Synthesis of sulfonamides and evaluation of their histone deacetylase (HDAC) activity

Article abstract of DOI:10.3390/12051125

A simple synthesis of sulfonamides 4-22 as novel histone deacetylase (HDAC) inhibitors is described. The key synthetic strategies involve N-sulfonylation of L-proline benzyl ester hydrochloride (2) and coupling reaction of N-sulfonyl chloride 3 with amine

Full text of DOI:10.3390/12051125

Molecules 2007, 12, 1125-1135
molecules
ISSN 1420-3049
© 2007 by MDPI
www.mdpi.org/molecules
Full Paper
Synthesis of Sulfonamides and Evaluation of Their Histone
Deacetylase (HDAC) Activity
Seikwan Oh 1, Hyung–In Moon 2, Il–Hong Son 2 and Jae–Chul Jung 1,*
1
Department of Neuroscience and Medical Research Institute, College of Medicine, Ewha Womans
University, Seoul 158–710, South Korea.
2
Department of Neuroscience and Inam Neuro Science Research Center, Wonkwang University
Sanbon Medical Center, Sanbondong, Gunpocity, Kyunggido, 435-040, South Korea. E-mails:
himoon@wonkwang.ac.kr (Hyung–In Moon); soniag@wonkwang.ac.kr (Il–Hong Son)
* To whom correspondence should be addressed; jcjung@ewha.ac.kr
Received: 17 April 2007; in revised form: 18 May 2007 / Accepted: 18 May 2007 / Published: 24 May
2007
Abstract: A simple synthesis of sulfonamides 4–22 as novel histone deacetylase (HDAC)
inhibitors is described. The key synthetic strategies involve N–sulfonylation of L–proline
benzyl ester hydrochloride (2) and coupling reaction of N–sulfonyl chloride 3 with amines
in high yields. It was found that several compounds showed good cellular potency with the
most potent compound 20 exhibiting an IC50 = 2.8 µM in vitro.
Keywords: HDAC; N–Sulfonylation; Coupling reaction; Anticancer.
Introduction
Histone acetylation and deacetylation play fundamental roles in the modulation of chromatin
topology and the regulation of gene transcription [1]. Histone deacetylase (HDAC) inhibitors that
inhibit proliferation and induce differentiation and/or apoptosis of tumor cells in culture and in animal
models have been identified [2]. A number of structurally diverse histone deacetylase inhibitors have
shown potent antitumor efficacy with little toxicity in vivo in animal models. Recently, HDAC
inhibitors have emerged as an exciting new class of potential anticancer agents for the treatment of
solid and hematological malignancies [3]. Current research priorities are to better characterize the

Molecules 2007, 12
1126
biological roles and biochemical features of HDAC inhibitors. In addition, efforts to identify optimal
HDAC inhibitors for anticancer therapeutics are underway [4]. More recently, the Angibaud group [5]
reported the preparation of a series of pyrimidyl-5-hydroxamic acids having significant HDAC activity
in human tumor cell lines. The Kalvinsh group [6] demonstrated that a series of novel sulfonamide
derivatives were synthesized and evaluated for their ability to inhibit human HDAC. The Delorme
group [7] developed of potential antitumor agents as a new set of sulfonamide derivatives. The Trivedi
group [8] described the QSAR modeling of sulfonamide inhibitors of HDAC.
In the context of our medicinal chemistry program dealing with the development of new potent
anticancer agents, we required sulfonyl chloride 3 as a key fragment in order to generate novel HDAC
inhibitors. We wish to report herein an efficient synthesis in good yields of sulfonamides 4–22, starting
from L–proline (1) via benzylation, sulfonylation, and coupling reaction and the evaluation of their
anti-proliferative inhibiting potency.
Results and Discussion
Chemistry
A series of sulfonamides 4–22 was prepared from (L)–proline (1) as a starting material, which was
condensed with benzyl alcohol in the presence of thionyl chloride in dichloromethane to give L–
proline benzyl ester hydrochloride (2) in 68% yield [9].
Scheme 1. Synthesis of sulfonamides 4–7.
O
OR2
N
b
O
c
N
O
N
S
O
S
O
O
R1
O
O
O
NH
Cl
OMe
1 R1=R2=H
2 R1=H HCl, R2=Bn
a
3
O
4
d
e
f
O
OH
O
N
O
N
N
O
S
O
O
O
O
S
O
g
O
S
O
NH
NH
NH
OH
O
OEt
O
O
OMe
O
7
5
6
Benzyl alcohol, SOCl2, CH Cl rt, 20 h, (68%); (b) SO2Cl2, TEA, 4-DMAP, toluene, 0 ºC, 2 h,
,
2
2
(72%); (c) L-phenylalanine methyl ester·HCl, DIPEA, 4-DMAP, CH2Cl2, rt, 16 h, (90%); (d) 10,
DIPEA, 4-DMAP, CH2Cl2, rt, 16 h, (80%); (e) L-phenylalanine ethyl ester·HCl, DIPEA, 4-
o
DMAP, CH2Cl2, rt, 16 h, (93%); (f) LiOH, THF/H2O, 0 C to rt, 4 h, (80%); (g) 1N-NaOH/
EtOH, rt, 16 h, (71%).

Molecules 2007, 12
1127
Compound 2 was treated with sulfuryl chloride (SO2Cl2) in toluene to generate in 72% yield the
key intermediate 3 [10], which was subsequently coupled with L-phenylalanine methyl ester
hydrochloride and L–phenylalanine ethyl ester hydrochloride in the presence of diisopropylethylamine
(DIPEA) and 4-dimethylaminopyridine (4-DMAP) in dichloromethane to afford 4 and 6 in 90% and
93% yields, respectively.
Sulfonamides 4 and 6 were readily hydrolyzed by lithium hydroxide aqueous solution or 1N-
sodium hydroxide aqueous solution to give acid 7 in 80% and 71% yields, respectively. In this
hydrolysis reaction, basic hydrolysis (1N-NaOH/MeOH or LiOH, H2O2, THF/H2O) is more favorable
than acidic hydrolysis (3N-HCl/THF-H2O, TFA/CH2Cl2) for preparation of acid 7 due to the higher
yield and ease of handling. Furthermore, LiOH conditions afforded a superior yield for comparing with
1N-NaOH condition (Scheme 1).
Scheme 2. Synthesis of PMB amine 10.
OMe
O
O
O
b
a
OH
O
OPMB
.
HN
HN
NH2 HCl
Boc
Boc
10
9
8
(a) 4-Methoxybenzyl-2,2,2-trichloroacetimidate, Sc(OTf)3, CH2Cl2, 0 oC to rt, 20 min, (97%); (b)
3N-HCl, 1,4-dioxane 0 oC to rt, 2 h, (64%).
To generate sulfonamide 5, PMB-amine 10 was prepared from compound 8 [11] which was
protected with freshly prepared 4-methoxybenzyl-2,2,2-trichloroacetimidate (commercially available
p-methoxybenzyl alcohol was treated with Cl3CCN in the presence of 1,5,7-triazabicyclo[4.4.0]dec-5-
ene) and catalytic amount of scandium triflate to give 9 [12], which was subsequently treated with 3N-
HCl aqueous solution in 1,4-dioxane in order to removal of N-Boc group to thus afford 10 in 62%
yield (over two steps) (Scheme 2). Interestingly, the condensation reaction of sulfonyl chloride 3 with
10 was took place smoothly to generate 5 in low yield. Unfortunately, compound 5 was unstable, and
isolation and characterization were problematic.
Sulfonyl chloride 3 was then coupled with several amines [amines including aromatic rings; (S)-
(+)-ethyl-4-phenylbutyrate-2-amine, 2-thiopheneethanamine, 4-fluorophenethylamine, pyridoxamine,
(R)-(+)-α-methylbenzylamine, and (S)-(+)-α-(methoxymethyl)phenethylamine; amines including
aliphatic groups; N,N-dimethylethylenediamine; 1-(2-aminoethyl)pyrrolidine, (S)-(+)-2-(hydroxyl-
methyl)pyrrolidine, N-(2-hydroxyethyl)piperazine, N-(2-aminoethyl)morpholine, and 2-(4-methyl-
piperazin-1-yl)-ethylamine] in the presence DIPEA and 4-DMAP in dichloromethane to give
sulfonamides 11–22 in high yields (Scheme 3).

Molecules 2007, 12
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Scheme 3. Synthesis of sulfonamides 11–22.
O
O
Reagents
N
N
O
a
O
O S O
O S O
Cl
R
3
NH
F
OEt
NH
NH
13 R=
12 R=
11 R=
14 R=
O
S
OH NH
NH
Me
NH
16 R=
19 R=
15 R=
18 R=
N
OH
H
OMe
HO
NH
NH
N
N
N
17 R=
20 R=
N
N
O
NH
N
NH
22 R=
21 R=
N
N
HO
(a) Reagents, DIPEA, 4-DMAP, CH2Cl2, rt, 3–16 h, (80%–95%).
Biological Activity
The in vitro growth inhibiting potency of sulfonamides 4 and 6–22 were evaluated and the results
are summarized in Table 1. We found that potent inhibition was observed with piperazine-sulfonamide
20, while compounds 4, 6, 11–12, 15, 17–19, and 21 did not possess HDAC activities. When aromatic
groups and pyrrolidine groups were used as coupling agents (compounds 4, 6, 11–12, 15, and 18–19),
the resulting compounds exhibited significantly reduced HDAC activity. Interestingly, piperazine–
based sulfonamides 20 and 21 were showed higher in vitro growth inhibiting potency when compared
to pyrrolidine–based sulfonamides 18 and 19.
Table 1. HDAC and growth inhibiting potency of novel sulfonamides 4 and 6–22.
Compound
IC50 cells (µM)a
7
40.3
36.8
25.3
21.5
2.8
13
14
16
20
22
12.3
>100
140
4, 6, 11–12, 15, 17–19, and 21
Sodium butyrateb
Trichostatin Ac
0.0046
a The values are means of three experiments.
b,c Reference materials.

Molecules 2007, 12
1129
Conclusions
In conclusion, a simple preparation of novel histone deacetylase (HDAC) inhibitors has been
described. The key synthetic strategies involve O–benzylation, N–sulfonylation, and coupling
reactions carried out in high yields. Compound 20 exhibited the most potent HDAC activity among
these analogues. We have found that piperazine–based sulfonamides 20 and 21 showed improved
growth inhibiting potency in vitro. In addition, the novel sulfonamides 7, 13, 14, 16, 20 and 22)
showed better HDAC activity than sodium butyrate. Although all prepared sulfonamides were
exhibited less HDAC activity than trichostatin A as a compared material, we have expected that simple
syntheses of new sulfonamide moieties and key fragments are useful for the modification of histone
deacetylase (HDAC) inhibitors.
Experimental
General
Reactions requiring anhydrous conditions were performed with the usual precautions for rigorous
exclusion of air and moisture. Tetrahydrofuran was distilled from sodium benzophenone ketyl prior to
use. Thin layer chromatography (TLC) was performed on precoated silica gel G and GP uniplates from
Analtech and visualized with 254–nm UV light. Flash chromatography was carried out on silica gel 60
[Scientific Adsorbents Incorporated (SAI), particle size 32–63 µm, pore size 60 Å]. 1H-NMR and 13C-
NMR spectra were recorded on Bruker DPX 500 instrument at 500 MHz (1H) and 125 MHz (13C),
respectively. The chemical shifts are reported in parts per million (ppm) downfield from
tetramethylsilane. Infrared (IR) spectra were obtained on an ATI Mattson FT/IR spectrometer. Mass
spectra were recorded with a Waters Micromass ZQ LC–Mass system and high resolution mass spectra
(HRMS) were measured with a Bruker BioApex FTMS system by direct injection using an
electrospray interface (ESI). Elemental analyses were performed on a CE instruments Model 1110
elemental analyzer. When necessary, chemicals were purified according to the reported procedures
[13].
Biology: In Vitro Inhibition of Histone Deacetylase
Histone deacetylase fraction was prepared as described by Yoshida et al. [14]. Human leukemia
K562 (2.5 x 108) cells were disrupted in buffer-A (15 mM potassium phosphate buffer, pH 7.5,
containing 5% glycerol and 0.2 mM EDTA, 15 mL). The nuclei were collected by centrifugation
(35000g, 10 min) and resuspended with buffer-A (15 mL) containing 1 M (NH4)2SO4. After
sonication, the supernatant was collected by centrifugation, and ammonium sulfate was added to make
the final concentration 3.5 M. After stirring for 1 h at 0 °C, the precipitate was collected by
centrifugation, dissolved with buffer-A (4 mL), and dialyzed against buffer-A (2000 mL). The
dialysate was loaded onto a mono Q HR 5/5 column (Pharmacia) equilibrated with buffer-A and eluted
with a linear gradient of 0–1 M-NaCl in buffer-A (30 mL). A single peak of histone deacetylase
activity was eluted around 0.4 M-NaCl, and the fraction was stored at –80 °C until use. Inhibition of

Molecules 2007, 12
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histone deacetylase was estimated as described by Yoshida et al. with slight modifications [14]. 3H-
Labeled histone was prepared by the method of Yoshida et al.: 3 K562 cells (108 cells) were incubated
in growth medium (25 mL) containing 0.5 mCi/mL [3H]sodium acetate (152.8 GBq/mmol; NEN) and
5 mM sodium butyrate at 37 °C [14]. Histone deacetylase inhibitory activity of test compound was
measured as follows: the mixture (total volume 50 µL) containing the above histone deacetylase
fraction (2 µL), 3H labeled histone (100 µg/mL), and test compound (5 µL) was incubated for 10 min
at 37 °C. [3H]Acetic acid, which was liberated from 3H-labeled histone, was extracted with ethyl
acetate, and radioactivity was measured by a liquid scintillation counter.
Chlorosulfonyl-L-proline benzyl ester (3)
To a stirred solution of L-proline benzyl ester hydrochloride (2, 2.4 g, 10.0 mmol) in dry toluene
(25 mL) were added dropwise TEA (2.3 g, 21.0 mmol) and DMAP (0.12 g), followed by addition of
sulfuryl dichloride (2.7 g, 20.0 mmol) in dry toluene (15 mL) at –10 °C and the mixture was stirred at
0 °C for 2 h. The reaction mixture was diluted with dichloromethane (70 mL) and washed with sat’d.
aqueous NH4Cl solution (80 mL) and water (100 mL). The organic layer was separated, dried over
anhydrous MgSO4, filtered, and concentrated under reduced pressure. The residue was purified by
flash column chromatography (silica gel, 15% ethyl acetate in hexanes) to give 3 (1.45 g, 48%) as a
beige solid. Rf = 0.4 (15% ethyl acetate in hexanes); [α]24D –105.0 (c 0.6, CHCl3); mp 65 °C (lit. [15]
mp
1
65–66 °C); IR (neat, NaCl) 3474, 3412, 1638, 1618, 1457, 1124, 837 cm-1; H-NMR (CDCl3) δ 7.46–
7.32 (m, 5H), 5.24 (s, 2H), 4.47 (dd, J = 4.0, 4.0 Hz, 1H), 3.79–3.73 (m, 1H), 3.63–3.57 (m, 1H), 2.34–
2.31 (m, 1H), 2.21–2.15 (m, 1H), 2.13–2.06 (m, 2H); 13C-NMR (CDCl3) δ 169.4, 135.0, 128.6, 128.5,
128.1, 67.8, 62.7, 51.7, 31.0, 24.8; HRMS calcd. for C12H14NO4SClNa 326.0230 [M+Na]+, found
326.0240.
General procedure for coupling reaction of chlorosulfonyl-L-proline benzyl ester (3) and several
amines
To a solution of chlorosulfonyl-L-proline benzyl ester (3, 0.3 g, 1.0 mmol) in dichloromethane (10
mL) were added DIPEA (0.19 g, 1.5 mmol) and DMAP (0.12 g, 0.1 mmol), followed by addition of
amines (1.1 mmol) at 0 °C and the reaction mixture was stirred at room temperature for 16 h. The
reaction mixture was diluted with dichloromethane (10 mL) and washed with sat’d aqueous NH4Cl
solution (10 mL) and brine (10 mL). The organic layer was separated, dried over anhydrous MgSO4,
filtered, and concentrated under reduced pressure. The residue was purified by flash column
chromatography (silica gel, ethyl acetate-hexane-methanol; 15:80: 5, v/v) to afford sulfonyl-L-proline
benzyl esters 4–22.
N-(L-Phenylalanine methyl ester)sulfonyl-L-proline benzyl ester (4). Yield: 90%; viscous oil; Rf = 0.3
(80:15:5 n-hexane-ethyl acetate-methanol, v/v); [α]25 –12.5 (c 0.40, CHCl3); IR (neat, NaCl) 3474,
D
1
3412, 1638, 1618, 1457, 1124, 837 cm-1; H-NMR (CDCl3) δ 7.42–7.18 (m, 10H), 5.20 (s, 2H), 4.56
(brs, 1H), 4.38 (dd, J = 4.0, 4.0 Hz, 1H), 3.75 (s, 3H), 3.74 (s, 1H), 3.25 (dd, J = 7.0, 7.0 Hz, 1H), 3.13

Molecules 2007, 12
1131
(dd, J = 5.5, 5.5 Hz, 1H), 3.00–2.87 (m, 2H), 2.20–2.14 (m, 1H), 2.00–1.93 (m, 1H), 1.85–1.80 (m,
13
2H); C-NMR (CDCl3) δ 172.2, 172.0, 137.1, 135.7, 135.3, 129.5, 129.2, 128.5, 128.4, 128.3, 128.1,
126.7, 67.3, 61.0, 57.0, 52.7, 48.3, 39.4, 31.2, 25.1; HRMS calcd. for C22H27N2O6S: 447.1590 [M+H]+,
found: 447.1609; Anal. calcd. C 59.27, H 5.76, N 6.38; found: C 59.18, H 5.87, N 6.27.
N-(L-Phenylalanine ethyl ester)sulfonyl-L-proline benzyl ester (6). Yield: 93%; viscous oil; Rf = 0.4
(80:15:5 n-hexane-ethyl acetate-methanol, v/v); [α]25 –105.2 (c 1.5, CHCl3); IR (neat, NaCl) 3288,
D
1
3064, 3029, 2981, 1740, 1604, 1455, 1340, 1151, 1020, 859 cm-1; H-NMR (CDCl3) δ 7.41–7.18 (m,
10H), 5.41 (brs, 1H), 5.21 (dd, J = 8.0, 8.0 Hz, 2H), 4.47 (dd, J = 4.0, 4.0 Hz, 1H), 4.30–4.23 (m, 1H),
4.21 (q, J = 4.5 Hz, 2H), 3.52–3.41 (m, 2H), 2.84–2.65 (m, 2H), 2.32–2.23 (m, 1H), 2.22–2.12 (m,
13
1H), 2.08–1.90 (m, 4H), 1.32 (t, J = 7.0 Hz, 3H); C-NMR (CDCl3) δ 172.3, 172.1, 140.6, 135.3,
128.5, 128.4, 128.3, 128.1, 126.1, 67.3, 61.9, 61.4, 56.0, 48.6, 35.2, 31.7, 31.2, 25.2, 14.6; HRMS
calcd. for C24H30N2O6SNa: 497.1722 [M+Na]+, found: 497.1743.
N-[(S)-Ethly 4-phenylbutanoate)sulfamoyl]-L-proline benzyl ester (11). Yield: 87%; viscous oil;
Rf = 0.3 (80:15:5 n-hexane-ethyl acetate-methanol, v/v); [α]25D –105.2 (c 0.5, CHCl3); IR (neat, NaCl)
3288, 3064, 3029, 2981, 1740, 1604, 1455, 1340, 1151, 1020, 859 cm-1; 1H-NMR (CDCl3) δ 7.41–7.18
(m, 10H), 5.41 (brs, 1H), 5.21 (dd, J = 8.0, 8.0 Hz, 2H), 4.47 (dd, J = 4.0, 4.0 Hz, 1H), 4.30–4.23 (m,
1H), 4.21 (q, J = 4.5 Hz, 2H), 3.52–3.41 (m, 2H), 2.84–2.65 (m, 2H), 2.32–2.23 (m, 1H), 2.22–2.12
(m, 1H), 2.08–1.90 (m, 4H), 1.32 (t, J = 7.0 Hz, 3H); 13C-NMR (CDCl3) δ 172.3, 172.1, 140.6, 135.3,
128.5, 128.4, 128.3, 128.1, 126.1, 67.3, 61.9, 61.4, 56.0, 48.6, 35.2, 31.7, 31.2, 25.2, 14.6; HRMS
calcd. for C24H30N2O6SNa: 497.1722 [M+Na]+, found: 497.1743.
1-[2-Thiophenethylsulfamoyl)]-L-proline benzyl ester (12). Yield: 90%; viscous oil; Rf = 0.3 (80:15:5
n-hexane-ethyl acetate-methanol, v/v); [α]25D –34.8 (c 0.5, CHCl3); IR (neat, NaCl) 3302, 3067, 3034,
1
2954, 2881, 1743, 1638, 1455, 1330, 1148, 1017, 849 cm-1; H-NMR (CDCl3) δ 7.52–7.30 (m, 5H),
7.24–7.14 (m, 1H), 7.00–6.83 (m, 2H), 5.29–5.11 (m, 2H), 4.75–4.60 (m, 1H), 4.52–4.42 (m, 1H),
3.53–3.28 (m, 4H), 3.04 (t, J = 6.5 Hz, 2H), 2.36–2.24 (m, 1H), 2.12–1.90 (m, 3H); 13C-NMR (CDCl3)
δ 172.5, 140.5, 135.3, 128.6, 128.4, 128.3, 127.0, 125.6, 124.0, 67.3, 61.3, 48.7, 44.7, 31.3, 30.6, 25.2;
HRMS calcd. for C18H22N2O4S2Na: 417.0919 [M+Na]+, found: 417.0927; Anal. calcd. C 54.80, H 5.62,
N 7.10; found: C 54.66, H 5.88, N 6.96.
1-[2-(4-Fluorophenethylsulfamoyl)]-L-proline benzyl ester (13). Yield: 85%; viscous oil;
Rf = 0.3 (80:15:5 n-hexane-ethyl acetate-methanol, v/v); [α]25D –31.2 (c 0.25, CHCl3); IR (neat, NaCl)
1
3297, 3067, 3036, 2955, 2881, 1747, 1602, 1510, 1455, 1328, 1219, 1149, 1076, 834 cm-1; H-NMR
(CDCl3) δ 7.41–7.32 (m, 5H), 7.20–7.12 (m, 2H), 7.03–6.95 (m, 2H), 5.29 (dd, J = 12.0, 12.0 Hz,
2H), 4.62 (t, J = 6.0 Hz, 1H), 4.45 (dd, J = 4.0, 4.0 Hz, 1H), 3.46–3.38 (m, 1H), 3.37–3.25 (m, 3H),
2.80 (t, J = 7.0 Hz, 2H), 2.32–2.21 (m, 1H), 2.07–2.00 (m, 1H), 1.98–1.90 (m, 2H); 13C-NMR (CDCl3)
δ 172.5, 162.4, 160.5, 135.3, 134.0, 130.2, 128.5, 128.3, 128.1, 115.4, 115.3, 67.2, 61.2, 48.7, 44.6,
35.5, 31.3, 25.2; HRMS calcd. for C20H23N2O4SFNa: 429.1260 [M+Na]+, found: 429.1272; Anal.
calcd. C 59.10, H 5.70, N 6.89; found: C 59.21, H 5.83, N 6.72.

Molecules 2007, 12
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1-[(R)-Methylbenzylsulfamoyl]-L-proline benzyl ester (15). Yield: 93%; viscous oil; Rf = 0.3 (80:15:5
n-hexane-ethyl acetate-methanol, v/v); [α]25D –17.5 (c 0.4, CHCl3); IR (neat, NaCl) 3288, 3032, 2977,
1
2879, 1747, 1605, 1497, 1332, 1151, 1084, 873 cm-1; H-NMR (CDCl3) δ 7.40–7.25 (m, 10H), 5.20
(dd, J = 12.0, 12.0 Hz, 2H), 5.14–5.05 (m, 1H), 4.73–4.65 (m, 1H), 4.40 (dd, J = 4.0, 4.0 Hz, 1H),
3.31–3.19 (m, 2H), 2.16–2.07 (m, 1H), 2.01–1.94 (m, 1H), 1.92–1.76 (m, 2H), 1.53 (s, 3/2H), 1.51 (s,
13
3/2H); C-NMR (CDCl3) δ 172.5, 143.4, 135.4, 128.5, 128.3, 128.1, 127.4, 126.1, 67.2, 60.9, 53.6,
48.7, 31.3, 25.0, 24.2; HRMS calcd. for C20H24N2O4SNa: 411.1354 [M+Na]+, found: 411.1367.
1-[(1S)-Methoxymethyl-2-phenethylsulfamoyl]-L-proline benzyl ester (16). Yield: 89%; viscous oil; Rf
= 0.3 (80:15:5 n-hexane-ethyl acetate-methanol, v/v); [α]25 –67.3 (c 0.30, CHCl3); IR (neat, NaCl)
D
3288, 3030, 2980, 2892, 1749, 1603, 1498, 1331, 1149, 1083, 854 cm-1; 1H-NMR (CDCl3) δ 7.41–7.21
(m, 10H), 5.20 (dd, J = 12.0, 12.0 Hz, 2H), 4.76 (d, J = 9.0 Hz, 1H), 4.40 (dd, J = 4.5, 4.5 Hz, 1H),
3.90–3.81 (m, 1H), ), 3.44 (dd, J = 4.5, 4.5 Hz, 1H), 3.37 (s, 3H), 3.31 (dd, J = 3.0, 3.0 Hz, 1H), 3.22
(dd, J = 8.5, 8.5 Hz, 1H), 2.96–2.84 (m, 3H), 2.24–2.16 (m, 1H), 2.01–1.94 (m, 1H), 1.86–1.79 (m,
13
2H); C-NMR (CDCl3) δ 172.4, 137.9, 135.5, 129.6, 128.5, 128.3, 128.2, 128.1, 126.4, 73.2, 67.1,
61.0, 59.2, 54.9, 48.3, 38.7, 31.3, 25.3; HRMS calcd. for C22H28N2O5SNa: 455.1617 [M+Na]+, found:
455.1623; Anal. calcd. C 61.09, H 6.52, N 6.48; found: C 60.95, H 6.41, N 6.37.
1-[4-(S)-2-Hydroxymethyl)pyrrolidine-1-sulfonyl]-L-proline benzyl ester (19). Yield: 80%; viscous oil;
Rf = 0.3 (80:15:5 n-hexane-ethyl acetate-methanol, v/v); [α]25 –62.3 (c 0.6, CHCl3); IR (neat, NaCl)
D
1
3519, 3064, 3034, 2957, 2881, 1746, 1655, 1456, 1337, 1147, 1017, 826 cm-1; H-NMR (CDCl3)
δ 7.41–7.30 (m, 5H), 5.19 (s, 1H), 5.18 (s, 1H), 4.49 (dd, J = 3.5, 4.0 Hz, 1H), 3.94–3.87 (m, 1H), 3.63
(dd, J = 4.5, 4.5 Hz, 1H), 3.60–3.39 (m, 4H), 3.31–3.22 (m, 1H), 2.73 (brs, 1H), 2.32–2.21 (m, 1H),
2.06–1.93 (m, 4H), 1.89–1.75 (m, 3H); 13C-NMR (CDCl3) δ 172.4, 135.3, 128.6, 128.5, 128.4, 128.3,
128.2, 128.0, 67.3, 65.5, 61.8, 61.2, 50.1, 49.4, 31.4, 29.3, 25.3, 25.0; HRMS calcd. for
C17H24N2O5SNa: 391.1304 [M+Na]+, found: 391.1299.
1-[4-(2-Hydroxyethyl)piperazine-1-sulfonyl]-L-proline benzyl ester (20). Yield: 81%; viscous oil;
Rf = 0.4 (80:15:5 n-hexane-ethyl acetate-methanol, v/v); [α]25D –35.7 (c 0.60, CHCl3); IR (neat, NaCl)
1
3416, 3065, 3034, 2950, 2879, 2821, 1747, 1455, 1340, 1154, 1016, 875 cm-1; H-NMR (CDCl3)
δ 7.40–7.30 (m, 5H), 5.17 (d, J = 4.0 Hz, 2H), 4.42 (dd, J = 3.5, 3.5 Hz, 1H), 3.62 (t, J = 5.5 Hz, 2H),
3.57–3.44 (m, 1H), 3.43–3.36 (m, 1H), 3.32–3.19 (m, 4H), 2.53 (t, J = 5.5 Hz, 2H), 2.50–2.41 (m,
13
5H), 2.30–2.20 (m, 1H), 2.04–1.92 (m, 3H); C-NMR (CDCl3) δ 172.4, 135.4, 128.5, 128.3, 128.0,
67.1, 67.0, 61.1, 57.0, 53.4, 48.8, 39.4, 31.4, 25.3; HRMS calcd. for C18H28N3O5S: 398.1750 [M+H]+,
found: 398.1762; Anal. calcd. C 54.39, H 6.85, N 10.57; found: C 54.17, H 6.67, N 10.38
1-[2-(4-Methylpiperazin-1-yl)ethylsulfamoyl]-L-proline benzyl ester (22). Yield: 88%; viscous oil;
Rf = 0.3 (80:15:5 n-hexane-ethyl acetate-methanol, v/v); [α]25D –34.0 (c 0.60, CHCl3); IR (neat, NaCl)
3286, 3064, 3034, 2956, 2817, 1745, 1455, 1330, 1148, 1012, 863 cm-1; 1H-NMR (CDCl3) δ 7.39–7.31
(m, 5H), 5.17 (dd, J = 12.5, 12.5 Hz, 2H), 4.45 (dd, J = 4.0, 4.0 Hz, 1H), 3.52–3.37 (m, 2H), 3.31–3.20
(m, 1H), 3.19–3.11 (m, 1H), 3.10–2.98 (m, 1H), 2.64–2.33 (m, 10H), 2.29 (s, 3H), 2.27–2.21 (m, 1H),
13
2.07–1.94 (m, 3H); C-NMR (CDCl3) δ 172.4, 135.4, 128.5, 128.4, 128.3, 128.0, 127.3, 126.8, 67.1,

Molecules 2007, 12
1133
61.0, 56.4, 55.1, 52.6, 48.8, 39.7, 31.4, 25.3; HRMS calcd. for C19H31N4O4S: 411.2066 [M+H]+,
found: 411.2073; Anal. calcd. C 55.59 H 7.37, N 13.65; found: C 55.71, H 7.58, N 13.31.
Acknowledgements
This work has been supported by the KOSEF Brain Neurobiology Grant (2006) and Ewha Global
Challenge (BK21) grant.
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Sample Availability: Samples of the compounds are available from authors.
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