Fluorinated isatin derivatives. Part 1: Synthesis of new N-substituted (S)-5-[1-(2-methoxymethylpyrrolidinyl)sulfonyl]isatins as potent caspase-3 and -7 inhibitors

Article abstract of DOI:10.1016/j.bmc.2009.02.048

A series of new N-substituted (S)-5-[1-(2-methoxymethylpyrrolidinyl)sulfonyl]isatin derivatives has been synthesized and tested as inhibitors of caspases-3 and -7, which are known to be downstream enzymes critical in the execution of apoptosis. N-Propyl-

Full text of DOI:10.1016/j.bmc.2009.02.048

Bioorganic & Medicinal Chemistry 17 (2009) 2680–2688
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Bioorganic & Medicinal Chemistry
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Fluorinated isatin derivatives. Part 1: Synthesis of new N-substituted
(S)-5-[1-(2-methoxymethylpyrrolidinyl)sulfonyl]isatins as potent caspase-3
and -7 inhibitors
Anil Kumar Podichetty a,c, Andreas Faust b,c, Klaus Kopka b,c, Stefan Wagner b,c, Otmar Schober b,
Michael Schäfers c, Günter Haufe a,c,
*
a Organisch-Chemisches Institut and International NRW Graduate School of Chemistry, Westfälische Wilhelms-Universität, Corrensstraße 40, D-48149 Münster, Germany
b Klinik und Poliklinik für Nuklearmedizin, Universitätsklinikum Münster, Albert-Schweitzer-Straße 33, D-48129 Münster, Germany
c European Institute of Molecular Imaging, Westfälische Wilhelms-Universität, Mendelstraße 11, D-48149 Münster, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of new N-substituted (S)-5-[1-(2-methoxymethylpyrrolidinyl)sulfonyl]isatin derivatives has
been synthesized and tested as inhibitors of caspases-3 and -7, which are known to be downstream
enzymes critical in the execution of apoptosis. N-Propyl- and N-butyl isatins, as well as the corresponding
terminal alcohols and regioisomeric fluorobutyl derivatives were shown to be excellent inhibitors having
different binding potencies for caspases-3 and -7. In contrast, the corresponding fluoroethyl and fluoro-
propyl compounds were about 100–1000 times less active. Fluorinated N-benzyl isatins as well as
trifluoroalkyl and difluoroalkyl derivatives were moderate inhibitors. However, isatins bearing different
alkylether groups at N-1 are very weak or not active as inhibitors of caspases-3 and -7.
Ó 2009 Elsevier Ltd. All rights reserved.
Received 11 November 2008
Revised 14 February 2009
Accepted 25 February 2009
Available online 1 March 2009
Keywords:
Apoptosis
Caspase inhibitors
Synthesis
Fluorine
Isatin derivatives
Substitution
1. Introduction
zymes with high potency. Besides peptidic inhibitors,6–8 the low
molecular weight pyrrolidinylsulfonyl isatins are known to possess
Programmed cell death, called apoptosis, is induced by either
receptor-mediated mechanisms, where a specific protein binds to
a receptor on the cell surface and triggers the cell death signal
(death receptor pathway), or direct damage of DNA by for example,
toxic substances or radiation, followed by mitochondrial induction
of the cell death program (mitochondrial pathway).1 Both mecha-
nisms trigger a complex cell death program—apoptosis—resulting
in a complete removal of the concerned cell without inflammatory
response. Downstream of the initial cellular process a class of
intracellular ‘death enzymes’, caspases (cysteinyl aspartate-specific
proteases) is activated.1–3 Apoptosis is known to be present in
many human diseases such as neurodegenerative diseases, cardio-
vascular diseases and others. Thus, apoptosis is an important target
for novel drugs.2,4 Therapeutic inhibition of caspase-3 and -7 has
been indeed shown to prevent cells from apoptosis.5
caspase inhibitory activity.9,10 Recently, the therapeutic action of
isatins as caspase inhibitors has been demonstrated.11 It has been
shown that the lead structure (S)-5-[1-(2-methoxymethylpyrrolid-
inyl)sulfonyl]isatin (1) perfectly fits into the active site of caspase-
3.5 Recently, we and others have also succeeded in the develop-
ment of new radiotracers (compounds suitable for application in
Positron Emission Tomography, PET) based on the isatin lead struc-
ture.12–15
Here, we report our recent results on the synthesis of a group of
new fluorinated and non-fluorinated 5-pyrrolidinylsulfonyl isatins
as caspase inhibitors. Some of them have been proven to exhibit
excellent inhibitory activity for caspases-3 and -7.
2. Results and discussion
2.1. Chemistry
Since caspases have been identified as suitable biological tar-
gets for anti-apoptotic strategies, it is reasonable to synthesize
compounds, which specifically bind to the active site of these en-
Based on the results of earlier work,5,12 we initially prepared
some basic non-fluorinated N-alkyl isatins 2b–2d, some polar vari-
ants 2f, 2h and 2i and several potential precursors 2e, 2g and 2j for
the preparation of fluorinated analogs 2k–2m in order to deter-
* Corresponding author. Tel.: +49 251 83 33281; fax: +49 251 83 39772.
E-mail address: haufe@uni-muenster.de (G. Haufe).
0968-0896/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2009.02.048

A. K. Podichetty et al. / Bioorg. Med. Chem. 17 (2009) 2680–2688
2681
mine their inhibition activity towards caspases-3 and -7 (Scheme
1, Table 1).
O
F
O
N
O
O
N
O
F
S
S
DAST
Compounds 1 and 2a have been prepared in previous work.5,12
Compounds 2b–2f and 2i were synthesized by treatment in dry
DMF of isatin 1 with the corresponding substituted alkyl bromides
in presence of anhydrous K2CO3 giving the target N-alkylation
products in 59–86% isolated yields. Subsequently, the hydroxyal-
kyl-isatin derivatives 2f and 2i were used as starting materials
for further functional group manipulations. The mesylate 2g and
the tosylate 2j were prepared by treatment of the alcohols 2f and
2i with mesyl- or tosyl chloride, respectively, in the presence of tri-
ethylamine. However, we failed to convert the mesylate 2g to the
terminal fluoride 2l by nucleophilic substitution under different
reaction conditions. Also, the direct treatment of the alcohol 2f
(prepared from 1 by reaction with 3-bromopropanol in presence
of half an equivalent of K2CO3), with diethylaminosulfur trifluoride
(DAST) failed to give 2l. Instead, this reaction proceeded both at the
terminal OH group and the C3 carbonyl function to give the tri-
fluoride 3b. Similarly, treatment of the N-propyl derivative 2c with
DAST gave the 3,3-difluoro isatin 3a (Scheme 2). Compound 2l fi-
O
O
CH2Cl2
-78°C
N
N
r.t.
MeO
MeO
X
Y
2c (X = H)
2i (X = OH)
3a (Y = H)
3b (Y = F)
Scheme 2. Substitution of oxygen functions with DAST.
nally was prepared by direct base mediated alkylation of 1 with 1-
bromo-3-fluoropropane.
The 4-fluorobut-1-yl compound 2m was found to be a highly
active inhibitor for caspases-3 and -7 (see below). Based on this re-
sult, we were interested in the synthesis of the regioisomers 2n
bearing a secondary fluorine substituent. Thus, we first prepared
the desired alkylation reagent, 3-fluorobutyltosylate from butan-
1,3-diol by tosylation of the primary OH group and subsequent
substitution of the secondary one with fluorine by treatment with
DAST (Scheme 3).
Also, N-alkenyl isatins bearing vinylic fluorine substituents
were synthesized. Treatment of compound 1 with 2-fluoroallyl-
tosylate16,17 in presence of K2CO3 gave the corresponding N-allyl
isatin 2o, while the alkylation with 4-bromo-1,1,2-trifluorobut-1-
ene gave 2p, each in 64% yield. Fluorinated benzyl substituents
were also introduced at the isatin nitrogen. In this way the p-flu-
oro- (2q), the p-trifluoromethyl- (2r) and the 3,5-bis-(trifluoro-
O
O
O
O
O
O
S
S
N
N
1. Alkylation
2. Functional group
manipulation
O
O
N
H
N
R
MeO
MeO
1
2
methyl)benzyl- (2s) isatins were synthesized from
treatment with the corresponding benzylbromides in presence of
NaH in dry DMF (Table 1).
1
by
Scheme 1. Alkylation of the lead isatin derivative 1.
In order to modify the polarity of the N-substituent, we also
introduced ether functions. Thus, applying a different molar ratio
of reactants, the reaction of 1 with 3-bromopropanol and K2CO3
(1:2:3) gave the hydroxyether 4, which was transformed to the
fluorinated dioxa derivative 5 by treatment with 1-bromo-2-fluo-
roethane and KH in DMF in the presence of catalytic amount of
Bu4NI. Furthermore, mesylation of 4 yielded compound 6, which
in turn was transformed to the terminal fluoride 7 by treatment
with Bu4NF in acetonitrile at elevated temperature (Scheme 4).
Also, treatment of compound 1 with epichlorohydrin in presence
of catalytic amounts of NaI provided the chlorohydrin 8 instead
of the desired epoxide (Scheme 4).
We also were interested in the effect of trifluoromethylated and
difluoromethylated N-alkyl groups on the inhibitory activity of
isatin derivatives. Thus, the alkylation of 1 with 1-bromo-3,3,3-tri-
fluoropropane, 1-bromo-4,4,4-trifluorobutane and 1-bromo-11,11-
difluoroundecane18 led to the target products 9a, 9b and 10,
respectively (Scheme 5).
Table 1
Yield and IC50 values of the lead compound
derivatives 2 and 3–10
1
and synthesized N-alkyl isatin
a
Compound
R
Yield (%)
IC50 (nM)
Caspase-3
Caspase-7
15
H
CH3
C2H5
n-C3H7
n-C4H9
47
82
59
65
86
120 26
2.4 0.3
183 48
5.3 3.8
29 13
170 47
304 73
319 59.8
58 15
2a12
2b
2c
2d
8.1 1.1
2e
2f
2g
2h
2i
C2H4CH2Cl
69
71
40
58
70
61
90 36
78 26
230 56
187 56
30 4.8
79 34
52 37
217 70
129 14
11 3.6
C2H4CH2OH
C2H4CH2OMs
C2H4COOH
C3H6CH2OH
C3H6CH2OTs
2j
56
3
29
5
2k
2l
2m
C2H4F
C2H4CH2F
C3H6CH2F
53
42
70
1840 166
5120 1150
41 17
2940 151
1440 306
28
6
2n
2o
2p
2q
2r
(CH2)2CHFCH3
CH2CF@CH2
(CH2)2CF@CF2
CH2C6H4-p-F
CH2C6H4-p-CF3
CH2C6H3-3,5-(CF3)2
70
44
64
62
38
58
25
499 239
83
191 107
82 67
3
6.8 1.9
266 96
178 67
44 19
OH
OH
7
11
9
2s
43
2
135 54
1. TsCl, Et3N
2. DAST
3a
3b
n-C3H7
C2H4CH2F
63
30
>100,000
6080 2240
>100,000
5640 4350
4
5
6
7
8
(CH2)3O(CH2)3OH
[(CH2)3O]2CH2CH2F
(CH2)3O(CH2)3OMs
(CH2)3O(CH2)3F
72
45
85
35
35
60,900 6660
9430 2870
>100,000
>100,000
13.3 8.9
113,000 11,100
19,400 2630
>100,000
>100,000
123 68
F
O
O
O
O
O
O
S
S
OTs
K2CO3
N
N
O
O
CH2CH(OH)CH2Cl
N
N
H
9a
9b
10
(CH2)2CF3
(CH2)3CF3
(CH2)10CHF2
47
88
40
359 210
40 18
100 19
111 24
MeO
MeO
213
6
F
2n
1
66 12
a
Values are the mean of three assays.
Scheme 3. Synthesis of isatin derivative 2n.

2682
A. K. Podichetty et al. / Bioorg. Med. Chem. 17 (2009) 2680–2688
O
O
O
O
N
O
S
Br
OH
MsCl
Et3N
CH2Cl2
O
O
O
O
K2CO3
N
N
N
H
OH
OMs
MeO
1
O
O
4
6
Cl
F
Br
KH
TBAF
cat. NaI
O
O
O
O
O
S
N
O
O
O
N
N
N
O
F
OH
MeO
F
O
O
Cl
8
5
7
Scheme 4. Synthesis of more polar isatin derivatives 4–8.
2.2. Structure–activity relationships (SAR)
weakly or not active as caspase inhibitors. Isatins 3a and 3b bear-
ing a difluoromethylene moiety instead of the 3-carbonyl function
completely lost the activity.
Among the simple N-alkyl isatins, the methyl12 and the propyl
derivatives 2a and 2c were shown to be excellent caspase-3 inhib-
itors with IC50 values as low as 2.4 or 5.3 nM, respectively, while
the n-butyl isatin 2d is an excellent caspase-7 inhibitor
(IC50 = 8.1 nM). In contrast, the ethyl derivative 2b was much less
active against both caspases. The N-alkyl isatins 2e–2j were mod-
erate inhibitors of caspases-3 and -7. Surprisingly, the fluoroethyl-
and fluoropropyl isatins 2k and 2l exhibited very weak inhibitory
activity in the micromolar range, while the 4-fluorobut-1-yl-isatin
2m is a rather potent inhibitor. The diastereomeric 3-fluorobut-1-
yl derivatives 2n are better inhibitors, particularly for caspase-7
with 3.5-fold higher inhibition potency as compared with cas-
pase-3. Replacement of a saturated by an unsaturated fluorinated
side chain led to a decrease of inhibitory activity. The 2-fluoroallyl
derivative 2o is a moderate inhibitor and the trifluoro derivative 2p
is only slightly more active. However, the fluorobenzylated com-
pounds 2q–2s are potent inhibitors. The p-trifluoromethyl deriva-
3. Conclusion
A series of fluorinated and non-fluorinated (S)-5-[1-(2-meth-
oxymethylpyrrolidinyl) sulfonyl]isatins has been prepared as po-
tential effector caspase inhibitors.
A broad variety of N-
substituents are tolerated without loss of caspase-3 and -7 inhibi-
tion potency. Among the substituted and unsubstituted alkyl
chains, the butyl compounds were shown to be the most active
caspase-3 and caspase-7 inhibitors. The 3-fluorobut-1-yl deriva-
tive 2n was one of the most active caspase inhibitors and even
more active than the 4-fluorobut-1-yl compound 2m. Also termi-
nal difluoroalkyl- and trifluoroalkyl compounds were shown to be
moderate inhibitors, while compounds bearing fluorinated or
non-fluorinated ether functions on N-1 are no inhibitors at all.
Fluorinated or trifluoromethylated N-benzyl compounds have
been shown to be moderate inhibitors of caspase-3 and cas-
pase-7.
tive 2r is
a very active caspase-7 inhibitor (IC50 = 11 nM).
Introduction of a trifluoromethyl group (compounds 9a and 9b)
led to decreased inhibition potency in comparison to the simple al-
kyl counterparts (compounds 2c and 2d), however, compound 9a
shows a ninefold higher inhibition potency for caspase-7 compared
with that of caspase-3. The long chain difluorinated compound 10
is a moderate inhibitor of caspases-3 and -7. All isatin derivatives
bearing an alkyl ether function at the nitrogen were shown to be
4. Experimental
4.1. General methods
All the chemicals, reagents and solvents for the synthesis of
compounds were analytical grade and used without further purifi-
cation, unless otherwise specified. 1H NMR (300.13 MHz and
400.13 MHz), 13C NMR (75.5 MHz and 100.63 MHz) and 19F NMR
(282.4 MHz) spectra were recorded in CDCl3 with TMS for 1H
NMR, CDCl3 for 13C NMR and CFCl3 for 19F NMR as the internal
standards. All chemical shift values were recorded in ppm (d). Ex-
act mass analyses were conducted on a Waters Quattro LC and a
Bruker MicroTof apparatus. All spectroscopic and analytical inves-
tigations were performed by staff members of the Organic Chemis-
try Institute, University of Münster. Silica coated aluminium foils
(Silica Gel 60 F254) from MERCK with 0.2 mm layer thickness were
used for thin layer chromatography (TLC). Column chromatogra-
phy was usually performed on silica gel (60–120 mesh) using suit-
able solvent mixtures. 1-Bromo-3-fluoropropane was prepared
from 3-bromopropanol with DAST19 and 1-tosyloxybutan-3-ol20
from butane-1,3-diol according to published protocols. 2-Fluoroal-
lyl tosylate17 and 11-bromo-1,1-difluoroundecane18 were synthe-
sized as described elsewhere.
O
O
O
N
O
O
O
CF3
S
S
Br
N
n
O
O
K2CO3
N
H
N
MeO
MeO
n
1
9a (n = 1)
9b (n = 2)
CF3
CHF2
Br
9
K2CO3
O
O
O
S
N
O
N
MeO
9
CHF2
10
Scheme 5. Synthesis of isatin derivatives 9a, 9b and 10.

A. K. Podichetty et al. / Bioorg. Med. Chem. 17 (2009) 2680–2688
2683
4.1.1. 4-Bromobutyl pivalate
stirred at À10 to 0 °C for 1.5–2.0 h followed by dilution with excess
CH2Cl2 (20 mL) and quenching with 0.1 N HCl solution (2 mL). The
two layers were separated and the organic layer was washed with
water (10 mL). The aqueous layer was again extracted with CH2Cl2
(10 mL) and the combined organic extracts were dried over MgSO4.
Filtration, followed by removal of the solvent in vacuo resulted in
the crude products, which were then purified by silica gel
chromatography.
To a cooled (À20 °C) solution of 4-bromobutanol (500 mg,
3.26 mmol) in dry CH2Cl2 (5 mL), pivaloyl chloride (0.44 mL,
3.59 mmol) followed by triethylamine (0.55 mL, 3.92 mmol) were
slowly added under argon atmosphere. The reaction mixture was
initially stirred at À15 to À20 °C for 1 h and then at ambient tem-
perature for 14–16 h. The work-up procedure was the same as
mentioned in procedure C (see below). The crude product was
purified by column chromatography (ethyl acetate/cyclohexane
1:19) to yield a colourless oil. Yield: 450 mg (58%). 1H NMR
(300 MHz, CDCl3): d 1.20 (s, 9H), 1.78–1.97 (m, 4H), 3.46 (t, 2H,
4.1.6. General procedure for the synthesis of gem-difluoro
derivatives (of isatin carbonyl moiety—procedure D)
3
3JH,H = 6.5 Hz), 4.11 (t, 2H, JH,H = 6.3 Hz) ppm. 13C NMR (75 MHz,
To a solution of the starting material in dry CH2Cl2 (3–6 mL),
fresh DAST (2.0–3.2 equiv) was added dropwise at À78 °C under
argon atmosphere and the reaction mixture was initially stirred
below À60 °C for 1 h and then at ambient temperature for 6–
14 h. The reaction mixture was then cooled to 0 °C, diluted with
an excess CH2Cl2 (10 mL) and then quenched with chilled satu-
rated NaHCO3 solution (10 mL). The aqueous layer was extracted
with CH2Cl2 (2 Â 10 mL) and the combined organic extracts were
dried over MgSO4. Filtration, followed by the removal of the sol-
vent in vacuo yielded the crude products, which were then purified
by silica gel chromatography.
CDCl3): d 27.2, 27.3, 29.4, 33.2, 38.8, 63.4, 178.5 ppm.
4.1.2. 1-Fluoro-3-tosyloxybutane
3-Tosyloxybutan-1-ol (200 mg, 0.81 mmol) was converted to 1-
fluoro-3-tosyloxybutane using fresh DAST (0.21 mL, 1.63 mmol) as
described in the general procedure C (see below) except that addi-
tion of DAST was carried out at 0 °C and the reaction mixture was
initially stirred at the same temperature for 30 min and then at
ambient temperature for 14 h followed by quenching with chilled
water and not with saturated NaHCO3 solution. The crude product
was purified by column chromatography (ethyl acetate/cyclohex-
ane 3:7) to yield a dense colourless oil. Yield: 170 mg (84%). 1H
4.1.6.1. (S)-1-Ethyl-5-[1-(2-methoxymethylpyrrolidinyl)sulfo-
nyl]isatin (2b). (S)-5-[1-(2-Methoxymethylpyrrolidinyl)sulfo-
nyl]isatin (1) (50 mg, 0.154 mmol) was converted to 2b using
anhydrous K2CO3 (53 mg, 0.386 mmol) and ethyl bromide
(0.022 mL, 0.308 mmol) as described in the general procedure A
and stirred for 14 h. The crude product was purified by column
chromatography (ethyl acetate/cyclohexane 3:2) to yield a golden
yellow coloured gummy solid. Yield: 32 mg (59%). 1H NMR
NMR (300 MHz, CDCl3):
d
1.34 (dd, 3H, 3JH,H = 6.2 Hz,
3JH,F = 23.9 Hz), 1.85–2.00 (m, 2H), 2.45 (s, 3H), 4.16 (t, 2H,
3JH,H = 6.0 Hz). 4.63–4.88 (m, 1H), 7.36 (d, 2H, JH,H = 8.0 Hz), 7.80
3
3
(d, 2H, JH,H = 8.3 Hz) ppm. 13C NMR (75 MHz, CDCl3): d 20.9 (d,
2
3
2JC,F = 22.2 Hz), 21.6, 36.2 (d, JC,F = 21.1 Hz), 66.5 (d, JC,F = 4.9 Hz),
1
86.9 (d, JC,F = 165.9 Hz), 127.9 (2C), 130.0 (2C), 132.7, 144.9 ppm.
19F NMR (282 MHz, CDCl3): d À177.1 (m, 1F) ppm. HRMS (ESI-
MicroTof): m/e 269.0606 (M+Na)+, calcd for C11H15FNaO3S
269.0618.
3
(300 MHz, CDCl3): d 1.36 (t, 3H, JH,H = 7.2 Hz), 1.60–1.72 (m, 2H),
1.86–1.95 (m, 2H), 3.09–3.17 (m, 1H), 3.35–3.48 (m, 2H), 3.37 (s,
2
3
3H), 3.60 (dd, 1H, JHb,Ha = 9.4 Hz, JHb,H = 3.8 Hz), 3.73–3.77 (m,
3
3
4.1.3. General procedure for the synthesis of N-1-alkylated
derivatives (procedure A)
1H), 3.88 (q, 2H, JH,H = 7.2 Hz), 7.05 (d, 1H, JH,H = 8.2 Hz), 8.05–
8.12 (m, 2H) ppm. 13C NMR (75 MHz, CDCl3): d 12.5, 24.1, 28.8,
35.5, 49.4, 59.1, 59.2, 74.9, 110.2, 117.4, 124.6, 133.7, 137.5,
153.4, 157.5, 182.2. HRMS (ESI-MicroTof): m/e 407.1244 (M+Na+-
CH3OH)+, calcd for C17H24N2NaO6S 407.1247.
To a solution of (S)-5-[1-(2-methoxymethylpyrrolidinyl)sulfo-
nyl]isatin (1) in dry DMF (3 mL) in a round-bottomed flask, anhy-
drous potassium carbonate (2.5–3.2 equiv) was added under
argon atmosphere and the reaction mixture was stirred at ambient
temperature for 30 min. An excess of the alkylating reagent, (2–
3 equiv) was slowly added and the reaction mixture was stirred
at ambient temperature for 6–48 h (depending on the type of elec-
trophile used) followed by dilution with 20 mL of ethyl acetate and
subsequent filtration after 15 min of further stirring. Removal of
the solvents in vacuo yielded the crude products, which were then
purified by silica gel chromatography.
4.1.6.2. (S)-5-[1-(2-Methoxymethylpyrrolidinyl)sulfonyl]-1-
propylisatin (2c). (S)-5-[1-(2-Methoxymethylpyrrolidinyl)sul-
fonyl]isatin (1) (50 mg, 0.154 mmol) was converted to 2c using
anhydrous K2CO3 (53 mg, 0.386 mmol) and n-propyl bromide
(0.028 mL, 0.308 mmol) as described in the general procedure A
and stirred for 8 h. The crude product was purified by column chro-
matography (ethyl acetate/cyclohexane 3:2) to yield a golden yel-
low coloured gummy solid. Yield: 37 mg (65%). 1H NMR (300 MHz,
3
4.1.4. General procedure for the synthesis of N-1-alkylated
derivatives (procedure B)
CDCl3):
d
1.04 (t, 3H, JH,H = 7.3 Hz), 1.64–1.80 (m, 4H,
3JH,H = 7.4 Hz), 1.89–1.95 (m, 2H), 3.11–3.15 (m, 1H), 3.35–3.48
(m, 2H), 3.37 (s, 3H), 3.60 (dd, 1H, JHb,Ha = 9.4 Hz, JHb,H = 3.8 Hz),
2
3
5-[1-(2-Methoxymethylpyrrolidinyl)sulfonyl]isatin (1) was
placed in a round-bottomed flask and dissolved in 50 mL of dry
dimethylformamide. Under an argon-atmosphere, 1.5 equiv of so-
dium hydride were added. During stirring for 30 min at ambient
temperature the solution turned dark red. An excess of the corre-
sponding benzylbromides were added and the reaction mixture
was stirred for further 2 or 3 h at ambient temperature. Removal
of the solvent in vacuo afforded the crude products, which were
purified by silica gel chromatography.
3
3.73–3.78 (m, 3H), 7.04 (d, 1H, JH,H = 8.3 Hz), 8.05 (d, 1H,
3
4
4JH,H = 1.6 Hz), 8.10 (dd, 1H, JH,H = 8.3 Hz, JH,H = 1.7 Hz) ppm. 13C
NMR (75 MHz, CDCl3): d 11.4, 20.7, 24.1, 28.8, 42.3, 49.4, 59.1,
59.2, 74.8, 110.4, 117.3, 124.6, 133.6, 137.5, 153.8, 157.8,
182.2 ppm. HRMS (ESI-MicroTof): m/e 421.1409 (M+Na+CH3OH)+,
calcd for C18H26N2NaO6S 421.1404.
4.1.6.3. (S)-1-Butyl-5-[1-(2-methoxymethylpyrrolidinyl)sulfo-
nyl]isatin (2d). (S)-5-[1-(2-Methoxymethylpyrrolidinyl)sulfo-
nyl]isatin (1) (30 mg, 0.093 mmol) was converted to 2d using
anhydrous K2CO3 (32 mg, 0.231 mmol) and n-butyl bromide
(0.02 mL, 0.185 mmol) as described in the general procedure A
and stirred for 6 h. The crude product was purified by column
chromatography (ethyl acetate/cyclohexane 3:2) to yield a golden
yellow coloured solid. Yield: 32 mg (86%). 1H NMR (300 MHz,
4.1.5. General procedure for the synthesis of mesylates
(procedure C)
To a solution of the alcohols 2f, 2i and 4 and 4-dimethylamino-
pyridine (DMAP, 0.05 equiv) in dry CH2Cl2 (5 mL), fresh MsCl
(1.2 equiv) followed by dry triethylamine (1.2 equiv) were added
at À10 °C under argon atmosphere. The reaction mixture was then

2684
A. K. Podichetty et al. / Bioorg. Med. Chem. 17 (2009) 2680–2688
3
CDCl3):
d
1.00 (t, 3H, JH,H = 7.3 Hz), 1.48 (sextuplet, 2H,
4.1.6.7. (S)-3-{5-[1-(2-Methoxymethylpyrrolidinyl)sulfonyl]-
2,3-dioxoindolin-1-yl}propanoic acid (2h). A mixture of a satu-
rated solution of aqueous NaHCO3 (0.4 mL, 0.131 mmol) and a 1 M
NaOCl solution (0.13 mL, 0.14 mmol) was added to a solution of
(S)-1-(3-hydroxypropyl)-5-[1-(2-methoxymethylpyrrolidinyl)sul-
fonyl]isatin (2f) (50 mg, 0.13 mmol), 2 M KBr solution (0.01 mL,
0.013 mmol) and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO,
0.0026 mmol) in CH2Cl2/H2O (1:1, 2 mL) at 0 °C and the reaction
mixture was stirred at the same temperature for 1.5–2 h followed
by quenching with MeOH (0.5 mL), neutralization with 10% HCl
and evaporation to dryness in vacuo. The crude product was then
purified by column chromatography (10% MeOH in CH2Cl2) to yield
a golden yellow coloured sticky solid. Yield: 30 mg (58%). 1H NMR
(300 MHz, CDCl3): d 1.60–1.74 (m, 2H), 1.85–1.94 (m, 2H), 2.67 (t,
3JH,H = 7.4 Hz), 1.65–1.76 (m, 4H), 1.89–1.95 (m, 2H), 3.10–3.18
(m, 1H), 3.35–3.47 (m, 2H), 3.37 (s, 3H), 3.60 (dd, 1H,
2JHb,Ha = 9.4 Hz, JHb,H = 3.8 Hz), 3.73–3.80 (m, 3H), 7.04 (d, 1H,
3
3JH,H = 8.3 Hz), 8.04 (d, 1H, 4JH,H = 1.7 Hz), 8.10 (dd, 1H,
3JH,H = 8.3 Hz, JH,H = 1.9 Hz) ppm. 13C NMR (75 MHz, CDCl3): d
4
13.6, 20.1, 24.1, 28.8, 29.2, 40.5, 49.3, 59.1, 59.2, 74.8, 110.4,
117.4, 124.5, 133.7, 137.5, 153.7, 157.8, 182.2 ppm. HRMS (ESI-
MicroTof):
C19H28N2NaO6S 435.1563.
m/e
435.1558
(M+Na+CH3OH)+,
calcd
for
4.1.6.4. (S)-1-(3-Chloropropyl)-5-[1-(2-methoxymethylpyrro-
lidinyl)sulfonyl]isatin (2e). (S)-5-[1-(2-Methoxymethylpyrro-
lidinyl)sulfonyl]isatin (1) (200 mg, 0.617 mmol) was converted to
2e using anhydrous K2CO3 (213 mg, 1.54 mmol) and 1-bromo-3-
chloropropane (0.02 mL, 0.185 mmol) as described in the general
procedure A and stirred for 6 h. The crude product was purified
by column chromatography (ethyl acetate/cyclohexane 3:2) to
yield a golden yellow coloured solid. Yield: 171 mg (69%). 1H
NMR (400 MHz, CDCl3): d 1.63–1.73 (m, 2H), 1.86–1.94 (m, 2H),
3
2H, JH,H = 7.4 Hz), 3.08–3.17 (m, 1H), 3.27–3.40 (m, 2H), 3.35 (s,
3H), 3.55–4.07 (m, 4H), 7.27 (m, 2H, isatinArH, CHCl3), 7.92–8.14
(m, 2H) ppm. 13C NMR (75 MHz, CDCl3): d 24.0, 28.7, 35.3, 39.8,
49.4, 59.1, 59.2, 74.9, 110.0, 117.4, 124.6, 133.5, 137.7, 153.3,
159.2, 170.8, 182.8 ppm. HRMS (ESI-MicroTof): m/e 419.0908
(M+Na)+, calcd for C17H20N2NaO7S 419.0883.
3
2.25 (quintet, 2H, JH,H = 6.5 Hz), 3.10–3.16 (m, 1H), 3.35–3.46
(m, 2H), 3.36 (s, 3H), 3.59 (dd, 1H, JHb,Ha = 9.4 Hz, JHb,H = 3.9 Hz),
2
3
4.1.6.8. (S)-1-(4-Hydroxybutyl)-5-[1-(2-methoxymethylpyrrolid
inyl)sulfonyl]isatin (2i). (S)-5-[1-(2-Methoxymethylpyrrolidi-
nyl)sulfonyl]isatin (1) (320 mg, 2.47 mmol) was converted to 2i
using anhydrous K2CO3 (272 mg, 1.97 mmol) and 4-bromobutyl
pivalate (700 mg, 2.96 mmol) as described in the general proce-
dure A and stirred for 12 h followed by dilution with an excess
water (10 mL) and complete extraction with CH2Cl2 (3 Â 10 mL).
The organic extracts were dried over MgSO4, filtered and the sol-
vent was removed completely in vacuo to afford the crude product.
It was dissolved in 1,4-dioxane (10 mL) and a 4 N HCl solution
(5 mL) was added. The above mixture was then heated at 80–
90 °C for 8–10 h followed by complete evaporation under vacuum.
The residue was purified by column chromatography (initially with
ethyl acetate/toluene 9:1) to separate the non-polar impurities fol-
lowed by final elution with 5% MeOH in CH2Cl2 to yield a golden
yellow coloured sticky solid. Yield: 275 mg (70%). 1H NMR
(300 MHz, CDCl3): d 1.65–1.93 (m, 9H), 3.09–3.17 (m, 1H), 3.35–
3
3.70 (t, 2H, JH,H = 6.0 Hz), 3.71–3.77 (m, 1H), 4.00 (t, 2H,
3JH,H = 7.0 Hz), 7.20 (d, 1H, 3JH,H = 8.3 Hz), 8.03 (d, 1H,
3
4
4JH,H = 1.8 Hz), 8.11 (dd, 1H, JH,H = 8.3 Hz, JH,H = 1.9 Hz) ppm. 13C
NMR (100 MHz, CDCl3): d 24.1, 28.8, 30.0, 38.2, 42.0, 49.3, 59.1,
59.2, 74.8, 110.4, 117.4, 124.6, 134.0, 137.6, 153.4, 158.0,
181.8 ppm. HRMS (ESI-MicroTof): m/e 423.0743 (M+Na)+, calcd
for C17H21ClN2NaO5S 423.0752.
4.1.6.5. (S)-1-(3-Hydroxypropyl)-5-[1-(2-methoxymethylpyrro-
lidinyl)sulfonyl]isatin (2f). (S)-5-[1-(2-Methoxymethylpyrro-
lidinyl)sulfonyl]isatin (1) (800 mg, 2.47 mmol) was converted to
2f using anhydrous K2CO3 (187 mg, 1.358 mmol) and 3-bromopro-
panol (0.65 mL, 7.40 mmol) as described in the general procedure
A and stirred for 48 h. The crude product was purified by column
chromatography (5% MeOH in CH2Cl2) to yield a golden yellow col-
oured solid. Yield: 675 mg (71%). 1H NMR (300 MHz, CDCl3): d
1.66–2.09 (m, 7H), 3.07–3.19 (m, 1H), 3.35–3.48 (m, 2H), 3.37 (s,
2
3.44 (m, 2H), 3.37 (s, 3H), 3.61 (dd, 1H, JHb,Ha = 9.4 Hz,
2
3
3
3H), 3.60 (dd, 1H, JHb,Ha = 9.4 Hz, JHb,H = 3.9 Hz), 3.70–3.83 (m,
3JHb,H = 3.8 Hz), 3.72–3.79 (m, 3H, JH,H = 6.0 Hz), 3.85 (t, 2H,
3
3
3H, JH,H = 5.6 Hz), 3.96 (t, 2H, JH,H = 6.6 Hz), 7.17 (d, 1H,
3JH,H = 7.2 Hz), 7.08 (d, 1H, 3JH,H = 8.3 Hz), 8.05 (d, 1H,
3JH,H = 8.3 Hz), 8.05 (d, 1H, 4JH,H = 1.7 Hz), 8.11 (dd, 1H,
4JH,H = 1.7 Hz), 8.10 (dd, 1H, JH,H = 8.3 Hz, JH,H = 1.9 Hz) ppm. 13C
NMR (75 MHz, CDCl3): d 23.9, 24.1, 28.8, 29.4, 40.5, 49.4, 59.1,
59.2, 62.0, 74.9, 110.5, 117.4, 124.6, 133.8, 137.5, 153.6, 157.9,
182.1 ppm. HRMS (ESI-MicroTof): m/e 419.1265 (M+Na)+, calcd
for C18H24N2NaO6S 419.1247.
3
4
3JH,H = 8.3 Hz, JH,H = 1.9 Hz) ppm. 13C NMR (75 MHz, CDCl3): d
4
24.1, 28.8, 29.7, 37.4, 49.3, 59.0, 59.1, 59.2, 74.8, 110.6, 117.4,
124.5, 134.0, 137.6, 153.6, 158.4, 182.0 ppm. HRMS (ESI-MicroTof):
m/e 437.1358 (M+Na)+, calcd for C18H26N2NaO7S 437.1353.
4.1.6.6. (S)-3-{5-[1-(2-Methoxymethylpyrrolidinyl)sulfonyl]-2,3-
dioxoindolin-1-yl}propyl methanesulfonate (2g). (S)-1-(3-
Hydroxypropyl)-5-[1-(2-methoxymethylpyrrolidinyl)-sulfonyl]
isatin (2f) (100 mg, 0.26 mmol) was converted to 2g using DMAP
(1.5 mg, 0.013 mmol), fresh MsCl (0.024 mL, 0.31 mmol) and dry
triethylamine (0.043 mL, 0.314 mmol) as described in the general
procedure C and stirred for 1 h. The crude product was purified
by column chromatography (1% MeOH in CH2Cl2) to yield a dull
yellow coloured gummy solid. Yield: 48 mg (40%). 1H NMR
(300 MHz, CDCl3): d 1.62–1.94 (m, 4H), 2.18–2.24 (m, 2H), 3.03–
3.15 (m, 1H), 3.06 (s, 3H), 3.35–3.47 (m, 2H), 3.37 (s, 3H), 3.60
4.1.6.9. (S)-4-{5-[1-(2-Methoxymethylpyrrolidinyl)sulfonyl]-2,3-
dioxoindolin-1-yl}butyl 4-methyl-benzenesulfonate (2j). (S)-
1-(4-Hydroxybutyl)-5-[1-(2-methoxymethylpyrrolidinyl)-sulfonyl]
isatin (2i) (230 mg, 0.58 mmol) was converted to 2j using DMAP
(14.0 mg, 0.116 mmol), fresh TsCl (166 mg, 0.87 mmol) and dry tri-
ethylamine (0.12 mL, 0.87 mmol) as described in the general proce-
dure C exceptthatthereaction mixturewasinitially stirredat 0 °C for
30 min and then at ambient temperature for 12 h. Also, after dilution
with CH2Cl2, the reaction mixture was washed with water and not
quenched with 0.1 N HCl solution as mentioned in the general proce-
dure. The crude product was purified by column chromatography
(ethyl acetate/toluene 7:3) to yield a light orange coloured gummy
solid. Yield: 195 mg (61%). 1H NMR (300 MHz, CDCl3): d 1.67–1.94
(m, 8H), 2.45 (s, 3H), 3.09–3.17 (m, 1H), 3.36–3.48 (m, 2H), 3.37 (s,
3H), 3.61 (dd, 1H, 2JHb,Ha = 9.4 Hz, 3JHb,H = 3.8 Hz), 3.72–3.81 (m, 3H,
3JH,H = 6.7 Hz), 4.09 (t, 2H, 3JH,H = 5.6 Hz), 7.07 (d, 1H, 3JH,H = 8.3 Hz),
2
3
(dd, 1H, JHb,Ha = 9.4 Hz, JHb,H = 3.9 Hz), 3.73–3.78 (m, 1H), 3.97
3
3
(t, 2H, JH,H = 6.9 Hz), 4.34 (t, 2H, JH,H = 5.7 Hz), 7.11 (d, 1H,
3JH,H = 8.3 Hz), 8.08 (d, 1H, 4JH,H = 1.7 Hz), 8.14 (dd, 1H,
3JH,H = 8.3 Hz, JH,H = 1.9 Hz) ppm. 13C NMR (75 MHz, CDCl3): d
4
24.1, 27.2, 28.8, 37.3, 37.6, 49.4, 59.1, 59.2, 66.9, 74.8, 110.4,
117.4, 124.8, 134.2, 137.7, 153.6, 158.7, 181.5 ppm. HRMS (ESI-
MicroTof): m/e 483.0871 (M+Na)+, calcd for C18H24N2NaO8S2
483.0866.
3
3
7.36 (d, 2H, JH,H = 8.0 Hz), 7.77 (d, 2H, JH,H = 8.3 Hz), 8.06 (d, 1H,
3
4
4JH,H = 1.8 Hz), 8.12 (dd, 1H, JH,H = 8.3 Hz, JH,H = 1.9 Hz) ppm. 13C
NMR (75 MHz, CDCl3): d 21.7, 23.4, 24.1, 26.2, 28.8, 39.9, 49.4, 59.1,

A. K. Podichetty et al. / Bioorg. Med. Chem. 17 (2009) 2680–2688
2685
59.2, 69.3, 74.9, 110.5, 117.4, 124.7, 127.9 (2C), 130.0 (2C), 132.6,
133.9, 137.6, 145.1, 153.3, 157.9, 181.9 ppm. HRMS (ESI-MicroTof):
m/e 573.1331 (M+Na)+, calcd for C25H30N2NaO8S2 573.1336.
4.1.6.13. (S)-1-(3-Fluorobutyl)-5-[1-(2-methoxymethylpyrrolid-
inyl)sulfonyl]isatin (2n). (S)-5-[1-(2-Methoxymethylpyrrolidi-
nyl)sulfonyl]isatin (1) (35 mg, 0.108 mmol) was converted to 2n
using anhydrous K2CO3 (37 mg, 0.27 mmol) and 3-fluorobutyl 4-
methylbenzenesulfonate (53 mg, 0.216 mmol) as described in the
general procedure A and stirred for 14 h. The crude product was
purified by column chromatography (ethyl acetate/toluene 3:2)
to yield an orange-yellow coloured solid. Yield: 31 mg (70%). 1H
4.1.6.10. (S)-1-(2-Fluoroethyl)-5-[1-(2-methoxymethylpyrrolid-
inyl)sulfonyl]isatin (2k). (S)-5-[1-(2-Methoxymethylpyrrolidi-
nyl)sulfonyl]isatin (1) (50 mg, 0.154 mmol) was converted to 2k
using anhydrous K2CO3 (53 mg, 0.385 mmol) and freshly distilled
1-bromo-2-fluoroethane (0.023 mL, 0.308 mmol) as described in
the general procedure A and stirred for 14 h. The crude product
was purified by column chromatography (ethyl acetate/cyclohex-
ane 7:3) to yield an orange-yellow coloured solid. Yield: 31 mg
(53%). 1H NMR (300 MHz, CDCl3): d 1.60–1.75 (m, 2H), 1.85–1.96
(m, 2H), 3.08–3.16 (m, 1H), 3.34–3.47 (m, 2H), 3.36 (s, 3H), 3.60
NMR (300 MHz, CDCl3):
d
1.45 (dd, 3H, 3JH,H = 6.2 Hz,
3JH,F = 24.0 Hz), 1.65–1.74 (m, 2H), 1.85–2.09 (m, 4H), 3.09–3.17
(m, 1H), 3.35–3.48 (m, 2H), 3.36 (s, 3H), 3.60 (dd, 1H,
3
2JHb,Ha = 9.4 Hz, JHb,H = 3.8 Hz), 3.72–3.79 (m, 1H), 3.95 (t, 2H,
3
3JH,H = 7.3 Hz), 4.64–4.86 (m, 1H), 7.12 (d, 1H, JH,H = 8.3 Hz), 8.05
4
3
4
(d, 1H, JH,H = 1.7 Hz), 8.11 (dd, 1H, JH,H = 8.3 Hz, JH,H = 1.9 Hz)
2
3
2
(dd, 1H, JHb,Ha = 9.4 Hz, JHb,H = 3.9 Hz), 3.71–3.78 (m, 1H), 4.11
ppm. 13C NMR (75 MHz, CDCl3): d 21.0 (d, JC,F = 22.3 Hz), 24.1,
28.8, 34.5 (d, JC,F = 20.8 Hz), 37.1 (d, JC,F = 4.1 Hz), 49.4, 59.1,
3
3
2
2
3
(dt, 2H, JH,H = 4.6 Hz, JH,F = 26.9 Hz), 4.80 (dt, 2H, JH,F = 47.0 Hz,
3JH,H = 4.5 Hz), 7.20 (d, 1H, 3JH,H = 8.3 Hz), 8.05 (d, 1H,
59.2, 74.8, 88.4 (d, JC,F = 166.0 Hz), 110.4, 117.3, 124.6, 133.8,
1
4JH,H = 1.5 Hz), 8.10 (dd, 1H, JH,H = 8.3 Hz, JH,H = 1.9 Hz) ppm. 13C
137.6, 153.5, 157.9, 181.9 ppm. 19F NMR (282 MHz, CDCl3): d
À175.6 (m, 1F, 2JH,F = 51.1 Hz, 3JH,F = 24.0 Hz, 3JH,F = 27.3 Hz). HRMS
(ESI-MicroTof): m/e 421.1204 (M+Na)+, calcd for C18H23FN2NaO5S
421.1205.
3
4
2
NMR (75 MHz, CDCl3): d 24.1, 28.8, 41.4 (d, JC,F = 20.4 Hz), 49.4,
1
5
59.1, 59.2, 74.8, 81.9 (d, JC,F = 171.8 Hz), 111.3 (d, JC,F = 4.4 Hz),
117.3, 124.5, 134.0, 137.5, 153.7, 157.9, 181.5 ppm. 19F NMR
2
3
(282 MHz, CDCl3): d À220.1 (dtt, 1F, JH,F = 53.8 Hz, JH,F = 26.8 Hz,
6JH,F = 1.0 Hz) ppm. HRMS (ESI-MicroTof): m/e 425.1148 (M+Na+-
CH3OH)+, calcd for C17H23FN2NaO6S 425.1153.
4.1.6.14. (S)-1-(2-Fluoroallyl)-5-[1-(2-methoxymethylpyrrolidi-
nyl)sulfonyl]isatin (2o). (S)-5-[1-(2-Methoxymethylpyrrolidi-
nyl)sulfonyl]isatin (1) (100 mg, 0.3 mmol) was converted to 2o
using anhydrous K2CO3 (106 mg, 0.77 mmol) and 2-fluoroallyl tos-
ylate (212 mg, 0.925 mmol) as described in the general procedure
A and stirred for 14 h. The crude product was purified by column
chromatography (ethyl acetate/toluene 1:1) to yield a golden yel-
low coloured gummy solid. Yield: 52 mg (44%). 1H NMR
(300 MHz, CDCl3): d 1.68–1.69 (m, 2H), 1.91–1.98 (m, 2H), 3.10–
3.15 (m, 1H), 3.35–3.46 (m, 2H), 3.36 (s, 3H), 3.59 (dd, 1H,
4.1.6.11. (S)-1-(3-Fluoropropyl)-5-[1-(2-methoxymethylpyrro-
lidinyl)sulfonyl]isatin (2l). (S)-5-[1-(2-Methoxymethylpyrro-
lidinyl)sulfonyl]isatin (1) (70 mg, 0.216 mmol) was converted to 2l
using anhydrous K2CO3 (74.5 mg, 0.540 mmol) and crude 1-bro-
mo-3-fluoropropane (0.06 mL, 0.648 mmol) as described in the gen-
eral procedure A and stirred for 36 h. The crude product was purified
by column chromatography (ethyl acetate/cyclohexane 3:2) to yield
an orange-yellow coloured solid. Yield: 35 mg (42%). 1H NMR
(300 MHz, CDCl3): d 1.61–1.76 (m, 2H), 1.85–1.96 (m, 2H), 2.20 (d
3
2JHb,Ha = 9.4 Hz, JHb,H = 3.7 Hz), 3.70–3.79 (m, 1H), 4.51 (d, 2H,
2
3
3JH,F = 13.0 Hz), 4.64–4.81 (dd, 1H, JHa,Hb = 3.5 Hz, JHa,F = 47.4 Hz),
3
3
2
3
of quintet, 2H, JH,H = 6.7 Hz, JH,F = 27.5 Hz), 3.10–3.18 (m, 1H),
4.94 (dd, 1H, JHb,Ha = 3.6 Hz, JHb,F = 16.0 Hz), 7.14 (d, 1H,
2
3.35–3.48 (m, 2H), 3.37 (s, 3H), 3.60 (dd, 1H, JHb,Ha = 9.4 Hz,
3JH,H = 7.8 Hz), 8.08–8.11 (m, 2H) ppm. 13C NMR (75 MHz, CDCl3):
3JHb,H = 3.9 Hz), 3.72–3.80 (m, 1H), 3.96 (t, 2H, JH,H = 7.0 Hz), 4.60
d 24.2, 28.8, 40.9 (d, JC,F = 33.6 Hz), 49.4, 59.1, 59.2, 74.8, 95.0 (d,
3
2
2
3
3
(dt, 2H, JH,F = 47.0 Hz, JH,H = 5.4 Hz), 7.11 (d, 1H, JH,H = 8.3 Hz),
8.07 (d, 1H, 4JH,H = 1.7 Hz), 8.12 (dd, 1H, 3JH,H = 8.3 Hz, 4JH,H = 1.9 Hz)
ppm. 13C NMR (75 MHz, CDCl3): d 24.1, 28.4 (d, 2JC,F = 20.0 Hz), 28.8,
37.2 (d, 3JC,F = 4.3 Hz), 49.4, 59.1, 59.2, 74.8, 81.0 (d, 1JC,F = 166.1 Hz),
110.3, 117.4, 124.7, 134.0, 137.6, 153.5, 158.0, 181.8 ppm. 19F NMR
(282 MHz, CDCl3): d À221.2 (tt, 1F, JH,F = 55.1 Hz, JH,F = 27.6 Hz)
ppm. HRMS (ESI-MicroTof): m/e 407.1049 (M+Na)+, calcd for
C17H21FN2NaO5S 407.1047.
2JC,F = 16.9 Hz), 111.1, 117.4, 124.6, 134.3, 137.5, 152.8, 157.3,
158.1 (d, JC,F = 262.2 Hz), 181.1 ppm. 19F NMR (282 MHz, CDCl3):
1
3
3
d
À102.4 to À102.7 (m, 1F, JHa,F = 47.4 Hz, JHb,F = 28.6 Hz,
3JH,F = 12.9 Hz) ppm. HRMS (ESI-MicroTof): m/e 437.1149 (M+Na+-
CH3OH)+, calcd for C18H23FN2NaO6S 437.1153.
2
3
4.1.6.15. (S)-5-[1-(2-Methoxymethylpyrrolidinyl)sulfonyl]-1-
(3,4,4-trifluorobut-3-enyl)isatin
(2p). (S)-5-[1-(2-Meth-
oxymethylpyrrolidinyl)sulfonyl]isatin (1) (200 mg, 0.617 mmol)
was converted to 2p using anhydrous K2CO3 (210 mg, 1.54 mmol)
and 4-bromo-1,1,2-trifluorobut-1-ene (0.14 mL, 1.234 mmol) as
described in the general procedure A and stirred at 35–40 °C for
18 h. The crude product was purified by column chromatography
(ethyl acetate/cyclohexane 7:3) to yield a deep orange coloured so-
lid. Yield: 171 mg (64%). 1H NMR (400 MHz, CDCl3): d 1.64–1.71
(m, 2H), 1.89–1.94 (m, 2H), 2.71–2.81 (m, 2H), 3.13–3.19 (m,
4.1.6.12. (S)-1-(4-Fluorobutyl)-5-[1-(2-methoxymethylpyrrolid-
inyl)sulfonyl]isatin (2m). (S)-5-[1-(2-Methoxymethylpyrrolidi-
nyl)sulfonyl]isatin (1) (50 mg, 0.154 mmol) was converted to 2m
using anhydrous K2CO3 (53 mg, 0.385 mmol) and 1-bromo-4-fluo-
robutane (0.033 mL, 0.308 mmol) as described in the general pro-
cedure A and stirred for 10 h. The crude product was purified by
column chromatography (ethyl acetate/cyclohexane 1:1) to yield
an orange-yellow coloured solid. Yield: 43 mg (70%). 1H NMR
(300 MHz, CDCl3): d 1.64–1.95 (m, 8H), 3.11–3.17 (m, 1H), 3.35–
2
1H), 3.36–3.47 (m, 2H), 3.36 (s, 3H), 3.59 (dd, 1H, JHb,Ha = 9.4 Hz,
3
3JHb,H = 3.9 Hz), 3.74–3.80 (m, 1H), 4.02 (t, 2H, JH,H = 6.7 Hz), 7.05
2
3
4
3.47 (m, 2H), 3.37 (s, 3H), 3.60 (dd, 1H, JHb,Ha = 9.4 Hz,
(d, 1H, JH,H = 8.3 Hz), 8.08 (d, 1H, JH,H = 1.7 Hz), 8.13 (dd, 1H,
3JHb,H = 3.9 Hz), 3.71–3.79 (m, 1H), 3.86 (t, 2H, JH,H = 6.9 Hz), 4.54
3JH,H = 8.3 Hz, JH,H = 1.9 Hz) ppm. 13C NMR (100 MHz, CDCl3): d
3
4
2
3
3
2
3
(dt, 2H, JH,F = 47.0 Hz, JH,H = 5.3 Hz), 7.07 (d, 1H, JH,H = 8.3 Hz),
24.1, 24.5 (dd, JC,F = 22.0 Hz, JC,F = 2.4 Hz), 28.8, 36.9 (m,
3JC,F = 2.6 Hz), 49.4, 59.1, 59.2, 74.8, 109.9, 117.4, 124.8, 134.4,
137.6, 152.9, 157.7, 181.3 ppm, (signals for the two non-proton-
ated carbons (–CF@CF2) are not detectable). 19F NMR (282 MHz,
8.05 (d, 1H, 4JH,H = 1.8 Hz), 8.10 (dd, 1H, 3JH,H = 8.3 Hz,
4JH,H = 1.9 Hz) ppm. 13C NMR (75 MHz, CDCl3):
d 23.5 (d,
3JC,F = 4.0 Hz), 24.1, 27.6 (d, JC,F = 20.1 Hz), 28.8, 40.2, 49.4, 59.1,
2
1
2
3
59.2, 74.8, 83.3 (d, JC,F = 165.6 Hz), 110.4, 117.4, 124.6, 133.8,
CDCl3): d À100.9 (dd, 1F, JFb,Fc = 81.1 Hz, JFb,Fa = 33.0 Hz), À121.9
2 3 4
137.5, 153.4, 157.8, 182.0 ppm. 19F NMR (282 MHz, CDCl3): d
(ddt, 1F, JFc,Fb = 81.1 Hz, JFc,Fa = 115.0 Hz, JH,Fc = 3.8 Hz), À174.6
3 3 3
2
3
À219.4 (tt, 1F, JH,F = 53.1 Hz, JH,F = 26.6 Hz) ppm. HRMS (ESI-
MicroTof): m/e 453.1460 calcd for
(M+Na+CH3OH)+,
C19H27FN2NaO6S 453.1465.
(ddt, 1F, JH,Fa = 21.6 Hz, JFa,Fb = 33.0 Hz, JFa,Fc = 115.0 Hz) ppm.
HRMS (ESI-MicroTof): m/e 487.1114 (M+Na+CH3OH)+, calcd for
C19H23F3N2NaO6S 487.1121.

2686
A. K. Podichetty et al. / Bioorg. Med. Chem. 17 (2009) 2680–2688
4.1.6.16. (S)-4-Fluorobenzyl-5-[1-(2-methoxymethylpyrrolidinyl)
sulfonyl]isatin (2q). (S)-5-[1-(2-Methoxymethylpyrrolidi-
umn chromatography (ethyl acetate/cyclohexane 1:1) to yield an
off-white coloured gummy solid. Yield: 20 mg (63%). 1H NMR
(400 MHz, CDCl3): d 1.01 (t, 3H, JH,H = 7.4 Hz), 1.66–1.79 (m, 4H),
3
nyl)sulfonyl]isatin (1) (324 mg, 1 mmol) was converted to 2q using
sodium hydride (60 mg, 1.5 mmol, 60% in mineral oil) and 4-fluo-
robenzyl bromide (0.37 mL, 567 mg, 3 mmol) as described in the
general procedure B. The crude orange product was purified by sil-
ica gel chromatography (cyclohexane/ethyl acetate 1:1) and
yielded 2q as a yellow solid. Yield: 298 mg (0.69 mmol, 69%). 1H
NMR (300 MHz, CDCl3): d 1.64–1.69 (m, 2H), 1.85–1.90 (m, 2H),
3.13–3.19 (m, 1H), 3.33 (s, 3H), 3.34–3.39 (m, 2H), 3.54 (dd, 1H,
1.89–2.08 (m, 2H), 3.11–3.19 (m, 1H), 3.36–3.48 (m, 2H), 3.37 (s,
2
3
3H), 3.61 (dd, 1H, JHb,Ha = 9.4 Hz, JHb,H = 3.9 Hz), 3.72 (t, 2H,
3JH,H = 7.2 Hz), 3.75–3.81 (m, 1H), 7.03 (dd, 1H, JH,H = 8.0 Hz,
3
5JH,H = 0.8 Hz), 8.00–8.03 (m, 2H) ppm. 13C NMR (100 MHz, CDCl3):
d 11.2, 20.5, 24.1, 28.8, 42.2, 49.3, 59.1, 59.2, 74.9, 109.8, 111.0 (t,
1JC,F = 251.3 Hz), 121.0 (t, 2JC,F = 23.5 Hz), 124.3, 133.6, 133.7, 147.1
(t, JC,F = 6.6 Hz), 165.2 (t, JC,F = 30.2 Hz) ppm. 19F NMR (282 MHz,
3
2
3
5
2JHb,Ha = 9.4 Hz, JHb,H = 3.9 Hz), 3.71–3.76 (m, 1H), 4.94 (s, 2H),
CDCl3): d À112.6 (d, 2F, JH,F = 1.2 Hz) ppm. HRMS (ESI-MicroTof):
3
6.91 (d, 1H, JH,H = 8.3 Hz), 7.03–7.09 (m, 2H), 7.31–7.36 (m, 2H),
m/e 411.1160 (M+Na)+, calcd for C17H22F2N2NaO4S 411.1161.
7.98 (dd, 1H, 3JH,H = 8.3 Hz, 4JH,H = 1.9 Hz), 8.04 (d, 1H,
4JH,H = 1.9 Hz) ppm. 13C NMR (75 MHz, CDCl3): d 25.4, 30.1, 45.0,
4.1.6.20. (S)-3,3-Difluoro-1-(3-fluoropropyl)-5-[1-(2-methoxy-
2
50.6, 60.3, 60.5, 76.1 112.3, 117.4 (d, JC,F = À22 Hz), 118.8, 125.8,
methylpyrrolidinyl)sulfonyl]indolin-2-one
(3b). (S)-1-(3-
3
130.7, 131.0 (d, JC,F = À3 Hz), 135.7, 138.6, 154.3, 161.6 (d,
Hydroxypropyl)-5-[1-(2-methoxymethylpyrrolidinyl)sulfonyl]-
isatin (2f) (50 mg, 0.13 mmol) was converted to 3b using fresh
DAST (0.055 mL, 0.41 mmol) as described in the general procedure
D and stirred at ambient temperature for 14 h. The crude product
was purified by column chromatography (ethyl acetate/cyclohex-
ane 1:1) to yield an off-white coloured gummy solid. Yield:
16 mg (30%). 1H NMR (400 MHz, CDCl3): d 1.65–1.72 (m, 2H),
1.89–1.95 (m, 2H), 2.06–2.19 (m, 2H), 3.11–3.17 (m, 1H), 3.36–
1JC,F = À248 Hz), 165.6, 182.9 ppm, 19F NMR (282 MHz, CDCl3): d
À113.1 (s, 1F) ppm. HRMS (ESI-MicroTof): m/e 487.1315 (M+Na+-
CH3OH)+, calcd for C22H25FN2NaO6S 487.1302.
4.1.6.17. (S)-4-Trifluoromethylbenzyl-5-[1-(2-methoxymethyl-
pyrrolidinyl)sulfonyl]isatin (2r). (S)-5-[1-(2-Methoxymethyl-
pyrrolidinyl)sulfonyl]isatin (1) (324 mg, 1 mmol) was converted
to 2r using sodium hydride (60 mg, 1.5 mmol, 60% in mineral oil)
and 4-trifluorobenzyl bromide (580 mg, 3 mmol) as described in
the general procedure B. The crude orange product was purified
by silica gel chromatography (diisopropyl ether/acetone 9:1) and
yielded 2r as a yellow foam. Yield: 175 mg (0.38 mmol, 38%). 1H
NMR (300 MHz, CDCl3): d 1.64–1.69 (m, 2H), 1.85–1.90 (m, 2H),
3.13–3.18 (m, 1H), 3.34 (s, 3H), 3.32–3.40 (m, 2H), 3.55 (dd, 1H,
2
3.47 (m, 2H), 3.37 (s, 3H), 3.60 (dd, 1H, JHb,Ha = 9.4 Hz,
3
3JHb,H = 3.9 Hz), 3.75–3.81 (m, 1H), 3.91 (t, 2H, JH,H = 7.0 Hz), 4.55
2
3
3
(dt, 2H, JH,F = 47.0 Hz, JH,H = 5.4 Hz), 7.09 (d, 1H, JH,H = 8.9 Hz),
8.02–8.04 (m, 2H) ppm. 13C NMR (100 MHz, CDCl3): d 24.1, 28.2
(d, JC,F = 20.1 Hz), 28.8, 37.2 (d, JC,F = 4.3 Hz), 49.3, 59.1, 59.2,
2
3
1
4
74.9, 80.9 (d, JC,F = 166.4 Hz), 109.8 (d, JC,F = 1.4 Hz), 110.9 (t,
1JC,F = 251.5 Hz), 120.9 (t, JC,F = 23.4 Hz), 124.4, 133.7, 134.0 (d,
2
3
3
2
2JHb,Ha = 9.4 Hz, JHb,H = 3.9 Hz), 3.69–3.73 (m, 1H), 5.04 (s, 2H),
4JC,F = 1.8 Hz), 146.9 (t, JC,F = 6.4 Hz), 165.3 (t, JC,F = 30.2 Hz)
3
6.87 (d, 1H, JH,H = 8.3 Hz), 7.46–7.50 (m, 2H), 7.63–7.66 (m, 2H),
ppm. 19F NMR (282 MHz, CDCl3): d À112.5 (s, 2F), À221.2 (tt, 1F,
7.98 (dd, 1H, 3JH,H = 8.3 Hz, 4JH,H = 1.9 Hz), 8.06 (d, 1H,
4JH,H = 1.9 Hz) ppm. 13C NMR (75 MHz, CDCl3): d 25.4, 30.1, 45.3,
50.6, 60.3, 60.5, 76.1 110.9, 117.5, 124.6, 126.2, 126.3, 127.8,
2JH,F = 54.9 Hz, JH,F = 27.5 Hz) ppm. HRMS (ESI-MicroTof): m/e
3
429.1066 (M+Na)+, calcd for C17H21F3N2NaO4S 429.1066.
2
130.8 (q, JC,F = À32.3 Hz), 134.4, 137.4, 137.8, 152.8, 157.8,
4.1.6.21. (S)-1-[3-(3-Hydroxypropoxy)propyl]-5-[1-(2-meth-
oxymethylpyrrolidinyl)sulfonyl]isatin (4). (S)-5-[1-(2-Meth-
oxymethylpyrrolidinyl)sulfonyl]isatin (1) (500 mg, 1.54 mmol)
was converted to 4 using anhydrous K2CO3 (680 mg, 4.938 mmol)
and 3-bromopropanol (0.30 mL, 3.395 mmol) as described in the
general procedure A and stirred for 36 h. The crude product was
purified by column chromatography (4% MeOH in CH2Cl2) to yield
a pale yellow coloured gummy solid. Yield: 490 mg (72%). 1H NMR
(300 MHz, CDCl3): d 1.54–1.94 (m, 8H), 3.09–3.17 (m, 1H), 3.32–
181.4 ppm, 19F NMR (282 MHz, CDCl3): d À62.9 (s, 3F) ppm. HRMS
(ESI-MicroTof): m/e 537.1272 (M+Na+CH3OH)+, calcd for
C23H25F3N2NaO6S 537.1282.
4.1.6.18. (S)-3,5-Bis-trifluoromethylbenzyl-5-[1-(2-methoxy-
methylpyrrolidinyl)sulfonyl]isatin
(2s). (S)-5-[1-(2-Meth-
oxymethylpyrrolidinyl)sulfonyl]isatin (1) (324 mg, 1 mmol) was
converted to 2s using sodium hydride (60 mg, 1.5 mmol, 60% in
mineral oil) and 3,5-bis-trifluorobenzyl bromide (0.27 mL, 454 g,
1.5 mmol) as described in the general procedure B. The crude or-
ange product was purified by silica gel chromatography (cyclohex-
ane/ethyl acetate 3:1 to 2:1) and yielded 2s as a yellow oil. Yield:
320 g (0.58 mmol, 58%). 1H NMR (300 MHz, CDCl3): d 1.64–1.68
(m, 2H), 1.86–1.89 (m, 2H), 3.07–3.11 (m, 1H), 3.31 (s, 3H), 3.31–
2
3.49 (m, 6H), 3.37 (s, 3H), 3.60 (dd, 1H, JHb,Ha = 9.4 Hz,
3
3JHb,H = 3.8 Hz), 3.70–3.83 (m, 3H, JH,H = 6.2 Hz), 3.84 (t, 2H,
3JH,H = 7.1 Hz), 7.01 (d, 1H, 3JH,H = 8.2 Hz), 8.06 (d, 1H,
3
4
4JH,H = 1.7 Hz), 8.10 (dd, 1H, JH,H = 8.2 Hz, JH,H = 1.9 Hz) ppm. 13C
NMR (75 MHz, CDCl3): d 24.1, 25.2, 28.8, 29.7, 36.0, 49.3, 58.6,
59.0, 59.1, 61.2, 61.3, 75.1, 110.6, 117.4, 124.5, 134.0, 137.6,
153.6, 158.4, 182.0 ppm. HRMS (ESI-MicroTof): m/e 463.1514
(M+Na)+, calcd for C20H28N2NaO7S 463.1509.
2
3
3.35 (m, 2H), 3.53 (dd, 1H, JHb,Ha = 9.4 Hz, JHb,H = 3.9 Hz), 3.69–
3
3.73 (m, 1H), 5.11 (s, 2H), 6.90 (d, 1H, JH,H = 8.3 Hz), 7.82 (br s,
3
4
2H), 7.88 (br s, 1H), 8.00 (dd, 1H, JH,H = 8.3 Hz, JH,H = 1.9 Hz),
8.05 (d, 1H, JH,H = 1.9 Hz) ppm. 13C NMR (75 MHz, CDCl3): d 24.5,
4.1.6.22. (S)-1-{3-[3-(2-Fluoroethoxy)propoxy]propyl}-5-[1-(2-
methoxymethylpyrrolidinyl)-sulfonyl]isatin (5). To a solution
of (S)-1-[3-(3-Hydroxypropoxy)propyl]-5-[1-(2-methoxymethyl-
pyrrolidinyl)sulfonyl]isatin (4) (60 mg, 0.136 mmol) in dry DMF
(2 mL) KH (20% suspension in oil) (33.0 mg, 0.163 mmol) was
added under argon atmosphere at À10 °C. The reaction mixture
was initially stirred at the same temperature for 30 min and at
ambient temperature for 1 h and then, catalytic amount of TBAI to-
gether with freshly distilled 1-bromo-2-fluoroethane (0.02 mL,
0.273 mmol) were added. The above mixture was stirred at ambi-
ent temperature for 96 h and then quenched with water (10 mL).
The mixture was extracted with CH2Cl2 (3 Â 15 mL), the combined
organic layers were dried over MgSO4, filtered and the solvent
4
29.2, 44.1, 49.7, 59.4, 59.6, 75.1, 111.1, 118.0, 121.0, 122.9 (q,
2
1JC,F = À270.7 Hz), 124.8, 127.6, 132.6 (q, JC,F = À32.7 Hz), 134.6,
136.7, 137.4, 152.4, 157.9, 181.0 ppm, 19F NMR (282 MHz, CDCl3):
d À63.1 (s, 6F) ppm. HRMS (ESI-MicroTof): m/e 605.1137 (M+Na+-
CH3OH)+, calcd for C24H24F6N2NaO6S 605.1151.
4.1.6.19. (S)-3,3-Difluoro-1-propyl-5-[1-(2-methoxymethylpyr-
rolidinyl)sulfonyl]indolin-2-one
oxymethylpyrrolidinyl)sulfonyl]-1-propylisatin
(3a). (S)-5-[1-(2-Meth-
(2c) (30 mg,
0.082 mmol) was converted to 3a using fresh DAST (0.026 mL,
0.205 mmol) as described in the general procedure D and stirred at
ambient temperature for 6 h. The crude product was purified by col-

A. K. Podichetty et al. / Bioorg. Med. Chem. 17 (2009) 2680–2688
2687
evaporated completely in vacuo. The resulting crude product was
purified by column chromatography (ethyl acetate/cyclohexane
2:3) to yield an off-white coloured gummy solid. Yield: 30 mg
crude product was purified by column chromatography (ethyl ace-
tate/cyclohexane 4:1) to yield a yellow-orange coloured solid.
Yield: 45 mg (35%). 1H NMR (400 MHz, CDCl3): d 1.61–1.71 (m,
2H), 1.82–1.93 (m, 2H), 3.08–3.16 (m, 1H), 3.31–3.47 (m, 2H),
(45%). 1H NMR (300 MHz, CDCl3): d 1.63–1.96, (m, 8H), 3.09–3.18
2
2
3
(m, 1H), 3.32–3.59 (m, 10H), 3.37 (s, 3H), 3.60 (dd, 1H, JHb,Ha
=
3.35 (s, 3H), 3.57 (dd, 1H, JHb,Ha = 9.4 Hz, JHb,H = 3.9 Hz), 3.60–
9.4 Hz, 3JHb,H = 3.8 Hz), 3.71–3.80 (m, 1H), 3.81 (t, 2H, 3JH,H = 6.8 Hz),
4.55 (dt, 2H, 2JH,F = 47.0 Hz, 3JH,H = 5.4 Hz), 7.13 (d, 1H, 3JH,H = 8.3 Hz),
8.07 (d, 1H, 4JH,H = 1.5 Hz), 8.13 (dd, 1H, 3JH,H = 8.3 Hz, 4JH,H = 1.9 Hz)
ppm. 13C NMR (75 MHz, CDCl3): d 24.1, 27.6, 28.8, 29.7, 36.8, 49.4,
3.76 (m, 3H), 3.90 (dd, 1H, JHa,Hb = 14.6 Hz, JHa,Hc = 7.3 Hz), 4.01
2
3
2
3
(dd, 1H, JHb,Ha = 14.6 Hz, JHb,Hc = 3.6 Hz), 4.23–4.29 (m, 1H), 7.26
3
4
(d, 1H, JH,H = 8.4 Hz), 7.96 (d, 1H, JH,H = 1.9 Hz), 8.02 (dd, 1H,
3JH,H = 8.4 Hz, JH,H = 1.9 Hz) ppm. 13C NMR (100 MHz, CDCl3): d
4
2
59.1, 59.2, 61.2, 61.3, 68.0, 70.1 (d, JC,F = 20.0 Hz), 75.3, 83.0 (d,
24.2, 28.9, 44.5, 47.2, 49.4, 59.1, 59.3, 69.8, 74.9, 111.9, 117.4,
124.3, 134.0, 137.4, 154.1, 158.7, 181.7 ppm. HRMS (ESI-MicroTof):
m/e 439.0700 (M+Na)+, calcd for C17H21ClN2NaO6S 439.0701.
1JC,F = 166.9 Hz), 110.4, 117.4, 124.6, 133.9, 137.5, 153.7, 158.5,
181 ppm. 19F NMR (282 MHz, CDCl3): d À222.7 (tt, 1F, 2JH,F = 54.3 Hz,
3JH,F = 27.5 Hz) ppm. HRMS (ESI-MicroTof): m/e 509.1722 (M+Na)+,
calcd for C22H31FN2NaO7S 509.1728.
4.1.6.26. (S)-5-[1-(2-Methoxymethylpyrrolidinyl)sulfonyl]-1-
(3,3,3-trifluoropropyl)isatin
(9a). (S)-5-[1-(2-Meth-
4.1.6.23. (S)-3-{3-[5-(1-(2-Methoxymethylpyrrolidinyl)sulfonyl)-
oxymethylpyrrolidinyl)sulfonyl]isatin (1) (35 mg, 0.108 mmol)
was converted to 9a using anhydrous K2CO3 (37 mg, 0.27 mmol)
and 3,3,3-trifluoro-1-iodopropane (0.025 mL, 0.216 mmol) as de-
scribed in the general procedure A and stirred for 14 h. The crude
product was purified by column chromatography (ethyl acetate/
toluene 1:1) to yield a golden orange coloured solid. Yield: 21 mg
(47%). 1H NMR (400 MHz, CDCl3): d 1.66–1.72 (m, 2H), 1.89–1.94
2,3-dioxoindolin-1-yl]propoxy}-propyl
methanesulfonate
(6). (S)-1-[3-(3-Hydroxypropoxy)propyl]-5-[1-(2-methoxymethyl-
pyrrolidinyl)sulfonyl]isatin (4) (137 mg, 0.311 mmol) was con-
verted to
6 using DMAP (1.9 mg, 0.015 mmol), fresh MsCl
(0.029 mL, 0.37 mmol) and dry triethylamine (0.052 mL,
0.37 mmol) as described in the general procedure C and stirred
for 1 h. The crude product was purified by column chromatography
(1% MeOH in CH2Cl2) to yield an off-white coloured gummy solid.
Yield: 120 mg (85%). 1H NMR (300 MHz, CDCl3): d 1.61–1.96 (m,
8H), 3.02–3.11 (m, 1H), 3.04 (s, 3H), 3.32–3.49 (m, 6H), 3.36 (s,
3
3
(m, 2H), 2.64 (tq, 2H, JH,H = 7.1 Hz, JH,F = 17.3 Hz), 3.12–3.18 (m,
2
1H), 3.36–3.47 (m, 2H), 3.36 (s, 3H), 3.58 (dd, 1H, JHb,Ha = 9.4 Hz,
3
3JHb,H = 3.9 Hz), 3.72–3.79 (m, 1H), 4.05 (t, 2H, JH,H = 7.0 Hz), 7.05
3
4
(d, 1H, JH,H = 8.3 Hz), 8.08 (d, 1H, JH,H = 1.7 Hz), 8.14 (dd, 1H,
2
3
4
3H), 3.61 (dd, 1H, JHb,Ha = 9.4 Hz, JHb,H = 3.8 Hz), 3.72–3.79 (m,
3JH,H = 8.3 Hz, JH,H = 1.9 Hz) ppm. 13C NMR (100 MHz, CDCl3): d
24.1, 28.9, 31.9 (q, JC,F = 29.3 Hz), 34.3 (q, JC,F = 3.8 Hz), 49.4,
3
3
2
3
1H), 3.83 (t, 2H, JH,H = 6.8 Hz), 4.20 (t, 2H, JH,H = 5.7 Hz), 7.11 (d,
3
4
1
1H, JH,H = 8.2 Hz), 8.07 (d, 1H, JH,H = 1.8 Hz), 8.13 (dd, 1H,
59.1, 59.3, 74.8, 110.1, 117.5, 124.9, 125.5 (q, JC,F = 276.9 Hz),
3JH,H = 8.2 Hz, JH,H = 1.9 Hz) ppm. 13C NMR (75 MHz, CDCl3): d
134.6, 137.6, 152.5, 157.7, 181.1 ppm. 19F NMR (282 MHz, CDCl3):
4
3
24.1, 25.2, 27.2, 28.8, 36.2, 37.5, 49.3, 59.0, 59.2, 61.2, 61.3, 66.8,
75.1, 110.4, 117.4, 124.8, 134.2, 137.6, 153.6, 158.4, 182.0 ppm.
HRMS (ESI-MicroTof): m/e 541.1287 (M+Na)+, calcd for
C21H30N2NaO9S2 541.1285.
d À65.5 (t, 3F, JH,F = 10.1 Hz) ppm. HRMS (ESI-MicroTof): m/e
475.1114 (M+Na+CH3OH)+, calcd for C18H23F3N2NaO6S 475.1121.
4.1.6.27. (S)-5-[1-(2-Methoxymethylpyrrolidinyl)sulfonyl]-1-(4,
4,4-trifluorobutyl)isatin
(9b). (S)-5-[1-(2-Methoxymethyl-
4.1.6.24. (S)-1-[3-(3-Fluoropropoxy)propyl]-5-[1-(2-methoxy-
methylpyrrolidinyl)sulfonyl]isatin (7). Toa solutionof (S)-3-[5-
{1-(2-methoxymethylpyrrolidinyl)sulfonyl}-2,3-dioxoindolin-1-
yl]propyl methanesulfonate (2g) (200 mg, 0.386 mmol) in
acetonitrile (5 mL) TBAFÁ3H2O (245 mg, 0.772 mmol) was added un-
der argon atmosphere. The reaction mixture was heated at 50 °C for
6 h and the solvent evaporated in vacuo. The resulting crude product
waspurifiedby columnchromatography(ethylacetate/cyclohexane
1:1) to yield an off-white coloured gummy solid. Yield: 60 mg (35%).
1H NMR (300 MHz, CDCl3): d 1.60–1.96 (m, 6H), 2.11 (m, 2H,
pyrrolidinyl)sulfonyl]isatin (1) (30 mg, 0.092 mmol) was converted
to 9b using anhydrous K2CO3 (32 mg, 0.23 mmol) and 4,4,4-tri-
fluoro-1-iodobutane (44 mg, 0.185 mmol) as described in the gen-
eral procedure A and stirred for 4 h. The crude product was purified
by column chromatography (ethyl acetate/toluene 1:1) to yield a
golden orange coloured solid. Yield: 35 mg (88%). 1H NMR
(400 MHz, CDCl3): d 1.65–1.75 (m, 2H), 1.86–1.95 (m, 2H), 2.02
3
(quintet, 2H, JH,H = 7.7 Hz), 2.17–2.31 (m, 2H), 3.11–3.17 (m, 1H),
2
3.36–3.47 (m, 2H), 3.37 (s, 3H), 3.59 (dd, 1H, JHb,Ha = 9.4 Hz,
3
3JHb,H = 3.9 Hz), 3.72–3.79 (m, 1H), 3.88 (t, 2H, JH,H = 7.3 Hz), 7.03
3
3
4
3JH,H = 6.3 Hz, JH,F = 27.1 Hz), 3.10–3.19 (m, 1H), 3.32–3.58 (m,
(d, 1H, JH,H = 8.3 Hz), 8.08 (d, 1H, JH,H = 1.6 Hz), 8.13 (dd, 1H,
2
3
4
6H), 3.39 (s, 3H), 3.66 (dd, 1H, JHb,Ha = 9.2 Hz, JHb,H = 3.8 Hz),
3JH,H = 8.2 Hz, JH,H = 1.5 Hz) ppm. 13C NMR (100 MHz, CDCl3): d
20.3 (q, JC,F = 2.8 Hz), 24.1, 28.9, 31.3 (q, JC,F = 29.6 Hz), 39.5,
49.4, 59.1, 59.2, 74.8, 110.1, 117.5, 124.9, 126.6 (q, 1JC,F = 276.5 Hz),
134.3, 137.7, 153.0, 157.8, 181.5 ppm. 19F NMR (282 MHz, CDCl3): d
3
3
2
3.72–3.79 (m, 1H), 3.82 (t, 2H, JH,H = 7.0 Hz), 4.52 (dt, 2H,
2JH,F = 47.0 Hz, JH,H = 5.5 Hz), 7.12 (d, 1H, JH,H = 8.2 Hz), 8.06 (d,
3
3
4
3
4
1H, JH,H = 1.7 Hz), 8.12 (dd, 1H, JH,H = 8.2 Hz, JH,H = 1.9 Hz) ppm.
13C NMR (75 MHz, CDCl3): d 24.1, 25.2, 28.4 (d, JC,F = 21.2 Hz),
À66.0 (t, 3F, JH,F = 10.5 Hz) ppm. HRMS (ESI-MicroTof): m/e
2
3
3
28.8, 36.0, 49.3, 59.1, 59.2, 61.2 (d, JC,F = 3.8 Hz), 61.3, 74.8, 81.0
489.1272 (M+Na+CH3OH)+, calcd for C19H25F3N2NaO6S 489.1278.
1
(d, JC,F = 165.9 Hz), 110.3, 117.5, 124.7, 134.0, 137.6, 153.5, 158.4,
182.0 ppm. 19F NMR (282 MHz, CDCl3):
d
À221.0 (tt, 1F,
4.1.6.28. (S)-1-(11,11-Difluoroundecyl)-5-[1-(2-methoxymethyl-
pyrrolidinyl)sulfonyl]isatin (10). (S)-5-[1-(2-Methoxymethyl-
pyrrolidinyl)sulfonyl]isatin (1) (35 mg, 0.108 mmol) was converted
to 10 using anhydrous K2CO3 (37 mg, 0.27 mmol) and 11-bromo-
1,1-difluoroundecane (58.5 mg, 0.216 mmol) as described in the
general procedure A and stirred for 24 h. The crude product was
purified by column chromatography (ethyl acetate/toluene 3:7)
to yield an orange-yellow coloured solid. Yield: 22 mg (40%). 1H
NMR (300 MHz, CDCl3): d 1.41–1.94 (m, 22H), 3.09–3.17 (m, 1H),
2JH,F = 54.3 Hz, JH,F = 27.2 Hz) ppm. HRMS (ESI-MicroTof): m/e
3
465.1465 (M+Na)+, calcd for C20H27FN2NaO6S 465.1466.
4.1.6.25. (S)-1-(3-Chloro-2-hydroxypropyl)-5-[1-(2-methoxy-
methylpyrrolidinyl)sulfonyl]isatin (8). To a round-bottomed
flask, (S)-5-[1-(2-methoxymethylpyrrolidinyl)sulfonyl]isatin (1)
(100 mg, 0.308 mmol) and sodium hydride (7.4 mg, 0.308 mmol)
were suspended in epichlorohydrin (0.75 mL, 9.0 mmol) under ar-
gon atmosphere and the reaction mixture was stirred at ambient
temperature for 48 h. At this stage a catalytic amount of sodium io-
dide was added and stirred for additional 48 h. The golden brown
reaction mixture was concentrated in vacuo and the resulting
2
3.35–3.49 (m, 2H), 3.37 (s, 3H), 3.61 (dd, 1H, JHb,Ha = 9.4 Hz,
3
3JHb,H = 3.9 Hz), 3.78 (m, 3H, JH,H = 7.2 Hz), 5.91 (tt, 1H,
3
3
2JH,F = 57.0 Hz, JH,H = 4.5 Hz), 7.02 (d, 1H, JH,H = 8.3 Hz), 8.06 (d,
4
3
4
1H, JH,H = 1.7 Hz), 8.11 (dd, 1H, JH,H = 8.3 Hz, JH,H = 1.9 Hz) ppm.

2688
A. K. Podichetty et al. / Bioorg. Med. Chem. 17 (2009) 2680–2688
3
13C NMR (75 MHz, CDCl3): d 22.1 (t, JC,F = 5.4 Hz), 24.1, 26.8, 27.2,
Imaging (EIMI). A.K.P. is grateful to the International NRW Gradu-
ate School of Chemistry for a stipend. Sandra Schröer’s assistance
in in vitro enzyme inhibition assays is gratefully acknowledged.
2
28.8, 29.0, 29.2, 29.3, 29.4, 34.1, 34.2 (t, JC,F = 22.6 Hz), 40.7, 49.4,
1
59.1, 59.2, 74.8, 110.4, 117.4, 119.1 (t, JC,F = 238.8 Hz), 124.6,
133.7, 137.5, 153.7, 157.8, 182.2 ppm. 19F NMR (282 MHz, CDCl3):
2
3
d À115.7 (dt, 2F, JH,F = 57.1 Hz, JH,F = 17.7 Hz) ppm. HRMS (ESI-
MicroTof): m/e 537.2239 (M+Na)+, calcd for C25H36F2N2NaO5S
537.2205.
References and notes
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4.1.7. In vitro enzyme inhibition assays (Table 1)
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Winkler, J. D.; Sung, C.-M.; Debouck, C.; Richardson, S.; Levy, M. A.; DeWolf, W.
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The inhibition potencies of target compounds 1–10 were assayed
for recombinant human caspases-3 and -7 (AlexisÒ Biochemicals
(Switzerland)) using their peptide-specific substrate (AlexisÒ Bio-
chemicals (Switzerland)) Ac-DEVD-AMC (Ac-Asp-Glu-Val-Asp-
AMC, caspase-3) as already described.10,11 The enzymatic activity
of the caspases was determined by measuring the accumulation of
the cleavedfluorogenic productAMC (7-amino-4-methylcoumarin).
Reaction rates showing inhibitory activity of the compounds 1–10
were measured with a FusionTM universal microplate analyzer (Perk-
inElmer) at excitation and emission wavelengths of 360 and 460 nm,
respectively. All assays were performed at a volume of 200
37 °C in reaction buffer.9,17 Buffers contained the compounds 1–10
in DMSO in single doses (end concentrations 500 M, 50 M,
M, 500 nM, 50 nM, 5 nM, 500 pM, 50 pM or 5 pM). Recombinant
ll at
l
l
5
l
caspases were diluted into the appropriate buffer to a concentration
of 0.5 units per assay (=500 pmol substrate conversion after 60 min).
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tion 10 lM) were added and reacted for further 10 min. The IC50 val-
ues were determined by non-linear regression analysis using the
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17. Shendage, D. M.; Fröhlich, R.; Bergander, K.; Haufe, G. Eur. J. Org. Chem. 2005,
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Acknowledgements
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This study was supported by grants from the Deutsche For-
schungsgemeinschaft (DFG), Sonderforschungsbereich 656 (pro-
jects A3 and B1), University of Münster, Germany and from Sie-
mens Medical Solutions to the European Institute of Molecular