Solid-phase library synthesis of reversed-statine type inhibitors of the malarial aspartyl proteases plasmepsin I and II

Article abstract of DOI:10.1016/S0968-0896(02)00568-0

With the aim to develop inhibitors of the plasmepsin I and II aspartic proteases of the malaria parasite Plasmodium falciparum, we have synthesized sets of libraries from novel reversed-statine isosteres, using a combination of solution phase and solid ph

Full text of DOI:10.1016/S0968-0896(02)00568-0

Bioorganic & Medicinal Chemistry 11 (2003) 827–841
Solid-Phase Library Synthesis of Reversed-Statine Type Inhibitors
of the Malarial Aspartyl Proteases Plasmepsin I and II
Anders Dahlgren,a Ingemar Kvarnstrom,a Lotta Vrang,b Elizabeth Hamelink,b
Anders Hallberg,c Asa Rosenquista,b,* and Bertil Samuelssonb,d,
*
aDepartment of Chemistry, Linkoping University, S-581 83 Linkoping, Sweden
¨
¨
bMedivir AB, Lunastigen 7, S-141 44 Huddinge, Sweden
cDepartment of Organic Pharmaceutical Chemistry, BMC, Uppsala University, Box 596, S-751 24 Uppsala, Sweden
dDepartment of Organic Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden
Received 6 September 2002; accepted 5 November 2002
Abstract—With the aim to develop inhibitors of the plasmepsin I and II aspartic proteases of the malaria parasite Plasmodium
falciparum, we have synthesized sets of libraries from novel reversed-statine isosteres, using a combination of solution phase and
solid phase chemistry. The synthetic strategy furnishes the library compounds in good to high overall yields and with excellent
stereochemical control throughout the developed route. The products were evaluated for their plasmepsin I and II inhibiting
properties and were found to exhibit modest but promising activity. The best inhibitor exhibits an in vitro activity of 28% inhibition
of plasmepsin II at an inhibitor concentration of 0.5 mM (Ki for Plm II=5.4 mM).
# 2003 Elsevier Science Ltd. All rights reserved.
Introduction
formed in the process of the parasite’s degradation of
hemoglobin, and this byproduct is therefore poly-
merized, forming what is known as hemozoin. Some of
the currently most widely used antimalarial drugs, for
example the weakly basic quinoline derivatives chlor-
oquine and mefloquine, exert their toxic effect on the
parasite by interfering with this sequestration process.3
Many of these drugs are no longer efficacious in most
parts of the world, due to the increased incidence of
drug resistant strains of P. falciparum able to restrict
accumulation of weak bases in the parasite’s digestive
vacuole.5 Other emerging antimalarial agents are arte-
misinin, involving free radical mechanisms causing
damage to the parasite’s digestive vacuoles,3 and pro-
phylactic drugs like proguanil, targeting the DNA
synthesis of the parasite in the liver stage.6
Malaria, which is transmitted by the Anopheles mos-
quito, is a major health threat in the world today with
enormous medical, social, and economic consequences.
Annual mortality worldwide from malaria is estimated
to be 2 million people. Over 40% of the world’s popu-
lation is possibly at risk, with 300–500 million indivi-
duals becoming infected each year.1 There are four
major species of the parasite, that is Plasmodium falci-
parum, P. vivax, P. malariae, and P. ovale, of which
P. falciparum is responsible for more than 95% of the
malaria-related morbidity and mortality.2
The malaria parasite has a complex life cycle that
requires a vertebrate host for the asexual reproduction
cycle and a female Anopheles mosquito for completion
of the sexual cycle.3 In the erythrocytic stage the para-
site invades the erythrocytes of its host, forms an acidic
vacuolar membrane, and consumes the hemoglobin as a
source of nutrients for growth and development.4 The
heme byproduct, which is toxic to the parasite, is
This underscores the pressing need for new generations
of safe, low cost drugs, effective against resistant
malaria strains, which can be used for both prophylactic
and therapeutic treatment of malaria.
The degradation of hemoglobin is mainly mediated by
the cysteine proteases falcipain 1–3 and the aspartic
proteases plasmepsin I and II (Plm I and II), expressed
by the parasite.3,7 Furthermore, it has been shown that
*Corresponding authors. Tel.: +46-8-608-3104; fax: +46-8-608-3199;
e-mail: asa.rosenquist@medivir.se (A. Rosenquist); bertil.samuelsson@
medivir.se (B. Samuelsson)
0968-0896/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved.
PII: S0968-0896(02)00568-0

828
A. Dahlgren et al. / Bioorg. Med. Chem. 11 (2003) 827–841
inhibitors of aspartyl proteinases (plasmepsins) and
cysteinyl proteinases (falcipains) from the malaria para-
site P. falciparum are efficacious in cell and animal
models of malaria, indicating that these enzymes may be
suitable molecular targets for drug therapy.7a,8 Today at
least 10 aspartic protease genes have been identified in
the P. falciparum genome, potentially complicating the
picture of target selection and target redundancy.9
Potent peptide plasmepsin inhibitors have previously
been described which incorporate the hydro-
xyethylamine core I, or the statine-derived core II,
found in pepstatin A.10,11 We now report on the design
and synthesis of novel reversed-statine type isosteres,
(R,R)-III and (S,S)-III, which introduces a C-terminus
where only N-terminus isosteres previously have been
explored (Fig. 1).
Scheme 1. (a) 2,2-Dimethoxypropane, 10-camphorsulfonic acid, ace-
tone; (b) H2O2 (aq), CaCO3, H2O; (c) HCl (aq); (d) MeI, Cs2CO3,
DMF; (e) DEAD, Ph3P, pNO2-benzoic acid, THF; (f) NaOMe,
MeOH.
From carbohydrate-derived precursors, using high
yielding solution-phase reaction sequences in combi-
nation with well optimized multi-step solid-phase reac-
tions, a rapid and efficient synthetic route has been
developed for these novel potential plasmepsin inhibi-
tors. Good to high overall yields and excellent stereo-
chemical control have been achieved. The compounds
synthesized were evaluated for both Plm I and II inhi-
bitory activity (Table 3), and to the best of our knowl-
edge this is the first report describing a thorough
evaluation of Plm I inhibitors.
Results and Discussion
The synthetic objective was to furnish four scaffolds
which coupled to a solid support resin would be amen-
able to an array synthesis of compounds. For the
synthesis of the methyl (2R,3R)-4-azido-2-bromobenzy-
loxy-3-hydroxy-butyrate scaffolds (+)-7 (with bromo in
the para position) and (+)-8 (with bromo in the meta
position) (Scheme 2) commercially available d-(ꢀ)-iso-
ascorbic acid was reacted with racemic 10-cam-
phorsulfonic acid (CSA) and 2,2-dimethoxypropane in
acetone to afford compound 112 in 98% yield (Scheme
1). Oxidative cleavage with H2O2,13 acidic workup, fol-
lowed by methylation, using MeI and Cs2CO3, provided
Scheme 2. (a) pBrBnBr, Ag2O, KI, toluene; (b) mBrBnBr, Ag2O, KI,
toluene, 60 ꢁC; (c) Dowex H+, MeOH; (d) MsCl, pyridine, CH2Cl2,
0–8 ꢁC; (e) NaN3, DMF, 60 ꢁC.
the isopropylidene protected (2R,3R)-methyl ester (+)-
214 in 90% yield (Scheme 1).
The enantiomer, the isopropylidene protected (2S,3S)-
methyl ester (ꢀ)-2, used for the synthesis of the methyl
(2S,3S)-4-azido-2-bromobenzyloxy-3-hydroxy-butyrate
scaffolds (ꢀ)-7 and (ꢀ)-8 (with bromo in the para and
meta position, respectively) (Scheme 2), was synthesized
from commercially available methyl 3,4-O-isopropylidene-
l-threonate by inverting the free hydroxyl group using
Mitsunobu conditions with diethylazodicarboxylate
(DEAD), Ph3P, and p-nitrobenzoic acid, followed by
cleavage of the obtained p-nitrobenzoate ester with
NaOMe in MeOH to give (ꢀ)-215 in 90% yield (Scheme 1).
The free hydroxyl groups in (+)-2 and (ꢀ)-2 were sub-
sequently bromobenzylated with either p- or m-bromo-
benzyl bromide using Ag2O16 and a catalytic amount of
KI in toluene to give (+)-3, (ꢀ)-3, (+)-4, and (ꢀ)-4 in
yields ranging from 90 to 100%17 (Scheme 2). The iso-
propylidene groups were removed by treatment with the
acidic ion exchanger Dowex H+ in MeOH, providing
the diols (+)-5, (ꢀ)-5, (+)-6, and (ꢀ)-6 in 75–85%
yield.18 Selective mesylation of the primary hydroxyl
Figure 1. The structures of the hydroxyethylamine core (I) and the
statine-derived core (II) used in previously reported Plm inhibitors.
(R,R)-III and (S,S)-III represent the structures of the reversed-statine
based Plm inhibitors presented in this report.

A. Dahlgren et al. / Bioorg. Med. Chem. 11 (2003) 827–841
829
groups, using mesyl chloride and pyridine in CH2Cl2 at
0–8 ꢁC, followed by displacement of the mesylate groups
with azide, using NaN3 in DMF, delivered the four tar-
get scaffolds (+)-7, (ꢀ)-7, (+)-8, and (ꢀ)-8 in yields
ranging from 70 to 85%19 over two steps (Scheme 2).
aspartic protease inhibitors.10,24,25 The total yield over
the two steps was determined through cleavage of a
minor amount of product from the resin. In this case
KOSiMe3 in THF was used in the hydrolysis step. Clea-
vage was achieved through treatment with TFA/CH2Cl2/
EtOH to give compound 14 in 57% yield over three steps
from 10 (including the cleavage step) (Scheme 3).
Ellman and coworkers have previously reported on the
synthesis of the base stable DHP linker attached to a
Merrifield polystyrene resin, useful for the attachment
of hydroxyl groups.20 Employing this procedure pro-
vided 9 in 87% yield (loading efficiency: 87%)21 to
which the scaffolds (+)-7, (ꢀ)-7, (+)-8, and (ꢀ)-8 were
coupled20 to give the resins 10, 11, 12, and 13 in 73–85%
yield based on the loading efficiency (Scheme 3).
Table 1. The identities and selected data of the target compounds
with R,R configuration at the central core
The solid-phase reaction sequence commenced by
hydrolysis of the methyl esters, using either KOSiMe3 in
THF or LiOH in THF/MeOH/water.22 The use of
KOSiMe3 in THF resulted in modest yields of final pro-
ducts. Notably, with LiOH in THF/MeOH/water excel-
lent yields of final compounds were obtained
(compounds 16j–16l, 17a–17l, and 19–22 in Tables 1 and
2).23 The resin bound acids were coupled with several
amines using benzotriazol-1-yl-oxytripyrrolidinopho-
sphonium
N-methylmorpholine (NMM) in DMF. The amines used
hexafluorophosphate
(PyBOP)
and
R0
R00
Yielda (%)
were selected based on similarity to amines reported in
Compd
R
15a
15b
15c
15d
15e
15f
15g
15h
15i
15j
15k
15l
17a
17b
17c
17d
17e
17f
17g
17h
17i
17j
17k
17l
19
A
A
A
A
A
A
A
A
A
A
A
A
B
B
B
B
B
B
B
B
B
B
B
B
A
B
C
D
C
D
E
F
G
H
I
I
I
J
J
N
O
P
N
O
P
N
O
P
N
O
P
N
O
P
N
O
P
N
O
P
N
O
P
25
25
27
31
26
27
21
19
25
30
29
32
79
90
98
95
99
99
91
84
81
81
65
96
50
90
70
81
99
51
65
45
70
90
J
K
K
K
L
L
L
I
I
I
J
J
J
K
K
K
L
L
L
M
M
M
M
K
I
Q
Q
Q
Q
P
N
P
N
P
21
23b
25b
27b
29b
30c
32c
33c
35c
K
I
K
I
N
aTotal yield, including the cleavage step, from the loaded resins 10 and
12, respectively (Scheme 3).
bSynthesized in solution from its corresponding bromo compound,
using PhB(OH)2, (Ph3P)4Pd, and aqueous sodium carbonate in
refluxing 1,2-dimethoxyethane. The yields given refer to the last cou-
pling step in solution.
cAs b, but using thiophene or thiazole, (Ph3P)4Pd, and KOAc in N,N-
dimethyl-acetamide at 120 ꢁC.
Scheme 3. (a) (+)-7, (ꢀ)-7, (+)-8, (ꢀ)-8, respectively, PPTS, 1,2-
dichloroethane, 82 ꢁC; (b) KOSiMe3, THF; (c) LiOH, THF, MeOH,
H2O; (d) R0NH2, PyBOP, NMM, DMF; (e) SnCl2, PhSH, Et3N, THF;
(f) R00CO2H, PyBOP, HOBt, DIEA, DMF; (g) TFA, CH2Cl2, EtOH.

830
A. Dahlgren et al. / Bioorg. Med. Chem. 11 (2003) 827–841
Reduction of the azide functionality using SnCl2, thio-
phenol, and Et3N in THF,26 followed by coupling of the
free amine with selected carboxylic acids10,25 using
PyBOP, 1-hydroxybenzotriazole (HOBt), and N,N-dii-
sopropylethylamine (DIEA) in DMF,27 and subsequent
cleavage furnished the final products 15a–15l, 16a–16l,
17a–17l, 18a–18l, and 19–22 from silica gel column
chromatography (Scheme 3, Tables 1 and 2).
with PhB(OH)2 at the bromo-aryl moiety (Tables 1 and
2).
In our hands, solid-phase Suzuki and Heck-like cou-
plings resulted in very poor yields of the desired pro-
ducts. However, utilizing standard solution Suzuki
conditions, that is reacting the cleaved off bromo com-
pounds with PhB(OH)2, (Ph3P)4Pd and aqueous
Na2CO3 in refluxing 1,2-dimethoxyethane (DME),28
provided the biphenyls 23–29 in yields ranging from 51
to 99% from the corresponding bromo compounds 15i,
16j, 17a, and 19–22 (Tables 1 and 2).
The bromo-aryl moiety of the final products provides a
convenient handle to further diversify this set of com-
pounds by introducing other functional groups in this
position to probe interactions putatively extending from
the S1 into the S3 pocket of the plasmepsins. In view of
inhibition data of Plm I and II, compounds 15i, 16j, and
17a were selected for substitution of the bromo-aryl
moiety with phenyl, thiophen-2-yl, and thiazol-5-yl
(Tables 1 and 2). Additionally, the slightly active com-
pound 20 and its analogues 19, 21, and 22 were coupled
Compounds 15i, 16j, and 17a were also successfully
coupled with thiophene and thiazole in solution using
Heck-like conditions, that is, the bromo compounds
were treated with thiophene or thiazole, (Ph3P)4Pd, and
KOAc in N,N-dimethylacetamide (DMA) at 120 ꢁC29 to
give the thiophen-2-yl-benzyl and thiazol-5-yl-benzyl
compounds 30–35 in 45–90% yield from the corre-
sponding bromo compounds (Tables 1 and 2). The
position of attachment at the thiazole moiety was
Table 2. The identities and selected data of the target compounds
with S,S configuration at the central core
1
determined by H NMR.
Inhibition Data and Structure–Activity Relationships
All final compounds were tested for their plasmepsin
inhibitory properties, and the data of the most potent
inhibitors are outlined in Table 3.
Compd
R
R0
R00
Yielda (%)
16a
16b
16c
16d
16e
16f
16g
16h
16i
16j
16k
16l
18a
18b
18c
18d
18e
18f
18g
18h
18i
18j
18k
18l
20
A
A
A
A
A
A
A
A
A
A
A
A
B
B
B
B
B
B
B
B
B
B
B
B
A
B
C
D
C
E
G
I
I
I
J
J
N
O
P
N
O
P
N
O
P
N
O
P
N
O
P
N
O
P
N
O
P
N
O
P
23
29
31
21
35
19
24
26
25
95
99
99
22
14
14
7
14
10
11
16
16
10
9
Ki values were determined for only a few selected com-
pounds, that is 15i (Ki=5.4 mM for Plm II) and 16j
(Ki=7.3 mM for Plm II). From analysis of the data in
Tables 1–3 it appears to be a requirement of R,R con-
figuration in this carbohydrate based template series to
achieve Plm I inhibitory activity, whereas both R,R and
S,S configuration give compounds showing Plm II inhi-
bitory activity. Additionally, it is evident that the presence
of the phenethyl side chain I or the piperidine derived side
chain K in the P2 position (see Table 1 and Fig. 1) seems
to be preferred in terms of potency. Regarding the P1 and
P20 substituents, no structure–activity conclusions can be
drawn from the inhibitory data presented above.
J
K
K
K
L
L
L
I
I
I
J
J
J
K
K
K
L
L
L
M
M
M
M
L
L
L
Table 3. Plasmepsin inhibitory properties of the most potent target
compounds
9
Q
Q
Q
Q
N
N
N
82
89
83
51
95
60
67
22
24b
26b
28b
31c
34c
Compd Inh, Plm Ia Inh, Plm IIa Compd Inh, Plm Ia Inh, Plm IIa
(%)
(%)
(%)
(%)
aTotal yield, including the cleavage step, from the loaded resins 11 and
13, respectively (Scheme 3).
15a
15g
15h
15i
16j
17a
14
0
8
11
0
22
6
11
9
28
17
9
17h
17i
18a
18b
20
11
15
0
0
0
0
11
6
6
7
13
bSynthesized in solution from its corresponding bromo compound,
using PhB(OH)2, (Ph3P)4Pd, and aqueous sodium carbonate in
refluxing 1,2-dimethoxyethane. The yields given refer to the last cou-
pling step in solution.
24
0
cAs b, but using thiophene or thiazole, (Ph3P)4Pd, and KOAc in N,N-
dimethyl-acetamide at 120 ꢁC.
aInhibition at an inhibitor concentration of 0.5 mM.

A. Dahlgren et al. / Bioorg. Med. Chem. 11 (2003) 827–841
831
Finally, the modestly potent but promising target com-
pounds 15i, 16j, and 17a appear to be well suited can-
didates for future optimization within this series of Plm I
and II inhibitors. They are lead like30a and all fall within
the property ranges predictive for oral bioavailability.30
Moreover, they can readily be diversified using combi-
natorial synthesis to generate new focused libraries.
Noteworthy, these newly developed carbohydrate tem-
plates are ideally suited to explore binding properties of
different R-groups (Tables 1 and 2) to the Plm enzymes.
sequence of Plm II was cleaved off by preincubation in an
assay reaction buffer (100 mM sodium acetate buffer (pH
4.5), 10% glycerol and 0.01% Tween 20) at room tem-
perature for 40 min. The reaction was initiated by the
addition of 3 mM substrate (DABCYL-Glu-Arg-Nle-
Phe-Leu-Ser-Phe-Pro-EDANS, AnaSpec Inc, San Jose,
CA, USA) and hydrolysis was recorded as the increase in
fluorescence intensity over a 10-min time period, during
which the rate increased linearly with time. Stock solu-
tions of inhibitors in DMSO were serially diluted in
DMSO and added directly before addition of substrate,
giving a final DMSO concentration of 1%.
Conclusion
IC50-values were obtained by assuming competitive
inhibition and fitting a Langmuir isotherm (vi/vo=1/
(1+[I] /IC50)) to the dose response data (Grafit), where
vi and vo are the initial velocities for the inhibited and
uninhibited reaction respectively and [I] is the inhibitor
concentration.32 The Ki was subsequently calculated by
using Ki=IC50/(1+[S]/Km)33 and a Km value deter-
mined according to Michaelis–Menten.
We have identified new small molecule lead inhibitors
of the aspartic plasmepsin I and II proteases from
carbohydrate derived retro-statine templates. The syn-
thetic strategy has been focused on developing these
templates and their chemistries in solution, followed by
taking well optimized reaction sequences on to solid
phase. The chemistry used readily provides the target
compounds and offers the opportunity to easily diversify
the sets of compounds presented in this report. Some
members from the small libraries synthesized show mod-
est but promising activity, with the best inhibitors having
in vitro activities of 28% inhibition of Plm II (15i) and
22% inhibition of Plm I (17a) at 0.5 mM concentration.
The introduction of P10 substituents in the reversed-sta-
tine type inhibitors presented may be worth exploring in
order to enhance the affinity for the plasmepsins.
Solution phase experimentals
5,6-O-Isopropylidene-D-isoascorbic acid (1). To a sus-
pension of d-(ꢀ)-isoascorbic acid (10.00 g, 56.8 mmol)
in acetone (50 mL) were added 2,2-dimethoxypropane
(12.0 mL, 10.2 g, 97.9 mmol) and 10-camphorsulfonic
acid (CSA) (0.660 g, 2.84 mmol). The mixture was stir-
red for 1 h at room temperature after which the reaction
was quenched with Et3N (0.395 mL, 0.288 g,
2.84 mmol). The solvent was evaporated and the
remainder was purified by flash column chromato-
graphy (EtOAc with 1% HOAc) to give compound 1
(12.06 g, 98%) as white crystals.
Experimental
General methods
NMR spectra were recorded on a Varian 300 MHz
instrument using CDCl3 or MeOH-d4 with TMS as an
internal standard. Optical rotations were measured in
CHCl3 solutions on a Perkin–Elmer 141 polarimeter.
TLC was carried out on Merck precoated 60 F254 plates
using UV-light and charring with EtOH/H2SO4/HOAc/
p-anisaldehyde 90:3:1:2 for visualisation. Column chro-
matography was performed using silica gel 60
(0.040–0.063 mm, Merck). Organic phases were dried
over anhydrous magnesium sulfate. Concentrations
were performed under diminished pressure (1–2 kPa) at
a bath temperature of 40 ꢁC. All target compounds were
subjected to MALDI-TOF analyses, using a Voyager-
DE STR Biospectrometry Workstation with a-cyano-4-
hydroxycinnamic acid as reference.
Methyl (2R,3R)-3,4-O-isopropylidene-2,3,4-trihydroxy-
butyrate [(+)-2]. Compound 1 (12.12g, 56.1mmol) and
CaCO3 (12.35g, 123 mmol) were suspended in water
(125mL). The reaction mixture was stirred at 0ꢁC while
H2O2 (30%, 20.0 mL, 176 mmol) was added dropwise
during half an hour. The temperature was slowly raised to
40ꢁC. After 4 h, activated carbon (2.64 g) and Pd on acti-
vated carbon (10%, 0.148 g) were added and the mixture
was heated at 85ꢁC until a negative peroxide test was
obtained (after about 1 h). The resulting suspension was
filtered and evaporated to a volume of 25mL. Aqueous
HCl (0.3M) was added until pH 3 was reached, followed
by several extractions with CH2Cl2 and EtOAc. The
organic phases were pooled, dried, and evaporated and
the obtained carboxylic acid was dissolved in DMF
(100mL). Cs2CO3 (32.90g, 101 mmol) and MeI (5.24 mL,
11.95 g, 84.19 mmol) were added and the suspension was
stirred at room temperature for two h. Water saturated
with NH4Cl was added and the mixture was extracted
several times with Et2O and EtOAc. The organic phases
were pooled, dried, and evaporated and the remainder was
purified by flash column chromatography (toluene/EtOAc
6:1) to yield (+)-2 (9.59 g, 90%) as a slightly yellow oil.
Plasmepsin assay measurements
Pro-plasmepsin II was generously provided from Helena
Danielson (Department of Biochemistry, Uppsala Uni-
versity, Uppsala, Sweden). The expression and purifica-
tion of plasmepsin I will be published elsewhere.31 The
activities of plasmepsin I (Plm I) and plasmepsin II (Plm
II) were measured essentially as described previously,10
using a total reaction volume of 100 mL. The concen-
tration of pro-Plm II was 3 nM and the amount of Plm I
was adjusted to give similar catalytic activity. The pro-
Methyl (2S,3S)-3,4-O-isopropylidene-2,3,4-trihydroxy-
butyrate [(ꢀ)-2]. To a solution of methyl 3,4-O-iso-
propylidene-l-threonate (0.870 g, 4.58 mmol) in dry

832
A. Dahlgren et al. / Bioorg. Med. Chem. 11 (2003) 827–841
THF (15 mL) were added p-nitrobenzoic acid (1.23 g,
7.36 mmol) and Ph3P (1.91 g, 7.28 mmol). The reaction
flask was placed in a water bath at room temperature,
and a solution of diethyl azodicarboxylate (DEAD)
(1.15 mL, 1.29 g, 7.41 mmol) in dry THF (15 mL) was
added dropwise to the stirred solution during 30 min at
room temperature. The reaction solution was stirred
overnight at room temperature and was then evapo-
rated and purified by flash column chromatography
(toluene/EtOAc 6:1). The product was dissolved in
MeOH (20 mL) and was allowed to react with NaOMe
in MeOH (1 M, 2.3 mL, 2.3 mmol), which was slowly
added dropwise into the stirred solution at room tem-
perature. The solution was stirred at room temperature
for 30 min, after which it was neutralized with HOAc,
evaporated, and purified by flash column chromato-
graphy (toluene/EtOAc 6:1). This afforded compound
(ꢀ)-2 (0.780 g, 90%) as a colorless oil.
Methyl (2R,3R)-2-(4-bromobenzyloxy)-3,4-dihydroxy-bu-
tyrate [(+)-5]. To a solution of compound (+)-3
(1.25 g, 3.48 mmol) in MeOH (15 mL) was added a sus-
pension of Dowex-H+ (50ꢃ8, 20–50 mesh) in MeOH
(9 mL). The mixture was shaken for 2 h at room tem-
perature, after which the reaction mixture was filtered,
neutralized with Et3N, and evaporated. The crude pro-
duct was purified by flash column chromatography
(EtOAc/toluene 2:1) to give compound (+)-5 (0.897 g,
22
81%) as a colorless solid. (+)-5: ½aꢂD +58.5 (c 0.5,
1
CHCl3); H NMR (CDCl3, 300 MHz): d 3.72–3.78 (m,
2H), 3.80 (s, 3H), 3.99–4.03 (m, 1H), 4.10–4.15 (m, 1H),
4.45 (d, J=11.7 Hz, 1H), 4.62 (d, J=11.7 Hz, 1H), 7.21
(d, J=8.4 Hz, 2H), 7.47 (d, J=8.4 Hz, 2H); 13C NMR
(CDCl3, 75.5 MHz): d 52.3, 62.8, 71.7, 72.6, 79.6, 122.2,
.
129.7, 131.7, 136.2, 171.3. Anal. (C12H15BrO5 0.3E-
tOAc) C, H.
Methyl (2S,3S)-2-(4-bromobenzyloxy)-3,4-dihydroxy-bu-
tyrate [(ꢀ)-5]. Compound (ꢀ)-5 was synthesized from
(ꢀ)-3 in 85% yield according to the method for the
Methyl (2R,3R)-2-(4-bromobenzyloxy)-3,4-dihydroxy-
3,4-O-isopropylidene- butyrate [(+)-3]. To a solution of
compound (+)-2 (0.683g, 3.59mmol) in toluene (15 mL)
were added p-bromobenzyl bromide (3.18 g, 12.7 mmol),
Ag2O (2.52 g, 10.9 mmol), and KI (0.101 g, 0.608 mmol)
and the mixture was stirred at room temperature for
15min (some heat evolution was observed). The suspen-
sion was filtered, evaporated, and purified by flash column
chromatography (toluene/EtOAc 6:1) to give compound
22
preparation of (+)-5. (ꢀ)-5: ½aꢂD ꢀ60.5 (c 0.4, CHCl3).
Anal. (C12H15BrO5) C, H.
Methyl (2R,3R)-2-(3-bromobenzyloxy)-3,4-dihydroxy-bu-
tyrate [(+)-6]. Compound (+)-6 was synthesized from
(+)-4 in 75% yield according to the method for the
22
preparation of (+)-5. (+)-6: ½aꢂD +54.7 (c 0.5, CHCl3);
22
(+)-3 (1.27 g, 99%) as a colorless solid. (+)-3: ½aꢂD
1H NMR (CDCl3, 300 MHz): d 3.65–3.72 (m, 2H), 3.80
(s, 3H), 3.90–4.02 (m, 1H), 4.11–4.14 (m, 1H), 4.45 (d,
J=11.7 Hz, 1H), 4.72 (d, J=11.7 Hz, 1H), 7.18–7.29 (m,
2H), 7.46 (d, J=7.8 Hz, 1H), 7.51 (s, 1H); 13C NMR
(CDCl3, 75.5 MHz): d 52.5, 63.0, 72.0, 72.7, 79.8, 122.8,
126.7, 130.3, 131.2, 131.5, 139.4, 171.5. Anal.
(C12H15BrO5) C, H.
1
+41.7 (c 1.5, CHCl3); H NMR (CDCl3, 300 MHz): d
1.34 (s, 3H), 1.41 (s, 3H), 3.76 (s, 3H), 3.97–4.07 (m, 3H),
4.34 (app dd, J=5.4, 12.5 Hz, 1H), 4.45 (d, J=11.7 Hz,
1H), 4.62 (d, J=11.7 Hz, 1H), 7.22 (d, J=8.4 Hz, 2H),
7.47 (d, J=8.4 Hz, 2H); 13C NMR (CDCl3, 75.5 MHz): d
25.3, 26.5, 52.1, 66.1, 72.2, 75.9, 79.1, 110.0, 122.0, 129.6,
131.6, 136.0, 170.7. Anal. (C15H19BrO5) C, H.
Methyl (2S,3S)-2-(3-bromobenzyloxy)-3,4-dihydroxy-bu-
tyrate [(ꢀ)-6]. Compound (ꢀ)-6 was synthesized from
(ꢀ)-4 in 75% yield according to the method for the
Methyl (2S,3S)-2-(4-bromobenzyloxy)-3,4-dihydroxy-
3,4-O-isopropylidene-butyrate [(ꢀ)-3]. Compound (ꢀ)-3
was synthesized from (ꢀ)-2 in 100% yield according to
22
preparation of (+)-5. (ꢀ)-6: ½aꢂD ꢀ53.0 (c 0.4, CHCl3).
22
the method for the preparation of (+)-3. (ꢀ)-3: ½aꢂD
Anal. (C12H15BrO5) C, H.
ꢀ40.0 (c 2.8, CHCl3). Anal. (C15H19BrO5) C, H.
Methyl (2R,3R) - 4 - azido - 2 - (4 - bromobenzyloxy) - 3-
hydroxy-butyrate [(+)-7]. To a solution of compound
(+)-5 (0.741 g, 2.32 mmol) in dry CH2Cl2 (15 mL) was
added dry pyridine (0.75 mL, 0.737 g, 9.33 mmol). The
temperature was lowered to 0 ꢁC and mesyl chloride
(0.215 mL, 0.317 g, 2.77 mmol) was added dropwise.
The solution was stirred at 0–8 ꢁC overnight. The reac-
tion mixture was evaporated and then coevaporated
four times with toluene. Flash column chromatography
(EtOAc/toluene 2:1) afforded the monomesylated pro-
duct which was dissolved in dry DMF (10 mL). NaN3
(0.609 g, 9.37 mmol) was added and the suspension was
heated to 60 ꢁC and stirred overnight. The mixture was
cooled to room temperature, filtered, and evaporated.
Finally, the remainder was purified by flash column
chromatography (toluene/EtOAc 6:1) to give compound
(+)-7 (0.678g, 85%) as a colorless oil. (+)-7: ½aꢂ2D2 +56.8
(c 1.7, CHCl3); 1H NMR (CDCl3, 300 MHz): d 3.44–3.47
(m, 2H), 3.80 (s, 3H), 4.02–4.15 (m, 2H), 4.43 (d,
J=11.4 Hz, 1H), 4.70 (d, J=11.4 Hz, 1H), 7.24 (d,
J=8.4Hz, 2H), 7.49 (d, J=8.4 Hz, 2H); 13C NMR
Methyl (2R,3R)-2-(3-bromobenzyloxy)-3,4-dihydroxy-
Compound
3,4-O-isopropylidene-butyrate
[(+)-4].
(+)-4 was synthesized from (+)-2 and m-bromobenzyl
bromide in 95% yield according to the method for the
preparation of (+)-3, with the exception that the reac-
22
tion mixture was stirred overnight at 60 ꢁC. (+)-4: ½aꢂD
1
+37.6 (c 2.4, CHCl3); H NMR (CDCl3, 300 MHz): d
1.37 (s, 3H), 1.46 (s, 3H), 3.78 (s, 3H), 4.01–4.08 (m,
3H), 4.40 (app dd, J=5.8, 11.3 Hz, 1H), 4.50
(d,J=12.1 Hz, 1H), 4.66 (d, J=12.1 Hz, 1H), 7.17–7.30
(m, 2H), 7.44 (d, J=7.8 Hz, 1H), 7.53 (s, 1H); 13C NMR
(CDCl3, 75.5 MHz): d 25.6, 26.8, 52.4, 66.3, 72.3, 76.1,
79.5, 110.2, 122.8, 126.6, 130.2, 131.1, 131.3, 139.6,
170.9. Anal. (C15H19BrO5) C, H.
Methyl (2S,3S)-2-(3-bromobenzyloxy)-3,4-dihydroxy-
3,4-O-isopropylidene- butyrate [(ꢀ)-4]. Compound (ꢀ)-4
was synthesized from (ꢀ)-2 in 90% yield according to the
22
method for the preparation of (+)-4. (ꢀ)-4: ½aꢂD ꢀ36.5
.
(c 2.1, CHCl3). Anal. (C15H19BrO5 0.8CH2Cl2) C, H.

A. Dahlgren et al. / Bioorg. Med. Chem. 11 (2003) 827–841
833
(CDCl3, 75.5 MHz): d 52.4, 52.6, 71.3, 72.5, 78.8, 122.3,
129.8, 131.7, 135.7, 170.9. Anal. (C12H14BrN3O4) C, H, N.
shaken at room temperature for 72 h, followed by
washing with MeOH/H2O 3:1 (3ꢃ), MeOH (3ꢃ), THF
(3ꢃ), THF/HOAc 8:1 (5ꢃ), THF (3ꢃ), and MeOH
(3ꢃ).
Methyl (2S,3S) - 4 - azido - 2 - (4 - bromobenzyloxy) - 3-
hydroxy-butyrate [(ꢀ)-7]. Compound (ꢀ)-7 was synthe-
sized from (ꢀ)-5 in 80% yield according to the method
Peptide coupling no. 1 (typical procedure). The resin was
washed with DMF (2ꢃ) and was then allowed to swell
in DMF for 30 min. After drying a solution containing
the amine R0NH2 (0.4 M), benzotriazol-1-yl-oxytri-
22
for the preparation of (+)-7. (ꢀ)-7: ½aꢂD ꢀ55.9 (c 1.1,
.
.
CHCl3). Anal. (C12H14BrN3O4 0.1toluene 0.4DMF) C,
H, N.
pyrrolidino-phosphonium
hexafluorophosphate
Methyl (2R,3R) - 4 - azido - 2 - (3 - bromobenzyloxy) - 3-
hydroxy-butyrate [(+)-8]. Compound (+)-8 was syn-
thesized from (+)-6 in 70% yield according to the
(PyBOP) (0.4 M) and N-methylmorpholine (NMM)
(0.8 M) in DMF was added. The slurry was shaken
overnight at room temperature and was then dried and
washed with DMF (5ꢃ), MeOH (3ꢃ), and CH2Cl2
(5ꢃ).
22
method for the preparation of (+)-7. (+)-8: ½ꢀꢂD +53.3
(c 2.2, CHCl3); 1H NMR (CDCl3, 300 MHz): d
3.36–3.52 (m, 2H), 3.77 (s, 3H), 4.02–4.12 (m, 2H), 4.42
(d, J=11,7 Hz, 1H), 4.69 (d, J=11,7 Hz, 1H), 7.20–7.26
(m, 2H), 7.41 (d, J=7.8 Hz, 1H), 7.48 (s, 1H); 13C NMR
(CDCl3, 75.5 MHz): d 52.3, 52.5, 71.1, 72.1, 79.0, 122.4,
126.4, 129.9, 130.8, 131.0, 138.9, 170.8. Anal.
(C12H14BrN3O4) C, H, N.
Reduction of the azide functionality (typical procedure).
The resin was washed with dry THF (2ꢃ) and was
allowed to swell in dry THF for 30 min. It was then
dried and a solution of anhydrous SnCl2 (0.2 M), thio-
phenol (0.8 M), and Et3N (1.0 M) in dry THF was
added. After shaking for 4 h at room temperature the
resin was dried and washed with THF/H2O 2:1 (2ꢃ),
THF (3ꢃ), DMF (2ꢃ), and CH2Cl2 (3ꢃ).
Methyl (2S,3S) - 4 - azido - 2 - (3 - bromobenzyloxy) - 3 -
hydroxy-butyrate [(ꢀ)-8]. Compound (ꢀ)-8 was synthe-
sized from (ꢀ)-6 in 72% yield according to the method
22
for the preparation of (+)-7. (ꢀ)-8: ½ꢀꢂD ꢀ52.0 (c 1.8,
Peptide coupling no. 2 (typical procedure). The resin was
washed with DMF (2ꢃ) and was then allowed to swell
in DMF for 30 min. It was dried and a solution of the
carboxylic acid R00CO2H (0.2 M), 1-hydroxy-
benzotriazole (HOBt) (0.2 M), PyBOP (0.2 M), and
N,N-diisopropylethylamine (DIEA) (0.6 M) in DMF
was added. The mixture was shaken overnight at room
temperature and was then dried and washed with DMF
(3ꢃ), CH2Cl2 (3ꢃ), and MeOH (3ꢃ).
.
CHCl3). Anal. (C12H14BrN3O4 0.2CHCl3) C, H, N.
Preparation of DHP-resin
The DHP resin 9 was synthesized from the Merrifield
Resin HL (25) (100–200 mesh, chlorine substitution
1.60 mmol/g, 1% cross-linking) according to the proce-
dure described in ref 20. The loading and loading effi-
ciency were determined to be 0.88 mmol/g and 87%,
respectively, using the method outlined in ref 21.
Cleavage of the resins. Cleavage from the loaded resins
was achieved through shaking the resins with TFA/
CH2Cl2/99.5% EtOH 2:2:1 for 2 h at room tempera-
ture, followed by collection of the solvents. After
washings with CH2Cl2 for 5 min and MeOH for 5 min
all solvents were combined and evaporated. Coeva-
poration with toluene three times afforded the crude
products.
Preparation of scaffold loaded resins 10, 11, 12 and 13
The scaffolds (+)-7, (ꢀ)-7, (+)-8, and (ꢀ)-8 were cou-
pled to the DHP-resin 9 according to the procedure
described in ref 20. This gave the scaffold loaded resins
10, 11, 12, and 13 with the loadings and loading effi-
ciencies 0.63 mmol/g, 75%; 0.68 mmol/g, 82%;
0.61 mmol/g, 73%; and 0.71 mmol/g, 85%, respectively.
The target compounds
Purifications. The targets were purified, to eliminate
mostly residual polar baseline material, by silica column
chromatography using CHCl3/EtOH (99.5%) 19:1 as
eluent in the vast majority of cases, the exceptions being
the target compounds with basic side chains where the
mobile phase CHCl3/EtOH (99.5%) 19:1+3% MeOH
saturated with NH3 was utilized.
General procedures for solid-phase reactions
Hydrolysis of the methyl ester functionality (procedure a,
used for compounds 15a–15l, 16a–16i and 18a–18l, typi-
cal procedure). The scaffold loaded resin was washed
with THF (2ꢃ) followed by swelling in dry THF for
30 min. The resin was dried and a solution of KOSiMe3
in THF (0.6 M) was added. The resin was shaken for 4 h
and was then dried and washed with THF (5ꢃ), THF/
HOAc (6:1) (4ꢃ), and THF (5ꢃ).
(2R,3R)-4-Azido-2-(4-bromobenzyloxy)-3-hydroxy-N-
phenethyl-butyramide (14). Compound 14 was cleaved
off after the first coupling step to establish the yield so
far (57%).
Hydrolysis of the methyl ester functionality, (procedure
b, used for compounds 16j–16l, 17a–17l, and 19–22, typi-
cal procedure). The scaffold loaded resin was washed
with THF (2ꢃ) followed by swelling in THF for 30 min.
The resin was dried and a solution of THF/[1 M LiOH
in (MeOH/H2O 7:1)] 3:1 was added. The slurry was
(2R,3R)-2-(4-Bromobenzyloxy)-3-hydroxy-4-pentanoyla-
22
mino-N-phenethyl-butyramide (15a). 15a: ½aꢂD +26.7 (c
1
0.5, CHCl3); H NMR (CDCl3, 300 MHz): d 0.91 (t,
J=7.3 Hz, 3H), 1.23–1.40 (m, 2H), 1.49–1.63 (m, 2H),

834
A. Dahlgren et al. / Bioorg. Med. Chem. 11 (2003) 827–841
2.19 (t, J=7.7 Hz, 2H), 3.27–3.36 (m, 1H), 3.47–3.68
(m, 3H), 3.71 (d, J=6.3 Hz, 1H), 3.82–3.90 (m, 1H),
4.35 (d, J=11.2 Hz, 1H), 4.49 (d, J=11.2 Hz, 1H), 6.01
(br s, 1H), 6.78 (br s, 1H), 7.05 (d, J=8.4 Hz, 2H),
7.13–7.35 (m, 5H), 7.45 (d, J=8.4 Hz, 2H); 13C NMR
(CDCl3, 75.5 MHz): d 13.9, 22.5, 28.0, 35.4, 36.5, 40.0,
41.4, 71.6, 73.6, 79.4, 122.7, 127.0, 128.9, 129.0, 130.1,
132.0, 135.8, 138.5, 171.2, 174.5. MS calcd for
C24H32BrN2O4 (M+H)+: 491.15. Found: 491.06. MS
calcd for C24H31BrN2O4Na (M+Na)+: 513.14. Found:
513.04. MS calcd for C24H31BrN2O4K (M+K)+:
529.11. Found: 529.01.
6.75–6.83 (m, 1H), 7.22 (d, J=8.4 Hz, 2H), 7.50 (d,
J=8.4 Hz, 2H), 7.63–7.85 (m, 4H). MS calcd for
C26H31BrN3O6 (M+H)+: 560.14. Found: 560.22. MS
calcd for C26H30BrN3O6Na (M+Na)+: 582.12. Found:
582.21. MS calcd for C26H30BrN3O6K (M+K)+:
598.10. Found: 598.18.
(2R,3R)-4-[(Benzo[1,3]dioxole-5-carbonyl)-amino]-2-(4-
bromobenzyloxy) - 3 - hydroxy - N - isobutyl - butyramide
(15f). 15f: 1H NMR (CDCl3, 300 MHz): d 0.89 (d,
J=6.9 Hz, 6H), 1.66–1.82 (m, 1H), 3.01–3.20 (m, 2H),
3.52–3.62 (m, 1H), 3.80–3.92 (m, 1H), 3.83 (d,
J=6.6 Hz, 1H), 4.01–4.09 (m, 1H), 4.57 (d, J=11.3 Hz,
1H), 4.72 (d, J=11.3 Hz, 1H), 6.02 (s, 2H), 6.62–6.71
(m, 1H), 6.78–6.84 (m, 1H), 6.82 (d, J=8.0 Hz, 1H),
7.23 (d, J=8.4 Hz, 2H), 7.48 (d, J=8.4 Hz, 2H),
7.64–7.84 (m, 2H). MS calcd for C23H28BrN2O6
(M+H)+: 507.11. Found: 507.11. MS calcd for
C23H27BrN2O6Na (M+Na)+: 529.10. Found: 529.10.
MS calcd for C23H27BrN2O6K (M+K)+: 545.07.
Found: 545.06.
(2R,3R)-2-(4-Bromobenzyloxy)-4-[3-(1,3-dioxo-1,3-dihy-
dro-isoindol-2-yl)-propionylamino]-3-hydroxy-N-phene-
thyl-butyramide (15b). 15b: 1H NMR (CDCl3,
300 MHz): d 2.62 (t, J=7.2 Hz, 2H), 2.82 (t, J=6.9 Hz,
2H), 3.25–3.40 (m, 1H), 3.42–3.65 (m, 3H), 3.75 (d,
J=6.6 Hz, 1H), 3.84–3.93 (m, 1H), 3.95 (t, J=7.2 Hz,
2H), 4.35 (d, J=11.3 Hz, 1H), 4.50 (d, J=11.3 Hz, 1H),
6.21 (br s, 1H), 6.90 (br s, 1H), 7.02 (d, J=8.4 Hz, 2H),
7.09–7.34 (m, 5H), 7.42 (d, J=8.4 Hz, 2H), 7.45–7.85
(m, 4H). MS calcd for C30H31BrN3O6 (M+H)+:
608.14. Found: 608.11. MS calcd for C30H30BrN3O6Na
(M+Na)+: 630.12. Found: 630.09. MS calcd for
C30H30BrN3O6K (M+K)+: 646.10. Found: 646.07.
(2R,3R)-2-(4-Bromobenzyloxy)-3-hydroxy-4-pentanoyla-
mino-N-(2-piperidin-1-yl-ethyl)-butyramide (15g). 15g:
1H NMR (CDCl3, 300 MHz): d 0.89 (t, J=7.5 Hz, 3H),
1.22–1.63 (m, 10H), 2.15 (t, J=7.2 Hz, 2H), 2.23–2.50
(m, 6H), 3.24–3.47 (m, 3H), 3.52–3.65 (m, 1H), 3.77 (d,
J=6.4 Hz, 1H), 3.86–3.97 (m, 1H), 4.54 (d, J=11.3 Hz,
1H), 4.60 (d, J=11.3 Hz, 1H), 6.10–6.21 (m, 1H),
7.05–7.15 (m, 1H), 7.27 (d, J=8.4 Hz, 2H), 7.47 (d,
J=8.4 Hz, 2H). MS calcd for C23H37BrN3O4 (M+H)+:
498.20. Found: 498.26. MS calcd for C23H36BrN3O4Na
(M+Na)+: 520.18. Found: 520.25.
(2R,3R)-4-[(Benzo[1,3]dioxole-5-carbonyl)-amino]-2-(4-
bromobenzyloxy) - 3 - hydroxy - N - phenethyl - butyramide
(15c). 15c: 1H NMR (CDCl3, 300 MHz): d 2.63 (d,
J=6.9 Hz, 2H), 3.46–3.70 (m, 3H), 3.73–3.85 (m, 1H),
3.79 (d, J=6.3 Hz, 1H), 3.95–4.07 (m, 1H), 4.37 (d,
J=11.3 Hz, 1H), 4.55 (d, J=11.3 Hz, 1H), 6.02 (s, 2H),
6.56–6.64 (m, 1H), 6.72–6.80 (m, 1H), 6.82 (d,
J=8.0 Hz, 1H), 7.04 (d, J=8.5 Hz, 2H), 7.12–7.34 (m,
7H), 7.42 (d, J=8.5 Hz, 2H). MS calcd for
C27H28BrN2O6 (M+H)+: 555.11. Found: 555.08. MS
calcd for C27H27BrN2O6Na (M+Na)+: 577.10. Found:
577.07. MS calcd for C27H27BrN2O6K (M+K)+:
593.07. Found: 593.04.
(2R,3R)-2-(4-Bromobenzyloxy)-4-[3-(1,3-dioxo-1,3-dihy-
dro-isoindol-2-yl)-propionylamino]-3-hydroxy-N-(2-piper-
idin-1-yl-ethyl)-butyramide (15h). 15h: 1H NMR
(CDCl3, 300 MHz): d 1.35–1.58 (m, 6H), 2.27–2.48 (m,
6H), 2.60 (t, J=6.9 Hz, 2H), 3.28–3.53 (m, 3H),
3.54–3.63 (m, 1H), 3.80 (d, J=6.5 Hz, 1H), 3.87–4.02
(m, 3H), 4.57 (d, J=11.3 Hz, 1H), 4.60 (d, J=11.3 Hz,
1H), 6.32–6.40 (m, 1H), 7.07–7.17 (m, 1H), 7.20 (d,
J=8.4 Hz, 2H), 7.42 (d, J=8.4 Hz, 2H), 7.47–7.87 (m,
4H). MS calcd for C29H36BrN4O6 (M+H)+: 615.18.
Found: 615.15. MS calcd for C29H35BrN4O6Na
(M+Na)+: 637.16. Found: 637.14. MS calcd for
C29H35BrN4O6K (M+K)+: 653.14. Found: 653.11.
(2R,3R)-2-(4-Bromobenzyloxy)-3-hydroxy-N-isobutyl-4-
pentanoylamino- butyramide (15d). 15d: 1H NMR
(CDCl3, 300 MHz): d 0.89 (d, J=6.9 Hz, 6H), 0.92 (t,
J=7.4 Hz, 3H), 1.22–1.43 (m, 2H), 1.53–1.67 (m, 2H),
1.66–1.82 (m, 1H), 2.20 (t, J=7.4 Hz, 2H), 3.00–3.19
(m, 2H), 3.32–3.42 (m, 1H), 3.62–3.74 (m, 1H), 3.78 (d,
J=6.6 Hz, 1H), 3.88–3.98 (m, 1H), 4.52 (d, J=11.3 Hz,
1H), 4.68 (d, J=11.3 Hz, 1H), 5.97–6.06 (m, 1H),
6.77–6.86 (m, 1H), 7.25 (d, J=8.4 Hz, 2H), 7.51 (d,
J=8.4 Hz, 2H). MS calcd for C20H32BrN2O4 (M+H)+:
443.15. Found: 443.18. MS calcd for C20H31BrN2O4Na
(M+Na)+: 465.14. Found: 465.17. MS calcd for
C20H31BrN2O4K (M+K)+: 481.11. Found: 481.14.
(2R,3R)-4-[(Benzo[1,3]dioxole-5-carbonyl)-amino]-2-(4-
bromobenzyloxy)-3-hydroxy-N-(2-piperidin-1-yl-ethyl)-
22
butyramide (15i). 15i: ½aꢂD +30.0 (c 0.6, CHCl3); 1H
NMR (CDCl3, 300 MHz): d 1.38–1.67 (m, 6H), 2.35–2.62
(m, 6H) 3.33–3.52 (m, 3H), 3.74–3.84 (m, 1H), 3.86 (d,
J=6.3 Hz, 1H), 4.02–4.08 (m, 1H), 4.55 (s, 2H), 6.02 (s,
2H), 6.72–6.83 (m, 1H), 6.80 (d, J=8.0 Hz, 1H), 7.20–
7.38 (m, 4H), 7.42 (d, J=8.5 Hz, 2H); 13C NMR (CDCl3,
75.5 MHz): d 24.0, 25.3, 35.5, 42.2, 54.5, 57.4, 71.5, 73.1,
80.4, 101.8, 107.8, 108.1, 121.8, 122.4, 128.6, 130.2,
131.9, 135.9, 148.1, 150.5, 167.4, 171.4. MS calcd for
C26H33BrN3O6 (M+H)+: 562.16. Found: 562.12. MS
calcd for C26H32BrN3O6Na (M+Na)+: 584.14. Found:
584.10. MS calcd for C26H32BrN3O6K (M+K)+:
600.11. Found: 600.08. Anal. (C26H32BrN3O6) C, H, N.
(2R,3R)-2-(4-Bromobenzyloxy)-4-[3-(1,3-dioxo-1,3-dihy-
dro-isoindol-2-yl)-propionylamino]-3-hydroxy-N-isobutyl-
1
butyramide (15e). 15e: H NMR (CDCl3, 300 MHz): d
0.91 (d, J=6.9 Hz, 6H), 1.69–1.82 (m, 1H), 2.62 (t,
J=7.0 Hz, 2H), 3.01–3.20 (m, 2H), 3.35–3.47 (m, 1H),
3.57–3.70 (m, 1H), 3.80 (d, J=6.6 Hz, 1H), 3.88–3.95
(m, 1H), 4.00 (t, J=7.0 Hz, 2H), 4.52 (d, J=11.3 Hz,
1H), 4.66 (d, J=11.3 Hz, 1H), 6.14–6.20 (m, 1H),

A. Dahlgren et al. / Bioorg. Med. Chem. 11 (2003) 827–841
835
(2R,3R)-2-(4-Bromobenzyloxy)-3-hydroxy-N-((1S,2R)-2-
hydroxy-indan-1-yl)-4-pentanoylamino-butyramide (15j).
15j: H NMR (CDCl3, 300 MHz): d 1.01 (t, J=7.2 Hz,
(2S,3S)-4-[(Benzo[1,3]dioxole-5-carbonyl)-amino]-2-(4-
bromobenzyloxy) - 3 - hydroxy - N - phenethyl - butyramide
(16c). 16c: NMR data: see compound 15c. MS calcd
for C27H28BrN2O6 (M+H)+: 555.11. Found: 555.15.
MS calcd for C27H27BrN2O6Na (M+Na)+: 577.10.
Found: 577.13.
1
3H), 1.27–1.36 (m, 2H), 1.55–1.63 (m, 2H), 2.23 (t,
J=6.8 Hz, 2H), 2.85 (dd, J=1.9, 16.8 Hz, 1H), 3.01 (dd,
J=5.5, 16.8 Hz, 1H), 3.20–3.31 (m, 1H), 3.43–3.53 (m,
1H), 3.91 (d, J=6.3 Hz, 1H), 3.90–4.03 (m, 1H), 4.43 (d,
J=11.3 Hz, 1H), 4.48–4.55 (m, 1H), 4.58 (d, J=11.3 Hz,
1H), 5.31 (dd, J=5.1, 9.1 Hz, 1H), 6.11–6.20 (m, 1H),
6.86–6.98 (m, 1H), 7.13 (d, J=8.4 Hz, 2H), 7.19–7.36
(m, 4H), 7.40 (d, J=8.4 Hz, 2H). MS calcd for
C25H32BrN2O5 (M+H)+: 519.15. Found: 519.09. MS
calcd for C25H31BrN2O5Na (M+Na)+: 541.13. Found:
541.06. MS calcd for C25H31BrN2O5K (M+K)+:
557.11. Found: 557.04.
(2S,3S)-2-(4-Bromobenzyloxy)-3-hydroxy-N-isobutyl-4-
pentanoylamino- butyramide (16d). 16d: NMR data: see
compound 15d. MS calcd for C20H32BrN2O4 (M+H)+:
443.15. Found: 443.20. MS calcd for C20H31BrN2O4Na
(M+Na)+: 465.14. Found: 465.19. MS calcd for
C20H31BrN2O4K (M+K)+: 481.11. Found: 481.16.
(2S,3S)-2-(4-Bromobenzyloxy)-4-[3-(1,3-dioxo-1,3-dihy-
dro-isoindol-2-yl)-propionylamino]-3-hydroxy-N-isobutyl-
butyramide (16e). 16e: NMR data: see compound 15e.
MS calcd for C26H31BrN3O6 (M+H)+: 560.14. Found:
560.20. MS calcd for C26H30BrN3O6Na (M+Na)+:
582.12. Found: 582.19. MS calcd for C26H30BrN3O6K
(M+K)+: 598.10. Found: 598.16.
(2R,3R)-2-(4-Bromobenzyloxy)-4-[3-(1,3-dioxo-1,3-dihy-
dro - isoindol - 2 - yl) - propionylamino] - 3 - hydroxy - N -
((1S,2R)-2-hydroxy-indan-1-yl)-butyramide (15k). 15k:
1H NMR (CDCl3, 300 MHz): d 2.60 (t, J=6.9 Hz, 2H),
2.85 (dd, J=1.9, 16.8 Hz, 1H), 3.01 (dd, J=5.5, 16.8 Hz,
1H), 3.42–3.57 (m, 2H), 3.92 (t, J=6.9 Hz, 2H), 4.02 (d,
J=6.5 Hz, 1H), 4.06–4.14 (m, 1H), 4.58 (d, J=11.3 Hz,
1H), 4.63 (d, J=11.3 Hz, 1H), 4.63–4.72 (m, 1H), 5.40
(dd, J=5.0, 9.0 Hz, 1H), 6.39–6.45 (m, 1H), 6.74–6.80
(m, 1H), 7.09–7.32 (m, 4H), 7.18 (d, J=8.4 Hz, 2H),
7.43 (d, J=8.4 Hz, 2H), 7.63–7.80 (m, 4H). MS calcd
for C31H31BrN3O7 (M+H)+: 636.13. Found: 636.19.
MS calcd for C31H30BrN3O7Na (M+Na)+: 658.12.
Found: 658.18. MS calcd for C31H30BrN3O7K
(M+K)+: 674.09. Found: 674.16.
(2S,3S)-4-[(Benzo[1,3]dioxole-5-carbonyl)-amino]-2-(4-
bromobenzyloxy) - 3 - hydroxy - N - isobutyl - butyramide
(16f). 16f: NMR data: see compound 15f. MS calcd for
C23H28BrN2O6 (M+H)+: 507.11. Found: 507.17. MS
calcd for C23H27BrN2O6Na (M+Na)+: 529.10. Found:
529.16. MS calcd for C23H27BrN2O6K (M+K)+:
545.07. Found: 545.13.
(2S,3S)-2-(4-Bromobenzyloxy)-3-hydroxy-4-pentanoyla-
mino-N-(2-piperidin-1-yl-ethyl)-butyramide (16g). 16g:
NMR data: see compound 15g. MS calcd for
C23H37BrN3O4 (M+H)+: 498.20. Found: 498.24. MS
calcd for C23H36BrN3O4Na (M+Na)+: 520.18. Found:
520.23.
(2R,3R)-4-[(Benzo[1,3]dioxole-5-carbonyl)-amino]-2-(4-
bromobenzyloxy)-3-hydroxy-N-((1S,2R)-2-hydroxy-in-
dan-1-yl)-butyramide (15l). 15l: 1H NMR (CDCl3,
300 MHz): d 2.92 (dd, J=1.8, 16.7 Hz, 1H), 3.20 (dd,
J=5.5, 16.7 Hz, 1H), 3.60–3.72 (m, 1H), 3.79–3.87 (m,
1H), 3.90 (d, J=6.6 Hz, 1H), 4.03–4.15 (m, 1H), 4.60
(d, J=11.3 Hz, 1H), 4.61–4.67 (m, 1H), 4.63 (d,
J=11.3 Hz, 1H), 5.43 (dd, J=5.1, 9.0 Hz, 1H), 6.03
(s, 2H), 6.57–6.63 (m, 1H), 6.78–6.85 (m, 1H), 6.81
(d, J=8.5 Hz, 1H), 7.10–7.32 (m, 8H), 7.43 (d,
J=8.4 Hz, 2H). MS calcd for C28H28BrN2O7
(M+H)+: 583.11. Found: 583.10. MS calcd for
C28H27BrN2O7Na (M+Na)+: 605.09. Found: 605.08.
MS calcd for C28H27BrN2O7K (M+K)+: 621.06.
Found: 621.06.
(2S,3S)-2-(4-Bromobenzyloxy)-4-[3-(1,3-dioxo-1,3-dihy-
dro-isoindol-2-yl)-propionylamino]-3-hydroxy-N-(2-piper-
idin-1-yl-ethyl)-butyramide (16h). 16h: NMR data: see
compound 15h. MS calcd for C29H36BrN4O6 (M+H)+:
615.18. Found: 615.24.
(2S,3S)-4-[(Benzo[1,3]dioxole-5-carbonyl)-amino]-2-(4-
bromobenzyloxy)-3-hydroxy-N-(2-piperidin-1-yl-ethyl)-
butyramide (16i). 16i: NMR data: See compound 15i.
MS calcd for C26H33BrN3O6 (M+H)+: 562.16. Found:
562.23. MS calcd for C26H32BrN3O6Na (M+Na)+:
584.14. Found: 584.22.
(2S,3S)-2-(4-Bromobenzyloxy)-3-hydroxy-4-pentanoyla-
mino-N-phenethyl-butyramide (16a). 16a: NMR data:
see compound 15a. MS calcd for C24H32BrN2O4
(M+H)+: 491.15. Found: 491.14. MS calcd for
C24H31BrN2O4Na (M+Na)+: 513.14. Found: 513.12.
MS calcd for C24H31BrN2O4K (M+K)+: 529.11.
Found: 529.10.
(2S,3S)-2-(4-Bromobenzyloxy)-3-hydroxy-N-((1S,2R)-2-
hydroxy-indan-1-yl)-4-pentanoylamino-butyramide (16j).
22
16j: ½aꢂD ꢀ62.3 (c 0.8, CHCl3); 1H NMR (CDCl3,
300 MHz): d 0.98 (t, J=7.2 Hz, 3H), 1.25–1.35 (m, 2H),
1.59–1.68 (m, 2H), 2.21 (t, J=6.8 Hz, 2H), 2.87 (dd,
J=1.9, 16.8 Hz, 1H), 3.07 (dd, J=5.5, 16.8 Hz, 1H),
3.24–3.35 (m, 1H), 3.44–3.55 (m, 1H), 3.93 (d,
J=6.3 Hz, 1H), 3.95–4.04 (m, 1H), 4.48 (d, J=11.3 Hz,
1H), 4.46–4.53 (m, 1H), 4.58 (d, J=11.3 Hz, 1H), 5.27
(dd, J=5.1, 9.1 Hz, 1H), 6.17–6.25 (m, 1H), 6.85–6.96
(m, 1H), 7.11 (d, J=8.4 Hz, 2H), 7.17–7.32 (m, 4H),
7.40 (d, J=8.4 Hz, 2H); 13C NMR (CDCl3, 75.5 MHz):
d 14.0, 22.7, 28.1, 35.6, 39.3, 40.0, 57.6, 71.8, 72.5, 73.5,
(2S,3S)-2-(4-Bromobenzyloxy)-4-[3-(1,3-dioxo-1,3-dihy-
dro-isoindol-2-yl)-propionylamino]-3-hydroxy-N-phene-
thyl-butyramide (16b). 16b: NMR data: see compound
15b. MS calcd for C30H31BrN3O6 (M+H)+: 608.14.
Found: 608.12. MS calcd for C30H30BrN3O6Na
(M+Na)+: 630.12. Found: 630.11. MS calcd for
C30H30BrN3O6K (M+K)+: 646.10. Found: 646.08.

836
A. Dahlgren et al. / Bioorg. Med. Chem. 11 (2003) 827–841
80.0, 122.7, 125.2, 126.1, 127.8, 129.0, 131.0, 132.5,
137.8, 141.6, 141.9, 171.2, 172.6. MS calcd for
C25H32BrN2O5 (M+H)+: 519.15. Found: 519.16. MS
calcd for C25H31BrN2O5Na (M+Na)+: 541.13. Found:
541.14. MS calcd for C25H31BrN2O5K (M+K)+:
557.11. Found: 557.11. Anal. (C25H31BrN2O5) C, H, N.
(2R,3R)-4-[(Benzo[1,3]dioxole-5-carbonyl)-amino]-2-(3-
bromobenzyloxy) - 3 - hydroxy - N - phenethyl - butyramide
(17c). 17c: 1H NMR (CDCl3, 300 MHz): d 2.65 (d,
J=6.9 Hz, 2H), 3.45–3.69 (m, 3H), 3.70–3.85 (m, 1H),
3.78 (d, J=6.3 Hz, 1H), 3.95–4.05 (m, 1H), 4.34 (d,
J=11.3 Hz, 1H), 4.56 (d, J=11.3 Hz, 1H), 6.01 (s, 2H),
6.55–6.65 (m, 1H), 6.68–6.81 (m, 1H), 6.82 (d,
J=8.0 Hz, 1H), 7.10–7.47 (m, 11H). MS calcd for
C27H28BrN2O6 (M+H)+: 555.11. Found: 555.08. MS
calcd for C27H27BrN2O6Na (M+Na)+: 577.10. Found:
577.06. MS calcd for C27H27BrN2O6K (M+K)+:
593.07. Found: 593.03.
(2S,3S)-2-(4-Bromobenzyloxy)-4-[3-(1,3-dioxo-1,3-dihy-
dro - isoindol - 2 - yl) - propionylamino] - 3 - hydroxy - N -
((1S,2R)-2-hydroxy-indan-1-yl)-butyramide (16k). 16k:
1H NMR (CDCl3, 300 MHz): d 2.58 (t, J=6.9 Hz, 2H),
2.90 (dd, J=1.9, 16.8 Hz, 1H), 3.00 (dd, J=5.5, 16.8 Hz,
1H), 3.45–3.57 (m, 2H), 3.94 (t, J=6.9 Hz, 2H), 4.05 (d,
J=6.5 Hz, 1H), 4.09–4.17 (m, 1H), 4.58 (d, J=11.5 Hz,
1H), 4.65 (d, J=11.5 Hz, 1H), 4.60–4.70 (m, 1H), 5.43
(dd, J=5.2, 9.1 Hz, 1H), 6.35–6.43 (m, 1H), 6.71–6.78
(m, 1H), 7.10–7.29 (m, 4H), 7.19 (d, J=8.4 Hz, 2H),
7.40 (d, J=8.4 Hz, 2H), 7.65–7.82 (m, 4H). MS calcd
for C31H31BrN3O7 (M+H)+: 636.13. Found: 636.11.
MS calcd for C31H30BrN3O7Na (M+Na)+: 658.12.
Found: 658.10. MS calcd for C31H30BrN3O7K
(M+K)+: 674.09. Found: 674.07.
(2R,3R)-2-(3-Bromobenzyloxy)-3-hydroxy-N-isobutyl-4-
pentanoylamino- butyramide (17d). 17d: 1H NMR
(CDCl3, 300 MHz): d 0.88 (d, J=6.9 Hz, 6H), 0.94 (t,
J=7.4 Hz, 3H), 1.20–1.41 (m, 2H), 1.53–1.66 (m, 2H),
1.68–1.82 (m, 1H), 2.20 (t, J=7.4 Hz, 2H), 3.01–3.20
(m, 2H), 3.32–3.43 (m, 1H), 3.61–3.72 (m, 1H), 3.80 (d,
J=6.6 Hz, 1H), 3.86–3.99 (m, 1H), 4.50 (d, J=11.3 Hz,
1H), 4.65 (d, J=11.3 Hz, 1H), 5.90–6.00 (m, 1H),
6.67–6.75 (m, 1H), 7.21–7.26 (m, 2H), 7.42–7.52 (m,
2H). MS calcd for C20H32BrN2O4 (M+H)+: 443.15.
Found: 443.16. MS calcd for C20H31BrN2O4Na
(M+Na)+: 465.14. Found: 465.15. MS calcd for
C20H31BrN2O4K (M+K)+: 481.11. Found: 481.12.
(2S,3S)-4-[(Benzo[1,3]dioxole-5-carbonyl)-amino]-2-(4-
bromobenzyloxy)-3-hydroxy-N-((1S,2R)-2-hydroxy-in-
dan-1-yl)-butyramide (16l). 16l: 1H NMR (CDCl3,
300 MHz): d 2.90 (dd, J=1.9, 16.8 Hz, 1H), 3.23 (dd,
J=5.4, 16.8 Hz, 1H), 3.63–3.72 (m, 1H), 3.80–3.89 (m,
1H), 3.92 (d, J=6.5 Hz, 1H), 4.04–4.17 (m, 1H), 4.62 (d,
J=11.3 Hz, 1H), 4.63–4.67 (m, 1H), 4.68 (d, J=11.3 Hz,
1H), 5.41 (dd, J=5.1, 9.1 Hz, 1H), 6.01 (s, 2H),
6.50–6.61 (m, 1H), 6.75–6.84 (m, 1H), 6.80 (d,
J=8.4 Hz, 1H), 7.12–7.30 (m, 8H), 7.41 (d, J=8.4 Hz,
2H). MS calcd for C28H28BrN2O7 (M+H)+: 583.11.
Found: 583.03. MS calcd for C28H27BrN2O7Na
(M+Na)+: 605.09. Found: 605.02. MS calcd for
C28H27BrN2O7K (M+K)+: 621.06. Found: 620.99.
(2R,3R)-2-(3-Bromobenzyloxy)-4-[3-(1,3-dioxo-1,3-dihy-
dro-isoindol-2-yl)-propionylamino]-3-hydroxy-N-isobutyl-
1
butyramide (17e). 17e: H NMR (CDCl3, 300 MHz): d
0.90 (d, J=6.9 Hz, 6H), 1.71–1.83 (m, 1H), 2.61 (t,
J=7.0 Hz, 2H), 3.00–3.22 (m, 2H), 3.31–3.43 (m, 1H),
3.57–3.70 (m, 1H), 3.82 (d, J=6.6 Hz, 1H), 3.89–3.93
(m, 1H), 4.02 (t, J=7.0 Hz, 2H), 4.54 (d, J=11.3 Hz,
1H), 4.68 (d, J=11.3 Hz, 1H), 6.16–6.23 (m, 1H),
6.73–6.80 (m, 1H), 7.22–7.52 (m, 4H), 7.65–7.83 (m,
4H). MS calcd for C26H31BrN3O6 (M+H)+: 560.14.
Found: 560.19. MS calcd for C26H30BrN3O6Na
(M+Na)+: 582.12. Found: 582.18. MS calcd for
C26H30BrN3O6K (M+K)+: 598.10. Found: 598.15.
(2R,3R)-2-(3-Bromobenzyloxy)-3-hydroxy-4-pentanoyla-
22
mino-N-phenethyl-butyramide (17a). 17a: ½aꢂD +29.2
1
(c 0.6, CHCl3); H NMR (CDCl3, 300 MHz): d 0.91 (t,
J=7.2 Hz, 3H), 1.33 (m, 2H), 1.58 (m, 2H), 2.17 (t,
J=7.7 Hz, 2H), 2.83 (t, J=6.8 Hz, 2H), 3.25–3.35 (m,
1H), 3.42–3.67 (m, 3H), 3.73 (d, J=6.3 Hz, 1H), 3.89 (br
s, 1H), 4.10–4.14 (m, 1H), 4.36 (d, J=11.3 Hz, 1H), 4.53
(d, J=11.3 Hz, 1H), 6.01 (br s, 1H), 6.77 (br s, 1H),
7.09–7.38 (m, 8H), 7.44 (d, J=7.5 Hz, 2H); 13C NMR
(CDCl3, 75.5 MHz): d 13.9, 22.5, 27.9, 35.5, 36.6, 40.0,
41.4, 71.7, 73.4, 79.8, 122.8, 126.8, 126.9, 128.8, 128.9,
130.4, 131.2, 131.5, 138.4, 139.0, 171.1, 174.5. MS calcd
for C24H32BrN2O4 (M+H)+: 491.15. Found: 491.20.
MS calcd for C24H31BrN2O4Na (M+Na)+: 513.14.
Found: 513.18. MS calcd for C24H31BrN2O4K
(2R,3R)-4-[(Benzo[1,3]dioxole-5-carbonyl)-amino]-2-(3-
bromobenzyloxy) - 3 - hydroxy - N - isobutyl - butyramide
(17f). 17f: 1H NMR (CDCl3, 300 MHz): d 0.90 (d,
J=6.9 Hz, 6H), 1.65–1.80 (m, 1H), 3.01–3.19 (m, 2H),
3.50–3.59 (m, 1H), 3.81–3.90 (m, 1H), 3.81 (d, J=6.6 Hz,
1H), 4.00–4.09 (m, 1H), 4.53 (d, J=11.3 Hz, 1H), 4.70 (d,
J=11.3Hz, 1H), 6.02 (s, 2H), 6.61–6.69 (m, 1H), 6.75–6.82
(m, 1H), 6.81 (d, J=8.0 Hz, 1H), 7.19–7.33 (m, 4H), 7.42–
7.52 (m, 2H). MS calcd for C23H28BrN2O6 (M+H)+:
507.11. Found: 507.18. MS calcd for C23H27BrN2O6Na
(M+Na)+: 529.10. Found: 529.17. MS calcd for
C23H27BrN2O6K (M+K)+: 545.07. Found: 545.15.
(M+K)+:
(C24H31BrN2O4) C, H, N.
529.11.
Found:
529.16.
Anal.
(2R,3R)-2-(3-Bromobenzyloxy)-3-hydroxy-4-pentanoyla-
mino-N-(2-piperidin-1-yl-ethyl)-butyramide (17g). 17g:
1H NMR (CDCl3, 300 MHz): d 0.90 (t, J=7.5 Hz, 3H),
1.20–1.61 (m, 10H), 2.12 (t, J=7.2 Hz, 2H), 2.23–2.49
(m, 6H), 3.25–3.49 (m, 3H), 3.52–3.64 (m, 1H), 3.79 (d,
J=6.4 Hz, 1H), 3.85–3.95 (m, 1H), 4.55 (d, J=11.3 Hz,
1H), 4.60 (d, J=11.3 Hz, 1H), 6.15–6.24 (m, 1H),
7.04–7.13 (m, 1H), 7.16–7.53 (m, 4H). MS calcd for
C23H37BrN3O4 (M+H)+: 498.20. Found: 498.27.
(2R,3R)-2-(3-Bromobenzyloxy)-4-[3-(1,3-dioxo-1,3-dihy-
dro-isoindol-2-yl)-propionylamino]-3-hydroxy-N-phene-
thyl-butyramide (17b). 17b: NMR data: see compound
18b. MS calcd for C30H31BrN3O6 (M+H)+: 608.14.
Found: 608.18. MS calcd for C30H30BrN3O6Na
(M+Na)+: 630.12. Found: 630.16. MS calcd for
C30H30BrN3O6K (M+K)+: 646.10. Found: 646.14.

A. Dahlgren et al. / Bioorg. Med. Chem. 11 (2003) 827–841
837
(2R,3R)-2-(3-Bromobenzyloxy)-4-[3-(1,3-dioxo-1,3-dihy-
dro-isoindol-2-yl)-propionylamino]-3-hydroxy-N-(2-piper-
idin-1-yl-ethyl)-butyramide (17h). 17h: 1H NMR
(CDCl3, 300 MHz): d 1.41–1.62 (m, 6H), 2.30–2.51 (m,
6H), 2.62 (t, J=6.9 Hz, 2H), 3.29–3.55 (m, 3H),
3.57–3.65 (m, 1H), 3.81 (d, J=6.5 Hz, 1H), 3.87–4.04
(m, 3H), 4.53 (d, J=11.3 Hz, 1H), 4.65 (d, J=11.3 Hz,
1H), 6.25–6.36 (m, 1H), 7.05–7.14 (m, 1H), 7.18–7.52
(m, 4H), 7.64–7.85 (m, 4H). MS calcd for C29H36BrN4O6
(M+H)+: 615.18. Found: 615.27. MS calcd for
C29H35BrN4O6Na (M+Na)+: 637.16. Found: 637.26.
J=5.0 Hz, 1H), 4.17–4.23 (m, 1H), 4.52–4.57 (m, 1H),
4.64 (s, 2H), 5.34 (dd, J=5.0, 9.0 Hz, 1H), 6.00 (s, 2H),
6.50–6.57 (m, 1H), 6.76 (d, J=8.3 Hz, 1H), 6.90–6.98
(m, 1H), 7.09–7.46 (m, 10H). MS calcd for
C28H28BrN2O7 (M+H)+: 583.11. Found: 583.08. MS
calcd for C28H27BrN2O7Na (M+Na)+: 605.09. Found:
604.05. MS calcd for C28H27BrN2O7K (M+K)+:
621.06. Found: 621.03.
(2S,3S)-2-(3-Bromobenzyloxy)-3-hydroxy-4-pentanoyla-
mino-N-phenethyl-butyramide (18a). 18a: NMR data:
see compound 17a. MS calcd for C24H32BrN2O4
(M+H)+: 491.15. Found: 491.16. MS calcd for
C24H31BrN2O4Na (M+Na)+: 513.14. Found: 513.15.
MS calcd for C24H31BrN2O4K (M+K)+: 529.11.
Found: 529.12.
(2R,3R)-4-[(Benzo[1,3]dioxole-5-carbonyl)-amino]-2-(3-
bromobenzyloxy)-3-hydroxy-N-(2-piperidin-1-yl-ethyl)-
22
1
butyramide (17i). 17i: ½aꢂD +23.2 (c 2.4, CHCl3); H
NMR (CDCl3, 300 MHz): 1.38–1.60 (m, 6H),
d
2.28–2.57 (m, 6H), 3.30–3.52 (m, 2H), 3.74–3.84 (m,
1H), 3.86 (d, J=6.0 Hz, 1H), 4.03–4.10 (m, 1H), 4.55 (d,
J=11.4 Hz, 1H), 4.61 (d, J=11.4 Hz, 1H), 6.01 (s, 2H),
6.75–6.85 (m, 1H), 6.80 (d, J=8.5 Hz, 1H), 7.17–7.38
(m, 4H), 7.42 (d, J=8.0 Hz, 1H), 7.49 (s, 1H); 13C NMR
(CDCl3, 75.5 MHz): d 24.2, 25.6, 35.7, 42.2, 54.4, 57.3,
71.4, 73.0, 80.6, 101.8, 107.8, 108.1, 121.8, 122.7, 126.9,
128.6, 130.3, 131.2, 131.5, 139.2, 148.1, 150.5, 167.4,
171.2. MS calcd for C26H33BrN3O6 (M+H)+: 562.16.
Found: 562.22. MS calcd for C26H32BrN3O6Na
(M+Na)+: 584.14. Found: 584.20.
(2S,3S)-2-(3-Bromobenzyloxy)-4-[3-(1,3-dioxo-1,3-dihy-
dro-isoindol-2-yl)-propionylamino]-3-hydroxy-N-phene-
22
thyl-butyramide (18b). 18b: ½aꢂD ꢀ21.0 (c 0.6, CHCl3);
1H NMR (CDCl3, 300 MHz): d 2.60 (t, J=7.2 Hz, 2H),
2.83 (t, J=6.9 Hz, 2H), 3.25–3.39 (m, 1H), 3.42–3.66
(m, 3H), 3.75 (d, J=6.6 Hz, 1H), 3.84–3.92 (m, 1H),
3.97 (t, J=7.2 Hz, 2H), 4.35 (d, J=11.3 Hz, 1H), 4.51
(d, J=11.3 Hz, 1H), 6.21 (br s, 1H), 6.75 (br s, 1H),
7.10–7.35 (m, 7H), 7.36 (s, 1H), 7.44 (d, J=8.0 Hz, 1H),
7.67–7.73 (m, 2H), 7.78–7.84 (m, 2H); 13C NMR
(CDCl3, 75.5 MHz): d 34.8, 35.3, 35.8, 40.3, 41.7, 71.6,
73.6, 80.2, 123.0, 123.7, 127.1, 127.2, 129.1, 129.2, 130.7,
131.4, 131.8, 132.4, 134.4, 138.7, 139.3, 168.5, 171.1,
171.2. MS calcd for C30H31BrN3O6 (M+H)+: 608.14.
Found: 608.13. MS calcd for C30H30BrN3O6Na
(M+Na)+: 630.12. Found: 630.12. MS calcd for
C30H30BrN3O6K (M+K)+: 646.10. Found: 646.09.
(2R,3R)-2-(3-Bromobenzyloxy)-3-hydroxy-N-((1S,2R)-2-
hydroxy-indan-1-yl)-4-pentanoylamino-butyramide (17j).
1
17j: H NMR (CDCl3, 300 MHz): d 1.01 (t, J=7.2 Hz,
3H), 1.20–1.31 (m, 2H), 1.52–1.61 (m, 2H), 2.22 (t,
J=6.8 Hz, 2H), 2.87 (dd, J=1.9, 16.8 Hz, 1H), 3.00 (dd,
J=5.5, 16.8 Hz, 1H), 3.20–3.31 (m, 1H), 3.43–3.55 (m,
1H), 3.87 (d, J=6.3 Hz, 1H), 3.91–4.05 (m, 1H), 4.40 (d,
J=11.3 Hz, 1H), 4.48–4.57 (m, 1H), 4.61 (d, J=11.3 Hz,
1H), 5.30 (dd, J=5.1, 9.1 Hz, 1H), 6.10–6.20 (m, 1H),
6.75–6.88 (m, 1H), 7.17–7.32 (m, 5H), 7.40–7.50 (m,
3H). MS calcd for C25H32BrN2O5 (M+H)+: 519.15.
Found: 519.17. MS calcd for C25H31BrN2O5Na
(M+Na)+: 541.13. Found: 541.16. MS calcd for
C25H31BrN2O5K (M+K)+: 557.11. Found: 557.13.
(2S,3S)-4-[(Benzo[1,3]dioxole-5-carbonyl)-amino]-2-(3-
bromobenzyloxy) - 3 - hydroxy - N - phenethyl - butyramide
(18c). 18c: NMR data: see compound 17c. MS calcd
for C27H28BrN2O6 (M+H)+: 555.11. Found: 555.15.
MS calcd for C27H27BrN2O6Na (M+Na)+: 577.10.
Found: 577.14. MS calcd for C27H27BrN2O6K
(M+K)+: 593.07. Found: 593.12.
(2R,3R)-2-(3-Bromobenzyloxy)-4-[3-(1,3-dioxo-1,3-dihy-
dro - isoindol - 2 - yl) - propionylamino] - 3 - hydroxy - N -
((1S,2R)-2-hydroxy-indan-1-yl)-butyramide (17k). 17k:
1H NMR (CDCl3, 300 MHz): d 2.55 (t, J=6.7 Hz, 2H),
2.92 (dd, J=1.9, 16.7 Hz, 1H), 3.03 (dd, J=5.5, 16.7 Hz,
1H), 3.40–3.54 (m, 2H), 3.92 (t, J=6.7 Hz, 2H), 4.01 (d,
J=6.6 Hz, 1H), 4.10–4.19 (m, 1H), 4.62 (d, J=11.5 Hz,
1H), 4.68 (d, J=11.5 Hz, 1H), 4.69–4.78 (m, 1H), 5.45
(dd, J=5.2, 9.1 Hz, 1H), 6.30–6.40 (m, 1H), 6.69–6.78
(m, 1H), 7.12–7.87 (m, 12H). MS calcd for
C31H31BrN3O7 (M+H)+: 636.13. Found: 636.12. MS
calcd for C31H30BrN3O7Na (M+Na)+: 658.12. Found:
658.10. MS calcd for C31H30BrN3O7K (M+K)+:
674.09. Found: 674.08.
(2S,3S)-2-(3-Bromobenzyloxy)-3-hydroxy-N-isobutyl-4-
pentanoylamino- butyramide (18d). 18d: NMR data: see
compound 17d. MS calcd for C20H32BrN2O4 (M+H)+:
443.15. Found: 443.21. MS calcd for C20H31BrN2O4Na
(M+Na)+: 465.14. Found: 465.19. MS calcd for
C20H31BrN2O4K (M+K)+: 481.11. Found: 481.16.
(2S,3S)-2-(3-Bromobenzyloxy)-4-[3-(1,3-dioxo-1,3-dihy-
dro-isoindol-2-yl)-propionylamino]-3-hydroxy-N-isobutyl-
butyramide (18e). 18e: NMR data: see compound 17e.
MS calcd for C26H31BrN3O6 (M+H)+: 560.14. Found:
560.21. MS calcd for C26H30BrN3O6Na (M+Na)+:
582.12. Found: 582.19. MS calcd for C26H30BrN3O6K
(M+K)+: 598.10. Found: 598.17.
(2R,3R)-4-[(Benzo[1,3]dioxole-5-carbonyl)-amino]-2-(3-
bromobenzyloxy)-3-hydroxy-N-((1S,2R)-2-hydroxy-in-
dan-1-yl)-butyramide (17l). 17l: 1H NMR (CDCl3,
300 MHz): d 2.92 (dd, J=1.9, 16.8 Hz, 1H), 3.12 (dd,
J=5.4, 16.8 Hz, 1H), 3.65–3.73 (m, 2H), 4.07 (d,
(2S,3S)-4-[(Benzo[1,3]dioxole-5-carbonyl)-amino]-2-(3-
bromobenzyloxy) - 3 - hydroxy - N - isobutyl - butyramide
(18f). 18f: NMR data: see compound 17f. MS calcd for
C23H28BrN2O6 (M+H)+: 507.11. Found: 507.17. MS
calcd for C23H27BrN2O6Na (M+Na)+: 529.10. Found:

838
A. Dahlgren et al. / Bioorg. Med. Chem. 11 (2003) 827–841
529.16. MS calcd for C23H27BrN2O6K (M+K)+:
545.07. Found: 545.12.
C28H28BrN2O7 (M+H)+: 583.11. Found: 583.06. MS
calcd for C28H27BrN2O7Na (M+Na)+: 605.09. Found:
605.04. MS calcd for C28H27BrN2O7K (M+K)+:
621.06. Found: 621.00.
(2S,3S)-2-(3-Bromobenzyloxy)-3-hydroxy-4-pentanoyla-
mino-N-(2-piperidin-1-yl-ethyl)-butyramide (18g). 18g:
NMR data: see compound 17g. MS calcd for
C23H37BrN3O4 (M+H)+: 498.20. Found: 498.19. MS
calcd for C23H36BrN3O4Na (M+Na)+: 520.18. Found:
520.17.
(2R,3R)-2-(4-Bromobenzyloxy)-N-(furan-2-yl-methyl)-3-
hydroxy-4-phenylacetylamino-butyramide (19). 19: 1H
NMR (MeOH-d4, 300 MHz): d 3.35–3.40 (m, 2H), 3.45
(s, 2H), 3.87 (d, J=4.6 Hz, 1H), 3.95–4.02 (m, 1H), 4.30
(d, J=15.4 Hz, 1H), 4.43 (d, J=15.4 Hz, 1H), 4.52 (d,
J=11.5 Hz, 1H), 4.61 Hz (d, J=11.5 Hz, 1H), 6.21–6.26
(m, 1H), 6.30–6.34 (m, 1H), 7.12 (d, J=8.4 Hz, 2H),
7.20–7.30 (m, 6H), 7.43 (d, J=8.4 Hz, 2H). MS calcd
for C24H26BrN2O5 (M+H)+: 501.10. Found: 501.09.
MS calcd for C24H25BrN2O5Na (M+Na)+: 523.08.
Found: 523.07. MS calcd for C24H25BrN2O5K
(M+K)+: 539.06. Found: 539.05.
(2S,3S)-2-(3-Bromobenzyloxy)-4-[3-(1,3-dioxo-1,3-dihy-
dro-isoindol-2-yl)-propionylamino]-3-hydroxy-N-(2-piper-
idin-1-yl-ethyl)-butyramide (18h). 18h: NMR data: see
compound 17h. MS calcd for C29H36BrN4O6 (M+H)+:
615.18. Found: 615.16. MS calcd for C29H35BrN4O6Na
(M+Na)+: 637.16. Found: 637.15.
(2S,3S)-4-[(Benzo[1,3]dioxole-5-carbonyl)-amino]-2-(3-
bromobenzyloxy)-3-hydroxy-N-(2-piperidin-1-yl-ethyl)-
butyramide (18i). 18i: NMR data: see compound 17i.
MS calcd for C26H33BrN3O6 (M+H)+: 562.16. Found:
562.22. MS calcd for C26H32BrN3O6Na (M+Na)+:
584.14. Found: 584.20.
(2S,3S)-2-(4-Bromobenzyloxy)-N-(furan-2-yl-methyl)-3-
hydroxy-4-phenylacetylamino-butyramide
(20).
20:
NMR data: see compound 19. MS calcd for
C24H26BrN2O5 (M+H)+: 501.10. Found: 501.04. MS
calcd for C24H25BrN2O5Na (M+Na)+: 523.08. Found:
523.02. MS calcd for C24H25BrN2O5K (M+K)+:
539.06. Found: 539.01.
(2S,3S)-2-(3-Bromobenzyloxy)-3-hydroxy-N-((1S,2R)-2-
hydroxy-indan-1-yl)-4-pentanoylamino-butyramide (18j).
1
18j: H NMR (CDCl3, 300 MHz): d 1.01 (t, J=7.2 Hz,
(2R,3R)-2-(3-Bromobenzyloxy)-N-(furan-2-yl-methyl)-3-
hydroxy-4-phenylacetylamino-butyramide (21). 21: 1H
NMR (MeOH-d4, 300 MHz): d 3.37–3.42 (m, 2H), 3.47
(s, 2H), 3.86 (d, J=4.7 Hz, 1H), 3.94–4.01 (m, 1H), 4.33
(d, J=15.4 Hz, 1H), 4.46 (d, J=15.4 Hz, 1H), 4.51 (d,
J=11.5 Hz, 1H), 4.60 Hz (d, J=11.5 Hz, 1H), 6.22–6.26
(m, 1H), 6.31–6.35 (m, 1H), 7.17–7.50 (m, 10H). MS
calcd for C24H26BrN2O5 (M+H)+: 501.10. Found:
501.08. MS calcd for C24H25BrN2O5Na (M+Na)+:
523.08. Found: 523.06. MS calcd for C24H25BrN2O5K
(M+K)+: 539.06. Found: 539.03.
3H), 1.22–1.31 (m, 2H), 1.54–1.63 (m, 2H), 2.20 (t,
J=6.8 Hz, 2H), 2.84 (dd, J=1.9, 16.9 Hz, 1H), 3.02 (dd,
J=5.5, 16.9 Hz, 1H), 3.19–3.31 (m, 1H), 3.40–3.51 (m,
1H), 3.86 (d, J=6.3 Hz, 1H), 3.85–4.01 (m, 1H), 4.42 (d,
J=11.3 Hz, 1H), 4.46–4.57 (m, 1H), 4.63 (d, J=11.3 Hz,
1H), 5.32 (dd, J=5.0, 9.1 Hz, 1H), 6.13–6.21 (m, 1H),
6.72–6.85 (m, 1H), 7.19–7.33 (m, 5H), 7.39–7.49 (m,
3H). MS calcd for C25H32BrN2O5 (M+H)+: 519.15.
Found: 519.05. MS calcd for C25H31BrN2O5Na
(M+Na)+: 541.13. Found: 541.03. MS calcd for
C25H31BrN2O5K (M+K)+: 557.11. Found: 557.02.
(2S,3S)-2-(3-Bromobenzyloxy)-N-(furan-2-yl-methyl)-3-
hydroxy-4-phenylacetylamino-butyramide
(2S,3S)-2-(3-Bromobenzyloxy)-4-[3-(1,3-dioxo-1,3-dihy-
dro - isoindol - 2 - yl) - propionylamino] - 3 - hydroxy - N -
((1S,2R)-2-hydroxy-indan-1-yl)-butyramide (18k). 18k:
1H NMR (CDCl3, 300 MHz): d 2.53 (t, J=6.5 Hz, 2H),
2.94 (dd, J=1.9, 16.7 Hz, 1H), 3.01 (dd, J=5.5, 16.7 Hz,
1H), 3.41–3.54 (m, 2H), 3.95 (t, J=6.5 Hz, 2H), 4.00 (d,
J=6.6 Hz, 1H), 4.11–4.19 (m, 1H), 4.60 (d, J=11.4 Hz,
1H), 4.67 (d, J=11.4 Hz, 1H), 4.70–4.78 (m, 1H), 5.42
(dd, J=5.1, 9.1 Hz, 1H), 6.32–6.45 (m, 1H), 6.71–6.76
(m, 1H), 7.14–7.85 (m, 12H). MS calcd for
C31H31BrN3O7 (M+H)+: 636.13. Found: 636.15. MS
calcd for C31H30BrN3O7Na (M+Na)+: 658.12. Found:
658.13. MS calcd for C31H30BrN3O7K (M+K)+:
674.09. Found: 674.10.
(22).
22:
NMR data: see compound 21. MS calcd for
C24H26BrN2O5 (M+H)+: 501.10. Found: 501.05. MS
calcd for C24H25BrN2O5Na (M+Na)+: 523.08. Found:
523.03. MS calcd for C24H25BrN2O5K (M+K)+:
539.06. Found: 539.00.
Suzuki coupling in solution, typical procedure. The
bromo compound (76.6 mmol), aqueous Na2CO3 (2 M,
128 mL, 255 mmol), PhB(OH)2 (28 mg, 230 mmol) and
(Ph3P)4Pd (6.9 mg, 6.0 mmol) were dissolved in freshly
distilled and degassed 1,2-dimetoxyethane (DME)
(6 mL). The solution was then refluxed overnight under
an argon atmosphere. The mixture was evaporated and
coevaporated with toluene three times, followed by
purification by silica column chromatography (see
above).
(2S,3S)-4-[(Benzo[1,3]dioxole-5-carbonyl)-amino]-2-(3-
bromobenzyloxy)-3-hydroxy-N-((1S,2R)-2-hydroxy-in-
dan-1-yl)-butyramide (18l). 18l: 1H NMR (CDCl3,
300 MHz): d 2.90 (dd, J=1.9, 16.9 Hz, 1H), 3.10 (dd,
J=5.5, 16.9 Hz, 1H), 3.63–3.71 (m, 2H), 4.05 (d,
J=5.0 Hz, 1H), 4.12–4.20 (m, 1H), 4.51–4.55 (m, 1H),
4.62 (s, 2H), 5.33 (dd, J=5.1, 9.0 Hz, 1H), 6.01 (s, 2H),
6.51–6.56 (m, 1H), 6.75 (d, J=8.5 Hz, 1H), 6.85–6.93
(m, 1H), 7.10–7.41 (m, 10H). MS calcd for
(2R,3R) - 2 - (Biphenyl - 4 - yl - methoxy) - N - (furan - 2 - yl -
methyl)-3-hydroxy-4-phenylacetylamino-butyramide (23).
23: NMR data: see compound 24. MS calcd for
C30H30N2O5Na (M+Na)+: 521.20. Found: 521.25. MS
calcd for C30H30N2O5K (M+K)+: 537.18. Found: 537.23.

A. Dahlgren et al. / Bioorg. Med. Chem. 11 (2003) 827–841
839
(2S,3S) - 2 - (Biphenyl - 4 - yl - methoxy) - N - (furan - 2 - yl -
methyl)-3-hydroxy-4-phenylacetylamino-butyramide (24).
J=6.8 Hz, 2H), 3.30–3.40 (m, 1H), 3.43–3.67 (m, 3H),
3.78 (d, J=6.4 Hz, 1H), 3.85–3.92 (m, 1H), 4.49 (d,
J=11.3 Hz, 1H), 4.63 (d, J=11.3 Hz, 1H), 5.85–5.95 (m,
1H), 6.77–6.85 (m, 1H), 7.11–7.72 (m, 14H). MS calcd
for C30H37N2O4 (M+H)+: 489.28. Found: 489.30. MS
calcd for C30H36N2O4Na (M+Na)+: 511.26. Found:
511.28. MS calcd for C30H36N2O4K (M+K)+: 527.23.
Found: 527.25.
22
1
24: ½aꢂD ꢀ19.2 (c 1.3, CHCl3); H NMR (MeOH-d4,
300 MHz): d 3.37–3.42 (m, 2H), 3.47 (s, 2H), 3.86 (d,
J=4.7 Hz, 1H), 3.94–4.01 (m, 1H), 4.33 (d, J=15.4 Hz,
1H), 4.46 (d, J=15.4 Hz, 1H), 4.51 (d, J=11.7 Hz, 1H),
4.60 Hz (d, J=11.7 Hz, 1H), 6.22–6.26 (m, 1H),
6.31–6.35 (m, 1H), 7.18–7.43 (m, 7H), 7.50–7.66 (m,
8H); 13C NMR (MeOH-d4, 75.5 MHz): d 35.7, 41.9,
42.7, 70.8, 72.6, 81.5, 107.0, 110.2, 126.8, 126.9, 127.3,
128.4, 128.7, 129.0, 131.8, 132.0, 132.6, 135.6, 136.4,
140.8, 142.1, 151.7, 170.9, 171.5. MS calcd for
C30H31N2O5 (M+H)+: 499.22. Found: 499.18. MS
calcd for C30H30N2O5Na (M+Na)+: 521.20. Found:
521.14.
Heck-like coupling in solution, typical procedure. The
bromo compound (21.3 mmol), thiophene or thiazol
(211 mmol), KOAc (6.0 mg, 61 mmol) and (Ph3P)4Pd
(5.0 mg, 4.3 mmol) were dissolved in degassed N,N-
dimethylacetamide (DMA) (2 mL). The solution was
stirred overnight at 120 ꢁC under an argon atmosphere,
after which the solvent was evaporated. The crude pro-
duct was purified by silica column chromatography (see
above).
(2R,3R) - 2 - (Biphenyl - 3 - yl - methoxy) - N - (furan - 2 - yl -
methyl)-3-hydroxy-4-phenylacetylamino-butyramide (25).
25: 1H NMR (MeOH-d4, 300 MHz): d 3.40–3.44 (m,
2H), 3.48 (s, 2H), 3.84 (d, J=4.7 Hz, 1H), 3.92–4.02 (m,
1H), 4.30 (d, J=15.4 Hz, 1H), 4.48 (d, J=15.4 Hz, 1H),
4.51 (d, J=11.3 Hz, 1H), 4.62 Hz (d, J=11.3 Hz, 1H),
6.21–6.25 (m, 1H), 6.32–6.36 (m, 1H), 7.17–7.70 (m,
15H). MS calcd for C30H30N2O5Na (M+Na)+: 521.20.
Found: 521.14. MS calcd for C30H30N2O5K (M+K)+:
537.18. Found: 537.11.
(2R,3R) - 4 - [(Benzo[1,3]dioxole - 5 - carbonyl) - amino] - 3 -
hydroxy-N-(2-piperidin-1-yl-ethyl)-2-(4-thiophen-2-yl-
benzyl)-butyramide (30). 30: 1H NMR (CDCl3,
300 MHz): d 1.38–1.70 (m, 6H), 2.30–2.58 (m, 6H)
3.33–3.55 (m, 2H), 3.55–3.84 (m, 2H), 3.86 (d,
J=6.6 Hz, 1H), 4.02–4.10 (m, 1H), 4.62 (s, 2H), 5.98 (s,
2H), 6.65–6.75 (m, 1H), 6.79 (d, J=8.5 Hz, 1H),
7.10–7.28 (m, 5H), 7.40 (d, J=8.4 Hz, 2H), 7.58 (d,
J=8.4 Hz, 2H). MS calcd for C30H36N3O6S (M+H)+:
566.23. Found: 566.22.
(2S,3S) - 2 - (Biphenyl - 3 - yl - methoxy) - N - (furan - 2 - yl -
methyl)-3-hydroxy-4-phenylacetylamino-butyramide (26).
26: NMR data: see compound 25. MS calcd for
C30H30N2O5Na (M+Na)+: 521.20. Found: 521.15. MS
calcd for C30H30N2O5K (M+K)+: 537.18. Found:
537.14.
(2S,3S)-3-Hydroxy-N-((1S,2R)-2-hydroxy-indan-1-yl)-4-
pentanoylamino-2-(4-thiophen-2-yl-benzyl)-butyramide
(31). 31: 1H NMR (CDCl3, 300 MHz): d 0.95 (t,
J=7.4 Hz, 3H), 1.23–1.35 (m, 2H), 1.55–1.65 (m, 2H),
2.18 (t, J=6.8 Hz, 2H), 2.95 (dd, J=1.9, 16.8 Hz, 1H),
3.20 (dd, J=5.5, 16.8 Hz, 1H), 3.50–3.57 (m, 1H),
3.62–3.70 (m, 1H), 3.84 (d, J=6.4 Hz, 1H), 3.98–4.05
(m, 1H), 4.62 (d, J=11.3 Hz, 1H), 4.64–4.72 (m, 1H),
4.70 (d, J=11.3 Hz, 1H), 5.43 (dd, J=5.0, 9.1 Hz, 1H),
5.89–5.95 (m, 1H), 6.81–6.90 (m, 1H), 7.07–7.33 (m,
7H), 7.38 (d, J=8.4 Hz, 2H), 7.58 (d, J=8.4 Hz, 2H).
MS calcd for C29H34N2O5SNa (M+Na)+: 545.21.
Found: 545.22.
(2R,3R)-4-[(Benzo[1,3]dioxole-5-carbonyl)-amino]-2-(bi-
phenyl-4-yl-methoxy)-3-hydroxy-N-(2-piperidin-1-yl-
ethyl)-butyramide (27). 27: 1H NMR (CDCl3,
300 MHz): d 1.38–1.70 (m, 6H), 2.35–2.60 (m, 6H) 3.33–
3.50 (m, 2H), 3.73–3.84 (m, 1H), 3.89 (d, J=6.6 Hz,
1H), 4.08–4.14 (m, 1H), 4.63 (s, 2H), 5.98 (s, 2H), 6.72–
6.83 (m, 1H), 6.78 (d, J=8.0 Hz, 1H), 7.20–7.50 (m,
9H), 7.58 (d, J=8.4 Hz, 2H). MS calcd for C32H38N3O6
(M+H)+: 560.28. Found: 560.25. MS calcd for
C32H37N3O6Na (M+Na)+: 582.26. Found: 582.24.
(2S,3S) - 2 - (Biphenyl - 4 - yl - methoxy) - 3 - hydroxy - N -
((1S,2R)-2-hydroxy-indan-1-yl)-4-pentanoylamino-butyr-
amide (28). 28: H NMR (CDCl3, 300 MHz): d 0.95 (t,
(2R,3R)-3-Hydroxy-4-pentanoylamino-N-phenethyl-2-(3-
thiophen-2-yl-benzyl)-butyramide (32). 32: 1H NMR
(CDCl3, 300 MHz): d 0.95 (t, J=7.4 Hz, 3H), 1.35 (m,
2H), 1.58 (m, 2H), 2.17 (t, J=7.6 Hz, 2H), 2.82 (t,
J=6.7 Hz, 2H), 3.24–3.35 (m, 1H), 3.43–3.64 (m, 3H),
3.78 (d, J=6.6 Hz, 1H), 3.90–3.99 (m, 1H), 4.41 (d,
J=11.3 Hz, 1H), 4.45 (d, J=11.3 Hz, 1H), 6.10–6.19 (m,
1H), 6.71–6.78 (m, 1H), 7.12–7.71 (m, 12H). MS calcd
for C28H35N2O4S (M+H)+: 495.23. Found: 495.24.
MS calcd for C28H34N2O4SNa (M+Na)+: 517.21.
Found: 517.23.
1
J=7.3 Hz, 3H), 1.25–1.35 (m, 2H), 1.58–1.65 (m, 2H),
2.20 (t, J=6.9 Hz, 2H), 2.95 (dd, J=1.8, 16.8 Hz, 1H),
3.20 (dd, J=5.5, 16.8 Hz, 1H), 3.44–3.60 (m, 1H),
3.61–3.72 (m, 1H), 3.90 (d, J=6.6 Hz, 1H), 3.95–4.05
(m, 1H), 4.60 (d, J=11.3 Hz, 1H), 4.63–4.72 (m, 1H),
4.78 (d, J=11.3 Hz, 1H), 5.39 (dd, J=5.1, 9.1 Hz, 1H),
6.10–6.20 (m, 1H), 6.75–6.84 (m, 1H), 7.17–7.78 (m,
13H). MS calcd for C31H36N2O5Na (M+Na)+: 539.25.
Found: 539.23. MS calcd for C31H36N2O5K (M+K)+:
555.23. Found: 555.20.
(2R,3R) - 4 - [(Benzo[1,3]dioxole - 5 - carbonyl) - amino] - 3 -
hydroxy-N-(2-piperidin-1-yl-ethyl)-2-(4-thiazol-5-yl-ben-
1
(2R,3R)-2-(Biphenyl-3-ylmethoxy)-3-hydroxy-4-penta-
noylamino-N-phenethyl-butyramide (29). 29: 1H NMR
(CDCl3, 300 MHz): d 0.90 (t, J=7.4 Hz, 3H), 1.34 (m,
2H), 1.60 (m, 2H), 2.15 (t, J=7.6 Hz, 2H), 2.80 (t,
zyl)-butyramide (33). 33: H NMR (CDCl3, 300 MHz):
d 1.31–1.62 (m, 6H), 2.30–2.55 (m, 6H) 3.33–3.53 (m,
2H), 3.55–3.65 (m, 1H), 3.82–3.87 (m, 1H), 3.89 (d,
J=6.6 Hz, 1H), 4.02–4.09 (m, 1H), 4.63 (s, 2H), 5.99 (s,

840
A. Dahlgren et al. / Bioorg. Med. Chem. 11 (2003) 827–841
2H), 6.65–6.78 (m, 1H), 6.80 (d, J=8.5 Hz, 1H),
7.10–7.21 (m, 1H), 7.22–7.70 (m, 6H), 8.04 (s, 1H), 8.77
(s, 1H). MS calcd for C29H35N4O6S (M+H)+: 567.23.
Found: 567.20.
(c) Dame, J. B.; Reddy, G. R.; Yowell, C. A.; Dunn, B. M.;
Kay, J.; Berry, C. Mol. Biochem. Parasitol. 1994, 64, 177.
8. (a) Rosenthal, P. J.; Olson, J. E.; Lee, K.; Palmer, J. T.
Antimicrob. Agents Chemother. 1996, 40, 1600. (b) Rosenthal,
P. J. Exp. Parasitol. 1995, 80, 272. (c) Rosenthal, P. J.;
McKerow, J. H.; Rasnick, D.; Leech, J. H. Mol. Biochem.
Parasitol. 1989, 35, 177. (d) Rosenthal, P. J.; Wollish, W. S.;
Palmer, J. T.; Rasnick, D. J. Clin. Invest. 1991, 88, 1467.
9. Coombs, G. H.; Goldberg, D. E.; Klemba, M.; Berry, C.;
Kay, J.; Mottram, J. C. Trends Parasitol. 2001, 17, 532.
10. See, for example: Haque, T. S.; Skillman, A. G.; Lee,
C. E.; Habashita, H.; Gluzman, I. Y.; Ewing, T. J. A.; Gold-
berg, D. E.; Kuntz, I. D.; Ellman, J. A. J. Med. Chem. 1999,
42, 1428.
11. Silva, A. M.; Lee, A. Y.; Gulnik, S. V.; Majer, P.; Col-
lins, J.; Bhat, T. N.; Collins, P. J.; Cachau, R. E.; Luker,
K. E.; Gluzman, I. Y.; Francis, S. E.; Oksman, A.; Goldberg,
D. E.; Erickson, J. W. Proc. Natl. Acad. Sci. U.S.A. 1996, 93,
10034.
12. See, for example: Abushanab, E.; Vemishetti, P.; Leiby,
R. W.; Singh, H. K.; Mikkilineni, A. B.; Wu, D. C-J., Saibaba,
R., Panzica, R. P. J. Org. Chem. 1988, 53, 2598 and references
therein.
(2S,3S)-3-Hydroxy-N-((1S,2R)-2-hydroxy-indan-1-yl)-4-
pentanoylamino-2-(4-thiazol-5-yl-benzyl)-butyramide
(34). 34: 1H NMR (CDCl3, 300 MHz): d 0.95 (t,
J=7.2 Hz, 3H), 1.30–1.39 (m, 2H), 1.62–1.70 (m, 2H),
2.21 (t, J=6.7 Hz, 2H), 2.95 (dd, J=1.8, 16.8 Hz, 1H),
3.22 (dd, J=5.5, 16.8 Hz, 1H), 3.45–3.57 (m, 1H),
3.63–3.72 (m, 1H), 3.87 (d, J=6.6 Hz, 1H), 3.98–4.05
(m, 1H), 4.64 (d, J=11.3 Hz, 1H), 4.66–4.71 (m, 1H),
4.73 (d, J=11.3 Hz, 1H), 5.43 (dd, J=5.0, 9.0 Hz, 1H),
6.00–6.09 (m, 1H), 6.79–6.87 (m, 1H), 7.05–7.58 (m,
8H), 8.07 (s, 1H), 8.78 (s, 1H). MS calcd for
C28H34N3O5S (M+H)+: 524.22. Found: 524.16. MS
calcd for C28H33N3O5SNa (M+Na)+: 546.20. Found:
546.15. MS calcd for C28H33N3O5K (M+K)+: 562.18.
Found: 562.12.
13. Wei, C. C.; De Bernardo, S.; Tengi, J. P.; Borgese, J.;
Weigele, M. J. Org. Chem. 1985, 50, 3462.
14. See, for example: Mayer, P.; Ahond, A.; Poupat, C.;
Potier, P. Bull. Soc. Chim. Fr. 1993, 130, 509.
15. See, for example: Joachimi, D.; Ohlmann, A.; Rettig, W.;
Tschierske, C. J. Chem. Soc., Perkin. Trans. 2 1994, 9, 2011.
16. The use of freshly made Ag2O proved to benefit the yields
of the reactions.
17. The benzylations with m-bromobenzyl bromide required
higher temperatures and longer reaction times compared to
the benzylations where p-bromobenzyl bromide was used.
18. Some lactonization could be observed during the course of
these reactions.
(2R,3R)-3-Hydroxy-4-pentanoylamino-N-phenethyl-2-(3-
thiazol-5-yl-benzyl)-butyramide (35). 35: 1H NMR
(CDCl3, 300 MHz): d 0.94 (t, J=7.3 Hz, 3H), 1.35 (m,
2H), 1.60 (m, 2H), 2.18 (t, J=7.7 Hz, 2H), 2.83 (t,
J=6.7 Hz, 2H), 3.45–3.54 (m, 1H), 3.57–3.75 (m, 3H),
3.78 (d, J=6.5 Hz, 1H), 4.05–4.18 (m, 1H), 4.43 (d,
J=11.3 Hz, 1H), 4.52 (d, J=11.3 Hz, 1H), 5.55–5.65 (m,
1H), 6.72–6.79 (m, 1H), 7.12–7.62 (m, 9H), 8.08 (s, 1H),
8.78 (s, 1H). MS calcd for C27H34N3O4S (M+H)+:
496.23. Found: 496.17. MS calcd for C27H33N3O4SNa
(M+Na)+: 518.21. Found: 518.16.
19. In the azide displacement step the m-bromo compounds
required slightly longer reaction times than the corresponding
p-bromo compounds.
Acknowledgements
20. Thompson, L. A.; Ellman, J. A. Tetrahedron Lett. 1994,
35, 9333.
21. Bunin, A. B. In The Combinatorial Index, Academic Press:
San Diego, 1998; p. 219.
22. Chen, Y. Unpublished results. For additional informa-
tion, contact: Dr. Yantao Chen, Department of Chemistry,
Linkoping University, S-581 83 Linkoping, Sweden.
23. In most cases, the crude products after cleavage from the
resin were contaminated only with a small amount of polar
baseline (according to TLC) material.
We greatly acknowledge Medivir AB for financial sup-
port and for performing the biological testings. We
would also like to thank Jussi Kangasmetsa and
Michael Pelcman at Medivir AB for valuable assistance
during MS analyses.
References and Notes
24. Alterman, M.; Bjorsne, M.; Muhlman, A.; Classon, B.;
Kvarnstrom, I.; Danielson, H.; Markgren, P.O.; Nillroth, U.;
Unge, T.; Hallberg, A.; Samuelsson, B. J. Med. Chem. 1998,
41, 3782.
25. Lee, C. E.; Kick, E. K.; Ellman, J. A. J. Am. Chem. Soc.
1998, 120, 9735.
1. Radding, J. A. Annu. Rep. Med. Chem. 1999, 34, 159.
2. Oaks, S. C., Jr., Mitchell, V. S., Pearson, G. W., Carpenter,
C. C. J., Eds. Malaria: Obstacles and Opportunities: AReport
of the Committee for the Study on Malaria Prevention and
Control: Status Review and Alternative Strategies, Division of
International Health, Institute of Medicine. National Academy:
Washington, DC, 1991.
´
26. Bartra, M.; Romea, P. L.; Urpı, F.; Vilarrasa, J. A. Tet-
rahedron 1990, 46, 587.
3. Francis, S. E.; Sullivan, D. J.; Goldberg, D. E. Annu. Rev.
Microbiol. 1997, 51, 97.
4. Scheibel, L. W.; Sherman, I. W. In Malaria, Wernsdofer,
W. H.; McGregor, I., Eds.; Churchill Livingstone: London,
1988; p. 219.
5. Slater, A. F. G. Pharmacol. Ther. 1993, 57, 203.
6. Wirth, D. F. Annu. Rep. Med. Chem. 1999, 34, 349.
7. (a) Francis, S. E.; Gluzman, I. Y.; Oksman, A.; Knick-
erbocker, A.; Mueller, R.; Bryant, M.; Sherman, D. R.; Rus-
sell, D. G.; Goldberg, D. E. Embo. J. 1994, 13, 306. (b)
Gluzman, I. Y.; Francis, S. E.; Oksman, A.; Smith, C. E.;
Duffin, K. L.; Goldberg, D. E. J. Clin. Invest. 1994, 93, 1602.
27. We observed that ester formation was a notable side
reaction in these coupling reactions when indanolamine was a
part of the resin bound molecules.
28. Ward, P.; Armour, D. R.; Bays, D. E.; Evans, B.; Giblin,
G. M. P.; Heron, N.; Hubbard, T.; Liang, K.; Middlemiss, D.;
Mordaunt, J.; Naylor, A.; Pegg, N. A.; Vinader, M. V.; Wat-
son, S. P.; Bountra, C.; Evans, D. C. J. Med. Chem. 1995, 38,
4985.
29. Bold, G.; Fassler, A.; Capraro, H.G.; Cozens, R.; Klim-
kait, T.; Lazdins, J.; Mestan, J.; Poncioni, B.; Rosel, J.; Stover,
D.; Tintelnot-Blomley, M.; Acemoglu, F.; Ucci-Stoll, K.;
Wyss, D.; Lang, M. J. Med. Chem. 1998, 41, 3387.

A. Dahlgren et al. / Bioorg. Med. Chem. 11 (2003) 827–841
841
30. (a) Lipinski, C. A.; Lombardo, F.; Dominy, B. W.; Fee-
ney, P. J. Adv. Drug Deliv. Rev. 1997, 23, 3. (b) Lipinski, C. A.
In Tools for Oral Absorption. Part Two. Predicting Human
Absorption; BIOTEC, PDD Symposium, AAPS, Miami, 1995.
31. Manuscript in preparation.
32. Copeland, R. A., Ed. Enzymes: A Practical Introduction
to Structure, Mechanism, and Data Analysis, 2nd ed.; John
Wiley & Sons: New York, 2000.
33. Cheng, Y.; Prusoff, W. H. Biochem. Pharmacol. 1973, 22,
3099.