7.70–7.55 (m, 3H), 3.87 (ddd, J¼1.9,
3.5, 5.1 Hz, 1H), 3.38 (d, J¼7.0 Hz, 2H), 3.35 (dd, J¼1.5,
14.0 Hz, 1H), 3.23 (ddd, J¼1.9, 3.8, 10.0 Hz, 1H), 3.09 (s,
3H), 2.78 (dd, J¼10.3, 14.0 Hz, 1H), 2.53 (m, 1H), 1.89
(dtq, J¼3.5, 7.0, 7.0 Hz, 1H), 1.31 (ddd, J¼1.9, 10.0,
14.0 Hz, 1H), 1.08 (d, J¼7.0 Hz, 3H), 1.07 (m, 1H), 0.89
(s, 9H), 0.88 (s, 9H), 0.80 (d, J¼7.0 Hz, 3H), 0.08 (s, 3H),
0.07 (s, 3H), 0.04 (s, 6H); 13C NMR (67.8 MHz, CDCl3)
d 139.9, 133.5, 129.2, 128.0, 80.3, 69.5, 65.2, 57.3,
56.3, 42.2, 31.8, 29.0, 26.1, 26.0, 18.3, 16.3, 10.6, ꢀ3.8,
ꢀ4.4, ꢀ5.2, ꢀ5.3; HRMS (ESI) calcd for C28H54NaO5SSi2
(M+Na)+ 581.3128, found 581.3095; Anal. Calcd
for C28H54O5SSi2: C, 60.17; H, 9.74. Found: C, 60.05; H,
9.68.
1
837 cmꢀ1; H NMR (270 MHz, CDCl3) d 7.35–7.11 (m,
5H), 4.05 (m, 1H), 3.93 (m, 1H), 3.63 (dd, J¼5.8, 9.8 Hz,
1H), 3.50 (dd, J¼5.4, 9.8 Hz, 1H), 3.18 (dd, J¼6.1,
12.7 Hz, 1H), 2.78 (dd, J¼7.8, 12.7 Hz, 1H), 2.01 (m, 1H),
1.73 (m, 1H), 1.68 (ddd, J¼3.6, 10.8, 14.7 Hz, 1H), 1.51
(ddd, J¼1.9, 5.4, 14.7 Hz, 1H), 1.02 (d, J¼6.8 Hz, 3H),
0.91 (s, 9H), 0.90 (s, 9H), 0.85 (d, J¼7.0 Hz, 3H), 0.11 (s,
3H), 0.08 (s, 3H), 0.05 (s, 6H); 13C NMR (67.8 MHz,
CDCl3) d 137.1, 129.2, 128.9, 128.7, 128.5, 125.4, 72.3,
70.0, 64.9, 40.0, 38.9, 37.2, 36.3, 26.0, 25.9, 18.4, 18.1,
13.7, 13.2, ꢀ4.2, ꢀ4.7, ꢀ5.2, ꢀ5.3; HRMS (ESI) calcd for
C27H52NaO3SSi2 (M+Na)+ 535.3073, found 535.3054.
4.1.10. Hydroxy ketone 18. To a mixture of Sn(OTf)2
(5.8 g, 14 mmol) and triethylamine (2.4 mL, 17 mmol) in
CH2Cl2 (130 mL) cooled at ꢀ78 ꢁC was added a solution
of ethylketone 17 (2.2 g, 11 mmol), and the mixture was
stirred at ꢀ78 ꢁC for 2 h. A 2.3 M solution of crotonalde-
hyde in CH2Cl2 (6.6 mL, 16 mmol) was added, and the reac-
tion mixture was stirred at ꢀ78 ꢁC for 2 h and ꢀ60 ꢁC for
1 h. The mixture was warmed to room temperature and
diluted with 0.5 M phosphate buffer (pH 7.0, 130 mL).
The organic layer was separated, and the aqueous layer was
extracted with ether (3ꢂ130 mL). The organic layer and the
extracts were combined, washed with 0.5 M phosphate
buffer (pH 7.0, 130 mL) and brine (130 mL), dried
(Na2SO4), and concentrated. The residual oil was purified
twice by column chromatography on silica gel (100 g, hex-
ane–ether 5:1/4:1/3:1) and (FL60D 100 g, hexane–ether
5:1/4:1/3:1) to give 18 (2.5 g, 85%) as a colorless oil:
TLC, Rf 0.41 (hexane–ether 1:1); [a]2D6 ꢀ0.07 (c 1.00,
4.1.8. Sulfone 16. To a stirred solution of sulfide 15 (1.36 g,
2.66 mmol) in CH2Cl2 (26 mL) cooled at 0 ꢁC were added
NaHCO3 (1.67 g, 19.9 mmol) and 77% m-chloroperoxy-
benzoic acid (1.61 g, 7.18 mmol). After 5 min, the mixture
was warmed to room temperature and stirred at room tem-
perature for 15 min. The reaction mixture was diluted with
saturated aqueous Na2S2O3 (10 mL) and H2O (30 mL),
stirred at room temperature for 30 min, and extracted
with ether (3ꢂ50 mL). The combined extracts were washed
with saturated aqueous NaHCO3 (30 mL) and brine
(30 mL), dried (Na2SO4), and concentrated. The residual
oil was purified by column chromatography on silica gel
(43 g, hexane–EtOAc 6:1) to give 16 (1.44 g, 99%) as a col-
orless oil: TLC, Rf 0.4 (hexane–ether 1:1); [a]2D2 +7.4 (c 1.00,
CHCl3); IR (neat) 3519, 1471, 1306, 1255, 1147, 1086,
1
CHCl3); IR (neat) 3446 (br), 1701, 1655 cmꢀ1; H NMR
1
837 cmꢀ1; H NMR (270 MHz, CDCl3) d 7.97–7.94 (m,
(270 MHz, CDCl3) d 7.36–7.24 (m, 5H), 5.65 (ddq, J¼1.1,
15.1, 6.5 Hz, 1H), 5.41 (ddq, J¼6.2, 15.1, 1.4 Hz, 1H),
4.49 (d, J¼11.9 Hz, 1H), 4.43 (d, J¼11.9 Hz, 1H), 4.42
(m, 1H), 3.64 (dd, J¼8.6, 8.6 Hz, 1H), 3.45 (dd, J¼5.1,
8.6 Hz, 1H), 3.15 (m, 1H), 2.84 (dq, J¼3.5, 7.0 Hz, 1H),
2.60 (br, 1H, OH), 1.67 (dd, J¼1.4, 6.5 Hz, 3H), 1.08
2H), 7.70–7.55 (m, 3H), 4.00–3.90 (m, 2H), 3.67 (dd,
J¼5.7, 9.7 Hz, 1H), 3.52 (dd, J¼5.7, 9.7 Hz, 1H), 3.52 (br
s, 1H, OH), 3.45 (dd, J¼4.1, 14.0 Hz, 1H), 3.01 (dd,
J¼7.8, 14.0 Hz, 1H), 2.25 (m, 1H), 1.99 (m, 1H), 1.64
(ddd, J¼4.9, 10.3, 14.3 Hz, 1H), 1.55 (ddd, J¼2.7, 4.9,

8284
K. Suenaga et al. / Tetrahedron 62 (2006) 8278–8290
(d, J¼7.3 Hz, 3H), 1.03 (d, J¼7.0 Hz, 3H); 13C NMR
(67.8 MHz, CDCl3) d 217.4, 137.5, 130.3, 128.3, 127.6,
127.5, 127.5, 73.4, 72.9, 72.3, 51.3, 45.4, 17.8, 15.6, 10.2;
HRMS (ESI) calcd for C17H24NaO3 (M+Na)+ 299.1623,
found 299.1625.
(dd, J¼3.2, 11.1 Hz, 1H), 3.52 (dd, J¼5.9, 11.1 Hz, 1H),
3.26 (dd, J¼5.7, 7.6 Hz, 1H), 2.68 (br, 1H), 1.82 (dd,
J¼2.2, 6.9 Hz, 1H), 1.75 (m, 1H), 1.65 (dd, J¼1.6, 6.2 Hz,
1H), 1.32 (s, 3H), 1.31 (s, 3H), 0.96 (d, J¼6.9 Hz, 3H),
0.83 (d, J¼6.9 Hz, 3H); MS (FAB) m/z 251 (M+Na)+;
HRMS (ESI) calcd for C13H24NaO3 (M+Na)+ 251.1623,
found 251.1607.
4.1.11. Acetonide 19. To a solution of tetramethylammo-
nium triacetoxyborohydride (24.8 g, 94.2 mmol) in aceto-
nitrile (88 mL) and acetic acid (93 mL) cooled at –25 ꢁC
was added a solution of hydroxy ketone 18 (5.14 g,
18.6 mmol) in acetonitrile (3 mL, 2ꢂ1 mL rinse). The reac-
tion mixture was stirred at ꢀ25 ꢁC for 1 h and at ꢀ15 ꢁC
for 34 h. The mixture was diluted with 0.5 M aqueous Na/K
tartrate (350 mL) and vigorously stirred at room temperature
for 1 h. The organic layer was separated, and the aqueous
layer was extracted with EtOAc (3ꢂ50 mL). The organic
layer and the extracts were combined, washed with H2O
(200 mL), saturated aqueous NaHCO3 (3ꢂ200 mL), and
brine (200 mL), respectively, dried (Na2SO4), and concen-
trated to give a crude diol (5.73 g).
4.1.13. Tosylate 21. To a stirred solution of alcohol 20
(1.00 g, 4.38 mmol) in pyridine (2.2 mL) cooled at 0 ꢁC
was added p-toluenesulfonyl chloride (1.50 g, 7.87 mmol),
and the mixture was stirred at 0 ꢁC for 6 h. The mixture
was diluted with H2O (15 mL), stirred at room temperature
for 30 min, and extracted with ether (3ꢂ15 mL). The com-
bined extracts were washed with brine (15 mL), dried
(Na2SO4), and concentrated. The residual oil was purified
by column chromatography on silica gel (50 g, hexane–ether
5:1/3:1) to give 21 (1.67 g, 100%) as a colorless oil: TLC,
Rf 0.60 (hexane–ether 1:1); [a]2D6 ꢀ3.87 (c 1.08, CHCl3); IR
(neat) 1598, 1495, 1224, 794, 706 cmꢀ1
;
1H NMR
(270 MHz, CDCl3) d 7.79 (d, J¼7.9 Hz, 2H), 7.34 (d,
J¼7.9 Hz, 2H), 5.65 (ddq, J¼0.8, 15.1, 6.2 Hz, 1H), 5.40
(ddq, J¼7.0, 15.1, 1.6 Hz, 1H), 4.23 (m, 1H), 4.15 (dd,
J¼9.5, 4.0 Hz, 1H), 3.98 (dd, J¼6.8, 9.5 Hz, 1H), 3.16
(dd, J¼6.2, 7.6 Hz, 1H), 2.45 (s, 3H), 1.92 (m, 1H), 1.74
(m, 1H), 1.70 (dd, J¼1.6, 6.2 Hz, 3H), 1.24 (s, 6H), 0.97
(d, J¼6.8 Hz, 3H), 0.84 (d, J¼6.8 Hz, 3H); MS (FAB) m/z
405 (M+Na)+; HRMS (ESI) calcd for C20H30NaO5S
(M+Na)+ 405.1712, found 405.1720.
To a solution of the diol (5.73 g) in acetone (77 mL) and 2,2-
dimethoxypropane (77 mL) was added pyridinium p-tolu-
enesulfonate (487 mg, 1.94 mmol). The mixture was stirred
at room temperature for 1.5 h and diluted with saturated
aqueous NaHCO3 (150 mL). The organic layer was sepa-
rated, and the aqueous layer was extracted with ether
(3ꢂ100 mL). The organic layer and the extracts were com-
bined, washed with brine (100 mL), dried (Na2SO4), and
concentrated. The residual oil was purified by column chro-
matography on silica gel (100 g, hexane–ether 10:1) to give
19 (4.97 g, 84%) as a colorless oil: TLC, Rf 0.89 (hexane–
ether 1:1); [a]2D6 ꢀ10.9 (c 0.862, CHCl3); IR (neat) 1222,
4.1.14. Nitrile 22. To a stirred solution of tosylate 21 (1.04 g,
2.72 mmol) in DMSO (15 mL) was added sodium cyanide
(656 mg, 13.4 mmol) at room temperature, and the reaction
mixture was stirred at 50 ꢁC for 2 h. After cooling, the mix-
ture was diluted with H2O (38 mL) and extracted with ether
(4ꢂ40 mL). The combined extracts were washed with brine
(30 mL), dried (Na2SO4), and concentrated. The residual oil
was purified by column chromatography on silica gel (25 g,
hexane–ether 10:1/5:1) to give 22 (633 mg, 98%) as a
colorless oil: TLC, Rf 0.63 (hexane–ether 1:1); [a]2D6 ꢀ19.5
1
735, 698 cmꢀ1; H NMR (270 MHz, CDCl3) d 7.34–7.24
(m, 5H), 5.67 (ddq, J¼0.8, 15.4, 5.9 Hz, 1H), 5.45 (ddq,
J¼7.0, 15.4, 1.6 Hz, 1H), 4.52 (d, J¼11.9 Hz, 1H), 4.47
(d, J¼11.9 Hz, 1H), 4.28 (m, 1H), 3.60 (dd, J¼4.9, 9.2 Hz,
1H), 3.36 (dd, J¼7.0, 9.2 Hz, 1H), 3.28 (dd, J¼5.1,
7.3 Hz, 1H), 1.96 (m, 1H), 1.89 (m, 1H), 1.71 (dd, J¼1.6,
5.9 Hz, 3H), 1.32 (s, 6H), 1.02 (d, J¼7.0 Hz, 3H), 0.87 (d,
J¼7.0 Hz, 3H); 13C NMR (67.8 MHz, CDCl3) d 138.7,
128.6, 128.2, 127.5, 127.4, 127.3, 100.3, 76.2, 73.1, 72.2,
70.9, 38.0, 37.7, 25.8, 23.7, 18.0, 14.4, 13.4; MS (FAB)
m/z 341 (M+Na)+; HRMS (ESI) calcd for C20H30NaO3
(M+Na)+ 341.2093, found 341.2094.
(c 0.91, CHCl3); IR (neat) 2246, 1224 cmꢀ1 1H NMR
;
(270 MHz, CDCl3) d 5.69 (m, 1H), 5.44 (ddq, J¼7.0, 15.4,
1.2 Hz, 1H), 4.30 (m, 1H), 3.15 (dd, J¼7.0, 7.0 Hz, 1H),
2.45 (m, 2H), 1.95 (m, 1H), 1.74 (m, 1H), 1.71 (dd, J¼1.2,
6.7 Hz, 3H), 1.35 (s, 3H), 1.33 (s, 3H), 1.14 (d, J¼6.7 Hz,
3H), 0.92 (d, J¼6.8 Hz, 3H); 13C NMR (67.8 MHz,
CDCl3) d 127.9, 127.9, 118.9, 100.6, 76.8, 70.5, 39.1,
35.1, 25.6, 23.6, 20.6, 18.0, 16.2, 13.5; MS (FAB) m/z 260
(M+Na)+; HRMS (ESI) calcd for C14H23NaO2 (M+Na)+
260.1626, found 260.1605.
4.1.12. Alcohol 20. Calcium (1.37 g, 34.2 mmol) was added
to a stirred solution of acetonide 19 (4.96 g, 15.6 mmol) in
THF (250 mL), isopropyl alcohol (85 mL), and liquid NH3
(170 mL) cooled at ꢀ78 ꢁC. After the mixture was stirred
at ꢀ78 ꢁC for 2 h, NH4Cl (14.3 g) and Fe(NO3)3$9H2O
(2.5 g) were added. The mixture was stirred at ꢀ78 ꢁC for
1 h and allowed to warm to room temperature. The residue
was diluted with H2O (400 mL), and the mixture was stirred
at room temperature for 1 h and extracted with EtOAc
(5ꢂ100 mL). The combined extracts were washed with
brine (100 mL), dried (Na2SO4), and concentrated. The re-
sidual oil was purified by column chromatography on silica
gel (150 g, hexane–ether 3:1/2:1) to give 20 (3.49 g, 98%)
as a colorless oil: TLC, Rf 0.40 (hexane–ether 1:1); [a]D32
ꢀ33.2 (c 1.25, CHCl3); IR (neat) 3455 (br), 1678,
4.1.15. Aldehyde 23. To a stirred solution of nitrile 22
(456 mg, 1.92 mmol) in CH2Cl2 (7.7 mL) cooled at
ꢀ78 ꢁC was added a 1.0 M solution of diisobutylaluminum
hydride in hexane (2.4 mL, 2.4 mmol). The solution was
stirred at ꢀ78 ꢁC for 70 min, and the reaction was quenched
by addition of MeOH (3 mL). After the mixture was warmed
to room temperature, 0.5 M aqueous Na/K tartrate (25 mL)
was added. The resulting mixture was vigorously stirred
at room temperature for 1 h, and the organic layer was
separated. The aqueous layer was extracted with ether
(3ꢂ30 mL). The organic layer and the extracts were com-
bined, washed with brine (10 mL), dried (Na2SO4), and
1
1225 cmꢀ1; H NMR (270 MHz, CDCl3) d 5.64 (m, 1H),
5.39 (ddq, J¼7.3, 15.4, 1.6 Hz, 1H), 4.31 (m, 1H), 3.69

K. Suenaga et al. / Tetrahedron 62 (2006) 8278–8290
8285
concentrated. The residual oil was purified by column chro-
matography on silica gel (FL60D 15 g, benzene–ether
100:1/80:1/20:1) to give 23 (439 mg, 95%) as a colorless
oil: TLC, Rf 0.52 (benzene–ether 20:1); [a]2D6 ꢀ26.8 (c 0.81,
J¼7.2 Hz, 3H); MS (FAB) m/z 237 (M+Na)+. Compound
24c: TLC, Rf 0.76 (hexane–ether 1:1); [a]2D8 ꢀ17 (c 0.34,
CHCl3); IR (CHCl3) 1675, 1455, 1380, 1225 cmꢀ1 1H
;
NMR (270 MHz, CDCl3) d 5.67 (ddq, J¼0.7, 15.5, 6.3 Hz,
1H), 5.45 (ddq, J¼7.3, 15.5, 1.3 Hz, 1H), 4.48 (dd, J¼4.3,
7.6 Hz, 1H), 4.29 (ddd, J¼0.7, 5.0, 7.3 Hz, 1H), 3.34 (s,
3H), 3.30 (s, 3H), 3.13 (dd, J¼4.6, 7.3 Hz, 1H), 1.89 (ddd,
J¼3.3, 7.6, 14.2 Hz, 1H), 1.81–1.70 (m, 2H), 1.71 (dd,
J¼1.3, 6.3 Hz, 3H), 1.40 (ddd, J¼4.3, 9.6, 14.2 Hz, 1H),
1.32 (s, 6H), 0.99 (d, J¼6.6 Hz, 3H), 0.87 (d, J¼7.2 Hz,
3H); MS (FAB) m/z 309 (M+Na)+; HRMS (ESI) calcd for
C16H30NaO4 (M+Na)+ 309.2042, found 309.2048.
CHCl3); IR (neat) 2725, 1726, 1225 cmꢀ1 1H NMR
;
(270 MHz, CDCl3) d 9.74 (dd, J¼2.2, 2.2 Hz, 1H), 5.69
(ddq, J¼1.0, 15.4, 6.3 Hz, 1H), 5.42 (ddq, J¼7.0, 15.4,
0.8 Hz, 1H), 4.30 (m, 1H), 3.11 (dd, J¼5.9, 7.0 Hz, 1H),
2.52 (ddd, J¼2.2, 5.4, 15.9 Hz, 1H), 2.31 (ddd, J¼2.2, 6.8,
15.9 Hz, 1H), 2.21 (m, 1H), 1.75 (m, 1H), 1.71 (dd, J¼0.8,
6.3 Hz, 3H), 1.31 (s, 6H), 1.03 (d, J¼6.8 Hz, 3H), 0.90 (d,
J¼7.0 Hz, 3H); 13C NMR (67.8 MHz, CDCl3) d 202.2,
128.2, 127.7, 100.5, 78.4, 70.7, 47.7, 39.1, 33.2, 25.6,
23.6, 18.0, 17.1, 13.5; MS (FAB) m/z 263 (M+Na)+;
HRMS (ESI) calcd for C14H25O3 (M+H)+ 241.1804, found
241.1817.
4.1.17. Benzyl ether 25. To a stirred solution of methyl ace-
tal 24a (771 mg, 3.60 mmol) in DMF (11 mL) cooled at 0 ꢁC
were added benzyl bromide (1.3 mL, 11 mmol) and sodium
hydride (438 mg of 60% dispersion in mineral oil,
11 mmol), successively. The mixture was stirred at room
temperature for 3 h, cooled to 0 ꢁC, and diluted with H2O
(20 mL) and saturated aqueous NH4Cl (40 mL). The mixture
was extracted with ether (3ꢂ30 mL), and the combined
extracts were washed with saturated aqueous NaHCO3
(2ꢂ30 mL) and brine (30 mL), dried (Na2SO4), and concen-
trated. The residual oil was purified by column chromato-
graphy on silica gel (FL60D 50 g, hexane–ether 40:1/
20:1) to give 25 (1.04 g, 95%) as a colorless oil: TLC, Rf
0.56 (hexane–ether 5:1); [a]2D6 ꢀ26.8 (c 0.81, CHCl3); IR
4.1.16. Methyl acetal 24a. Aldehyde 23 (1.06 g, 4.41 mmol)
was dissolved in a 0.009 M solution of pyridinium p-tolu-
enesulfonate (16.2 mL, 0.146 mmol) in MeOH, and the
solution was stirred at room temperature for 30 min. The
reaction was quenched by addition of triethylamine (3 mL),
and the resulting mixture was concentrated. The residual
oil was purified by column chromatography on silica gel
(FL60D 100 g, hexane–ether 10:1/7:1/6:1/5:1/4:1)
to give 24a (409 mg, 43%), 24b (319 mg), and dimethyl
acetal 24c (199 mg) as a colorless oil, respectively. Acetals
24b (319 mg) and 24c (199 mg) were dissolved in a
0.009 M solution of pyridinium p-toluenesulfonate (8.0 mL,
0.072 mmol) in MeOH. After the mixture was stirred at
room temperature for 1 h, triethylamine (1.5 mL) was
added, and the resulting mixture was concentrated. The resi-
dual oil was purified by column chromatography on silica
gel (FL60D 50 g, hexane–ether 7:1/6:1/5:1/4:1) to
give 24a (225 mg, 24%), 24b (167 mg) and 24c (46.7 mg)
as colorless oil, respectively. Further, from acetals 24b
(167 mg) and 24c (46.7 mg), acetals 24a (89 mg, 9%), 24b
(84 mg), and 24c (19 mg, 2%) were obtained by repeating
the procedure described above. Further from 24b (84 mg)
and 24c (19 mg), acetals 24a (49 mg, 5%), 24b (38 mg,
4%), and 24c (4 mg, 0.3%) were obtained again. In total,
methyl acetal 24a (772 mg, 82%) was obtained from alde-
hyde 23 (1.06 g). Compound 24a: TLC, Rf 0.37 (hexane–
ether 1:1); [a]2D6 +77.2 (c 0.97, CHCl3); IR (CHCl3) 3490
1
(neat) 2933, 1207, 734 cmꢀ1; H NMR (270 MHz, CDCl3)
d 7.27–7.11 (m, 5H), 5.57 (m, 1H), 5.42 (ddq, J¼7.3, 15.1,
1.1 Hz, 1H), 4.81 (d, J¼4.9 Hz, 1H), 4.49 (d, J¼11.9 Hz,
1H), 4.21 (d, J¼11.9 Hz, 1H), 4.13 (m, 1H), 3.60 (dd,
J¼6.8, 9.4 Hz, 1H), 3.21 (s, 3H), 2.14 (m, 1H), 1.99 (m,
1H), 1.64 (dd, J¼1.1, 6.2 Hz, 3H), 1.56 (m, 1H), 1.52 (m,
1H), 0.99 (d, J¼6.5 Hz, 3H), 0.85 (d, J¼7.0 Hz, 3H); 13C
NMR (67.8 MHz, CDCl3) d 139.5, 131.0, 128.0, 127.6,
127.1, 126.9, 104.6, 87.3, 80.1, 70.4, 54.3, 46.5, 42.5,
35.5, 19.9, 17.9, 9.6; MS (FAB) m/z 327 (M+Na)+; HRMS
(ESI) calcd for C19H28NaO3 (M+Na)+ 327.1936, found
327.1935.
4.1.18. C29–C35 segment 6. To a stirred solution of benzyl
ether 25 (69.2 mg, 0.227 mmol) in acetone (1.5 mL) and
H2O (0.5 mL) were added N-methylmorpholine-N-oxide
(40.0 mg, 0.341 mmol) and a 2.4% solution of osmium
tetroxide in tert-butyl alcohol (0.15 mL, 0.011 mmol). After
being stirred at room temperature for 2 h, sodium periodate
(133 mg, 0.622 mmol) was added. The reaction mixture was
stirred at room temperature for 30 min, diluted with satu-
rated aqueous Na2S2O3 (10 mL), and extracted with EtOAc
(3ꢂ13 mL). The combined extracts were washed with satu-
rated aqueous Na2S2O3 (13 mL) and brine (13 mL), dried
(Na2SO4), and concentrated. The residual oil was purified
by column chromatography on silica gel (3 g, hexane–ether
3:1/1:1) to give 6 (66.9 mg, 99%) as a colorless oil: TLC,
Rf 0.51 (hexane–ether 1:1); [a]2D6 +24.7 (c 1.34, CHCl3); IR
1
(br), 1670, 1455, 1380, 1235 cmꢀ1; H NMR (270 MHz,
CDCl3) d 5.67 (ddq, J¼1.1, 15.1, 6.5 Hz, 1H), 5.52 (ddq,
J¼6.2, 15.1, 1.6 Hz, 1H), 4.90 (d, J¼4.9 Hz, 1H), 4.25 (br,
1H), 3.54 (dd, J¼8.1, 8.1 Hz, 1H), 3.31 (s, 3H), 3.21 (m,
1H), 2.29 (m, 1H), 2.05 (dd, J¼7.0, 12.7 Hz, 1H), 1.79 (m,
1H), 1.70 (dd, J¼1.6, 6.5 Hz, 3H), 1.57 (ddd, J¼4.9, 10.8,
12.7 Hz, 1H), 1.04 (d, J¼6.8 Hz, 3H), 0.87 (d, J¼7.3 Hz,
3H); 13C NMR (67.8 MHz, CDCl3) d 131.4, 126.3, 104.9,
89.0, 74.4, 55.0, 44.0, 41.8, 35.8, 18.7, 17.9, 12.0; MS
(FAB) m/z 237 (M+Na)+; HRMS (ESI) calcd for C12H23O3
(M+H)+ 215.1647, found 215.1651. Compound 24b: TLC,
Rf 0.43 (hexane–ether 1:1); [a]2D9 +112 (c 0.995, CHCl3);
1
(neat) 2829, 2698, 1732, 1207, 739, 698 cmꢀ1; H NMR
1
IR (CHCl3) 3490 (br), 1675, 1450, 1380, 1230 cmꢀ1; H
(270 MHz, CDCl3) d 9.73 (d, J¼1.3 Hz, 1H), 7.41–7.25
(m, 5H), 4.92 (d, J¼4.9 Hz, 1H), 4.72 (d, J¼11.3 Hz, 1H),
4.61 (d, J¼11.3 Hz, 1H), 4.23 (dd, J¼1.3, 3.0 Hz, 1H),
3.60 (dd, J¼6.8, 10.0 Hz, 1H), 3.31 (s, 3H), 2.28 (m, 1H),
2.12 (dd, J¼6.8, 12.7 Hz, 1H), 2.10 (m, 1H), 1.66 (ddd,
J¼4.9, 9.9, 12.7 Hz, 1H), 1.11 (d, J¼6.5 Hz, 3H), 0.92 (d,
J¼7.0 Hz, 3H); 13C NMR (67.8 MHz, CDCl3) d 204.4,
NMR (270 MHz, CDCl3) d 5.70 (ddq, J¼1.0, 15.5, 6.3 Hz,
1H), 5.55 (ddq, J¼6.3, 15.5, 1.3 Hz, 1H), 4.99 (d, J¼2.3,
5.6 Hz, 1H), 4.15 (m, 1H), 3.60 (dd, J¼7.3, 7.3 Hz, 1H),
3.48 (br m, 1H), 3.34 (s, 3H), 2.30 (m, 1H), 2.04 (m, 1H),
1.81 (m, 1H), 1.73 (dd, J¼1.3, 6.3 Hz, 3H), 1.51 (ddd,
J¼2.3, 5.6, 13.5 Hz, 1H), 1.10 (d, J¼6.6 Hz, 3H), 0.95 (d,

8286
K. Suenaga et al. / Tetrahedron 62 (2006) 8278–8290
137.8, 128.3, 127.7, 127.7, 104.9, 86.4, 85.2, 73.3, 54.8,
42.9, 42.4, 35.9, 20.0, 10.7; MS (FAB) m/z 315 (M+Na)+;
HRMS (FAB) calcd for C17H24NaO4 [(M+Na)+] 315.1572,
found 315.1593; Anal. Calcd for C17H24O4: C, 69.84; H,
8.27. Found: C, 69.43; H, 8.31.
was purified by column chromatography on silica gel (30 g,
hexane–ether 5:1/1:1) to give 27 (512 mg, 89%) as a color-
less oil: TLC, Rf 0.08 (hexane–ether 4:1); [a]2D8 ꢀ9.8 (c 1.00,
1
CHCl3); IR (neat) 3460 (br), 1458, 1253, 1089 cmꢀ1; H
NMR (270 MHz, CDCl3) d 5.67 (dd, J¼6.5, 15.7 Hz, 1H),
5.48 (dd, J¼5.7, 15.7 Hz, 1H), 4.90 (d, J¼5.1 Hz, 1H),
4.29 (m, 1H), 3.98 (dt, J¼7.0, 3.2 Hz, 1H), 3.55 (t,
J¼8.1 Hz, 1H), 3.44–3.20 (m, 3H), 3.32 (s, 3H), 3.31 (s,
3H), 2.57 (m, 1H), 2.26 (m, 1H), 2.05 (dd, J¼7.0, 12.4 Hz,
1H), 1.93–1.73 (m, 2H), 1.68 (br s, OH), 1.57 (ddd, J¼5.1,
11.1, 12.4 Hz, 1H), 1.31 (ddd, J¼2.4, 9.5, 13.8 Hz, 1H),
1.25 (ddd, J¼2.4, 9.7, 13.8 Hz, 1H), 1.04 (d, J¼6.5 Hz,
3H), 0.97 (d, J¼7.0 Hz, 3H), 0.89 (s, 9H), 0.87 (d,
J¼7.0 Hz, 3H), 0.86 (s, 9H), 0.77 (d, J¼6.8 Hz, 3H), 0.05
(s, 3H), 0.04 (s, 3H), 0.00 (s, 6H); 13C NMR (67.8 MHz,
CDCl3) d 133.1, 130.3, 105.1, 89.1, 81.4, 74.8, 69.8, 65.5,
56.6, 55.2, 44.3, 42.5, 41.9, 38.1, 36.0, 33.6, 26.2, 26.1,
18.9, 18.4, 18.3, 15.9, 12.3, 10.9, ꢀ3.7, ꢀ4.2, ꢀ5.1, ꢀ5.2;
HRMS (ESI) calcd for C32H66NaO6Si2 (M+Na)+
625.4296, found 625.4288.
4.1.19. Olefin 26. To a stirred solution of C22–C28 segment
5 (744 mg, 1.30 mmol) in THF (4.3 mL) cooled at ꢀ78 ꢁC
was added a 1.52 M solution of BuLi in hexane (0.73 mL,
1.7 mmol) dropwise. The mixture was stirred at ꢀ78 ꢁC for
30 min, and then a solution of C29–C35 segment 6
(115.3 mg, 0.394 mmol) in THF (4 mL) was added dropwise,
and the resulting mixture was stirred at ꢀ78 ꢁC for 3 h. The
reaction was quenched by addition of saturated aqueous
NH4Cl (5 mL), and the mixture was extracted with ether
(3ꢂ5 mL). The combined extracts were washed with brine
(5 mL), dried (Na2SO4), and concentrated. The residual oil
was purified by column chromatography on silica gel (20 g,
hexane–ether10:1/4:1/2:1/1:1)togiveadiastereomer-
ic mixture of hydroxy sulfones (343 mg) as a colorless oil
along with recovered 5 (498 mg, 67%). The hydroxy sulfones
were employed in the next experiment without separation of
the diastereomers. To a vigorously stirred solution of the dia-
stereomeric mixture of hydroxy sulfones (343 mg) in MeOH
(13 mL) cooled at 0 ꢁC were added Na2HPO4 (965 mg,
6.80 mmol) and 5% sodium amalgam (2.2 g, 4.8 mmol).
The mixture was stirred at 0 ꢁC for 2 h, diluted with saturated
aqueous NH4Cl (10 mL), then stirred at room temperature for
30 min, and extracted with ether (3ꢂ20 mL). The combined
extracts were washed with brine (10 mL), dried (Na2SO4),
and concentrated. The residual oil was purified by column
chromatography on silica gel (6 g, hexane–ether 10:1/
5:1) to give olefin 26 (196 mg, 72% from 6) as a colorless
oil: TLC, Rf 0.51 (hexane–ether 4:1); [a]2D5 ꢀ19.6 (c 1.00,
4.1.21. Alcohol 28. A mixture of alcohol 27 (369 mg,
0.612 mmol), NaHCO3 (206 mg, 2.45 mmol), and 5% Pd
on carbon (121 mg) in ethanol (6 mL) was stirred under a
hydrogen atmosphere at room temperature for 18 h. The
mixture was filtered through a pad of Celite, and the residue
was washed with EtOAc. The filtrate and the washings were
combined and concentrated. The residual oil was purified by
column chromatography on silica gel (20 g, hexane–ether
5:1/1:1) to give 28 (353 mg, 95%) as a colorless oil:
TLC Rf 0.63 (hexane–ether 1:1); [a]2D6 +1.8 (c 1.00,
CHCl3); IR (CHCl3) 3481, 1462, 1255, 1095 cmꢀ1 1H
;
NMR (270 MHz, CDCl3) d 4.88 (d, J¼5.1 Hz, 1H), 3.96
(m, 1H), 3.83 (m, 1H), 3.54 (t, J¼7.8 Hz, 1H), 3.45 (dd,
J¼7.6, 10.3 Hz, 1H), 3.33 (dd, J¼6.5, 10,3 Hz, 1H), 3.21
(m, 1H), 3.30 (s, 3H), 3.28 (s, 3H), 2.24 (m, 1H), 2.05 (dd,
J¼7.0, 12.3 Hz, 1H), 1.90–1.35 (m, 8H), 1.33–1.27 (m,
2H), 1.03 (d, J¼6.5 Hz, 3H), 0.93 (d, J¼7.0 Hz, 3H), 0.86
(s, 9H), 0.86 (s, 9H), 0.83 (d, J¼7.0 Hz, 3H), 0.79 (d,
J¼6.8 Hz, 3H), 0.04 (s, 3H), 0.04 (s, 3H), 0.00 (s, 6H);
HRMS (ESI) calcd for C32H69O6Si2 (M+H)+ 605.4633,
found 605.4649.
CHCl3); IR (neat) 1470, 1254, 1092 cmꢀ1 1H NMR
;
(270 MHz, CDCl3) d 7.36–7.20 (m, 5H), 5.62 (dd, J¼7.0,
16.0 Hz, 1H), 5.46 (dd, J¼7.0, 16.0 Hz, 1H), 4.88 (d,
J¼4.9 Hz, 1H), 4.57 (d, J¼11.9 Hz, 1H), 4.35 (d, J¼
11.9 Hz, 1H), 4.20 (dd, J¼2.7, 7.0 Hz, 1H), 4.01 (dt,
J¼9.5, 2.7 Hz, 1H), 3.67 (dd, J¼7.0, 8.9 Hz, 1H), 3.47–
3.24 (m, 3H), 3.32 (s, 3H), 3.28 (s, 3H), 2.54 (m, 1H), 2.21
(m, 1H), 2.06 (dd, J¼7.6, 12.4 Hz, 1H), 1.88 (m, 1H),
1.67–1.57 (m, 2H), 1.42–1.24 (m, 2H), 1.07 (d, J¼7.0 Hz,
3H), 0.97 (d, J¼7.0 Hz, 3H), 0.92 (d, J¼7.0 Hz, 3H), 0.88
(s, 9H), 0.86 (s, 9H), 0.77 (d, J¼7.0 Hz, 3H), 0.06 (s, 3H),
0.05 (s, 3H), 0.00 (s, 6H); 13C NMR (67.8 MHz, CDCl3)
d 139.4, 135.2, 129.5, 128.0, 127.2, 127.7, 104.5, 87.3,
31.2, 80.3, 70.5, 69.8, 65.3, 56.6, 54.3, 46.4, 42.6, 42.4,
38.8, 35.4, 33.7, 26.1, 26.0, 19.9, 18.3, 18.2, 16.0, 10.7,
9.7, ꢀ3.8, ꢀ4.4, ꢀ5.3, ꢀ5.4; HRMS (ESI) calcd for
C39H72NaO6Si2 (M+Na)+ 715.4765, found 715.4727.
4.1.22. 3,4-Dimethoxybenzyloxymethyl ether 29. To a
stirred solution of alcohol 28 (607 mg, 1.00 mmol) in
CH2Cl2 (8 mL) cooled at 0 ꢁC were added diisopropylethyl-
amine (8.8 mL, 52 mmol) and the 1 M solution of (3,4-di-
methoxybenzyloxy)methyl chloride in CH2Cl2 (13 mL,
13 mmol) prepared from 3,4-dimethoxybenzyl (methyl-
thio)methyl ether according to Ref. 4c. The mixture was
stirred at room temperature for 3 h, and the reaction was
quenched by addition of MeOH (40 mL) and NaHCO3
(500 mg). The resulting mixture was stirred at room temper-
ature for 1.5 h, and H2O (20 mL) was added. The organic
layer was separated, and the aqueous layer was extracted
with hexane (5ꢂ20 mL). The organic layer and the extracts
were combined, washed with saturated aqueous NaHCO3
(20 mL), H2O (20 mL), and brine (20 mL), successively,
dried (Na2SO4), and concentrated. The residual oil was puri-
fied by column chromatography on alumina (50 g, hexane–
EtOAc 2:1) and silica gel (FL60D 25 g, benzene–acetone
100:1/50:1/20:1) to give 29 (663 mg, 84%) as a colorless
oil: TLC, Rf 0.59 (hexane–EtOAc 3:1); [a]2D5 +8.7 (c 1.00,
4.1.20. Alcohol 27. Calcium (1.13 g, 28.1 mmol) was added
to a stirred solution of olefin 26 (616 mg, 0.956 mmol) in
THF (30 mL), isopropyl alcohol (10 mL), and liquid NH3
(20 mL) cooled at ꢀ78 ꢁC. After the mixture was stirred at
ꢀ78 ꢁC for 1.5 h, NH4Cl (6.0 g) and Fe(NO3)3$9H2O
(1.3 g) were added. The mixture was stirred at ꢀ78 ꢁC for
1 h and allowed to warm to room temperature. The residue
was diluted with H2O (70 mL), and the mixture was stirred
at room temperature for 1.5 h and extracted with EtOAc
(3ꢂ50 mL). The combined extracts were washed with brine
(50 mL), dried (Na2SO4), and concentrated. The residual oil

K. Suenaga et al. / Tetrahedron 62 (2006) 8278–8290
8287
CHCl3); IR (neat) 1516, 1463, 1380, 1257, 1097,
J¼7.0 Hz, 3H), 0.88 (d, J¼7.0 Hz, 3H), 0.75 (d, J¼7.0 Hz,
3H); 13C NMR (150 MHz, CDCl3) d 149.1, 148.6, 136.3,
136.2, 135.8, 135.7, 134.7, 134.6, 134.0, 133.8, 130.9,
129.6, 129.6, 129.5, 127.7, 127.7, 127.5, 120.7, 111.4,
111.0, 104.7, 94.5, 87.3, 81.5, 78.6, 72.0, 69.5, 66.1, 56.8,
56.1, 55.9, 54.5, 43.5, 42.7, 42.0, 36.0, 35.6, 33.9, 30.7,
27.7, 27.4, 27.3, 26.9, 20.3, 19.7, 19.3, 15.1, 11.3, 8.9;
HRMS (ESI) calcd for C62H88NaO9Si2 (M+Na)+ 1055.5865,
found 1055.5845; Anal. Calcd for C62H88O9Si2: C, 72.05;
H, 8.58. Found: C, 72.53; H, 9.01.
1
1032 cmꢀ1; H NMR (270 MHz, CDCl3) d 6.86–6.73 (m,
3H), 4.81 (d, J¼4.6 Hz, 1H), 4.75 (s, 2H), 4.52 (s, 2H),
4.01 (m, 1H), 3.94 (m, 1H), 3.81 (s, 3H), 3.80 (s, 3H), 3.50
(dd, J¼6.5, 9.7 Hz, 1H), 3.45–3.10 (m, 3H), 3.17 (s, 3H),
3.17 (s, 3H), 2.16 (m, 1H), 2.02 (dd, J¼7.6, 12.7 Hz, 1H),
1.81 (m, 1H), 1.66 (m, 1H), 1.63–1.33 (m, 6H), 1.27–1.15
(m, 2H), 1.03 (d, J¼6.5 Hz, 3H), 0.83 (d, J¼7.0 Hz, 3H),
0.81 (s, 9H), 0.80 (s, 9H), 0.77 (d, J¼7.0 Hz, 3H), 0.74 (d,
J¼7.0 Hz, 3H), 0.01 (s, 3H), 0.00 (s, 3H), ꢀ0.01 (s, 6H);
13C NMR (67.8 MHz, CDCl3) d 148.9, 148.5, 130.8,
120.6, 111.4, 110.9, 104.7, 94.5, 87.3, 81.8, 78.6, 70.2,
69.5, 65.4, 57.0, 56.1, 56.0, 54.6, 43.6, 42.7, 42.5, 36.1,
35.5, 33.1, 30.8, 27.7, 26.3, 26.2, 26.1, 20.4, 18.4, 18.4,
15.6, 11.1, 9.1, ꢀ3.7, ꢀ4.2, ꢀ5.1, ꢀ5.2; HRMS (ESI) calcd
for C42H80NaO9Si2 (M+Na)+ 807.5239, found 807.5221.
4.1.25. Diol 32. To a stirred solution of TBDPS ether 31
(178 mg, 0.198 mmol) in 1,2-dimethoxyethane (5.0 mL)
was added 1 M aqueous HCl (1.2 mL). The solution was
stirred at room temperature for 7 h, cooled to 0 ꢁC, and di-
luted with ether (10 mL) and saturated aqueous NaHCO3
(10 mL). The organic layer was separated, and the aqueous
layer was extracted with ether (3ꢂ10 mL). The organic layer
and the extracts were combined, washed with brine (10 mL),
dried (Na2SO4), and concentrated. The residual oil was
purified by column chromatography on silica gel (6 g,
hexane–EtOAc 5:1/4:1/2:1) to give a diastereomeric
mixture of hemiacetals (143 mg) as a colorless oil along
with recovered 31 (54 mg, 29%). Using the same procedure
as described above, a diastereomeric mixture of hemiacetals
(399 mg) was obtained from 31 (626 mg, 0.606 mmol).
To a stirred solution of the hemiacetals (542 mg) in ethanol
(10 mL) was added sodium borohydride (71.7 mg,
1.89 mmol). The mixture was stirred at room temperature
for 1.5 h, diluted with saturated aqueous NH4Cl (10 mL),
and extracted with ether (5ꢂ20 mL). The combined extracts
were washed with brine (10 mL), dried (Na2SO4), and con-
centrated. The residual oil was purified by column chroma-
tography on silica gel (20 g, hexane–EtOAc 4:1/2:1/
1:1/EtOAc) to give 32 (590 mg, 70%) as a colorless oil:
TLC, Rf 0.2 (hexane–EtOAc 1:1); [a]2D8 ꢀ19.6 (c 1.00,
CHCl3); IR (neat) 3434, 1516, 1462, 1427, 1109,
4.1.23. Diol 30. To a stirred solution of 3,4-dimethoxy-
benzyloxymethyl ether 29 (664 mg, 0.846 mmol) in THF
(42 mL) was added a 1.0 M solution of tetrabutylammonium
fluoride in THF (2.0 mL, 2.0 mmol). The mixture was stirred
at room temperature for 2 h, diluted with saturated aqueous
NH4Cl (9 mL), and extracted with ether (3ꢂ30 mL). The
combined extracts were washed with brine (10 mL), dried
(Na2SO4), and concentrated. The residual oil was purified
by column chromatography on silica gel (20 g, hexane–
EtOAc 1:1/EtOAc) to give 30 (466 mg, 99%) as a colorless
oil: TLC, Rf 0.5 (EtOAc); [a]2D6 +6.9 (c 1.07, CHCl3);
1
IR (neat) 3428, 1516, 1265, 1095, 1029 cmꢀ1; H NMR
(270 MHz, CDCl3) d 6.83–6.71 (m, 3H), 4.78 (d,
J¼4.6 Hz, 1H), 4.75 (d, J¼9.2 Hz, 1H), 4.72 (d, J¼9.2 Hz,
1H), 4.49 (s, 2H), 3.95 (m, 1H), 3.78 (s, 3H), 3.77 (s, 3H),
3.87–3.39 (m, 5H), 3.32 (m, 1H), 3.26 (s, 3H), 3.19 (s,
3H), 2.12 (m, 1H), 1.99 (m, 1H), 1.85–1.27 (m, 10H), 1.00
(d, J¼6.5 Hz, 3H), 0.82 (d, J¼6.8 Hz, 3H), 0.78 (d,
J¼7.3 Hz, 3H), 0.71 (d, J¼6.8 Hz, 3H); 13C NMR
(67.8 MHz, CDCl3) d 148.9, 148.5, 130.7, 120.5, 111.3,
110.9, 104.8, 94.6, 87.2, 83.6, 78.4, 75.2, 69.5, 68.1, 57.5,
56.3, 56.0, 55.9, 54.7, 43.6, 42.5, 40.1, 36.1, 35.0, 30.3,
27.5, 20.4, 15.9, 13.9, 9.0; HRMS (ESI) calcd for
C30H52NaO9 (M+Na)+ 579.3509, found 579.3496.
1
1028 cmꢀ1; H NMR (270 MHz, CDCl3) d 7.72–7.56 (m,
8H), 7.45–7.26 (m, 12H), 6.88–6.78 (m, 3H), 4.78 (d,
J¼7.0 Hz, 1H), 4.71 (d, J¼7.0 Hz, 1H), 4.62 (d,
J¼11.6 Hz, 1H), 4.50 (d, J¼11.6 Hz, 1H), 4.26 (m, 1H),
3.91 (m, 1H), 3.87 (s, 3H), 3.86 (s, 3H), 3.72 (m, 1H),
3.60–3.32 (m, 5H), 2.80 (s, 3H), 2.12 (m, 1H), 1.99–1.82
(m, 2H), 1.76–1.36 (m, 9H), 1.06 (s, 9H), 1.01 (d,
J¼7.0 Hz, 3H), 0.98 (s, 9H), 0.90 (d, J¼7.0 Hz, 3H), 0.85
(d, J¼6.5 Hz, 3H), 0.74 (d, J¼6.2 Hz, 3H); 13C NMR
(67.8 MHz, CDCl3) d 149.1, 148.8, 136.1, 136.1, 135.7,
135.6, 134.5, 134.5, 133.8, 133.8, 129.8, 129.5, 129.5,
129.4, 127.6, 127.6, 127.5, 127.5, 120.5, 111.1, 111.0,
94.4, 81.1, 81.1, 77.4, 72.1, 70.4, 66.1, 59.7, 56.9, 56.1,
56.0, 42.0, 37.8, 35.4, 33.3, 32.7, 29.9, 29.7, 28.1, 27.4,
27.0, 19.8, 19.4, 17.4, 15.4, 11.6, 11.4; HRMS (ESI) calcd
for C61H88NaO9Si2 (M+Na)+ 1043.5865, found 1043.5869.
4.1.24. TBDPS ether 31. To a stirred solution of diol 30
(80.8 mg, 0.145 mmol) in DMF (1.5 mL) cooled at 0 ꢁC
were added imidazole (749 mg, 8.71 mmol) and tert-butyl-
diphenylsilyl chloride (1.1 mL, 4.4 mmol). The mixture
was stirred at room temperature for 5 h, diluted with cold
water (1 mL), and extracted with ether (3ꢂ5 mL). The com-
bined extracts were washed with brine (5 mL), dried
(Na2SO4), and concentrated. The residual oil was purified
by column chromatography on silica gel (10 g, benzene–
ether 50:1/20:1) to give 31 (113 mg, 75%) as a colorless
oil: TLC, Rf 0.7 (hexane–EtOAc 3:1); [a]2D6 +6.9 (c 1.00,
1
CHCl3); IR (neat) 1516, 1462, 1427, 1109, 1028 cmꢀ1; H
NMR (270 MHz, CDCl3) d 7.70–7.46 (m, 8H), 7.45–7.24
(m, 12H), 6.82–6.68 (m, 3H), 4.87 (d, J¼4.6 Hz, 1H), 4.84
(d, J¼7.0 Hz, 1H), 4.81 (d, J¼7.0 Hz, 1H), 4.59 (s, 2H),
4.16 (m, 1H), 3.92 (m, 1H), 3.76 (s, 3H), 3.76 (s, 3H),
3.47 (dd, J¼6.5, 10.0 Hz, 1H), 3.36 (dd, J¼7.8, 10.0 Hz,
1H), 3.25 (dd, J¼6.7, 10.0 Hz, 1H), 3.07 (s, 3H), 2.92 (m,
1H), 2.76 (s, 3H), 2.11 (m, 1H), 2.00 (m, 1H), 1.97 (dd,
J¼7.0, 12.2 Hz, 1H), 1.56–1.15 (m, 9H), 1.11 (d,
J¼6.5 Hz, 3H), 1.06 (s, 9H), 1.00 (s, 9H), 0.90 (d,
4.1.26. Trityl ether 33. To a stirred solution of diol 32
(63.5 mg, 0.0614 mmol) in pyridine (0.7 mL) was added tri-
tyl chloride (86.6 mg, 0.307 mmol) at room temperature.
The solution was stirred at 50 ꢁC for 12 h and was cooled
to room temperature. Saturated aqueous NaHCO3 (3 mL)
was added, and the mixture was stirred at room temperature
for 2 h and extracted with ether (3ꢂ5 mL). The combined
extracts were washed with brine (5 mL), dried (Na2SO4),
and concentrated. The residual oil was purified by column

8288
K. Suenaga et al. / Tetrahedron 62 (2006) 8278–8290
chromatography on silica gel (2 g, hexane–ether–Et3N
5:1:0.1/2:1:0/1:1:0) to give 33 (73.5 mg, 95%) as a
colorless oil: TLC, Rf 0.8 (hexane–EtOAc 3:1); [a]2D8 ꢀ2.3
(c 1.00, CHCl3); IR (neat) 3500, 1516, 1462, 1427, 1109,
8H), 7.43–7.27 (m, 12H), 6.88–6.78 (m, 3H), 4.98 (dd,
J¼2.7, 9.4 Hz, 1H), 4.74 (d, J¼7.0 Hz, 1H), 4.65 (d,
J¼7.0 Hz, 1H), 4.59 (d, J¼11.6 Hz, 1H), 4.46 (d,
J¼11.6 Hz, 1H), 4.25 (m, 1H), 3.86 (s, 3H), 3.86 (s, 3H),
3.86 (m, 1H), 3.74 (m, 1H), 3.67–3.32 (m, 3H), 3.02 (m,
1H), 2.80 (s, 3H), 2.18–1.90 (m, 2H), 2.04 (s, 3H), 1.86
(m, 1H), 1.80–1.15 (m, 6H), 1.05 (s, 9H), 0.97 (s, 9H),
1.03–0.75 (m, 3H), 0.91 (d, J¼7.0 Hz, 3H), 0.89 (d,
J¼6.8 Hz, 3H), 0.88 (d, J¼7.3 Hz, 3H), 0.77 (d, J¼6.8 Hz,
3H); 13C NMR (150 MHz, CDCl3) d 170.9, 148.9, 148.5,
136.1, 136.1, 135.7, 135.6, 134.6, 134.4, 133.7, 133.7,
130.6, 129.5, 129.4, 127.6, 127.5, 127.4, 120.4, 111.1,
110.7, 95.1, 81.3, 78.3, 78.2, 71.8, 69.5, 65.9, 60.7, 56.4,
55.9, 55.8, 41.7, 36.4, 34.4, 32.7, 30.9, 30.3, 29.7, 27.1,
26.7, 26.5, 21.1, 19.6, 19.1, 16.8, 15.1, 11.1, 9.4; HRMS
(ESI) calcd for C63H90NaO10Si2 (M+Na)+ 1085.5970, found
1085.5970.
1
1029 cmꢀ1; H NMR (270 MHz, CDCl3) d 7.75–7.53 (m,
8H), 7.48–7.15 (m, 27H), 6.86–6.75 (m, 3H), 4.78 (d,
J¼7.0 Hz, 1H), 4.71 (d, J¼7.0 Hz, 1H), 4.60 (d,
J¼11.6 Hz, 1H), 4.49 (d, J¼11.6 Hz, 1H), 4.26 (m, 1H),
3.84 (s, 3H), 3.83 (s, 3H), 3.82 (m, 1H), 3.55–3.30 (m,
4H), 3.21 (m, 1H), 3.03 (m, 1H), 2.85 (s, 3H), 2.11 (m,
1H), 1.97–1.70 (m, 2H), 1.66–1.31 (m, 6H), 1.05 (s, 9H),
0.97 (s, 9H), 1.13–0.88 (m, 3H), 0.89 (d, J¼6.8 Hz, 3H),
0.86 (d, J¼8.1 Hz, 3H), 0.84 (d, J¼6.5 Hz, 3H), 0.75 (d,
J¼6.8 Hz, 3H); 13C NMR (150 MHz, CDCl3) d 149.1,
148.8, 144.6, 136.3, 136.2, 135.8, 135.7, 134.6, 134.6,
133.9, 133.8, 130.0, 129.6, 129.6, 129.5, 128.8, 127.8,
127.7, 127.7, 127.6, 127.0, 120.6, 111.2, 111.0, 94.6, 86.6,
81.8, 81.1, 77.6, 72.1, 70.3, 66.0, 62.0, 56.9, 56.0, 55.9,
41.9, 38.0, 35.4, 34.1, 31.9, 29.5, 29.4, 28.2, 27.3, 26.9,
19.7, 19.3, 17.5, 15.3, 11.7, 11.3; HRMS (ESI) calcd for
C80H102NaO9Si2 (M+Na)+ 1285.6960, found 1285.6974.
4.1.29. Aldehyde 36. To a stirred solution of alcohol 35
(19.0 mg, 0.0178 mmol) in CH2Cl2 (0.2 mL) were added
pyridine (0.02 mL, 0.178 mmol) and the Dess–Martin perio-
dinane (10.3 mg, 0.0243 mmol). The mixture was stirred at
room temperature for 30 min and diluted with saturated
aqueous Na2S2O3 (2 mL) and saturated aqueous NaHCO3
(1 mL). The resulting mixture was stirred at room tempera-
ture for 30 min and extracted with ether (3ꢂ2 mL). The
combined extracts were washed with H2O (2 mL) and brine
(2 mL), dried (Na2SO4), and concentrated. The residual oil
was purified by column chromatography on silica gel
(0.3 g, hexane–ether 1:1/1:2) to give 36 (17.3 mg, 91%)
as a colorless oil: TLC, Rf 0.8 (hexane–EtOAc 1:1); [a]D28
ꢀ2.3 (c 1.00, CHCl3); IR (neat) 2719, 1730, 1516, 1238,
4.1.27. Acetate 34. To a stirred solution of trityl ether 33
(688 mg, 0.545 mmol) in pyridine (4.0 mL) were added
acetic anhydride (2.0 mL) and 4-(dimethylamino)pyridine
(30.0 mg, 0.246 mmol). The mixture was stirred at room
temperature for 12 h and concentrated. The residual oil
was purified by column chromatography on silica gel
(10 g, hexane–ether 4:1/2:1/1:1) to give 34 (725 mg,
100%) as a colorless oil: TLC, Rf 0.8 (hexane–EtOAc 3:1);
[a]2D8 +5.1 (c 1.00, CHCl3); IR (neat) 1732, 1516, 1462,
1427, 1240, 1109, 1031 cmꢀ1
;
1H NMR (270 MHz,
1
CDCl3) d 7.75–7.55 (m, 8H), 7.48–7.18 (m, 27H), 6.87–
6.77 (m, 3H), 4.99 (dd, J¼2.7, 10.0 Hz, 1H), 4.75 (d,
J¼7.0 Hz, 1H), 4.67 (d, J¼7.0 Hz, 1H), 4.60 (d,
J¼11.9 Hz, 1H), 4.46 (d, J¼11.9 Hz, 1H), 4.26 (m, 1H),
3.85 (s, 6H), 3.48 (dd, J¼7.6, 10.3 Hz, 1H), 3.43–3.34 (m,
2H), 3.20 (m, 1H), 3.13–2.92 (m, 2H), 2.81 (s, 3H), 2.36–
1.75 (m, 4H), 1.97 (s, 3H), 1.70–1.20 (m, 5H), 1.06 (s,
9H), 0.97 (s, 9H), 1.13–0.80 (m, 3H), 0.93 (d, J¼7.0 Hz,
3H), 0.89 (d, J¼7.0 Hz, 3H), 0.75 (d, J¼6.6 Hz, 3H), 0.70
(d, J¼6.6 Hz, 3H); 13C NMR (67.8 MHz, CDCl3) d 170.8,
148.9, 148.5, 144.3, 136.2, 136.1, 135.7, 135.6, 134.6,
134.6, 133.8, 133.7, 130.8, 129.5, 128.7, 127.8, 127.6,
127.6, 127.5, 126.9, 120.4, 111.3, 110.9, 95.4, 86.6, 81.5,
78.8, 77.4, 72.2, 69.7, 66.1, 61.5, 56.6, 56.1, 56.0, 42.0,
37.0, 34.9, 33.7, 31.2, 30.8, 29.8, 27.4, 27.1, 27.0, 21.3,
19.8, 19.4, 17.2, 15.3, 11.5, 9.8; HRMS (ESI) calcd for
C82H104NaO10Si2 (M+Na)+ 1327.7066, found 1327.7075.
1169, 1031 cmꢀ1; H NMR (270 MHz, CDCl3) d 9.73 (br
s, 1H), 7.76–7.55 (m, 8H), 7.48–7.22 (m, 12H), 6.89–6.79
(m, 3H), 5.01 (dd, J¼3.0, 9.5 Hz, 1H), 4.76 (d, J¼7.0 Hz,
1H), 4.66 (d, J¼7.0 Hz, 1H), 4.61 (d, J¼11.9 Hz, 1H),
4.47 (d, J¼11.9 Hz, 1H), 4.27 (m, 1H), 3.88 (s, 6H), 3.52–
3.35 (m, 3H), 3.03 (m, 1H), 2.80 (s, 3H), 2.48 (m, 1H),
2.43 (m, 1H), 2.39–1.97 (m, 3H), 1.77 (m, 1H), 1.70–1.23
(m, 6H), 1.07 (s, 9H), 0.97 (s, 9H), 0.96 (d, J¼6.8 Hz,
3H), 0.91 (d, J¼6.8 Hz, 3H), 0.89 (d, J¼7.3 Hz, 3H), 0.75
(d, J¼6.8 Hz, 3H); 13C NMR (150 MHz, CDCl3) d 201.8,
170.7, 149.1, 148.7, 136.3, 136.2, 135.8, 135.7, 134.7,
134.6, 133.9, 133.9, 130.8, 129.6, 129.6, 129.6, 129.5,
127.7, 127.7, 127.6, 120.5, 111.3, 111.0, 95.2, 81.5, 78.4,
77.8, 72.1, 69.7, 66.1, 56.6, 56.1, 55.9, 45.0, 41.9, 37.0,
34.7, 33.4, 30.7, 29.9, 29.7, 27.3, 26.9, 21.1, 19.7, 19.3,
18.2, 15.3, 11.3, 9.8; HRMS (ESI) calcd for
C68H92NaO10Si2 (M+Na)+ 1083.5814, found 1083.5833.
4.1.28. Alcohol 35. To a stirred solution of acetate 34
(52.4 mg, 0.0401 mmol) in ether (0.6 mL) was added formic
acid (0.4 mL), and the mixture was stirred at room tempera-
ture (23 ꢁC) for 15 min. The mixture was poured into satu-
rated aqueous NaHCO3 (4 mL) cooled at 0 ꢁC, and the
resulting mixture was extracted with ether (3ꢂ3 mL). The
combined extracts were washed with brine (3 mL), dried
(Na2SO4), and concentrated. The residual oil was purified
by column chromatography on silica gel (2 g, hexane–ether
2:1/1:1/1:2/1:5) to give 35 (33.0 mg, 77%) as a color-
less oil: TLC, Rf 0.4 (hexane–ether 1:5); [a]2D8 ꢀ1.1 (c 1.00,
CHCl3); IR (neat) 3497, 1731, 1516, 1240, 1109,
4.1.30. Enamide 37. A solution of aldehyde 36 (112 mg,
0.106 mmol), N-methylformamide (1.1 mL, 19 mmol), hy-
droquinone (46.3 mg, 0.421 mmol), and pyridinium p-tolu-
enesulfonate (79.4 mg, 0.316 mmol) in benzene (50 mL)
was heated to reflux for 5 h under a stream of nitrogen with
˚
continuous removal of water using molecular sieves of 3 A.
The mixture was cooled to room temperature, diluted
with triethylamine (2 mL) and saturated aqueous NaHCO3
(5 mL), and extracted with ether (3ꢂ10 mL). The combined
extracts were washed with brine (10 mL), dried (Na2SO4),
and concentrated. The residual oil was purified by column
chromatography on silica gel (20 g, hexane–EtOAc 4:1/
2:1/1:1/1:2) to give 37 (64.6 mg, 55%) as a colorless
1
1031 cmꢀ1; H NMR (270 MHz, CDCl3) d 7.69–7.58 (m,

K. Suenaga et al. / Tetrahedron 62 (2006) 8278–8290
8289
oil: TLC, Rf 0.5 (hexane–EtOAc 1:1); [a]2D8 ꢀ10.3 (c 1.00,
give a diastereomeric mixture of 39 (2.7 mg, 74%) as a color-
less oil, which was employed in the next experiment without
separation of the diastereomers: TLC, Rf 0.3 (benzene–
CHCl3); IR (neat) 1733, 1654, 1515, 1238, 1109,
1
1030 cmꢀ1; H NMR (270 MHz, CDCl3) d 8.24 [7.92] (s,
1
1H), 7.72–7.54 (m, 8H), 7.45–7.22 (m, 12H), 6.45 [7.14]
(d, J¼14.0 Hz, 1H), 6.88–6.78 (m, 3H), 4.99 (dd, J¼9.2,
14.0 Hz, 1H), 4.75 (d, J¼7.0 Hz, 1H), 4.75 (m, 1H), 4.64
[4.65] (d, J¼7.0 Hz, 1H), 4.69 (d, J¼11.9 Hz, 1H), 4.46
[4.48] (d, J¼11.9 Hz, 1H), 4.29 (m, 1H), 3.89 (s, 3H), 3.83
(s, 3H), 3.52–3.32 (m, 3H), 3.01 (m, 1H), 2.87 (s, 3H),
2.80 [2.81] (s, 3H), 2.76 (m, 1H), 2.06 (s, 3H), 2.19–1.97
(m, 2H), 2.84–1.22 (m, 4H), 1.06 (s, 9H), 0.97 (s, 9H),
1.16–0.78 (m, 3H), 0.88 (d, J¼6.8 Hz, 3H), 0.86 (d,
J¼8.1 Hz, 3H), 0.74 (d, J¼6.8 Hz, 3H). The minor counter-
parts of doubled signals in the ratio of 2:1 are in brackets;
HRMS (ESI) calcd for C65H91NNaO10Si2 (M+Na)+
1124.6079, found 1124.6060.
acetone 8:1); H NMR (400 MHz, CDCl3) d 8.26 [7.95,
8.25, 7.93]a (s, 1H), 7.69–7.56 (m, 8H), 7.43–7.27 (m,
12H), 6.47 [7.14]b (d, J¼14.0 Hz, 1H), 5.07 [5.05]c (m,
1H), 4.94 (dd, J¼6.2, 14.0 Hz, 1H), 4.76 [4.80]c (m, 1H),
4.25 (m, 1H), 3.92 (m, 1H), 3.80–3.58 (m, 2H), 3.42
[3.43]b (s, 3H), 3.38 [3.38, 3.35]d (s, 3H), 3.51–3.36 (m,
2H), 3.00 (m, 1H), 2.91 [2.86, 2.89, 2.63]a (s, 3H), 2.54 (m,
1H), 2.07 [2.08]c (s, 3H), 1.67–1.18 (m, 9H), 1.04 (s, 9H),
1.00 [0.99]c (d, J¼6.8 Hz, 3H), 0.96 (s, 9H), 0.94 [0.93,
0.91, 0.90]a (d, J¼7.3 Hz, 3H), 0.86 [0.86]b (d, J¼7.3 Hz,
3H), 0.72 (d, J¼6.8 Hz, 3H). The minor counterparts of
doubled signals in the ratios of 9:6:3:2 (superscript a), 3:2
(superscript b), 2:1 (superscript c), and 3:4:2 (superscript d)
are in brackets.
4.1.31. Alcohol 38. To a stirred solution of enamide 37
(30.0 mg, 0.0272 mmol) in CH2Cl2 (7.6 mL), tert-butyl
alcohol (0.4 mL), and 1 M phosphate buffer (pH 6, 0.4 mL)
cooled at 0 ꢁC was added 2,3-dichloro-5,6-dicyano-p-benzo-
quinone (DDQ) (8.3 mg, 0.030 mmol). The mixture was
warmed to room temperature and stirred at room temperature
for 30 min. To the mixture cooled at 0 ꢁC was added DDQ
(7.0 mg, 0.025 mmol), and the mixture was stirred at room
temperature for 40 min. Further, the mixture was cooled to
0 ꢁC and DDQ (8.0 mg, 0.029 mmol) was added. After the
mixture was stirred at room temperature for 40 min, DDQ
(7.5 mg, 0.027 mmol) was added to the mixture cooled at
0 ꢁC. The mixture was stirred at room temperature for
20 min and diluted with 1 M phosphate buffer (pH 6,
5 mL) was added. The mixture was stirred at room tempera-
ture for 1 h and extracted with ether (3ꢂ5 mL). The com-
bined extracts were washed with brine (5 mL), dried
(Na2SO4), and concentrated. The residual oil was purified
by column chromatography on silica gel (3 g, hexane–
ether–acetone 15:15:1) to give 38 (22.7 mg, 90%) as a color-
less oil: TLC, Rf 0.4 (benzene–ether–acetone 10:1:1); [a]D21
+28.3 (c 0.97, CHCl3); IR (neat) 3514, 1696, 1657, 1427,
4.1.33. Analogs 4 and 40. A solution of esters 39 (2.7 mg,
0.0026 mmol) in a 5:3:8 mixture of HF$pyridine, pyridine,
and THF (0.32 mL) was stirred at room temperature for
7 h. The mixture was diluted with EtOAc (5 mL) and poured
into saturated aqueous NaHCO3 (5 mL) cooled at 0 ꢁC, and
the resulting mixture was extracted with EtOAc (3ꢂ5 mL).
The combined extracts were washed with brine (5 mL), dried
(Na2SO4), and concentrated. The residual oil was purified by
column chromatography on silica gel (FL60D 1 g, benzene–
acetone 2:1/1:1) followed by reversed-phase HPLC [De-
velosil Ph-UG-5 (20ꢂ250 mm), 50% aqueous MeOH,
5.0 mL/min, detection at UV 215 nm] to give 4 (tR¼91 min,
0.8 mg, 55%) and 40 (tR¼97 min, 0.5 mg, 34%) as a color-
less oil, respectively. Compound 4: TLC, Rf 0.5 (benzene–
acetone 1:1); [a]2D8 +88.5 (c 0.067, CHCl3); IR (neat) 3675,
1
1575, 1488, 1237, 1202, 1043 cmꢀ1; H NMR (400 MHz,
CDCl3) d 8.30 [8.08] (s, 1H), 6.49 [7.17] (d, J¼14.0 Hz,
1H), 5.11 (m, 1H), 4.97 [4.99] (dd, J¼9.6, 14.0 Hz, 1H),
4.80 (dd, J¼2.8, 10.0 Hz, 1H), 3.93 (m, 1H), 3.79–3.29
(m, 5H), 3.50 (s, 3H), 3.40 (s, 3H), 3.37 (s, 3H), 3.20 (m,
1H), 3.03 [3.07] (s, 3H), 2.51 (m, 1H), 2.09 [2.08] (s, 3H),
1.90–1.72 (m, 2H), 1.76 (m, 1H), 1.69–1.36 (m, 6H), 1.02
[1.01] (d, J¼6.8 Hz, 3H), 0.98 (d, J¼6.8 Hz, 3H), 0.89 (d,
J¼6.8 Hz, 3H), 0.82 (d, J¼6.8 Hz, 3H). The minor counter-
parts of doubled signals in the ratio of 2:1 are in brackets;
HRMS (ESI) calcd for C28H51NNaO10 (M+Na)+ 584.3411,
found 584.3398. Compound 40: TLC, Rf 0.5 (benzene–ace-
tone 1:1); [a]2D8 +103 (c 0.042, CHCl3); IR (neat) 3648, 1575,
1488, 1237, 1202, 1043 cmꢀ1; 1H NMR (400 MHz, CDCl3)
d 8.29 [8.08] (s, 1H), 6.49 [7.16] (d, J¼14.0 Hz, 1H), 5.13
(m, 1H), 4.98 [4.99] (m, 1H), 4.82 (dd, J¼2.8, 10.8 Hz,
1H), 3.94 (m, 1H), 3.77–3.09 (m, 6H), 3.49 (s, 3H), 3.38
(s, 3H), 3.37 (s, 3H), 3.03 [3.07] (s, 3H), 2.54 (m, 1H),
2.17 [2.09] (s, 3H), 1.90–1.39 (m, 9H), 1.02 [1.01] (d,
J¼7.2 Hz, 3H), 0.95 (d, J¼6.8 Hz, 3H), 0.89 [0.89] (d,
J¼6.8 Hz, 3H), 0.83 [0.83] (d, J¼7.2 Hz, 3H). The minor
counterparts of doubled signals in the ratio of 2:1 are in
brackets; HRMS (ESI) calcd for C28H51NNaO10 (M+Na)+
584.3411, found 584.3398.
1249, 1109 cmꢀ1 1H NMR (270 MHz, CDCl3) d 8.29
;
[8.02] (s, 1H), 7.78–7.54 (m, 8H), 7.47–7.22 (m, 12H),
6.50 [7.17] (d, J¼14.3 Hz, 1H), 5.00 [5.01] (dd, J¼9.5,
14.3 Hz, 1H), 4.83 (m, 1H), 4.28 (m, 1H), 3.51–3.33 (m,
3H), 3.04 (m, 1H), 2.98 [2.96] (s, 3H), 2.81 (s, 3H), 2.57
(m, 1H), 2.50 (m, 1H), 2.10 (m, 1H), 2.15 (s, 3H), 1.44–
1.17 (m, 4H), 1.06 (s, 9H), 1.05 (d, J¼6.5 Hz, 3H), 0.97 (s,
9H), 1.16–0.78 (m, 3H), 0.88 (d, J¼6.8 Hz, 3H), 0.85 (d,
J¼6.0 Hz, 3H), 0.73 (d, J¼6.5 Hz, 3H). The minor counter-
parts of doubled signals in the ratio of 2:1 are in brackets;
HRMS (ESI) calcd for C55H79NNaO7Si2 (M+Na)+
944.5293, found 944.5297.
4.1.32. Ester 39. To a stirred solution of alcohol 38 (3.2 mg,
0.0035 mmol)and2,3-di-O-methyl-D-glyceric acid (12.8 mg,
0.0955 mmol) were added triethylamine (0.027 mL,
0.019 mmol), 2,4,6-trichlorobenzoyl chloride (0.023 mL,
0.014 mmol), and 4-(dimethylamino)pyridine (0.7 mg,
0.006 mmol). The mixture was stirred at room temperature
for 1.5 h, diluted with 10% citric acid (5 mL), and extracted
with ether (5ꢂ5 mL). The combined extracts were washed
with brine (5 mL), dried (Na2SO4), and concentrated. The
residual oil was purified by column chromatography on silica
gel (2 g, benzene–acetone 30:1/20:1/15:1/10:1) to
4.2. Actin-depolymerizing activity
The actin-depolymerizing activity of the compounds was
measured as previously described.3,6 To the 3.7 mM solution
of actin (0.30 mL, containing 10% pyrenyl actin) in G-buffer

8290
K. Suenaga et al. / Tetrahedron 62 (2006) 8278–8290
4. (a) Kigoshi, H.; Ojika, M.; Suenaga, K.; Mutou, T.; Hirano, J.;
Sakakura, A.; Ogawa, T.; Nisiwaki, M.; Yamada, K.
Tetrahedron Lett. 1994, 35, 1247–1250; (b) Kigoshi, H.;
Ojika, M.; Ishigaki, T.; Suenaga, K.; Mutou, T.; Sakakura,
A.; Ogawa, T.; Yamada, K. J. Am. Chem. Soc. 1994, 116,
7443–7444; (c) Kigoshi, H.; Suenaga, K.; Mutou, T.;
Ishigaki, T.; Atsumi, T.; Ishiwata, H.; Sakakura, A.; Ogawa,
T.; Ojika, M.; Yamada, K. J. Org. Chem. 1996, 61, 5326–
5351; (d) Suenaga, K.; Kamei, N.; Okugawa, Y.; Takagi, M.;
Akao, A.; Kigoshi, K.; Yamada, K. Bioorg. Med. Chem. Lett.
1997, 7, 269–274; (e) Kigoshi, H.; Suenaga, K.; Takagi, M.;
Akao, A.; Kanematsu, K.; Kamei, N.; Okugawa, Y.; Yamada,
K. Tetrahedron 2002, 58, 1075–1102.
was added a 0.15 M solution of MgCl2 (2.0 mL), and the
mixture was stirred at room temperature for 1 h to polymer-
ize G-actin to F-actin. To the solution of F-actin was added
various concentrations of compounds in dimethyl sulfoxide
(2.0 mL) with stirring, and the time course of depolymeriza-
tion was continuously monitored by measuring fluorescence
of pyrenyl actin (10% of total actin) with a fluorometer
(HITACHI, F-4000, equipped with a magnetic stirrer) at
25 ꢁC at 365-nm excitation and 407-nm emission wave-
lengths. The IC50 values were the concentrations required
to depolymerize F-actin to 50% of its control amplitude.
4.3. Cytotoxicity
5. Hirata, K.; Muraoka, S.; Suenaga, K.; Kuroda, T.; Kato, K.;
Tanaka, H.; Yamamoto, M.; Takata, M.; Yamada, K.;
Kigoshi, H. J. Mol. Biol. 2006, 356, 945–954.
6. Kuroda, T.; Suenaga, K.; Sakakura, A.; Handa, T.; Okamoto,
K.; Kigoshi, H. Bioconjugate Chem. 2006, 17, 524–529.
7. (a) Fusetani, N.; Yasumuro, K.; Matsunaga, S.; Hashimoto, K.
Tetrahedron Lett. 1989, 30, 2809–2812; (b) Matsunaga, S.; Liu,
P.; Celatka, C. A.; Panek, J. S.; Fusetani, N. J. Am. Chem. Soc.
1999, 121, 5605–5606.
8. Hori, M.; Saito, S.; Shin, Y.; Ozaki, H.; Fusetani, N.; Karaki, H.
FEBS Lett. 1993, 322, 151–154.
9. Saito, S.; Watabe, S.; Ozaki, H.; Fusetani, N.; Karaki, H.
J. Biol. Chem. 1994, 269, 29710–29714.
Growing cells of HeLa S3 were suspended in Eagle’s mini-
mal essential medium containing 10% fetal bovine serum,
penicillin (0.1 units/mL), streptomycin (0.1 mg/mL), and
amphotericin B (0.25 mg/mL) at 3ꢂ104 cells/mL, and
samples dissolved in DMSO were added. The mixture was
incubated at 37 ꢁC for 4 days in a CO2 incubator with a
humidified atmosphere containing 5% CO2. The number
of viable cells was assessed using an MTT (3-[4,5-di-
methylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) as-
say.22 The IC50 value (concentration required for 50%
inhibition of cell growth) was determined using a growth
curve.
10. (a) Liu, P.; Panek, J. S. J. Am. Chem. Soc. 2000, 122, 1235–
1236; (b) Panek, J. S.; Liu, P. J. Am. Chem. Soc. 2000, 122,
11090–11097.
Acknowledgements
11. (a) Klenchin, V. A.; Allingham, J. S.; King, R.; Tanaka, J.;
Marriott, G.; Rayment, I. Nature Struct. Biol. 2003, 10,
1058–1063; (b) Allingham, J. S.; Tanaka, J.; Marriott, G.;
Rayment, I. Org. Lett. 2004, 6, 597–599.
12. Suenaga, K.; Miya, S.; Kuroda, T.; Handa, T.; Kanematsu, K.;
Sakakura, A.; Kigoshi, H. Tetrahedron Lett. 2004, 45, 5383–
5386.
13. (a) Walker, M. A.; Heathcock, C. H. J. Org. Chem. 1991, 56,
5747–5750; (b) Raimundo, B. C.; Heathcock, C. H. Synlett
1995, 1213–1214.
14. Roush, W. R.; Ando, K.; Powers, D. B.; Palkowitz, A. D.;
Halterman, R. L. J. Am. Chem. Soc. 1990, 112, 6339–6348.
15. Evans, D. A.; Bartroli, J.; Shih, T. L. J. Am. Chem. Soc. 1981,
103, 2127–2129.
We are grateful to Professors Hiroshi Ozaki and Masatoshi
Hori (The University of Tokyo) for their donation of actin
and their helpful advice and discussions. This study was sup-
ported in part by the 21st Century COE program and Grants-
in-Aid for Scientific Research from Ministry of Education,
Culture, Sports, Science and Technology, The Asahi Glass
Foundation, Suntory Institute for Bioorganic Research, As-
tellas Foundation for Research on Medicinal Resources,
Shorai Foundation for Science and Technology, TARA pro-
ject (University of Tsukuba), and Research Fellowships of
the Japan Society for the Promotion of Science for Young
Scientists (JSPS) to T.K. Finally, we thank Ms. Shoko
Ueda, Mr. Tomohisa Handa, and Mr. Kengo Kanematsu
for their technical assistance.
16. Nakagawa, I.; Hata, T. Tetrahedron Lett. 1975, 1409–1412.
17. (a) Paterson, I.; Tiller, R. D. Tetrahedron Lett. 1991, 32, 1749–
1752; (b) Paterson, I.; Lister, M. A.; Ryan, G. R. Tetrahedron
Lett. 1992, 33, 4233–4236.
References and notes
18. Evans, D. A.; Chapman, K. T.; Carreira, E. M. J. Am. Chem.
Soc. 1988, 110, 3560–3578.
19. (a) Rychnovsky, S. D.; Skalitzky, D. J. Tetrahedron Lett. 1990,
31, 945–948; (b) Evans, D. A.; Rieger, D. L. Tetrahedron Lett.
1990, 31, 7099–7100; (c) Rychnovsky, S. D.; Rogers, B.; Yang,
G. J. Org. Chem. 1993, 58, 3511–3515.
20. The stereochemistry at C35 of acetals 24a and 24b was not
determined.
21. The stereochemistry of 4 and 26 concerning the 2,3-di-O-
methylglyceroyl group was determined by degradation and
chiral HPLC analyses in the same manner as that used for
mycalolide B.7b
1. (a) Fenteany, G.; Shoutian, Z. Curr. Top. Med. Chem. 2003, 3,
593–616; (b) Yeung, K.-S.; Paterson, I. Angew. Chem., Int. Ed.
2002, 41, 4632–4653.
2. (a) Yamada, K.; Ojika, M.; Ishigaki, T.; Yoshida, Y.; Ekimoto,
H.; Arakawa, M. J. Am. Chem. Soc. 1993, 115, 11020–11021;
(b) Ojika, M.; Kigoshi, H.; Ishigaki, T.; Yamada, K.
Tetrahedron Lett. 1993, 34, 8501–8504; (c) Ojika, M.;
Kigoshi, H.; Ishigaki, T.; Nisiwaki, M.; Tsukada, I.; Mizuta,
K.; Yamada, K. Tetrahedron Lett. 1993, 34, 8505–8508; (d)
Ojika, M.; Kigoshi, H.; Ishigaki, T.; Tsukada, I.; Tsuboi, T.;
Ogawa, T.; Yamada, K. J. Am. Chem. Soc. 1994, 116, 7441–
7442.
22. Alley, M. C.; Scudiero, D. A.; Monks, A.; Hursey, M. L.;
Czerwinski, M. J.; Fine, D. L.; Abbott, B. J.; Mayo, J. G.;
Shoemaker, R. H.; Boyd, M. R. Cancer Res. 1988, 48, 589–601.
3. Saito, S.; Watabe, S.; Ozaki, H.; Kigoshi, H.; Yamada, K.;
Fusetani, N.; Karaki, H. J. Biochem. 1996, 120, 552–555.