Total synthesis and antiangiogenic activity of cyclopentane analogues of fumagillol

Article abstract of DOI:10.1016/j.bmcl.2005.05.065

Novel cyclopentane analogues of fumagillol were synthesized and their endothelial cell proliferation inhibitory activities were evaluated. The cyclopentane-fumagillol derivatives were synthesized from (-)-2,3-O- isopropylidene-d-erythronolactone via stereoselective glycolate Claisen rearrangement and intramolecular ester enolate alkylation as key steps.

Full text of DOI:10.1016/j.bmcl.2005.05.065

Bioorganic & Medicinal Chemistry Letters 15 (2005) 3580–3583
Total synthesis and antiangiogenic activity of
cyclopentane analogues of fumagillol
Byeong-Seon Jeong,a, Nam Song Choi,a Soon Kil Ahn,a,* Hoon Bae,b,à
Hak Sung Kimc and Deukjoon Kimb
aNew Drug Research Laboratories, Chong Kun Dang Research Institute, Cheonan 330-831, Republic of Korea
bCollege of Pharmacy, Seoul National University, Seoul 151-742, Republic of Korea
cCollege of Pharmacy, Wonkwang University, Iksan 570-749, Republic of Korea
Received 14 April 2005; revised 12 May 2005; accepted 14 May 2005
Abstract—Novel cyclopentane analogues of fumagillol were synthesized and their endothelial cell proliferation inhibitory activities
were evaluated. The cyclopentane-fumagillol derivatives were synthesized from (ꢀ)-2,3-O-isopropylidene-D-erythronolactone via
stereoselective glycolate Claisen rearrangement and intramolecular ester enolate alkylation as key steps.
ꢀ 2005 Elsevier Ltd. All rights reserved.
Angiogenesis is the phenomenon of generating a new
capillary vessel, which is one of the normal physiological
functions and one of the pathological functions caused
by various diseases as well. It has deep connection with
growth and transfer of solid cancer, rheumatic arthritis,
diabetic retinopathy, psoriasis, etc.1 Since the Folkman
research group suggested a novel concept of treating sol-
id cancer by inhibiting angiogenesis in 1971,2 clinical
importance of therapeutic agents controlling angiogene-
sis has been emphasized, and much endeavor on angio-
genesis seems to have been bestowed on it.
Figure 1.
Fumagillin(1),anaturalproductisolatedfromAspergillus
fumigatus,3 was found by the Folkman group in 19904 to
of
methionine
aminopeptidase
type
2
strongly inhibit endothelial cell proliferation. Many
semi-synthetic analogues have been synthesized from
fumagillol (2), the hydrolysis product of fumagillin.4
Among these analogues, TNP-470 (3)4a and CKD-732
(4)4c,d are currently employed in clinical trials for the
treatment of a variety of cancers (Fig. 1). The mecha-
nism of action of these agents, including fumagillin, is
proposed to inhibit angiogenesis by selective inhibition
(MetAP-2) through covalent bonding to the His231 res-
idue of MetAP-2 by opening the spiro-epoxide.5
We have reported the first asymmetric total synthesis of
fumagillol, featuring the chelation-controlled glycolate
Claisen rearrangement and the intramolecular ester eno-
late alkylation as the key steps.6,7 As an ongoing project
to expand structural diversity, the cyclopentane ring
shown in 5 was introduced, instead of the naturally
occurring cyclohexane skeleton of fumagillol (Fig. 1).
We anticipated that this approach could lead to novel
angiogenesis inhibitors since cyclopentane analogue 5
is not available from fermentation and it possesses a
high level of homology to the fumagillol structure. It
has a spiro-epoxide and an isoamyl side chain, which
are proposed to be essential for activity and for
Keywords: Fumagillol; Angiogenesis.
*
Corresponding author. Tel.: +82 41 529 3107; fax: +82 41 558
3004; e-mail: skahn@ckdpharm.com
Present address: Department of Chemistry, Vanderbilt University,
Nashville, TN 37235, USA.
à Present address: Department of Chemistry and Biochemistry, Florida
State University, Tallahassee, FL 32306, USA.
0960-894X/$ - see front matter ꢀ 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2005.05.065

B.-S. Jeong et al. / Bioorg. Med. Chem. Lett. 15 (2005) 3580–3583
3581
hydrophobic interaction with MetAP-2, respectively.
Moreover, the stereochemistry of the substituents in
the cyclopentane ring is identical to that of fumagillol.
DCC coupling from 9 or Mitsunobu reaction from 90
in good yield. The c,d-unsaturated glycolate 11 was effi-
ciently obtained as a single diastereomer by 1,3-chirality
transfer through a chelation-controlled chair-like transi-
tion state of the Burke–Fujisawa–Kallmerten modifica-
tion of the Ireland–Claisen rearrangement.9,10
Intramolecular ester enolate alkylation of the tosylate
12, which was converted from 11 by desilylation and
tosylation, was performed with KHMDS at 0 ꢁC in a
short time to produce the desired cyclopentane-carbox-
ylate 13 in 66% yield with a 10:1 mixture of inseparable
diastereomers. The excellent diastereomeric excess im-
plies that this cyclization may proceed through an allylic
strain-controlled ÔH-eclipsedÕ transition state.10
Our synthesis, which is described in Scheme 1,8 began
with commercially available (ꢀ)-2,3-O-isopropylidene-
D-erythronolactone 6, which was converted to the corre-
sponding lactol with DIBAL-H, followed by the Wittig
reaction with (carbomethoxyethylidene)triphenyl-phos-
phorane to afford the a,b-unsaturated ester 7 in 87%
yield for the two steps. After protection of the alcohol
with the TBDPS group, the methyl ester was trans-
formed to the aldehyde 8 by the sequence of reduction
with DIBAL-H and MnO2 oxidation (83% overall yield
for the three steps). Addition of isoamylmagnesium bro-
mide to the aldehyde 8 produced a 3:1 mixture of allylic
alcohols 9 and 90 where each compound could be iso-
lated by silica column chromatography in 95% total
yield. The absolute configuration of the newly generated
stereocenter in 9 and 90 was confirmed by spectroscopic
analysis of the compounds 13 and 130 (vide infra). The
allylic glycolate ester 10 could be prepared using either
The absolute configuration of 13 was verified by chemi-
cal transformation and NMR analysis. An observation
of the formation of the lactones (15 or 150) in high yield
in the case of treatment of the diol 14 with DBU is
reliable evidence that expected stereo-chemistry of the
C(a) position in 13 is correct. For the stereochemistry
1
at the C(b) position, H NMR studies were conducted.
Scheme 1. Reagents and conditions: (a) DIBAL-H, CH2Cl2, ꢀ78 ꢁC, 3 h, 92%; (b) Ph3P=C(Me)CO2Me, toluene, reflux, 1 h, 95%; (c) TBDPSCl,
imidazole, DMF, rt, 3 h, 95%; (d) DIBAL-H, CH2Cl2, ꢀ78 ꢁC, 4 h, 96%; (e) MnO2, CH2Cl2, rt, 20 h, 91%; (f) isoamylMgBr, THF, ꢀ78 ꢁC, 1 h, 70%
of 9 and 25% of 90; (g) BnOCH2CO2H, DCC, DMAP, CH2Cl2, rt, 3 h, 77%; (g0) BnOCH2CO2H, PPh3, DIAD, THF, 0 ꢁC, 30 min then rt, 3 h, 82%;
(h) (i) LiHMDS, TMSCl/Et3N, THF, ꢀ78 ꢁC, 1 h then rt, 10 h, (ii) CH2N2, Et2O, 0 ꢁC, 5 min, 70% (for 2 steps); (i) TBAF, THF, rt, 12 h, 80%; (j)
TsCl, pyridine, CHCl3, 4 ꢁC, 20 h, 98%; (k) KHMDS, THF, 0 ꢁC, 10 min, 66% (10:1 mixture of inseparable diastereomers); (l) PPTS, MeOH, reflux,
20 h, 98%; (m) DBU, CH3CN, reflux, 6 h, 96% (15:150 = 1:1); (m0) NaOMe, MeOH, rt, 6 h, 95%; (n) Ag2O, MeI, reflux, 4 h, 80%; (o) Li, liq. NH3,
ꢀ78 ꢁC, 3 h, 62%; (p) TsCl, Et3N, DMAP, CH2Cl2, rt, 18 h, 80%; (q) K2CO3, MeOH, rt, 2 h, 90%; (r) m-CPBA, NaHCO3, CH2Cl2, 0 ꢁC, 4 h, 94%
(ca. 3:1 of inseparable diastereomeric mixture); (s) chloroacetyl isocyanate, Et3N, DMAP, CH2Cl2, 0 ꢁC, 71% (18% of 20 and 53% of 200).

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B.-S. Jeong et al. / Bioorg. Med. Chem. Lett. 15 (2005) 3580–3583
Upon irradiation of the H(b) in 13, nuclear Overhauser
effect (NOE) was observed to be 1.4% for the H(c), while
NOE in the diastereomer 130 prepared from 90 was 5.6%.
These results nicely support the fact that H(b) and H(c)
in 13 have a trans-relationship (Fig. 2).
values were colorimetrically measured by SRB (CPAE
cell) or MTT (EL-4, P388) methods. The biological data
are shown in Table 1. The prepared novel cyclopentane
analogues of fumagillol showed endothelial cell prolifer-
ation inhibitory activity at lM concentration. However,
their activities turned out to be lower than those of fum-
agillin derivatives.
Although several methods for the selective methylation
of C(c)-alcohol in 14, which was prepared from 13 by
treatment with PPTS in methanol, with/without protec-
tion of the other hydroxyl group were attempted, we
failed to obtain the desired mono-methoxy product in
good yield. Lactonization turned out to be the best pro-
tection to give a 1:1 mixture of separable regioisomers
(15 and 150), with the undesired isomer 150 being recy-
cled. Then, methylation of the hydroxyl group in 15
was successfully performed with Ag2O/MeI reaction
system to give 16 in 80% yield. Removal of the benzyl-
protecting group in 16 along with the concurrent reduc-
tion of the lactone was accomplished using excess
lithium in liquid ammonia to produce the triol 17 in
62% yield. Selective mono-tosylation of the primary hy-
droxyl group in 17, followed by treatment with mild
base, afforded the spiro-epoxy compound 18 in 72%
yield for the two steps. Epoxidation of the olefin in 18
with m-CPBA produced a 3:1 mixture of inseparable
diastereomers 19 in 94% yield.
In summary, total synthesis of a novel cyclopentane
analogue of fumagillol was carried out using glycolate
Claisen rearrangement and intramolecular ester eno-
late alkylation as key steps. Studies on the struc-
ture–activity relationship of fumagillol analogues are
underway.
Acknowledgments
This work was supported by Grants (01-PJ1-PG4-
01PT01-0004 and 00-PJ2-PG-1-CD02-0018) from the
Ministry of Health & Welfare, Republic of Korea.
References and notes
1. (a) Folkman, J. J. Natl. Cancer Inst. 1990, 82, 4; (b)
Hanahan, D.; Folkman, J. Cell 1996, 86, 353.
2. Folkman, J. N. Engl. J. Med. 1971, 285, 1182.
To measure the endothelial cell proliferation inhibitory
activity of the novel cyclopentane analogue of fumagil-
lol, chloroacetylcarbamoyl group, a side chain of
TNP-470 (3), was introduced, and each diastereomer
(20 and 200) was isolated by silica column chromato-
graphy. Anti-proliferating activities were evaluated
against calf pulmonary artery endothelial (CPAE) cells,
lymphoma EL-4 cells, and murine leukemia P388. IC50
3. Hanson, F. R.; Eble, E. J. Bacteriol. 1949, 58, 527.
4. (a) Ingber, D. E.; Fujita, T.; Kishmoto, S.; Sudo, K.;
Kanamaru, T.; Brem, H.; Folkman, J. Nature 1990, 345,
555; (b) Marui, S.; Itoh, F.; Kozai, Y.; Sudo, K.;
Kishimoto, S. Chem. Pharm. Bull 1992, 40, 96; (c) Hong,
C. I.; Kim, J. W.; Lee, S. J.; Ahn, S. K.; Choi, N. S.; Hong,
R. K.; Chun, H. S.; Moon, S. K.; Han, C. K. W.O. Patent
9959986, 1999; (d) Han, C. K.; Ahn, S. K.; Choi, N. S.;
Hong, R. K.; Moon, S. K.; Chun, H. S.; Lee, S. J.; Kim, J.
W.; Hong, C. I.; Kim, D.; Yoon, J. H.; No, K. T. Bioorg.
Med. Chem. Lett. 2000, 10, 39; (e) Fardis, M.
Pyun, H.-J.; Tario, J.; Jin, H.; Kim, C. U.; Ruckman, J.;
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USA 1997, 94, 6099; (b) Liu, S.; Widom, J.; Kemp, C. W.;
Crews, C. M.; Clardy, J. Science 1998, 282, 1324.
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Tetrahedron Lett. 1997, 38, 4437; (b) Kim, D.; Ahn, S. K.;
Bae, H.; Kim, H. S. Arch. Pharm. Res. 2005, 28, 129.
7. For total syntheses or approaches to fumagillin and
analogues by other groups see: (a) Corey, E. J.; Snider, B.
B. J. Am. Chem. Soc. 1972, 94, 2549; (b) Taber, D. F.;
Christos, T. E.; Rheingold, A. L.; Guzei, I. A. J. Am.
Chem. Soc. 1999, 121, 5589; (c) Vosburg, D. A.; Weiler, S.;
Sorensen, E. J. Angew Chem. Int. Ed. 1999, 38, 971; (d)
Picoul, W.; Urchegui, R.; Haudrechy, A.; Langlois, Y.
Tetrahedron Lett. 1999, 40, 4797; (e) Moffat, D.; Simpkins,
N. S. Synlett 2001, 661; (f) Boiteau, J.-G.; Van de Weghe,
P.; Eustache, J. Org. Lett. 2001, 3, 2737; (g) Vosburg, D.
A.; Weiler, S.; Sorensen, E. J. Chirality 2003, 15, 156; (h)
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Figure 2.
Table 1. In vitro endothelial cell proliferation inhibitory activities
against CPAE, EL-4, and P-388 cell lines
Compound
IC50 (lg/mL)
CPAE
EL-4
P-388
20
200
8.8 · 10ꢀ2
3.0 · 10ꢀ1
1.1
P10
P10
5.7 · 10ꢀ1
Fumagillin (1)
TNP-470 (3)
3.0 · 10ꢀ3
2.0 · 10ꢀ4
1.6 · 10ꢀ3
3.8 · 10ꢀ3
P10
P10
8. All new compounds exhibited satisfactory spectroscopic
and analytical data, and the ratio of stereoisomers was

B.-S. Jeong et al. / Bioorg. Med. Chem. Lett. 15 (2005) 3580–3583
3583
1
determined by the H NMR analysis and/or isolation of
individual isomers. Selected data for the key intermediates
11 and 13: For 11 H NMR (400 MHz, CHCl3-d) d 7.24–
52.4, 39.1, 38.3, 28.0, 27.7, 26.3, 25.3, 23.0, 22.8, 21.4, 15.8,
14.6; EI-MS (m/z) 415 (M+ꢀ1).
1
9. (a) Burke, S. D.; Fobare, W. F.; Pacofsky, G. J. J. Org.
Chem. 1983, 48, 5221; (b) Sato, T.; Tajima, K.; Fujisawa,
T. Tetrahedron Lett. 1983, 24, 729; (c) Kallmerten, J.;
Gould, T. J. Tetrahedron Lett. 1983, 24, 5177.
10. Plausible transition states for the two transformations
(10 ! 11 and 12 ! 13).
7.76 (m, 15H), 5.14 (t, 1H, J = 6.5 Hz), 4.48 (d, 1H,
J = 11.3 Hz), 4.33 (d, 1H, J = 11.3 Hz), 4.21–4.26 (m, 2H),
4.00 (d, 1H, J = 10.2 Hz), 3.90 (dd, 1H, J = 10.8, 5.4 Hz),
3.82 (dd, 1H, J = 10.8, 5.4 Hz), 3.61 (s, 3H), 2.95 (dd, 1H,
J = 0.2, 9.8 Hz), 1.88–1.92 (m, 2H), 1.58 (s, 3H), 1.42–1.51
(m, 1H), 1.37 (s, 3H), 1.29 (s, 3H), 1.08–1.11 (m, 2H), 1.06
(s, 9H), 0.85 (d, 6H, J = 6.6 Hz); 13C NMR (100 MHz,
CHCl3-d) d 172.1, 137.3, 136.2, 136.1, 134.4, 134.2, 131.4,
130.7, 129.7, 128.8, 128.5, 128.3, 127.9, 127.8, 125.9, 107.2,
81.5, 79.9, 73.2, 64.6, 51.8, 50.8, 41.4, 38.9, 27.9, 27.8, 27.4,
25.9, 25.7, 22.9, 22.8, 19.7, 13.5; EI-MS (m/z) 673 (M++1).
For 13 1H NMR (400 MHz, CHCl3-d) d 7.26–7.38 (m,
5H), 5.28 (t, 1H, J = 7.2 Hz), 4.85 (d, 1H, J = 7.1 Hz),
4.64–4.69 (m, 1H), 4.57 (d, 1H, J = 11.5 Hz), 4.34 (d, 1H,
J = 11.5 Hz), 3.74 (s, 3H), 2.98 (d, 1H, J = 7.1 Hz), 2.64
(dd, 1H, J = 14.3, 5.3 Hz), 2.42 (dd, 1H, J = 14.3, 5.3 Hz),
2.02–2.04 (m, 2H), 1.72 (s, 3H), 1.47–1.54 (m, 1H), 1.32 (s,
3H), 1.26 (s, 3H), 1.19–1.21 (m, 2H), 0.87 (d, 6H, J = 6.6
Hz); 13C NMR (100 MHz, CHCl3-d) d 172.3, 138.9, 131.1,
128.6, 127.9, 127.7, 113.7, 92.5, 82.5, 78.7, 68.1, 63.3, 60.8,