Total synthesis of (-)-tetrodotoxin from D-glucose: A new route to multi-functionalized cyclitol employing the ferrier(II) reaction toward (-)-tetrodotoxin

Article abstract of DOI:10.1246/bcsj.20090194

Total synthesis of (-)-tetrodotoxin (TTX) from D-glucose is described. As a critical transformation step for synthesizing TTX, a key multi-functionalized cyclitol was prepared from D-glucose employing the Ferrier(II) reaction. Stereospecific introduction of three functionalized branched chains were achieved via Peterson olefination and spiro α-chloroepoxidation of the corresponding carbonyl derivatives.

Full text of DOI:10.1246/bcsj.20090194

© 2010 The Chemical Society of Japan
Bull. Chem. Soc. Jpn. Vol. 83, No. 3, 279–287 (2010)
279
Total Synthesis of (¹)-Tetrodotoxin from D-Glucose:
A New Route to Multi-Functionalized Cyclitol Employing
the Ferrier(II) Reaction toward (¹)-Tetrodotoxin
Shoji Akai,1 Hidehito Seki,1 Naoki Sugita,1 Tomokazu Kogure,1 Naoki Nishizawa,1 Katsuhiko Suzuki,1
Yutaka Nakamura,1 Yasuhiro Kajihara,1 Juji Yoshimura,2 and Ken-ichi Sato*1
1Material and Life Chemistry, Faculty of Engineering, Kanagawa University,
Rokkakubashi, Kanagawa-ku, Yokohama 221-8686
2Department of Basic Science, College of Science and Engineering, Iwaki Meisei University, Iwaki 970-8551
Received July 28, 2009; E-mail: satouk01@kanagawa-u.ac.jp
Total synthesis of (¹)-tetrodotoxin (TTX) from D-glucose is described. As a critical transformation step for
synthesizing TTX, a key multi-functionalized cyclitol was prepared from D-glucose employing the Ferrier(II) reaction.
Stereospecific introduction of three functionalized branched chains were achieved via Peterson olefination and spiro
¡-chloroepoxidation of the corresponding carbonyl derivatives.
The structure of tetrodotoxin (TTX), a toxic principle in
puffer fish poisoning, was reported in 1964 by four separate
research groups: Tsuda’s,1a Hirata’s,1b Woodward’s,1c and
Mosher’s1d groups. TTX is a useful biological tool in neuro-
physiology due to its specificity for blocking voltage-gated
Na+ ion channels in nervous systems.2 Recently, TTX and
several analogs have been found and isolated (Figure 1), not
only from aquatic organisms such as puffer fish, but also
from terrestrial animals.3,4 TTX and its analogs can provide
important insights into pharmaceutical studies, elucidation of
structure-activity relationships, and biological roles.5 Accord-
ingly, the ability to synthesize larger amounts of TTX and its
analogs has grown in importance, however still remains as an
extremely difficult, yet fascinating, challenge.6 In 2003, the
Isobe and Du Bois groups both succeeded in the synthesis of
(¹)-TTX.7a,7d,7e In the following year, Isobe’s group reported
an improved route with fewer steps.7b,7c,7f We also achieved the
total synthesis of («)-TTX from myo-inositol in 2005,8a and
(¹)-TTX from D-glucose employing the Henry reaction (intra-
molecular nitro aldol reaction) in 2008.8b Moreover, recently
Noheda filed a patent application for a synthetic method for
TTX, analogs, and its intermediates.9
In this area, a practical synthetic route for TTX and its
analogs to satisfy biological and pharmacological needs has
been increasingly in demand. Particularly, development of a
convergent synthetic method to prepare the multi-functional-
ized cyclitol of the TTX skeleton rather than a linear protocol is
required. Herein, we describe our success in another convergent
new route for synthesizing (¹)-TTX from D-glucose via the
multi-functionalized cyclitol 10a employing the Ferrier(II)
reaction10 as the key skeleton construction. Our synthetic plan
was based on our prior experiences in the total synthesis of
(«)-TTX from myo-inositol8a (Scheme 1). Both total syntheses
were successfully carried out using the common intermediate
D, with the later work accomplished in an enantiospecific
manner. Compound D was derived from D-glucose in the
following manner. Compound D can be synthesized from
multi-functionalized cyclitol F,8 which can be prepared by the
reaction of enol acetate G employing the Ferrier(II) reaction.10
Compound G can be obtained by standard transformations
of D-glucose by using stereoselective introduction of the
branched chain at the C-3 of D-glucose (at the C-6 of TTX).
The transformation of D into (¹)-TTX, via compound C, B,
and A, were accomplished in a similar manner as reported in
the previous paper.8
Results and Discussion
The total synthesis of (¹)-TTX from D-glucose is shown in
Scheme 2. Methyl 2-O-benzyl-4,6-O-benzylidene-¡-D-gluco-
pyranosid-3-ulose (1) was prepared by regioselective benzyla-
tion11 followed by the Swern oxidation of methyl 4,6-O-
Figure 1.18 Tetrodotoxin and its analogs.1,3
Published on the web February 26, 2010; doi:10.1246/bcsj.20090194

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Bull. Chem. Soc. Jpn. Vol. 83, No. 3 (2010)
Total Synthesis of Tetrodotoxin from D-Glc
Scheme 1.18 Retrosynthetic analysis of (¹)-TTX from D-glucose.
benzylidene-¡-D-glucopyranoside12 derived from D-glucose.
Peterson’s olefination13 of 1 followed by treatment with
aqueous acetic acid solution gave the methylene derivative 3
via trimethylsilyl derivative 2. Regioselective protections of 3
with pivaloyl and methoxymethyl groups gave 5, which was
oxidized using m-chloroperbenzoic acid via the same stereo-
chemical course as reported14 to afford epoxide 6. Alkaline
hydrolysis of 6 yielded triol 7, which was then converted into
the acetonide 8. Oxidation of 8 resulted in an unstable aldehyde,
which was immediately converted into enol acetate 9 (G) as a
single geometrical isomer. The (Z)-configuration at C-8a of 9
was determined by NOESY spectrum (Figure 2). This selec-
tivity was likely due to steric hindrance of the C-5 substituent.
The crucial key reaction of the intramolecular cyclization
(Ferrier(II) reaction)10 of enol acetate 9 was carried out as
follows. Enol acetate 9 was treated with several mercury
reagents in aqueous acetic acid-acetone solution at room
temperature. The results are shown in Table 1. As a result, the
desired stereoisomer 10a (F) was obtained in 58% yield using
Hg(OAc)2 (10a:10b:10c:10d = 6:2:1:0) under the conditions
values of 10a are shown in Figure 2: H-8a, 5.21, J8a,8 = 3.3 Hz;
H-8, 4.21, J8,7 = 2.2 Hz, J8,OH = 1.5 Hz; H-7, 4.02, J7,5 = 0 Hz;
H-5, 4.31, J8a,5 = 1.0 Hz). Furthermore, the configurations at
C-6 and C-8a in TTX numbering of 10a were verified by X-ray
crystal structure analysis of 11 (Figure 3). In spite of many
efforts toward transforming 10b-10d into 10a or others,
it could not be achieved. It seems that some side reactions,
especially ¢-elimination, occurred during the stereochemical
inversion of hydroxy substituents at C-8 and -8a. Protected diol
11 was obtained by catalytic debenzylation of 10a, followed by
isopropylidenation. Compound 11 was then transformed into
12 (E) by Peterson olefination13 and subsequent O-silylation.
Methylene derivative 12 was converted into the corresponding
hydroxymethyl derivative 13 in a hydroboration-oxidation and
de-O-silylation sequence. Selective protection of the primary
hydroxy group of 13 using a tert-butyldiphenylsilyl group
afforded the corresponding monohydroxy compound 14,
which was then oxidized with Dess-Martin periodinane15 to
give optically active ketone 15 (D), a key intermediate in
the synthesis of TTX. The further transformation of 15 into
(¹)-TTX was performed along to our established route8
including the successive spiro ¡-chloroepoxide formation and
ring-opening with an azide anion16 as a crucial key step. Full
synthetic details including the stereochemistry and the final
transformation of 15 into (¹)-TTX are available in Supporting
Information and previous papers.8 The spectral data (1H and
MS) for the synthetic TTX was in good agreement with that of
natural TTX.7a,7b,8
listed in Entry 4. On the other hand, the Ferrier(II) reaction
10c
using PdCl2
afforded a complex mixture. It seems that
(³-allyl)palladium complex as a reaction intermediate was
not smoothly generated therefore the starting enol acetate
gradually decomposed during heating. Finally, we decided that
Hg(OAc)2 was the most suitable reagent for this enol acetate
9. The structures of the four stereoisomers 10a-10d were
confirmed by 1H NMR analysis. The chemical shifts and J

S. Akai et al.
Bull. Chem. Soc. Jpn. Vol. 83, No. 3 (2010)
281
Scheme 2.18 Total synthesis of (¹)-TTX from D-glucose. Reagents and conditions: a) TMSCH2MgCl, Et2O-CH2Cl2 (94%);
b) 60% AcOH aq (99%); c) PivCl, Py., CH2Cl2 (94%); d) P2O5, CH2(OCH3)2, CH2Cl2, (82%); e) m-CPBA, (CH2Cl)2 (75%);
f) n-Bu4NOH, THF (83%); g) (CH3)2C(OCH3)2, p-TsOH, CH2Cl2 (75%); h) TFAA, DMSO, Et3N, CH2Cl2; i) K2CO3, Ac2O,
CH3CN (72%, 2 steps); j) Hg(OAc)2, AcOH aq-acetone, then NaCl aq (58%); k) 20% Pd(OH)2-C, H2, EtOH (quant.);
l) (CH3)2C(OCH3)2, p-TsOH, acetone-CH2Cl2 (66%); m) [i] TMSCH2MgCl, Et2O (56%); [ii] TBS-Cl, imidazole, CH2Cl2 (88%); n)
[i] BH3¢THF, THF, then 10% NaOH aq, 30% H2O2 aq; [ii] n-Bu4NF, THF (74%, 2 steps); o) tert-butyldiphenylsilyl chloride
(TBDPS-Cl), imidazole, CH2Cl2 (92%); p) Dess-Martin periodinane, CH2Cl2 (99%).
total synthesis of TTX in three routes.8 The proper selection
of these synthetic methodologies may useful for not only
Conclusion
The total synthesis of (¹)-TTX from D-glucose featuring the
Ferrier(II) reaction as the key skeleton construction was
successfully carried out using effective and stereoselective
steps. In studies of TTX synthesis, our group has achieved the
compounds related to TTX (including enabled derivatives),
but also other highly complex multi-functionalized cyclitols
bearing branched chain structures such as cyclophellitol,
mytillitol, and laminitol.17

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Bull. Chem. Soc. Jpn. Vol. 83, No. 3 (2010)
Total Synthesis of Tetrodotoxin from D-Glc
NOE
rotations were measured in 0.5 dm tubes using a JASCO P-1020
polarimeter in CHCl3 or 3% CD3COOD/D2O. Mass spectra were
obtained on a SHIMADZU JMS-T100CS. X-ray diffraction was
measurement by Rigaku Saturn 70 diffractometer with graphite
monochromated Mo K¡ radiation. Structure solution and refine-
ment were performed using CrystalStructure 3.8. Crystallographics
data have been deposited with Cambridge Crystallographic Data
Centre: Deposition number CCDC-644815 for compound No. 11.
Copies of the data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge
Crystallographic Data Centre, 12, Union Road, Cambridge, CB2
1EZ, U.K.; Fax: +44 1223 336033; e-mail: deposit@ccdc.cam.
ac.uk).
NOE
OAc
8a
4.75
7.21
H3CO(d)
H (d)
O
8
OAc
O
H
4a
3.47
(s)
5
MOMO
OMe
6
7
O
H
O
O
O
OBn
9 (G)
BnO
O
OMe
2.2 Hz
3.3 Hz
1.0 Hz
OAc
8a
O
Methyl 2-O-Benzyl-4,6-O-benzylidene-¡-D-glucopyranosid-
3-ulose (1). To a stirred solution of trifluoroacetic anhydride
(1.12 mL, 8.07 mmol) in dry CH2Cl2 (10 mL), dimethyl sulfoxide
(0.96 mL, 13.5 mmol) was added at ¹78 °C under argon. After
30 min, a solution of methyl 2-O-benzyl-4,6-O-benzylidene-¡-D-
glucopyranoside10 (1.00 g, 2.69 mmol) in dry CH2Cl2 (5 mL) was
added dropwise to the reaction mixture at ¹78 °C. After 15 min,
triethylamine (2.61 mL, 18.8 mmol) was added dropwise to the
above mixture and stirred for 5 min. After the disappearance of
2-O-benzylglucopyranoside on TLC with toluene-acetone (8:1
v/v), the reaction mixture was poured into saturated aq NaHCO3
solution, extracted with CHCl3, washed with brine and water, dried
over anhyd MgSO4, and evaporated to give 1, which was purified
by recrystallization from hexane-EtOAc; mp 177.0-178.0 °C
(colorless needles, hexane-EtOAc); Rf = 0.38 (toluene-acetone =
H
8a OAc
H
5
O
4a
H
4a
6
5
8
MOMO
OH
MOMO
8
7
O
H
7
6
O
BnO
1.5 Hz
OH
OBn
10a (F)
O
O
Figure 2.18 Structure assignments of enol acetate 9 and
cyclitol 10a (Chemical shifts, split pattern, NOE correla-
tion of 9, and J values of 10a with the corresponding TTX
numbering).
Table 1. The Ferrier(II) Reaction Conditions and Products
Yields
Time
Ratioa)
/h 10a:10b:10c:10d
Isolated yield
of 10a/%
Entry Reagent
25
8:1 v/v); ½¡ꢀD ¹32.4° (c 0.73, CHCl3); IR (KBr, disk): ¯ 1748
¹1
1
cm (C=O); H NMR (600 MHz): ¤ 7.51-7.31 (10H, m, PhH),
5.53 (1H, s, PhCH), 5.06 (1H, d, J2,1 = 4.1 Hz, H-1), 4.97, 4.60
1
2
3
4
Hg(OCOCF3)2 0.3
6:0:1:3
33
trace
48
HgCl2
HgO
4
5
1.5
0:0:1:2
5:0:2:1
6:2:1:0
(2H, each d, JA,B = 12.2 Hz, -CH2Ph), 4.39 (1H, dd, J6eq,6ax
10.2 Hz, J6eq,5 = 4.8 Hz, H-6eq), 4.20 (1H, dd, J4,5 = 9.8 Hz,
4,2 = 1.4 Hz, H-4), 4.14 (1H, dd, J2,1 = 4.1 Hz, J2,4 = 1.4 Hz, H-
=
Hg(OAc)2
58
J
1
a) Determined by H NMR spectrum.
2), 4.09 (1H, ddd, J5,4 = 9.8 Hz, J5,6eq = 4.8 Hz, J5,6ax = 10.4 Hz,
H-5), 3.87 (1H, dd, J6ax,6eq = 10.2 Hz, J6ax,5 = 10.4 Hz, H-6ax),
3.44 (3H, s, OCH3). 13C NMR (150 MHz): ¤ 196.27, 136.9, 136.3,
129.3, 128.6, 128.2, 128.2, 126.4, 102.5, 101.9, 82.1, 79.6, 72.6,
69.4, 65.4. Anal. Calcd for C21H22O6 (370.40): C, 68.10; H,
5.99%. Found: C, 68.43; H, 6.33%.
Methyl
2-O-Benzyl-4,6-O-benzylidene-3-C-trimethylsilyl-
To a solution of 3-ulose 1
methyl-¡-D-allopyranoside (2).
(781 mg, 2.1 mmol) in a mixture of dry CH2Cl2-Et2O (1:1 v/v,
70 mL), trimethylsilylmethylmagnesium chloride (0.45 M in Et2O,
7.0 mL, 3.15 mmol) was added and stirred for 1 h under argon.
After the disappearance of starting compound 1 on TLC with
hexane-EtOAc (2:1 v/v), the mixture was poured into saturated aq
NH4Cl solution, extracted with EtOAc, washed with brine and
water, dried over anhyd MgSO4, evaporated to give 2 (913 mg,
94% yield), which was purified on a column of silica gel with
hexane-EtOAc (4:1 v/v). colorless syrup; Rf = 0.25 (hexane-
Figure 3.18 ORTEP drawing of 11 with the corresponding
TTX numbering. Thermal ellipsoids were scaled to enclose
30% probability.
25
EtOAc = 4:1 v/v); ½¡ꢀD +32.9° (c 1.07, CHCl3); IR (KBr, neat):
¹1
¯ 3511 cm (OH); 1H NMR (600 MHz): ¤ 7.52-7.31 (10H, m,
PhH), 5.48 (1H, s, PhCH), 4.73 (1H, d, J1,2 = 3.4 Hz, H-1), 4.68
(2H, s, CH2-Ph), 4.32 (1H, dd, J6eq,6ax = 10.3 Hz, J6eq,5 = 5.2 Hz,
H-6eq), 4.10 (1H, ddd, J5,6eq = 5.2 Hz, J5,6ax = 10.3 Hz, J5,4 = 9.2
Hz, H-5), 3.69 (1H, dd, J6ax,5 = 10.3 Hz, J6ax,6eq = 10.3 Hz, H-
Experimental
Melting points were measured using a Yanaco Model MP-J3
micro-melting point apparatus, and are uncorrected. IR spectra
were recorded using a SHIMADZU IR Prestige-21 spectrometer in
KBr. H and 13C NMR spectra were measured with JEOL JNM-
ECA500 and -600 spectrometers in CDCl3 or 3% CD3COOD/D2O
solution with tetramethylsilane used as internal standard. Specific
6ax), 3.49 (1H, s, OH), 3.39 (3H, s, OCH3), 3.38 (1H, d, J2,1
=
3.4 Hz, H-2), 3.36 (1H, d, J4,5 = 9.2 Hz, H-4), 1.36, 1.26 (2H, each
d, JA,B = 14.9 Hz, CH2Si(CH3)3), 0.00 (9H, s, CH2Si(CH3)3).
13C NMR (150 MHz): ¤ 137.7, 137.3, 129.0, 128.5, 128.1, 128.0,
126.5, 102.2, 98.5, 82.6, 78.9, 74.9, 72.3, 69.1, 59.4, 55.7, 24.4,
1

S. Akai et al.
Bull. Chem. Soc. Jpn. Vol. 83, No. 3 (2010)
283
0.39. NOE correlation: H-5-OH; H-3¤-H-2, -H-4. Anal. Calcd for
C25H34O6Si (458.62): C, 65.47; H, 7.47%. Found: C, 65.22; H,
7.28%.
d, JA,B = 12.4 Hz, CH2Ph), 4.74, 4.66 (2H, each d, JA,B = 6.9 Hz,
OCH2OCH3), 4.71 (1H, d, J1,2 = 3.8 Hz, H-1), 4.40 (1H, dd,
J
6a,5 = 2.1 Hz, J6a,6b = 11.9 Hz, H-6a), 4.18 (1H, dd, J6b,5 = 5.7
Methyl
pyranoside (3).
2-O-Benzyl-3-deoxy-3-methylene-¡-D-ribo-hexo-
Compound 2 (98.4 mg, 0.214 mmol) was
Hz, J6b,6a = 11.9 Hz, H-6b), 3.98 (1H, br d, J4,5 = 9.8 Hz, H-4),
3.91 (1H, m, H-2), 3.75 (1H, ddd, J5,4 = 9.8 Hz, J5,6a = 2.1 Hz,
dissolved in 60% aq acetic acid solution (3 mL), and stirred for 4 h
at 70 °C. After the disappearance of starting compound 2 on TLC
with hexane-EtOAc (4:1 v/v), the reaction mixture was evapo-
rated to give olefin 3 (59.4 mg, 99% yield), which was purified on
a column of silica gel with hexane-EtOAc (1:4 v/v). Colorless
J5,6b = 5.7 Hz, H-5), 3.42, 3.39 (6H, each s, 2 © OCH3), 1.21 (9H,
s, C(CH3)3). 13C NMR (150 MHz): ¤ 178.2, 140.7, 137.9, 128.5,
127.9, 127.7, 106.4, 98.2, 76.9, 73.4, 72.1, 71.2, 63.3, 56.5, 55.1,
38.9, 27.2. Anal. Calcd for C22H32O7 (408.49): C, 64.69; H,
7.90%. Found: C, 64.74; H, 8.16%.
25
syrup; Rf = 0.55 (hexane-EtOAc = 1:4 v/v); ½¡ꢀD +21.1° (c
Methyl 2-O-Benzyl-4-O-methoxymethyl-6-O-pivaloyl-¡-D-
¹1
¹1
1.45, CHCl3); IR (KBr neat): ¯ 3445 cm (OH), 1661 cm
glucopyranoside-3-spiro-2¤-oxirane (6).
To a solution of 5
(C=C); 1H NMR (600 MHz): ¤ 7.38-7.29 (5H, m, PhH), 5.41-
5.31 (2H, m, H-3¤), 4.80, 4.59 (2H, each d, JA,B = 12.5 Hz,
(53 mg, 0.13 mmol) in dry (CH2Cl)2 (1 mL), m-chloroperbenzoic
acid (44.9 mg, 0.26 mmol) was added and stirred at 55 °C under
argon for 3 h. After the disappearance of starting compound 5 on
TLC with hexane-MeOH (5:1 v/v), the reaction mixture was
poured into saturated aq NaHCO3 solution, extracted with CHCl3,
washed with brine and water, dried over anhyd MgSO4, evaporated
to give epoxide 6 (41 mg, 75% yield), which was purified on a
column of silica gel with hexane-EtOAc (4:1 v/v). Colorless
CH2Ph), 4.71 (1H, d, J1,2 = 3.6 Hz, H-1), 4.07 (1H, dd, J6a,5
7.4 Hz, J6a,6b = 9.3 Hz, H-6a), 3.93 (1H, m, H-2), 3.85 (2H, m,
H-6b, H-4), 3.50 (1H, ddd, J5,6a = 7.4 Hz, J5,6b = 4.0 Hz, J5,4
=
=
8.9 Hz, H-5), 3.40 (3H, s, OCH3), 2.28 (1H, d, JOH,4 = 7.2 Hz,
4-OH), 2.05 (1H, s, 6-OH). 13C NMR (150 MHz): ¤ 143.5, 137.9,
128.5, 128.1, 127.9, 127.7, 105.3, 98.7, 97.7, 76.5, 73.7, 72.1,
68.6, 62.6, 55.3. Anal. Calcd for C15H20O5 (280.32): C, 64.27; H,
7.19%. Found: C, 64.15; H, 7.16%.
26
syrup; Rf = 0.48 (hexane-EtOAc = 2:1 v/v); ½¡ꢀD +91.5° (c
¹1
1.26, CHCl3); IR (KBr, neat): ¯ 1732 cm (C=O); 1H NMR
Methyl 2-O-Benzyl-3-deoxy-3-methylene-6-O-pivaloyl-¡-D-
ribo-hexopyranoside (4). To a solution of olefin 3 (104 mg,
0.37 mmol) in dry CH2Cl2 (2.5 mL) and pyridine (0.5 mL),
pivaloyl chloride (92 ¯L, 0.74 mmol) was added and stirred at
0 °C. After 80 min, pivaloyl chloride (46 ¯L, 0.37 mmol) was
added to the above mixture at rt. After the disappearance of starting
compound 3 on TLC with hexane-EtOAc (1:1 v/v), EtOH (5 mL)
was added to the above reaction mixture and stirred for 10 min.
The above mixture was poured into water, extracted with CHCl3,
washed with brine and water, dried over anhyd MgSO4, evaporated
to give 4 (126 mg, 94% yield), which was purified on a column
of silica gel with hexane-EtOAc (3:1 v/v). Mp 65.2-67.3 °C
(600 MHz): ¤ 7.37-7.28 (5H, m, PhH), 4.78, 4.52 (2H, each d,
J
A,B = 12.2 Hz, CH2Ph), 4.72, 4.51 (2H, each d, JA,B = 6.7 Hz,
OCH2OCH3), 4.69 (1H, d, J1,2 = 3.6 Hz, H-1), 4.41 (1H, dd,
6a,5 = 2.1 Hz, J6a,6b = 11.9 Hz, H-6a), 4.17 (1H, dd, J6b,6a = 11.9
Hz, J6b,5 = 5.7 Hz, H-6b), 3.88 (1H, ddd, J5,4 = 10.1 Hz, J5,6a
J
=
2.1 Hz, J5,6b = 5.7 Hz, H-5), 3.79 (1H, d, J4,5 = 10.1 Hz, H-4), 3.70
(1H, m, H-2), 3.39, 3.36 (6H, each s, 2 © OCH3), 3.13, 3.06 (2H,
each d, Ja,b = 5.8 Hz, H-3¤), 1.21 (9H, s, C(CH3)3). 13C NMR
(150 MHz): ¤ 178.2, 137.8, 129.8, 128.4, 127.9, 98.9, 97.6, 73.9,
73.5, 70.4, 69.3, 63.1, 60.6, 56.4, 55.2, 45.4, 38.9, 27.2. Anal.
Calcd for C22H32O8 (424.48): C, 62.25; H, 7.60%. Found: C,
62.23; H, 7.57%.
26
(hexane-EtOAc); Rf = 0.21 (hexane-EtOAc = 3:1 v/v); ½¡ꢀD
Methyl 2-O-Benzyl-3-C-hydroxymethyl-4-O-methoxymeth-
¹1
+27.0° (c 3.00, CHCl3); IR (KBr, disk): ¯ 3474 cm (OH),
yl-¡-D-glucopyranoside (7).
To a solution of epoxide 6
¹1
1721 cm (C=O); 1H NMR (600 MHz): ¤ 7.38-7.30 (5H, m,
(41 mg, 97.0 ¯mol) in dry THF (1 mL), tetra-n-butylammonium
hydroxide (40 wt % in aqueous solution, 315 ¯L, 0.485 mmol) was
added and refluxed for 30 h. After the disappearance of starting
compound 6 on TLC with hexane-EtOAc (1:4 v/v), the reaction
mixture was poured into saturated aq NH4Cl solution, extracted
with CHCl3, washed with brine and water, dried over anhyd
MgSO4, evaporated to give diol 7 (29 mg, 83% yield), which was
purified on a column of silica gel with hexane-EtOAc (1:4 v/v).
PhH), 5.42-5.37 (2H, m, H-3¤), 4.79, 4.59 (2H, each d, JA,B
12.5 Hz, CH2Ph), 4.72 (1H, d, J1,2 = 3.8 Hz, H-1), 4.50 (1H, dd,
6a,5 = 5.0 Hz, J6a,6b = 12.2 Hz, H-6a), 4.27 (1H, dd, J6b,5 = 2.2
Hz, J6b,6a = 12.2 Hz, H-6b), 3.91 (1H, m, H-2), 3.81 (1H, br dd,
=
J
J
J
4,OH = 6.4 Hz, J4,5 = 9.3 Hz, H-4), 3.63 (1H, ddd, J5,4 = 9.3 Hz,
5,6a = 5.0 Hz, J5,6b = 2.2 Hz, H-5), 3.40 (3H, s, OCH3), 2.71
(1H, d, JOH,4 = 6.4 Hz, OH), 1.22 (9H, s, C(CH3)3). 13C NMR
(150 MHz): ¤ 179.4, 142.6, 137.8, 130.1, 128.6, 128.5, 128.4,
128.2, 127.9, 127.7, 105.9, 98.5, 76.6, 72.7, 72.5, 72.2, 68.2, 63.8,
63.7, 55.2, 38.9, 27.2. Anal. Calcd for C20H28O6 (364.43): C,
65.91; H, 7.74%. Found: C, 65.83; H, 7.88%.
26
Colorless syrup; Rf = 0.31 (hexane-EtOAc = 1:4 v/v); ½¡ꢀD
¹1
+75.7° (c 0.75, CHCl3); IR (KBr, neat): ¯ 3474 cm (OH);
1H NMR (600 MHz): ¤ 7.36-7.30 (5H, m, PhH), 4.90, 4.69 (2H,
each d, JA,B = 6.4 Hz, OCH2OCH3), 4.78, 4.68 (2H, each d, JA,B
11.9 Hz, CH2Ph), 4.62 (1H, d, J1,2 = 4.1 Hz, H-1), 4.18 (1H, dd,
6a,OH = 6.7 Hz, J6a,6b = 11.9 Hz, H-6a), 3.95 (1H, dd, J6b,6a
11.9 Hz, J6b,OH = 7.2 Hz, H-6b), 3.91 (1H, d, JOH,3¤ = 2.1 Hz, OH),
3.80, 3.77 (2H, each ddd, J3¤,OH = 2.1 Hz, J3¤,OH = 6.5 Hz, Ja,b
12.2 Hz, H-3¤), 3.67 (1H, d, J4,5 = 10.4 Hz, H-4), 3.66 (1H, d,
5,4 = 10.4 Hz, H-5), 3.59 (1H, d, J2,1 = 4.1 Hz, H-2), 3.45, 3.36
=
Methyl 2-O-Benzyl-3-O-deoxy-4-O-methoxymethyl-3-meth-
ylene-6-O-pivaloyl-¡-D-ribo-hexopyranoside (5). To a solution
of compound 4 (267.4 mg, 0.74 mmol) in dry CH2Cl2 (4 mL),
dimethoxymethane (3.27 mL, 37 mmol), Molecular Sieves 4A
(945 mg), and P2O5 (650 mg, 4.52 mmol) were added and stirred at
rt for 5 h. After the disappearance of starting compound 4 on TLC
with hexane-EtOAc (1:1 v/v), the reaction mixture was poured
into saturated NaHCO3 solution, extracted with CHCl3, washed
with brine and water, dried over anhyd MgSO4, evaporated to give
5 (245.3 mg, 82% yield), which was purified on a column of silica
gel with hexane-EtOAc (4:1 v/v). Colorless syrup; Rf = 0.47
J
=
=
J
(6H, each s, OCH3), 2.95 (1H, dd, JOH,6a = 7.2 Hz, JOH,6b = 7.2
Hz, CH2OH), 2.45 (1H, dd, JOH,3¤a = 6.7 Hz, JOH,3¤b = 6.7 Hz,
OH). 13C NMR (150 MHz): ¤ 137.6, 128.5, 128.1, 128.0, 99.2,
98.3, 81.5, 79.4, 75.2, 74.1, 69.1, 62.9, 61.7, 56.5, 55.5. Anal.
Calcd for C17H26O8 (358.38): C, 56.97; H, 7.31%. Found: C,
56.76; H, 7.37%.
25
(hexane-EtOAc = 2:1 v/v); ½¡ꢀD +123.0° (c 1.80, CHCl3); IR
¹1
(KBr, neat): ¯ 1732 cm (C=O); 1H NMR (600 MHz): ¤ 7.38-
Methyl 2-O-Benzyl-3-C-hydroxymethyl-4-O-methoxymeth-
yl-¡-D-glucopyranoside-3-spiro-4¤-(2¤,2¤-dimethyldioxolane) (8).
7.30 (5H, m, PhH), 5.39-5.27 (2H, m, H-3¤), 4.79, 4.57 (2H, each

284
Bull. Chem. Soc. Jpn. Vol. 83, No. 3 (2010)
Total Synthesis of Tetrodotoxin from D-Glc
To a solution of diol 7 (2.52 g, 7.07 mmol) in CH2Cl2 (75 mL),
acetone dimethylacetal (4.3 mL, 35.4 mmol) and p-toluenesulfonic
acid monohydrate (54 mg, 0.28 mmol) were added and stirred for
20 min. After the disappearance of starting compound 7 on TLC
with hexane-EtOAc (1:4 v/v), triethylamine (1 mL) was added to
the reaction mixture and stirred 5 min. The above mixture was
poured into saturated aq NaHCO3 solution, extracted with CHCl3,
washed with brine and water, dried over anhyd MgSO4, and
evaporated to give acetonide 8 (2.10 g, 75% yield), which was
purified on a column of silica gel with hexane-EtOAc (1:1 v/v).
D-gluco-hexodialdopyranoside-3-spiro-4¤-(2¤,2¤-dimethyldioxo-
lane)): Colorless syrup; Rf = 0.25 (toluene-acetone = 8:1 v/v);
1H NMR (270 MHz): ¤ 9.63 (1H, d, JCHO,5 = 2.3 Hz), 8.28-7.23
(5H, m, PhH), 4.89, 4.67 (2H, each d, JA,B = 12.2 Hz, CH2Ph),
4.85, 4.56 (2H, each d, JA,B = 6.6 Hz, OCH2OCH3), 4.46 (1H,
J
1,2 = 3.3 Hz, H-1), 4.33, 4.09 (2H, each d, Ja,b = 9.5 Hz, H-3¤),
3.87 (1H, dd, J5,CHO = 2.3 Hz, J5,4 = 10.2 Hz, H-5), 3.65 (1H,
d, J4,5 = 10.2 Hz, H-4), 3.53 (1H, d, J2,1 = 3.3 Hz, H-2), 3.30,
3.29 (6H, each s, 2 © OCH3), 1.47, 1.44 (6H, each s, C(CH3)2).
13C NMR (150 MHz): ¤ 197.0, 137.7, 128.6, 128.2, 128.2, 109.6,
99.7, 99.0, 85.4, 78.0, 77.7, 74.6, 74.6, 74.2, 64.5, 56.3, 55.9, 26.8,
25.8. ESI-TOF-MS Calcd for C20H29O8 m/z [M + H]+: 397.1862.
Found: 397.1865.
2D-(2,3,4,6/5(OH))-2-O-Acetyl-4-O-benzyl-5-C-hydroxymeth-
yl-5,5¤-O-isopropylidene-6-O-methoxymethyl-2,3,4,5,6-penta-
hydroxycyclohexanone (10a), 2D-(2,4,6/3,5(OH))-2-O-Acetyl-
4-O-benzyl-5-C-hydroxymethyl-5,5¤-O-isopropylidene-6-O-me-
thoxymethyl-2,3,4,5,6-pentahydroxycyclohexanone (10b), 2L-
(3,4,6/2,5(OH))-2-O-Acetyl-4-O-benzyl-5-C-hydroxymethyl-5,5¤-
O-isopropylidene-6-O-methoxymethyl-2,3,4,5,6-pentahydroxy-
cyclohexanone (10c), and 2L-(4,6/2,3,5(OH))-2-O-Acetyl-4-O-
benzyl-5-C-hydroxymethyl-5,5¤-O-isopropylidene-6-O-methoxy-
26
Colorless syrup; Rf = 0.25 (hexane-EtOAc = 1:1 v/v); ½¡ꢀD
¹1
+94.7° (c 0.82, CHCl3); IR (KBr, neat): ¯ 3480 cm (OH);
1H NMR (500 MHz): ¤ 7.37-7.28 (5H, m, PhH), 4.90, 4.71 (2H,
each d, JA,B = 6.5 Hz, OCH2OCH3), 4.83, 4.56 (2H, each d,
J
A,B = 12.4 Hz, CH2Ph), 4.41 (1H, d, J1,2 = 3.4 Hz, H-1), 4.35,
4.01 (2H, each d, Ja,b = 9.3 Hz, H-3¤), 3.92 (1H, br ddd, J6a,5
2.2 Hz, J6a,OH = 5.2 Hz, J6,6¤ = 12.7 Hz, H-6a), 3.70 (1H, br ddd,
6b,6a = 12.7 Hz, J6b,5 = 2.2 Hz, J6b,OH = 8.9 Hz, H-6b), 3.57 (1H,
d, J4,5 = 10.1 Hz, H-4), 3.53 (1H, d, J2,1 = 3.4 Hz, H-2), 3.45 (3H,
s, OCH3), 3.43 (1H, ddd, J5,4 = 10.1 Hz, J5,6a = 2.2 Hz, J5,6b
2.2 Hz, H-5), 3.28 (3H, s, OCH3), 3.08 (1H, br dd, JOH,6a = 5.2 Hz,
OH,6b = 8.9 Hz, OH), 1.48, 1.44 (6H, each s, C(CH3)2). 13C NMR
=
J
=
J
(150 MHz): ¤ 137.9, 128.5, 128.5, 128.2, 128.0, 109.2, 100.2,
98.9, 85.8, 78.2, 78.1, 74.4, 70.4, 64.5, 61.5, 56.5, 55.3, 26.9, 25.9.
Anal. Calcd for C20H30O8 (398.45): C, 60.29; H, 7.59%. Found: C,
59.97; H, 7.52%.
methyl-2,3,4,5,6-pentahydroxycyclohexanone (10d).
To a
solution of enol acetate 9 (218 mg, 0.497 mmol) in a mixture of
acetone-H2O-AcOH (500:200:7 v/v/v, 6 mL), mercury(II) acetate
(205 mg, 0.464 mmol) was added and stirred at 70 °C for 1 h. After
the disappearance of starting compound 9 on TLC with hexane-
EtOAc (1:1 v/v), the reaction mixture was cooled to rt, saturated
aq NaCl solution (3 mL) was added to the above mixture, and
stirred for 5 min. After the end of reaction as determined by TLC
with hexane-EtOAc (1:1 v/v), the mixture was extracted with
CHCl3, washed with brine and water, and evaporated to give a
residue. The remaining residue was purified on a column of silica
gel with hexane-EtOAc (4:1 v/v) to give cyclitol 10a (122 mg,
58% yield) and its diastereomers 10b (18 mg, 23% yield) and 10c
(9.2 mg, 9% yield), respectively.
Methyl
6-O-Acetyl-2-O-benzyl-4-O-methoxymethyl-¡-D-
xylo-hex-5-enopyranoside-3-spiro-4¤-(2¤,2¤-dimethyldioxolane)
(9). To a stirred solution of trifluoroacetic anhydride (200 ¯L,
1.36 mmol) in dry CH2Cl2 (30 mL), dimethyl sulfoxide (170 ¯L,
2.4 mmol) was added at ¹78 °C under argon. After 15 min, a
solution of alcohol 8 (94.8 mg, 0.24 mmol) in dry CH2Cl2 (2 mL)
was added dropwise to the reaction mixture at ¹78 °C. After
30 min, triethylamine (400 ¯L, 2.88 mmol) was added dropwise to
the above mixture, and stirred for 5 min. After the disappearance of
starting compound 8 on TLC with toluene-acetone (8:1 v/v), the
reaction mixture was warm to rt, poured into saturated aq NaHCO3
solution, extracted with CHCl3, washed with brine and water, dried
over anhyd MgSO4, and evaporated to give unstable aldehyde.
Following, to a solution of aldehyde in dry CH3CN (5 mL),
potassium carbonate (199 mg, 1.44 mmol) and acetic anhydrous
(227 ¯L, 2.4 mmol) were added and refluxed for 6 h. After the
disappearance of starting aldehyde on TLC with hexane-EtOAc
(1:1 v/v), the reaction mixture was poured into saturated aq NH4Cl
solution, extracted with EtOAc, washed with brine and water,
dried over anhyd MgSO4, and evaporated to give enol acetate 9
(75.2 mg, 2 steps 72% yield), which was purified on a column of
silica gel with hexane-EtOAc (1:1 v/v). Mp 50.0-51.0 °C (color-
less plates, hexane-EtOAc); Rf = 0.47 (hexane-EtOAc = 2:1 v/v);
10a: colorless syrup; Rf = 0.34 (hexane-EtOAc = 1:1 v/v);
25
¹1
½¡ꢀD ¹8.74° (c 2.31, CHCl3); IR (KBr neat): ¯ 3543 cm (OH),
¹1
1
1748, 1732 cm (C=O); H NMR (600 MHz): ¤ 7.41-7.35 (5H,
m, PhH), 5.21 (1H, dd, J2,6 = 1.0 Hz, J2,3 = 3.3 Hz, H-2), 4.92,
4.73 (2H, each d, JA,B = 11.9 Hz, CH2Ph), 4.78, 4.75 (2H, each d,
J
A,B = 6.7 Hz, OCH2OCH3), 4.31 (1H, d, J6,2 = 1.0 Hz, H-6), 4.26,
3.90 (2H, each d, JA,B = 9.5 Hz, H-5¤), 4.21 (1H, ddd, J3,2 = 3.3
Hz, J3,4 = 2.2 Hz, J3,OH = 1.5 Hz, H-3), 4.02 (1H, d, J4,3 = 2.2 Hz,
H-4), 3.43 (3H, s, OCH3), 2.29 (1H, d, JOH,3 = 1.5 Hz, OH), 2.20
(3H, s, COCH3), 1.52, 1.46 (6H, each s, C(CH3)2). 13C NMR (150
MHz): ¤ 197.0, 169.4, 137.1, 128.7, 128.4, 128.1, 110.2, 96.9,
87.2, 81.1, 77.8, 74.7, 74.5, 69.4, 64.6, 56.5, 26.6, 26.0, 20.5.
Anal. Calcd for C21H28O9 (424.44): C, 59.43; H, 6.65%. Found:
C, 59.34; H, 7.05%. ESI-TOF-MS Calcd for C21H28NaO9 m/z
[M + Na]+: 447.1631. Found: 447.1596.
26
¹1
½¡ꢀD ¹10.6° (c 0.97, CHCl3); IR (KBr, disk): ¯ 1755 cm
(C=O), 1639 cm (C=C); 1H NMR (600 MHz): ¤ 7.39-7.31
¹1
(5H, m, PhH), 7.21 (1H, d, J6,4 = 1.9 Hz, H-6), 4.88, 4.61 (2H,
10b: colorless syrup; Rf = 0.48 (hexane-EtOAc = 1:1 v/v);
25
¹1
each d, JA,B = 12.4 Hz, CH2Ph), 4.87, 4.75 (2H, each d, JA,B
=
½¡ꢀD ¹14.4° (c 1.01, CHCl3); IR (KBr neat): ¯ 3468 cm (OH),
¹1 1
6.5 Hz, OCH2OCH3), 4.53 (1H, J1,2 = 3.4 Hz, H-1), 4.21, 3.98
(2H, each d, Ja,b = 9.3 Hz, H-3¤), 4.03 (1H, d, J4,6 = 1.9 Hz, H-4),
3.64 (1H, d, J2,1 = 3.4 Hz, H-2), 3.47, 3.41 (6H, each s, 2 ©
OCH3), 2.14 (3H, s, COCH3), 1.48, 1.44 (6H, each s, C(CH3)2).
13C NMR (150 MHz): ¤ 167.2, 137.8, 135.0, 128.5, 128.2, 128.1,
123.7, 109.9, 100.4, 98.2, 85.4, 77.4, 76.2, 74.7, 64.4, 56.9, 56.4,
26.7, 25.7, 20.5. Anal. Calcd for C22H30O9 (438.47): C, 60.26; H,
6.90%. Found: C, 60.50; H, 6.87%.
1755, 1748 cm (C=O); H NMR (600 MHz): ¤ 7.40-7.33 (5H,
m, PhH), 5.23 (1H, dd, J2,6 = 1.0 Hz, J2,3 = 10.3 Hz, H-2), 5.03,
4.80 (2H, each d, JA,B =11.7 Hz, OCH2OCH3), 4.77 (2H, s,
CH2Ph), 4.47 (1H, d, J6,2 = 1.0 Hz, H-6), 3.98, 3.81 (2H, each d,
J
J
a,b = 8.4 Hz, H-5¤), 3.92 (1H, d, J4,3 = 9.5 Hz, H-4), 3.48 (1H, d,
3,4 = 9.5 Hz, H-3), 3.43 (3H, s, OCH3), 2.50 (1H, br s, OH), 2.18
(3H, s, COCH3), 1.52, 1.48 (6H, each s, C(CH3)2). 13C NMR
(150 MHz): ¤ 197.0, 169.7, 137.6, 128.9, 128.4, 127.9, 111.7, 96.7,
84.6, 81.6, 80.2, 77.3, 76.5, 71.1, 64.3, 56.5, 26.4, 26.3, 20.5. ESI-
Aldehyde (Methyl (5R)-2-O-Benzyl-4-O-methoxymethyl-¡-

S. Akai et al.
Bull. Chem. Soc. Jpn. Vol. 83, No. 3 (2010)
285
25
TOF-MS Calcd for C21H28NaO9 m/z [M + Na]+: 447.16310.
Found: 447.1602.
Rf = 0.27 (toluene-acetone = 1:1 v/v); ½¡ꢀD +19.4° (c 3.40,
¹1 ¹1
CHCl3); IR (KBr, disk): ¯ 3458 cm (OH), 1730, 1714 cm
1
10c: colorless syrup; Rf = 0.23 (hexane-EtOAc = 1:1 v/v);
(C=O); H NMR (600 MHz): ¤ 5.33 (1H, d, J2,3 = 3.4 Hz, H-2),
4.76 (2H, each d, JA,B = 6.7 Hz, OCH2OCH3), 4.46 (1H, br dd,
J3,OH = 2.8 Hz, J3,2 = 2.8 Hz, H-3), 4.41 (1H, s, H-6), 4.30, 3.96
(2H, each d, Ja,b = 9.8 Hz, H-5¤), 4.22 (1H, br s, H-4), 3.32 (3H, s,
OCH3), 2.84 (1H, br d, JOH,4 = 3.4 Hz, OH), 2.64 (1H, br s, OH),
2.23 (3H, s, COCH3), 1.49 (6H, s, C(CH3)2). 13C NMR (150 MHz):
¤ 197.6, 169.7, 110.1, 97.0, 87.5, 80.0, 75.3, 71.8, 71.2, 64.3, 56.8,
26.8, 26.3, 20.7. Anal. Calcd for C14H22O9 (334.32): C, 50.30; H,
6.63%. Found: C, 49.99; H, 6.92%.
1D-(1,2,3,5/4(OH))-1-O-tert-Butyldimethylsilyl-4-C-hydroxy-
methyl-2,3:4,4¤-di-O-isopropylidene-5-O-methoxymethyl-6-C-
methylene-1,2,3,4,5-cyclohexanepentol (12). To a solution of
diacetonide 11 (60 mg, 0.16 mmol) in dry Et2O (10 mL), trimeth-
ylsilylmethylmagnesium chloride (1.0 M in Et2O solution,
2.88 mL, 2.88 mmol) was added dropwise at 0 °C, and stirred for
20 h. After the disappearance of starting compound 11 on TLC
with hexane-EtOAc (1:1 v/v), the reaction mixture was poured
into saturated aq NH4Cl solution, extracted with EtOAc, washed
with brine and water, dried over anhyd MgSO4, and evaporated to
give olefin (30 mg, 56% yield), which was purified on a column of
silica gel with hexane-EtOAc (3:2 v/v). To a solution of resulting
olefin (30 mg, 80 ¯mol) in dry CH2Cl2 (4 mL) tert-butyldimethyl-
silyl chloride (78 mg, 0.51 mmol) and imidazole (52 mg, 0.77
mmol) were added and stirred for 22 h. After the disappearance of
starting olefin on TLC with hexane-EtOAc (2:1 v/v), the reaction
mixture was poured into saturated aq NaHCO3 solution, extracted
with CHCl3, washed with brine and water, and evaporated to give
silyl ether 12 (28.8 mg, 88% yield), which was purified on a column
of silica gel with hexane-EtOAc (4:1 v/v). Colorless syrup; Rf =
25
¹1
½¡ꢀD +8.9° (c 0.1, CHCl3); IR (KBr neat): ¯ 3495 cm (OH),
¹1
1
1744, 1742 cm (C=O); H NMR (600 MHz): ¤ 7.40-7.34 (5H,
m, PhH), 6.00 (1H, d, J2,3 = 3.3 Hz, H-2), 4.83, 4.64 (2H, each d,
JA,B = 11.9 Hz, CH2Ph), 4.69, 4.67 (2H, each d, JA,B = 6.7 Hz,
OCH2OCH3), 4.43 (1H, ddd, J3,4 = 3.6 Hz, J3,OH = 9.6 Hz, J3,2
=
3.3 Hz, H-3), 4.22, 3.99 (2H, each d, Ja,b = 9.6 Hz, H-5¤), 3.98 (1H,
d, J6,4 = 1.7 Hz, H-6), 3.50 (1H, dd, J4,3 = 3.6 Hz, J4,6 = 1.7 Hz,
H-4), 3.39 (3H, s, OCH3), 3.13 (1H, d, JOH,3 = 9.6 Hz, OH), 2.23
(3H, s, COCH3), 1.41, 1.32 (6H, each s, C(CH3)2). 13C NMR
(150 MHz): ¤ 200.2, 170.0, 136.9, 128.6, 128.3, 128.0, 112.5,
96.5, 85.2, 82.6, 79.8, 74.9, 73.4, 73.0, 69.2, 56.5, 26.6, 26.2, 20.7.
ESI-TOF-MS Calcd for C21H28NaO9 m/z [M + Na]+: 447.1631.
Found: 447.1662.
10d: colorless syrup; Rf = 0.6-0.2 tailing (hexane-EtOAc = 1:1
26
¹1
v/v); ½¡ꢀD +10.3° (c 0.1, CHCl3); IR (KBr neat): ¯ 3468 cm
¹1
1
(OH), 1745, 1741 cm (C=O); H NMR (600 MHz): ¤ 7.43-7.27
(5H, m, PhH), 5.37 (1H, dd, J2,3 = 4.1 Hz, J2,4 = 3.3 Hz, H-2),
5.14 (1H, dd, J3,4 = 4.3 Hz, J3,OH = 7.0 Hz, H-3), 4.89, 4.68 (2H,
each d, JA,B = 12.0 Hz, CH2Ph), 4.67, 4.65 (2H, each d, JA,B
6.7 Hz, OCH2OCH3), 4.26, 3.85 (2H, each d, Ja,b = 9.6 Hz, H-5¤),
3.95 (1H, d, J6,4 = 1.2 Hz, H-6), 3.94 (1H, dd, J4,6 = 1.2 Hz, J4,3
=
=
4.3 Hz, H-4), 3.37 (3H, s, OCH3), 3.20 (1H, d, JOH,3 = 7.0 Hz,
OH), 2.00 (3H, s, COCH3), 1.36, 1.13 (6H, each s, C(CH3)2).
13C NMR (150 MHz): ¤ 205.6, 170.5, 137.0, 128.5, 128.4, 128.2,
128.0, 111.5, 97.0, 84.7, 82.5, 74.9, 73.3, 69.6, 69.0, 56.5, 26.7,
26.1, 20.9. ESI-TOF-MS Calcd for C21H28NaO9 m/z [M + Na]+:
447.1631. Found: 447.1643.
2D-(2,3,4,6/5(OH))-2-O-Acetyl-5-C-hydroxymethyl-3,4:5,5¤-di-
O-isopropylidene-6-O-methoxymethyl-2,3,4,5,6-pentahydroxy-
25
0.36 (hexane-EtOAc = 4:1 v/v); ½¡ꢀD ¹48.4° (c 3.38, CHCl3); IR:
cyclohexanone (11).
A solution of cyclitol 10a (146 mg,
Characteristic absorption was not observed; 1H NMR (600 MHz): ¤
5.43, 5.31 (2H, each m, H-6¤), 4.79, 4.75 (2H, each d, JA,B = 6.7
Hz, OCH2OCH3), 4.53 (1H, m, H-1), 4.41 (1H, dd, J2,1 = 4.5 Hz,
0.344 mmol) in EtOH (7 mL) was hydrogenated in the presence of
a catalytic amount of 20% Pd(OH)2-C (116 mg) under H2 gas at rt
for 2 h. After the disappearance of starting compound 10a on TLC
with toluene-acetone (1:1 v/v), catalyst was filtered off, and
evaporated to quantitatively give diol. To a solution of this diol
(10.6 mg, 31.7 ¯mol) in a mixture of acetone-CH2Cl2 (1:1 v/v)
(0.4 mL), 2,2-dimethoxypropane (40 ¯L, 0.317 mmol) and p-
toluenesulfonic acid monohydrate (5.5 mg, 3.17 ¯mol) were added
and stirred at rt for 1 h. After the disappearance of starting diol on
TLC with toluene-acetone (2:1 v/v), the reaction mixture was
quenched with saturated aq NaHCO3 solution, washed with brine
and water, dried over anhyd MgSO4, and evaporated to give
diacetonide 11 (7.8 mg, 66% yield), which was purified on a
column of silica gel with hexane-EtOAc (2:1 v/v). Mp 145.0-
146.0 °C (colorless prism, hexane-EtOAc); Rf = 0.41 (hexane-
J
2,3 = 6.9 Hz, H-2), 4.21 (1H, d, J3,2 = 6.9 Hz, H-3), 4.15 (2H, each
s, H-4¤), 4.14 (1H, br s, H-5), 3.43 (3H, s, OCH3), 1.47, 1.43, 1.40,
1.33 (12H, each s, 2 © C(CH3)2), 0.94 (9H, s, SiC(CH3)3), 0.14,
0.12 (6H, each s, Si(CH3)2). 13C NMR (150 MHz): ¤ 143.1, 112.1,
110.2, 109.8, 96.5, 83.3, 79.2, 77.6, 69.5, 67.7, 56.1, 26.9, 26.3,
26.0, 25.7, 24.8, 18.6, 13.7, ¹4.6, ¹4.9. Anal. Calcd for C22H40-
O7Si (444.63): C, 59.43; H, 9.07%. Found: C, 59.62; H, 8.85%.
Olefin (1D-(1,2,3,5/4(OH))-4-C-Hydroxymethyl-2,3:4,4¤-di-
O-isopropylidene-5-O-methoxymethyl-6-C-methylene-1,2,3,4,5-
cyclohexanepentol):
Mp 55.5-56.5 °C (colorless needles,
25
hexane-EtOAc); Rf = 0.40 (hexane-EtOAc = 1:1 v/v); ½¡ꢀD
¹1
¹104.3° (c 0.45, CHCl3); IR (KBr disk): ¯ 3487 cm (OH),
1659 cm¹1 (C=C); 1H NMR (600 MHz): ¤ 5.37, 5.33 (2H, each m,
H-6¤), 4.79, 4.75 (2H, each d, JA,B = 6.7 Hz, OCH2OCH3), 4.48
25
EtOAc = 1:1 v/v); ½¡ꢀD ¹152.4° (c 1.03, CHCl3); IR (KBr
¹1
disk): ¯ 1759, 1741 cm (C=O); 1H NMR (600 MHz): ¤ 5.70
(1H, dd, J4,5 = 4.8 Hz, J4,3 = 6.7 Hz, H-2), 4.36 (1H, br ddd, J5,4
4.8 Hz, J5,1 = 1.9 Hz, J5,OH = 9.8 Hz, H-5), 4.28 (1H, dd, J3,4
=
=
(1H, d, J2,3 = 4.5 Hz, H-2), 5.03, 4.72 (2H, each d, Ja,b = 6.9 Hz,
OCH2OCH3), 4.84 (1H, dd, J3,2 = 4.5 Hz, J3,4 = 6.8 Hz, H-3),
6.7 Hz, J3,1 = 0.7 Hz, H-3), 4.26, 4.16 (2H, each d, JA,B = 9.5 Hz,
H-4¤), 4.24 (1H, br d, J1,3 = 0.7 Hz, H-1), 3.45 (3H, s, OCH3), 2.43
(1H, d, JOH,5 = 9.8 Hz, OH), 1.44, 1.43, 1.41, 1.35 (12H, each s,
2 © C(CH3)2). 13C NMR (150 MHz): ¤ 143.6, 112.3, 110.5, 110.1,
97.1, 81.8, 79.5, 78.3, 76.1, 68.6, 68.3, 56.4, 27.0, 26.2, 25.6, 25.0.
Anal. Calcd for C16H26O7 (330.37): C, 58.17; H, 7.93%. Found: C,
57.90; H, 8.20%.
1D-(1,2,3,5,6/4(OH))-4,6-Di-C-hydroxymethyl-2,3:4,4¤-di-O-
isopropylidene-5-O-methoxymethyl-1,2,3,4,5-cyclohexanepentol
(13). To a solution of olefin 12 (215 mg, 0.484 mmol) in dry THF
(15 mL), Borane-THF complex (1.0 M in THF solution, 1.45 mL,
4.43 (1H, d, J4,3 = 6.8 Hz, H-4), 4.35, 4.24 (2H, each d, JA,B
=
9.8 Hz, H-5¤), 4.18 (1H, s, H-6), 3.46 (3H, s, OCH3), 2.24 (3H, s,
COCH3), 1.48, 1.45, 1.39, 1.35 (12H, each s, 2 © C(CH3)2).
13C NMR (150 MHz): ¤ 200.6, 170.0, 111.7, 111.5, 97.9, 82.1,
80.2, 77.4, 75.9, 73.8, 69.3, 56.6, 27.1, 25.9, 25.6, 24.4, 20.6.
Anal. Calcd for C17H26O9 (374.38): C, 54.54; H, 7.00%. Found: C,
54.41; H, 7.24%.
Diol
5,5¤-O-isopropylidene-6-O-methoxymethyl-2,3,4,5,6-pentahy-
droxycyclohexanone): Mp 66.5-67.3 °C (hexane-EtOH);
(2D-(2,3,4,6/5(OH))-2-O-Acetyl-5-C-hydroxymethyl-

286
Bull. Chem. Soc. Jpn. Vol. 83, No. 3 (2010)
Total Synthesis of Tetrodotoxin from D-Glc
1.45 mmol) was added at 0 °C, and stirred at rt. After 1 h, 10 wt %
aq NaOH solution (9 mL) was added to the stirred mixture at 0 °C.
After 5 min, 30 wt % aq H2O2 solution (9 mL) was added and
stirred at 0 °C for 1 h. After monitoring of the reaction on TLC
with hexane-EtOAc (2:1 v/v), the reaction mixture was poured
into saturated aq NH4Cl solution, extracted with EtOAc, washed
with sodium thiosulfate solution, brine, and water, dried over
anhyd MgSO4, and evaporated to give residue. To a solution of the
remaining residue in tetrahydrofuran (5 mL), tetra-n-butylammo-
nium fluoride (1.0 M in THF solution, 0.58 mL, 0.58 mmol) was
added and stirred for 1 h at rt. After the disappearance of starting
compound 12 on TLC with EtOAc, the reaction mixture was
evaporated to give a residue. The remaining residue was purified
on a column of silica gel with EtOAc to give diol 13 (126 mg, 74%
TLC with hexane-EtOAc (4:1 v/v), the reaction mixture was
poured into saturated aq NaHCO3 solution, extracted with CHCl3,
washed with brine and water, and evaporated to give ketone 15
(865 mg, 99% yield), which was purified on a column of silica gel
with hexane-EtOAc (4:1 v/v). Colorless syrup; Rf = 0.4 (hexane-
26
EtOAc = 4:1 v/v); ½¡ꢀD +17.0° (c 0.83, CHCl3); IR (KBr, neat):
¹1
1
¯ 1732 cm (C=O); H NMR (600 MHz): ¤ 7.65-7.34 (10H, m,
PhH), 4.62, 4.54 (2H, each d, JA,B = 6.7 Hz, CH2OCH3), 4.44 (1H,
dd, J3,2 = 6.0 Hz, J3,5 = 1.9 Hz, H-3), 4.43, 4.35 (2H, each d,
J
A,B = 9.6 Hz, H-4¤), 4.40 (1H, d, J2,3 = 6.0 Hz, H-2), 4.37 (1H,
dd, J5,6 = 2.1 Hz, J5,3 = 1.9 Hz, H-5), 4.01 (1H, dd, J6¤a,6 = 4.8 Hz,
6¤a,6¤b = 11.0 Hz, H-6¤a), 3.93 (1H, dd, J6¤b,6¤a = 11.0 Hz, J6¤b,6
10.3 Hz, H-6¤b), 3.30 (3H, s, OCH3), 3.28 (1H, ddd, J6,6¤a = 4.8 Hz,
6,6¤b = 10.3 Hz, J6,5 = 2.1 Hz, H-6), 1.51, 1.50, 1.36, 1.34 (12H,
J
=
J
25
yield 2 steps). Colorless syrup; Rf = 0.55 (EtOAc); ½¡ꢀD +6.59°
each s, 2 © C(CH3)2), 1.04 (9H, s, C(CH3)3). 13C NMR (150 MHz):
¤ 206.2, 135.5, 135.5, 134.8, 133.2, 129.8, 129.6, 127.7, 111.0,
110.8, 98.7, 82.8, 82.3, 79.2, 78.6, 69.8, 58.3, 55.7, 51.5,
26.9, 26.8, 26.8, 26.7, 26.5, 26.2, 19.2, 19.1. Anal. Calcd for
C32H44O8Si (584.77): C, 65.73; H, 7.58%. Found. C, 65.79; H,
7.33%.
¹1
(c 1.8, CHCl3); IR (KBr neat): ¯ 3464 cm (OH); 1H NMR
(600 MHz): ¤ 4.77, 4.72 (2H, each d, JA,B = 6.7 Hz, OCH2OCH3),
4.26 (2H, each d, JA,B = 9.6 Hz, H-4¤), 4.15 (1H, d, J2,1 = 4.8 Hz,
H-2), 4.15 (1H, s, H-3), 4.01 (1H, dd, J6¤a,6 = 9.1 Hz, J6¤a,6¤b
11.3 Hz, H-6¤a), 3.93 (1H, d, J5,6 = 2.4 Hz, H-5), 3.85 (1H, dd,
6¤b,6 = 6.2 Hz, J6¤b,6¤a = 11.3 Hz, H-6¤b), 3.83 (1H, br ddd, J1,2
=
J
=
(¹)-Tetrodotoxin. White powder; Rf = 0.5 (1-butanol-AcOH-
H2O = 2:1:1 v/v/v), Rf = 0.6 (pyridine-EtOAc-AcOH-H2O =
4.8 Hz, J1,6 = 2.4 Hz, J1,OH = 10.8 Hz, H-1), 3.46 (3H, s, OCH3),
3.18 (1H, d, JOH,1 = 10.8 Hz, OH), 2.63 (1H, br s, OH), 2.10 (1H,
dddd, J6,6¤a = 9.1 Hz, J6,5 = 2.4 Hz, J6,6¤b = 6.2 Hz, J6,1 = 2.4 Hz,
H-6), 1.58, 1.41, 1.41, 1.40 (12H, each s, 2 © C(CH3)2). 13C NMR
(150 MHz): ¤ 110.8, 109.7, 99.5, 80.6, 79.9, 78.3, 75.5, 69.3, 68.2,
61.3, 56.8, 39.7, 27.0, 26.6, 25.8, 25.7. Anal. Calcd for C16H28O8
(348.39): C, 55.16; H, 8.10%. Found: C, 55.0; H, 8.20%.
28
15:9:3:6 v/v/v/v); ½¡ꢀD ¹3.75° (c 0.13, 3% AcOH); 1H NMR
(600 MHz, in 3% CD3COOD/D2O, referenced to CHD2COOD
(2.06 ppm)): ¤ 5.50 (d, 1H, J = 8.9 Hz, H-4), 4.30 (d, 1H,
J = 2.1 Hz, H-8), 4.25 (br s, 1H, H-5), 4.09 (t, 1H, J = 2.1 Hz,
H-7), 4.06, 4.01 (2 © d, 2H, J = 12.4 Hz, H-11), 3.96 (s, 1H,
H-9), 2.35 (d, 1H, J = 9.6 Hz, H-4a). ESI-TOF-MS Calcd for
C11H18N3O8 m/z [M + H]+: 320.1094. Found: 320.1085.
1D-(1,2,3,5,6/4(OH))-6¤-O-tert-Butyldiphenylsilyl-4,6-di-C-
hydroxymethyl-2,3:4,4¤-di-O-isopropylidene-5-O-methoxymeth-
yl-1,2,3,4,5-cyclohexanepentol (14). To a solution of diol 13
(1.3 g, 3.73 mmol) in dry CH2Cl2 (45 mL) tert-butyldiphenylsilyl
chloride (1.2 mL) and imidazole (1.0 mg, 14.7 mmol) were added
and stirred for 10 min. After the disappearance of starting com-
pound 13 on TLC with EtOAc, the reaction mixture was poured
into saturated aq NaHCO3 solution, extracted with CHCl3, washed
with brine and water, and evaporated to give silyl ether 14 (2.01 g,
92% yield), which was purified on a column of silica gel with
hexane-EtOAc (4:1 v/v). Colorless syrup; Rf = 0.45 (hexane-
The authors thank Professor T. Nakagawa for helpful
discussions. This work was partially supported by “Science
Frontier Project of Kanagawa University” and Grants-in-Aid
for Scientific Research for Young Scientists B (No. 19750147
to A. S.) from the Ministry of Education, Culture, Sports,
Science and Technology, Japan.
Supporting Information
The copies of 1H and 13C NMR (PDF). This material is
available free of charge on the web at http://www.csj.jp/journals/
bcsj/.
26
EtOAc = 3:1 v/v); ½¡ꢀD ¹23.6° (c 2.8, CHCl3); IR (KBr, neat):
¹1
¯ 3508 cm (OH); 1H NMR (600 MHz): ¤ 7.68-7.36 (10H, m,
PhH), 4.71, 4.61 (2H, each d, JA,B = 6.7 Hz, OCH2OCH3), 4.35,
4.30 (2H, each d, Ja,b = 9.6 Hz, H-4¤), 4.14 (1H, d, J3,2 = 5.3 Hz,
H-3), 4.11 (1H, dd, J2,3 = 5.3 Hz, J2,1 = 5.2 Hz, H-2), 4.06 (1H, br
dd, J5,1 = 0.9 Hz, J5,6 = 2.2 Hz, H-5), 4.02 (1H, dd, J6¤a,6 = 9.5 Hz,
References
1
a) K. Tsuda, S. Ikuma, M. Kawamura, K. Tachikawa, K.
J
6¤a,6¤b = 10.3 Hz, H-6¤a), 3.88 (1H, dd, J6¤b,6¤a = 10.3 Hz, J6¤b,6
=
=
Sakai, C. Tamura, O. Amakasu, Chem. Pharm. Bull. 1964, 12,
1357. b) T. Goto, Y. Kishi, S. Takahashi, Y. Hirata, Tetrahedron
1965, 21, 2059. c) R. B. Woodward, Pure Appl. Chem. 1964, 9, 49.
d) H. S. Mosher, F. A. Fuhrman, H. D. Buchwald, H. G. Fischer,
Science 1964, 144, 1100.
6.2 Hz, H-6¤b), 3.76 (1H, dddd, J1,2 = 5.2 Hz, J1,5 = 0.9 Hz, J1,6
2.1 Hz, J1,OH = 11.3 Hz, H-1), 3.31 (3H, s, OCH3), 3.30 (1H, d,
OH,1 = 11.3 Hz, OH), 2.09 (1H, dddd, J6,6¤b = 6.2 Hz, J6,6¤a = 9.5
J
Hz, J6,5 = 2.2 Hz, J6,1 = 2.1 Hz, H-6), 1.56, 1.45, 1.42, 1.40 (12H,
each s, 2 © C(CH3)2), 1.05 (9H, s, C(CH3)3). 13C NMR (150 MHz):
¤ 135.6, 135.5, 133.5, 133.3, 129.7, 129.7, 127.7, 127.7, 110.5,
109.6, 98.9, 80.2, 80.0, 78.2, 75.5, 69.7, 68.1, 62.3, 56.2, 40.3,
26.8, 26.7, 25.8, 25.8, 19.2. NOE correlations: H-2-H-6; H-4¤-
H-3, H-5. Anal. Calcd for C32H46O8Si (586.78): C, 65.50; H,
7.90%. Found: C, 65.17; H, 7.98%.
2
a) T. Narahashi, J. W. Moore, W. R. Scott, J. Gen. Physiol.
1964, 47, 965. b) T. Narahashi, J. Toxicol., Toxin Rev. 2001, 20, 67.
a) Review: M. Yotsu-Yamashita, J. Toxicol., Toxin Rev.
2001, 20, 50. b) See also references cited in 8.
3
4
5
J. W. Daly, J. Nat. Prod. 2004, 67, 1211.
a) M. Yotsu-Yamashita, Y. Yamagishi, T. Yasumoto,
2D-(2,3,5,6/4(OH))-6¤-O-tert-Butyldiphenylsilyl-4,6-di-C-hy-
droxymethyl-2,3:4,4¤-di-O-isopropylidene-5-O-methoxymethyl-
Tetrahedron Lett. 1995, 36, 9329. b) Y. Shimizu, Ann. N.Y. Acad.
Sci. 1986, 479, 24. c) M. Kodama, T. Ogata, S. Sato, Mar. Biol.
1985, 87, 199. d) K. Matsumura, Nature 1995, 378, 563.
2,3,4,5-tetrahydroxycyclohexanone (15).
To a solution of
compound 14 (0.876 g, 1.49 mmol) in dry CH2Cl2 (20 mL), Dess-
Martin periodinane (1.268 g, 2.99 mmol) was added and stirred for
15 min at rt. After the disappearance of starting compound 14 on
6
For leading references from other groups, see: a) M.
Fernández-González, R. Alonso, J. Org. Chem. 2006, 71, 6767.
b) C. S. Burgey, R. Vollerthun, B. Fraser-Reid, J. Org. Chem.

S. Akai et al.
Bull. Chem. Soc. Jpn. Vol. 83, No. 3 (2010)
287
1996, 61, 1609. c) R. J. Nachman, M. Hoenel, T. M. Williams,
R. C. Halaska, H. S. Mosher, J. Org. Chem. 1986, 51, 4802.
d) J. F. W. Keana, P. J. Boyle, M. Erion, R. Hartling, J. R. Husman,
J. E. Richman, R. B. Roman, R. M. Wah, J. Org. Chem. 1983, 48,
3621. e) T. Itoh, M. Watanabe, T. Fukuyama, Synlett 2002, 1323.
f) T. Umezawa, T. Hayashi, H. Sakai, H. Teramoto, T. Yoshikawa,
M. Izumiya, Y. Tamatani, T. Hirose, Y. Ohfune, T. Shinada, Org.
Lett. 2006, 8, 4971.
9883. b) Review: R. J. Ferrier, S. Middleton, Chem. Rev. 1993, 93,
2779. c) Review: H. Takahashi, Yakugaku Zasshi 2002, 122, 755.
11 J. K. Fairweather, M. J. McDonough, R. V. Stick, D. M. G.
Tilbrook, Aust. J. Chem. 2004, 57, 197.
12 Commercially available: TCI Japan (CAS# 3162-96-7).
13 Review: L. F. van Staden, D. Gravestock, D. J. Ager, Chem.
Soc. Rev. 2002, 31, 195.
14 M. Funabashi, H. Sato, J. Yoshimura, Bull. Chem. Soc. Jpn.
1976, 49, 788.
7
a) N. Ohyabu, T. Nishikawa, M. Isobe, J. Am. Chem. Soc.
2003, 125, 8798. b) T. Nishikawa, D. Urabe, M. Isobe, Angew.
Chem., Int. Ed. 2004, 43, 4782. c) D. Urabe, T. Nishikawa, M.
Isobe, Chem. Asian J. 2006, 1, 125. d) A. Hinman, J. Du Bois,
J. Am. Chem. Soc. 2003, 125, 11510. e) U. Koert, Angew. Chem.,
Int. Ed. 2004, 43, 5572. f) M. Isobe, N. Ohyabu, T. Nishikawa,
J. Synth. Org. Chem., Jpn. 2007, 65, 492.
15 D. B. Dess, J. C. Martin, J. Am. Chem. Soc. 1991, 113,
7277.
16 a) K. Sato, K. Suzuki, M. Ueda, M. Katayama, Y. Kajihara,
Chem. Lett. 1991, 1469. b) K. Sato, K. Suzuki, M. Ueda, Y.
Kajihara, H. Hori, Bull. Chem. Soc. Jpn. 1997, 70, 225. c) K. Sato,
T. Sekiguchi, T. Hozumi, T. Yamazaki, S. Akai, Tetrahedron Lett.
2002, 43, 3087.
8
a) K. Sato, S. Akai, N. Sugita, T. Ohsawa, T. Kogure, H.
Shoji, J. Yoshimura, J. Org. Chem. 2005, 70, 7496. b) K. Sato, S.
Akai, H. Shoji, N. Sugita, S. Yoshida, Y. Nagai, K. Suzuki, Y.
Nakamura, Y. Kajihara, M. Funabashi, J. Yoshimura, J. Org.
Chem. 2008, 73, 1234.
17 a) K. Sato, M. Bokura, H. Moriyama, T. Igarashi, Chem.
Lett. 1994, 37. b) K. Sato, M. Bokura, M. Taniguchi, Bull. Chem.
Soc. Jpn. 1994, 67, 1633.
18 The numbering used in all Schemes and Figures of this
paper corresponds to that of tetrodotoxin.
9
P. Noheda, EP 1785427, 2007.
10 a) S. L. Bender, R. J. Budhu, J. Am. Chem. Soc. 1991, 113,