Anti-cancer activity of carbamate derivatives of melampomagnolide B

Article abstract of DOI:10.1016/j.bmcl.2014.05.059

Melampomagnolide B (MMB) is a natural sesquiterpene structurally related to parthenolide (PTL). We have shown that MMB exhibits anti-leukemic properties similar to PTL. Unlike PTL, the presence of a primary hydroxyl group in the MMB molecule allows the opportunity for examining the biological activity of a variety of conjugated analogs of MMB. We have now synthesizet a series of carbamate analogs of MMB and evaluated these derivqtives for anti-cancer activity qgainst a panel of sixty human cqncer cell lines. Analogs 6a and06e exhibited promising anti-leukemic activity against human leukemia cell line CCRF-CEM with GI₅₀ values of 680 and 620 nM, respectively. Analog 6a also showed GI₅₀ values of 1.98 and 1.38 μM respectively, against RPMI-8226 and SR leukemia cell lines and GI₅₀ values of 460 and 570 nM against MDA-MB-435 melanoma and MDA-MB-468 breast cancer cell lines, respectively. Analog 6e had GI₅₀ values of 650 and 900 nM against HOP-92 non-small cell lung and RXF 393 renal cancer cell lines.

Full text of DOI:10.1016/j.bmcl.2014.05.059

Bioorganic & Medicinal Chemistry Letters xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Anti-cancer activity of carbamate derivatives
of melampomagnolide B
⇑
Venumadhav Janganati, Narsimha Reddy Penthala, Nikhil Reddy Madadi, Zheng Chen, Peter A. Crooks
Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Melampomagnolide B (MMB) is a natural sesquiterpene structurally related to parthenolide (PTL). We
have shown that MMB exhibits anti-leukemic properties similar to PTL. Unlike PTL, the presence of a pri-
mary hydroxyl group in the MMB molecule allows the opportunity for examining the biological activity
of a variety of conjugated analogs of MMB. We have now synthesized a series of carbamate analogs of
MMB and evaluated these derivatives for anti-cancer activity against a panel of sixty human cancer cell
lines. Analogs 6a and 6e exhibited promising anti-leukemic activity against human leukemia cell line
CCRF-CEM with GI50 values of 680 and 620 nM, respectively. Analog 6a also showed GI50 values of
Received 10 April 2014
Revised 15 May 2014
Accepted 16 May 2014
Available online xxxx
Keywords:
Parthenolide
Melampomagnolide B
Anti-cancer activity
Carbamates
1.98 and 1.38 lM respectively, against RPMI-8226 and SR leukemia cell lines and GI50 values of 460
and 570 nM against MDA-MB-435 melanoma and MDA-MB-468 breast cancer cell lines, respectively.
Analog 6e had GI50 values of 650 and 900 nM against HOP-92 non-small cell lung and RXF 393 renal can-
cer cell lines.
Heterocyclic amines
Ó 2014 Published by Elsevier Ltd.
Parthenolide (PTL; 1, Fig. 1), a sesquiterpene lactone isolated
from the medicinal herb Feverfew (Tanacetum parthenium), has
been widely reported in the literature as an anticancer agent
that is effective against both hematological and solid tumors.1,2
PTL and its analogs promote apoptosis by inhibiting the activity
PTL is a major source for several novel anti-leukemic com-
pounds arising from our research program over the past decade.
The two best examples are dimethylaminoparthenolide (DMAPT;
2, Fig. 1) and melampomagnolide B (MMB; 3, Fig. 1). MMB is a
melampolide originally isolated from Magnolia grandiflora.9 MMB
can be synthesized from commercially available PTL via SeO2/
tBuOOH oxidation.10,11 Both of the above compounds 2 and 3 have
been identified as new antileukemic sesquiterpenes with proper-
ties similar to PTL.11,12 DMAPT is currently in phase 1 clinical stud-
ies for evaluation as a treatment for acute myeloid leukemia cell
(AML).12
More importantly, from a drug design point of view, MMB is a
more intriguing molecule than either PTL or DMAPT because of
the presence of the primary hydroxyl group at C-14, which can
be structurally modified to improve potency, water solubility, bio-
availability and tissue targeting of the molecule.
of the NF-
j
B transcription factor complex, and thereby down-
regulates anti-apoptotic genes under NF-
jB
control.3 Recent
studies also demonstrate that PTL induces robust apoptosis of
primary acute myeloid leukemia (AML) stem cells in culture.4,5
AML is a clonal malignancy of the hematopoietic system charac-
terized by accumulation of immature cell populations in the
bone marrow or peripheral blood,6 and is the most common
type of leukemia in adults but has the lowest survival rate of
all leukemias.7
More recently, we have shown that PTL and PTL analogs also
selectively induce almost complete glutathione depletion and
severe cell death in CD34+ AML cells,8 but exhibit significantly less
toxicity in normal CD34+ cells. PTL analogs perturb glutathione
homeostasis by a multifactorial mechanism, including inhibition
of key glutathione metabolic enzymes (GCLC and GPX1), and direct
depletion of glutathione. Thus, primitive leukemia cells are
uniquely sensitive to agents that target aberrant glutathione
metabolism, an intrinsic property of primary human AML cells.
In the current study, we have prepared a series of novel carba-
mate analogs of MMB. These compounds were initially designed as
⇑
Corresponding author. Tel.: +1 501 686 6495; fax: +1 501 686 6057.
E-mail address: pacrooks@uams.edu (P.A. Crooks).
Figure 1. Structures of PTL (1), DMAPT fumarate (2) and MMB (3).
http://dx.doi.org/10.1016/j.bmcl.2014.05.059
0960-894X/Ó 2014 Published by Elsevier Ltd.
Please cite this article in press as: Janganati, V.; et al. Bioorg. Med. Chem. Lett. (2014), http://dx.doi.org/10.1016/j.bmcl.2014.05.059

2
V. Janganati et al. / Bioorg. Med. Chem. Lett. xxx (2014) xxx–xxx
Table 1
potential prodrugs of MMB. However, we have found that on
examining the anticancer activity of these compounds, several of
the molecules exhibited significant growth inhibition properties
in a panel of sixty human cancer cell lines. Two of these com-
Structures, reaction conditions, yields, and melting points for carbamate analogs of
melampomagnolide B
Amine
Product
Yield
(%)
Time
(h)
Mp (°C)
pounds exhibited GI50 values of 610
lM against the majority of
the human cancer cell lines in the panel.
Carbamate analogs of MMB were prepared by reaction of the p-
nitrophenyloxycarbonyl ester of MMB13 with a variety of primary
and secondary heterocyclic amines containing pyrrolidine, mor-
pholine, piperidine, imidazole, triazole and pyridine moieties, to
afford carbamate products 6a–6g14 with generally improved
water-solubility (Scheme 1, Table 1) compared to MMB. The key
p-nitrophenyloxycarbonyl ester of MMB was prepared by the reac-
tion of MMB with p-nitrophenylchloroformate in the presence of
triethylamine. All conjugation reactions were carried out at ambi-
ent temperature in dichloromethane. We have reported previously
that the reaction of sesquiterpenes containing an exocyclic double
bond attached to the 13-position of the 5-membered lactone ring
with primary and secondary amines leads to the facile formation
of Michael addition products.15 However, under the reaction condi-
tions employed in Scheme 1, the rate of O-carbamoylation appears
to be much faster than the rate of C-13 Michael addition, and only
in a few cases, with amines such as 2-morpholinoethylamine, 2-
piperidinoethylamine and 3-aminopropylimidazole, were Michael
addition byproducts observed (usually in low yields of 5–10%),
due likely to the high nucleophilicity of these amines.
50
67
12
12
150
50
72
65
8
6
150
80
All compounds were purified by column chromatography (sil-
ica gel; methanol/dichloromethane) to afford pure compounds in
50–75% yield. The synthesized compounds were fully character-
ized by 1H NMR, 13C NMR and high resolution mass spectral
analysis.14
The above carbamate analogs were evaluated for growth inhibi-
tion properties against a panel of 60 human cancer cell lines
derived from nine human cancer cell types, grouped into disease
sub-panels that represent leukemia, lung, colon, central nervous
system (CNS), melanoma, renal, ovary, breast, and prostate cancer
cells. Growth inhibitory (GI50) effects were measured as a function
of the variation of optical density as a percentage of control.16,17
Initial screening assays were carried out at a single concentration
70
8
107
75
68
5
8
70
60
of 10 lM. Five analogs, 6a–6e, were identified as hits based on
their ability to inhibit by 60% the growth of at least 8 of the 60
tumor cell lines in the panel. These five analogs were then evalu-
ated in 5-dose assays over the concentration range 10ꢀ4
–
10ꢀ8
lM, and their GI50 values against the tumor cell lines in the
panel determined (Table 2). Two analogs, 6a and 6e, were identi-
fied as lead compounds and generally exhibited improved growth
inhibition against all human tumor cell lines when compared to
PTL (1) and DMAPT (2), with the exception of the leukemia cell line
subpanel; in these cell lines, the GI50 values for DMAPT compared
very favorably with those for both 6a and 6e. Compound 6a exhib-
ited potency against leukemia cell line CCRF-CEM, melanoma cell
line MDA-MB-435 and breast cancer cell line MDA-MB-468 in
the nanomolar range with GI50 values of 680, 460 and 570 nM,
respectively. Compound 6e was found to possess potent anti-leu-
kemic activity against leukemia cell line CCRF-CEM, non-small cell
lung cancer cell line HOP-92 and renal cancer cell line RXF 393
with GI50 values of 620, 650 and 900 nM, respectively, (Table 2).
Compounds 6a and 6e also exhibited significant growth inhibi-
tion against the following sub-panels of human cancer cell lines:
non-small cell lung cancer (GI50 values 0.65–1.45
lM); colon
cancer (GI50 values 1.12–2.06 M); melanoma (GI50 values
l
Scheme 1. Synthesis of carbamoylated MMB analogs 6a–6g: Reagents and conditions: (a) CH2Cl2, triethylamine, rt, 24 h; (b) CH2Cl2, heterocyclic amines, rt, 5–12 h.
Please cite this article in press as: Janganati, V.; et al. Bioorg. Med. Chem. Lett. (2014), http://dx.doi.org/10.1016/j.bmcl.2014.05.059

V. Janganati et al. / Bioorg. Med. Chem. Lett. xxx (2014) xxx–xxx
3
Table 2
Growth inhibition (GI50; l
M)b data for PTL (1), DMAPT (2) and carbamoylated MMB
analogs 6a–6e against a panel of human cancer cell lines
Panel/cell line
1a
2a
6a
6b
6c
6d
6e
GI50
GI50
GI50
GI50
GI50
GI50
GI50
Leukemia
CCRF-CEM
HL-60(TB)
K-562
MOLT-4
RPMI-8226
SR
7.94
5.01
19.9
15.8
7.94
NDc
1.99
1.58
2.51
3.16
2.51
ND
0.68
2.04
3.45
2.05
1.98
1.38
2.49
4.15
3.26
3.48
8.71
10.2
2.65
ND
ND
5.54
8.20
4.10
3.03
3.59
3.37
5.00
5.72
3.65
0.62
ND
ND
2.32
2.57
2.36
Figure 2. Cytotoxic mechanism of action of MMB analogs.
Non-small cell lung cancer
HOP-92
NCI-H522
12.5
5.01
10.0
2.51
1.45
1.25
2.25
1.78
2.25
1.64
2.30
2.13
0.65
1.26
Colon cancer
COLO 205
HCT-116
The above MMB analogs, like PTL and DMAPT, are inhibitors of
the NF B pathway, activators of the nuclear kinase JNK, and selec-
15.8
10.0
15.8
31.6
5.01
3.98
2.06
1.41
1.46
4.78
3.18
3.46
3.54
1.89
3.13
8.89
2.87
3.48
1.79
1.13
1.12
j
tively deplete glutathione levels in hematopoietic cancer stem
cells, leading to an increase in reactive oxygen species (ROS) and
subsequent apoptosis (Fig. 2).4,8,11 We have recently shown that
hematopoietic cancer stem cells have lower levels of reduced glu-
tathione (GSH) and increased levels of oxidized glutathione (GSSG)
when compared to normal stem cells, and are thus more vulnera-
ble to agents such PTL and MMB and its analogs that induce oxida-
tive stress through generation of ROS.11 Specifically, PTL and MMB
analogs inhibit several crucial enzymes in the glutathione pathway
(i.e., GCLC and GPX1) leading to severe depletion of cellular gluta-
thione and resulting in oxidative stress and apoptosis.
SW-620
CNS cancer
SF-539
SNB-75
19.9
50.1
2.51
ND
1.98
6.13
15.0
18.0
5.77
3.78
14.4
19.5
1.76
1.71
Melanoma
LOX IMVI
MALME-3M
M14
7.94
12.5
ND
10.0
ND
15.8
7.94
2.23
1.90
2.84
0.46
7.88
4.18
9.65
6.56
4.96
7.52
5.58
6.01
4.84
6.12
7.97
5.89
1.95
2.32
1.59
2.24
MDA-MB-435
ND
Ovarian cancer
IGROV1
OVCAR-3
19.9
19.9
19.9
12.5
2.31
1.69
4.09
8.41
14.4
ND
3.49
6.20
3.66
ND
In summary, we have reported on a series of novel carbamate
derivatives of MMB derived from heterocyclic and heteroaromatic
amines. Among these derivatives, compounds 6a and 6e have been
identified as potent anticancer agents with growth inhibition activ-
ities in the nanomolar range against a variety of hematological and
solid tumor cell lines. Analogs 6a and 6e exhibit promising anti-
leukemic activity against human leukemia cell line CCRF-CEM with
GI50 values of 680 and 620 nM, respectively. Compound 6a also
exhibits GI50 values of 460 and 570 nM against MDA-MB-435 mel-
anoma and MDA-MB-468 breast cancer cell lines, respectively, and
6e has GI50 values of 650 and 900 nM against HOP-92 non-small
cell lung and RXF 393 renal cancer cell lines, respectively. Further
structure–activity relationship studies will focus on the structural
optimization of these interesting lead analogs and on the molecu-
lar basis for their mechanism of action.
Renal cancer
ACHN
CAKI-1
RXF 393
TK-10
ND
15.8
12.5
15.8
3.16
1.79
2.03
1.20
2.60
3.80
6.86
4.08
3.11
2.75
2.88
2.22
3.78
3.74
4.31
3.00
3.93
1.75
1.99
0.90
2.51
10.0
12.5
ND
Prostate cancer
DU-145
ND
5.01
2.44
7.42
4.59
3.74
3.49
Breast cancer
MCF7
BT-549
T-47D
MDA-MB-468
15.8
ND
ND
ND
5.01
5.01
39.8
ND
1.62
2.69
3.07
0.57
3.91
4.75
4.86
2.30
2.85
2.60
6.19
3.22
3.54
4.99
6.32
3.26
1.33
1.47
2.23
1.29
GI50 values <1
l
M are bolded.
a
GI50 values obtained from NCI database.
GI50, concentration of analog (
ND not determined.
b
c
lM) that halves cellular growth.
Acknowledgments
0.46–2.84
breast cancer (GI50 values 0.57–3.07
l
M); renal cancer (GI50 values 0.90–2.60
l
M); and
We are grateful to the NIH/National Cancer Institute (Grant #
R01 CA158275) for supporting this research, to the Arkansas
Research Alliance for an Arkansas Scholar award and to the NCI
drug screening program.
lM) (Table 2).
We have determined the hydrolytic stability of the above five
carbamate derivatives in human plasma and have shown that com-
pounds 6b–6e have half-lives in the range 100–180 min, while
compound 6a has a much longer half-life of 8 h in human plasma.
Thus, we consider compounds 6b–6d to be anticancer agents that
are also metabolized by plasma esterases to the active parent com-
pound MMB, while compound 6a would be considered a more
potent anticancer agent than MMB that is likely not metabolized
to MMB in vivo.
The above results are interesting for a number of reasons: first,
the antileukemic activities of 6a and 6e against the sub-panel of
human leukemia cells indicates that these carbamate analogs of
MMB are more potent than the parent compound. Second, the
potent growth inhibition of human solid tumor cell lines by 6a
and 6e is the first report of such activities for MMB analogs.
Third, these interesting results indicate that structural modifi-
cation of the MMB molecule through appropriate carbamoylation
of the primary hydroxyl group can lead to an improvement in
the anticancer properties of MMB.
References and notes
1. Knight, D. W. Nat. Prod. Rep. 1995, 12, 271.
2. (a) Skalska, J.; Brookes, P. S.; Nadtochiy, S. M.; Hilchey, S. P.; Jordan, C. T.;
Guzman, M. L.; Maggirwar, S. B.; Briehl, M. M.; Bernstein, S. H. PLoS ONE 2009,
4, e8115; (b) Shama, N.; Crooks, P. A. Bioorg. Med. Chem. Lett. 2008, 18, 3870; (c)
Hewamana, S.; Alghazal, S.; Lin, T. T.; Clement, M.; Jenkins, C.; Guzman, M. L.;
Jordan, C. T.; Neelakantan, S.; Crooks, P. A.; Burnett, A. K.; Pratt, G.; Fegan, C.;
Rowntree, C.; Brennan, P.; Pepper, C. Blood 2008, 111, 4681; (d) Oka, D.;
Nishimura, K.; Shiba, M.; Nakai, Y.; Arai, Y.; Nakayama, M.; Takayama, H.;
Inoue, H.; Okuyama, A.; Nonomura, N. Int. J. Cancer 2007, 120, 2576.
3. (a) Bork, P. M.; Schmitz, M. L.; Kuhnt, M.; Escher, C.; Heinrich, M. FEBS Lett.
1997, 402, 85; (b) Wen, J.; You, K. R.; Lee, S. Y.; Song, C. H.; Kim, D. G. J. Biol.
Chem. 2002, 277, 38954; (c) Hehner, S. P.; Heinrich, M.; Bork, P. M.; Vogt, M.;
Ratter, F.; Lehmann, V.; Schulze-Osthoff, K.; Dröge, W.; Schmitz, M. L. J. Biol.
Chem. 1998, 273, 1288; (d) Sweeney, C. J.; Li, L.; Shanmugam, R.; Bhat-
Nakshatri, P. B.; Jayaprakasan, V.; Baldridge, L. A.; Gardner, T.; Smith, M.;
Nakshatri, H.; Cheng, L. Clin. Cancer Res. 2004, 10, 5501; (e) Yip-Schneider, M.
T.; Nakshatri, H.; Sweeney, C. J.; Marshall, M. S.; Wiebke, E. A.; Schmidt, C. M.
Please cite this article in press as: Janganati, V.; et al. Bioorg. Med. Chem. Lett. (2014), http://dx.doi.org/10.1016/j.bmcl.2014.05.059

4
V. Janganati et al. / Bioorg. Med. Chem. Lett. xxx (2014) xxx–xxx
Mol. Cancer Ther. 2005, 4, 587; (f) Nozaki, S.; Sledge, G. W.; Nakshatri, H.
Oncogene 2001, 20, 2178.
4. Guzman, M. L.; Rossi, R. M.; Karnischky, L.; Li, X.; Peterson, D. R.; Howard, D. S.;
Jordan, C. T. Blood 2005, 105, 4163.
412.1930, found 412.1933. ((1aR,7aS,10aS,10bS,E)-1a-methyl-8-methylene-9-
oxo-1a,2,3,6,7,7a,8,9,10a,10b-decahydrooxireno[20,30:9,10]cyclodeca[1,2-b]furan-
5-yl)methyl-(2-(pyrrolidin-1-yl)ethyl)carbamate (6b): 1H NMR (CDCl3,
400 MHz): d 6.22 (d, J = 3.2 Hz, 1H), 5.65 (t, J = 7 Hz, 1H), 5.55 (s, 1H), 4.62
(d, J = 11.6 Hz, 1H), 4.47 (d, J = 12.4 Hz, 1H), 3.82 (t, J = 9.6 Hz, 1H), 3.35 (s, 2 H),
2.90–2.83 (m, 2H), 2.70 (s, 4H), 2.42 (d, J = 9.6 Hz, 2H), 2.38–2.13 (m, 7H) 1.84
(s, 4H), 1.66 (t, J = 12 Hz, 1H), 1.52 (s, 3H), 1.13 (t, J = 11.6 Hz, 1H). 13C NMR
(CDCl3, 100 MHz): d 169.3, 156.1, 138.6, 135.3, 129.8, 120.1, 80.9, 67.0, 63.1,
59.8, 55.1, 53.8, 42.5, 38.9, 36.5, 25.6, 24.3, 23.6, 23.2, 17.8 ppm. HRMS (ESI) m/
5. (a) Guzman, M. L.; Jordan, C. T. Expert Opin. Biol. Ther. 2005, 5, 1147; (b) Dai, Y.;
Guzman, M. L.; Chen, S.; Wang, L.; Yeung, S. K.; Pei, X. Y.; Dent, P.; Jordan, C. T.;
Grant, S. Br. J. Haematol. 2010, 151, 70; (c) Kim, Y. R.; Eom, J. I.; Kim, S. J.; Jeung,
H. K.; Cheong, J. W.; Kim, J. S.; Min, Y. H. J. Pharmacol. Exp. Ther. 2010, 335, 389.
6. Deschler, B.; Lubbert, M. Cancer 2006, 107, 2099.
7. (a) Estey, E.; Dohner, H. Lancet 2006, 368, 1894; (b) Lowenberg, B.; Suciu, S.;
Archimbaud, E.; Haak, H.; Stryckmans, P.; De Cataldo, R.; Dekker, A. W.;
Berneman, Z. N.; Thyss, A.; Van der Lelie, J.; Sonneveld, P.; Visani, G.; Fillet, G.;
Hayat, M.; Hagemeijer, A.; Solbu, G.; Zittoun, R. J. Clin. Oncol. 1998, 16, 872; (c)
Tazzari, P. L.; Cappellini, A.; Ricci, F.; Evangelisti, C.; Papa, V.; Grafone, T.;
Martinelli, G.; Conte, R.; Cocco, L.; McCubrey, J. A.; Martelli, A. M. Leukemia
2007, 21, 427.
z
calcd
for
C
22H33N2O5
(M+H)+
405.2384,
found
405.2390.
((1aR,7aS,10aS,10bS,E)-1a-methyl-8-methylene-9-oxo-1a,2,3,6,7,7a,8,9,10a,10b-
decahydrooxireno[20,30:9,10]cyclodeca[1,2-b]furan-5-yl)methyl-(2-(pyridin-2-
yl)ethyl)carbamate (6c): 1H NMR (CDCl3, 400 MHz): d 8.50 (s, 1H), 7.62 (t,
J = 7.2 Hz, 1H), 7.15 (d, J = 7.6 Hz, 2H), 6.19 (s, 1H), 5.64 (t, J = 8 Hz, 1H), 5.56–
5.56 (m, 2H), 4.62 (d, J = 12.4 Hz, 1H), 4.44 (d, J = 12.8 Hz, 1H), 3.84 (t, J = 9.2 Hz,
1H), 3.60 (d, J = 6 Hz, 2H), 2.99–2.82 (m, 4H), 2.41–2.12 (m, 5H), 1.75 (s, 1H),
1.64 (d, J = 10.4 Hz, 1H), 1.52 (s, 3H), 1.07 (t, J = 13.6 Hz, 1H). 13C NMR (CDCl3,
100 MHz): d 169.3, 159.1, 156.0, 149.1, 138.6, 136.6, 135.5, 129.9, 123.4, 121.6,
120.2, 81.0, 67.0, 63.2, 59.8, 42.5, 40.1, 37.1, 36.6, 25.8, 24.4, 23.7, 17.9 ppm.
8. Pei, S.; Minhajuddin, M.; Callahan, K. P.; Balys, M.; Ashton, J. M.; Neering, S. J.;
Lagadinou, E. D.; Corbett, C.; Ye, H.; Liesveld, J. L.; O’Dwyer, K. M.; Li, Z.; Shi, L.;
Greninger, P.; Settleman, J.; Benes, C.; Hagen, F. K.; Munger, J.; Crooks, P. A.;
Becker, M. W.; Jordan, C. T. J. Biol. Chem. 2013, 288, 33542.
HRMS (ESI) m/z calcd for
C
23H29N2O5 (M+H)+ 413.2071, found 413.2073.
9. El-Feraly, F. S. Phytochemistry 1984, 23, 2372.
((1aR,7aS,10aS,10bS,E)-1a-methyl-8-methylene-9-oxo-1a,2,3,6,7,7a,8,9,10a,10b-
decahydrooxireno[20,30:9,10]-cyclodeca[1,2-b]furan-5-yl)-methyl(2-morpholino
ethyl)carbamate (6d): 1H NMR (CDCl3, 400 MHz): d 6.11(d, J = 3.6 Hz, 1H), 5.58
(t, J = 8 Hz, 1H), 5.43 (d, J = 2.8 Hz, 1H), 5.06 (s, 1H), 4.53 (d, J = 12.4 Hz, 1H),
4.34 (d, J = 12 Hz, 1H), 3.74 (t, J = 8.8 Hz, 1H), 3.56 (s, 4 H), 3.16 (t, J = 5.2 Hz,
2H), 2.78–2.72 (m, 2H), 2.32 (s, 8H), 2.21–2.00 (m, 4H), 1.55 (t, J = 10.4 Hz, 1H),
1.41 (s, 3H), 1.01 (t, J = 12 Hz, 1H). 13C NMR (CDCl3, 100 MHz): d 169.2, 155.9,
138.7, 135.4, 130.2, 120.0, 80.9, 67.0, 66.7, 63.1, 59.8, 57.2, 53.1, 42.5, 37.0,
36.5, 25.7, 24.4, 23.7, 17.8 ppm. HRMS (ESI) m/z calcd for C22H33N2O6 (M+H)+
421.2333, found 421.2331. ((1aR,7aS,10aS,10bS,E)-1a-methyl-8-methylene-9-
oxo-1a,2,3,6,7,7a,8,9,10a,10b-decahydrooxireno[20,30:9,10]cyclodeca[1,2-b]furan-
5-yl)methyl-(5-(methylthio)-1H-1,2,4-triazol-3-yl)carbamate (6e): 1H NMR
(CDCl3, 400 MHz): d 6.22 (s, 2H), 5.82 (t, J = 8 Hz, 1H), 5.50 (s, 1H), 4.90 (d,
J = 12.4 Hz, 1H), 4.81(d, J = 12.4 Hz, 1H), 3.85 (t, J = 9.6 Hz, 1H), 2.95 (s, 1H),
2.85 (d, J = 9.2 Hz, 1H), 2.48–2.15 (m, 8H), 1.70–1.53 (m, 6H), 1.13 (t,
10. Macias, F. A.; Galindo, J. C. G.; Massanet, G. M. Phytochemistry 1992, 31, 1969.
11. Shama, N.; ShanShan, P.; Fred, K. H.; Craig, T. J.; Peter, A. C. Bioorg. Med. Chem.
2011, 19, 1515.
12. Guzman, M. L.; Rossi, R. M.; Neelakantan, S.; Li, X.; Corbett, C. A.; Hassane, D. C.;
Becker, M. W.; Bennett, J. M.; Sullivan, E.; Lachowicz, J. L.; Vaughan, A.;
Sweeney, C. J.; Matthews, W.; Carroll, M.; Liesveld, J. L.; Crooks, P. A.; Jordan, C.
T. Blood 2007, 110, 4427.
13. Synthetic procedure and analytical data for the p-nitrophenyloxycarbonyl ester of
MMB (5): To the reaction mixture of MMB (100 mg, 0.378 mmol) and
triethylamine (45.8 mg, 0.454 mmol) in dichloromethane (2 mL), p-
nitrophenylchloroformate (76.3 mg, 0.378 mmol) was added at 0 °C. The
reaction mixture was stirred for 24 h at ambient temperature. When the
reaction was completed (monitored by TLC), water was added to the reaction
mixture and the aqueous mixture was extracted with dichloromethane. The
organic layer was washed with water, followed by brine solution, dried over
anhydrous Na2SO4 and concentrated to afford the crude product. The crude
product was purified by column chromatography (silica gel, 2% methanol in
dichloromethane) to afford compound 5 as a pale yellow solid. 1H NMR (CDCl3,
400 MHz): d 8.26 (d, J = 9.6 Hz, 2H), 7.37 (d, J = 9.8 Hz, 2H), 6.25 (s, 1H), 5.83 (t,
J = 8.4 Hz, 1H), 5.56 (s, 1H), 4.81(d, J = 12.8 Hz, 1H), 4.72 (d, J = 12.4 Hz, 1H),
3.86 (m, 1H), 2.85 (m, 2H), 2.56 (m, 7H), 1.77 (m, 2H), 1.55 (s, 1H), 1.16 (t,
J = 13.2 Hz, 1H). 13C NMR (CDCl3, 100 MHz): d 169.1, 155.2, 152.2, 145.4, 138.6,
133.6, 132.8, 125.3, 121.5, 120.3, 80.8, 71.5, 63.1, 59.8, 42.7, 36.4, 25.6, 24.9,
23.9, 17.9 ppm.
14. General synthetic procedure and analytical data for carbamate derivatives of MMB:
To the p-nitrophenyloxycarbonyl ester derivative of MMB (5) (70 mg,
0.16 mmol) in dichloromethane (2 mL), the appropriate amine (0.16 mmol)
was added at 0 °C. The reaction mixture was stirred for 18 h at ambient
temperature. When the reaction was completed (monitored by TLC), water was
added to the reaction mixture and the aqueous mixture was extracted with
dichloromethane. The organic layer was washed with water, followed by brine
solution, dried over anhydrous Na2SO4 and concentrated to afford the crude
product. The crude product was purified by column chromatography (silica gel,
5% methanol in dichloromethane) to afford the carbamate analogs (6a–g) as
white solids. ((1aR,7aS,10aS,10bS,E)-1a-methyl-8-methylene-9-oxo-1a,2,3,6,7,
7a,8,9,10a,10b-decahydrooxireno[20,30:9,10]cyclodeca[1,2-b]furan-5-yl)methyl-
4,4-difluoropiperidine-1-carboxylate (6a): 1H NMR (CDCl3), 400 MHz): d 6.27 (d,
J = 2.8 Hz, 1H), 5.67 (t, J = 8.4 Hz, 1H), 5.56 (s, 1H), 4.69 (d, J = 12.4 Hz, 1H), 4.52
(d, J = 12 Hz, 1H), 3, 87 (t, J = 9.6 Hz, 1H), 3.60 (br s, 4H), 2.87 (d, J = 9.2 Hz, 2H),
2.50–2.16 (m, 6H), 1.96 (br s, 4H), 1.71 (t, J = 10 Hz, 1H), 1.55 (s, 3H), 1.14 (t,
J = 12 Hz, 1H). 13C NMR (CDCl3, 100 MHz): d 169.4, 154.8, 138.7, 135.3, 129.9,
121.5, 120.5 (t, JCF = 5.3 Hz, 1C), 81.1, 67.7, 63.4, 60.0, 42.7, 41.0, 36.7, 34.0,
25.8, 24.4, 23.9, 18.1 ppm. HRMS (ESI) m/z calcd for C21H28F2NO5 (M+H)+
J = 12.4 Hz, 1H) ppm. 13C NMR (CDCl3, 100 MHz):
d 169.1, 163.1, 157.4,
149.9, 138.5, 133.3, 132.7, 120.2, 80.7, 70.1, 62.9, 59.7, 42.4, 36.2, 25.6, 24.3,
23.7, 17.8, 13.5 ppm. HRMS (ESI) m/z calcd for C19H25N4O5S (M+H)+ 421.1540,
found
421.1524.((1aR,7aS,10aS,10bS,E)-1a-methyl-8-methylene-9-oxo-
1a,2,3,6,7,7a,8,9,10a,10b-decahydrooxireno[20,30:9,10]cyclodeca[1,2-b]furan-5-
yl)methyl-(3-(1H-imidazol-1-yl)-propyl)carbamate (6f): 1H NMR (CDCl3,
400 MHz): d 7.56 (s, 1H), 7.09 (s, 1H), 6.95 (s, 1H), 6.26 (d, J = 3.6 Hz, 1H),
5.69 (t, J = 8 Hz, 1H), 5.56 (d, J = 3.2 Hz, 1H), 4.85 (s, 1H), 4.64 (d, J = 12.4 Hz,
1H), 4.51 (d, J = 12.4 Hz, 1H), 4.04 (t, J = 7.2 Hz, 2H), 3.88 (t, J = 9.2 Hz, 1H), 3.21
(d, J = 6 Hz, 2H), 2.93–2.85 (m, 2H), 2.47–2.16 (m, 7H), 2.03 (t, J = 6.4 Hz, 1H)
1.70 (t, J = 10.8 Hz, 1H), 1.55 (s, 3H), 1.15 (t, J = 12.4 Hz, 1H). 13C NMR (CDCl3,
100 MHz): d 169.5, 156.3, 138.9, 137.1, 135.3, 130.4, 129.6, 120.2, 118.8, 81.1,
67.3, 63.3, 60.0, 44.4, 42.7, 38.3, 36.7, 31.5, 25.8, 24.6, 23.8, 18.0 ppm. HRMS
(ESI) m/z calcd for
C
22H30N3O5 (M+H)+ 416.2180, found 416.2183.
((1aR,7aS,10aS,10bS,E)-1a-methyl-8-methylene-9-oxo-1a,2,3,6,7,7a,8,9,10a,10b-
decahydrooxireno[20,30:9,10]-cyclodeca[1,2-b]furan-5-yl)methyl-(3-
morpholinopropyl)carbamate (6g) 1H NMR (CDCl3, 400 MHz): d 6.23 (s, 1H), 5.74
(s, 1H), 5.65 (t, J = 8 Hz, 1H), 5.54 (s, 1H), 4.58 (d, J = 12 Hz, 1H), 4.48 (d,
J = 16 Hz, 1H), 3.85 (t, J = 9.2 Hz, 1H), 3.72 (s, 4H), 3.27 (s, 2H), 2.89–2.83 (m,
2H), 2.46–2.11 (m, 12H), 1.69 (t, J = 12 Hz 3H), 1.52 (s, 3H), 1.11 (t, J = 12 Hz,
1H). 13C NMR (CDCl3, 100 MHz): d 169.5, 156.3, 138.9, 135.7, 129.9, 120.4, 81.2,
67.0, 66.9, 63.4, 60.1, 57.4, 53.6, 42.7, 36.8, 25.9, 25.5, 24.6, 23.9, 18.1 ppm.
HRMS (ESI) m/z calcd for C23H35N2O6 (M+H)+ 435.2490, found 435.2482.
15. Neelakantan, S.; Shama, N.; Guzman, M. L.; Jordan, C. T.; Crooks, P. A. Bioorg.
Med. Chem. Lett. 2009, 19, 4346.
16. Boyd, M. R.; Paull, K. D. Drug Dev. Res. 1995, 34, 91.
17. Acton, E. M.; Narayanan, V. L.; Risbood, P. A.; Shoemaker, R. H.; Vistica, D. T.;
Boyd, M. R. J. Med. Chem. 1994, 37, 2185.
Please cite this article in press as: Janganati, V.; et al. Bioorg. Med. Chem. Lett. (2014), http://dx.doi.org/10.1016/j.bmcl.2014.05.059