An expedient synthesis of the amide analog of the potent antifungal lipopeptidolactone FR901469

Article abstract of DOI:10.1016/S0040-4039(00)02047-5

An expedient synthesis of the lactam analog (20) of the 40-membered lipopeptidolactone antifungal antibiotic, FR901469 (1), is described. The key steps in this synthesis are a novel biotransformation of the natural product to produce the highly versatile linear peptide building block 3, and efficient formation of the 40-membered ring by macrolactamization under high-dilution conditions.

Full text of DOI:10.1016/S0040-4039(00)02047-5

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 42 (2001) 703–705
An expedient synthesis of the amide analog of the potent
antifungal lipopeptidolactone FR901469
David Barrett,a,* Akira Tanaka,a Akihiko Fujie,b Nobuharu Shigematsu,b Michizane Hashimotob
and Seiji Hashimotob
aMedicinal Chemistry Research Laboratories, Fujisawa Pharmaceutical Co. Ltd., 2-1-6 Kashima, Yodogawa-ku,
Osaka 532-8514, Japan
bExploratory Research Laboratories, Fujisawa Pharmaceutical Co. Ltd., 5-2-3-chome, Tokodai, Tsukuba,
Ibaraki 300-2698, Japan
Received 4 October 2000; accepted 10 November 2000
Abstract—An expedient synthesis of the lactam analog (2) of the 40-membered lipopeptidolactone antifungal antibiotic, FR901469
(1), is described. The key steps in this synthesis are a novel biotransformation of the natural product to produce the highly
versatile linear peptide building block 3, and efficient formation of the 40-membered ring by macrolactamization under
high-dilution conditions. © 2001 Elsevier Science Ltd. All rights reserved.
The last decades of the twentieth century have seen an
increase in the incidence of severe, life-threatening inva-
sive fungal diseases. This can be attributed to the
increase in the population of immunosuppressed indi-
viduals, resulting from improved outcomes in trans-
plantation surgery, aggressive anticancer regimens, and
the HIV epidemic.1 During this period, the polyene
Amphotericin B (AmpB) has remained the primary
agent for first-line treatment of these infections.2 How-
ever, this drug is well known to produce a variety of
dose-limiting toxic side effects that result in discontinu-
ation of treatment and clinical failure.2 The introduc-
tion of various lipid formulations of AmpB has gone
some way to reducing the toxicity associated with this
agent,3 however, the need clearly exists for a novel,
broad spectrum, fungicidal, antifungal agent, with a
superior safety profile to AmpB.
We recently reported the isolation and biological ac-
tivity of the novel water-soluble natural products,
FR901379 (WF11899A) and FR901469 (1), which
inhibit the synthesis of 1,3-b-glucan, a key component
of the fungal cell wall.4,5 FR901379 is a member of
the echinocandin class of natural products6 and a
semi-synthetic derivative, FK463, is currently in
phase III clinical trials.7 FR901469 shows potent
antifungal activity and excellent water solubility,
however the presence of an ornithine amine
group adjacent to the ester moiety results in a pH-de-
pendent ring opening process leading to a biologically
inactive linear lipopeptide. In order to remove this
propensity for ring opening, we designed the amide
analog 2 of the natural product and herein disclose
efficient methodology for the synthesis of this com-
pound.
HO
OH
OH
N
H
N
H
N
H
N
H
N
O
O
O
O
N
O
1 X = O (FR901469)
2 X = NH
O
X
HN
NH
O
HCl.H2N
O
NH
O
O
O
H
N
H
N
H
N
OH
O
O
HO
OH
OH
H2N
OH
O
Keywords: antifungals; macrocycles; microbial reactions; peptides and polypeptides.
* Corresponding author. Fax: 06-6304-5435; e-mail: david barrett@po.fujisawa.co.jp
–
0040-4039/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(00)02047-5

704
D. Barrett et al. / Tetrahedron Letters 42 (2001) 703–705
Our approach to the synthesis of 2 is based on deacyla-
tion of the lipophilic side chain of the natural product,
introduction of a pre-formed amide-substituted side
chain moiety, macrolactamization and ornithine amino
group deprotection. The key intermediate for the syn-
thesis of 2, the linear peptide 3, was produced in 35%
yield by direct incubation of FR901469 with
Actinoplanes utahensis IFO-13244 in 0.2 M phosphate
at pH 7.8 and 60°C (Scheme 1).8 In general, this
organism has been employed for deacylation of various
lipopeptide compounds and cleaves only the amide
bond connecting the lipophilic side chain to the peptide
skeleton. For example, removal of the side chain from
echinocandin B.9 In this work, we have demonstrated
another facet of this organism, whereby simultaneous
removal of a b-hydroxyacid side chain and an ornithine
moiety is also possible.
adduct 6 in 88% yield as an oil. Removal of the benzyl
groups from 6 under hydrogenation conditions pro-
duced the amine 7 in 100% yield. The enantiomeric
excess of this amine was 93.1% by conversion to the
Mosher amide ((S)-(+)-MTPACl-Et3N-CH2Cl2) and
GC analysis. Completion of the synthesis of 9 involved
coupling of 7 with Z-Orn(BOC)OH using a water solu-
ble carbodiimide derivative (1-ethyl-3-dimethylamino-
propylcarbodiimide hydrochloride, WSCD.HCl) to
afford the b-amino acid derivative 8 in 90% yield. Ester
hydrolysis (LiOH-MeOH-H2O, 99%) gave the corre-
sponding carboxylic acid, which was then smoothly
converted to the activated ester 9 (HOBT-WSCD.HCl-
CH2Cl2-rt, 100%).
The final steps in the synthesis of 2 are shown in
Scheme 3. Selective acylation of the amine group of 3
with activated ester 9 proceeded smoothly in DMF in
the presence of diisopropylethylamine. Since the result-
ing acylated intermediate had poor water solubility,
impeding purification by ODS column chromatogra-
phy, the crude material was directly subjected to cata-
lytic hydrogenation to remove the benzyloxycarbonyl
protecting group. Purification afforded the cyclization
precursor 10 in 71% yield from 3. Macrocyclization
under high dilution conditions (1.2 mM) employing
WSCD.HCl-HOBT in DMF resulted in smooth cycliza-
For the synthesis of 2, the appropriate side-chain frag-
ment 9 was prepared as shown in Scheme 2. Aldehyde
4 was converted to the E-olefin 5 in 52% yield by Wittig
reaction with methyl(triphenylphosphoranilidene)-
acetate. A trace amount of the Z-isomer was removed
by column chromatography. Application of the Davies
asymmetric b-amino acid synthesis methodology10
involving reaction of 5 with the lithium amide derived
from (R)-N-(a-methylbenzyl)benzylamine afforded the
HO
OH
Actinoplanes utahensis IFO-13244
OH
0.2M PBS-pH 7.8-60 deg.
H2N
N
H
N
H
N
H
N
O
O
O
N
O
FR901469 (1)
HN
NH
O
(35%)
O
O
O
O
H
N
H
N
H
N
OH
O
HO2C
HO
OH
OH
H2N
OH
O
3
Scheme 1. Biotransformation of FR901469.
PPh3
CO2Me
Ph
N
Li
Ph
THF
CO2Me
toluene-reflux-2hr
(52%)
CH3(CH2)12
O
CH3(CH2)12
(88%)
5
4
Z-Orn(BOC)OH
HOBT-WSCD.HCl
CH2Cl2-rt-2hr
H2-20%Pd(OH)2-AcOH
MeOH-EtOAc-rt-7hr
Ph
CO2Me
N
Ph
CH3(CH2)12
CO2Me
CH3(CH2)12
NH2
(90%)
(100%)
6
7
CH3(CH2)12
1. LiOH-MeOH-H2O-rt-4hr(99%)
CO2Me
O
CH3(CH2)12
O
N
N
O
NH
2. HOBT-WSCD.HCl
CH2Cl2-rt-2hr(100%)
H
O
O
NH O
N
H
O
O
N
O
N
H
O
N
O
N
H
O
8
9
Scheme 2. Synthesis of the activated ester fragment.

D. Barrett et al. / Tetrahedron Letters 42 (2001) 703–705
705
HO
OH
1. 9 (1.2equiv)
HOBT-WSCD.HCl
DMF-rt-2hr
EtNPri2-DMF-rt
2. H2-PdC
OH
CH3(CH2)12
NH
NH O
N
H
N
H
N
H
N
O
O
O
N
O
O
3
H
N
(83%)
HN
NH
O
(71% from 3)
O
O
NH
O
O
O
2H
N
H
N
H
N
OH
O
O
HO2C
HO
OH
OH
H2N
10
OH
O
HO
OH
1. TFA (neat)
OH
CH3(CH2)12
N
H
N
H
N
N
H
N
O
2. ODS Chromatography
H
O
O
O
O
N
O
NH
NH
H
N
2
HN
O
O
O
O
O
O
H
N
H
N
H
N
(93%)
OH
O
O
O
NH
HO
OH
OH
H2N
OH
O
11
Scheme 3. Synthesis of lactam (2).
tion of 10 to afford the cyclic peptide 11 in 83% yield as
an amorphous white solid after purification by ODS
column chromatography and lyophilization. Removal
of the BOC protecting group using neat TFA afforded
2 as the hydrochloride salt after ion-exchange chro-
matography and freeze-drying.11
1091. (b) Iwamoto, T.; Fujie, A.; Nitta, K.; Hashimoto,
S.; Okuhara, M.; Kohsaka, M. J. Antibiotics 1994, 47,
1092–1097.
5. Fujie, A.; Iwamoto, T.; Muramatsu, H.; Okudaira, T.;
Nitta, K.; Nakanishi, T.; Sakamoto, K.; Hori, Y.; Hino,
M.; Hashimoto, S.; Okuhara, M. J. Antibiotics 2000, 53,
912–919.
In summary, we disclose novel methodology whereby
the lactone moiety of the natural product FR901469
can be modified to an amide group, thereby removing
the propensity for ring opening whilst maintaining
potent antifungal activity.12 The key intermediate linear
peptide 3 was readily produced by a novel biotransfor-
mation of the natural product. This methodology is
applicable to the synthesis of a variety of novel
lipophilic side chain-modified analogs, the synthesis and
biological activity of which will be reported in future
publications.
6. Turner, W. W.; Current, W. L. Drugs Pharm. Sci. 1997,
82, 315–334.
7. Tomishima, M.; Ohki, H.; Yamada, A.; Takasugi, H.;
Maki, K.; Tawara, S.; Tanaka, H. J. Antibiotics 1999, 52,
674–676.
8. Selected data for 3: [h]2D2=−33.7 (c 1.0, MeOH); IR (KBr)
3300, 2980, 1655, 1540, 1455, 1235 cm−1; FAB-MS (m/z):
1183 (M+H)+.
9. Boeck, L. D.; Fukuda, D. S.; Abbott, B. J.; Debono, M.
J. Antibiotics 1989, 382–388.
10. Davies, S. G.; Ichihara, O. Tetrahedron: Asymmetry 1991,
2, 183–186.
11. Selected data for 2: [h]2D8=+17.4 (c 0.67, MeOH);
IR(KBr) 3307, 2854, 1659, 1522, 1450, 1240 cm−1; FAB-
MS (m/z): 1532 (MH+−HCl); 1H NMR (200 MHz,
CD3OD, l): 0.76–1.00 (9H, m), 1.15 (3H, d, J=6.3 Hz),
1.18–1.65 (40H, m), 1.65–2.60 (9H, m), 2.80–3.05 (4H,
m), 3.58–4.90 (24H, m), 5.04 (1H, d, J=3 Hz), 6.90 (2H,
d, J=8.5 Hz), 7.06 (2H, d, J=8.5 Hz).
References
1. Anaissie, E. Clin. Infect. Dis. 1992, 14 (Suppl. 1): S43–
S53.
2. Gallis, H. A.; Drew, R. H.; Pickard, W. W. Rev. Infect.
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4. (a) Iwamoto, T.; Fujie, A.; Sakamoto, K.; Tsurumi, Y.;
Shigematsu, N.; Yamashita, M.; Hashimoto, S.;
Okuhara, M.; Kohsaka, M. J. Antibiotics 1994, 47, 1084–
12. The amide analog 2 showed comparable antifungal activ-
ity to the natural product 1 and the clinically used AmpB.
For example, MIC values against A. niger ATCC6275
were 0.5, 0.25, and 0.25 mg/ml for 2, 1, and AmpB,
respectively.
.
.