Total synthesis of eurypamides, marine cyclic-isodityrosines from the Palauan sponge Microciona eurypa

Article abstract of DOI:10.1016/j.tet.2004.04.062

Total synthesis of eurypamides A, B, and D, 1, 2, and 4, has been successfully accomplished. The Tl(NO₃)₃ (TTN) oxidation of the halogenated bisphenols, 14a, 14b, 24, and 43, effected regio-controlled cyclization to provide the corre

Full text of DOI:10.1016/j.tet.2004.04.062

Tetrahedron 60 (2004) 5623–5634
Total synthesis of eurypamides, marine cyclic-isodityrosines
from the Palauan sponge Microciona eurypa
*
Miyuki Ito, Maki Yamanaka, Noriki Kutsumura and Shigeru Nishiyama
Department of Chemistry, Faculty of Science and Technology, Keio University, Hiyoshi 3-14-1, Kohoku-ku, Yokohama 223-8522, Japan
Received 24 March 2004; accepted 20 April 2004
Abstract—Total synthesis of eurypamides A, B, and D, 1, 2, and 4, has been successfully accomplished. The Tl(NO3)3 (TTN) oxidation of
the halogenated bisphenols, 14a, 14b, 24, and 43, effected regio-controlled cyclization to provide0t0he corresponding diaryl ethers, 15a, 15b,
25, and 46. This investigation revealed a structural revision of eurypamide A as to possess (200S,3 R,400S)-configuration (47), along with the
spectral data of pure 2 and 4, which were previously characterized in a mixture.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
The isodityrosine-type natural products are known to
exhibit antimicrobial, cytotoxic, and enzyme-inhibitory
activities. In such cyclic members, as K-13, OF 4949, and
vancomycin, the diaryl ether moiety plays an important role
to support the stereochemistry of the peptide chains which
regulate their biological activities. In this context, we have
extensively synthesized these isodityrosine-type natural
products employing phenolic oxidation with TTN, as a
key step,1 which can assemble the cyclic structures by
production of the diaryl ether linkage in the desired manner.
Upon oxidation of A with TTN in MeOH, the corresponding
product B is produced, and the following Zn-reduction
afforded the diaryl ether C (Fig. 1). In particular, the ether
linkage is exclusively constructed at the iodine position.2
We initiated the synthesis of eurypamides, as part of our
extensive investigation. Among eurypamides A–D, 1–4,
isolated from the Palauan sponge, Microciona eurypa,3 1
consists of isodityrosine and the unprecedented
(200S,300S,400R)-dihydroxyarginine unit. The other three
congeners were not isolated, and their structures were
determined by direct spectroscopic measurement of a
mixture. While eurypamide C 3 was synthesized by Itokawa
et al.,4 no synthetic investigation of the others has been
reported. In addition, eurypamides might be expected to
possess biological activities by their structural similarity to
other cyclic isodityrosine-members, although no such
Figure 1.
information has been reported, to our knowledge. We
describe herein the synthesis of eurypamides A, B, and D, 1,
2, and 4.5
2. Results and discussion
In our retrosynthetic analysis, the cyclic structure would be
constructed by ring-closing at the ether linkage by means of
the TTN oxidation of 5 (Scheme 1). The substrate 5 would
Keywords: Eurypamides; Isodityrosine; L-Threonine.
*
Corresponding author. Tel./fax: þ81-45-566-1717;
e-mail address: nisiyama@chem.keio.ac.jp
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.04.062

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M. Ito et al. / Tetrahedron 60 (2004) 5623–5634
proton signal (*) by the anisotropy effect of another
aromatic ring in addition to existence of two Br and one I
groups by the mass spectroscopic evidence. Dehalogenation
of 15a was accomplished by Pd-mediated hydrogenolysis,
followed by alkaline hydrolysis and TFA treatment to give 2
in good yield. After acid hydrolysis of 2, gas-chromato-
graphic analysis of the resultant mixture indicated the
existence of L-threonine: the phenolic oxidation of 14a gave
rise to cyclization without serious racemization and/or
elimination reactions even in the presence of a labile
L-threonine.
In the next stage, synthesis of eurypamide D 4 was
attempted. Tripeptide 14b, a substrate of the TTN oxidation,
was produced essentially as the same procedure as in the
case of 14a, as depicted in Scheme 2. The oxidation of
14b gave the desired cyclic compound 15b in 61% yield,
which was successively submitted to hydrogenolysis
(16b), alkaline hydrolysis, and TFA treatment to provide
eurypamide D 4. Based on these successful results, our
attention turned to synthesis of eurypamide A 1.
Scheme 1. Retrosynthetic analysis of eurypamides A, B, and D, 1, 2, and 4.
be synthesized from L-tyrosine 6 and, L-threonine 7 for 2,
L-allo-threonine 8 for 4, or (3S,4R)-dihydroxyarginine unit
9 for 1, a guanidine group of which would be introduced at
the final step.
2.2. Synthesis of eurypamide A 1
2.1. Synthesis of eurypamide B 2 and D 4
Synthesis of 1 was started from preparation of the (3S,4R)-
dihydroxyarginine derivative. Thus, 177 was produced by
condensation of 2,3-O-isopropylidene-D-glyceraldehyde
with methyl isocyanoacetate. Reduction of 17 with
DIBAL-H and NaBH4, gave diol 18. Selective protec-
tion of the primary hydroxyl group as a pivaloyl ester,
followed by introduction of TBS groups, afforded 19. After
conversion of the Cbz group into the Boc group (20a),
the primary TBS group was selectively removed
(20b), followed by azidation (21a) and removal of the
pivaloyl group to give the primary alcohol 21b, which
on oxidation with TEMPO afforded the amino acid 22
(Scheme 3).
The first synthetic target was the relatively simple
eurypamide B 2 to confirm the feasibility of our phenolic
oxidation approach employing TTN as an oxidant (Scheme
2). Accordingly, connection of the brominated tyrosine
derivative 106 with N-Boc-L-threonine 11a under BOP
conditions, provided the dipeptide 12a. After removal of the
Boc group of 12a, an ammonium salt was further coupled
with the diiodotyrosine derivative 13 to give the tripeptide
14a. TTN oxidation of 14a in THF–MeOH smoothly
proceeded to afford the desired cyclic product 15a in 72%
1
yield. The structure was determined by the mass and H
NMR spectra: the high-field shift (d 5.77) of the aromatic
Scheme 2. Reagents and conditions: (a) BOP, Et3N, DMF: 12a, 90%; 12b, 85%. (b) i. TFA, CH2Cl2; ii. 13, BOP, Et3N, DMF: 14a, 91% in 2 steps; 14b, 91% in
2 steps. (c) TTN, THF–MeOH (4:1): 15a, 72%; 15b, 61%. (d) H2, NaOAc, 10% Pd–C, MeOH: 16a, 100%; 16b, 100%. (e) i. 1 M aq. NaOH, MeOH, quant;
ii. TFA, CH2Cl2: 2, 90% in 2 steps; 4, 92% in 2 steps.

M. Ito et al. / Tetrahedron 60 (2004) 5623–5634
5625
Scheme 3. Reagents and conditions: (a) DIBAL-H, CH2C12. (b) NaBH4, MeOH, 84% from 21. (c) PivCl, pyr, 80%. (d) TBSOTf, 2,6-lutidine, CH2Cl2, 85%.
(e) H2, 10% Pd–C, MeOH; Boc2O, NaHCO3 aq., dioxane, 100%. (f) PPTS, MeOH, 77%. (g) MsCl, pyr; NaN3, DMF, 77%. (h) DIBAL-H, CH2Cl2, 90%.
(i) TEMPO, KBr, NaClO, NaHCO3 aq., acetone, 83%.
Scheme 4. Reagents and conditions: (a) 10, BOP, Et3N, DMF, 85%. (b) TFA, CH2C12. (c) 13, BOP, Et3N, DMF, 65% in 2 steps. (d) TTN, THF–MeOH (4:1),
63%. (e) Ph3P, H2O, THF. (f) HgCl2, Et3N, DMF, 60% in 2 steps. (g) i. H2, NaOAc, 10% Pd–C, MeOH; ii. TBAF, THF, 65% in 2 steps; iii. 1 M aq. NaOH,
MeOH; iv. TFA, CH2Cl2, quant in 2 steps.
Amino acid 22 was connected with 10 to give the dipeptide
23 in 85% yield (Scheme 4). After selective removal of the
Boc group, the second coupling with 13 afforded the desired
tripeptide 24. TTN oxidation of 24 effected the cyclization
to give the cyclic diaryl ether 25 in 63% yield. Upon
monitoring by TLC, there were no remarkable byproducts
except highly polar-products, which might be produced by
polymerization. The azide group of 25 was selectively
reduced, followed by introduction of the guanidine group to
give 27. Removal of the halogen atoms and the TBS groups,
followed by successive hydrolysis00 for the ester and the
N-protecting group, gave (300S,4 R)-eurypamide A 1.
enabled determination of the stereochemistry, with the
exception of those at the C-3 and 4 positions.3 The acetonide
derivative of 1 was used to determine the stereochemistry of
the C-3 and 4 positions; both H-3 and H-4 showed NOE
correlations to the same acetonide-methyl group. This
observa0t0ion00revealed that00the C-3 and 4 positions should
have (3 S,4 R)- or (300R,4 S)-configuration. Although they
adopted a more energetically preferred (300S,400R)-configu-
ration in the molecular modeling calculation, we expected 1
might possess a more labile (300R,400S)-stereochemistry.
Based on this working-hypothesis, the corresponding
arginine derivative carrying (300R,400S)-configuration was
synthesized from D-ribose.
1
Comparison of the H NMR data of the synthetic sample
with those reported (Table 1), indicated a clear difference in
the region of the methine protones of the dihydroxyarginine
moiety while the respective 13C NMR spectra and optical
rotations were similar ([a]2D0 217.8 (c 0.23, MeOH), lit.3
[a]D 221.5 (c 0.23, MeOH)).
2.3. Synthesis of (300R,400S)-eurypamide A 47
Introduction of an azide group at the free hydroxyl group
position of 288 under the Mitsunobu conditions provided 29
(Scheme 5). Reduction of the azide and successive Boc
protection afforded 30. Debenzylation (31) and selective
Faulkner described that the rigid system of eurypamide A 1

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M. Ito et al. / Tetrahedron 60 (2004) 5623–5634
Table 1. Comparison of the 1H NMR data (CD3OD) of the synthetic 1 with
the reported data (Ref. 3)
Scheme 6. Reagents and conditions: (a) 10, BOP, Et3N, DMF, 81%. (b) i.
TBAF, THF; ii. TFA, CH2C12, 13, EDC, HOBt, Et3N, DMF, 85% in 3
steps. (c) 2,2-dimethoxypropane, cat. TsOH, DMF, 47%. (d) i. TBSOTf,
2,6-lutidine, CH2Cl2; ii. K2CO3, MeOH, 60%.
proton, protection of the amide proton would effect the
desired introduction of an azide group. Thus, after removal
of the pivaloyl group of 33, alcohol 34 was treated with
NaH, followed by Boc protection to give the oxazolidinone
35. The primary TBS ether was selectively removed (36),
followed by successive mesylation and azidation to give the
desired 37. Hydrolysis of the oxazolidinone proceeded
under Cs2CO3 conditions, and the resulted primary alcohol
(38) was oxidized with TEMPO to give the amino acid 39.
Amino acid 39 was coupled with 10 to give dipeptide 40
(Scheme 6). After deprotection of the Boc group, coupling
reaction with 13 was attempted. Unfortunately, no expected
product was obtained under several reaction conditions.
Accordingly, the TBS and Boc groups of 40 were removed,
and the resulting amino alcohol was submitted to coupling
with 13 to give tripeptide 41 in good yield. To examine
protection with a pivaloyl (32) and TBS groups, gave 33.
After selective removal of the primary TBS group, an
alcohol generated was submitted to mesylation and azida-
tion. However, the required substitution did not proceed.
Based on our working-hypothesis of influence of the amide
Scheme 5. Reagents and conditions: (a) Ph3P, DEAD, DPPA, THF, 92%. (b) Ph3P, H2O, THF. (c) Boc2O, NaHCO3, H2O–dioxane, 92% in 2 steps. (d) H2,
10% Pd–C, EtOH. (e) PivCl, pyr., 66% in 2 steps. (f) TBSOTf, 2,6-lutidine, CH2Cl2, 89%. (g) DIBAL-H, CH2Cl2, 92%. (h) i. NaH, THF, 93%; ii. Boc2O,
DMAP, Et3N, THF, 86%. (i) CSA, MeOH, 67%. (j) i. MsCl, pyr.; ii. NaN3, DMF, 80%. (k) Cs2CO3, MeOH, 85%. (l) TEMPO, KBr, NaClO, NaHCO3 aq.,
acetone, 85%.

M. Ito et al. / Tetrahedron 60 (2004) 5623–5634
5627
Scheme 7. Reagents and conditions: (a) TTN, THF–MeOH (4:1), 44: 56%, 45: 47%, 46: 56%. (b) i. Ph3P, H2O, THF; ii. HgCl2, Et3N, DMF, 72%; iii. H2,
NaOAc, 10% Pd–C, MeOH, quant; iv. TBAF, THF, 70%; v. 1 M aq. NaOH, MeOH, quant; vi. TFA, CH2Cl2, quant.
adaptability to the TTN cyclization, acetonide 42 and TBS
derivative 43 were produced from 41. Among the oxidation
reactions of 41, 42 and 43, 41 and 42 provided not the
desired cyclic isodityrosine but the spirodienone-type
compounds 44 and 45 in moderate yields, while the TBS
derivative 43 provided the desired product 46 in 56% yield.
Compound 46 in hand was derivatized by essentially00the
same procedure as in the case of 24 to afford (300R,4 S)-
eurypamide A 47 (Scheme 7). Under the full range of
spectroscopic data, the synthetic sample was super-
imposable to those of the reported data.
700 (FAB) spectrometers. Preparative and analytical TLCs
were carried out on silica gel plate (Kieselgel 60 PF254
,
E. Merck AG. Germany) using UV light and 5%
molybdophosphoric acid in ethanol or 2% ninhydrin in
1-propanol for detection. Kanto Chemical silica 60 N
(spherical, neutral, 63–210 mm) was used for column
chromatography.
4.2. Synthesis of eurypamide B 2 and D 4
4.2.1. N-tert-Butoxycarbonyl-L-threonyl-o,o0-dibromo-L-
tyrosine methyl ester 12a. A mixture of 11a (1.83 g,
8.4 mmol), 10 (3.63 g, 8.4 mmol), BOP reagent (3.69 g,
8.35 mmol), and Et3N (2 mL, 15 mmol) in DMF (17 mL)
was stirred overnight. After the addition of 5% KHSO4 aq.,
the mixture was extracted with EtOAc, then washed with
brine. The organic layer was dried (Na2SO4), and evapo-
rated. The residue was purified by silica-gel column
chromatography (1/1 hexane/EtOAc) to give 12a as an oil
(4.15 g, 90%): IR (film) 3392, 1662, 1477, 1367, 1241,
1162 cm21; dH 1.20 (3H, d, J¼6.4 Hz), 1.45 (9H, s), 2.90
(1H, s), 2.93 (1H, dd, J¼5.6, 14 Hz), 3.09 (1H, dd, J¼5.6,
14 Hz), 3.76 (3H, s), 4.05 (1H, m), 4.39 (1H, m), 4.75 (1H,
m), 5.43 (1H, d, J¼8.1 Hz), 5.92 (1H, s), 7.12 (1H, d, J¼
7.3 Hz), 7.24 (2H, s); dC 18.4, 28.3, 36.3, 52.6, 53.3, 58.3,
66.8, 80.5, 109.9, 130.2, 132.6, 148.5, 156.2, 171.0;
HREIMS m/z 553.0159, calcd for C19H2779Br2N2O7
(MþþH) 553.0185.
4.2.2. N-tert-Butoxycarbonyl-o,o0-diiodo-L-tyrosyl-L-
threonyl-o,o0-dibromo-L-tyrosine methyl ester 14a. A
solution of 12a (524 mg, 0.94 mmol) in TFA (2 mL)–
CH2Cl2 (6 mL) was stirred at 0 8C for 3 h. After
evaporation, the residue was dissolved in DMF (0.6 mL),
containing 13 (504.2 mg, 0.94 mmol), BOP reagent
(418 mg, 0.94 mmol) and Et3N (0.27 mL, 1.9 mmol) were
added at 0 8C. After being stirred overnight, the reaction was
quenched by the addition of 5% KHSO4 aq., extracted with
3. Conclusion
Eurypamides A 1, B 2, and D 4, were successfully
synthesized by employing the TTN-mediated oxidative
cyclization of the corresponding phenols 14a, 14b, 24, and
43. In addition to supplying the spectroscopic data of
pure 2 and 4, structural revision of 1 was ac0c0 omplished:
the dihydroxyarginine residue of 1 possesses (2 S,300R,400S)-
configuration 47.
4. Experimental
4.1. General
All reactions were carried out under an argon atmosphere
unless otherwise noted. Optical rotations were measured on
a Jasco DIR-360 digital polarimeter with a sodium (D line)
lamp. IR spectra were recorded on a Jasco Model A-202
1
spectrophotometer. H NMR spectra and 13C NMR spectra
were obtained on JNM-EX270 and JNM-GX400 spectro-
meters in CDCl3 using tetramethylsilane as an internal
standard, as otherwise stated. High-resolution mass spectra
were obtained on a Hitachi M-80B GC-MS spectrometer
operating at the ionization energy of 70 eV or JEOL JMS-

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M. Ito et al. / Tetrahedron 60 (2004) 5623–5634
EtOAc, and washed with brine. The organic layer was dried
(Na2SO4), and evaporated. The residue was purified by
silica-gel column chromatography (2/3 hexane/EtOAc) to
give 14a as an amorphous solid (850 mg, 91% in 2 steps):
[a]2D0 þ4.2 (c 1.00, CHCl3); IR (film) 3388, 1650, 1519,
1477, 1457, 1241, 1160 cm21; dH 1.10 (3H, d, J¼6.8 Hz),
1.43 (9H, s), 2.94 (2H, complex), 3.05 (1H, dd, J¼5.6,
14 Hz), 3.75 (3H, s), 4.31 (3H, complex), 4.72 (1H, m), 4.96
(1H, d, J¼7.6 Hz), 5.72 (1H, s), 5.96 (1H, s), 6.96 (1H, d,
J¼7.6 Hz), 7.14 (1H, d, J¼7.8 Hz), 7.24 (2H, s), 7.51
(2H, s); dC 19.8, 28.7, 36.8, 36.9, 52.8, 55.1, 56.3, 57.1,
59.7, 68.5, 80.9, 85.1, 112.0, 131.9, 134.0, 134.6, 141.4,
151.1, 155.3, 157.6, 171.9, 172.7, 173.7; HRFABMS m/z
0.03 mmol) in MeOH (0.5 mL)–1 M NaOH aq. (0.5 mL)
at 0 8C was stirred for 30 min. After treatment with
Amberlite IR 120B (Hþ), evaporation gave a residue,
which was dissolved in CH2Cl2 (1 mL)–TFA (1 mL). After
being stirred at 0 8C for 2 h, the mixture was evaporated to
give 2 as an oil (12 mg, 90%): [a]2D0 222.1 (c 1.00, MeOH);
IR (film) 3407, 1653, 1508, 1384, 1220 cm21; dH (CD3OD)
1.14 (3H, d, J¼6.4 Hz), 2.66 (1H, t, J¼13 Hz), 2.93 (1H, dd,
J¼5, 15 Hz), 3.20 (1H, broad d, J¼15 Hz), 3.42 (1H, dd,
J¼4, 13 Hz), 4.16 (2H, complex), 4.43 (1H, d, J¼2.4 Hz),
4.72 (1H, dd, J¼4, 13 Hz), 5.94 (1H, d, J¼2 Hz), 6.65 (1H,
d, J¼2, 8 Hz), 6.83 (1H, d, J¼8 Hz), 6.86 (1H, d, J¼2,
8 Hz), 7.02 (1H, dd, J¼2, 8 Hz), 7.19 (1H, d, J¼2, 8 Hz),
7.41 (1H, d, J¼2, 8 Hz); dC (CD3OD) 19.9, 36.9, 39.8, 53.9,
58.7, 58.8, 69.5, 116.7, 117.0, 122.7, 123.4, 124.5, 124.9,
131.8, 133.0, 135.7, 147.2, 149.7, 154.8, 168.4, 168.5,
170.7; HRFABMS m/z 444.1758, calcd for C22H26N3O7
(MþþH) 444.1771.
79
967.8734, calcd for C28H34 Br2I2N3O9 (MþþH) 967.8751.
Found: C, 34.75; H, 3.68; N, 4.22. Calcd for
C28H33Br2I2N3O9: C, 34.70; H, 3.43; N, 4.34.
4.2.3. Cyclic tripeptide 15a. To a solution of 14a
(329.2 mg, 0.34 mmol) in THF (140 mL) and MeOH
(35 mL) was added TTN (420 mg, 1.0 mmol) at 0 8C.
After being stirred for 1 h, Na2SO3 and H2O (1drop) were
added. The mixture was passed through a Celite pad, and
evaporated to give a residue. Purification by silica-gel
column chromatography (1/2 hexane/EtOAc) gave 15a as
an oil (206.6 mg, 72%): [a]2D0 þ6.5 (c 1.00, CHCl3); IR
(film) 3332, 1654, 1490, 1455, 1276, 1253, 1172 cm21; dH
1.00 (3H, d, J¼6.4 Hz), 1.49 (9H, s), 2.57 (1H, t, J¼
12.8 Hz), 2.72 (1H, d, J¼12.4 Hz), 3.19 (1H, dd, J¼4.8,
13.2 Hz), 3.35 (1H, dd, J¼4.0, 13.2 Hz), 3.62 (1H, m), 3.85
(3H, s), 4.05 (1H, m), 4.37 (1H, m), 4.51 (1H, m), 5.01 (1H,
m), 5.46 (1H, d, J¼7.2 Hz), 5.75 (1H, d, J¼2 Hz), 6.32 (1H,
s), 6.71 (1H, d, J¼7.6 Hz), 7.06 (1H, d, J¼1.6 Hz), 7.36
(1H, d, J¼1.6 Hz), 7.56 (1H, d, J¼9.6 Hz), 7.66 (1H, s); dC
17.2, 28.5, 37.0, 38.8, 52.7, 53.0, 53.7, 56.2, 56.2, 67.7,
79.8, 82.7, 113.5, 116.8, 128.9, 133.8, 134.3, 135.0, 137.0,
142.8, 146.9, 155.0, 168.4, 169.2; HRFABMS m/z
4.2.6. Chiral GC analysis of eurypamide B 2. Compound
2 (1 mg) in 6 M aq. HCl was heated at 120 8C overnight in
the sealed tube. After evaporation, the residue was heated in
HCl/MeOH for 1 h. The mixture was then evaporated, and
the residue was treated with trifluoroacetic anhydride
(0.5 mL) for 1 h under the same conditions. The mixture
was evaporated, and the residue was dissolved in Et2O
(0.5 mL). The resulting solution was submitted to Chiral GC
analysis using Chirasil–Val column (25 m£0.25 mm; the
program rate: 50 8C (10 min), then 50–200 8C at 4 8C/min).
The GC analysis for the amino acids established the
presence of L-threonine (19.48 min).
4.2.7. N-tert-Butoxycarbonyl-L-allo-threonyl-o,o0-
dibromo-L-tyrosine methyl ester 12b. A mixture of 11b
(65.2 mg, 0.3 mmol), 10 (129 mg, 0.3 mmol), BOP reagent
(132 mg, 0.3 mmol), and Et3N (0.084 mL, 0.6 mmol) in
DMF (2 mL) was stirred overnight. Work-up and purifi-
cation by silica-gel column chromatography (1/1 hexane/
EtOAc) gave 12b as an oil (140.1 mg, 85%): IR (film) 3382,
1658, 1479, 1241, 1160 cm21; dH 1.26 (3H, d, J¼6.4 Hz),
1.44 (9H, s), 2.96 (1H, dd, J¼6.8, 14 Hz), 3.06 (1H, dd,
J¼5.2, 14 Hz), 3.71 (1H, m), 3.73 (3H, s), 3.93 (1H, m),
4.05 (1H, m), 4.78 (1H, m), 5.53 (1H, d, J¼8.0 Hz), 6.25
(1H, s), 7.06 (1H, d, J¼7.6 Hz), 7.28 (2H, s); dC 19.8, 28.3,
36.2, 52.6, 52.7, 53.3, 58.5, 69.2, 76.6, 76.9, 77.2, 77.3,
80.5, 109.9, 130.3, 132.6, 148.6, 156.1, 171.1, 171.2;
HREIMS m/z 553.0223, calcd for C19H2779Br2N2O7
(MþþH) 553.0185.
4.2.8. N-tert-Butoxycarbonyl-o,o0-diiodo-L-tyrosyl-L-
allo-threonyl-o,o0-dibromo-L-tyrosine methyl ester 14b.
To a solution of 12b (213.3 mg, 0.385 mmol) in CH2Cl2
(1.5 mL) was added TFA (1.5 mL) at 0 8C. After being
stirred for 1 h, the mixture was concentrated in vacuo. The
residue was dissolved in DMF (3 mL), 13 (250 mg,
0.46 mmol), EDC (82.6 mg, 0.43 mmol), HOBt (70.6 mg,
0.43 mmol), and Et3N (0.1 mL, 0.71 mmol) were added at
0 8C; the mixture was stirred overnight. Work-up and
purification by silica-gel column chromatography (2/3
hexane/acetone) gave 14b as an oil (340.4 mg, 91% in 2
steps): [a]2D0 þ1.5 (c 1.00, MeOH); IR (film) 3361,
1564 cm21; dH (CD3OD) 1.16 (3H, d, J¼6.4 Hz), 1.38
(9H, s), 2.64 (1H, dd, J¼10, 14 Hz), 2.94 (2H, complex),
79
841.9602, calcd for C28H33 Br81BrIN3O9 (MþþH)
841.9608.
4.2.4. N-tert-Butoxycarbonyl-eurypamide B methyl ester
16a. A solution of 15a (90.6 mg, 0.11 mmol) in MeOH
(1 mL) containing catalytic amounts of 10% Pd/C and
NaOAc (26.5 mg, 0.32 mmol) was stirred overnight at
ambient temperature in a hydrogen atmosphere. After
filtration, the filtrate was evaporated. The residue was
purified by silica-gel column chromatography (20/1 CHCl3/
MeOH) to give 16a as an oil (66.3 mg, 100%): [a]2D0 þ22.4
(c 1.00, MeOH); IR (film) 3311, 1654, 1508, 1438, 1367,
1276, 1226, 1166 cm21; dH (CD3OD) 1.11 (3H, d, J¼
6.4 Hz), 1.42 (9H, s), 2.66 (1H, t, J¼12.8 Hz), 2.90 (2H, m),
3.29–3.36 (3H, complex), 3.80 (3H, s), 4.06 (1H, m), 4.39
(2H, complex), 4.80 (1H, m), 5.37 (1H, d, J¼8.4 Hz), 5.88
(1H, d, J¼1.6 Hz), 6.52 (1H, dd, J¼2.4, 8.4 Hz), 6.76 (1H,
d, J¼8.4 Hz), 6.87 (1H, dd, J¼2.4, 8.4 Hz), 7.01 (1H, dd,
J¼2.4, 8.4 Hz), 7.17 (1H, dd, J¼2.4, 8.4 Hz), 7.37 (1H, dd,
J¼2.4, 8.4 Hz), 7.85 (1H, d, J¼9.6 Hz), 8.33 (1H, d, J¼
10.4 Hz); dC (CD3OD) 19.7, 28.7, 38.3, 39.5, 52.9, 54.7,
54.9, 58.6, 69.6, 80.7, 116.5, 117.1, 122.7, 123.4, 124.7,
127.9, 131.6, 133.1, 135.0, 146.3, 149.2, 155.3, 156.9,
170.9, 172.2, 173.0; HRFABMS m/z 558.2467, calcd for
C28H36N3O9 (MþþH) 558.2451.
4.2.5. Eurypamide B 2. A solution of 16a (17 mg,

M. Ito et al. / Tetrahedron 60 (2004) 5623–5634
5629
3.04 (1H, dd, J¼6.0, 14 Hz), 3.70 (3H, s), 3.97 (1H, m), 4.24
(1H, dd, J¼6.0, 10 Hz), 4.33 (1H, d, J¼6.4 Hz), 4.65 (1H,
m), 7.34 (2H, s), 7.62 (2H, s); dC (CD3OD) 19.7, 28.6, 28.7,
36.9, 37.0, 52.8, 55.2, 57.0, 59.8, 68.9, 80.8, 85.1, 112.0,
132.0, 134.1, 134.6, 141.4, 151.1, 155.4, 157.6, 171.7,
172.8, 173.6; HRFABMS m/z 969.8769, calcd for
4.09 (1H, m), 4.54 (1H, dd, J¼6, 10 Hz), 4.75 (1H, m), 5.92
(1H, d, J¼2 Hz), 6.66 (1H, dd, J¼2, 8 Hz), 6.83 (1H, d,
J¼8 Hz), 6.88 (1H, dd, J¼2, 8.4 Hz), 7.02 (1H, dd, J¼2,
8.4 Hz), 7.22 (1H, dd, J¼2, 8.4 Hz), 7.39 (1H, dd, J¼2,
8.4 Hz), 8.20 (1H, d, J¼10 Hz), 8.38 (1H, d, J¼10 Hz); dC
(CD3OD) 18.9, 36.8, 37.8, 55.1, 58.7, 62.3, 69.2, 116.8,
117.0, 122.7, 123.4, 124.5, 124.9, 128.5, 131.7, 133.1,
135.6, 137.4, 147.2, 149.7, 154.8, 168.5, 176.7; HRFABMS
m/z 444.1754, calcd for C22H26N3O7 (MþþH) 444.1771.
79
C28H34 Br81BrI2N3O9 (MþþH) 969.8731.
4.2.9. Cyclic tripeptide 15b. To a solution of 14b (95.7 mg,
0.1 mmol) in THF (40 mL) and MeOH (10 mL) was added
TTN (110 mg, 0.24 mmol) at 0 8C. After being stirred for
1 h, the reaction was quenched by the addition of Na2SO3
and H2O (1drop). The mixture was passed through a Celite
pad, and evaporated. The residue was purified by silica-gel
column chromatography (10/1 CHCl3/MeOH) to give 15b
as an amorphous solid (50.9 mg, 61%): [a]2D0 þ3.6 (c 1.00,
CHCl3); IR (film) 3332, 1656, 1490, 1455, 1421, 1367,
1253, 1170 cm21; dH 1.11 (3H, d, J¼6.0 Hz), 1.44 (9H, s),
2.62 (2H, complex), 3.15 (1H, dd, J¼6.4, 13 Hz), 3.36 (1H,
dd, J¼4.0, 13 Hz), 3.81 (3H, s), 4.39 (1H, m), 4.49 (1H, m),
4.97 (1H, m), 5.41 (1H, d, J¼7.2 Hz), 5.66 (1H, s), 6.49
(1H, broad), 6.87 (1H, d, J¼8 Hz), 7.05 (1H, broad s), 7.40
(1H, d, J¼2 Hz), 7.58 (1 h, d, J¼9 Hz), 7.64 (1H, broad s);
dC 18.4, 19.5, 28.5, 36.8, 38.1, 52.9, 53.0, 53.5, 56.7, 58.4,
69.2, 79.8, 82.7, 113.5, 117.1, 118.5, 129.0, 133.4, 134.2,
134.9, 137.0, 142.8, 144.0, 146.9, 155.0, 169.1, 169.9,
171.1, 171.3; HRFABMS m/z 839.9646, calcd for
4.3. Synthesis of (3S,4R)-eurypamide A 1
4.3.1. 2-(N-Benzyloxycarbonyl)amino-2-deoxy-3,4,5-tri-
(tert-butyldimethylsilyloxy)-1-pivaloyl-D-arabinitol 19.
To a solution of 17 (2.1 g, 4.1 mmol) in CH2Cl2 (30 mL)
was added DIBAL-H (6 mL, 1 M in toluene) at 278 8C; the
mixture was stirred for 1 h. The reaction mixture was
partitioned between EtOAc and H2O. The organic layer was
washed with Rochelle salt aq. and brine, dried (Na2SO4),
then evaporated to give a residue, which was dissolved in
MeOH (30 mL), and NaBH4 (120 mg, 3 mmol) was added
at 0 8C. After being stirred for 30 min at ambient
temperature, the resulted mixture was partitioned between
EtOAc and H2O. Work-up and purification by silica-gel
column chromatography (3/1 hexane/EtOAc) gave 18 as an
oil (1.82 g, 84% in 2 steps): dH 0.07–0.16 (12H, complex),
0.90 (18H, s), 1.17 (9H, s), 3.53 (1H, dd, J¼6.8, 9.6 Hz),
3.68 (1H, m), 3.78 (4H, complex), 4.00 (1H, m), 5.10 (2H,
complex), 5.63 (1H, d, J¼8.8 Hz), 7.35 (5H, complex). This
compound was immediately submitted the next step.
79
C28H33 Br2IN3O9 (MþþH) 839.9628.
4.2.10. N-tert-Butoxycarbonyl-eurypamide D methyl
ester 16b. A solution of 15b (26 mg, 0.031 mmol) in
MeOH (1 mL) containing catalytic amounts of 10% Pd/C
and NaOAc (7.6 mg, 0.093 mmol) was stirred at ambient
temperature overnight in a hydrogen atmosphere. Work-up
and purification by silica-gel column chromatography (10/1
CHCl3/MeOH) gave 16b as an oil (21.1 mg, 100%): [a]D20
þ14.9 (c 1.00, MeOH); IR (film) 3419, 1656, 1508, 1438,
1367, 1276, 1226, 1166 cm21; dH (CD3OD) 1.12 (3H, d,
J¼6.4 Hz), 1.43 (9H, s), 2.68 (1H, t, J¼12.4 Hz), 2.85 (1H,
d, J¼14 Hz), 2.95 (1H, dd, J¼7, 14 Hz), 3.34 (1H, dd, J¼4,
13 Hz), 3.79 (3H, s), 3.92 (1H, m), 4.34 (1H, m), 4.44 (1H,
m), 4.79 (1H, dd, J¼4, 13 Hz) 5.46 (1H, d, J¼8.4 Hz), 5.87
(1H, d, J¼1.6 Hz), 6.53 (1H, dd, J¼2.4, 8.4 Hz), 6.76 (1H,
d, J¼8 Hz), 6.88 (1H, dd, J¼2.4, 8.4 Hz), 7.01 (1H, dd,
J¼2.4, 8.4 Hz), 7.19 (1H, dd, J¼2.4, 8.4 Hz), 7.35 (1H, dd,
J¼1.6, 8 Hz), 7.95 (1H, d, J¼9.2 Hz); dC (CD3OD) 19.1,
28.7, 38.1, 39.1, 52.9, 54.7, 54.8, 55.4, 58.6, 69.5, 80.7,
116.6, 117.1, 119.3, 122.6, 123.3, 124.8, 128.1, 131.3,
133.1, 134.9, 146.4, 155.5, 170.5, 172.2, 172.9; HRFABMS
m/z 558.2464, calcd for C28H36N3O9 (MþþH) 558.2451.
To a solution of 18 (421 mg, 0.82 mmol) in CH2Cl2 (8 mL)
was added pivaloyl chloride (0.5 mL, 4.1 mmol) at 0 8C; the
mixture was stirred at ambient temperature for 4 h. The
reaction was quenched by the addition of 5% KHSO4 aq.,
and extracted with EtOAc. The organic layer was washed
with saturated NaHCO3 aq. and brine, dried (Na2SO4), then
evaporated. A mixture of the residue (392 mg, 0.66 mmol),
2,6-lutidine (0.6 mL, 5.2 mmol), and TBDMSOTf (0.6 mL,
2.6 mmol) in CH2Cl2 (6 mL) was stirred for 1 h. Work-up
and purification by silica-gel column chromatography (20/1
hexane/EtOAc) gave 19 as an amorphous solid (398 mg,
85%): [a]2D0 þ6.0 (c 1.00, CHCl3); IR (film) 1733, 1471,
1255, 1149 cm21; dH 0.04 (3H, s), 0.05 83H, s), 0.06 (6H,
s), 0.12 (3H, s), 0.87 (9H, s), 0.89 (9H, s), 0.91 (9H, s), 1.18
(9H, s), 3.55 (1H, dd, J¼5.6, 11 Hz), 3.64 (1H, dd, J¼5.2,
11 Hz), 3.71 (1H, m), 3.89 (1H, t, J¼11 Hz), 3.99 (1H, d,
J¼2.8 Hz), 4.12 (2H, complex), 4.99 (1H, d, J¼12.8 Hz),
5.12 (1H, d, J¼12.8 Hz), 5.23 (1H, d, J¼7.2 Hz), 7.33 (5H,
complex); dC 25.1, 24.9, 24.7, 24.1, 23.7, 18.2, 18.3,
18.5, 25.8, 26.0, 27.3, 38.8, 50.2, 63.0, 64.7, 66.6, 71.0,
127.9, 128.1, 128.2, 128.3, 136.4, 155.5, 177.8; HREIMS
m/z 712.4443, calcd for C36H70NO7Si3 (MþþH) 712.4460.
4.2.11. Eurypamide D 4. To a solution of 16b (16.6 mg,
0.03 mmol) in MeOH (0.5 mL) was added 1 M NaOH aq.
(0.5 mL) at 0 8C; the mixture was stirred for 30 min. After
treatment with Amberlite IR 120B (Hþ), evaporation gave a
residue, which was dissolved in CH2Cl2 (1 mL)–TFA
(1 mL) at 0 8C. After being stirred for 2 h, the mixture was
evaporated, and the residue was co-evaporated several times
with toluene to give 4 as an oil (12 mg, 92%): [a]2D0 221.5 (c
1.00, MeOH); IR (film) 3297, 1666, 15081438, 1276,
1208 cm21; dH (CD3OD) 1.14 (3H, d, J¼6.4 Hz), 2.69 (1H,
t, J¼12.7 Hz), 2.94 (1H, dd, J¼6.0, 15 Hz), 3.20 (1H, broad
d, J¼14 Hz), 3.40 (1H, dd, J¼4.0, 13 Hz), 4.04 (1H, m),
4.3.2. 2-(N-tert-Butoxycarbonyl)amino-2-deoxy-3,4,5-
tri-(tert-butyldimethylsilyloxy)-1-pivaloyl-D-arabinitol
20a. A solution of 19 (0.8 g, 1.1 mmol) in MeOH (10 mL)
containing of catalytic amounts of 10% Pd/C was stirred for
1 h at ambient temperature in a hydrogen atmosphere. The
mixture was passed through a Celite pad, and evaporated.
A mixture of the residue, NaHCO3 (150 mg, 1.8 mmol), and
Boc2O (0.4 mL, 1.6 mmol) in H2O (6 mL)–1,4-dioxane
(6 mL) was stirred for 1 h. Work-up and purification by

5630
M. Ito et al. / Tetrahedron 60 (2004) 5623–5634
silica-gel column chromatography (20/1 hexane/EtOAc)
gave 20a as an oil (0.77 g, 100%): [a]2D0 þ1.4 (c 1.00,
CHCl3); IR (film) 1720, 1482, 1390, 1365, 1282, 1255,
1151 cm21; dH 0.06 (18H, complex), 0.89 (27H, complex),
1.18 (9H, s), 1.45 (9H, s), 3.53–3.71 (3H, complex), 3.84–
4.11 (4H, complex), 5.00 (1H, d, J¼7.2 Hz); dC 25.1, 24.9,
23.9, 23.7, 18.2, 18.3, 18.5, 26.1, 27.2, 27.5, 38.7, 49.9,
62.8, 64.8, 71.2, 76.1, 79.1, 154.9, 177.9; HREIMS m/z
678.4607, calcd for C33H72NO7Si3 (MþþH) 678.4616.
Found: C, 58.79; H, 10.45; N, 1.97. Calcd for
C33H71NO7Si3: C58.44; H, 10.55; N, 2.07.
CHCl3); IR (film) 3446, 2102, 1697, 1496, 1473, 1390,
1367, 1255 cm21; dH 0.11 (3H, s), 0.15 (9H, s), 0.90 (9H, s),
0.93 (9H, s), 1.43 (9H, s), 2.94 (1H, m), 3.31 (1H, dd, J¼4.8,
13 Hz), 3.45 (1H, dd, J¼3.6, 13 Hz), 3.56 (1H, m), 3.72–
3.81 (3H, complex), 3.93 (1H, dd, J¼2, 5.2 Hz), 5.12 (1H,
d, J¼7.3 Hz); dC 24.9, 24.8, 24.1, 24.0, 18.1, 18.3, 26.0,
26.1, 28.4, 53.5, 53.9, 63.7, 72.1, 73.4, 79.8, 156.5;
HREIMS m/z 505.3191, calcd for C22H48N4O5Si2
(MþþH) 505.3241.
4.3.6. Amino acid 22. To a solution of 21b (91.7 mg,
0.182 mmol) in acetone (0.5 mL) and 5% NaHCO3 aq.
(0.5 mL) were added TEMPO (35.7 mg, 0.20 mmol), KBr
(2.8 mg, 0.018 mmol), and 8% NaClO aq. (0.5 mL). After
being stirred for 3 h, the reaction was quenched by the
addition of 5% KHSO4 aq. The mixture was partitioned
between EtOAc and H2O, and the aqueous layer was
extracted with EtOAc. The combined organic layer was
dried (Na2SO4), then evaporated. The residue was purified
by silica-gel column chromatography (20/1 hexane/EtOAc
and 10/1 CHCl3/MeOH) to give 22 as an oil (78 mg, 83%):
IR (film) 2100, 1718, 1471, 1388, 1253 cm21; dH (CD3OD)
0.07 (3H, s), 0.13 (3H, s), 0.16 (3H, s), 0.17 (3H, s), 0.89
(9H, s), 0.95 (9H, s), 1.43 (9H, s), 3.33 (1H, t, J¼3.2 Hz),
3.55 (1H, dd, J¼2.8, 13.2 Hz), 3.83 (1H, dd, J¼3.6, 6.8 Hz),
4.33 (1H, broad d, J¼6.8 Hz), 4.40 (1H, d, J¼9.2 Hz), 5.55
(1H, d, J¼9.2 Hz); dC (CD3OD) 25.1, 24.4, 24.3, 24.2,
23.4, 23.3, 18.9, 19.1, 26.5, 26.6, 28.7, 54.0, 56.2, 73.7,
74.8, 80.9, 157.7, 174.4; HRFABMS m/z 519.3056, calcd
for C22H47N4O6Si2 (MþþH) 519.3034.
4.3.3. 2-(N-tert-Butoxycarbonyl)amino-2-deoxy-3,4-di-
(tert-butyldimethylsilyloxy)-1-pivaloyl-D-arabinitol 20b.
To a solution of 20a (760 mg, 1.1 mmol) in MeOH (10 mL)
was added a catalytic amount of PPTS at 0 8C; the mixture
was stirred overnight. Work-up and purification by silica-
gel column chromatography (10/1 hexane/EtOAc) gave 20b
as an oil (640 mg, 77%): [a]2D0 þ3.2 (c 1.00, CHCl3); IR
(film) 3450, 2956, 1720, 1482, 1390, 1255, 1155 cm21; dH
0.07–0.18 (12H, complex), 0.90 (18H, complex), 1.18 (9H,
s), 1.42 (9H, s), 3.63 (1H, m), 3.69 (3H, complex), 3.89 (2H,
complex), 4.07 (2H, complex), 4.88 (1H, d, J¼7.8 Hz); dC
25.0, 24.8, 24.4, 24.2, 24.15, 18.1, 18.4, 25.9, 26.2,
27.2, 28.4, 38.7, 50.0, 62.5, 62.6, 70.7, 73.2, 79.4, 155.0,
177.8; HREIMS m/z 564.3778, calcd for C27H58NO7Si2
(MþþH) 564.3752. Found: C, 57.53; H, 10.07; N, 2.43.
Calcd for C27H71NO7Si2: C, 57.51; H, 10.19; N, 2.48.
4.3.4. Azide 21a. To a solution of 20b (557 mg, 0.99 mmol)
in pyridine (5 mL) was added MsCl (0.1 mL, 1.3 mmol) at
0 8C. After being stirred for 2 h at the same temperature, the
mixture was partitioned between EtOAc and H2O, the
organic layer was washed with 5% KHSO4 aq., followed by
brine. The organic layer was dried (Na2SO4), and concen-
trated in vacuo. A mixture of the residue and NaN3 (514 mg,
7.9 mmol) in DMF (3 mL) was heated at 80 8C for 4 h. After
being cooled to ambient temperature; the mixture was
filtered. The filtrate was partitioned between EtOAc and
H2O, the organic layer was washed with brine. The organic
layer was dried (Na2SO4), and evaporated. Purification of
the residue by a silica gel column (40/1 hexane/EtOAc)
gave 21a as an oil (454 mg, 77%): [a]2D0 þ13.1 (c 1.00,
CHCl3); IR (film) 3450, 2102, 1720, 1473, 1253 cm21; dH
0.09 (3H, s), 0.13 (3H, s), 0.15 (6H, s), 0.92 (9H, complex),
0.94 (9H, s), 1.21 (9H, s), 1.43 (9H, s), 3.27 (1H, dd, J¼4.6,
13 Hz), 3.45 (1H, dd, J¼3, 13 Hz), 3.79 (1H, m), 3.92 (1H,
m), 4.07 (2H, complex), 4.81 (1H, d, J¼7.6 Hz); dC 25.1,
25.0, 23.85, 23.8, 18.1, 18.5, 26.0, 26.3, 27.2, 28.4, 38.8,
49.2, 50.0, 53.4, 62.5, 72.0, 73.1, 79.6, 154.9, 177.8;
HREIMS m/z 589.3830, calcd for C27H57N4O6Si2 (MþþH)
589.3816.
4.3.7. Dipeptide 23. To a solution of 22 (99.2 mg,
0.19 mmol) and 10 (102 mg, 0.22 mmol) in DMF
(1.5 mL) were added BOP reagent (92.2 mg, 0.20 mmol)
and Et3N (0.10 mL, 0.68 mmol) at 0 8C, the reaction
mixture was stirred overnight. Work-up and purification
by silica-gel column chromatography (8/1 hexane/EtOAc)
gave 23 as an oil (140.1 mg, 85%): [a]2D0 þ15.7 (c 1.0,
CHCl3); IR (film) 3434, 2103, 1671, 1477 cm21; dH 0.05
(3H, s), 0.13 (6H, s), 0.16 (3H, s), 0.83 (9H, s), 0.90 (9H, s),
1.44 (9H, s), 2.95 (2H, complex), 3.28 (1H, dd, J¼4.4,
12.8 Hz), 3.40 (1H, dd, J¼3.2, 12.8 Hz), 3.72 (3H, s), 3.75
(1H, m), 4.26 (1H, m), 4.35 (1H, m), 4.76 (1H, m), 5.41 (1H,
d, J¼6.8 Hz), 5.91 (1H, s), 7.13 (1H, d, J¼7.2 Hz), 7.22
(2H, s); dC 25.1, 24.8, 24.6, 23.9, 18.0, 18.1, 25.9, 28.2,
36.8, 52.4, 53.1, 53.3, 55.2, 72.4, 80.3, 100.5, 109.7, 130.6,
132.5, 148.4, 155.8, 170.2, 171.0; HRFABMS m/z
852.2023, calcd for C32H5679Br2N5O8Si2 (MþþH)
852.2034.
4.3.8. Tripeptide 24. To a solution of 23 (160.4 mg,
0.19 mmol) in CH2Cl2 (1 mL) was added TFA (1 mL) at
0 8C. After being stirred for 1 h, the mixture was evaporated.
A mixture of the residue, 13 (112.3 mg, 0.210 mmol), BOP
reagent (90.3 mg, 0.23 mmol) and Et3N (0.10 mL,
0.71 mmol) in DMF (1.8 mL) was stirred overnight.
Work-up and purification by silica-gel column chroma-
tography (6/1 hexane/acetone) gave 24 as an oil (155 mg,
65% in 2 steps): [a]2D0 þ5.1 (c 1.00, CHCl3); IR (film) 3390,
2103, 1660, 1253 cm21; dH 0.01 (1H, s), 0.03 (3H, s), 0.11
(3H, s), 0.16 (3H, s), 0.84 (9H, s), 0.89 (9H, s), 1.43 (9H, s),
2.90 (1H, m), 2.93 (1H, dd, J¼6.8, 13.2 Hz), 3.03 (1H, dd,
J¼6.8, 14 Hz), 3.10 (1H, m), 3.26 (1H, dd, J¼3.2, 13 Hz),
4.3.5. Azide alcohol 21b. To a solution of 21a (326 mg,
0.55 mmol) in CH2Cl2 (4 mL) was added DIBAL-H
(2.0 mL, 1 M in toluene) at 278 8C; the mixture was stirred
for 1 h. The reaction was quenched by the addition of
EtOAc, and the mixture was partitioned between EtOAc and
H2O. The organic layer was washed with Rochelle salt aq.,
followed by brine. The organic layer was dried (Na2SO4),
and concentrated in vacuo. The residue was purified by
silica-gel column chromatography (8/1–4/1 hexane/EtOAc)
to give 21b as an oil (252 mg, 90%): [a]2D0 þ5.2 (c 1.0,

M. Ito et al. / Tetrahedron 60 (2004) 5623–5634
5631
3.41 (1H, dd, J¼3.2, 13 Hz), 3.68 (1H, m), 3.73 (3H, s), 4.21
(1H, m), 4.33 (1H, d, J¼6.8 Hz), 4.54 (1H, dd, J¼2.4,
7.2 Hz), 4.76 (1H, m), 4.94 (1H, d, J¼8.0 Hz), 5.71 (1H, s),
5.91 (1H, s), 6.90 (1H, d, J¼7.8 Hz), 7.10 (1H, d, J¼
7.6 Hz), 7.22 (2H, s), 7.53 (2H, s); dC 24.9, 24.6, 23.8,
14.3, 18.0, 18.1, 21.1, 25.9, 26.8, 27.8, 28.3, 36.6, 52.5,
53.0, 53.5, 54.0, 55.7, 60.4, 71.7, 72.3, 80.5, 82.3, 109.9,
117.8, 132.6, 132.7, 140.0, 148.5, 152.5, 169.3, 1708, 171.0;
HRFABMS m/z 1267.0624, calcd for C41H6379Br2I2N6O10Si2
(MþþH) 1267.0600.
was stirred for 30 min. Work-up and purification by
preparative TLC (1/2 hexane/EtOAc) gave a methyl ester
(19.6 mg, 65%): [a]2D0 223.9 (c 1.00, CHCl3); IR (film)
3334, 1725, 1650, 1506, 1367, 1228, 1164 cm21; dH 1.43
(18H, complex), 1.50 (9H, s), 2.56 (1H, t, J¼12 Hz), 2.83
(1H, dd, J¼2, 14.4 Hz), 3.04 (1H, dd, J¼6, 14 Hz), 3.26
(1H, m), 3.38 (1H, dd, J¼3.6, 12.8 Hz), 3.62 (1H, d, J¼
9.2 Hz), 3.80 (3H, s), 4.42 (1H, m), 4.62 (1H, d, J¼8.8 Hz),
4.90 (1H, m), 5.10 (1H, d, J¼8.4 Hz), 5.78 (1H, s), 5.89
(1H, d, J¼2 Hz), 6.55 (1H, dd, J¼2, 8 Hz), 6.66 (1H, d,
J¼9.2 Hz), 6.85 (1H, d, J¼8.0 Hz), 6.86 (1H, dd, J¼2.4,
8.4 Hz), 6.90 (1H, d, J¼8.4 Hz), 7.08 (2H, complex), 7.36
(1H, s), 7.40 (1H, dd, J¼2, 8.0 Hz), 8.61 (1H, m), 11.4 (1H,
s); dC 28.1, 28.2, 28.4, 37.4, 39.7, 43.3, 52.7, 53.3, 53.7,
53.8, 70.9, 71.1, 77.2, 79.6, 83.7, 114.6, 114.8, 121.5, 123.0,
124.1, 126.7, 128.2, 131.0, 132.0, 133.5, 144.2, 147.2,
152.7, 153.2, 155.1, 157.5, 162.1, 168.1, 171.0, 171.3;
HRFABMS m/z 845.3948, calcd for C40H57N6O14 (MþþH)
845.3933.
4.3.9. Cyclic tripeptide 25. A mixture of 24 (149.5 mg,
0.12 mmol) and TTN (210 mg, 0.47 mmol) in THF
(40 mL)–MeOH (10 mL) was stirred at 0 8C for 1 h.
Work-up and purification by silica-gel column chroma-
tography (4/1 hexane/EtOAc) gave 25 as an oil (85 mg,
63%): [a]2D0 þ38.7 (c 1.00, CHCl3); IR (film) 2103, 1681,
1486, 1255 cm21; dH 20.04 (3H, s), 0.08 (3H, s), 0.18 (3H,
s), 0.37 (3H, s), 0.90 (9H, s), 1.00 (9H, s), 1.50 (9H, s), 2.41
(1H, t, J¼12.8 Hz), 2.67 (1H, d, J¼12.8 Hz), 3.23–3.40
(3H, complex), 3.53 (1H, dd, J¼3.2, 12.8 Hz), 3.86 (3H, s),
3.91 (1H, m), 3.98 (1H, dd, J¼3.2, 7.6 Hz), 4.27 (1H, m),
4.53 (1H, dd, J¼2.8, 8.8 Hz), 4.92 (1H, m), 5.41 (1H, d,
J¼6.8 Hz), 5.87 (1H, d, J¼1.6 Hz), 6.12 (1H, s), 6.18 (1H,
d, J¼8.8 Hz), 7.05 (1H, d, J¼1.6 Hz), 7.19 (1H, d, J¼2 Hz),
7.63 (1H, d, J¼2 Hz); dC 25.3, 25.1, 25.0, 24.3, 23.3,
17.9, 18.0, 25.8, 26.2, 28.4, 36.7, 39.6, 52.8, 53.8, 72.5,
73.2, 79.5, 82.2, 114.0, 116.9, 117.3, 118.9, 128.2, 128.9,
133.9, 134.2, 134.3, 136.7, 142.6, 143.9, 147.0, 154.6,
167.5, 168.1, 170.9; HRFABMS m/z 1141.1490, calcd for
To a solution of the protected 1 (19.6 mg, 0.023 mmol) in
MeOH (0.3 mL) was added 1 M NaOH aq. (0.3 mL) at 0 8C.
After being stirred for 30 min, the reaction was quenched
by the addition of Amberlite IR 120B (Hþ) and stirred for
15 min. The mixture was filtered, and the filtrate was
evaporated. The residue was diluted with CH2Cl2 (0.5 mL),
and TFA (0.5 mL) was added to the mixture at 0 8C. After
being stirred for 2 h, the mixture was treated with essentially
the same procedure as in the case of 2 to give (3S,4R)-1 as
an oil (15 mg, quant): [a]2D0 217.8 (c 0.23, MeOH); IR
(film) 3280, 1670, 15081438, 1203 cm21; dC (CD3OD)
36.9, 39.7, 45.8, 53.9, 55.1, 55.4, 71.4, 74.2, 116.6, 117.1,
122.6, 123.5, 124.5, 124.9, 131.9, 133.0, 135.8, 147.2,
149.7, 154.7, 159.6, 169.3, 170.4, 174.8; HRFABMS m/z
531.2178, calcd for C24H31N6O8 (MþþH) 531.2203.
79
C41H62 Br81BrIN6O10Si2 (MþþH) 1141.1457.
4.3.10. Cyclic tripeptide 27. A mixture of 25 (73.2 mg,
0.064 mmol) and Ph3P (52.5 mg, 0.2 mmol) in THF
(0.7 mL)–H2O (0.05 mL) was heated at 60 8C for 2 h.
After evaporation, the residue was passed through silica-gel
short column chromatography (2/1 hexane/CHCl3). A
mixture of the product, 26 (27.4 mg, 0.096 mmol) HgCl2
(20.6 mg, 0.08 mmol), and Et3N (0.03 mL, 0.21 mmol) in
DMF (0.6 mL) was stirred at 0 8C for 1 h. Work-up and
purification by silica-gel column chromatography (5/1
hexane/EtOAc) gave 27 as an oil (51.4 mg, 60%): dH
0.01–0.35 (12H, complex), 0.91 (9H,s), 1.03 (9H, s), 1.45
(27H, complex), 2.41 (1H, t, J¼12.8 Hz), 2.66 (1H, d,
J¼14.0 Hz), 3.38 (4H, complex), 3.80 (1H, m), 3.83 (3H, s),
4.00 (1H, m), 4.23 (1H, m), 4.52 (1H, m), 4.93 (1H, m), 5.43
(1H, m), 5.92 (1H, s), 6.12 (1H, broad), 6.25 (1H, d,
J¼8.8 Hz), 7.03 (1H, s), 7.19 (1H, s), 7.53 (1H, m), 7.62
(1H, s), 8.55 (1H, d, J¼7.0 Hz), 11.30 (1H, broad); dC 25.7,
25.3, 24.1, 24.0, 17.9, 25.8, 25.9, 26.1, 28.0, 28.3, 28.4,
28.5, 36.2, 39.7, 42.8, 52.8, 52.9, 53.8, 72.3, 72.6, 77.2,
79.0, 79.2, 82.1, 83.3, 113.9, 116.8, 118.8, 128.2, 128.9,
134.0, 134.2, 136.9, 142.6, 143.8, 146.9, 152.8, 154.4,
156.1, 163.2, 168.0, 170.6; HRFABMS m/z 1355.2855,
4.4. Synthesis of (300R,400S)-eurypamide A 47
4.4.1. 4-Azido-4-deoxy-2,3,5-tri-O-benzyl-1-O-tert-butyl-
dimethylsilyl-D-ribitol 29. A mixture of 28 (6.14 g,
11 mmol), Ph3P (4.48 g, 17 mmol), DPPA (3.5 mL,
17 mmol), and DEAD (7.5 mL, 17 mmol) in THF (80 mL)
was stirred at ambient temperature for 2 h. Evaporation and
purification by silica-gel column chromatography (15/1
hexane/EtOAc) gave 29 as an oil (5.9 g, 92%): IR (film)
2096, 1455, 1255 cm21; dH 0.05 (6H, s), 0.90 (9H, s), 3.67
(3H, complex), 3.76 (1H, dd, J¼5.2, 10.8 Hz), 3.89 (1H, dd,
J¼4, 10.8 Hz), 3.97 (1H, m), 4.47 (1H, d, J¼12 Hz), 4.50
(1H, d, J¼12 Hz), 4.53 (1H, d, J¼12 Hz), 4.63 (2H, s),
4.70 (1H, d, J¼12 Hz), 7.35 (15H, complex); dC 25.2,
18.4, 26.0, 62.1, 62.3, 70.0, 72.4, 73.2, 73.9, 78.2, 79.4,
127.5, 127.6, 127.7, 127.9, 128.2, 137.8, 137.9, 138.1;
HREIMS m/z 562.3121, calcd for C32H43N3O4Si (MþþH)
562.3101.
79
calcd for C52H82 Br2IN6O14Si2 (MþþH) 1355.2839.
4.4.2. 4-(N-tert-Butoxycarbonyl)amino-4-deoxy-2,3,5-
tri-O-benzyl-1-O-tert-butyldimethylsilyl-D-ribitol 30. A
mixture of 29 (1.91 g, 3.4 mmol) and Ph3P (2.72 g,
10.2 mmol) in THF (30 mL)–H2O (3 mL) was heated at
60 8C for 2 h. After evaporation, the residue was dissolved
in H2O (10 mL)–1,4-dioxane (30 mL), NaHCO3 (0.87 g,
10.2 mmol) and Boc2O (1.2 mL, 5.1 mmol) were added at
0 8C. After being stirred for 1 h, the mixture was partitioned
4.3.11. Proposed eurypamide A 1. A solution of 27
(49 mg, 0.036 mmol) in MeOH (0.5 mL) containing cata-
lytic amounts of 10% Pd/C and NaOAc (8.8 mg,
0.11 mmol) was stirred at ambient temperature overnight
in a hydrogen atmosphere. The reaction mixture was filtered
through a Celite pad, and evaporated. A mixture of the
residue and TBAF (1 M in THF, 0.18 mL) in THF (0.6 mL)

5632
M. Ito et al. / Tetrahedron 60 (2004) 5623–5634
between EtOAc and H2O. The organic layer was washed
with brine, dried (Na2SO4), and evaporated. The residue
was purified by silica-gel column chromatography (50/1–
10/1 hexane/EtOAc) to give 30 as an oil (1.99 g, 92%): [a]D20
þ3.4 (c 1.00, CHCl3); IR (film) 3444, 1716, 1496, 1454,
1365, 1251, 1170 cm21; dH 0.09 (3H, s), 0.10 (3H, s), 0.94
(9H, s), 1.46 (9H, s), 3.54 (1H, d, J¼4.4, 9.2 Hz), 3.70 (2H,
complex), 3.85 (2H, complex), 4.00 (1H, m), 4.11 (1H, s),
4.47 (2H, complex), 4.61 (2H, complex), 4.77 (2H, com-
plex), 5.04 (1H, d, J¼8.8 Hz), 7.27–7.39 (15H, complex);
dC 25.3, 18.3, 26.0, 28.4, 50.8, 62.7, 69.3, 72.4, 72.9, 73.5,
78.3, 79.0, 80.5, 100.4, 127.3, 127.4, 127.5, 127.6, 127.8,
128.1, 128.2, 138.1, 138.4, 138.6, 155.3; HREIMS m/z
635.3735, calcd for C37H53NO6Si (Mþ) 635.3642.
HREIMS m/z 594.4051, calcd for C28H64NO6Si3 (MþþH)
594.4041.
4.4.6. Oxazolidinone 35. To a solution of 34 (0.84 g,
1.4 mmol) in THF (15 mL) was added NaH (111 mg, 60%
dispersion in mineral oil, 2.8 mmol) at 0 8C; the mixture
was stirred overnight. The reaction was quenched by the
addition of saturated NH4Cl aq., and extracted with EtOAc.
The organic layer was washed with brine, dried (Na2SO4),
and evaporated. A mixture of the residue, Et3N (0.6 mL,
4.2 mmol), DMAP (catalytic amount), and Boc2O (0.5 mL,
2.1 mmol) in THF (10 mL) was stirred for 1 h. Work-up and
purification by silica-gel column chromatography (8/1
hexane/EtOAc) gave 35 as an oil (0.75 g, 86%): [a]D20
þ36.5 (c 1.00, CHCl3); IR (film) 1797, 1720 cm21; dH 0.09
(18H, complex), 0.03 (3H, s), 0.90 (9H, s), 0.09 (3H, s), 0.10
(3H, s), 0.87 (9H, s), 0.90 (18H, s), 1.53 (9H, s), 3.45 (1H,
dd, J¼4.8, 10.4 Hz), 3.53 (1H, t, J¼10.4 Hz), 3.71 (1H, dd,
J¼4.0, 8.4 Hz), 4.15 (1H, t, J¼8.8 Hz), 4.35 (1H, s), 4.45
(1H, dd, J¼4.0, 9.2 Hz), 4.65 (1H, dd, J¼4.0, 8.4 Hz); dC
25.33, 25.31, 25.1, 24.8, 24.3, 24.2, 17.8, 18.0, 18.3,
25.9, 26.0, 27.4, 28.0, 55.7, 62.8, 64.1, 71.4, 77.9, 83.5,
85.2, 149.5, 152.5; HREIMS m/z 620.3794, calcd for
C29H62NO7Si3 (MþþH) 620.3834.
4.4.3. 4-(N-tert-Butoxycarbonyl)amino-4-deoxy-1-O-tert-
butyldimethylsilyl-5-O-pivaloyl-D-ribitol 32. A solution
of 30 (2.18 g, 3.4 mmol) in EtOH (40 mL) containing
catalytic amounts of 10% Pd/C was stirred for 30 min at
ambient temperature in a hydrogen atmosphere. The
reaction mixture was passed through a Celite pad, and
evaporated. A mixture of crude 31 and pivaloyl chloride
(0.5 mL, 3.83 mmol) in pyridine (15 mL) was stirred at
ambient temperature for 1 day. Work-up and purification by
silica-gel column chromatography (4/1–1/1 hexane/EtOAc)
gave 32 as an oil (1.02 g, 66%): [a]2D0 21.3 (c 1.00, CHCl3);
IR (film) 3384, 1716, 1508, 1253 cm21; dH 0.10 (6H, s),
0.90 (9H, s), 1.21 (9H, s), 1.43 (9H, s), 2.81 (1H, d,
J¼5.2 Hz), 3.50 (1H, d, J¼5.6 Hz), 3.68 (2H, complex),
3.85 (2H, complex), 4.02 (1H, m), 4.25 (1H, dd, J¼4,
11.2 Hz), 4.38 (1H, m), 4.93 (1H, d, J¼8.8 Hz); dC 25.4,
18.3, 25.9, 27.2, 28.4, 38.9, 52.4, 63.6, 64.6, 70.9, 73.7,
79.9, 156.0, 178.5; HREIMS m/z 450.2903, calcd for
C21H44NO7Si (MþþH) 450.2896.
4.4.7. Alcohol 36. To a solution of 35 (377.4 mg,
0.61 mmol) in MeOH (5 mL) was added catalytic amounts
of CSA at 0 8C; the mixture was stirred for 3 h. Work-up and
purification by silica-gel column chromatography (4/1
hexane/EtOAc) gave 36 as an oil (206 mg, 67%): [a]D20
þ58.9 (c 1.00, CHCl3); IR (film) 3502, 1808, 1720, 1654,
1471, 1384, 1371, 1255 cm21; dH 0.04 (3H, s), 0.09 (6H, s),
0.11 (3H, s), 0.89 (9H, s), 0.90 (9H, s), 1.55 (9H, s), 2.21
(1H, dd, J¼5, 8 Hz), 3.61 (2H, complex), 3.74 (1H, m), 4.18
(1H, t, J¼12 Hz), 4.34 (1H, d, J¼3.6 Hz), 4.63 (2H,
complex); dC 25.0, 24.7, 24.4, 24.3, 17.9, 18.0, 25.8,
28.0, 55.6, 62.2, 63.7, 70.9, 76.0, 84.2, 150.1, 152.0;
HREIMS m/z 506.2983, calcd for C23H48NO7Si2 (MþþH)
506.2969.
4.4.4. 4-(N-tert-Butoxycarbonyl)amino-4-deoxy-1,2,3-
tri-O-tert-butyldimethylsilyl-5-O-pivaloyl-D-ribitol 33.
To a solution of 32 (0.82 g, 1.8 mmol) in CH2Cl2 (15 mL)
was added 2,6-lutidine (1.3 mL, 11 mmol) and TBDMSOTf
(1.1 mL, 5.5 mmol) at 0 8C; the mixture was stirred at 0 8C
for 1 h. Work-up and purification by silica-gel column
chromatography (10/1 hexane/EtOAc) gave 33 as an oil
(1.1 g, 89%): [a]2D0 þ6.1 (c 1.0, CHCl3); IR (film) 3376,
1722, 1654, 1500, 1463, 1386, 1365, 1255, 1151 cm21; dH
0.10 (18H, complex), 0.90 (27H, complex), 1.19 (9H, s),
1.41 (9H, s), 3.47 (1H, m), 3.73 (2H, complex), 3.92 (1H,
d, J¼6.8 Hz), 4.09 (1H, m), 4.21 (2H, m), 5.11 (1H, d,
J¼12 Hz); HREIMS m/z 678.4587, calcd for C33H72NO7Si3
(MþþH) 678.4616. Found: C, 58.60; H, 10.38; N, 2.02.
Calcd for C33H71NO7Si3: C58.44; H, 10.55; N, 2.07.
4.4.8. Azide 37. To a solution of 36 (309 mg, 0.61 mmol) in
pyridine (4 mL) was added MsCl (0.1 mL, 1.3 mmol) at
0 8C. After being stirred for 2 h at the same temperature, the
mixture was partitioned between EtOAc and H2O. The
organic layer was washed with 5% KHSO4 aq. and brine,
dried (Na2SO4), and evaporated. A mixture of the residue
and NaN3 (330 mg, 5.7 mmol) in DMF (1.0 mL) was heated
at 70 8C overnight. Work-up and purification by silica-gel
column chromatography (6/1 hexane/EtOAc) gave 37 as an
oil (254 mg, 80%): [a]D20 þ29.0 (c 0.50, CHCl3); IR (film)
2103, 1818, 1718, 1654, 1461, 1371, 1326, 1257, 1159,
1093 cm21; dH 0.05 (3H, s), 0.09 (3H, s), 0.11 (3H, s), 0.13
(3H, s), 0.90 (18H, s), 1.55 (9H, s), 3.28 (1H, dd, J¼4.4,
8.8 Hz), 3.41 (1H, dd, J¼6.8, 12.8 Hz), 3.72 (1H, m), 4.18
(1H, t, J¼8.8 Hz), 4.23 (1H, d, J¼2.4 Hz), 4.51 (1H, dd,
J¼4.4, 8.8 Hz), 4.59 (1H, dd, J¼4.4, 8.8 Hz); d C 25.0,
24.5, 24.4, 24.3, 18.0, 25.8, 28.0, 49.9, 53.6, 55.7, 62.1,
71.4, 75.0, 84.0, 149.3; HREIMS m/z 531.3054, calcd for
C23H47N4O6Si2 (MþþH) 531.3034.
4.4.5. 4-(N-tert-butoxycarbonyl)amino-4-deoxy-1,2,3-tri-
O-tert-butyldimethylsilyl-D-ribitol 34. A mixture of 33
(1.13 g, 1.7 mmol) DIBAL-H (5 mL, 1 M in toluene) in
CH2Cl2 (10 mL) was stirred for 2 h at 278 8C. Work-up and
purification by silica-gel column chromatography (10/1–4/
1 hexane/EtOAc) to give 34 as an oil (0.91 g, 92%): [a]D20
þ6.2 (c 1.00, CHCl3); IR (film) 3406, 1698 cm21; dH 0.08
(18H, complex), 0.89, (9H, s), 0.90, (9H, s), 0.91 (9H, s),
1.43 (9H, s), 3.01 (1H, m), 3.48 (1H, m), 3.65 (2H,
complex), 3.80 (2H, complex), 3.98 (1H, m), 4.05 (1H, s),
5.47 (1H, d, J¼7.6 Hz); dC 25.3, 25.0, 24.6, 24.4, 23.9,
18.2, 18.4, 26.0, 28.4, 53.4, 63.8, 64.3, 75.4, 79.1, 155.2;
4.4.9. Primary alcohol 38. To a solution of 37 (254 mg,
0.48 mmol) in MeOH (4 mL) was added Cs2CO3 (catalytic
amount) at 0 8C; the mixture was stirred for 6 h. Work-up

M. Ito et al. / Tetrahedron 60 (2004) 5623–5634
5633
and purification by silica-gel column chromatography (5/1–
2/1 hexane/EtOAc) gave 38 as an oil (204 mg, 85%): [a]D20
þ1.6 (c 1.00, CHCl3); IR (film) 3382, 2102, 1652, 1457,
1257, 1056 cm21; dH 0.12 (6H, s), 0.14 (3H, s), 0.15 (3H, s),
0.90 (9H, s), 0.92 (9H, s), 1.44 (9H, s), 2.47 (1H, m), 3.29
(1H, dd, J¼6.8, 12.8 Hz), 3.54 (1H, dd, J¼3.2, 12.8 Hz),
3.65 (2H, complex), 3.84 (1H, m), 3.90 (1H, m), 4.02 (1H,
m), 5.18 (1H, d, J¼8.0 Hz); dC 25.1, 24.4, 23.9, 18.1,
18.3, 25.9, 26.0, 28.4, 52.6, 53.7, 62.4, 73.9, 76.4, 79.6,
155.4; HREIMS m/z 505.3230, calcd for C22H49N4O5Si2
(MþþH) 505.3241.
3.71 (3H, s), 3.74 (2H, complex), 4.25 (1H, m), 4.67 (2H,
complex), 7.34 (2H, s), 7.63 (2H, s); dC (CD3OD) 28.5,
28.7, 36.9, 52.9, 54.9, 55.0, 55.9, 57.1, 72.4, 73.7, 80.9,
85.1, 85.2, 112.0, 131.9, 134.1, 134.6, 141.3, 141.4, 151.1,
157.6, 170.9, 172.3, 173.4; HRFABMS m/z 1038.8856,
calcd for C29H3579Br2I2N6O10 (MþþH) 1038.8871.
4.4.13. Tripeptide 43. To a solution of 41 (30 mg,
0.03 mmol) in CH2Cl2 (3 mL) were added 2,6-lutidine
(0.10 mL, 0.86 mmol) and TBDMSOTf (0.07 mL,
0.31 mmol) at 0 8C; the mixture was stirred at 0 8C for
1 h. The reaction was quenched by the addition of 5%
KHSO4 aq., and extracted with EtOAc. The organic layer
was washed with brine, dried (Na2SO4), and evaporated. A
mixture of the residue and K2CO3 in MeOH (2 mL) was
stirred for 2 h. Work-up and purification by silica-gel
column chromatography (4/1 hexane/EtOAc) gave 43 as an
oil (21.8 mg, 60%): [a]D20 þ6.8 (c 1.00, CHCl3); IR (film)
3363, 2103, 1662, 1475, 1251, 1160 cm21; dH 0.09 (12H,
complex), 0.82 (9H, s), 0.92 (9H, s), 1.44 (9H, s), 2.80 (1H,
m), 2.91 (1H, dd, J¼6.4, 13.2 Hz), 3.05 (2H, complex), 3.27
(1H, dd, J¼6.8, 13.2 Hz), 3.54 (1H, dd, J¼5.2, 12 Hz), 3.71
(3H, s), 3.74 (1H, m), 3.79 (1H, m), 4.06 (1H, broad d,
J¼4.4 Hz), 4.28 (1H, m), 4.56 (1H, dd, J¼6.8, 8.4 Hz), 4.69
(1H, m), 4.84 (1H, d, J¼7.2 Hz), 5.68 (1H, s), 5.87 (1H, s),
6.76 (1H, d, J¼8.0 Hz), 7.02 (1H, d, J¼8.0 Hz), 7.23
(2H, s), 7.53 (2H, s); dC 25.0, 24.6, 24.2, 24.1, 18.1,
18.2, 25.8, 26.0, 28.3, 36.9, 52.6, 52.8, 55.9, 73.0, 75.3,
80.8, 82.4, 109.9, 130.6, 132.6, 139.7, 139.8, 148.4, 152.6,
168.5, 170.5, 170.7; HRFABMS m/z 1266.0578, calcd for
4.4.10. Amino acid 39. To a solution of 38 (204 mg,
0.4 mmol) in acetone (2 mL) and 5% NaHCO3 aq. (1.5 mL)
were added TEMPO (catalytic amount), KBr (111.1 mg,
0.93 mmol), and 8% NaClO aq. (1 mL, 1.6 mmol). After
being stirred for 4 h, Work-up and purification by silica-gel
column chromatography (2/1 hexane/EtOAc–10/1 CHCl3/
MeOH) gave 39 as an oil (177.4 mg, 85%): [a]2D0 þ1.0
(c 1.00, MeOH); IR (film) 2102, 1716, 1384, 1367,
1255 cm21; dH (CD3OD) 0.12 (3H, s), 0.15 (3H, s), 0.17
(3H, s), 0.18 (3H, s), 0.88 (9H, s), 0.95 (9H, s), 1.45 (9H, s),
3.55 (1H, dd, J¼2.8, 13.2 Hz), 3.98 (1H, m), 4.05 (1H, m),
4.32 (1H, m), 6.59 (1H, dd, J¼8.8 Hz); dC (CD3OD) 24.8,
24.2, 24.1, 23.8, 19.1, 26.5, 26.6, 28.7, 54.6, 57.7, 74.3,
61.5, 77.4, 80.7, 157.0, 172.9; HRFABMS m/z 519.3066,
calcd for C22H47N4O6Si2 (MþþH) 519.3034.
4.4.11. Dipeptide 40. A mixture of 39 (52.9 mg, 0.1 mmol),
10 (71.8 mg, 0.16 mmol), BOP reagent (66.5 mg,
0.16 mmol), and Et3N (0.05 mL, 0.34 mmol) in DMF
(1.5 mL) was stirred overnight. Work-up and purification
by silica-gel column chromatography (8/1 hexane/EtOAc)
gave 40 as an oil (70.4 mg, 81%): [a]2D0 þ12.2 (c 1.00,
CHCl3); dH 0.06 (3H, s), 0.12 (3H, s), 0.13 (3H, s), 0.16 (3H,
s), 0.84 (9H, s), 0.93 (9H, s), 1.46 (9H, s), 2.99 (2H,
complex), 3.17 (1H, dd, J¼7.2, 12 Hz), 3.44 (1H, dd, J¼4,
12 Hz), 3.71 (3H, s), 3.86 (1H, m), 4.12 (1H, broad d,
J¼6.4 Hz), 4.23 (1H, t, J¼7 Hz), 4.72 (1H, dd, J¼6.4,
14 Hz), 5.68 (1H, d, J¼8 Hz), 5.85 (1H, s), 6.81 (1H, d,
J¼7.2 Hz), 7.23 (2H, s); dC 25.3, 24.7, 24.4, 24.1,
18.1, 25.6, 25.8, 25.9, 26.0, 28.3, 29.7, 37.0, 52.5,
53.3, 53.4, 58.0, 70.4, 74.6, 83.9, 109.8, 130.4, 132.5,
148.5, 169.7, 170.8; HRFABMS m/z 854.2011, calcd for
79
C41H63 Br2I2N6O10Si2 (MþþH) 1266.0600.
4.4.14. TTN oxidation of 41. A mixture of 41 (11 mg,
0.01 mmol) and TTN (30 mg, 0.06 mmol) in MeOH
(1 mL)–THF (4 mL) was stirred at 0 8C for 4 h. Work-up
and purification by preparative TLC (1/3 hexane/EtOAc)
gave 44 as an oil (3.4 mg, 33%); dH 1.41 (9H, s), 1.98 (1H,
broad d, J¼14 Hz), 2.20 (1H, m), 2.59 (1H, t, J¼12 Hz),
3.24 (3H, s), 3.85 (3H, s), 5.25 (1H, broad s), 7.34 (1H,
broad s), 7.41 (1H, d, J¼2 Hz), 7.53 (1H, broad s).
4.4.15. TTN oxidation of 42. A mixture of 41 (12.2 mg,
0.01 mmol) and 2,2-dimethoxypropane (0.1 mL) in DMF
(0.5 mL) in the presence of catalytic amounts of TsOH was
heated at 65 8C for 3.5 h: work-up gave 42 (6 mg, 47%). A
mixture of 42 (7.8 mg, 0.007 mmol) and TTN (30 mg,
0.06 mmol) in MeOH (1 mL)–THF (4 mL) was stirred at
0 8C for 1 h. Work-up and purification by preparative TLC
(20/1 CHCl3/MeOH) gave 45 as an oil (1.8 mg, 25%); dH
1.40 (3H, s), 1.44 (9H, s), 1.66 (3H, s), 3.24 (3H, s), 3.84
(3H, s), 5.19 (1H, d, J¼2.8 Hz), 6.42 (1H, d, J¼10 Hz), 7.32
(1H, d, J¼2 Hz), 7.40 (1H, d, J¼2.8 Hz), 7.57 (1H, d, J¼
2 Hz).
79
C32H56 Br81BrN5O8Si2 (MþþH) 854.2014.
4.4.12. Tripeptide 41. To a solution of 40 (106.8 mg,
0.13 mmol) in THF (1.5 mL) was added TBAF (1 M in
THF, 0.5 mL) at 0 8C; the mixture was stirred for 30 min.
The reaction mixture was partitioned between EtOAc and
H2O. The organic layer was washed with brine, dried
(Na2SO4), and evaporated. A mixture of the residue and
TFA (0.8 mL) in CH2Cl2 (0.8 mL), was stirred at 0 8C for
30 min, and evaporated. A mixture of the residue, 13
(130.6 mg, 0.25 mmol), EDC (46.2 mg, 0.24 mmol), HOBt
(32.9 mg, 0.24 mmol) and Et3N (0.08 mL, 0.61 mmol) in
DMF (1.5 mL) was stirred overnight. Work-up and
purification by silica-gel column chromatography (20/1
hexane/EtOAc) gave 41 as an oil (109.4 mg, 85%): [a]D20
þ0.4 (c 1.00, MeOH); IR (film) 3332, 2100, 1637, 1457,
1245, 1159 cm21; dH (CD3OD) 1.39 (9H, s), 2.65 (1H, dd,
J¼8.4, 14 Hz), 2.85–2.98 (2H, complex), 3.04 (1H, dd,
J¼6.0, 14 Hz), 3.35 (1H, dd, J¼6.0, 13.2 Hz), 3.50 (1H, m),
4.4.16. Cyclic tripeptide 46. To a solution of 43 (57.9 mg,
0.046 mmol) in THF (20 mL) and MeOH (5 mL) was added
TTN (57.8 mg, 0.13 mmol) at 0 8C; the mixture was stirred
for 1 h. Work-up and purification by silica-gel column
chromatography (4/1 hexane/EtOAc) gave 46 as an oil
(29.0 mg, 56%): [a]2D0 þ2.8 (c 1.00, CHCl3); IR (film) 3374,
2103, 1671, 1455, 1255, 1106 cm21; dH 0.08 (6H,
complex), 0.24 (6H, complex), 0.82 (9H, s), 1.00 (9H, s),
1.49 (9H, s), 2.56 (1H, t, J¼12.8 Hz), 2.68 (1H, d,

5634
M. Ito et al. / Tetrahedron 60 (2004) 5623–5634
J¼12.8 Hz), 3.29 (2H, complex), 3.44 (1H, m), 3.80 (3H, s),
3.84 (2H, complex), 4.31 (1H, m), 4.56 (1H, d, J¼ 7.6 Hz),
4.99 (1H, m), 5.40 (1H, d, J¼6.4 Hz), 5.72 (1H, d,
J¼1.6 Hz), 6.05 (1H, s), 6.64 (1H, d, J¼7.2 Hz), 6.88
(1H, d, J¼10 Hz), 7.09 (1H, s), 7.26 (1H, overlapped with
solvent signal), 7.58 (1H, d, J¼2 Hz); dC 24.5, 24.4, 24.0,
23.5, 18.1, 18.4, 25.6, 26.2, 28.4, 28.5, 36.3, 38.6,
52.8, 52.9, 53.8, 75.1, 76.4, 79.6, 82.6, 113.5, 116.9,
118.7, 128.8, 133.6, 134.4, 134.6, 136.9, 143.9, 146.9,
154.8, 166.9, 167.9, 170.7; HRFABMS m/z 1139.1438,
J¼15 Hz), 3.34 (1H, dd, J¼6.8, 12.4 Hz), 3.44–3.48 (2H,
complex), 3.68 (1H, dd, J¼4.5, 8 Hz), 3.85 (1H, m), 4.12
(1H, d, J¼6 Hz), 4.70 (1H, d, J¼4.5 Hz), 4.74 (1H, dd, J¼3,
12 Hz), 5.95 (1H, d, J¼2 Hz), 6.67 (1H, dd, J¼2, 8 Hz),
6.84 (1H, d, J¼8 Hz), 6.88 (1H, dd, J¼2, 8 Hz), 7.03 (1H,
dd, J¼2, 8 Hz), 7.20 (1H, dd, J¼2, 8 Hz), 7.42 (1H, dd,
J¼2, 8 Hz); HRFABMS m/z 531.2180, calcd for
C24H31N6O8 (MþþH) 531.2203.
79
calcd for C41H62 Br2IN6O10Si2 (MþþH) 1139.1409.
Acknowledgements
4.4.17. (300R,400S)-Eurypamide A 47. To a solution of 46
(58.4 mg, 0.051 mmol) in THF (1 mL) and H2O (0.1 mL)
was added Ph3P (40.7 mg, 0.2 mmol) at ambient tempera-
ture; the mixture was heated at 60 8C for 2 h. After evapo-
ration, the residue was purified by silica-gel short column
chromatography (30/1 CHCl3/MeOH). A mixture of an
amine, 26 (30.7 mg, 0.11 mmol), Et3N (0.03 mL,
0.21 mmol), and HgCl2 (28.6 mg, 0.11 mmol) in DMF
(1 mL) was stirred at 0 8C for 1 h. The reaction mixture was
diluted with EtOAc and H2O, and filtered through a Celite
pad. The filtrate was extracted with EtOAc, washed with
brine, dried (Na2SO4), and evaporated. The residue was
dissolved in MeOH (0.5 mL), containing catalytic amounts
of 10% Pd/C and NaOAc (12.5 mg, 0.153 mmol), and the
mixture was stirred at ambient temperature overnight in a
hydrogen atmosphere. The reaction mixture was filtered
through a Celite pad, and evaporated. To the residue in THF
(0.6 mL) was added TBAF (1 M in THF, 0.18 mL) at 0 8C.
After being stirred for 30 min, the mixture was partitioned
between EtOAc and H2O, and the organic layer was washed
with brine. The organic layer was dried (Na2SO4), and
evaporated. The residue was purified by preparative TLC
(1/2 hexane/EtOAc) to give the corresponding methyl ester.
This work was supported by Grant-in-Aid for the 21st
Century COE program ‘KEIO Life Conjugate Chemistry’,
as well as Scientific Research C from the Ministry of
Education, Culture, Sports, Science, and Technology,
Japan.
References and notes
1. (a) Yamamura, S.; Nishiyama, S. Studies in Natural Products
Chemistry; Atta-ur-Rahman, Ed.; Elservier: Amsterdam, 1992;
Vol. 10, pp 629–669. (b) Yamamura, S.; Nishiyama, S. J. Synth.
Org. Chem. Jpn 1997, 55, 1029–1039.
2. An exception experienced was the case of K-13, in which the
ether linkage was obtained, not at the iodine part but at the
bromine position, probably owing to steric hindrance. See:
Nishiyama, S.; Suzuki, Y.; Yamamura, S. Tetrahedron Lett.
1989, 30, 379–382.
3. Reddy, M. V. R.; Harper, R. M.; Faulkner, D. J. Tetrahedron
1998, 54, 10649–10656.
4. Itokawa, H.; Watanabe, K.; Kawaoto, S.; Inoue, T. Jpn. Kokai
Tokkyo Koho JP 63203671; Chem. Abstr. 110, 213362w.
5. Part of this investigation was preliminary reported Ito, M.;
Yamanaka, M.; Kutsumura, N.; Nishiyama, S. Tetrahedron
Lett. 2003, 44, 7949–7952.
A mixture of the methyl ester (8.8 mg, 0.011 mmol) and
1 M NaOH aq. (0.3 mL) in MeOH (0.3 mL) was stirred at
0 8C for 30 min. After the addition of Amberlite IR 120B
(Hþ), the mixture was filtered. The filtrate was evaporated to
give a residue, which was treated at 0 8C with TFA (0.5 mL)
in CH2Cl2 (0.5 mL) for 2 h. Evaporation gave 47 as an oil
(4.0 mg, 82%): [a]2D0 220.5 (c 0.23, MeOH); IR (film) 3390,
1671, 1506, 1428, 1274, 1203 cm21; dH (CD3OD) 2.67 (1H,
t, J¼12.7 Hz), 2.96 (1H, dd, J¼6, 15 Hz), 3.20 (1H, d,
6. Nishiyama, S.; Kim, M. H.; Yamamura, S. Tetrahedron Lett.
1994, 35, 8397–8400.
7. Yamamoto, Y.; Kirihata, M.; Ichimoto, I.; Ueda, H. Agric. Biol.
Chem. 1985, 49, 1435–1439.
8. Naka, T.; Minakawa, N.; Abe, H.; Kaga, D.; Matsuda, A. J. Am.
Chem. Soc. 2000, 122, 7233–7243.