Highly Efficient Biomimetic Total Synthesis and Structural Verification of Bistratamides E and J from Lissoclinum bistratum

Article abstract of DOI:10.1002/chem.200305504

The interesting biological activities of heterocycle-containing cyclic peptide-derived natural products, isolated from marine organisms over the past twenty years, have attracted the interest of many synthetic and natural products chemists. Bistratamides

Full text of DOI:10.1002/chem.200305504

FULL PAPER
Highly Efficient Biomimetic Total Synthesis and Structural Verification of
Bistratamides E and J from Lissoclinum bistratum
Shu-Li You and JefferyW. Kelly*[a]
Abstract: The interesting biological ac-
tivities of heterocycle-containing cyclic
peptide-derived natural products, iso-
lated from marine organisms over the
past twenty years, have attracted the
interest of many synthetic and natural
products chemists. Bistratamides E J,
members of this class of natural prod-
ucts that were isolated very recently
from Lissoclinum bistratum, exhibited
we report the first total syntheses of
bistratamides E (1) and J (2) in overall
yields of 19 and 34%, respectively. The
thiazole substructures have been syn-
thesized by oxidation of their corre-
containing peptides using a novel bio-
mimetic approach wherein Val-Cys di-
peptide units were converted to thiazo-
lines by a bisphosphonium salt. The
final macrocyclization was promoted
efficiently using the combination of
PyBOP and DMAP. This approach
allows the use of readily available
Fmoc-protected amino acids to make
complex thiazole and oxazoline-con-
taining natural products.
sponding
thiazoline
substructures,
which were obtained from cysteine
Keywords: biomimetic synthesis
¥
bistratamides ¥ natural products ¥
thiazole ¥ total synthesis
cytotoxic activity against
a human
colon tumor (HCT-116) cell line. Here
Introduction
Numerous thiazole and/or thiazoline-containing natural
products have been isolated from marine organisms includ-
ing ascidians (sea squirts) over the past twenty years.[1] Their
cytotoxic activities as well as their metal binding capacity
has attracted the interest of several synthetic and natural
product chemists.[2] The thiazole oxazoline and thiazole con-
taining peptide-derived macrocycles, bistratamides E (1) and
J (2), respectively, were very recently isolated from Lissocli-
num bistratum in the southern Philippines (Scheme 1).[3]
They exhibited moderate cytotoxic activity against a human
colon tumor (HCT-116) cell line. The antimicrobial, antitu-
mor and the anti-drug resistance properties of members of
this family of natural products warrant the synthetic efforts
published thus far to prepare natural products related to bis-
Scheme 1. Retrosynthetic analysis for 1 and 2.
intermediates,[7] 2) a condensation reaction between cysteine
tratamides E and J.[4
esters and N-protected imino esters,[8] and 3) the cyclodehy-
6]
Construction of the thiazoles in these peptide-derived
macrocycles is central to their total synthesis. Commonly
used methods for the preparation of thiazoles include 1) a
modification of Hantzsch×s procedure using thioamides as
dration of b-hydroxythioamides using either Mitsunobu con-
10]
ditions or the Burgess reagent.[9
Thiazolines synthesized
by the last two procedures are readily converted into thia-
zoles by oxidation. Recently, we reported that N-acylated
cysteine substructures when treated with bis(triphenyl) oxo-
diphosphonium trifluoromethanesulfonate afford thiazolines
efficiently.[11] In this approach, thiazolines are formed by a
nucleophilic attack of the cysteine thiol group on the phos-
phorus-activated amide carbonyl group of the preceding res-
idue, followed by dehydration via phosphine oxide forma-
tion. The reaction proceeds in high yield with excellent
chemo- and enantioselectivity without epimerization of the
[a]Dr. S.-L. You, Prof. Dr. J.W. Kelly
Department of Chemistry and
The Skaggs Institute for Chemical Biology
The Scripps Research Institute
La Jolla, CA 92037 (USA)
Fax : (+1)858-784-9899
E-mail: jkelly@scripps.edu
71
Chem. Eur. J. 2004, 10, 71 75
DOI: 10.1002/chem.200305504
¹ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

FULL PAPER
chiral center of the neighboring amino acid residue. Thia-
zole-containing peptides can be obtained by oxidation of the
resulting thiazolines employing activated MnO2. Here, we
report the total synthesis of bistratamides E and J in overall
yields of 19 and 34%, respectively.
donor compound 7a was prepared by removing the Fmoc
protecting group of 7 using diethylamine. Thiazoles 7a and
7b were coupled utilizing HBTU, HOBt and DIEA deliver-
ing tetrapeptide-derived bisheterocycle 8 in 91% yield.
N-Fmoc deprotection and coupling of 8 to N-Fmoc-O-
trityl-threonine afforded 9 (92%) which was Fmoc depro-
tected and coupled with N-Fmoc-l-valine to give 10 (93%),
Scheme 3. Macrocycle precursor 11 can be obtained from
hexapeptide 10 by removing the Fmoc and allyl groups as
described above affording reactive termini. Several methods
(DPPA,[14] FDPP,[15] PyBOP[16]) were evaluated to cyclode-
hydrate 11 affording 12. The combination of PyBOP and
DMAP gave the highest yield (93%), achieved by adding 11
[0.5 mmol in 30 mL CH2Cl2/DMF 2:1 v/v]into a solution of
PyBOP (1 mmol) and DMAP (1 mmol) in 120 mL CH2Cl2/
DMF (2:1 v/v) over 16 h with a syringe pump. The trityl
group was removed from the threonine residue in 12 by
treating the macrocycle with TFA (2%) in CH2Cl2 affording
bistratamide J (2), a colorless
Results and Discussion
A retrosynthetic analysis for the preparation of 1 and 2 de-
picts how both macrocycles can be synthesized from the
common bis-thiazole intermediate 3, derived from a tetra-
peptide prepared from ordinary Fmoc-protected amino
acids (Scheme 1).
The preparation of 8, a specific analogue of 3 with allyl
and Fmoc protecting groups on the C- and N-termini, com-
mences with protecting the carboxylic acid of N-Fmoc-S-
trityl-cysteine (4) as an allyl ester (Scheme 2). Fmoc depro-
solid. The 1H and 13C NMR
spectra were identical to those
reported by Perez and Faulk-
ner.[3] The structure of 2 was
also verified by X-ray crystal-
lography.[17]
The final steps of the syn-
thesis of bistratamide E (1) are
depicted in Scheme 4. Hexa-
peptide 14 was synthesized
from 8 after consecutive Fmoc
deprotections and couplings
with N-Fmoc-O-allo-threonine
and N-Fmoc-l-valine. Allo-
threonine was used to ensure
the correct stereochemistry in
a subsequent step because the
Scheme 2. Synthesis of tetrapeptide 8. a) HOBt, HBTU, DIEA, allyl alcohol, DMF; b) DEA, CH3CN;
c) HOBt, HBTU, DIEA, N-Fmoc-l-valine, DMF, 84%; d) Ph3PO, Tf2O, CH2Cl2, À208C, 89%; e) activated
MnO2, CH2Cl2, 94% (>96% ee); f) DEA, CH3CN; g) Pd(OAc)2, PS-triphenylphosphine, PhSiH3, CH2Cl2;
h) HOBt, HBTU, DIEA, DMF, 91% for f) h); DEA = N,N-diethylamine, DIEA = N,N-diisopropylethyl-
amide oxygen inverts the acti-
vated side chain upon nucleo-
philic attack in the preparation
of the oxazoline. Removal of
the Fmoc and allyl protecting
groups of 14 afforded the mac-
rocycle precursor 15 in quanti-
amine, DMF = N,N-dimethylformamide, HOBt = N-hydroxybenzo-
triazole, HBTU = 2-(1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluro-
nium hexafluorophosphate, PS-triphenylphosphine = polystyrene
triphenylphosphine.
tection allows the resulting amine to be coupled with an
active ester of N-Fmoc-l-valine to afford the fully protected
dipeptide 5 (84% for three steps). Bis(triphenyl)oxodiphos-
phonium trifluoromethanesulfonate[12] was utilized to con-
vert the trityl protected cysteine residue in 5 to a thiazoline
yielding 6 (89%). Thiazoline 6 was oxidized to a thiazole 7
employing activated manganese oxide (94%; >96% ee).
The bis-thiazole 8 was prepared by a coupling between 7a
and 7b, differentially protected thiazoles derived from 7.
The carboxylic acid compound 7b was obtained by remov-
ing the allyl protecting group of 7 using a solid phase palla-
dium catalyst (generated from Pd(OAc)2 and polymer-sup-
ported triphenylphosphine) in the presence of phenylsi-
lane.[13] The use of a solid phase catalyst greatly simplified
workup of the reaction, as the product could be separated
from the catalyst by filtration through silica gel. The amine
tative yield. Cyclodehydration of 15 to 16 was achieved in
81% yield by adding 15 [0.5 mmol in 30 mL CH2Cl2/DMF
2:1 v/v]into a solution of PyBOP (1 mmol) and DMAP
(1 mmol) in 120 mL CH2Cl2/DMF 2:1 (v/v) over 16 h with a
syringe pump. The Val-Thr substructure was then converted
to an oxazoline using the Burgess reagent, providing bistra-
tamide E (1) (63%). The 1H and 13C NMR of bistratamide E
(1) were identical to those reported by Perez and Faulk-
ner.[3]
In summary, bistratamides E and J have been synthesized
from cysteine containing peptides using a novel biomimetic
approach wherein Val-Cys dipeptide substructures are con-
verted to thiazolines by a bisphosphonium salt. This ap-
proach allows the use of readily available Fmoc-protected
amino acids to make complex natural products in high
yields with excellent regio and stereoselectivity.
72
¹ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Chem. Eur. J. 2004, 10, 71 75

Total Synthesis of Bistratamides
71 75
Synthesis of dipeptide 5: A solution of
Na-Fmoc-Cys(S-trityl)-OH
(5.86 g,
10 mmol) in DMF (50 mL) was treated
with HOBt¥H2O (1.68 g, 11 mmol) and
HBTU (4.17 g, 11 mmol) at 258C.
After 10 min, allyl alcohol (1.36 mL,
20 mmol) and DIEA (3.65 mL,
21 mmol) were added separately. The
resulting mixture was stirred at 258C
overnight. The reaction mixture was
concentrated and the residue was dis-
solved in EtOAc and washed with
10% aqueous NaHCO3. The organic
layer was dried over Na2SO4, filtered
and concentrated.
Diethylamine (30 mL) was added to a
solution of the above crude ester in
CH3CN (30 mL) and the resulting mix-
ture was stirred at 258C for 30 min to
ensure complete removal of the Fmoc
protecting group. After concentration
in vacuo, the reaction mixture was
azeotroped to dryness with CH3CN
(2î30 mL) and the residue was dis-
solved in DMF (40 mL). In another
Scheme 3. The later steps of the synthesis affording 2. a) DEA, CH3CN; b) HOBt, HBTU, DIEA, N-Fmoc-O-
trityl-l-threonine, DMF, 92%; c) HOBt, HBTU, DIEA, N-Fmoc-l-valine, DMF, 93%; d) Pd(OAc)2, PS-triphe-
nylphosphine, PhSiH3, CH2Cl2; e) PyBOP, DMAP, CH2Cl2, DMF, 93%; f) TFA, PhSH, CH2Cl2, 96%; PyBOP
= benzotriazole-1-yl-oxy-tris-pyrrolidino-phosphonium hexafluorophosphate, DMAP = 4-(N,N-dimethyl)pyri-
dine, TFA = trifluoroacetic acid (other reagents defined in Scheme 2).
flask,
a
solution of Na-Fmoc-valine
(3.73 g, 11 mmol) in DMF (40 mL)
was treated with HOBt¥H2O (1.68 g,
11 mmol)
and
HBTU
(4.17 g,
11 mmol). After 10 min, this mixture
and DIEA (3.65 mL, 21 mmol) were
sequentially added to the above free
amino ester. After stirring at 258C for
8 h. The reaction mixture was concen-
trated and the residue was dissolved in
EtOAc and washed with 10% aqueous
NaHCO3. The organic layer was dried
over Na2SO4, filtered and concentrat-
ed. The resulting crude product was
purified by flash chromatography using
a mixture of EtOAc/hexanes. Dipep-
tide 5 was obtained as a white foam
(6.09 g, 84%). [a]D24
= +4.4 (c=1.61
in CHCl3); 1H NMR (600 MHz,
CDCl3, 258C, TMS): d = 7.76 (d, J=
7.5 Hz, 2H), 7.59 (t, J=7.0 Hz, 2H),
7.39 (m, 8H), 7.31 7.24 (m, 9H), 7.19
(dd, J=7.5, 7.0 Hz, 2H), 6.06 (m, 1H),
5.86 (m, 1H), 5.40 (m, 1H), 5.30 (d,
J=16.6 Hz, 1H), 5.25 (d, J=10.5 Hz, 1
H), 4.61 4.56 (m, 3H), 4.44 (dd, J=
8.3, 7.2 Hz, 1H), 4.35 (dd, J=10.1,
7.0 Hz, 1H), 4.22 (t, J=7.0 Hz, 1H),
4.01 (m, 1H), 2.76 (dd, J=12.3, 6.6 Hz,
1H), 2.08 (dd, J=12.3, 3.1 Hz, 1H),
2.08 (m, 1H), 0.96 (d, J=6.1 Hz, 3H),
0.91 (d, J=6.6 Hz, 3H); 13C NMR
(150 MHz, CDCl3): d = 172.7, 169.7,
156.2, 144.1, 143.9, 143.8, 141.3, 131.3,
129.4, 128.0, 127.7, 127.0, 126.9, 125.1,
119.9 (2C), 118.9, 67.0, 66.3, 59.7, 51.2,
Scheme 4. The later steps of the synthesis affording 1. a) DEA, CH3CN; b) HOBt, HBTU, DIEA, N-Fmoc-
allo-threonine, DMF, 95%; c) HOBt, HBTU, DIEA, N-Fmoc-l-valine, DMF, 86%; d) Pd(OAc)2, PS-triphenyl-
phosphine, PhSiH3, CH2Cl2; e) PyBOP, DMAP, CH2Cl2, DMF, 81%; f) Burgess reagent, THF, reflux, 63%;
Burgess reagent=(methoxycarbonylsulfamoyl)triethylammonium hydroxide, inner salt (other reagents defined
in Schemes 2 and 3).
Experimental Section
47.2, 33.4, 31.6, 19.0, 17.5; HRMS (MALDI-FTMS): calcd for
C45H44NaN2O5S: 747.2863, found: 747.2886 [M+Na]+.
General: Unless stated otherwise, all reactions were carried out in flame-
dried glassware under a dry argon atmosphere. All solvents were pur-
chased from Fisher and were dried prior to use. 1H NMR spectra were
measured at 600 MHz on a Bruker DRX spectrometer, and were refer-
enced to internal TMS (0.0 ppm). 13C NMR spectra were performed at
150 MHz on a Bruker DRX-600 instrument and were referenced to
CDCl3. The chemical shift assignments for major diastereomers, not for
minor diastereomers, were reported. Flash chromatography was per-
formed on silica gel 60 (230 400 mesh, E. Merck no. 9385).
Synthesis of compound 6: Trifluoromethanesulfonic anhydride (2.35 mL,
15 mmol) was added slowly at 08C to a solution of triphenylphosphine
oxide (8.35 g, 30 mmol) in dry CH2Cl2 (100 mL). The reaction mixture
was stirred for 10 min at 08C and then adjusted to À208C using a brine-
ice bath. Then a solution of 5 (7.25 g, 10 mmol) in CH2Cl2 (10 mL) was
added. The reaction progress was monitored by TLC and completed in
2 h. The reaction mixture was quenched with 10% aqueous NaHCO3.
The aqueous layer was extracted with CH2Cl2 and the combined organic
73
Chem. Eur. J. 2004, 10, 71 75
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¹ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

J. W. Kelly and S.-L. You
FULL PAPER
layers were dried over Na2SO4, filtered and concentrated. The resulting
127.5, 127.2, 126.9 (2C), 125.0, 124.9, 123.8, 119.8 (2C), 118.7, 88.6, 69.8,
66.8, 65.8, 56.9, 56.5, 46.9, 32.9, 32.8, 19.6, 19.5, 18.0, 17.8, 16.4; HRMS
(MALDI-FTMS): calcd for C57H57NaN5O7S2: 1010.3591, found:
1010.3613 [M+Na]+.
crude product was purified by flash chromatography. Compound 6 was
obtained as a colorless oil (4.135 g, 89%). [a]D24
=
+11.8 (c=1.00 in
CHCl3); 1H NMR (600 MHz, CDCl3, 258C, TMS): d
=
7.76 (d, J=
7.5 Hz, 2H), 7.61 (dd, J=9.7, 8.3 Hz, 2H), 7.39 (t, J=7.5 Hz, 2H), 7.31
(t, J=7.5 Hz, 2H), 5.96 5.92 (m, 1H), 5.55 (d, J=9.2 Hz, 1H), 5.36 (t,
J=17.1 Hz, 1H), 5.28 (d, J=10.5 Hz, 1H), 5.17 (dd, J=8.8, 8.3 Hz, 1H),
4.70 (br, 2H), 4.57 (dd, J=9.2, 4.8 Hz, 1H), 4.43 4.37 (m, 2H), 4.24 (t,
J=7.0 Hz, 1H), 3.60 3.55 (m, 2H), 2.22 2.19 (m, 1H), 1.02 (d, J=7.0 Hz,
3H), 0.93 (d, J=7.0 Hz, 3H); 13C NMR (150 MHz, CDCl3): d = 175.5,
170.2, 156.1, 143.9, 143.7, 141.2, 131.4, 127.6, 127.0, 125.1, 119.9, 119.1,
77.4, 66.9, 66.2, 58.4, 47.2, 35.9, 32.3, 19.3, 16.6; HRMS (MALDI-FTMS):
calcd for C26H28N2O4S: 465.1842, found: 465.1858 [M+H]+.
Synthesis of compound 10: Deprotecting the Fmoc group in 9 and cou-
pling with Na-Fmoc-valine followed the procedure described in synthesis
of 5. Compound 10 was obtained in 93% yield as a white foam. [a]D24
=
1
À19.9 (c=1.55 in CHCl3); H NMR (600 MHz, CDCl3, 258C, TMS): d =
8.11 (s, 1H), 8.06 (s, 1H), 7.95 (d, J=9.2 Hz, 1H), 7.75 (d, J=7.5 Hz, 2
H), 7.57 7.51 (m, 8H), 7.38 (m, 2H), 7.29 7.26 (m, 10H), 7.23 (dd, J=
14.0, 6.6 Hz, 2H), 6.83 (m, 1H), 5.98 (m, 1H), 5.41 (d, J=8.3 Hz, 1H),
5.39 5.35 (m, 2H), 5.27 5.25 (m, 1H), 5.13 (dd, J=8.3, 6.6 Hz, 1H), 4.82
(d, J=5.7 Hz, 2H), 4.41 (dd, J=10.1, 6.6 Hz, 2H), 4.31 (dd, J=10.5,
7.0 Hz, 1H), 4.19 (m, 1H), 4.01 (m, 1H), 3.66 (m, 1H), 2.60 (m, 1H),
2.33 (m, 1H), 2.06 (m, 1H), 1.07 (d, J=6.1 Hz, 3H), 0.99 (d, J=6.6 Hz, 3
H), 0.98 (d, J=6.6 Hz, 3H), 0.90 (d, J=7.1 Hz, 3H), 0.89 (d, J=6.1 Hz, 3
H), 0.84 (d, J=6.6 Hz, 3H), 0.82 (d, J=6.6 Hz, 3H); 13C NMR
(150 MHz, CDCl3): d = 171.9, 171.7, 170.3, 169.4, 160.9, 160.8, 156.3,
149.2, 147.0, 143.7, 143.6, 141.2, 131.8, 128.9, 128.7, 127.6, 127.5, 127.2,
127.0, 125.0, 123.8, 119.9 (2C), 118.8, 88.5, 69.2, 67.0, 65.9, 57.0, 56.6, 55.9,
47.1, 32.9 (2C), 31.2, 19.6, 19.5, 18.0 (2C), 17.5, 16.9; HRMS (MALDI-
FTMS): calcd for C62H66NaN6O8S2: 1109.4276, found: 1109.4293
[M+Na]+.
Synthesis of compound 7: Activated MnO2 (<5 micron, 85%, 7.16 g,
70 mmol) was added to a solution of 7 (3.25 g, 7 mmol) in CH2Cl2
(35 mL). The reaction mixture was stirred overnight at 258C, then fil-
tered through a short silica gel and Celite column and washed with
EtOAc. The organic solution was concentrated. The resulting crude prod-
uct was purified by flash chromatography. Compound 7 was obtained as
a white solid (3.04 g, 94%). M.p. 104 1058C; [a]2D4 = À43.4 (c=0.58 in
1
CHCl3); H NMR (600 MHz, CDCl3, 258C, TMS): d = 8.10 (s, 1H), 7.76
(d, J=7.0 Hz, 2H), 7.59 (m, 2H), 7.39 (m, 2H), 7.30 (m, 2H), 6.03 (m, 1
H), 5.59 (d, J=8.8 Hz, 1H), 5.41 (t, J=17.1 Hz, 1H), 5.30 (d, J=10.1 Hz,
1H), 4.94 (dd, J=8.8, 6.1 Hz, 1H), 4.85 (d, J=5.3 Hz, 2H), 4.44 (m, 2H),
4.22 (m, 1H), 2.43 (m, 1H), 0.96 (d, J=6.6 Hz, 3H), 0.94 (d, J=7.0 Hz, 3
H); 13C NMR (150 MHz, CDCl3): d = 172.2, 160.8, 156.0, 147.0, 143.8,
143.7, 141.3, 131.8, 127.7, 127.2, 127.0, 125.0 (2C), 119.9, 118.9, 66.9, 65.9,
58.5, 47.2, 33.4, 19.4, 17.6; HRMS (MALDI-FTMS): calcd for
C26H26N2O4S: 463.1686, found: 465.1668 [M+H]+.
Synthesis of compound 12: Deprotecting the Fmoc group in 10 (544 mg,
0.5 mmol) followed the procedure described in synthesis of 5. The allyl
group was removed using a palladium catalyst as described in synthesis
of 8. The resulting amino acid 11 was dissolved in CH2Cl2/DMF (30 mL,
2:1 v/v). This solution was added into a flask containing PyBOP (520 mg,
1 mmol) and DMAP (122 mg, 1 mmol) in CH2Cl2/DMF (120 mL, 2:1 v/v)
over 16 h using a syringe pump. After the completion of addition, the
mixture was stirred for 4 h. Regular workup and purification by flash
chromatography gave 12 as a white foam (375 mg, 93%). [a]2D4 = À157.6
Synthesis of compound 8: Pd(OAc)2 (11.2 mg, 0.05 mmol) and PS-triphe-
nylphosphine (252 mg, 1.59 mmolgÀ1, 0.4 mmol, purchased from Argo-
naut Technologies) were added to a flask containing CH2Cl2 (20 mL).
After stirring for 10 min, 7 (1.155 g, 2.5 mmol) and PhSiH3 (0.61 mL,
5 mmol) were added separately. TLC showed that the starting material
disappeared in 15 min. After removing the solvent, the residue was
passed through a short silica gel column and eluted with CHCl3/EtOH
1:1. The carboxylic acid 7b was used in next step without further purifica-
tion.
1
(c=0.50 in CHCl3); H NMR (600 MHz, DMSO, 258C): d = 8.38 (d, J=
10.1 Hz, 1H), 8.34 (s, 1H), 8.28 (d, J=9.2 Hz, 1H), 8.25 (s, 1H), 8.17 (d,
J=10.5 Hz, 1H), 7.92 (d, J=9.6 Hz, 1H), 7.48 (d, J=7.9 Hz, 6H), 7.31
(dd, J=7.9, 7.5 Hz, 6H), 7.24 (dd, J=7.5, 7.0 Hz, 3H), 5.35 (dd, J=9.7,
7.0 Hz, 1H), 5.22 (dd, J=9.2, 8.8 Hz, 1H), 4.62 (dd, J=10.1, 3.1 Hz, 1H),
4.33 (t, J=11.0 Hz, 1H), 3.71 (m, 1H), 2.24 (m, 1H), 2.16 2.11 (m, 2H),
1.01 (d, J=6.6 Hz, 3H), 0.98 (d, J=6.6 Hz, 3H), 0.97 (d, J=4.8 Hz, 3H),
0.95 (d, J=6.1 Hz, 3H), 0.87 (d, J=7.0 Hz, 3H), 0.79 (d, J=6.6 Hz, 3H),
0.68 (d, J=6.6 Hz, 3H); 13C NMR (150 MHz, DMSO): d = 170.3, 169.8,
169.6, 167.7, 159.8, 159.5, 149.0, 148.0, 144.6, 128.5, 127.7, 127.0, 125.9,
124.3, 57.9, 55.4, 55.2, 34.4, 33.9, 30.3, 19.6, 19.5, 19.4, 18.9, 18.6, 17.9;
HRMS (MALDI-FTMS): calcd for C44H50NaN6O5S2: 829.3176, found:
829.3190 [M+Na]+.
In separate flask, the Fmoc group in 7 (1.063 g, 2.3 mmol) was removed
using diethylamine as described in the synthesis of 5. The resulting free
amine 7a was dissolved in DMF (10 mL), then, a solution of the above
free carboxylic acid, HOBt¥H2O (383 mg, 2.5 mmol), HBTU (948 mg,
2.5 mmol) and DIEA (0.92 mL, 5.3 mmol) in DMF (10 mL) was added.
The resulting mixture was stirred for 8 h. Regular workup and purifica-
tion with flash chromatography using a mixture of EtOAc/hexanes gave
8 as a white foam (1.35 g, 91%). [a]D24
=
À16.9 (c=0.45 in CHCl3);
Synthesis of bistratamide J (2): TFA (0.1 mL) and PhSH (21 mL,
0.2 mmol) were added to a flask containing 12 (161 mg, 0.2 mmol) in
CH2Cl2 (5 mL). TLC showed that 12 disappeared in 5 min. After remov-
ing all of the solvents, the residue was purified by flash chromatography.
Bistratamide J (2) was obtained as a colorless solid (108 mg, 96%). M.p.
165 1678C; [a]2D5 = À134.9 (c=0.50 in MeOH)[lit[3]: [a]D =À25.0 (c=0.5
1H NMR (600 MHz, CDCl3, 258C, TMS): d = 8.08 (s, 1H), 8.04 (s, 1H),
7.98 (d, J=8.8 Hz, 1H), 7.74 (d, J=7.0 Hz, 2H), 7.58 (dd, J=16.2,
7.0 Hz, 2H), 7.37 (m, 2H), 7.29 7.23 (m, 2H), 5.99 (m, 1H), 5.65 (m, 1
H), 5.36 (d, J=9.3 Hz, 1H), 5.33 (d, J=8.8 Hz, 1H), 5.25 (d, J=10.5 Hz,
1H), 4.93 (dd, J=8.3, 6.1 Hz, 1H), 4.79 (m, 2H), 4.47 (d, J=6.6 Hz, 2H),
4.23 (m, 1H), 2.62 (m, 1H), 2.40 (m, 1H), 1.04 (d, J=6.6 Hz, 3H), 1.00
(d, J=6.6 Hz, 6H), 0.95 (d, J=6.6 Hz, 3H); 13C NMR (150 MHz,
CDCl3): d = 172.1, 171.5, 160.7, 160.6, 156.0, 149.3, 146.9, 143.6 (2C),
141.2 (2C), 131.7, 127.6, 127.2, 127.0, 126.9, 124.9, 124.8, 123.5, 119.9,
118.7, 66.8, 65.8, 56.3, 47.1, 33.0 (2C), 19.6, 19.3, 18.0, 17.5; HRMS
(MALDI-FTMS): calcd for C34H36NaN4O5S2: 667.2019, found: 667.2046
[M+Na]+.
in MeOH)]; 1H NMR (600 MHz, DMSO, 258C):
d = 8.49 (d, J=
10.5 Hz, 1H), 8.43 (d, J=9.7 Hz, 1H), 8.30 (s, 1H), 8.24 (s, 1H), 8.13 (d,
J=9.7 Hz, 1H), 8.08 (d, J=10.1 Hz, 1H), 5.33 (dd, J=10.1, 7.4 Hz, 1H),
5.22 (t, J=4.8 Hz, 1H), 5.20 (dd, J=9.7, 9.2 Hz, 1H), 4.35 (t, J=11.0 Hz,
1H), 4.32 (dd, J=10.1, 2.0 Hz, 1H), 4.14 (m, 1H), 2.22 (m, 1H), 2.16
2.11 (m, 2H), 1.11 (d, J=6.6 Hz, 3H), 1.05 (d, J=6.1 Hz, 3H), 1.04 (d,
J=5.8 Hz, 3H), 1.03 (d, J=6.6 Hz, 3H), 0.99 (d, J=6.6 Hz, 3H), 0.91 (d,
J=6.6 Hz, 3H), 0.81 (d, J=6.6 Hz, 3H); 13C NMR (150 MHz, DMSO): d
= 170.1 (2C), 169.4 (2C), 159.9, 159.7, 149.0, 148.3, 125.4, 124.2, 67.7,
61.3, 58.8, 55.4, 55.0, 34.7, 34.3, 30.8, 21.3, 19.8, 19.5, 19.4, 18.9, 18.8, 18.6;
HRMS (MALDI-FTMS): calcd for C25H36NaN6O5S2: 587.2081, found:
587.2062 [M+Na]+.
Synthesis of compound 9: Deprotecting the Fmoc group in 8 and cou-
pling with Na-Fmoc-Thr(O-trityl)-OH followed the procedure described
in synthesis of 5. Compound 9 was obtained in 92% yield as a white
foam. [a]2D4 = À13.9 (c=0.56 in CHCl3); 1H NMR (600 MHz, CDCl3, 25
8C, TMS): d = 8.15 (s, 1H), 8.06 (s, 1H), 7.93 (d, J=9.2 Hz, 1H), 7.73
(d, J=7.5 Hz, 2H), 7.53 (m, 8H), 7.47 (d, J=8.4 Hz, 1H), 7.37 7.34 (m,
2H), 7.28 7.22 (m, 11H), 5.98 (m, 1H), 5.75 (br, 1H), 5.39 5.35 (m, 2H),
5.25 (d, J=10.1 Hz, 1H), 5.18 (dd, J=18.3, 6.6 Hz, 1H), 4.81 (d, J=
5.3 Hz, 2H), 4.34 (m, 1H), 4.29 (dd, J=9.7, 7.9 Hz, 1H), 4.24 (dd, J=
10.1, 7.5 Hz, 1H), 4.14 4.12 (m, 1H), 3.49 (br, 1H), 2.61 (m, 1H), 2.38
(m, 1H), 1.14 (m, 3H), 1.01 0.99 (m, 3H), 0.96 (d, J=6.6 Hz, 6H), 0.82
(d, J=6.6 Hz, 3H); 13C NMR (150 MHz, CDCl3): d = 171.8, 169.5, 160.8,
160.7, 155.0, 149.2, 147.0, 143.7 (2C), 143.6, 141.1, 128.6, 128.1, 127.6,
Synthesis of compound 13: Deprotecting the Fmoc group in 8 and cou-
pling with Na-allo-Fmoc-threonine followed the procedure described in
synthesis of 5. Compound 13 was obtained in 95% yield. [a]2D4 = À41.0
(c=1.07 in CHCl3); 1H NMR (600 MHz, CDCl3, 258C, TMS): d = 8.28
(d, J=9.6 Hz, 1H), 8.09 (s, 1H), 8.04 (s, 1H), 7.76 (d, J=7.5 Hz, 2H),
7.58 (d, J=7.5 Hz, 2H), 7.43 (d, J=8.8 Hz, 1H), 7.39 (t, J=7.5 Hz, 2H),
7.30 (t, J=7.5 Hz, 2H), 6.03 5.96 (m, 1H), 5.94 (d, J=8.4 Hz, 1H), 5.39
5.35 (m, 2H), 5.29 5.26 (m, 2H), 4.81 (d, J=5.7 Hz, 2H), 4.55 (d, J=
74
¹ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Chem. Eur. J. 2004, 10, 71 75

Total Synthesis of Bistratamides
71 75
5.3 Hz, 1H), 4.42 4.35 (m, 2H), 4.25 4.20 (m, 2H), 4.08 4.06 (m, 1H),
2.48 2.44 (m, 1H), 2.35 2.32 (m, 1H), 1.31 (d, J=6.1 Hz, 3H), 1.05 (d,
J=7.0 Hz, 3H), 1.00 (d, J=7.0 Hz, 3H), 0.99 (d, J=6.6 Hz, 3H), 0.93 (d,
J=7.0 Hz, 3H); 13C NMR (150 MHz, CDCl3): d = 171.2 (2C), 170.5,
160.8, 160.4, 156.5, 148.7, 146.6, 143.7, 143.6, 141.2, 131.6, 127.7, 127.2,
127.0, 125.0, 123.9, 120.0, 119.0, 69.1, 67.2, 66.0, 59.2, 56.5, 56.1, 47.0, 33.8,
33.5, 20.4, 19.5, 19.2, 18.2, 17.2; HRMS (MALDI-FTMS): calcd for
C38H43N5O7S2: 746.2677, found: 746.2677 [M+H]+.
[1]a) S. Carmeli, R. E. Moore, G. M. L. Patterson, T. H. Corbett, F. A.
Valeriote, J. Am. Chem. Soc. 1990, 112, 8195 8197; b) S. Carmeli,
R. E. Moore, G. M. L. Patterson, Tetrahedron Lett. 1991, 32, 2593
2596; c) R. J. Boyce, G. C. Mulqueen, G. Pattenden, Tetrahedron
1995, 51, 7321 7330; d) J. Ogino, R. E. Moore, G M. L. Patterson,
C. D. Smith, J. Nat. Prod. 1996, 59, 581 586; e) for reviews see: B. S.
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[2]a) C. D. J. Boden, G. Pattenden, J. Chem. Soc. Perkin Trans. 1 2000,
875 882; b) P. Wipf, P. C. Fritch, J. Am. Chem. Soc. 1996, 118, 12
358 12367; c) B. Mckeever, G. Pattenden, Tetrahedron Lett. 2001,
42, 2573 2577; d) P. Wipf, Y. Uto, J. Org. Chem. 2000, 65, 1037
1049; e) L. A. Morris, J. J. Kettenes van den Bosch, K. Versluis, G. S.
Thompson, M. Jaspars, Tetrahedron 2000, 56, 8345 8353.
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[4]Bistratamides A and B: B. M. Degnan, C. J. Hawkins, M. F. lavin,
E. J. McCaffrey, D. L. Parry, D. J. Watters, J. Med. Chem. 1989, 32,
1354 1359.
Synthesis of compound 14: Deprotecting the Fmoc group in 13 and cou-
pling with Na-Fmoc-valine followed the procedure described in synthesis
of 5. Compound 14 was obtained in 86% yield: [a]2D4 = À42.0 (c=0.92 in
CHCl3); 1H NMR (600 MHz, CDCl3, 258C, TMS): d
= 8.26 (d, J=
9.7 Hz, 1H), 8.08 (s, 1H), 7.99 (s, 1H), 7.75 (d, J=7.5 Hz, 1H), 7.73 (d,
J=7.9 Hz, 2H), 7.57 7.53 (m, 2H), 7.49 (d, J=7.5 Hz, 1H), 7.39 7.35 (m,
2H), 7.29 7.25 (m, 2H), 5.98 (m, 1H), 5.91 (d, J=8.8 Hz, 1H), 5.39 5.34
(m, 2H), 5.27 5.24 (m, 2H), 4.80 (d, J=5.7 Hz, 2H), 4.65 (d, J=5.7 Hz,
1H), 4.53 (dd, J=7.5, 7.0 Hz, 1H), 4.38 (dd, J=10.1, 8.9 Hz, 1H), 4.24
(q, J=7.3 Hz, 1H), 4.18 (dd, J=7.5, 7.0 Hz, 1H), 4.13 4.12 (m, 1H),
2.48 2.46 (m, 2H), 2.32 2.30 (m, 1H), 2.12 2.08 (m, 1H), 1.27 (d, J=
6.1 Hz, 3H), 1.03 (d, J=7.0 Hz, 3H), 0.98 0.97 (m, 6H), 0.93 (d, J=
6.6 Hz, 3H), 0.92 (d, J=6.6 Hz, 3H), 0.89 (d, J=6.6 Hz, 3H); 13C NMR
(150 MHz, CDCl3): d = 172.0, 171.3, 171.0, 170.7, 160.8, 160.4, 156.4,
148.7, 146.6, 143.7, 143.6, 141.2, 131.6, 127.6, 127.3, 127.0, 125.0, 123.8,
119.9, 118.9, 68.6, 67.0, 66.0, 60.1, 57.8, 56.6, 56.1, 47.0, 38.5, 33.6, 33.3,
31.5, 20.4, 19.5, 19.1, 18.2, 18.0, 17.1; HRMS (MALDI-FTMS): calcd for
C43H52NaN6O8S2: 867.3180, found: 867.3202 [M+Na]+.
[5]Bistratamides
C and D: M. P. Foster, G. P. ConcepciÛn, G. B.
Caraan, C. M. Ireland, J. Org. Chem. 1992, 57, 6671 6675.
[6]a) E. Aguilar, A. I. Meyers, Tetrahedron Lett. 1994, 35, 2477 2480;
b) S. V. Downing, E. Aguilar, A. I. Meyers, J. Org. Chem. 1999, 64,
826 831.
[7]a) U. Schmidt, R. Utz, Angew. Chem. 1984, 96, 723 724; Angew.
Chem. Int. Ed. Engl. 1984, 23, 725 726; b) U. Schmidt, P. Gleich,
Angew. Chem. 1985, 97, 569 571; Angew. Chem. Int. Ed. Engl.
1985, 24, 606 608; c) U. Schmidt, R. Utz, A. Lieberknecht, H.
Griesser, B. Potzolli, J. Bahr, K. Wagner, P. Fischer, Synthesis 1987,
233 236; d) M. W. Bredenkamp, C. W. Holzapfel, W. J. van Zyl,
Synth. Commun. 1990, 20, 2235 2249.
[8]a) M. North, G. Pattenden, Tetrahedron 1990, 46, 8267 8290;
b) C. D. J. Boden, G. Pattenden, T. Ye, Synlett 1995, 417 419.
[9]Mitsunobu conditions: a) N. Galÿotti, C. Montagne, J. Poncet, P.
Jouin, Tetrahedron Lett. 1992, 33, 2807 2810; b) P. Wipf, C. P.
Miller, Tetrahedron Lett. 1992, 33, 6267 6270.
[10]Burgess reagent: P. Wipf, P. C. Fritch, Tetrahedron Lett. 1994, 35,
5397 5400.
[11]a) S.-L. You, H. Razavi, J. W. Kelly, Angew. Chem. 2003, 115, 87
89; Angew. Chem. Int. Ed. 2003, 42, 83 85; b) P. Raman, H. Razavi,
J. W. Kelly, Org. Lett. 2000, 2, 3289 3292.
[12]a) J. B. Hendrickson, S. M. Schwartzman, Tetrahedron Lett. 1975, 16,
277 280; b) A. Aaberg, T. Gramstqd, S. Husebye, Tetrahedron Lett.
1979, 20, 2263 2264; c) J. B. Hendrickson, M. S. Hussoin, J. Org.
Chem. 1987, 52, 4137 4139; d) J. B. Hendrickson, M. A. Walker, A.
Varvak, M. S. Hussoin, Synlett 1996, 661 662.
Synthesis of compound 16: Compound 16 was synthesized from 14 in 81
% yield, following the procedure described in synthesis of 12. [a]D24
=
À124.6 (c=0.56 in CHCl3); 1H NMR (600 MHz, CDCl3, 258C, TMS): d
= 8.47 (d, J=8.8 Hz, 1H), 8.07 (s, 1H), 7.95 (d, J=10.1 Hz, 1H), 7.87 (d,
J=7.5 Hz, 1H), 7.75 (s, 1H), 7.72 (d, J=8.3 Hz, 1H), 5.24 (dd, J=8.8,
5.7 Hz, 1H), 5.10 (t, J=8.3 Hz, 1H), 4.66 4.62 (m, 2H), 4.37 (br, 1H),
3.61 (t, J=7.0, 1H), 2.53 2.50 (m, 1H), 2.26 2.16 (m, 2H), 1.27 (d, J=
6.6 Hz, 3H), 1.08 (d, J=7.0 Hz, 3H), 1.05 (d, J=6.6 Hz, 3H), 1.03 (d, J=
6.6 Hz, 3H), 0.99 (d, J=7.0 Hz, 6H), 0.97 (d, J=6.6 Hz, 3H); 13C NMR
(150 MHz, CDCl3): d = 172.1, 170.3, 169.1, 168.9, 161.0, 160.0, 149.8,
147.8, 123.4, 123.3, 67.0, 62.2, 57.8, 56.1 (2C), 34.7, 34.4, 29.8, 20.2, 19.6,
19.1, 18.9, 18.6, 17.1; HRMS (MALDI-FTMS): calcd for
C25H36NaN6O5S2: 587.2081, found: 587.2059 [M+Na]+.
Synthesis of bistratamide E (1): The Burgess reagent (48 mg, 97%,
0.2 mmol) was added to a solution of 16 (85 mg, 0.15 mmol) in THF
(8 mL). After stirring at 258C for 10 min, the mixture was refluxed for
2 h. Regular workup and purification with flash chromatography gave
bistratamide E (1) as a white solid (52 mg, 63%). M.p. 90 968C; [a]D25
=
À35.7 (c=0.53 in MeOH)[3]: [a]D =À31.0 (c=1.0 in MeOH)]; 1H NMR
(600 MHz, DMSO, 258C): d = 8.57 (d, J=8.3 Hz, 1H), 8.39 (s, 1H), 8.36
(s, 1H), 8.05 (d, J=9.7 Hz, 1H), 7.79 (d, J=8.8 Hz, 1H), 5.52 (dd, J=8.3,
4.4 Hz, 1H), 5.30 (dd, J=8.8, 5.3 Hz, 1H), 4.83 (m, 1H), 4.78 (dq, J=8.3,
6.1 Hz, 1H), 4.24 (dd, J=8.8, 1.8 Hz, 1H), 2.33 (m, 1H), 2.22 (m, 1H),
2.05 (m, 1H), 1.47 (d, J=6.1 Hz, 3H), 0.95 (d, J=7.0 Hz, 3H), 0.90 (d,
J=7.0 Hz, 3H), 0.89 (d, J=6.6 Hz, 3H), 0.86 (d, J=6.1 Hz, 3H), 0.85 (d,
J=6.6 Hz, 6H); 13C NMR (150 MHz, DMSO): d = 169.4, 168.2, 168.0,
167.9, 159.4, 158.8, 148.1, 147.6, 125.2, 124.9, 82.0, 72.8, 54.8, 54.0, 51.2,
34.3, 34.2, 30.5, 21.4, 18.8, 18.1, 17.9, 17.5, 17.4, 16.0; HRMS (MALDI-
FTMS): calcd for C25H34N6O5S2: 547.2156, found: 547.2173 [M+H]+.
[13]M. Dessolin, M.-G. Guillerez, N. Thieriet, F. Guibÿ, A. Loffet, Tetra-
hedron Lett. 1995, 36, 5741 5744.
[14]Z. Xia, C. D. Smith, J. Org. Chem. 2001, 66, 3459 3466.
[15]a) A. J. Blake, J. S. Hannam, K. A. Jolliffe, G. Pattenden, Synlett
2000, 1515 1518; b) A. Bertram, G. Pattenden, Synlett 2000, 1519
1521; c) A. Bertram, G. Pattenden, Heterocycles 2002, 58, 521 561.
[16]a) T. H˘eg-Jensen, M. H. Jakobsen, A. Holm, Tetrahedron Lett.
1991, 32, 6387 6390; b) J. Coste, D. Le-Nguyen, B. Castro, Tetrahe-
dron Lett. 1990, 31, 205 208.
[17]Crystal data for 2¥DMSO: C25H36N6O5S2¥C2H6OS, Mr =564.72¥78.13,
monoclinic space group, P21, a=10.1299(16), b=9.2194(15), c=
18.628(3) ä, b=104.523(3)8, V=1684.1(5) ä3, Z=2, 1calcd
=
1.268 MgmÀ3
; . 12
MoKa radiation, l=0.71073 ä, m=0.267 mmÀ1
Acknowledgments
544 data (5895 unique, Rint =0.0292, q <25.008) were collected on a
Bruker SMART APEX CCD X-ray diffractometer. CCDC-214886
(2¥DMSO) contains the supplementary crystallographic data for this
paper. These data can be obtained free of charge via www.ccdc.ca-
m.ac.uk/conts/retrieving.html(or from the Cambridge Crystallo-
graphic Data Center, 12 Union Road, Cambridge CB21EZ, UK;
fax: (+44)1223-336-033; or deposit@ccdc.cam.ac.uk).
We gratefully acknowledge NIH grant GM63212 and the Skaggs Institute
for Chemical Biology for generous financial support. We thank Dr. Raj
K. Chadha for the X-ray structure determination and Professor Evan T.
Powers for helpful discussions.
Received: September 2, 2003 [F5504]
75
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¹ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim