A practical semi-synthesis of tautomycin using a hydrolysate of natural tautomycin

Article abstract of DOI:10.1016/j.tet.2003.09.097

A useful and brief semi-synthesis of tautomycin, which can be supplied a large quantity, has been achieved through the coupling reaction of the C21-C26 segment (an epoxide) with the C1-C20 segment (a dithiane), which was derived from the degradation of natural tautomycin, toward the conformational analysis of the C21-C26 moiety and the exploration of structure-activity relationships.

Full text of DOI:10.1016/j.tet.2003.09.097

Tetrahedron 59 (2003) 9609–9617
A practical semi-synthesis of tautomycin using a hydrolysate of
natural tautomycin
*
Masakuni Kurono and Minoru Isobe
Laboratory of Organic Chemistry, Graduate School of Bioagricultural Sciences, Nagoya University, Furocho, Chikusa,
Nagoya 464-8601, Japan
Received 1 September 2003; revised 29 September 2003; accepted 30 September 2003
Abstract—A useful and brief semi-synthesis of tautomycin, which can be supplied a large quantity, has been achieved through the coupling
reaction of the C21–C26 segment (an epoxide) with the C1–C20 segment (a dithiane), which was derived from the degradation of natural
tautomycin, toward the conformational analysis of the C21–C26 moiety and the exploration of structure–activity relationships.
q 2003 Elsevier Ltd. All rights reserved.
1. Introduction
tautomycin (C17–C70) resulting in PP2A selective
inhibitory activity.6k We assumed that the conformation of
C21–C26 moiety of 1 might bear key issues of the
inhibitory activity. In order to confirm this issue, we have
to prepare several compounds labeled and/or analogous to
tautomycin. Total synthesis approach would not always
suitable for such purposes, even though we have already
accomplished the total synthesis.6e,i During the course of
structural studies of tautomycin, Ubukata et al. reported that
an unsaturated ketone 3 resulted as alkaline hydrolysate of 1
under weakly basic conditions (MeOH, 20% Cs2CO3, pH
9).4 Because of the fact that tautomycin is a fermentation
product, we already utilized this hydrolysate 3 for the semi-
syntheses of several unnatural tautomycin analogs, which
were all inactive.6j In order to prepare the labeled
tautomycin itself, we searched for an alternative and
practical semi-synthetic route starting from 3. We have
recently prepared the 100%-13C-labeled tautomycin at the
18, 19, 21, and 22-positions for the purpose of elucidation of
the dynamics and conformation of C17–C26 moiety
through total synthesis pathway (Tsuboi and Isobe et al.,
unpublished result). This method would help us to prepare
the required tautomycin analogs as well for modification of
the maleic segment. Here we have established a practical
synthetic pathway to tautomycin from the enone 3 along this
line (Fig. 1).
Tautomycin (1) was isolated from Streptomyces spiroverti-
cillatus in 1987 by Isono and co-workers as an antibiotics
with strong antifungal activity against Sclerotinia
sclerotiorum,1 and 1 shows a specific inhibitor of protein
phosphatase 1 and 2A.2 It has been reported that PP1 or
PP2A were inhibited by natural products such as okadaic
acid, calyculin, and microcystin-LR.3 These three com-
pounds inhibit PP2A much more strongly than PP1, on the
other hand, tautomycin 1 inhibits PP1 more selectively than
PP2A.3These activities promoted the synthetic chemists,
and four groups have reported the four different total
syntheses of tautomycin including this research group in
1995.4–10 Structure–activity relationship was reported from
various sources with natural and synthetic derivatives.5–8
We have been studying the structural relationship from view
point of the molecular shape of 1 and the protein-
phosphatase inhibitory activity. Initially 1 was regarded as
a tautomeric compound and named accordingly,1 later it
became apparent that 1 exists in two forms in equilibrium
between acid anhydride (1a) and diacid forms (1b).4 In
1996, we separated the 2 forms 1a and 1b by HPLC and
proved that 1a did not show any inhibitory activity and that
only diacid 1b was truly active.6j Some other groups
confirmed the importance of the anhydride moiety.8b,11
Furthermore, we recently showed the importance of the
hydrophobic spiroketal moiety of tautomycin in selective
inhibition of PP; okadaic acid–tautomycin hybrid com-
pound, which have right-end segment of okadaic acid
(C28–C38 spiroketal structure) and left-hand segment of
2. Synthesis of C1–C20 segment
Tautomycin (1) was purified with an ODS column by a
modified procedure (see Section 5) of the method described
previously.1 Treatment of 1 with dil. cesium carbonate
(Cs2CO3) in MeOH at pH 9 provided the degradation
product 3.4 We proposed this reaction mechanism to include
Keywords: tautomycin; synthesis; proteinphosphatase; inhibitor.
*
Corresponding author. Tel.: þ81-52-789-4109; fax: þ81-52-789-4111;
e-mail: isobem@agr.nagoya-u.ac.jp
0040–4020/$ - see front matter q 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2003.09.097

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M. Kurono, M. Isobe / Tetrahedron 59 (2003) 9609–9617
Figure 1.
trans-esterification and concomitant elimination to give the
enone 3.6j The synthesis of converting it into segment
C1–20 (compound 10) is summarized in Scheme 1. The
protection of the hydroxyl group of 3 by treatment with
t-butyldimethylsilyl trifluoromethanesulfonate (TBSOTf)
and 2,6-lutidine gave the silyl vinyl ether 4, which was
successively treated with dil. acetic acid (AcOH) in THF at
room temperature for 12 h. Under these conditions, the silyl
vinyl ether moiety was selectively cleaved to give 5.
Reduction of 5 with sodium borohydride (NaBH4) in MeOH
led to exclusive 1,2-reduction to give a diastereomeric
mixture (C2 and C20) of the allylic alcohol 6. We performed
oxidative cleavage of the allylic alcohol under Lemieux–
Johnson condition.12 No oxidative cleavage, however, was
observed under various conditions. Dihydroxylation with
osmium tetroxide (OsO4) did not occur under a condition
using 4-(dimethylamino)pyridine (DMAP) (used for the
purpose of in situ generation of more reactive OsO4-
DMAP).13 It may be due to strong steric congestion around
the olefin. Fortunately, treatment of the allylic alcohol with
ozone worked well in CH2Cl2 at 2788C, which was
followed by reductive cleavage of the resulting ozonide
with NaBH4 to provide an diastereomeric mixture of the
triol 7 in 76% yield. The 1,2-glycol moiety of 7 was cleaved
with sodium metaperiodate (NaIO4), which was success-
ively treated with pyridinium chlorochromate (PCC) in the
˚
presence of molecular sieves 4 A to furnish the C1–C20
segment. Thioketalization at the C20 and C2 positions
furnished the protected C1–C20 segment 10 in 59% yield.
No epimerization occurred at the C3 stereogenic center by
employing the similar conditions as our previous synthesis
of tautomycin.6i Since TBS group at C18 was partly
deprotected, the resulting alcohol 11 was re-protected as a
TBS ether 10 in 99% yield.
3. Semi-synthesis of tautomycin
The segment coupling is summarized in Scheme 2. The
coupling reaction between the anion of dithiane 10 and the
epoxide 12 was the key element of our synthetic program,
and it had previously been defined as Segment B1 in our
total synthesis.6i Treatment of the dithiane 10 with
t-butyllithium (tBuLi) at 2438C for 1 h in 20% hexa-
methylphosphoramide (HMPA)/THF gave the correspond-
ing dithiane carbanion, which was confirmed by reddish
color. To this solution was added the C21–C26 segment
126g at 2788C, and the temperature was allowed to warm to
2508C, then maintained at 2508C for 1 h. After work-up,
the coupling product 13 was separated by silica gel column
chromatography and isolated in 87% yield. The excess
Scheme 1. Reagents and conditions: (a) TBSOTf, 2,6-lutidine, 2108C,
10 min, then room temperature, 40 min; (b) AcOH–THF–H2O¼3:1:1,
room temperature, 12 h, 90% (2 steps); (c) NaBH4, MeOH, 08C, 30 min,
85%; (d) O3/CH2Cl2, 2788C, 20 min, then NaBH4/MeOH, 2788C to room
temperature, 76%; (e) NaIO4, THF–H2O¼4:1, 08C, 30 min, then room
˚
temperature, 30 min, quant.; (f) PCC, MS 4 A, room temperature, 1.5 h,
83%; (g) HS(CH2)3SH/BF3·OEt2, 12 mM, 08C, 1 h, then room temperature,
24 h, 59%, 11, 38%; (h) TBSOTf, 2,6-lutidine, 08C, 30 min, 99%.

M. Kurono, M. Isobe / Tetrahedron 59 (2003) 9609–9617
9611
fermentation in 10 gram scale. Further synthetic studies
are in progress with respect to 13C incorporated tauto-
mycins. And the corresponding bioorganic studies including
PP1g (protein phosphatase) will be published elsewhere.
5. Experimental
5.1. General methods
Infrared spectra (IR) were recorded on a JASCO FT/IR-
8300 spectrophotometer and are reported in wave number
(cm21). Proton nuclear magnetic resonance (1H NMR)
spectra were measured with a BRUKER ARX-400 or an
AMX-600 spectrometers. Chemical shifts are reported in
parts per million (ppm) relative to the residual undeuterated
CHCl3 (d¼7.26 ppm) as an internal standard. Data are
reported as follows; chemical shift, integration, multiplicity
(s¼singlet, d¼doublet, t¼triplet, q¼quartet, qn¼quintet,
sext¼sextet, oct¼octet, br¼broadened, m¼multiplet),
coupling constant(s), and assignment, respectively. Carbon
nuclear magnetic resonance (13C NMR) spectra were
measured with a BRUKER ARX-400 or an AMX-600
spectrometers. Chemical shifts are reported in ppm using
CDCl3 (d¼77.0 ppm) as an internal standard. 2D NMR
(COSY, HMQC, and HMBC) were measured with a
BRUKER ARX-400 or AMX-600 spectrometers. Tauto-
mycin numbering corresponding to the front page is
Scheme 2. Reagents and conditions: (a) t-BuLi, 20% THF–HMPA, 250 to
2438C, 1 h, then 12, 278 to 2508C, 1 h, 87%; (b) Ac2O, pyridine, DMAP,
room temperature, 12 h; (c) DDQ, CH2Cl2–H2O¼10:1, room temperature,
1 h; (d) MeOH, CaCO3, room temperature, 7 h, 76% (3 steps); (e) Cl3C6-
H2COCl, Et3N, DMAP, 84%; (f) (HF)x·Py, THF, room temperature, 12 h;
(g) Hg(ClO4)2, CaCO3, CH3CN, H2O, room temperature, 3 min, 69%
(2 steps).
1
employed for assignment of H NMR. Optical rotations
were measured on a JASCO DIP-370 digital polarimeter.
MS spectra were measured utilizing a Micromass Q-TOF
mass spectrometer equipped with a Z-spray type ESI source
and are reported in m/z. Low-resolution mass spectra (FAB)
were recorded on a JEOL M Station and reported in m/z.
Elemental analyses was performed by Mr S. Kitamura in
Analytical Laboratory at Bioagricultural Sciences, Nagoya
University to whom the authors gratefully acknowledge.
Reactions were monitored by thin-layer chromatography
(TLC) carried out on 0.25 mm silica gel coated glass
plates 60F254 using UV light as visualizing agent and
12.molybdo(VI)phosphoric acid n-hydrate or p-anis-
aldehyde solution and heated as developing agents. Silica
gel 60 (particle size 0.063–0.2 mm ASTM) was used for
open-column chromatography. Dry THF was distilled from
potassium metal with benzophenone indicator under N2
atmosphere. Dry CH2Cl2 was distilled from CaH2 under N2
atmosphere. Pyridine and Et3N were dried over anhydrous
KOH. BF3·OEt2 was distilled from CaH2. All other
commercially available reagents were used as received.
C1–C20 segment 10 was recovered in 43% yield. The
protective p-methoxybenzyl (PMB) group of 13 was
removed in 3 steps; thus, (i) acetylation at the C22 hydroxyl
group, (ii) oxidative cleavage of the PMB group with 2,3-
dichloro-5,6-dicyano-1,4-benzoquinone (DDQ),14 and (iii)
hydrolysis of the temporary acetate to provide the diol 14 in
76% overall yield. This compound was identical with the
authentic compound, which had been prepared, during the
course of the total synthesis under the similar condition.6i
Selective esterification of 14 with the maleic segment 156c
under Yamaguchi condition15 proceeded expectedly to
afford the desired product 16 in 88% yield as reported
previously.6i Two-step deprotection of 16 was achieved to
remove TBS groups with poly(hydrogen fluoride)pyridine
complex ((HF)x·Py)16 and to cleave the two dithioketals
using mercury perchlorate (Hg(ClO4)2) in aqueous aceto-
nitrile.17 The semi-synthetic tautomycin was obtained in
69% yield in two steps. The synthetic material was proved
Tautomycin (1) was kindly provided by ex-Professor
K. Isono (Tokai University) and further purified by the
procedure of the method described previously with slight
modification. The purification system of tautomycin is
shown in Figure 2.
1
to be identical in all respects ([a]D, H and 13C NMR, IR,
MS) with natural tautomycin.
4. Conclusion
5.1.1. Purification of natural tautomycin (1). A crude
tautomycin 1 (550 g) was suspended CH2Cl2 (300 ml) and
filtrated through Celite pad. The filtrate was concentrated to
give a dark brown oil (423 g). This oil was roughly purified
by silica gel column chromatography (4 kg). It was then
eluted with CH2Cl2 (8 l) followed by 5% MeOH/CH2Cl2
(24 l) and 30% MeOH/CH2Cl2 (16 l). 5% MeOH/CH2Cl2
A useful and alternative synthetic route of tautomycin has
been established through the coupling reaction of the
epoxide 12 (C21–C26 segment) with the dithiane anion of
10 (C1–C20 segment) in 16% overall yield in 16 steps from
natural tautomycin (1), which was available through

9612
M. Kurono, M. Isobe / Tetrahedron 59 (2003) 9609–9617
MS calcd for C41H66NaOþ13 [MþNa]þ 789.4401, found
789.4387.
5.1.2. Enone (3). To a solution of tautomycin 1 (30.0 mg,
0.039 mmol) in MeOH (2.0 ml) was added dropwise 20%
Cs2CO3 solution (about 3.2 ml) until the mixture solution
reached pH 9. After being stirred for 3 h at 08C, the reaction
mixture was allowed to warm to room temperature and
stirred for 2 h. While the reaction went on, the solution was
kept to pH 9. The solution was adjusted to pH 5 with 1N
HCl, and the MeOH was evaporated off. The resulting
mixture was extracted with AcOEt (£3), washed with water
(£3) and brine. The combined organic extracts were dried
over Na2SO4 and then concentrated to give a brown oil
(30.1 mg). Purification by column chromatography (silica
gel 2 g, ether/hexane¼2/1) gave the pure enone 3 (20.3 mg,
1
92%) as a colorless oil. 3: H NMR (400 MHz, CDCl3) d
0.79 (3H, d, J¼6.5 Hz, 7-CH3), 0.88 (3H, d, J¼7.5 Hz, 13-
CH3), 0.90 (3H, d, J¼7.0 Hz, 25-CH3), 0.99 (3H, d,
J¼6.5 Hz, 15-CH3), 0.99 (3H, d, J¼7.0 Hz, H-26), 1.09
(3H, d, J¼7.0 Hz, 3-CH3), 1.18 (3H, d, J¼7.0 Hz, 19-CH3),
1.20–1.73 (18H, m, H-4a, 4b, 5a, 5b, 7, 8a, 8b, 9a, 9b, 11a,
11b, 12a, 15, 16a, 16b, 17a, 17b, 25), 1.84 (1H, m, H-13),
2.01 (1H, m, H-12b), 2.14 (3H, s, H-1), 2.29 (1H, br s, OH),
2.53 (1H, sext, J¼7.0 Hz, H-3), 2.76 (1H, br s, OH), 2.94
(1H, dq, J¼7.5, 7.0 Hz, H-19), 3.16 (1H, td, J¼10.0, 2.0 Hz,
H-6), 3.26 (1H, dd, J¼10.0, 2.5 Hz, H-14), 3.33 (3H, s,
23-OCH3), 3.48 (1H, dd, J¼7.5, 4.5 Hz, H-24), 3.69 (1H, m,
H-18), 3.81 (1H, ddd, J¼7.0, 4.5, 1.5 Hz, H-23), 6.34 (1H,
dd, J¼16.0, 1.0 Hz, H-21), 6.82 (1H, dd, J¼16.0, 7.0 Hz,
H-22). 13C NMR (100.6 MHz, CDCl3) d 10.9, 14.7, 16.1,
16.7, 17.9, 18.2, 18.9, 26.8, 27.6, 27.9, 28.1, 28.2, 29.0,
29.7, 29.8, 30.2, 30.6, 31.7, 34.8, 34.9, 36.1, 47.3, 48.6,
57.1, 74.2, 75.0, 77.8, 82.1, 95.6, 132.0, 142.7, 204.4, 212.5.
[a]2D6¼219.38 (c 0.21, CHCl3). IR (KBr): 3447, 2932, 2363,
1706, 1629, 1458, 1375, 1255, 1231, 1180, 1099, 1066, 987,
875 cm21. FAB-MS (positive p-nitrobenzyl alcohol): m/z
567 (C33H58O7, [MþH]þ), 549 ([MþH–H2O]þ). Anal.
calcd for C33H58O7: C, 69.86; H, 10.41. Found: C, 69.93; H,
10.31.
Figure 2. Purification system of tautomycin: Column A: a stainless column
(50£500 mm, 981 ml) (Nomura Chemical) was packed with Cosmosil
75C18-OPN. Column B: a stainless steel column (20£250 mm, 78.5 ml)
(Nomura Chemical) was packed with Cosmosil 75C18-OPN to which was
made stick crude tautomycin. Pump: Waters 170 P-1 (100 ml/min)
(Waters). Injector: Waters Prep LC 3000 System (Waters). Detector:
Waters 490E (254 nm) (Waters). Recorder: UNICORDER U-228 (Nippon
Denshi Kagaku).
fraction was concentrated in vacuum to give a brown oil
(220 g). To a solution of an aliquot (10.22 g) in CH2Cl2 was
added ODS silica gel (Cosmosil 75C18-OPN, 26 g), and the
suspension were concentrated to dryness. The adsorbates
were dry-packed in column (20£250 mm) which equipped
with ODS-HPLC column (50£500 mm), and then eluted
with 60% MeOH–H2O (9.0 l), 70% MeOH–H2O (7.0 l)
and 100% MeOH (3.5 l). The 70% fraction was evaporated
below 308C to removed the MeOH, and adjusted to pH 3 by
1N HCl. The suspension was extracted with CH2Cl2 (£3),
and the organic extracts were dried over Na2SO4 and
concentrated under reduced pressure to give tautomycin (1)
1
(2.52 g). 1: H NMR (CDCl3, 600 MHz) d 0.80 (3H, d,
J¼6.5 Hz, 7-CH3), 0.89 (3H, d, J¼7.0 Hz, 13-CH3), 0.97
(3H, d, J¼7.0 Hz, 25-CH3), 0.98 (3H, d, J¼7.0 Hz, 25-
CH3), 1.00 (3H, d, J¼6.5 Hz, 15-CH3), 1.10 (3H, d,
J¼7.0 Hz, 3-CH3), 1.11 (3H, d, J¼7.5 Hz, 19-CH3),
1.20–1.70 (17H, m, H-4a, 4b, 5a, 5b, 7, 8a, 8b, 9a, 9b,
11a, 11b, 12a, 15, 16a, 16b, 17a, 17b), 1.83 (1H, m, H-13),
2.01 (1H, m, H-12b), 2.11 (1H, m, H-25), 2.15 (3H, s, H-1),
2.27 (3H, d, J¼1.5 Hz, 50-CH3), 2.46 (1H, br s, OH), 2.53
(1H, sext, J¼7.0 Hz, H-3), 2.67 (1H, qn, J¼7.5 Hz, H-19),
2.67 (1H, dd,0J¼17.5, 4.0 Hz, H-21a), 2.77 (1H, dd, J¼16.5,
10.0 Hz, H-2 a), 2.92 (1H, dd, J¼16.5, 3.0 Hz, H-2’b), 2.99
(1H, dd, J¼17.5, 8.5 Hz, H-21b), 3.16 (1H, dt, J¼10.0,
2.0 Hz, H-6), 3.20 (1H, br s, OH), 3.27 (1H, dd, J¼6.0,
2.0 Hz, H-23), 3.27 (1H, dd, J¼10.0, 2.0 Hz, H-14), 3.44
(3H, s, OCH3), 3.70 (1H, br t, J¼7.0 Hz, H-18), 4.35 (1H,
m, H-22), 4.54 (1H, br s, OH), 5.10 (1H, t, J¼6.0 Hz, H-24),
5.21 (1H, br d, J¼10.0 Hz, H-30). 13C NMR (CDCl3,
150.9 MHz) d 10.2, 11.0, 13.7, 16.2, 16.7, 17.9, 18.0, 19.4,
26.8, 27.4, 27.6, 28.1, 28.1, 28.7, 29.1, 30.2, 30.7, 31.4,
34.8, 34.8, 36.0, 41.0, 45.8, 47.3, 52.4, 59.1, 63.9, 66.4,
74.3, 74.3, 74.8, 76.5, 80.6, 95.7, 142.1, 143.0, 164.8, 165.8,
169.5, 213.1, 215.3. IR (KBr): 3444, 2934, 1768, 1709,
1460, 1381, 1257, 1100, 987, 909, 732 cm21. ESI Q-TOF
5.1.3. TBS ether (5). To a solution of enone 3 (1.96 g,
3.46 mmol) dissolved in CH2Cl2 (20 ml) were added 2,6-
lutidine (6.05 ml, 51.9 mmol) and TBSOTf (5.17 ml,
22.5 mmol) at 2208C under N2 atmosphere. After being
stirred for 10 min, the reaction mixture was allowed to
warm to room temperature and stirred for 30 min. The
reaction mixture was poured into sat. NH4Cl and extracted
with CH2Cl2 (£3) washed with water (£3) and brine. The
combined organic phase was dried over Na2SO4 and then
concentrated under reduced pressure to afford the silyl vinyl
ether 4 (4.50 g).
To a solution of 4 (4.50 g) dissolved in THF (1 ml) were
added AcOH (12 ml), H2O (4 ml) and THF (3 ml) at room
temperature. After being stirred for 12 h at room tempera-
ture, the reaction mixture was poured into sat. NaHCO3 and
extracted with CH2Cl2 (£3). The combined organic phase
was washed with water (£3) and brine, dried over Na2SO4
and then concentrated to give the oil (4.57 g). Purification
by column chromatography (silica gel 250 g, ether/
hexane¼1/6) gave the pure 5 (2.47 g, 90%) as a colorless
1
oil. 5: H NMR (400 MHz, CDCl3) d 0.01 (3H, s, CH3Si),

M. Kurono, M. Isobe / Tetrahedron 59 (2003) 9609–9617
9613
0.04 (3H, s, CH3Si), 0.04 (3H, s, CH3Si), 0.05 (3H, s,
CH3Si), 0.80 (3H, d, J¼6.5 Hz, 7-CH3), 0.85 (9H, s,
SiC(CH3)3), 0.88 (3H, d, J¼7.5 Hz, 13-CH3), 0.88 (9H, s,
SiC(CH3)3), 0.90 (3H, d, J¼7.0 Hz, 25-CH3), 0.91 (3H, d,
J¼7.0 Hz, H-26), 1.01 (3H, d, J¼7.0 Hz, 15-CH3), 1.09
(3H, d, J¼7.0 Hz, 3-CH3), 0.98 (3H, d, J¼7.0 Hz, 19-CH3),
1.20–1.70 (17H, m, H-4a, 4b, 5a, 5b, 7, 8a, 8b, 9a, 9b, 11a,
11b, 12a, 15, 16a, 16b, 17a, 17b), 1.74 (1H, m, H-25), 1.84
(1H, m, H-13), 2.02 (1H, m, H-12b), 2.14 (3H, s, H-1), 2.56
(1H, sext, J¼7.0 Hz, H-3), 3.01 (1H, qn, J¼7.0 Hz, H-19),
3.16 (1H, td, J¼9.5, 2.0 Hz, H-6), 3.25 (1H, dd, J¼10.5,
2.5 Hz, H-14), 3.27 (3H, s, 23-OCH3), 3.51 (1H, dd, J¼6.0,
4.0 Hz, H-24), 3.71 (1H, ddd, J¼7.0, 4.0, 1.0 Hz, H-23),
4.01 (1H, m, H-18), 6.32 (1H, dd, J¼16.0, 1.0 Hz, H-21),
6.75 (1H, dd, J¼16.0, 7.0 Hz, H-22). 13C NMR
(100.6 MHz, CDCl3) d 24.8, 24.5, 24.4, 23.8, 10.9,
12.4, 16.0, 16.8, 18.0, 18.3, 19.6, 25.8, 25.9, 26.1, 26.7,
27.6, 28.0, 28.1, 29.1, 30.2, 30.4, 30.5, 31.3, 34.8, 34.9,
36.1, 47.3, 49.0, 56.9, 73.4, 74.3, 75.0, 79.6, 83.0, 95.6,
131.5, 143.5, 202.4, 212.7. [a]2D7¼18.88 (c 0.33, CHCl3). IR
(KBr): 2931, 2362, 1717, 1636, 1464, 1362, 1255, 1086,
987, 939, 836, 775 cm21. Anal. calcd for C45H86O7Si2: C,
67.86; H, 11.08. Found: C, 67.96; H, 10.90.
5.1.5. Triol (7). To a solution of 6 (270 mg, 0.34 mmol) in
CH2Cl2 (25 ml) was bubbled ozone until the color of
solution was blue (50 V, 30 min) at 2788C. After nitrogen
purging, to the reaction mixture was added NaBH4
(63.9 mg, 1.69 mmol) in MeOH (5 ml) at 2788C at N2
atmosphere. After being stirred for 90 min, the reaction
mixture was poured into 1N HCl. After the organic solvent
was evaporated, the resulting mixture was extracted with
AcOEt (£3). The combined organic phase was washed with
water (£3) and brine, dried over Na2SO4 and then
concentrated under reduced pressure to afford the crude 7.
Purification by column chromatography (silica gel 10 g,
ether/hexane¼2/1) gave the epimeric mixture 7 (146 g,
1
76%) as a colorless oil. 7: H NMR (400 MHz, CDCl3) d
0.09 (3H, s, CH3Si), 0.09 (3H, s, CH3Si), 0.82 (3H, d,
J¼7.0 Hz, 7-CH3), 0.86 (3H, d, J¼7.0 Hz, 19-CH3), 0.87
(3H, d, J¼7.0 Hz, 13-CH3), 0.89 (3H, d, J¼6.5 Hz, 3-CH3),
0.90 (9H, s, SiC(CH3)3), 1.00 (3H, d, J¼7.0 Hz, 15-CH3),
1.14 (1.7H, d, J¼6.5 Hz, H-1), 1.15 (1.3H, d, J¼6.5 Hz, H-
1), 1.20–1.74 (19H, m), 1.83 (3H, m, H-13, OH£2), 2.03
(1H, m, H-12b), 3.19 (0.57H, td, J¼10.0, 2.0 Hz, H-6), 3.19
(0.43H, td, J¼10.0, 2.0 Hz, H-6), 3.31 (0.57H, dd, J¼10.0,
2.5 Hz, H-14), 3.31 (0.43H, dd, J¼10.0, 2.5 Hz, H-14), 3.48
(1H, ddd, J¼11.0, 6.5, 2.0 Hz, H-18), 3.58–3.78 (5H, m,
H-2, 19, 20, 21a, 21b). 13C NMR (100.6 MHz, CDCl3) d
24.6, 24.2, 10.9, 10.9, 12.7, 12.7, 14.1, 14.7, 16.5, 18.0,
18.1, 19.7, 20.2, 25.9, 26.8, 27.2, 27.6, 27.6, 28.2, 28.3,
28.6, 29.9, 30.2, 30.6, 30.6, 30.8, 31.0, 34.7, 34.7, 35.0,
35.0, 36.1, 36.1, 39.7, 40.0, 40.0, 64.7, 64.7, 71.6, 71.7,
73.9, 74.4, 74.6, 74.8, 76.5, 76.6, 95.7, 95.7. [a]2D7¼234.48
(c 0.18, CHCl3). IR (KBr): 3421, 2928, 2360, 1653, 1560,
1457, 1255, 1058, 835, 775 cm21. Anal. calcd for
C32H64O6Si: C, 67.08; H, 11.26. Found: C, 66.89; H, 11.35.
5.1.4. Allylic alcohol (6). To a solution of 5 (2.64 g,
3.31 mmol) in MeOH (25 ml) was added NaBH4 (752 mg,
19.88 mmol) at 08C under N2 atmosphere. After being
stirred for 30 min, the reaction mixture was poured into 1N
HCl. After the organic solvent was evaporated, the resulting
mixture was extracted with AcOEt (£3). The combined
organic phase was washed with water (£3) and brine, dried
over Na2SO4 and then concentrated under reduced pressure
to afford the crude 6 (2.37 g). Purification by column
chromatography (silica gel 150 g, ether/hexane¼1/4) gave
the epimeric mixture 6 (2.24 g, 85%) as a colorless oil. 6: 1H
NMR (400 MHz, CDCl3) d 0.04 (3H, s, CH3Si), 0.06 (3H, s,
CH3Si), 0.07 (3H, s, CH3Si), 0.08 (3H, s, CH3Si), 0.82 (3H,
d, J¼7.0 Hz, 7-CH3), 0.82 (3H, d, J¼7.0 Hz, 19-CH3), 0.88
(3H, d, J¼7.0 Hz, 13-CH3), 0.88 (3H, d, J¼7.0 Hz, 3-CH3),
0.89 (3H, d, J¼7.0 Hz, 25-CH3), 0.89 (9H, s, SiC(CH3)3),
0.90 (9H, s, SiC(CH3)3), 0.91 (3H, d, J¼7.0 Hz, H-26), 1.00
(3H, d, J¼7.0 Hz, 15-CH3), 1.13 (1.7H, d, J¼7.0 Hz, H-1),
1.15 (1.3H, d, J¼7.0 Hz, H-1), 1.20–1.84 (20H, m), 1.72
(1H, oct, J¼7.0 Hz, H-25), 1.84 (1H, m, H-13), 2.04 (1H, m,
H-12b), 2.54 (1H, br s, OH), 3.19 (0.57H, td, J¼10.0,
2.0 Hz, H-6), 3.20 (0.43H, td, J¼10.0, 2.0 Hz, H-6), 3.22
(3H, s, 23-OCH3), 3.29 (0.57H, dd, J¼10.0, 2.5 Hz, H-14),
3.30 (0.43H, dd, J¼10.0, 2.5 Hz, H-14), 3.45 (1H, dd,
J¼4.0, 7.0 Hz, H-24), 3.55 (1H, dt, J¼4.0, 7.0 Hz, H-23),
3.64 (0.57H, dt, J¼6.5, 7.0 Hz, H-2), 3.72 (0.43H, dd,
J¼4.0, 7.0 Hz, H-2), 3.82 (1H, m, H-18), 4.02 (1H, dd
J¼8.0, 6.0 Hz, H-20), 5.61 (1H, dd, J¼16.0, 7.0 Hz, H-22),
5.66 (1H, dd, J¼16.0, 6.0 Hz, H-21). 13C NMR
(100.6 MHz, CDCl3) d 24.7, 24.5, 24.2, 23.6, 10.9,
10.9, 12.5, 14.3, 14.8, 16.7, 18.0, 18.1, 18.5, 18.8, 19.7,
19.7, 20.3, 25.9, 26.2, 26.8, 27.2, 27.2, 27.6, 27.6, 28.2,
28.6, 29.8, 30.2, 30.3, 30.5, 31.1, 34.9, 35.0, 35.0, 36.2,
39.7, 40.0, 43.5, 55.9, 65.8, 71.4, 71.4, 74.4, 74.5, 75.0,
75.1, 75.1, 75.2, 79.8, 79.8, 83.7, 95.7, 95.7, 96.2, 129.1,
136.3, 136.3. [a]2D6¼8.08 (c 0.12, CHCl3). IR (KBr): 3448,
2929, 2363, 1458, 1254, 1070, 835, 775 cm21. Anal. calcd
for C45H90O7Si2: C, 67.63; H, 11.38. Found: C, 67.61; H,
11.35.
5.1.6. Alcohol (8). To a solution of 7 (1.20 g, 2.09 mmol) in
THF (40 ml) was added to NaIO4 (1.34 g, 6.28 mmol) in
H2O (10 ml) at 08C. After stirring for 45 min, the reaction
mixture was allowed to warm to room temperature and
stirred for 30 min. After the solvent was evaporated, the
reaction mixture was extracted with AcOEt (£3), washed
with water (£3) and brine. The combined organic phase
were dried over Na2SO4 and then concentrated to give a
colorless oil. Purification by column chromatography (silica
gel 60 g, ether/hexane¼1/2) gave the epimeric mixture 8
1
(1.14 g, quant.) as a colorless oil. 8: H NMR (400 MHz,
CDCl3) d 0.06 (3H, s, CH3Si), 0.06 (3H, s, CH3Si), 0.82
(3H, d, J¼7.0 Hz, 7-CH3), 0.88 (3H, d, J¼7.0 Hz, 13-CH3),
0.88 (9H, s, SiC(CH3)3), 0.90 (3H, d, J¼6.5 Hz, 3-CH3),
0.99 (3H, d, J¼7.0 Hz, 15-CH3), 1.09 (3H, d, J¼7.0 Hz,
19-CH3), 1.14 (1.7H, d, J¼7.0 Hz, H-1), 1.15 (1.3H, d,
J¼7.0 Hz, H-1), 1.20–1.74 (19H, m), 1.81 (1H, m, H-13),
2.03 (1H, m, H-12b), 2.50 (1H, qdd, J¼7.0, 5.0, 2.0 Hz,
H-19), 3.18 (0.57H, td, J¼10.0, 2.0 Hz, H-6), 3.19 (0.43H,
td, J¼10.0, 2.0 Hz, H-6), 3.29 (0.57H, dd, J¼10.0, 2.5 Hz,
H-14), 3.29 (0.57H, dd, J¼10.0, 2.5 Hz, H-14), 3.65 (0.57H,
dt, J¼6.5, 7.0 Hz, H-2), 3.73 (0.43H, dd, J¼4.0, 7.0 Hz,
H-2), 3.90 (1H, q, J¼5.0 Hz, H-18), 9.75 (1H, d, J¼2.0 Hz,
H-20). 13C NMR (100.6 MHz, CDCl3) d 24.7, 24.2, 10.5,
10.9, 14.2, 14.8, 16.6, 18.0, 19.7, 20.4, 25.8, 26.7, 26.8,
27.6, 27.6, 28.1, 28.6, 29.8, 30.2, 30.2, 30.4, 31.7, 31.8,
34.7, 34.8, 34.9, 36.1, 39.7, 40.0, 51.0, 71.3, 71.4, 73.7,
74.5, 74.5, 74.8, 74.8, 95.7, 95.7, 205.1. [a]2D6¼223.58 (c
0.18, CHCl3). IR (KBr): 3462, 2956, 2932, 2860, 1726,

9614
M. Kurono, M. Isobe / Tetrahedron 59 (2003) 9609–9617
1459, 1383, 1255, 1099, 1006, 988, 837, 775 cm21. Anal.
calcd for C31H60O5Si: C, 68.74; H, 11.43. Found: C, 68.84;
H, 11.18.
CH3), 1.05 (3H, d, J¼7.0 Hz, 19-CH3), 1.09 (3H, d,
J¼7.0 Hz, 3-CH3), 1.20–2.14 (26H, m, 3, 4a, 4b, 5a, 5b,
7, 8a, 8b, 9a, 9b, 11a, 11b, 12a, 12b, 13, 15, 16a, 16b, 17a,
17b, 19, SCH2CH2CH2S£2, OH), 2.73–3.02 (8H, m,
SCH2CH2CH2S£2), 3.21 (1H, td, J¼9.5, 2.5 Hz, H-6),
3.38 (1H, dd, J¼10.0, 2.5 Hz, H-14), 3.56 (1H, m, H-18),
4.53 (1H, d, J¼5.0 Hz, H-20). 13C NMR (100.6 MHz,
CDCl3) d 10.9, 13.6, 14.2, 16.6, 18.0, 23.5, 25.6, 26.3, 26.4,
26.8, 27.4, 27.5, 28.3, 30.3, 30.8, 31.1, 31.4, 31.9, 34.7,
35.0, 36.1, 41.9, 44.0, 52.3, 54.9, 73.6, 74.4, 74.6, 95.6.
[a]2D6¼256.98 (c 0.33, CHCl3). IR (KBr): 3483, 2951, 2860,
2364, 1718, 1457, 1381, 1230, 1096, 986, 876 cm21. Anal.
calcd for C31H56O3S4: C, 61.41; H, 9.57. Found: C, 61.54;
H, 9.33.
5.1.7. C1–C20 segment (9). To a solution of 8 (530 mg,
0.98 mmol) in CH2Cl2 (10 ml) was added PCC (634 mg,
˚
2.94 mmol) and a powdered molecular sieves 4 A (795 mg)
at room temperature. After being stirred for 2 h, the reaction
mixture was diluted with ether, filtered through a pad of
Celite and then concentrated under reduced pressure to
afford 9. Purification by column chromatography (silica gel
50 g, ether/hexane¼1/5) gave the pure 9 (896 mg, 83%) as a
colorless oil. 9: 1H NMR (400 MHz, CDCl3) d 0.06 (3H, s,
CH3Si), 0.07 (3H, s, CH3Si), 0.80 (3H, d, J¼7.0 Hz,
7-CH3), 0.88 (3H, d, J¼7.0 Hz, 13-CH3), 0.88 (9H, s,
SiC(CH3)3), 0.99 (3H, d, J¼6.5 Hz, 15-CH3), 1.09 (3H, d,
J¼7.0 Hz, 3-CH3), 1.09 (3H, d, J¼7.0 Hz, 19-CH3), 1.20–
1.74 (17H, m, 4a, 4b, 5a, 5b, 7, 8a, 8b, 9a, 9b, 11a, 11b, 12a,
15, 16a, 16b, 17a, 17b), 1.82 (1H, m, H-13), 2.02 (1H, m,
H-12b), 2.14 (3H, s, H-1), 2.50 (1H, qdd, J¼7.0, 5.0, 2.0 Hz,
H-19), 2.53 (1H, qd, J¼13.5, 7.0 Hz, H-3), 3.16 (1H, td,
J¼10.0, 2.0 Hz, H-6), 3.25 (1H, dd, J¼10.0, 2.5 Hz, H-14),
3.90 (1H, q, J¼5.0 Hz, H-18), 9.74 (1H, d, J¼2.0 Hz,
H-20). 13C NMR (100.6 MHz, CDCl3) d 24.7, 24.2, 10.1,
10.5, 10.9, 16.1, 16.7, 18.0, 25.7, 26.7, 27.6, 28.0, 28.1,
29.1, 30.2, 30.6, 31.6, 34.8, 34.8, 36.1, 47.3, 51.0, 73.6,
74.3, 74.9, 95.6, 204.9, 212.7. [a]2D7¼25.68 (c 0.15, CHCl3).
IR (KBr): 2931, 2859, 1717, 1458, 1378, 1255, 987, 837,
775 cm21. Anal. calcd for C31H58O5Si: C, 68.95; H, 11.04.
Found: C, 69.09; H, 10.85.
5.1.9. Protected C1–C20 segment (10). To a solution of 11
(150 mg, 0.25 mmol) in CH2Cl2 (5 ml) was added 2,6-
lutidine (0.14 ml, 1.24 mmol) and TBSOTf (0.14 ml,
0.62 mmol) at 2208C under N2 atmosphere. After being
stirred for 10 min, the reaction mixture was allowed to
warm to room temperature and stirred for 30 min. The
mixture was poured into sat. NH4Cl aq. and extracted with
CH2Cl2 (£3), washed with water (£3) and brine. The
combined organic phase was dried and then concentrated
under reduced pressure to afford the crude oil (240 mg).
Purification by column chromatography (silica gel 20 g,
ether/hexane¼1/10) gave the pure 10 (176 mg, 99%) as a
colorless oil.
5.1.10. Alcohol (13). To a solution of 10 (264 mg,
0.37 mmol), which was dried in advance with toluene-
azeotrope, and HMPA (0.19 ml 1.10 mmol) in dry THF
(0.7 ml) was added dropwise t-BuLi (1.45 M solution in
hexane, 0.31 ml, 0.44 mmol) at 2508C under Ar
atmosphere, then allowed to warm to 2438C. After stirring
for 90 min, the reaction mixture was allowed to cool at
2788C. A solution of epoxide 12 (25.7 mg, 0.092 mmol) in
THF (0.4 ml) was added to the reaction mixture at 2788C,
and allowed to warm to 2508C. After stirring for 1 h, the
reaction mixture was poured into sat. NH4Cl aq. and
extracted with Et2O (£3). The combined organic phase was
washed with water (£3) and brine, dried over Na2SO4, and
then concentrated in vacuum. The residue was purified by
column chromatography (silica gel 25 g, ether/hexane¼1/4)
to afford the coupling product 13 (73.0 mg, 87%) and
recovered dithiane 10 (82 mg, 43%). 13: 1H NMR
(400 MHz, CDCl3) d 0.09 (6H, s, CH3Si), 0.81 (3H, d,
J¼7.0 Hz, 7-CH3), 0.84 (9H, s, SiC(CH3)3), 0.86 (3H, d,
J¼7.0 Hz, 13-CH3), 0.98 (3H, d, J¼7.0 Hz, H-26), 0.99
(3H, d, J¼7.0 Hz, 25-CH3), 1.02 (3H, d, J¼7.0 Hz, 15-
CH3), 1.09 (3H, d, J¼7.0 Hz, 3-CH3), 1.09 (3H, d,
J¼7.0 Hz, 19-CH3), 1.20–2.12 (25H, m, H-3, 4a, 4b, 5a,
5b, 7, 8a, 8b, 9a, 9b, 11a, 11b, 12a, 12b, 13, 15, 16a, 16b,
17a, 17b, 25, SCH2CH2CH2S£2), 1.58 (3H, s, H-1), 2.20
(1H, qd, J¼7.0, 2.0 Hz, H-19), 2.25 (1H, dd, J¼15.5,
2.0 Hz, H-21a), 2.64 (1H, dd, J¼15.5, 8.0 Hz, H-21b),
2.60–2.90 (6H, m, SCH2CH2CH2S), 2.97 (1H, ddd, J¼11.5,
14.5, 3.0 Hz, one of SCH2CH2CH2S), 3.10 (1H, dd, J¼6.0,
1.5 Hz, H-23) 3.14 (1H, ddd, J¼11.5, 14.5, 3.0 Hz, one of
SCH2CH2CH2S), 3.25 (1H, td, J¼9.5, 2.5 Hz, H-6), 3.36
(1H, dd, J¼10.0, 2.5 Hz, H-14), 3.51 (3H, s, OCH3), 3.54
(1H, dd, J¼6.0, 5.0 Hz, H-24), 3.79 (3H, s, Ar–OCH3), 3.99
(1H, br d, J¼2.5 Hz, OH), 4.19 (1H, m, H-22), 4.25 (1H, m,
5.1.8. Protected C1–C20 segment (10). To a solution of 9
(220 mg, 0.41 mmol) and 1,3-propanedithiol (0.49 ml,
4.9 mmol) in CH2Cl2 (0.2 ml) was added boron trifluoride
etherate (15.5 ml, 0.122 mmol) in CH2Cl2 (10 ml) at 08C
under N2 atmosphere. After being stirred for 1 h, the cooling
bath was removed and stirring was continued for 24 h. The
reaction mixture was poured into sat. NaHCO3 and
extracted with Et2O (£3). The combined organic phase
was washed with water (£3) and brine, dried over Na2SO4
and then concentrated in vacuum. The residue was purified
by column chromatography (silica gel, ether/hexane¼1/6)
to afford protected 10 (173 mg, 59%) and 11 (94.4 mg,
38%). 10: 1H NMR (400 MHz, CDCl3) d 0.07 (3H, s,
CH3Si), 0.11 (3H, s, CH3Si), 0.82 (3H, d, J¼7.0 Hz,
7-CH3), 0.87 (3H, d, J¼7.0 Hz, 13-CH3), 0.90 (9H, s,
SiC(CH3)3), 1.00 (3H, d, J¼7.0 Hz, 19-CH3), 1.01 (3H, d,
J¼7.0 Hz, 15-CH3), 1.10 (3H, d, J¼7.0 Hz, 3-CH3), 1.20–
2.15 (25H, m, H-3, 4a, 4b, 5a, 5b, 7, 8a, 8b, 9a, 9b, 11a, 11b,
12a, 12b, 13, 15, 16a, 16b, 17a, 17b, 19, SCH2CH2CH2-
S£2), 1.60 (3H, s, H-1), 2.74–2.96 (8H, m, SCH2CH2CH2-
S£2), 3.22 (1H, td, J¼9.5, 2.5 Hz, H-6), 3.36 (1H, dd,
J¼10.0, 2.5 Hz, H-14), 3.84 (1H, m, H-18), 4.31 (1H, d,
J¼5.0 Hz, H-20). 13C NMR (100.6 MHz, CDCl3) d 24.7,
24.1, 10.9, 12.1, 14.3, 16.9, 18.0, 18.1, 23.5, 25.4, 25.6,
25.9, 26.3, 26.4, 26.7, 27.5, 27.7, 28.3, 29.4, 30.3, 30.4,
31.3, 32.0, 34.8, 35.0, 36.1, 42.0, 43.3, 51.9, 54.8, 72.2,
74.5, 74.7, 95.6. [a]2D7¼235.78 (c 0.22, CHCl3). IR (KBr):
2954, 2857, 2363, 1459, 1382, 1255, 1091, 986, 939, 836,
775 cm21. Anal. calcd for C37H70O3S4Si: C, 61.66; H,
1
10.08. Found: C, 61.78; H, 9.81. 11: H NMR1H NMR
(400 MHz, CDCl3) d 0.82 (3H, d, J¼7.0 Hz, 7-CH3), 0.87
(3H, d, J¼7.0 Hz, 13-CH3), 1.02 (3H, d, J¼7.0 Hz, 15-

M. Kurono, M. Isobe / Tetrahedron 59 (2003) 9609–9617
9615
H-18), 4.51 (1H, d, J¼11.0 Hz, one of CH2Ar), 4.72 (1H, d,
J¼11.0 Hz, one of CH2Ar), 6.83 (1H, dd, J¼9.5, 2.5 Hz,
one of ArH), 6.84 (1H, dd, J¼9.5, 2.5 Hz, one of ArH), 7.25
(1H, dd, J¼9.5, 2.5 Hz, one of ArH), 7.26 (1H, dd, J¼9.5,
2.5 Hz, one of ArH). 13C NMR (100.6 MHz, CDCl3) d
24.5, 23.8, 8.2, 10.8, 14.2, 16.8, 17.6, 17.9, 18.0, 20.4,
23.6, 25.1, 25.6, 25.8, 26.1, 26.2, 26.5, 26.7, 27.4, 27.5,
28.2, 29.3, 29.5, 30.3, 31.3, 31.7, 34.8, 35.2, 36.1, 40.4,
41.4, 46.9, 54.8, 55.2, 55.8, 59.5, 67.9, 73.4, 74.3, 74.5,
75.3, 82.9, 84.3, 95.6, 113.6, 129.3, 130.7, 159.0.
[a]2D6¼238.18 (c 0.24, CHCl3). IR (KBr): 3464, 2958,
2928, 2856, 1615, 1515, 1463, 1383, 1251, 1174, 1099, 941,
834, 775 cm21. Anal. calcd for C53H94O7S4Si: C, 63.68; H,
9.48. Found: C, 63.70; H, 9.35.
55.6, 58.2, 68.6, 73.8, 74.4, 75.3, 75.5, 81.6, 95.7.
[a]2D6¼235.88 (c 0.13, CHCl3). IR (KBr): 3448, 2929,
2360, 2343, 1718, 1462, 1256, 1099, 834, 774 cm21. ESI
Q-TOF MS calcd for C45H86NaO6S4Siþ [MþNa]þ
901.4974, found 901.4932.
5.1.12. Ester (16). To a solution of Segment A 15 (7.9 mg,
0.025 mmol) and Et3N (7.0 ml, 0.05 mmol) in toluene (1 ml)
was added 2,4,6-trichlorobenzoyl chloride (7.0 ml,
0.045 mmol) at room temperature. After stirring for 5 h, a
solution of 14 (16.8 mg, 0.019 mmol) in toluene (1 ml) and
DMAP (4.2 mg, 0.034 mmol) in toluene (0.5 ml) were
added to reaction mixture at room temperature. After being
stirred for 30 min at room temperature, the mixture was
diluted with water, adjusted to pH 3 by 1N HCl and then
extracted with Et2O (£3). The combined organic phase was
washed with water (£3) and brine, dried over Na2SO4 and
then concentrated in vacuum. The residue was purified by
column chromatography (silica gel, ether/hexane¼1/3) to
provide 16 (18.9 mg, 84%). 16: 1H NMR (400 MHz,
CDCl3) d 0.02 (3H, s, SiCH3), 0.06 (3H, s, SiCH3), 0.07
(3H, s, SiCH3), 0.12 (3H, s, SiCH3), 0.82 (3H, d, J¼7.0 Hz,
7-CH3), 0.85 (3H, d, J¼6.5 Hz, 13-CH3), 0.85 (9H, s,
SiC(CH3)3), 0.87 (9H, s, SiC(CH3)3), 0.92 (3H, d,
J¼7.0 Hz, 26-CH3), 0.93 (3H, d, J¼7.0 Hz, 25-CH3), 1.03
(3H, d, J¼6.5 Hz, 15-CH3), 1.04 (3H, d, J¼7.0 Hz, 19-
CH3), 1.10 (3H, d, J¼7.0 Hz, 3-CH3), 1.09–2.22 (26H, m,
H-3, 4a, 4b, 5a, 5b, 7, 8a, 8b, 9a, 9b, 11a, 11b, 12a, 12b, 13,
15, 16a, 16b, 17a, 17b, 19, 25, SCH2CH2CH2S£2), 1.59
(3H, s, H-1), 2.22 (3H, s, 50-CH3), 2.60–3.13 (12H, m,
H-20a, H-20b, H-21a, H-21a, SCH2CH2CH2S£2), 3.20 (1H,
dd, J¼7.0, 3.0 Hz, H-23), 3.26 (1H, td, J¼9.0, 3.0 Hz, H-6),
3.37 (1H, dd, J¼10.0, 2.0 Hz, H-14), 3.44 (4H, s, OCH3,
OH), 4.04 (1H, m, H-22), 4.22 (1H, m, H-18), 5.09 (1H, d0d,
J¼7.0, 5.0 Hz, H-24), 5.16 (1H, dd, J¼7.0, 6.0 Hz, H-3 ).
13C NMR (100.6 MHz, CDCl3) d 25.2, 24.9, 24.3, 23.8,
7.7, 10.1, 10.9, 14.2, 15.3, 16.8, 16.9, 18.0, 18.0, 19.7, 23.7,
25.1, 25.6, 25.9, 26.0, 26.3, 26.6, 26.8, 27.5, 27.6, 28.4,
28.4, 29.5, 30.4, 31.4, 31.8, 34.8, 35.3, 36.2, 39.2, 41.2,
41.5, 46.7, 54.9, 55.7, 59.4, 65.8, 63.0, 67.6, 73.8, 74.4,
75.3, 76.0, 82.0, 95.6, 142.4, 143.5, 164.1, 165.9, 169.3.
[a]2D8¼215.48 (c 0.18, CHCl3). IR (KBr): 3438, 1771, 1736,
1464, 1378, 1255, 1100, 912, 836, 778 cm21. ESI Q-TOF
MS calcd for C59H106NaO11S4Siþ2 [MþNa]þ 1197.6054,
found 1197.6084.
5.1.11. Diol (14). To a solution of 13 (37 mg, 0.037 mmol)
in Ac2O (0.5 ml) and pyridine (1.0 ml) was added DMAP
(1.0 mg, 8.19 mmol) at room temperature. After being
stirred overnight, the reaction mixture was poured into H2O
and extracted with CH2Cl2 (x 3). The combined organic
phase was washed with aqueous CuSO4·5H2O (£3), water
(£3) and brine, dried over Na2SO4, and concentrated to give
the crude acetylated compound.
To a solution of the crude acetylated compound in CH2Cl2
(2.0 ml) and H2O (0.2 ml) was added DDQ (13.6 mg
0.06 mmol) in toluene (0.1 ml) and CH2Cl2 (0.2 ml) at
room temperature. After stirring for 1 h, the reaction
mixture was poured into sat. NaHCO3 aq. and then extracted
with CH2Cl2 (£3). The combined organic phase was washed
with water (£3) and brine, dried over Na2SO4 and then
concentrated in vacuum to give a crude deprotected
compound.
To a solution of the crude deprotected compound in MeOH
(1.5 ml) was added CaCO3 (30 mg, 0.217 mmol) at room
temperature. After stirring for 7 h, the reaction mixture was
poured into sat. NH4Cl aq. and then extracted with AcOEt
(£3). The combined organic phase was washed with water
(£3) and brine, dried over Na2SO4, and then concentrated in
vacuum. The residue was purified by column chromato-
graphy (silica gel 1.5 g, ether/hexane¼1/3) to afford 14
1
(24.7 mg, 76%). 14: H NMR (400 MHz, CDCl3) d 0.07
(3H, s, CH3Si), 0.10 (3H, s, CH3Si), 0.82 (3H, d, J¼7.0 Hz,
7-CH3), 0.88 (3H, d, J¼7.0 Hz, 13-CH3), 0.89 (9H, s,
SiC(CH3)3), 0.97 (3H, d, J¼7.0 Hz, H-26), 1.01 (3H, d,
J¼7.0 Hz, 25-CH3), 1.03 (3H, d, J¼7.0 Hz, 15-CH3), 1.07
(3H, d, J¼7.0 Hz, 19-CH3), 1.10 (3H, d, J¼7.0 Hz, 3-CH3),
1.20–2.15 (25H, m, H-3, 4a, 4b, 5a, 5b, 7, 8a, 8b, 9a, 9b,
11a, 11b, 12a, 12b, 13, 15, 16a, 16b, 17a, 17b, 25,
SCH2CH2CH2S£2), 1.59 (3H, s, H-1), 2.24 (1H, ddd,
J¼16.0, 9.0, 1.0 Hz, H-21a), 2.25 (1H, qd, J¼7.0, 4.5 Hz,
H-19), 2.66–2.92 (6H, m, SCH2CH2CH2S), 2.78 (1H, dd,
J¼16.0, 9.0 Hz, H-21b), 3.03 (1H, ddd, J¼11.0, 14.5,
3.0 Hz, one of SCH2CH2CH2S), 3.16 (1H, dd, J¼7.0,
3.0 Hz, H-23), 3.17 (1H, ddd, J¼12.0, 14.5, 3.0 Hz, one of
SCH2CH2CH2S), 3.26 (1H, td, J¼9.5, 2.5 Hz, H-6), 3.38
(1H, dd, J¼10.0, 2.5 Hz, H-14), 3.42 (1H, br s, OH), 3.45
(3H, s, OCH3), 3.63 (1H, m, H-24), 4.24 (2H, m, H-22, OH),
4.32 (1H, m, H-18). 13C NMR (100.6 MHz, CDCl3) d 24.3,
23.8, 7.9, 10.8, 14.2, 16.9, 17.0, 18.0, 19.6, 23.6, 25.0, 25.6,
25.9, 26.3, 26.3, 26.7, 26.8, 27.5, 27.6, 28.3, 29.4, 29.7,
30.4, 31.5, 31.8, 34.8, 35.2, 36.1, 38.5, 41.4, 46.8, 54.9,
5.1.13. Tautomycin (1). To a solution of 16 (17.9 mg,
0.015 mmol) in THF (1 ml), which was transferred into a
teflon vial was added pyridinium poly(hydrogen fluoride)
(12 drops) at room temperature. After being stirred for 12 h,
the reaction mixture was neutralized by sat. NaHCO3 aq. to
pH 3 and then extracted with ether (£3). The combined
organic phase was washed with water (£3) and brine, dried
and then concentrated in vacuum.
To a solution of the residue in acetonitrile (0.8 ml) and
water (0.08 ml) was added mercury (II) perchlorate
trihydrate (20.4 mg, 0.045 mmol) and calcium carbonate
(7.5 mg, 0.075 mmol) at room temperature. After being
stirred for 3 min, the mixture was diluted with ether, filtered
through SuperCelw, and then concentrated to give a crude
oil. The residue was purified by column chromatography
(silica gel 0.8 g, ethyl acetate/hexane¼1/2) to afford

9616
M. Kurono, M. Isobe / Tetrahedron 59 (2003) 9609–9617
synthetic tautomycin 1 (8.0 mg, 69%). 1: 1H NMR (CDCl3,
600 MHz) d 0.80 (3H, d, J¼6.5 Hz, 7-CH3), 0.89 (3H, d,
J¼7.0 Hz, 13-CH3), 0.97 (3H, d, J¼7.0 Hz, 25-CH3), 0.98
(3H, d, J¼7.0 Hz, 25-CH3), 1.00 (3H, d, J¼6.5 Hz, 15-
CH3), 1.10 (3H, d, J¼7.0 Hz, 3-CH3), 1.11 (3H, d,
J¼7.5 Hz, 19-CH3), 1.20–1.70 (17H, m, H-4a, 4b, 5a, 5b,
7, 8a, 8b, 9a, 9b, 11a, 11b, 12a, 15, 16a, 16b, 17a, 17b), 1.83
(1H, m, H-13), 2.01 (1H, m, H-12b), 2.11 (1H, m, H-25),
2.15 (3H, s, H-1), 2.27 (3H, d, J¼1.5 Hz, 50-CH3), 2.53 (1H,
sext, J¼7.0 Hz, H-3), 2.67 (1H, m, H-19), 2.67 (1H, dd,
J¼17.5, 4.0 Hz, H-21b), 2.78 (1H, dd, J¼16.5, 10.0 Hz,
H-20a), 2.92 (1H, dd, J¼16.5, 3.0 Hz, H-20b), 2.99 (1H, dd,
J¼17.5, 8.5 Hz, H-21b), 3.16 (1H, td, J¼10.0, 2.5 Hz, H-6),
3.28 (1H, dd, J¼6.0, 2.0 Hz, H-23), 3.28 (1H, dd, J¼10.0,
2.0 Hz, H-14), 3.44 (3H, s, OCH3), 3.70 (1H, td, J¼8.0,
3.0 Hz, H-18), 4.35 (1H, ddd, J¼8.0, 4.0, 2.0 Hz, H-22),
5.10 (1H, t, J¼6.0 Hz, H-24), 5.21 (1H, m, H-30). 13C NMR
(CDCl3, 150.9 MHz) d 10.1, 11.0, 13.7, 16.2, 16.7, 17.9,
18.0, 19.4, 26.8, 27.4, 27.7, 28.1, 28.1, 28.7, 29.1, 30.2,
30.7, 31.5, 34.8, 34.8, 36.1, 41.0, 45.8, 47.3, 52.4, 59.1,
63.9, 66.4, 74.3, 74.3, 74.8, 76.5, 80.6, 95.7, 142.1, 142.9,
164.8, 165.8, 169.6, 213.1, 215.3. [a]2D7¼4.48 (c 0.32,
CHCl3). Lit. [a]2D5¼3.48 (c 1, CHCl3). IR (KBr): 3447, 2928,
2360, 1769, 1716, 1457, 1379, 1260, 1098, 908, 803, 733,
628 cm21. ESI Q-TOF MS calcd for C41H66NaOþ13
[MþNa]þ 789.4401, found 789.4387.
244–246. (c) Ubukata, M.; Cheng, X.-C.; Isobe, M.; Isono, K.
J. Chem. Soc. Perkin Trans. 1 1993, 617–624.
5. For Oikawa and Ichihara’s total synthesis, see: (a) Oikawa,
M.; Oikawa, H.; Ueno, T.; Ichihara, A. Tetrahedron Lett.
1993, 30, 4797–4800. (b) Oikawa, H.; Oikawa, M.; Ueno, T.;
Ichihara, A. Tetrahedron Lett. 1994, 35, 4809–4812.
(c) Oikawa, M.; Ueno, T.; Oikawa, H.; Ichihara, A. J. Org.
Chem. 1995, 60, 5048–5068. (d) Ueno, T.; Oikawa, M.;
Oikawa, H.; Ichihara, A. Biosci. Biotech. Biochem. 1995, 59,
2104–2110. For their group’s structure–activity investi-
gations, see: (e) Kawamura, T.; Matsuzawa, S.; Mizuno, Y.;
Kikuchi, K.; Oikawa, H.; Oikawa, M.; Ubukata, M.; Ichihara,
A. Biochem. Pharmacol. 1998, 55, 995–1003. (f) Oikawa, H.
Curr. Med. Chem. 2002, 9, 2033–2054.
6. For Isobe’s total synthesis, see: (a) Ichikawa, Y.; Naganawa,
A.; Isobe, M. Synlett 1993, 737–738. (b) Ichikawa, Y.; Tsuboi,
K.; Naganawa, A.; Isobe, M. Synlett 1993, 907–908.
(c) Naganawa, A.; Ichikawa, Y.; Isobe, M. Tetrahedron
1994, 50, 8969–8982. (d) Jiang, Y. M.; Ichikawa, Y.; Isobe,
M. Synlett 1995, 3, 285–288. (e) Ichikawa, Y.; Tsouboi, K.;
Jiang, Y.; Naganawa, A.; Isobe, M. Tetrahedron Lett. 1995,
36, 7101–7104. (f) Jiang, Y.; Isobe, M. Tetrahedron 1996, 52,
2877–2892. (g) Tsuboi, K.; Ichikawa, Y.; Naganawa, A.;
Isobe, M.; Ubukata, M.; Isono, K. Tetrahedron 1997, 53,
5083–5102. (h) Jiang, Y.; Ichikawa, Y.; Isobe, M.
Tetrahedron 1997, 53, 5103–5122. (i) Tsouboi, K.; Ichikawa,
Y.; Jiang, Y.; Naganawa, A.; Isobe, M. Tetrahedron 1997, 53,
5123–5142. For his group’s structure–activity investigations,
see: (j) Sugiyama, Y.; Ohtani, I. I.; Isobe, M.; Takai, A.;
Ubukata, M.; Isono, K. Bioorg. Med. Chem. Lett. 1996, 6, 3–8.
(k) Takai, A.; Tsuboi, K.; Koyasu, M.; Isobe, M. Biochem. J.
2000, 350, 81–88.
Acknowledgements
This work was supported by a grant-in-aid from the Ministry
of Education, Science and Technology. We are grateful to
ex-Professor K. Isono at Tokai University for supplying a
crude tautomycin. We also thank Mr S. Kitamura (analytical
laboratory in this school) for elemental analyses, Mr K. Koga
for special NMR spectroscopy and Dr K. Tsuboi for the
record of some unpublished information.
7. For Shibasaki’s total synthesis, see: (a) Nakamura, S.-i.;
Shibasaki, M. Tetrahedron Lett. 1994, 35, 4145–4148.
(b) Shimizu, S.; Nakamura, S.; Nakada, S.; Shibasaki, M.
Tetrahedron 1996, 52, 13363–13408.
8. For Chamberlin’s total synthesis, see: (a) Sheppeck, J. E., II;
Liu, W.; Chamberlin, A. R. J. Org. Chem. 1997, 62, 387–398.
For his group’s structure–activity investigations, see: (b) Liu,
W.; Sheppeck, J. E., II; Colby, D. A.; Huang, H.-B.; Nairn,
A. C.; Chamberlin, A. R. Bioorg. Med. Chem. Lett. 2003, 13,
1597–1600. (c) Colby, D. A.; Liu, W.; Sheppeck, J. E., II;
Huang, H.-B.; Nairn, A. C.; Chamberlin, A. R. Bioorg. Med.
Chem. Lett. 2003, 13, 1601–1605.
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