Design, Synthesis, and Biological Evaluation of Peptidomimetic N-Substituted Cbz-4-Hyp-Hpa-Amides as Novel Inhibitors of Plasmodium falciparum

Article abstract of DOI:10.1002/cbdv.201700037

A new series of peptidomimetic N-substituted Cbz-4-Hyp-Hpa-amides were designed, synthesized, and evaluated for inhibition of the Plasmodium falciparum. Substituents on the N-atom of the amide group were selected alkyl-, allyl-, aryl-, 2-hydroxyethyl-, 2-

Full text of DOI:10.1002/cbdv.201700037

Article Type: Full Paper
Corresponding author mail id : valeriy_bacherikov@yahoo.com
DESIGN, SYNTHESIS AND BIOLOGICAL EVALUATION OF PEPTIDOMIMETIC N-
SUBSTITUTED CBZ-4-HYP-HPA-AMIDES AS NOVEL INHIBITORS OF PLASMODIUM
FALCIPARUM
Authors: Valeriy A. Bacherikov a, Amar G. Chittiboyina b, c, Mitchell A. Avery b, c
.
Affiliation: a) Department of Medicinal Chemistry and Biology, Odessa Medical Institute, International
Humanitarian University, Odessa, 65009, Ukraine;
b) National Center for Natural Products Research, University of Mississippi, University, MS 38677, United
States;
c) School of Pharmacy, Department of BioMolecular Sciences, University of Mississippi, University, MS
38677, United States.
A new series of peptidomimetic N-substituted Cbz-4-Hyp-Hpa-amides was designed, synthesized and
evaluated for inhibition of the Plasmodium falciparum. Substituents on the N atom of the amide group
were selected. They are the following alkyl-, allyl-, aryl-, 2-hydroxyethyl-, 2-cyanoethyl-, cyanomethyl-, 2-
hydroxyethyl-, 2,2-diethoxyethyl-, or 2-ethoxy-2-oxoethylamino groups, and about forty new compounds
were synthesized and evaluated for anti-plasmodial activity in vitro. Antimalarial activity was investigated
as for the final peptide mimetics, and their immediate predecessors, carrying TBDMS or TBDPS protecting
groups on 4-hydroxyproline residue and eighteen derivatives exhibited toxicity against P. falciparum. Of
these agents, compound 23e was shown to have potent antimalarial activity with IC50 528 ng/mL.
Key words: antimalarial activity, peptidomimetic, falcipain, drug design, synthesis.
1. Introduction
Malaria, trypanosomiasis, and leishmaniasis are major parasitic diseases in many countries. Recent
WHO data shows approximately 429,000 deaths from malaria, mainly due to the influence of the parasite
Plasmodium falciparum [1]. The existing chemotherapy of these diseases suffers from the evolution of
widespread drug resistance and/or lack of safe and effective drugs.
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The search and use of new drugs directed against malarial proteases is required among various
methods of malaria treatment, combating parasitic infections by chemotherapy approach [2]. Plasmodium
falcipains and other cysteine proteases are involved in various processes of the erythrocytic cycle of the
malaria parasite and are exciting targets for antiparasitic drug design [3]. Although the key catalytic role of
Plasmodium falciparum enzymes, principal food vacuolar hemoglobinases, falcipain-2 (FP-2) and falcipain-3
(FP-3) is generally known, the degradation of hemoglobin, as source of amino acids for parasite
development, is carried out by enzymatic complex which contains several parasite proteins, also including
plasmepsin II, plasmepsin IV, histo aspartic protease, and heme detoxification protein (HDP) [4-6]
.
[4]
The majority of previous studies was devoted to the inhibitors search of FP-2 and FP-3 and HDP
was only recently proposed as a drug target [7]. Of the two groups of mechanism-based cysteine protease
inhibitors, preference should be given to reversible antiparasitic agents, which are considered potentially
more effective than irreversible ones [8, 9]
.
The results of synthetic [10-15], protein modelling, docking studies [16] and virtual screening studies [9,
15, 17-20], led to the conclusion that in order to obtain highly active agents, efforts should be made to the
design of peptidomimetic molecules with high affinity to the binding site of the enzyme.
P. J. Rosenthal et. al. investigated several peptide fluoromethyl ketone proteinase inhibitors,
constituted as combination Phe-Arg, Phe-Ala, Phe-Phe or Tyr-Ala derivatives, from which benzyl (S)-1-((R)-
1-fluoro-6-guanidino-2-oxohexan-3-ylamino)-1-oxo-3-phenylpropan-2-ylcarbamate (1, (Z)-Phe-Arg-CH2F,
Fig. 1) was the most potent inhibitor. Peptidomimetic compound 1 inhibited P. falciparum trophozoite
cysteine proteinase (TCP), blocked hemoglobin degradation and killed parasites at picomolar
concentrations [10]. Further research within this group of compounds revealed such highly potent inhibitors
as Mu-Phe-HPhe-CH2F (2) [11], Mu-Leu-HphVSPh (3) [12] and N-Me-pipu-Leu-Hph-VS2Np (4) [13]
.
Fig. 1. Early structures of the peptidyl cysteine protease inhibitors
Peptidomimetic vinyl sulfones like 3 and 4 (Fig. 1), playing the role of Michael acceptors, tend to
form covalent bond with the thiolate of the catalytic cysteine within active site that make them irreversible
inhibitors [21, 22]. However, cell permeability and the selectivity of vinyl sulfones towards parasitic protease
in comparison with human cysteine protease should be definitely improved [22]. Similar results were also
shown in the study of irreversible inhibitors containing fumaric acid as an electrophilic building block, which
can covalently link the active site Cys residue of FP-2 and rhodesain via a Michael-type reaction [23], [24]
.
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Several ketone-based peptides (5, 6, Fig. 2) were reported to be potent and reversible inhibitors of
cruzain, cysteine protease implicated in Chagas’ disease [25]
.
Fig. 2. Peptidyl ketone-based cysteine protease (cruzain) inhibitors
A number of di- and tri-peptides was investigated, some of which (7 and 8, Fig. 3) exhibited
antiparasitic activity in the picomolar range [26]
.
Fig. 3. Structures of the reversible peptidomimetic malaria parasite inhibitors
Recently, series of peptidomimetic hydroxyprolyl-homophenylalanylketones were designed,
synthesized and evaluated for inhibition of the Plasmodium falciparum cysteine proteases FP-2 and FP-3
[15]. Analysis of structures mostly potent peptidomimetics 9 (IC50 80 nM against FP-2 and 60 nM against FP-
3), 10 (IC50 1.10 μM against FP-2 and 0.52 μM against FP-3) (Fig. 4) and other derivatives from this series in
comparison with structural motif of potent inhibitors of cysteine proteases was evident that hydroxyproline
in the P2 pocket (see Fig. 4), an α-hydroxyketone electrophile in the P’1 pocket, and homophenylalanine in
the P1 pocket were suitable substituents for high binding affinity of these peptidomimetics.
Fig. 4. Structures of the peptidomimetic hydroxyprolyl-homophenylalanylketones
The authors proposed to formulate the residues of unnatural amino acids into anti-malarial
peptidomimetic inhibitors, for example, L-homophenylalanine fragment in this series of derivatives. It was
assumed that these peptides would be more resistant to peptidase and would have an increased half-life.
Furthermore, the design can lead to decreased analogue flexibility and improved binding thermodynamics
as well as introduction of rigid L-proline residue [15]
.
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It can be concluded from the data of the antimalarial activity of the discussed compounds, that
their design was quite productive and the substances 9 and 10 can be accepted as the lead compounds in
this group of peptidomimetics.
2. Results and discussion
2.1. Chemistry
It was previously found that high activity was observed for compounds composed of 4-hydroxy-L-
proline and L-homophenylalanine constituents [15]. Based on these data, corresponding dipeptide 17,
consisting of protected 4-hydroxy-L-proline and L-homophenylalanine residues with free C-terminus
available for modification was chosen as a key intermediate. The major variances of structure made to
these analogues were substitution of the C-terminus of L-homophenylalanine moiety related to area of P’1
site of our model.
Scheme 1. Synthesis of key dipeptide 17
Intermediate dipeptide 17 was synthesized in five steps (Scheme 1) starting from N-Cbz-4-hydroxy-
L-proline (11) by sequential introduction of tert-butyldimethyl (TBDMS) or tert-butyldiphenyl (TBDPS) silyl
protective groups, which were mostly appropriate for the following transformations [27]. Obtained silyl
protected N-Cbz-4-hydroxy-L-proline (14) then was condensed with ethyl L-homophenylalanine HCl (15)
and saponification of 16 provided with desired dipeptide 17. Substances for antimalarial testing were
obtained by condensing C-terminus of 17 with substituted amines.
According to the chosen strategy obtained dipeptide 17 was reacted with substituted
ethylenediamines 18 to form intermediates 19 and then TBDMS (or TBDPS) protecting group was removed
by standard procedure [27] to give desired peptidomimetics 20 (Scheme 2).
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R2
N
HO
RO
O
RO
R1
HN
H
H
R3
O
N
R1
N
N
+
i or ii
R2
N
N
N
R3
O
O
O
O
CH2Cl2
O
O
18
17a. R = TBDMS
17b. R = TBDPS
19a-f
Reaction conditions: i.TEA/HOBt/DMAP/EDAC; ii. DCC or HOBt/DCC;
iii. n-Bu4NF/THF.
iii
R2
N
O
HO
H
N
R1
R3
N
From 17a: a. R1=R2=H, R3=Ph; b.R1=Ph, R2=R3=H;
N
c. R1=R2=H, R3=4-MePh; d.R1=4-MePh, R2=R3=H;
O
e. R1=H, R2=R3=Me; From 17b: f. R1= R2= R3=Me.
O
O
20a-f
Scheme 2. Synthesis of peptidomimetic inhibitors 20
We also synthesized a number of derivatives 22 and 23a bearing amino ethylencyano-substituents at
P’1 site (Scheme 3).
Scheme 3. Synthesis of cyano-substituted peptidomimetic inhibitors 23
Peptidomimetic inhibitor 26 with cyano substituent directly attached to amide group was obtained
from acid 14a and 2-amino-4-phenylbutyronitrile hydrochloride 24 (Scheme 4).
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Scheme 4. Synthesis of cyano-substituted peptidomimetic inhibitor 26
Requisite
2-amino-4-phenylbutyronitrile
hydrochloride
24
was
obtained
from
phenylpropionaldehyde by the known method [28]
.
The group of compounds bearing phenolic or aliphatic hydroxyl substituents and having ability for
the formation of hydrogen bonds was designed and synthesized. TBDMS protected aminophenols 27 and 2-
[27]
(tert-butyldimethylsilyloxy)ethylamine 30 were synthesized according to the standard procedure
from
aminophenols or ethanolamine and TBDMS chloride in presence of imidazole or triethylamine in CH2Cl2.
Reaction of 27, 30 with acid 17a gave derivatives 28, 31 and the following removal of protected TBDMS
groups led to the formation of desired peptidomimetics 29, 32 (Scheme 5).
Scheme 5. Synthesis of phenolic and ethylenhydroxy substituted peptidomimetic inhibitors
For obtaining peptidomimetic bearing acetal function starting acid 17a was reacted with
commercially available aminoacetaldehyde diethylacetal 33 in standard conditions to give 34 and
peptidomimetic derivative 35 was obtained after removing of the protected group (Scheme 6).
Scheme 6. Synthesis of aminoacetaldehyde diethylacetal peptidomimetic inhibitor 35
Comparison of structure of lead compound 9 with known peptidomimetics and their mechanism of
action brought to the idea that tri-peptides, bearing α-hydroxyketone residue with general structure 36
(Fig. 5) would have similar biological action. Due to potentialities inherent in variety of available α-
aminoacid derivatives the great number of active peptidomimetics can be designed and synthesized.
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Figure 5. The lead peptidyl cysteine protease inhibitor and tri-peptides
For these purposes acid 17b was reacted with glycine ethyl ester hydrochloride 37 to give desired
tripeptide ester 38 which was saponified to acid 39 using LiOH (Scheme 7).
HO
TBDPSO
O
TBDPSO
H
OR
H
O
N
N
N
OEt
H
i
N
O
N
+
O
NH2HCl
O
O
O
O
O
O
37
38 R = Et;
39 R = H.
17b
ii
Reaction conditions: i.TEA/HOBt/DMAP/EDAC/CH2Cl2;
ii. LiOH aq./THF:MeOH = 1:1
Scheme 7. Synthesis of peptidomimetic tripeptide ester 38
We were planning to introduce (N-tosyl, N-aryl) fragments at P1 and P1’-sites of our prototypical
molecule instead of the homophenylalanyl moiety, similar to the structures 3 and 4. For this purpose, in the
model reaction N-carbobenzyloxy-L-proline 40 was condensed with N-phenyl-4-toluensulfonamide 41 [29] to
form the desired product 42 in good yield (Scheme 8).
Scheme 8. Model synthesis of peptidomimetic toluensulfonamide 42
2.2 Biological results
There were about forty compounds bearing the various residues on the P’1 site and P2 site
synthesized whose antimalaria activity was examined. Antimalarial activity was investigated as for the final
peptide mimetics, and their immediate predecessors, carrying TBDMS or TBDPS protecting groups. The
cytotoxicity of the peptidyl cysteine protease inhibitors against P. falciparum (D6 and W2 clones) is shown
in Table 1. The in vitro growth inhibition of studied derivatives expressed as IC50 was within the range 1.1-
7.4 μM/L (528-5280 ng/mL). About half of the synthesized compounds was not exhibited admissible
antimalarial activity (IC50 over 5280 ng/mL) and was considered as inactive one.
Among active compounds, the derivatives, wherein the 4-hydroxyproline group was protected as
the silyl ethers, namely substances 19, 22, 25, 28, 31, 34, 38 and 39, were quantitatively dominated. Based
on the obviously greater lipophilic the nature of silyl substituted molecules one can say that this clearly
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[30]
observed fact can be attributed to an easier penetration of these derivatives into target cells
and
probably their resistance to intracellular proteases. These considerations also suggest that as well as P3 site,
the P2 site of inhibitor molecule must maintain a certain hydrophobicity to preserve the anti-plasmodium
activity. Similar structure-activity relationships of potential choline or ethanolamine analogues aimed at
increasing lipophilicity were essential for antimalarial activity and interfering with P. falciparum
phospholipid metabolism [31]
.
Although the studied compounds were hydrophobic with a parameter LogP, calculated by various
methods [32], in the range 1.8 – 9.3 (Table 1, only LogP values for Meylan/Kowwin model were shown), the
acceptable correlation of these values with antiplasmodium activity was not found.
Among active substances silyl substituted derivatives were dominating, but the most active
compound found was 23e with the free hydroxyl group on proline residue and N-(cyanomethyl)-N-
methylamino group at P’1 site. Approximately 2.5 times less active agent in the studied row was derivative
31, bearing TBDPS protecting groups on hydroxyl substituent group on the proline and the aminoethyl
moieties. Another compound 32 with the free hydroxyl group on proline residue and 2-hydroxyphenyl
substituent exhibited moderate activity. This finding is consistent with the hypothesis that the molecules
bearing a hydroxyl group on the proline ring displayed an additional increase of activity [15]. On the other
hand, the activity of the silyl derivatives can probably be attributed to their lipophilicity and easier
penetration through cell membranes. Moreover, bulky substituent may facilitate proper orientation of the
agent in the enzyme active site.
The data may indicate that for better bioavailability the inhibitor molecule must contain at P3 site
the low polar substituents. At the same time, the high activity undoubtedly suggests positive influence free
hydroxyl group in the pyrrolidine ring. The data clearly revealed that the obtained results require a more
thorough QSAR examination, which is currently ongoing. Results of obtained QSAR model will be published
elsewhere.
Table 1. Inhibition of P. falciparum and LogP data of active compounds (19-39)
P. falciparum (D6 clone)
Inhibition
P. falciparum (W2 clone)
Inhibition
LogP
model
Compounds
IC50
IC50
IC50
IC50
SI
SI
Meylan/Kowwin [32]
(ng/mL)
(μM/L)
(ng/mL)
(μM/L)
19a
19b
19d
19e
19f
2700
2600
3200
4000
3000
2800
4200
4.1
3.9
4.8
6.5
4.0
4.3
6.6
>1.8
>1.8
>1.5
>1.2
>1.6
>1.7
>1.1
3200
2800
2800
4760
2000
1600
2800
4.9
4.2
4.2
7.8
2.7
2.5
4.4
>1.5
>1.7
>1.7
>1.0
>2.4
>3.0
>1.7
4.75
3.60
4.53
5.64
6.33
7.50
5.92
22b
22c
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22d
4760
5280
528
6.4
7.4
1.1
16.3
3.7
4.7
1.9
5.4
4.8
3.1
4.4
0.4
0.017
>1.0
>9.0
>9.0
>1.5
>2.4
>1.6
>3.7
>1.7
>1.6
>2.1
>1.5
4760
5280
720
6.4
>1.0
>9.0
>6.6
>1.7
>3.4
>1.5
>3.2
>1.5
>1.6
>2.4
>1.2
2.76
5.62
7.51
9.09
3.01
2.32
3.67
2.41
3.00
1.84
1.84
22e
7.4
23e
1.5
24
3200
2000
3000
1300
2800
3000
2300
3200
2800
1400
3200
1500
3200
3000
2000
4000
14.2
2.6
25
28
5.1
31
2.1
32
6.2
34
4.8
38
2.7
39
5.5
Chloroquine
artemisinin
0.05
0.0145
8
Note 1. Compounds with IC50 over 5280 ng/mL were considered as inactive ones and were not included in
Table 1.
Note 2. SI is a selectivity index: SI = CC50/IC50, where CC50 is a cytotoxic concentration. All these compounds
were not cytotoxic to Vero cells.
2.3 Conclusions
In the summary, we designed and synthesized a new series of peptidomimetic N-substituted Cbz-4-
Hyp-Hpa-amides as potential antimalarial agents. The study found that numerous peptidomimetics
corresponding to the lead structure and the current model of the active antimalarial agents may be
synthesized by condensation of protected Cbz-4-hydroxy-L-proline and L-homophenylalanine, followed by
the addition of the variety of substituents to C-terminus L-homophenylalanine in order to create variations
in P’1 site.
The evaluation of antimalarial activity of the obtained compounds showed that the model generally
corresponded to the structural requirements of the active compound. The analysis of the biological activity
data showed that the substituent at the hydroxyl group of hydroxyproline could also affect the antimalarial
activity of the peptidomimetic. In the study an acceptable correlation between calculated LogP values
(Meylan/Kowwin model) with antiplasmodium activity was not found.
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3. Experimental work
3.1. Chemistry
General Methods: All solvents and chemicals were purchased from Aldrich. Anhydrous solvents
were stored with molecular sieves. THF, ether, and DME were distilled from sodium-benzophenone;
acetonitrile and CH2Cl2 were distilled from P2O5 immediately prior to the use. Final inhibitors 19−39 were
synthesized as detailed in the following procedures below. The reactions were conducted under argon
atmosphere. Melting points were determined on a Fargo melting point apparatus and were not corrected.
1H NMR and 13C NMR spectra were determined on Bruker 400, 500 and 600 MHz spectrometers in CDCl3 or
o
DMSO-d6 solution at 25 C. Chemical shifts (δ) were expressed in ppm downfield from internal standard
TMS. Infrared (IR) spectra were obtained on Bruker Vector33 FTIR spectrometer. Optical rotations were
measured on Rudolph Autopol IV polarimeter. MS spectra were carried out on HP 5973 GC-MS instrument.
High Resolution Mass spectra were recorded on Bruker BioApex LC-Mass system with a Lock Spray Source
or with a FTMS system by direct injection using an electrospray interface (ESI). Flash column
chromatography was carried out over silica gel G60 (70-230 mesh, ASTM; Merck). Thin layer
chromatography (TLS) was performed on silica gel G60 F254 (Merck) plates with short wave length UV light
for visualization. The purity of all final compounds was determined to be ≥95% by NMR and HPLC-MS
analysis.
(2S,4R)-Benzyl 4-(tert-butyldimethylsilyloxy)-2-((S)-1-ethoxy-1-oxo-4-phenylbutan-2-ylcarbamo-
yl)pyrrolidine-1-carboxylate (16). Triethylamine (TEA, 1.518 g, 2.08 mL, 15 mmol), hydroxybenzotriazole
(HOBt, 0.811 g, 6 mmol), dimethylaminopyridine (DMAP, 6 mg, 0.05 mmol) in CH2Cl2 N-(3-
dimethylaminopropyl)-N’-ethylcarbodiimide hydrochloride (EDAC, 1.15 g, 6 mmol) were added to the
solution of (2S,4R)-1-(benzyloxycarbonyl)-4-(tert-butyl-dimethylsilyloxy)pyrrolidine-2-carboxylic acid (14,
1.897 g, 5 mmol) at -5 o C. A reaction mixture was stirred under Ar pad for 2 h at room temperature then
ethyl (S)-2-amino-4-phenylbutyrate hydrochloride (L-homophenylalanine ethyl ester hydrochloride, 15,
1.243 g, 5.1 mmol) was added and stirring was continued for 20 h. After this time the reaction mixture was
mixed with saturated NH4Cl solution (20 mL) at 0 o C, formed layers were separated, water solution was
extracted with ethyl acetate (4×6 mL), organic phases were combined, washed with brine (10 mL), dried
over Na2SO4, filtered and concentrated in vacuo to give a crude product (3.38 g), which was purified by
column chromatography on SiO2 (150 g, column 30×250 mm) using gradient ethyl acetate/hexanes = 10/90
27.4
1
to 30/70 as eluant affording 2.719 g (95.7%) of product 16 as syrup. [α]D = -15.0 (c = 1, CHCl3). H NMR
(400 MHz, CDCl3): δ 0.044, 0.060 (each 3H, s, 2×CH3), 0.854 (9H, s, 3×CH3), 1.15 (3H, br. t, CH3), 1.52 (2H, m,
CH2), 1.80 (4H, m, 2×CH2), 2.27 (1H, m, CH), 2.49 (2H, m, CH2), 3.33 (2H, m, CH2), 4.01 (2H, m, CH2), 4.32
(3H, m, CH & CH2), 5.01 (2H, m, CH2), 6.30 (1H, br. s, NH), 7.1-7.4 (10H, m, PhH). 13C NMR (100 MHz, CDCl3):
δ 172.12, 171.37, 156.58, 155.49, 141.13, 140.82, 136.65, 128.70, 128.27, 128.04, 126.31, 77.68, 77.56,
77.36, 77.04, 70.75, 70.07, 67.58, 61.58, 60.56, 59.98, 59.55, 55.89, 54.95, 52.46, 52.20, 40.45, 37.55,
34.23, 31.74, 25.92, 21.22, 18.15, 14.39, -4.58, -4.69. IR (film) νmax 418.2, 698.6, 748.1, 837.1, 1024.2,
1115.7, 1204.1, 1356.5, 1419.0, 1539.7, 1683.3, 2360.3, 2930.4, 3314.2 cm-1. HRMS (TOF) (m/z): M+H+ calcd
for C31H45N2O6Si 569.3059, found 569.3047.
2-((2S,4R)-1-(Benzyloxycarbonyl)-4-(tert-butyldimethylsilyloxy)
pyrrolidine-2-carboxamido)-4-
phenylbutanoic acid (17a). Aqueous solution of LiOH (1 M) was added dropwise to the solution of 16
(2.273 g, 4 mmol) in THF/MeOH (1/1, 20 mL) with stirring at -5 o C. After 3.5 h turbid reaction mixture
became transparent and after 4 h TLC analysis was shown consuming of starting ester. The reaction mixture
was cooled in ice-water bath and acidified with 1 N HCl to pH ~5.5, then extracted with EtOAc (5×5 mL).
Organic phases were combined, washed with brine (5 mL), water (5 mL), dried over Na2SO4, filtered and
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concentrated in vacuo to give a product (17a), 1.793 g (82.9%) which was pure for using in the next step.
o
22.1
27.4
1
Mp 119 C. [α]D = -18.4 (c = 1, MeOH); [α]D = -15.4(c = 1, CHCl3). H NMR (400 MHz, CDCl3): δ 0.040,
0.055 (each 3H, s, 2×CH3), 0.85 (9H, s, 3×CH3), 1.98 (2H, m, CH2), 2.18 (1H, m, CH), 2.33 (1H, m, CH), 2.62
(2H, m, CH2), 3.43 (1H, m, CH), 3.56 (1H, m, CH), 4.50 (3H, m, CH & CH2), 5.13 (2H, m, CH2), 6.55 (1H, br. s,
NH), 7.1-7.4 (10H, m, PhH). IR (film) νmax 426.0, 441.1, 698.2, 836.8, 1022.4, 1116.3, 1172.9, 1254.1, 1357.0,
1420.4, 1537.1, 1684.8, 2929.4 cm-1. HRMS (TOF) (m/z): M+H+ calcd for C29H40N2O6Si 541.2716, found
541.2734.
(2S,4R)-Benzyl
amino)butan-2-ylcarbamoyl)pyrrolidine-1-carboxylate
aminoethyl)(phenyl)amino)-1-oxo-4-phenylbutan-2-ylcarbamoyl)-4-(tert-butyldimethylsilyloxy)-
4-(tert-butyldimethylsilyloxy)-2-(1-oxo-4-phenyl-1-(2-(phenylamino)ethyl-
(19a) and (2S,4R)-benzyl 2-(1-((2-
pyrrolidine-1-carboxylate (19b). General procedure. TEA (152 mg, 0.208 mL, 1.5 mmol), HOBt (81 mg, 0.6
mmol), DMAP (0.6 mg, 0.05 mmol) in CH2Cl2 (5 mL) EDAC (115 mg, 0.6 mmol) was added to the solution of
2-((2S,4R)-1-(benzyloxycarbonyl)-4-(tert-butyldimethylsilyloxy)pyrrolidine-2-carboxamido)-4-
phenylbutanoic acid (17a, 270 mg, 0.5 mmol)at -5 oC. A reaction mixture was stirred under Ar pad for 0.5 h
at room temperature then N-phenylethylenediamine (18a, 82 mg, 0.079 mL, 0.6 mmol) was added and
stirring was continued for 22 h. After this time the reaction mixture was mixed with saturated NH4Cl
solution (2 mL) at 0 o C, formed layers were separated, water solution was extracted with ethyl acetate (4×2
mL), organic phases were combined, washed with brine (2 mL), dried over Na2SO4, filtered and
concentrated in vacuo to give a crude product which was purified by column chromatography on SiO2 (18 g,
column 15×220 mm) using gradient ethyl acetate/hexanes = 10/90 to 30/70 as eluant yielding two
products, 19a 67 mg (20.4%) and 19b 49 mg (14.9%) as syrups. 19a [α]D26.4=-30.4 (c=1, CHCl3) and 19b
[α]D26.3=-27.2 (c=1, CHCl3). 1H NMR (400 MHz, CDCl3); 19a: δ 0.060, 0.081 (each 3H, s, 2×CH3), 0.880 (9H, s,
3×CH3), 2.00 (2H, m, CH2), 2.16 (1H, m, CH), 2.35 (1H, m, CH), 2.68 (2H, m, CH2), 3.26 (3H, m, CH & CH2),
3.44 (2H, m, CH2), 3.60 (2H, m, CH2), 4.09 (1H, t, J = 8.4 Hz, CH), 4.44 (2H, m, CH2), 4.96 (1H, d, J = 12.8 Hz,
CH), 5.05 (1H, d, J = 12.8 Hz, CH), 6.30 (1H, br. s, NH), 6.69 (3H, m, 3×CH, PhH), 7.12-7.32 (12H, m, PhH),
7.51 (2H, s, NH). HRMS (TOF) (m/z): M+H+ calcd for C37H51N4O5Si 659.3629, found 659.3656. 19b: δ 0.06,
0.08 (each 3H, s, 2×CH3), 0.88 (9H, s, 3×CH3), 2.00 (2H, m, CH2), 2.16 (1H, m, CH), 2.35 (1H, m, CH), 2.68 (2H,
m, CH2), 3.26 (3H, m, CH & CH2), 3.44 (2H, m, CH2), 3.60 (2H, m, CH2), 4.09 (1H, t, J = 8.4 Hz, CH), 4.44 (2H,
m, CH2), 4.96 (1H, d, J = 12.8 Hz, CH), 5.05 (1H, d, J = 12.8 Hz, CH), 6.30 (1H, br. s, NH), 6.69 (3H, m, 3×CH,
PhH), 7.12-7.32 (12H, m, PhH), 7.51 (2H, s, NH). IR (film) 19a νmax 428.7, 467.1, 693.4, 746.8, 780.1, 842.5,
901.5, 1020.1, 1115.6, 1171.4, 1205.2, 1254.3, 1358.9, 1417.7, 1513.4, 1604.8, 1653.5, 2360.9, 2857.5,
2927.3, 3021.6, 3302.4 cm-1; 19b νmax 426.6, 457.0, 695.7, 748.6, 782.3, 836.9, 900.7, 1022.2, 1115.8,
1171.3, 1206.0, 1256.8, 1356.1, 1418.0, 1512.6, 1603.6, 1650.4, 2360.5, 2856.2, 2928.6, 3028.7, 3300.6 cm-
1. HRMS (TOF) (m/z) 19a: M+H+ calcd for C37H51N4O5Si 659.3629, found 659.3648; 19b: M+H+ calcd for
C37H51N4O5Si 659.3629, found 659.3611.
(2S,4R)-Benzyl
4-(tert-butyldimethylsilyloxy)-2-(1-oxo-4-phenyl-1-(2-(p-tolylamino)ethyl-
amino)butan-2-ylcarbamoyl)pyrrolidine-1-carboxylate (19c) and (2S,4R)-benzyl 2-(1-((2-aminoethyl)(p-
tolyl)amino)-1-oxo-4-phenylbutan-2-ylcarbamoyl)-4-(tert-butyldimethylsilyloxy)pyrrolidine-1-carboxylate
[33]
(19d) were synthesized following general procedure from 17a (108 mg, 0.2 mmol) and appropriate 18b
(31 mg, 0.205 mmol). It was isolated 37 mg (27.5%) 19c and 24 mg (17.8%) of 19d as syrups. 19c [α]D
26.2
=
37.4 (c=1, CHCl3), 19d [α]D25.9 = 58.7 (c=0.3, CHCl3). 1H NMR (400 MHz, CDCl3); 19c: δ 0.031, 0.046 (each 3H,
s, 2×CH3), 0.845 (9H, s, 3×CH3), 2.02 (4H, m, 2×CH2), 2.26 (3H, s, CH3), 2.36 (1H, m, CH), 2.64 (2H, m, CH2),
3.20 (1H, m, CH), 3.37 (2H, m, CH2), 3.48 (3H, m, CH & CH2), 3.62 (2H, m, CH2), 4.41 (3H, m, CH & CH2), 4.96
(1H, d, J = 12.8 Hz, CH), 5.06 (1H, d, J = 12.8 Hz, CH), 5.16 (1H, d, J = 12.8 Hz, CH), 6.43 (1H, br. s, NH), 6.73
(1H, br. s, NH), 7.03-7.47 (15H, m, PhH), 7.47 (1H, s, NH). HRMS (TOF) (m/z): M+H+ calcd for C38H53N4O5Si
673.3791, found 673.3824. 19d: δ 0.06, 0.08 (each 3H, s, 2×CH3), 0.88 (9H, s, 3×CH3), 1.26 (3H, s, CH3), 2.01
(2H, m, CH2), 2.22 (2H, m, CH), 2.36 (2H, m, CH2), 2.69 (1H, m, CH2), 3.34 (4H, m, 2×CH & CH2), 3.62 (1H, m,
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CH2), 4.16 (1H, t, J = 8.4 Hz, CH), 4.49 (2H, m, CH2), 4.92 (1H, d, J = 12.4 Hz, CH), 5.06 (1H, d, J = 12.4 Hz, CH),
6.77 (2H, br. s, NH2), 6.98-7.28 (15H, m, PhH), 7.63 (1H, s, NH). IR (film) 19c νmax 412.8, 698.2, 777.5, 807.9,
836.5, 1022.3, 1116.0, 1169.7, 1257.0, 1355.9, 1424.0, 1522.4, 1680.4, 2856.4, 2927.9, 3340.4cm-1; 19d νmax
413.1, 418.7, 425.1, 430.2, 434.2, 441.9, 447.1, 458.1, 477.1, 699.3, 1126.2, 1357.3, 1429.8, 1513.5, 1669.4,
2924.5, 3316.4 cm-1. HRMS (TOF) (m/z) 19c: M+H+ calcd for C38H53N4O5Si 673.3824, found 673.3801; 19d:
M+H+ calcd for C38H53N4O5Si 673.3785, found 673.3801.
(2S,4R)-Benzyl
4-(tert-butyldimethylsilyloxy)-2-(1-(2-(dimethylamino)ethylamino)-1-oxo-4-
phenylbutan-2-ylcarbamoyl)pyrrolidine-1-carboxylate (19e) was synthesized following general
procedure from 17a (270 mg, 0.5 mmol) and 18e (53 mg, 0.6 mmol) affording 230 mg (75.3%) 19e as syrup.
27.4
1
[α]D = -10.8 (c = 0.5, CHCl3). H NMR (400 MHz, CDCl3) δ 0.034, 0.054 (each 3H, s, 2×CH3), 0.85 (9H, s,
3×CH3), 2.13 (2H, m, CH2), 2.29 (1H, m, CH), 2.47 (1H, m, CH2), 2.67 (2H, m, CH2), 3.18 (3H, m, CH & CH2),
3.32 (1H, m, CH2), 3.46 (2H, m, CH2), 3.61 (2H, m, CH2), 4.41 (2H, m, CH2), 5.15 (2H, dd, J = 11.6 Hz, CH2),
6.22 (1H, s, NH), 6.9-7.5 (12H, m, PhH & 2×NH). IR (film) νmax 410.0, 418.4, 428.9, 641.0, 698.9, 749.1, 891.5,
1087.6, 1244.1, 1312.1, 1356.5, 1448.7, 1570.2, 1629.2, 2851.4, 2927.7, 3329.3 cm-1. HRMS (TOF) (m/z):
M+H+ calcd for C33H51N4O5Si 611.3629, found 611.3617.
(2S,4R)-Benzyl 4-(tert-butyldiphenylsilyloxy)-2-((S)-1-((2-(dimethylamino)ethyl)-(methyl)amino)-
1-oxo-4-phenylbutan-2-ylcarbamoyl)pyrrolidine-1-carboxylate (19f) was synthesized following general
22.3
procedure from 17b (200 mg, 0.3 mmol, [α]D
= -26.4 (c = 1, CHCl3)) and 18f (37 mg, 0.36 mmol)
27.4
affording 166 mg (73.9%) 19f as syrup. [α]D = -8.4 (c = 0.5, CHCl3). 1H NMR (400 MHz, CDCl3) δ 7.65 –
6.95 (m, 21H), 5.13 (m, 2H), 4.75 (m, 1H), 4.56 (m, 1H), 4.39 (m, 1H), 3.43 (s, 5H), 2.87 (m, 4H), 2.72 – 2.32
(m, 8H), 2.24 (m, 3H), 1.98 (m, 4H), 1.00 (s, 9H). IR (film) νmax 3293.4, 418.4, 430.3, 447.6, 464.5, 508.1,
611.7, 701.5, 743.1, 822.2, 1022.4, 1112.1, 1169.3, 1356.1, 1416.8, 1455.1, 1496.4, 1640.2, 1706.4, 2360.5,
2857.5, 2931.1 cm-1. HRMS (TOF) (m/z): M+H+ calcd for C44H57N4O5Si 749.4098, found 749.4115.
(2S,4R)-Benzyl
4-hydroxy-2-((S)-1-oxo-4-phenyl-1-(2-(phenylamino)ethylamino)butan-2-
ylcarbamoyl)pyrrolidine-1-carboxylate (20a). General procedure. n-Bu4NF (1M solution in THF, 0.2 mL)
was added to stirred solution of 19a (66 mg, 0.1 mmol) in THF (1 mL) and the reaction mixture was stirred
at room temperature. After 1 h reaction was finished, brine (2 mL) was added, formed layers were separated,
water solution was extracted with EtOAc (3×1 mL), and organic phases were combined, dried over Na2SO4,
filtered and concentrated in vacuo. A residue was purified with column chromatography on SiO2 (10 g,
column 15×210 mm), using CH3OH/CHCl3 = 5/95, 10/90 (v/v) as eluant yielding 43.5 mg of 20a (79.8%). Mp
115 oC. [α]D26.2 = -32.4 (c = 0.5, CHCl3). 1H NMR (400 MHz, CDCl3) δ 7.78 – 6.46 (m, 17H), 5.08 (s, 2H), 4.69
(m, 1H), 4.40 (m, 3H), 3.44 (m, 7H), 2.97 (m, 1H), 2.76 – 2.39 (m, 2H), 2.19 (m, 2H), 2.00 (m, 2H), 1.75 (m,
1H), 1.46 – 1.13 (m, 2H). IR (film) νmax 425.4, 696.1, 750.0, 1126.3, 1356.9, 1422.2, 1511.7, 1603.2, 1651.2,
2927.3, 3306.2 cm-1. HRMS (TOF, m/z): M+H+ calcd for C31H37N4O5 545.2764, found 545.2777.
(2S,4R)-Benzyl
2-(1-((2-aminoethyl)(phenyl)amino)-1-oxo-4-phenylbutan-2-ylcarbamoyl)-4-
hydroxypyrrolidine-1-carboxylate (20b) was synthesized according to general procedure from 19b (44
mg) and n-Bu4NF (1M solution in THF, 0.14 mL) in anh. THF (1 mL), yield was 28 mg (60.3%). Mp 114 oC
26.8
1
(dec.). [α]D
= -32.4 (c = 1, CHCl3). H NMR (400 MHz, CDCl3) δ 1.92 (2H, m, CH2), 2.08-2.30 (3H, m,
3×CH), 2.66 (2H, m, CH2), 2.99 (1H, m, CH), 3.09 – 3.46 (5H, m, 5×CH), 3.52 (1H, d, J = 11.6 Hz, CH), 3.61 (1H,
dd, J = 3.6, 11.6 Hz, CH), 4.20 (1H, m, CH), 4.33 (1H, t, J = 8.0 Hz, CH), 4.46 (1H, br.s, CH), 5.05 (2H, dd, J =
12.4 & 13.3 Hz, CH2), 6.60 (3H, m, PhH & OH), 7.05-7.40 (13H, m, PhH & 2×NH), 7.05-7.53 (1H, m, NH). IR
(film) νmax 418.4, 434.2, 696.4, 749.8, 1129.3, 1173.0, 1357.6, 1430.0, 1539.1, 1603.3, 1673.2, 2925.4,
3352.2 cm-1. HRMS (TOF) (m/z): M+H+ calcd for C31H37N4O5 545.2764, found 545.2770.
This article is protected by copyright. All rights reserved.

(2S,4R)-Benzyl
4-hydroxy-2-((S)-1-oxo-4-phenyl-1-(2-(p-tolylamino)ethylamino)butan-2-
ylcarbamoyl)pyrrolidine-1-carboxylate (20c) was synthesized according to general procedure from 19c
(22 mg) and n-Bu4NF (1M solution in THF, 0.065 mL) in anh. THF (0.5 mL), yield was 17.2 mg (96.1%).
o
26.7
1
Mp 134 C. [α]D = -19.4 (c = 1, CHCl3). H NMR (400 MHz, CDCl3) δ 7.32 (s, 1H), 7.23 – 6.91 (m, 14H),
6.85 (s, 1H), 6.75 (d, J = 8.1, 2H), 6.40 (d, J = 7.5, 2H), 4.88 (s, 3H), 4.30 (s, 2H), 4.25 – 4.06 (m, 3H), 3.54 –
3.15 (m, 6H), 2.76 (s, 1H), 2.47 (s, 2H), 2.31 (s, 1H), 2.15 (s, 2H), 2.02 (s, 4H), 1.87 (s, 1H), 1.80 (s, 2H), 1.59
(s, 1H). IR (film) νmax 418.1, 699.5, 741.4, 1124.8, 1172.3, 1356.6, 1419.5, 1521.7, 1681.0, 2961.0, 3306.6 cm-
1. HRMS (TOF) (m/z): M+H+ calcd for C31H37N4O5 545.2764, found 545.2770.
(2S,4R)-Benzyl 2-((S)-1-(2-(dimethylamino)ethylamino)-1-oxo-4-phenylbutan-2-ylcarbamoyl)-
4-hydroxypyrrolidine-1-carboxylate (20e) was synthesized according to general procedure from 19e (158
mg) and n-Bu4NF (1M solution in THF, 0.52 mL) in anh. THF (0.5 mL), yield was 111 mg (90.4%). Mp 136
o C. [α]D26.0 = 9.2 (c = 0.5, CHCl3). 1H NMR (400 MHz, CDCl3) δ 8.61 (d, J = 6.0, 1H), 8.03 (s, 1H), 7.41 –
7.05 (m, 10H), 5.30 (s, 1H), 5.06 (s, 2H), 4.59 (m, 3H), 3.83 (m, 1H), 3.67 (m, 2H), 3.01 (m, 2H), 2.67 (m,
2H), 2.62 – 2.51 (m, 5H), 2.41 (d, J = 6.6, 2H), 2.27 (m, 3H), 2.16 – 1.96 (m, 1H). IR (film) νmax 415.9, 432.7,
446.5, 700.2, 746.1, 1124.0, 1170.2, 1357.4, 1423.5, 1537.6, 1678.0, 2960.0, 3333.4 cm-1. HRMS (TOF)
(m/z): M+H+ calcd for C27H37N4O5497.2764, found 497.2759.
(2S,4R)-Benzyl
2-((S)-1-((2-(dimethylamino)ethyl)(methyl)amino)-1-oxo-4-phenylbutan-2-
ylcarbamoyl)-4-hydroxypyrrolidine-1-carboxylate (20f) was synthesized according to general procedure
from 19f (28 mg) and n-Bu4NF (1M solution in THF, 0.075 mL) in anh. THF (0.5 mL), yield was 17.6 mg
26.0
1
(92.7%) as a syrup. [α]D = -20.1 (c = 2, CHCl3). H NMR (400 MHz, CDCl3) δ 7.44 – 6.93 (m, 11H), 5.10
(m, 2H), 4.86 (m, 1H), 4.74 – 4.33 (m, 3H), 3.65 (m, 3H), 3.04 – 2.72 (m, 3H), 2.69 – 2.22 (m, 8H), 2.22 – 2.05
(m, 3H), 1.95 (m, 2H), 1.23 (m, 3H). IR (film) νmax 413.0, 431.5, 444.3, 455.2, 700.0, 740.2, 1120.4, 1170.1,
1231.6, 1355.9, 1417.0, 1456.3, 1490.0, 1541.4, 1638.3, 1702.3, 2874.6, 2960.5, 3286.3 cm-1. HRMS (TOF)
(m/z): M+H+ calcd for C28H39N4O5511.2920, found 511.2930.
(2S,4R)-Benzyl
4-(tert-butyldimethylsilyloxy)-2-((S)-1-(2-cyanoethylamino)-1-oxo-4-
phenylbutan-2-ylcarbamoyl)pyrrolidine-1-carboxylate (22a) was synthesized following general
procedure from 17a (162 mg, 0.3 mmol) and 21a (25 mg, 0.36 mmol) yielding 117 mg (65.8%) 22a. Mp 167
oC.[α]D25.9 = -24.0 (c = 0.3, CHCl3). 1H NMR (400 MHz, CDCl3) δ 7.78 (s, 1H), 7.49 – 7.07 (m, 13H), 6.41 (d, J
= 7.7, 1H), 6.22 (d, J = 9.4, 1H), 5.42 – 4.93 (m, 2H), 4.63 – 4.19 (m, 3H), 4.08 (t, J = 7.5, 1H), 3.87 – 3.29 (m,
4H), 3.27 – 3.02 (m, 1H), 2.82 – 2.49 (m, 3H), 2.46 (m, 1H), 2.16 (m, 2H), 2.06 – 1.91 (m, 2H), 1.83 (m, 3H),
0.85 (s, 9H), 0.06 (s, 6H). IR (film) νmax 412.4, 418.8, 424.5, 430.0, 433.2, 437.6, 442.9, 451.7, 466.6, 474.3,
699.0, 1124.7, 1172.6, 1357.4, 1421.7, 1546.2, 1666.7, 2926.0, 3301.2 cm-1. HRMS (TOF) (m/z): M+H+ calcd
for C32H45N4O5Si 593.3159, found 593.3154.
(2S,4R)-Benzyl 2-((S)-1-(bis(2-cyanoethyl)amino)-1-oxo-4-phenylbutan-2-ylcarbamoyl)-4-(tert-
butyldimethylsilyloxy)pyrrolidine-1-carboxylate (22b) was synthesized by following general procedure
27.4
from 17a (162 mg, 0.3 mmol) and 21b (49 mg, 0.4 mmol) affording 101 mg (52.3%) 22b as syrup. [α]D
=
1
-20.0 (c = 0.5, CHCl3). H NMR (400 MHz, CDCl3) δ 0.042, 0.058 (each 3H, s, 2×CH3), 0.85 (9H, s, 3×CH3),
1.83 (2H, m, CH2), 2.00 (2H, m, CH2), 2.20 (1H, m, CH), 2.41 (1H, m, CH), 2.56 (1H, m, CH), 2.70 (2H, m, CH2),
3.19 (1H, m, CH), 3.36 (1H, m, CH), 3.57 (3H, m, CH & CH2), 4.41 (3H, m, CH & CH2), 5.19 (2H, m, CH2), 6.41
(1H, d, J = 9.6 Hz, NH), 7.19-7.5 (10H, m, PhH), 7.78 (1H, s, NH). IR (film) νmax 410.7, 414.6, 572.4, 700.9,
751.8, 837.3, 1126.1, 1171.3, 1203.0, 1357.7, 1421.8, 1497.7, 1680.0, 2249.2, 2348.8, 2929.8, 3338.7 cm-1.
HRMS (TOF) (m/z): M-(C3H3N)2+H+ calcd for C29H43N3O5Si 541.2972, found 541.3139.
(2S,4R)-Benzyl 2-(1-(allyl(2-cyanoethyl)amino)-1-oxo-4-phenylbutan-2-ylcarbamoyl)-4-(tert-
butyldimethylsilyloxy)pyrrolidine-1-carboxylate (22c) was synthesized following general procedure from
17a (162 mg, 0.3 mmol) and 21c, obtained according to [34] (40 mg, 0.36 mmol) affording 157 mg (82.7%)
27.4
1
22c as syrup. [α]D = -36.8 (c = 0.5, CHCl3). H NMR (400 MHz, CDCl3, δ, ppm) 0.044, 0.06 (each 3H, s,
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2×CH3), 0.85 (9H, s, 3×CH3), 1.91 (3H, m, CH & CH2), 2.25 (3H, m, CH& CH2), 2.59 (4H, m, 4×CH), 3.16 (1H, m,
CH), 3.53 (4H, m, 4×CH), 3.98 (2H, m, 2×CH), 4.44 (2H, m, CH2), 4.83 (1H, s, CH), 5.19 (4H, m, 4×CH), 5.66
(1H, br. s, NH), 7.2-7.5 (10H, m, PhH). IR (film) νmax 416.9, 427.7, 436.9, 668.8, 699.3, 741.8, 995.7, 1121.9,
1172.4, 1233.1, 1357.3, 1419.3, 1497.5, 1540.4, 1647.8, 1698.8, 2341.5, 2360.4, 2927.8, 3309.8 cm-1. HRMS
(TOF) (m/z): M+H+ calcd for C35H49N4O5Si 633.3472, found 633.3501.
(2S,4R)-Benzyl
4-(tert-butyldimethylsilyloxy)-2-((S)-1-(N-(2-cyanoethyl)-4-
methylphenylsulfonamido)-1-oxo-4-phenylbutan-2-ylcarbamoyl)pyrrolidine-1-carboxylate (22d) was
prepared according to general procedure from 17a (162 mg, 0.3 mmol) and 21d (65 mg, 0.31 mmol). It
yielded 103 mg (46.0%) 22d as syrup. [α]D25.9 = -28.7 (c = 0.3, CHCl3). 1H NMR (400 MHz, CDCl3) δ 7.91 (d, J
= 8.2, 2H), 7.76 (d, J = 8.3, 1H), 7.50 – 6.92 (m, 14H), 6.50 – 6.22 (m, 1H), 5.45 (m, 1H), 5.19 (m, 2H), 4.41
(m, 2H), 3.96 (m, 1H), 3.65 (m, 2H), 3.49 (m, 2H), 3.25 (m, 1H), 2.80 – 2.50 (m, 5H), 2.44 (m, 4H), 2.19 (m,
3H), 2.10 – 1.77 (m, 4H), 1.73 (m, 1H), 1.60 (m, 1H), 1.44 – 1.05 (m, 4H), 0.85 (s, 9H), 0.06 (2×s, 6H). IR (film)
νmax 412.9, 419.7, 424.0, 428.0, 433.3, 436.9, 441.1, 446.2, 453.0, 459.4, 548.5, 666.0, 699.8, 750.0, 814.7,
1091.7, 1163.3, 1358.7, 1419.9, 1540.2, 1684.8, 2927.8, 3337.9 cm-1. HRMS (TOF) (m/z): M+Na+ calcd for
C26H27N2O5SNa769.3067, found 769.3033.
(2S,4R)-Benzyl 4-(tert-butyldiphenylsilyloxy)-2-((S)-1-((cyanomethyl)(methyl)amino)-1-oxo-4-
phenylbutan-2-ylcarbamoyl)pyrrolidine-1-carboxylate (22e) was synthesized following general
procedure from 17b (200 mg, 0.3 mmol) and 21e (39 mg, 0.36 mmol) affording 183 mg (84.9%) 22e as
26.0
1
syrup. [α]D = -13.2 (c = 0.5, CHCl3). H NMR (400 MHz, DMSO) δ 7.81 – 6.87 (m, 21H), 5.31 – 4.99 (m,
2H), 4.93 – 4.66 (m, 1H), 4.62 – 4.34 (m, 3H), 4.28 – 4.16 (m, 1H), 4.14 – 4.02 (m, 1H), 3.78 – 3.65 (m, 2H),
3.66 – 3.51 (m, 1H), 3.49 – 3.24 (m, 1H), 3.06 – 2.77 (m, 3H), 2.71 – 2.55 (m, 1H), 2.55 – 2.36 (m, 1H), 2.35 –
2.09 (m, 2H), 2.05 (m, 1H), 2.01 – 1.79 (m, 2H), 1.78 – 1.59 (m, 1H), 1.26 (m, 3H), 1.02 (s, 9H). IR (film) νmax
419.8, 431.0, 439.5, 452.8, 458.5, 482.7, 612.8, 668.4, 701.2, 741.6, 822.2, 1022.1, 1112.6, 1169.5, 1265.5,
1355.0, 1416.2, 1653.5, 1701.1, 2360.0, 2857.4, 2930.4, 3313.9 cm-1. HRMS (TOF) (m/z): M+H+ calcd for
C42H49N4O5Si 717.3472, found 717.3456.
(2S,4R)-Benzyl 2-((S)-1-((cyanomethyl)(methyl)amino)-1-oxo-4-phenylbutan-2-ylcarbamoyl)-4-
hydroxypyrrolidine-1-carboxylate (23e) was obtained following general procedure from 22e (143 mg, 0.2
mmol) and n-Bu4NF (1M solution in THF, 0.28 mL) in anh. THF (2 mL) to get after column
o
26.0
1
chromatography 91 mg (95.1%) 23e. Mp 169 C. [α]D
= -18.8 (c = 0.5, CHCl3). H NMR (400 MHz,
DMSO) δ 7.82 – 6.88 (m, 11H), 5.31 – 4.98 (m, 2H), 4.94 – 4.64 (m, 1H), 4.60 – 4.33 (m, 3H), 4.28 – 4.16 (m,
1H), 4.13 – 4.02 (m, 1H), 3.75 – 3.64 (m, 2H), 3.66 – 3.51 (m, 1H), 3.49 – 3.24 (m, 1H), 3.06 – 2.77 (m, 3H),
2.71 – 2.55 (m, 1H), 2.55 – 2.36 (m, 1H), 2.35 – 2.09 (m, 2H), 2.05 (m, 1H), 2.01 – 1.79 (m, 2H), 1.78 – 1.59
(m, 1H), 1.26 (m, 3H). IR (film) νmax 419.8, 431.8, 439.6, 452.4, 458.4, 482.9, 612.1, 668.2, 701.7, 741.3,
822.5, 1021.1, 1113.6, 1168.5, 1265.5, 1355.0, 1414.2, 1652.4, 1703.0, 2361.4, 2856.8, 2930.3, 3318.1 cm-1.
HRMS (TOF) (m/z): M+H+ calcd for C26H30N4O5478.5407, found 478.5402.
(2S,4R)-Benzyl
2-((S)-1-(2-cyanoethylamino)-1-oxo-4-phenylbutan-2-ylcarbamoyl)-4-
hydroxypyrrolidine-1-carboxylate (23a) was obtained following general procedure from 22a (117 mg, 0.2
mmol) and n-Bu4NF (1M solution in THF, 0.28 mL) in anh. THF (2 mL). Column chromatography
o
26.3
1
purification yielded 20 mg (21.8%) 23a. Mp 179 C. [α]D = -12.8 (c = 0.5, CHCl3). H NMR (400 MHz,
CDCl3) δ 8.09 (m, 1H), 7.27 (m, 10H), 5.13 (s, 2H), 4.39 (m, 3H), 3.97 – 3.41 (m, 19H), 3.36 (s, 1H), 3.24 (m,
1H), 2.81 – 2.42 (m, 4H), 2.30 (m, 1H), 2.18 (m, 2H), 1.95 (m, 1H), 1.69 (m, 1H), 1.26 (m, 1H). IR (film) νmax
431.2, 445.6, 474.2, 700.4, 999.0, 1087.5, 1132.6, 1202.3, 1356.0, 1436.3, 1542.6, 1638.2, 1660.7, 1680.8,
2360.8, 2938.5, 3394.8 cm-1. HRMS (TOF) (m/z): M+H+ calcd for C26H31N4O5479.2294, found 479.2281.
(2S,4R)-Benzyl
2-((S)-1-(allyl(2-cyanoethyl)amino)-1-oxo-4-phenylbutan-2-ylcarbamoyl)-4-
hydroxypyrrolidine-1-carboxylate (23c) was synthesized following general procedure from 22c (143 mg,
0.3 mmol) and n-Bu4NF (1M solution in THF, 0.34 mL) in anh. THF (2 mL), yield was 70 mg (59.7%). Mp
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163 oC. [α]D26.3 = -41.2 (c = 0.5, CHCl3). 1H NMR (400 MHz, CDCl3) δ 7.60 – 6.73 (m, 11H), 5.64 (m, 1H), 5.15
(m, 4H), 4.79 (m, 1H), 4.48 (m, 2H), 3.98 (m, 1H), 3.67 (m, 5H), 3.11 (m, 1H), 3.02 – 2.37 (m, 6H), 2.19 (m,
2H), 1.95 (m, 2H), 1.32 (m, 1H), 1.00 (m, 1H). IR (film) νmax 417.3, 447.6, 699.8, 1122.4, 1357.2, 1419.1,
1634.1, 2926.6, 3306.7 cm-1. HRMS (TOF) (m/z): M+H+ calcd for C29H35N4O5519.2607, found 519.2599.
(2S,4R)-Benzyl
4-(tert-butyldimethylsilyloxy)-2-(1-cyano-3-phenylpropylcarba-
moyl)pyrrolidine-1-carboxylate (25) was synthesized following general procedure from 14 (190 mg, 0.5
[28]
26.0
mmol) and 24
(108 mg, 0.55 mmol). It isolated 102 mg (39.2%) 25 as syrup. [α]D = -40.8 (c = 0.5,
1
CHCl3). H NMR (400 MHz, CDCl3) δ 7.47 (d, J = 25.2, 1H, NH), 7.46 – 6.97 (m, 10H, PhH), 5.29 – 5.04 (m,
2H, CH2), 4.84 – 4.65 (m, 1H), 4.55 – 4.27 (m, 2H), 3.58 – 3.34 (m, 2H), 2.89 – 2.60 (m, 2H), 2.59 – 2.33 (m,
1H), 2.20 – 1.88 (m, J = 30.4, 16.5, 3H), 0.85 (s, 9H, t-Bu), 0.06 (2×s, 6H). IR (film) νmax 410.8, 415.2, 426.6,
433.9, 438.4, 698.6, 750.3, 1120.3, 1172.4, 1356.6, 1422.4, 1531.9, 1682.8, 2928.6, 3306.8 cm-1. HRMS
(TOF) (m/z): M+H+ calcd for C29H39N3NaO4Si 544.2608, found 544.2634.
(2S,4R)-Benzyl 2-((S)-1-cyano-3-phenylpropylcarbamoyl)-4-hydroxypyrrolidine-1-carboxylate (26)
was synthesized according to general procedure from 25 (75 mg, 0.144 mmol) and n-Bu4NF (1M solution in
THF, 0.22 mL) in anh. THF (1.5 mL). After column chromatography yield was 55 mg (94.3%) as a syrup.
[α]D26.0 = -40.2 (c = 1, CHCl3). 1H NMR (400 MHz, CDCl3) δ 7.78 (m, 1H), 7.71 (s, 1H), 7.43 – 6.94 (m, 11H),
5.10 (m, 2H), 4.66 (m, 1H), 4.37 (m, 2H), 3.90 – 3.15 (m, 3H), 2.67 (m, 2H), 2.39 – 1.59 (m, 5H). IR (film) νmax
413.7, 425.1, 698.9, 748.4, 999.2, 1030.3, 1082.6, 1123.1, 1172.5, 1279.9, 1356.6, 1421.0, 1498.0, 1533.1,
1680.9, 2927.3, 3030.6, 3301.3 cm-1. HRMS (TOF) (m/z): M+Na+ calcd for C23H25N3O4Na 430.1743, found
430.1725.
(2S,4R)-Benzyl
4-(tert-butyldimethylsilyloxy)-2-((S)-1-(2-(tert-
butyldimethylsilyloxy)phenylamino)-1-oxo-4-phenylbutan-2-ylcarbamoyl)pyrrolidine-1-carboxylate
(28) was obtained following general procedure from 17a (162 mg, 0.3 mmol) and 27 [27] (48 mg, 0.36 mmol)
affording 145 mg (73.7%) 28 as syrup. [α]D = -6.3 (c = 0.3, CHCl3). 1H NMR (400 MHz, CDCl3) δ 8.27 (s,
25.4
1H), 7.41 – 7.09 (m, 11H), 7.02 – 6.88 (m, 2H), 6.88 – 6.76 (m, 1H), 5.16 (s, 2H), 4.44 (d, J = 36.7, 3H), 3.53 (s,
2H), 2.79 – 1.83 (m, 9H), 1.26 (s, 6H), 1.00 (d, J = 4.9, 9H), 0.89 – 0.78 (m, 11H), 0.26 (d, J = 7.1, 6H), 0.12 –
0.01 (m, 6H). IR (film) νmax 414.8, 418.8, 423.7, 431.7, 447.8, 668.4, 749.9, 836.8, 1114.4, 1259.0, 1355.4,
1418.0, 1455.6, 1533.3, 1600.7, 1683.6, 2342.2, 2360.0, 2854.8, 2926.6, 3629.4 cm-1. HRMS (TOF) (m/z):
M+H+ calcd for C41H60N3O6Si2 746.4021, found 746.4047.
(2S,4R)-Benzyl
4-hydroxy-2-((S)-1-(2-hydroxyphenylamino)-1-oxo-4-phenylbutan-2-
ylcarbamoyl)pyrrolidine-1-carboxylate (29) was synthesized following general procedure from 28 (52 mg,
0.07 mmol) and n-Bu4NF (1M solution in THF, 0.21 mL) in anh. THF (1.5 mL), yield was 25 mg (66.3%).
o
25.4
1
Mp 127 C. [α]D = -20.2 (c = 0.5, CHCl3). H NMR (400 MHz, CDCl3) δ 9.25 (s, 1H), 8.99 (s, 1H), 7.40 –
6.69 (m, 17H), 5.19 – 4.90 (m, 2H), 4.42 (m, 4H), 3.69 – 3.47 (m, 2H), 3.40 (s, 1H), 2.99 – 2.83 (m, 1H), 2.68
(m, 4H), 2.20 (m, 4H), 1.95 (m, 1H). IR (film) νmax 411.9, 423.7, 428.3, 435.6, 443.9, 455.2, 697.9, 750.5,
1126.7, 1173.7, 1357.1, 1455.6, 1497.8, 1538.1, 1599.9, 1668.1, 2926.5, 3287.3 cm-1. HRMS (TOF) (m/z):
M+Na+ calcd for C29H31N3O6Na 540.2111, found 540.2124.
(2S,4R)-Benzyl
4-(tert-butyldimethylsilyloxy)-2-((S)-1-(2-(tert-
butyldimethylsilyloxy)ethylamino)-1-oxo-4-phenylbutan-2-ylcarbamoyl)pyrrolidine-1-carboxylate (31)
[27]
was obtained following general procedure from 17a (162 mg, 0.3 mmol) and 30
(58 mg, 0.33 mmol)
yielding 146 mg (69.8%) 31 as syrup. [α]D25.4 = -16.2 (c = 0.5, CHCl3). 1H NMR (400 MHz, CDCl3) δ 7.25 (m,
12H), 6.55 (s, 1H), 5.14 (m, 2H), 4.41 (m, 3H), 4.13 (q, J = 7.1, 1H), 3.69 (s, 3H), 3.44 (m, 3H), 2.67 (m, 2H),
2.60 – 2.32 (m, 2H), 2.24 (m, 2H), 2.06 (m, 3H), 1.04 – 0.71 (m, 18H), 0.18 – 0.02 (m, 12H). IR (film) νmax
416.0, 423.8, 428.1, 431.4, 435.6, 446.7, 455.0, 462.8, 473.3, 836.4, 1022.9, 1115.1, 1171.1, 1256.9, 1356.6,
1420.0, 1545.5, 1649.2, 2348.8 cm-1. HRMS (TOF) (m/z): M+H+ calcd for C37H60N3O6Si2 698.4021, found
698.4016.
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(2S,4R)-Benzyl
4-hydroxy-2-((S)-1-(2-hydroxyethylamino)-1-oxo-4-phenylbutan-2-yl-
carbamoyl)pyrrolidine-1-carboxylate (32) was synthesized following general procedure by deprotection of
31 (131 mg, 0.188 mmol) with n-Bu4NF (1M solution in THF, 0.56 mL) in anh. THF (2.5 mL), yield was 77
mg (87.1%). Mp 156 oC. [α]D25.3 = -36.6 (c = 0.2, CHCl3). 1H NMR (400 MHz, CDCl3) δ 7.61 – 6.99 (m, 12H),
5.20 – 5.00 (m, 2H), 4.61 – 4.31 (m, 3H), 3.49 (s, 2H), 3.36 (d, J = 4.7, 2H), 3.28 (d, J = 4.8, 1H), 3.19 – 3.03
(m, 5H), 2.77 – 2.57 (m, 2H), 2.48 (s, 1H), 2.35 (s, 1H), 2.25 (s, 1H), 2.15 – 1.83 (m, 3H). IR (film) νmax 415.0,
429.2, 699.3, 747.8, 1123.8, 1171.5, 1356.7, 1419.3, 1539.2, 1666.8, 2875.4, 2961.0, 3285.7 cm-1. HRMS
(TOF) (m/z): M+H+ calcd for C25H32N3O6 470.2291, found 470.2273.
(2S,4R)-Benzyl
4-(tert-butyldimethylsilyloxy)-2-((S)-1-(2,2-diethoxyethylamino)-1-oxo-4-
phenylbutan-2-ylcarbamoyl)pyrrolidine-1-carboxylate (34) was obtained following general procedure from
25.3
17a (162 mg, 0.3 mmol) and 33 (48 mg, 0.36 mmol). It isolated 145 mg (73.7%) 34. Mp 93 oC. [α]D = -
1
28.7 (c = 0.3, CHCl3). H NMR (400 MHz, CDCl3) δ 7.30 (m, 12H), 5.24 – 4.98 (m, 2H), 4.64 – 4.28 (m, 4H),
3.71 (q, J = 7.0, 4H), 3.58 – 3.29 (m, 4H), 2.80 – 2.43 (m, 2H), 2.34 – 2.14 (m, 2H), 2.05 (m, 4H), 1.23 (m, 6H),
0.85 (s, 9H), 0.041 & 0.059 (2×s, 6H). IR (film) νmax 413.1, 417.7, 421.2, 429.9, 437.0, 451.7, 457.0, 463.0,
668.4, 698.0, 752.2, 1126.1, 1356.9, 1423.2, 1540.1, 1669.4, 2342.8, 2360.0, 2926.9, 3304.4 cm-1. HRMS
(TOF) (m/z): M+Na+ calcd for C35H53N3O7SiNa 678.3550, found 678.3564.
(2S,4R)-benzyl
2-((S)-1-(2,2-diethoxyethylamino)-1-oxo-4-phenylbutan-2-ylcarbamoyl)-4-
hydroxypyrrolidine-1-carboxylate (35) was obtained by deprotection of 34 (122 mg, 0.181 mmol) with n-
25.0
Bu4NF (1M solution in THF, 0.55 mL) in anh. THF (2.5 mL), yield was 93 mg (95.1%). Mp 117 oC. [α]D
= -32.8 (c = 0.2, CHCl3). 1H NMR (400 MHz, CDCl3) δ 7.29 (m, 12H), 5.25 – 4.97 (m, 2H), 4.63 – 4.28 (m, 4H),
3.72 (q, J = 7.0, 4H), 3.57 – 3.27 (m, 4H), 2.80 – 2.43 (m, 2H), 2.33 – 2.14 (m, 2H), 2.05 (m, 4H), 1.23 (m, 6H).
IR (film) νmax 413.2, 417.5, 421.0, 430.9, 437.6, 451.5, 457.3, 463.6, 668.6, 698.1, 752.8, 1126.4, 1355.9,
1424.2, 1540.9, 1669.3, 2343.0, 2360.0, 2926.4, 3304.7 cm-1. HRMS (TOF) (m/z): M+H+ calcd for
C29H40N3O7542.2866, found 542.2867.
(2S,4R)-Benzyl
4-(tert-butyldiphenylsilyloxy)-2-((S)-1-(2-ethoxy-2-oxoethylamino)-1-oxo-4-
phenylbutan-2-ylcarbamoyl)pyrrolidine-1-carboxylate (38) was obtained by general method from 17b
(332 mg, 0.5 mmol) and glycine ethyl ester hydrochloride 37 (84 mg. 0.6 mmol). Column chromatographic
25.3
1
purification yielded 305 mg (81.0%) of product 38 as syrup. [α]D
= -2.2 (c = 1, CHCl3). H NMR (400
MHz, CDCl3) δ 7.74 – 6.95 (m, 20H), 6.68 (s, 1H), 6.54 (s, 1H), 6.41 (s, 1H), 5.29 (s, 1H), 5.11 (m, 2H), 4.49 (m,
2H), 4.41 – 3.98 (m, 4H), 3.96 – 3.62 (m, 2H), 3.52 (m, 1H), 3.43 – 3.29 (m, 1H), 3.24 – 3.10 (m, 1H), 2.81 –
2.42 (m, 2H), 2.38 – 1.71 (m, 5H), 1.25 (m, 3H), 1.03 (s, 9H). 13C NMR (101 MHz, CDCl3) δ 171.53, 169.76,
136.25, 135.58, 135.57, 129.98, 129.94, 128.57, 128.53, 128.51, 128.12, 127.85, 127.80, 127.68, 126.15,
99.98, 71.69, 71.34, 67.43, 60.00, 41.26, 38.29, 32.94, 31.96, 26.83, 26.79, 19.07, 19.04, 14.15. IR (film) νmax
424.2,435.0, 611.8, 665.3, 700.2, 740.8, 821.3, 899.2, 1021.2, 1111.5, 1197.6, 1353.2, 1426.6, 1454.5,
1497.3, 1538.0, 1651.7, 1747.1, 2349.0, 2856.8, 2930.6, 3296.2 cm-1. HRMS (TOF) (m/z): M+H+ calcd for
C43H52N3O7Si 750.3575, found 750.3604.
2-((S)-2-((2S,4R)-1-(Benzyloxycarbonyl)-4-(tert-butyldiphenylsilyloxy)pyrrolidine-2-
carboxamido)-4-phenylbutanamido)acetic acid (39) was obtained using procedure similar to synthesis 17a
from 224 mg of 38 and 0.358 mL of 1N LiOH aq. in 3 mL THF:MeOH = 1:1 mixture affording 0.206 g
24.0
1
(96%) product 39 which was pure for using in the next step. [α]D = -3.2 (c = 1, CH3OH). H NMR (400
MHz, CDCl3) δ 8.05 – 6.55 (m, 22H), 5.05 (m, 4H), 4.50 (m, 2H), 4.35 (m, 1H), 3.98 (m, 1H), 3.66 (m, 2H), 3.46
(m, 2H), 2.61 (m, 2H), 2.03 (m, 4H), 1.26 (m, 1H), 1.01 (2×s, 9H). IR (film) νmax 416.3, 597.1, 697.2, 1081.2,
1123.3, 1174.7, 1211.2, 1356.7, 1424.6, 1497.3, 1547.8, 1649.9, 2096.5, 3453.1 cm-1. HRMS (TOF) (m/z):
M+H+ calcd for C41H48N3O7Si 722.3262, found 722.3279.
This article is protected by copyright. All rights reserved.

(R)-Benzyl 2-(phenyl(tosyl)carbamoyl)pyrrolidine-1-carboxylate (42) (model reaction) was
[29]
obtained from Cbz-protected proline (40) and N-phenyl-4-toluensulfonamide (41)
using DCC as a
condensing agent in presence of DMAP, according to general procedure. DCC (155 mg, 0.75 mmol) was
added to the solution of 4-methyl-N-phenylbenzenesulfonamide (124 mg, 0.5 mmol), Cbz-proline (125 mg,
0.5 mmol) and DMAP (0.6 mg, 0.005 mmol) in anh. CH2Cl2 (5 mL) and reaction mixture was stirred for 22
h. The reaction mixture was filtered, mixed with 0.1 N HCl (5 mL), filtered again, organic phase was
separated, water solution was extracted with CH2Cl2 (3×1 mL), organic phases were combined, dried over
Na2SO4, filtered and concentrated in vacuo. A residue was purified by column chromatography on SiO2 (20
g), using EtOAc/Hexanes = 5/95, 10/90, 20/80, 30/70 and 40/60 (v/v) as eluant affording 192 mg of 42
(80.3%). Mp 163 o C. [α]D = 73.8 (c = 1, CHCl3). 1H NMR (400 MHz, CDCl3) δ 2.49 (3H, s, CH3), 3.49 (2H, m,
CH2), 3.58 (2H, m, CH2), 3.98 (1H, m, CH), 4.18 (1H, m, CH), 4.70 (1H, d, J = 11.7 Hz, CH), 5.01 (2H, m, CH2),
7.1-7.5 (10H, m, PhH). IR (film) νmax 419.4, 433.0, 448.1, 459.2, 468.4, 548.0, 570.2, 651.3, 677.7, 696.3,
752.1, 814.9, 982.9, 1027.8, 1086.4, 1118.8, 1172.5, 1250.1, 1356.4, 1415.5, 1451.9, 1488.7, 1541.9,
1594.8, 1712.6, 2341.5, 2360.5, 2928.3 cm-1. HRMS (TOF) (m/z): M+H+ calcd for C26H27N2O5S 501.1460,
found 501.1458.
Biological Evaluation
Effects of compounds on parasite development were determined by the flow cytometry [35]. P.
falciparum parasites (D6 clone or Chloroquine resistant W2 strain) were synchronized with 5% sorbitol and
cultured at 1% parasitemia and 2% hematocrit under the atmosphere of 3% O2, 6% CO2, and 91% N2 in
RPMI-1640 medium supplemented with 10% human serum. Inhibitors were added from DMSO stocks
(maximum concentration of DMSO equal to 0.1%). After 48 h, the culture medium was removed and
replaced with 1% formaldehyde in PBS pH 7.4, and cells were fixed for 48 h at room temperature. Fixed
parasites were transferred into 0.1% Triton-X-100 in PBS containing 1 nM YOYO-1 dye (Molecular
Probes). Parasitemia was determined from dot plots (forward scatter vs fluorescence acquired on FACSort
flow cytometer) with the help of CellQuest software (Beckton Dickinson). IC50 values for growth inhibition
were determined from plots of percent control parasitemia over inhibitor concentration with the help of
GraphPad Prism software.
All the compounds were simultaneously tested for cytotoxicity on VERO (monkey kidney
fibroblast) cells by the neutral red assay [36]. IC50 values for each compound were computed from the growth
inhibition curve.
Acknowledgments
This work was supported by CDC Cooperative Agreement UR3/CCU4186520-03 for financial support.
V. A. Bacherikov is thankful to University of Mississippi, MS, USA for supporting his post-doctoral
fellowship.
Supporting Information
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/cbdv.2017xxxxx
This article is protected by copyright. All rights reserved.

References
[1]
WHO, 2014, accessed January 16, 2015 ed., World Health Organization: Geneva, Switzerland, 2014,
p. 242.
[2]
[3]
[4]
M. Sajid, J. H. McKerrow, Molecular and biochemical parasitology 2002, 120, 1.
P. J. Rosenthal, P. S. Sijwali, A. Singh, B. R. Shenai, Current pharmaceutical design 2002, 8, 1659.
K. C. Pandey, Journal of parasitic diseases : official organ of the Indian Society for Parasitology 2011,
35, 94.
[5]
[6]
P. J. Rosenthal, Advances in experimental medicine and biology 2011, 712, 30.
M. Chugh, V. Sundararaman, S. Kumar, V. S. Reddy, W. A. Siddiqui, K. D. Stuart, P. Malhotra, Proc
Natl Acad Sci U S A 2013, 110, 5392.
[7]
D. Jani, R. Nagarkatti, W. Beatty, R. Angel, C. Slebodnick, J. Andersen, S. Kumar, D. Rathore, PLoS
pathogens 2008, 4, e1000053.
[8]
[9]
K. Chibale, C. C. Musonda, Current medicinal chemistry 2003, 10, 1863.
P. V. Desai, A. Patny, J. Gut, P. J. Rosenthal, B. Tekwani, A. Srivastava, M. Avery, Journal of medicinal
chemistry 2006, 49, 1576.
[10]
P. J. Rosenthal, W. S. Wollish, J. T. Palmer, D. Rasnick, The Journal of clinical investigation 1991, 88,
1467.
[11]
[12]
P. J. Rosenthal, G. K. Lee, R. E. Smith, The Journal of clinical investigation 1993, 91, 1052.
P. J. Rosenthal, J. E. Olson, G. K. Lee, J. T. Palmer, J. L. Klaus, D. Rasnick, Antimicrobial Agents and
Chemotherapy 1996, 40, 1600.
[13]
[14]
J. E. Olson, G. K. Lee, A. Semenov, P. J. Rosenthal, Bioorganic & medicinal chemistry 1999, 7, 633.
E. Verissimo, N. Berry, P. Gibbons, M. L. Cristiano, P. J. Rosenthal, J. Gut, S. A. Ward, P. M. O'Neill,
Bioorganic & medicinal chemistry letters 2008, 18, 4210.
[15]
[16]
D. J. Weldon, F. Shah, A. G. Chittiboyina, A. Sheri, R. R. Chada, J. Gut, P. J. Rosenthal, D. Shivakumar,
W. Sherman, P. Desai, J. C. Jung, M. A. Avery, Bioorganic & medicinal chemistry letters 2014, 24,
1274.
Y. A. Sabnis, P. V. Desai, P. J. Rosenthal, M. A. Avery, Protein science : a publication of the Protein
Society 2003, 12, 501.
This article is protected by copyright. All rights reserved.

[17]
[18]
[19]
P. V. Desai, A. Patny, Y. Sabnis, B. Tekwani, J. Gut, P. Rosenthal, A. Srivastava, M. Avery, Journal of
medicinal chemistry 2004, 47, 6609.
F. Shah, P. Mukherjee, J. Gut, J. Legac, P. J. Rosenthal, B. L. Tekwani, M. A. Avery, J Chem Inf Model
2011, 51, 852.
J. B. Ghasemi, F. Shiri, S. Pirhadi, Z. Heidari, Combinatorial chemistry & high throughput screening
2015, 18, 227.
[20]
[21]
S. Falgun, M. Prasenjit, D. Prashant, A. Mitchell, Current Computer Aided-Drug Design 2010, 6, 1.
B. R. Shenai, B. J. Lee, A. Alvarez-Hernandez, P. Y. Chong, C. D. Emal, R. J. Neitz, W. R. Roush, P. J.
Rosenthal, Antimicrobial Agents and Chemotherapy 2003, 47, 154.
[22]
[23]
[24]
R. Ettari, N. Micale, T. Schirmeister, C. Gelhaus, M. Leippe, E. Nizi, M. E. Di Francesco, S. Grasso, M.
Zappala, Journal of medicinal chemistry 2009, 52, 2157.
U. Machon, C. Buchold, M. Stempka, T. Schirmeister, C. Gelhaus, M. Leippe, J. Gut, P. J. Rosenthal,
C. Kisker, M. Leyh, C. Schmuck, Journal of medicinal chemistry 2009, 52, 5662.
A. Breuning, B. r. Degel, F. Schulz, C. Büchold, M. Stempka, U. Machon, S. Heppner, C. Gelhaus, M.
Leippe, M. Leyh, C. Kisker, J. Rath, A. Stich, J. Gut, P. J. Rosenthal, C. Schmuck, T. Schirmeister,
Journal of medicinal chemistry 2010, 53, 1951.
[25]
[26]
L. Huang, A. Lee, J. A. Ellman, Journal of medicinal chemistry 2002, 45, 676.
B. J. Lee, A. Singh, P. Chiang, S. J. Kemp, E. A. Goldman, M. I. Weinhouse, G. P. Vlasuk, P. J.
Rosenthal, Antimicrobial agents and chemotherapy 2003, 47, 3810.
[27]
[28]
E. J. Corey, A. Venkateswarlu, Journal of the American Chemical Society 1972, 94, 6190.
P. López-Serrano, J. A. Jongejan, F. van Rantwijk, R. A. Sheldon, Tetrahedron: Asymmetry 2001, 12,
219.
[29]
[30]
K. K. Park, J. J. Lee, J. Ryu, Tetrahedron 2003, 59, 7651.
M. J. Chaparro, J. Vidal, I. Angulo-Barturen, J. M. Bueno, J. Burrows, N. Cammack, P. Castaneda, G.
Colmenarejo, J. M. Coteron, L. de Las Heras, E. Fernandez, S. Ferrer, R. Gabarro, F. J. Gamo, M.
Garcia, M. B. Jimenez-Diaz, M. J. Lafuente, M. L. Leon, M. S. Martinez, D. Minick, S. Prats, M.
Puente, L. Rueda, E. Sandoval, A. Santos-Villarejo, M. Witty, F. Calderon, ACS medicinal chemistry
letters 2014, 5, 657.
[31]
M. Calas, G. Cordina, J. Bompart, M. Ben Bari, T. Jei, M. L. Ancelin, H. Vial, Journal of medicinal
chemistry 1997, 40, 3557.
This article is protected by copyright. All rights reserved.

[32]
[33]
[34]
[35]
I. d. R. F. M. Negri, 1.1.0 ed., Milano, Italy, 22.04.2015.
I. Perillo, M. C. Caterina, J. López, A. Salerno, Synthesis 2004, 2004, 851.
C.-E. Yeom, M. J. Kim, B. M. Kim, Tetrahedron 2007, 63, 904.
P. S. Sijwali, P. J. Rosenthal, Proceedings of the National Academy of Sciences of the United States of
America 2004, 101, 4384.
[36]
H. Babich, E. Borenfreund, Applied and Environmental Microbiology 1991, 57, 2101.
This article is protected by copyright. All rights reserved.