Aromatic β-amino acids as Asp-Phg mimics in LDV derived VLA-4 antagonists

Article abstract of DOI:10.1055/s-2002-34389

Aromatic β-amino acid esters 2a-h were prepared in racemic and enantiomerically pure form by the Radionow reaction or based on the method described by Davis and used as mimics of the Asp-Phg C-terminus in LDV derived VLA-4 antagonists. As a promising β-am

Full text of DOI:10.1055/s-2002-34389

PAPER
2023
Aromatic -Amino Acids as Asp Phg Mimics in LDV Derived VLA-4
Antagonists
Aromatic
-
Amino
o
A
cids as As
l
p–Phg
k
Mimics in
L
m
D
V
derived
V
L
A
-4
a
A
ntagonistr Wehner,*a Horst Blum,b Michael Kurz,a Hans Ulrich Stilza
a
Chemistry, Aventis Pharma Deutschland GmbH, 65926 Frankfurt am Main, Germany
Fax +490(69)331399; E-mail: volkmar.wehner@aventis.com
b
DG Thrombotic/Degenerative Joint Diseases, Aventis Pharma Deutschland GmbH, 65926 Frankfurt am Main, Germany
Received 28 June 2002
Dedicated to Professor Dieter Seebach on the occasion of his 65th birthday.
tides have been evaluated as antiproliferatives against hu-
man cancer cell lines4 and as mimics of the human peptide
hormone somatostatin.3 -Amino-acids have also been in-
corporated in pharmacologically active compounds.2
Abstract: Aromatic -amino acid esters 2a h were prepared in ra-
cemic and enantiomerically pure form by the Radionow reaction or
based on the method described by Davis and used as mimics of the
Asp–Phg C-terminus in LDV derived VLA-4 antagonists. As a
promising -amino acid ester, 11 was identified and used for the
synthesis of the highly potent VLA-4 antagonist S9059 with an IC50
of 1.6 nM in a cell attachment assay.
In pharmaceutical research, -amino acids have been used
as carboxy termini of blood platelet fibrinogen receptor
(GPIIb/IIIa) antagonists, which were expected to be a
promising new class of antithrombotic agents.5 These
compounds were derived from the RGDS tetrapeptide
recognition motif, which is used by fibrinogen to bind to
its receptor. In GPIIb/IIIa antagonists based on the hydan-
toin scaffold, the C-terminal aspartic acid–phenylglycine
(Asp–Phg) could be replaced by -amino acids leading to
orally bioavailable compounds.5 In the present paper, we
demonstrate that -amino acids could not only be used to
replace the C-terminus in RGDS derived peptidomimetics
Key words: amino acids, esters, asymmetric synthesis, chiral aux-
iliaries, VLA-4 antagonists
In the past years -amino acids have become of great in-
terest as building blocks for the synthesis of -peptides
due to their enhanced stability (compared to -amino ac-
ids) towards peptidases,1a–c their interesting structural
features1b,2 and biological functions.1b,2,3 Cyclo- -tripep-
Scheme 1
-Amino acids as C-termini of RGDS derived GPIIb/IIIa antagonists and LDV derived VLA-4 antagonists.
Synthesis 2002, No. 14, Print: 07 10 2002.
Art Id.1437-210X,E;2002,0,14,2023,2036,ftx,en;C03702SS.pdf.
© Georg Thieme Verlag Stuttgart · New York
ISSN 0039-7881

2024
V. Wehner et al.
PAPER
but are also valuable C-termini in LDV derived antago- 4, VCAM-1 ( = vascular cell adhesion molecule 1) as sub-
nists of the leukocyte receptor VLA-4 (very late activating strate.
antigen 4), which are of interest as antiinflammatory
In order to improve the oral bioavailability of the com-
agents.6 In this case, the Asp–Phg residue could also be re-
pounds, we evaluated the replacement of the Asp–Phg ter-
placed by -amino acids (see Scheme 1). Interestingly,
minus by aromatic -amino acids, which proved
VLA-4 antagonists with -amino acid C-termini have
successfull for RGDS derived GPIIb/IIIa antagonists.5
been reported by other research groups as well.7a–c
For this purpose, a set of racemic aromatic -amino acid
There are several methods for the synthesis of racemic ethylesters 2a–h was prepared by the Radionow reaction
and enantiomerically pure -amino acids described in the (for the preparation of the -amino acids) and subsequent
literature. The oldest and most commonly used method esterification using a saturated solution of HCl in ethanol
for the synthesis of aromatic -amino acids was published (Scheme 2, reaction conditions for the esterification and
by Radionow and coworkers. In the Radionow reaction, total yields see Table 1). The low yield for 2h (23%) may
an aromatic aldehyde and malonic acid are condensed in be due to the partial cleavage of the acetal group (OCH2O)
the presence of ammonium acetate, which serves as a base under the acidic conditions of ester formation.
and the source of the amino group.8a,b The -amino acid
Table 1 Aromatic -Amino Acid Ethyl Esters 2a–h Prepared Ac-
cording to Scheme 2
precipitates from the solution and can be isolated by a
simple filtration. Other methods used are the addition of
ammonia to acrylic acid derivatives or the Reformatsky
Compound R1
R2
Reaction
conditions
(esterification)
Total
yielda
reaction with imines.9a–d
Enantiomerically pure (ee >95%) -aryl- -amino acids
were prepared via penicillin acylase catalyzed hydrolysis
of the corresponding N-phenylacetyl derivatives10 which
were prepared by the Radionow reaction8a,b and subse-
quent acylation. The addition of lithium-(R)-( -methyl-
benzyl) benzylamide or lithium-(R)-N-benzyl-N- -
methyl-4-methoxybenzylamide as a homochiral ammonia
equivalent to (E)-t-butyl crotonate or substituted (E)-cin-
namic acid t-butyl esters and subsequent hydrogenolytic
or oxidative cleavage of the chiral auxilary allows the syn-
thesis of chiral -amino acids with high enantiomeric pu-
rity (>95% ee).11a,b
2a
2bb
2c
2d
2e
2f
F
H
7 h, reflux
7 h, reflux
5 h, reflux
7 h, reflux
7 h, reflux
7 h, reflux
7 h, reflux
22 h, r.t.
33 %
84 %
45 %
49 %
32 %
32 %
39 %
23 %c
Cl
H
t-Bu
H
i-Bu
H
OMe
H
OMe
OMe
2g
2h
3,4-OCH2CH2O
3,4-OCH2O
A very general approach for the preparation of Fmoc or
Boc protected enantiomerically pure -amino acids from
the corresponding -amino acids was described by See-
bach and coworkers. Using the Arndt–Eistert homologa-
tion sequence, enantiomerically pure -amino acids with
aliphatic, aromatic or functionalized side chains were pre-
pared.2,12a–c The enantioselective synthesis of -substitut-
ed -amino acids13and the preparation of geminally
disubstituted -amino acids has been described as well.14
a Compounds 2b,c,d,h were isolated as free base.
b 3-Amino-3-(4-chlorophenyl) propionic acid was purchased from
Maybridge.
c Work up procedure: The reaction mixture was filtered, the filtrate
concentrated in vacuo, the residue distributed between H2O and
EtOAc, the H2O phase washed with EtOAc and the combined organic
phases dried over Na2SO4. After filtration, the solvent was removed
in vacuo and the residue purified by chromatography over silica gel
(70–200 m) using CH2Cl2–MeOH, 9:1.
In the lead optimization process of VLA-4 antagonists, we
found that the Leu–Asp–Val (LDV) binding motif of one
of its natural ligands (fibronectin) could be replaced by a
Gly–Asp–Phg C-terminus. Incorporation of the Gly–
Asp–Phg C-terminus into a hydantoin scaffold led to the
potent VLA-4 antagonist S5466 with an IC50 of 0.5 M in
a cell attachment assay using the human VLA-4 express-
ing U937 cell line and one of the natural ligands of VLA-
The -amino acid ethyl esters prepared according
Scheme 2 were coupled to the racemic hydantoin deriva-
tive 8, which was synthesized as shown in Scheme 3.
4-Acetylbenzonitrile was reacted with potassium cyanide
and ammonium carbonate in a water–ethanol mixture to
give the hydantoin 4 as described.5 Treatment of 4 with
chloroacetic acid methylester in the presence of potassium
Scheme 2 Synthesis of racemic -amino acid ethyl esters 2a–h.
Synthesis 2002, No. 14, 2023–2036 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Aromatic -Amino Acids as Asp–Phg Mimics in LDV derived VLA-4 Antagonist
2025
iodide and sodium methoxide in methanol provided inter- Asp–Phg. Considering that one could expect an improve-
mediate 55 which was alkylated with 2-bromomethyl- ment of potency by a factor of about 2 for the active dia-
naphthalene in N-methylpyrrolidone using potassium car- stereomer, only a factor of about 9 in potency was lost in
bonate. The resulting hydantoin 6 was transformed to the 3f compared to S5466.
hydroxamidino derivative 7 by addition of hydroxy-
lamine. Hydrogenolytic cleavage followed by acidic hy-
drolysis of the methylester gave 8 which was coupled with
Table 2 VLA-4 Antagonists 3a–h Prepared According to Scheme 3
(Mixture of Two Diastereomers)
the -amino acid ethylesters 2a–h using DCC/HOBt.
Cleavage of the ethyl esters with lithium hydroxide in
methanol led to the VLA-4 antagonists 3a–h (Table 2) as
mixtures of 2 diastereomers (ratio about 1:1, Table 5 and
Table 6) as determined by 13C NMR (Table 6). The 2 iso-
mers were characterized by 1H NMR, 13C NMR and high
resolution mass spectrometry (HRMS) (Table 4, Table 5
and Table 6). 2D-NMR experiments (DQF-COSY, HM-
Com-
pound
R1
R2
Yielda
IC50[
]
U937(VLA-4)/
VCAM-1 cell at-
tachment assay
3a
3b
3c
F
H
46%
37%
12%
32%
46%
18%
30%
45%
31.6
46.0
88.7
75.2
17.7
9.4
Cl
H
t-Bu
H
QC, HMBC) allowed the assignment of all hydrogen and
1
carbon atoms. H–1H coupling constants for the 2 dia- 3d
i-Bu
H
stereomers could not be determined due to overlapping
signals. The yield over the last 2 steps (coupling of 2a–h
to 8, ester cleavage) varied between 12–46% depending
on the -amino acid ester used (Table 2)
3e
OMe
H
3f
OMe
OMe
3g
3,4-OCH2CH2O
3,4-OCH2O
22.1
19.6
0.5
Compounds 3a–h were tested in a cell attachment assay
using VLA-4 expressing human U937 cells which belong
to the leukocyte family and one of the ligands of VLA-4,
human VCAM-1 (vascular cell adhesion molecule 1) as
substrate, which was fixed on a 96-well microtiter plate
(results see Table 2).
3h
S5466
a Yield over 2 steps (coupling and ester cleavage, 8 to 3a–h).
In the next step of the lead optimization process, it was
planned to prepare 3-amino-3-(3,4-dimethoxy)phenyl-
propionic acid (or a corresponding ester) in enantiomeri-
cally pure form and to connect it to the optimized hydan-
toin derivative 17 (see Scheme 5). During this work we
The intention of this lead optimization step was to identify
the best replacement of the Asp–Phg C-terminus in
S5466. The 2 diastereomers were therefore not separated
but tested directly. 2f (leading to compound 3f, IC50 = 9.4
) was found to be the most suitable replacement for
Scheme 3 Synthesis of VLA-4 antagonists 3a–h.
Synthesis 2002, No. 14, 2023–2036 ISSN 0039-7881 © Thieme Stuttgart · New York

2026
V. Wehner et al.
PAPER
Scheme 4 Synthesis of (S)-3-Amino-3-(3,4-dimethoxy)-phenyl-propionic acid t-butylester 11.
found that in the case of commercially available (S)- and chloride 13 by catalytic reduction of the nitro group, addi-
(R)-3-amino-3-phenyl-propionic acid the (S)-enantiomer tion of phenylisocyanate and reaction of the biphenyl al-
led to more potent compounds. Therefore only (3S)-ami- cohol intermediate with SOCl2 in 85% yield over 3 steps.
no-3-(3,4-dimethoxy)phenyl-propionic acid was prepared The hydantoin building block 16 was prepared starting
by the method described by Davis and coworkers.11 It was from commercially available 1-amino-cyclohexane-car-
found that the procedure for the debenzylation/cleavage boxylic acid, which was transformed to the methylester 14
of the chiral auxillary (see Scheme 4 and experimental with SOCl2 in MeOH. The isocyanate of L-leucine t-buty-
section) could be performed under 105 Pa ( = 1atm) H2 lester (prepared as described by Nowick and coworkers15)
pressure using 10% Pd/C in methanol instead of the was coupled with 14 in DMF followed by acidic cycliza-
4
105 Pa using 30% Pd/C reported previously.11 The 1H tion of the adduct 15 to the hydantoin carboxylic acid 16.
NMR spectra (300 MHz, DMSO-d6) of the adduct 10 Compound 16 was deprotonated at the CO2H function and
showed only one set of signals indicating a diastereomeric at N3 by 2 equivalents of BuLi at –76 °C. The dianion was
purity of >95% de. Hydrogenolytic cleavage of the chiral reacted with the biphenyl urea chloride 13 at 0 °C and the
auxilary and debenzylation, which did not influence the mixture was adjusted to pH 1 by the addition of 1 N HCl.
enantiomeric excess of the -amino acid as shown by The hydantoin 17 was isolated after chromatographic pu-
Davis,11 gave 11 in 70% overall yield.
rification by preparative HPLC in 16% yield (not opti-
mized). For the synthesis of S9059, the -amino acid ester
11 was coupled to 17 using TOTU {O-[cyano(ethoxycar-
bonyl)methylene]amino}-N,N,N ,N -tetramethyluronium
tetrafluoroborate) and the t-butylester of the adduct was
cleaved with CF3CO2H. The enantiomeric purity of 17
was determined to be 97.6% (ee 95.2%) by HPLC on
chiral phase (see experimental section).
In parallel to the optimization of the C-terminus of the
VLA-4 antagonists, the substitution pattern at the hydan-
toin scaffold was optimized. We found that spiro cyclo-
hexyl hydantoin derivatives with a biphenyl urea
substituent at N3 led (after coupling of 11) to highly potent
VLA-4 antagonist S9059. In order to mimic the leucine
side chain of the LDV binding motif, an isobutyl group
was introduced next to the hydantoin as shown in In conclusion, we have shown that -amino acids could be
Scheme 5. The IC50 of S9059 in the cell attachment assay used as replacements of the pharmacokinetically less
(see above) was 1.6 nM, a 313 fold increase in potency favourable Asp–Phg C-terminus in LDV derived hydan-
compared to S5466. The biphenyl urea substituent in toin based antagonists of the leukocyte receptor VLA-4.
S9059 was mainly responsible for the marked increase in (3S)-Amino-3-(3,4-dimethoxy-phenyl)-propionic
acid
potency. Similar results have also been obtained by other was identified as a promising C-terminus. Parallel optimi-
groups working on LDV derived VLA-4 antagonists.6
zation of the substitution pattern at the hydantoin led to
the S9059, a VLA-4 antagonist with an excellent in vitro
potency (IC50 = 1.6 nM, cell attachment assay).
S9059 was prepared according to Scheme 5. 4-Nitrophe-
nyl-benzylalcohol was transformed to the biphenyl urea
Synthesis 2002, No. 14, 2023–2036 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Aromatic -Amino Acids as Asp–Phg Mimics in LDV derived VLA-4 Antagonist
2027
Scheme 5 Synthesis of VLA-4 antagonist S9059.
Table 3 Spectroscopic Data of -Amino Acid Ethylesters 2a–h
Com- 1H NMR (DMSO-d6), , J (Hz)
ESI-MS, m/z (%)a
pound
2a
1.08 (t, 3 H, J = 7.0 Hz, CH2CH3), 3.00 (A of ABX, J = 9.0, 16.5 Hz, 1 H, CHAH), 3.20 (B of ABX, J = 5.5, 212.0 (87) [M + H]+,
16.5 Hz, 1 H, CHHB), 3.97 (q, 2 H, J = 7.0 Hz, CH2CH3), 4.60 (X of ABX, 1 H, J = 5.5, 9.0 Hz, CH), 7.20– 195.0 (100), 152.9 (34)
+
7.32 (m, 2 H, ArH), 7.55–7.70 (m, 2 H, ArH), 8.75 (br s, 3 H, NH3 )
2b
2c
1.12 (t, 3 H, J = 7.0 Hz, CH2CH3), 2.01 (br s, 2 H, NH2), 2.50–2.60 (m, 2 H, CH2), 4.00 (q, 2 H, J = 7.0 Hz, 228.2 (100) [M + H]+,
CH2CH3), 4.20 (t, 1 H, CHNH2, J = 7.5 Hz), 7.28–7.43 (m, 4 H, ArH)
211.1 (15), 140.0 (56)
1.08 (t, 3 H, J = 7.0 Hz, CH2CH3), 1.28 (s, 9 H, t- Bu), 2.97 (A of ABX, J = 9.0, 15.5 Hz, 1 H, CHAH), 3.20 250.3 (16) [M + H]+,
(B of ABX, J = 5.5, 15.5 Hz, 1 H, CHHB), 4.00 (q, 2 H, J = 7.0 Hz, CH2CH3), 4.54 (X of ABX, 1 H, J = 5.5, 233.3 (32), 162.1 (100)
+
9.0 Hz, CH), 7.40–7.50 (m, 4 H, ArH), 8.68 (br s, 3 H, NH3 )
2d
2e
0.85 [d, 6 H, J = 6.0 Hz, C(CH3)3], 1.10 (t, 3 H, J = 6.5 Hz, CH2CH3),1.80 [sept, 1 H, J = 6.0 Hz, C(CH3)3], 250.3 (100) [M + H]+,
1.96 (br s, 2 H, NH2), 2.40 [d, 2 H, J = 6.0 Hz, C(CH3)3], 2.46–2.58 (m, 2 H, CH2), 4.00 (q, 2 H, J = 6.0 Hz, 233.2 (30), 162.1 (88)
CH2CH3), 4.16 (t, 1 H, J = 6.5 Hz, CH), 7.08 (d, J = 8.0 Hz, 2 H, ArH), 7.25 (d, J = 8.0 Hz, 2 H, ArH)
1.09 (t, 3 H, J = 7.0 Hz, CH2CH3), 2.94 (A of ABX, J = 9.0, 16.0 Hz, 1 H, CHAH), 3.16 (B of ABX, J = 5.5, 224.0 (12) [M + H]+,
16.0 Hz, 1 H, CHHB), 3.74 (s, 3 H, OCH3), 3.99 (q, 2 H, J = 7.0 Hz, CH2CH3), 4.52 (X of ABX, 1 H, J = 5.5, 207.0 (100), 165.0 (12)
+
9.0 Hz, CH), 6.97 (d, J = 8.5 Hz, 2 H, ArH), 7.45 (d, J = 8.5 Hz, 2 H, ArH), 8.56 (br s, 3 H, NH3 )
2f
1.05 (t, 3 H, J = 7.0 Hz, CH2CH3), 2.96 (A of ABX, J = 9.0, 16.0 Hz, 1 H, CHAH), 3.17 (B of ABX, J = 5.5, 254.2 (5) [M + H]+,
16.0 Hz, 1 H, CHHB), 3.74 (s, 3 H, OCH3), 3.77 (s, 3 H, OCH3), 4.01 (q, 2 H, J = 7.0 Hz, CH2CH3), 4.42–
4.58 (X of ABX, m,1 H, CH), 6.97–7.07 (m, 2 H, ArH), 7.28 (s, 1 H, ArH), 8.67 (br s, 3 H, NH3 )
253.2 (15), 237.2 (100),
166.0 (36)
+
2g
2hb
1.10 (t, 3 H, J = 6.5 Hz, CH2CH3), 2.90 (A of ABX, J = 9.0, 16.0 Hz, 1 H, CHAH), 3.12 (B of ABX, J = 5.5, 252.1 (16) [M + H]+,
16.0 Hz, 1 H, CHHB), 4.02 (q, 2 H, J = 6.5 Hz, CH2CH3), 4.23 (s, 4 H, OCH2CH2O), 4.48 (X of ABX, 1 H, 235.1 (100), 193.0 (3)
J = 5.5, 9.0 Hz, CH), 6.82–6.99 (m, 2 H, ArH), 7.09 (d, 1 H, J = 1.0 Hz, ArH), 8.55 (br s, 3 H, NH3 )
+
-
310.2 (30),. 238.1 (42)
[M + H]+, 221.1 (100),
150.0 (30)
a DCI-MS in case of compound 2f.
b Compound was characterized by MS and directly used for the synthesis of 3h.
Synthesis 2002, No. 14, 2023–2036 ISSN 0039-7881 © Thieme Stuttgart · New York

2028
V. Wehner et al.
PAPER
Table 4 HRMS Data of compounds 3a–h
Compound
3aa, ab
3ba, bb
3ca, cb
3da, db
Diastereomeric Ratio
m/z = calcd for [M + H]+
Calcd
(1.0/1.0)a
C33H31N5O5F
596.22963
596.23037
3ea, eb
(1.0/1.0)a
C33H31N5O5Cl
612.20022
612.20082
3fa, fb
(1.2/1.0)a
C37H40N5O5
634.30158
634.30240
3ga, gb
(1.0/1.0)a
C37H40N5O5
634.30158
634.30240
3ha, hb
Found
Compound
Diastereomeric Ratio
m/z = calcd for [M + H]+
Calcd
(1.0/1.0)
(1.1/1.0)
(1.1/1.0)
(1.0/1.0)
C34H34N5O6
608.24964
608.25036
C35H36N5O7
638.26001
638.26093
C35H34N5O7
636.24434
636.24527
C34H32N5O7
622.22885
622.22962
Found
a Determined by 13C NMR (125 MHz, DMSO-d6), main diastereomer = a, minor diastereomer = b (e.g. 3aa, 3ab).
Table 5 1H NMR Data of Compounds 3a–ha,b (500 MHz, DMSO-d6, )
Compound Number
3aa
3ab
3ba
3ca
3da
3ea
3fa
3ga
3ha
3bb
3cb
3db
3eb
3fb
3gb
3hb
Diastereomeric Ratioc (1.0/1.0)
(1.0/1.0)
(1.2/1.0)
(1.0/1.0)
(1.0/1.0)
(1.1/1.0)
(1.1/1.0)
(1.0/1.0)
H-2
2.52
2.52
5.19
5.19
8.87
8.87
4.20
4.20
1.70
1.69
4.11
4.09
4.86
4.84
2.51
2.51
5.17
5.17
8.90
8.90
4.20
4.20
1.69
1.69
4.11
4.08
4.85
4.84
2.50
2.50
5.16
5.16
8.88
8.87
4.17
4.17
1.70
1.69
4.11
4.08
4.85
4.84
2.52
2.52
5.19
5.19
8.82
8.82
4.20
4.20
1.70
1.69
4.11
4.08
4.85
4.84
2.51
2.51
5.14
5.14
8.78
8.78
4.17
4.17
1.70
1.69
4.11
4.08
4.86
4.84
2.51
2.51
5.16
5.16
8.79
8.79
4.20
4.20
1.70
1.70
4.09
4.12
4.83
4.86
2.49
2.49
5.08
5.08
8.77
8.76
4.16
4.16
1.70
1.69
4.11
4.08
4.86
4.84
2.48
2.48
5.11
5.11
8.80
8.79
4.18
4.18
1.70
1.69
4.12
4.08
4.86
4.84
3
4
6
8
10a
10b
Synthesis 2002, No. 14, 2023–2036 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Aromatic -Amino Acids as Asp–Phg Mimics in LDV derived VLA-4 Antagonist
2029
Table 5 1H NMR Data of Compounds 3a–ha,b (500 MHz, DMSO-d6, ) (continued)
Compound Number
3aa
3ab
3ba
3ca
3da
3ea
3fa
3ga
3ha
3hb
3bb
3cb
3db
3eb
3fb
3gb
Diastereomeric Ratioc (1.0/1.0)
(1.0/1.0)
(1.2/1.0)
(1.0/1.0)
(1.0/1.0)
(1.1/1.0)
(1.1/1.0)
(1.0/1.0)
7.63
H-12
7.63
7.62
7.64
7.64
7.63
7.64
7.63
7.63
7.76
7.76
7.46
7.46
7.46
7.46
7.84
7.84
7.80
7.80
7.34
7.34
7.70
7.67
7.79
7.78
7.36
7.36
7.12
7.12
-
7.62
7.76
7.76
7.46
7.46
7.46
7.46
7.85
7.85
7.80
7.80
7.34
7.34
7.69
7.66
7.79
7.76
7.35
7.35
7.35
7.35
-
7.65
7.78
7.78
7.47
7.47
7.46
7.46
7.85
7.85
7.80
7.80
7.34
7.34
7.68
7.71
7.79
7.80
7.24
7.24
7.30
7.30
-
7.64
7.78
7.78
7.46
7.46
7.45
7.45
7.84
7.84
7.80
7.80
7.34
7.34
7.70
7.67
7.79
7.78
7.22
7.24
7.05
7.08
-
7.63
7.77
7.77
7.46
7.46
7.46
7.46
7.84
7.84
7.80
7.80
7.34
7.34
7.70
7.67
7.80
7.78
7.25
7.24
6.87
6.84
-
7.64
7.76
7.76
7.46
7.46
7.46
7.46
7.84
7.84
7.80
7.80
7.34
7.34
7.71
7.67
7.79
7.78
6.95
6.93
-
7.63
7.77
7.77
7.46
7.46
7.45
7.45
7.84
7.84
7.80
7.80
7.34
7.34
7.70
7.67
7.80
7.78
6.80
6.83
-
7.63
7.76
7.76
7.46
7.46
7.46
7.46
7.84
7.84
7.80
7.80
7.34
7.34
7.70
7.67
7.79
7.78
6.90
6.89
-
14
15
16
17
19
20
22
23
27
28
30
-
-
-
6.77
6.77
-
6.83
6.80
-
6.77
-
6.83
-
31
-
-
-
-
-
6.77
-
6.80
-
t-Bu
1.84
1.84
Synthesis 2002, No. 14, 2023–2036 ISSN 0039-7881 © Thieme Stuttgart · New York

2030
V. Wehner et al.
PAPER
Table 5 1H NMR Data of Compounds 3a–ha,b (500 MHz, DMSO-d6, ) (continued)
Compound Number
3aa
3ab
3ba
3ca
3da
3ea
3fa
3ga
3ha
3bb
3cb
3db
3eb
3fb
3gb
3hb
Diastereomeric Ratioc (1.0/1.0)
(1.0/1.0)
(1.2/1.0)
(1.0/1.0)
(1.0/1.0)
(1.1/1.0)
(1.1/1.0)
(1.0/1.0)
CH2(i-Bu)
CH(i-Bu)
2 CH3(i-Bu)
OCH3
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
2.39
2.37
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
1.80
1.77
0.85
0.83
-
-
-
-
3.72
3.69
3.71
3.69
OCH3
-
-
-
3.69
3.74
OCH2CH2O
OCH2O
-
4.17, 4.20
4.17, 4.20
-
-
5.94, 5.97
5.94, 5.97
a Due to signal overlapping, coupling constants could not be determined.
b C(=NH)NH2 and CO2H protons appear between 8 12 ppm as a very broad signal.
c Determined by 13C NMR (125 MHz, DMSO-d6), main diastereomer = a, minor diastereomer = b (e.g. 3aa, 3ab).
Table 6 13C NMR Data of Compounds 3a–h (125 MHz, DMSO-d6, )
Compound Number
3aac
3abc
3ba
3ca
3da
3ea
3fa
3ga
3ha
3bb
3cb
3db
3eb
3fb
3gb
3hb
Diastereomeric Ratioa,b (1.0/1.0)
(1.0/1.0)
(1.2/1.0)
(1.0/1.0)
(1.0/1.0)
(1.1/1.0)
(1.1/1.0)
(1.0/1.0)
C-1
174.33
174.33
43.69
43.59
50.11
50.11
164.77
164.77
40.81
40.73
174.28
174.28
43.59
43.59
50.25
50.25
164.85
164.85
40.82
40.73
174.49
174.49
43.69
43.90
50.36
50.42
164.55
164.55
40.82
40.73
174.52
174.52
43.59
43.59
50.37
50.37
164.65
164.65
40.83
40.74
174.42
174.45
43.72
43.59
50.12
50.12
164.56
164.56
40.80
40.73
174.69
174.69
43.78
43.97
50.42
50.37
164.66
164.66
40.78
40.87
174.27
174.30
43.59
43.59
50.09
50.09
164.55
164.55
40.77
40.70
174.39
174.43
43.79
43.91
50.52
50.52
164.60
164.60
40.82
40.73
2
3
5
6
Synthesis 2002, No. 14, 2023–2036 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Aromatic -Amino Acids as Asp–Phg Mimics in LDV derived VLA-4 Antagonist
2031
Table 6 13C NMR Data of Compounds 3a–h (125 MHz, DMSO-d6, ) (continued)
Compound Number
3aac
3abc
3ba
3ca
3da
3ea
3fa
3ga
3ha
3hb
3bb
3cb
3db
3eb
3fb
3gb
Diastereomeric Ratioa,b (1.0/1.0)
(1.0/1.0)
(1.2/1.0)
(1.0/1.0)
(1.0/1.0)
(1.1/1.0)
(1.1/1.0)
(1.0/1.0)
155.49
155.46
67.00
C-7
155.47
155.43
67.01
155.46
155.42
67.01
155.49
155.45
66.98
155.49
155.46
66.98
155.49
155.46
66.98
155.46
155.51
66.99
155.49
155.46
66.99
8
66.98
66.99
66.98
66.98
66.98
66.99
66.97
66.98
8-Me
20.11
20.11
20.07
20.10
20.10
20.11
20.10
20.11
20.05
20.06
20.03
20.06
20.06
20.03
20.06
20.06
9
10
11
12
13
14
15
16
17
18
19
20
21
22
173.89
173.93
43.59
173.88
173.92
43.59
173.90
173.93
43.58
173.91
173.93
43.59
173.91
173.94
43.59
173.97
173.93
43.58
173.90
173.94
43.59
173.90
173.94
43.59
43.59
43.59
43.58
43.59
43.59
43.58
43.59
43.59
134.89
134.87
126.09
126.09
132.63
132.63
127.55
127.55
126.15
126.15
125.88
125.88
127.42
127.42
132.08
132.08
127.88
127.88
125.76
125.76
142.02
142.04
127.42
127.42
134.87
134.89
126.09
126.09
132.63
132.63
127.55
127.55
126.15
126.15
125.87
125.87
127.42
127.42
132.08
132.08
127.87
127.87
125.76
125.76
141.99
142.03
127.42
127.42
134.89
134.89
126.09
126.09
132.64
132.64
127.56
127.56
126.09
126.09
125.85
125.85
127.40
127.40
132.07
132.07
127.86
127.86
125.75
125.57
141.92
141.95
127.40
127.40
134.89
134.91
126.09
126.09
132.64
132.64
127.55
127.55
126.17
126.17
125.87
125.87
127.41
127.41
132.08
132.08
127.87
127.87
125.76
125.76
141.99
142.01
127.41
127.41
134.89
134.91
126.08
126.08
132.64
132.64
127.56
127.56
126.15
126.15
125.87
125.87
127.42
127.42
132.08
132.08
127.88
127.88
125.76
125.76
142.00
142.03
127.42
127.42
134.90
134.90
126.08
126.08
132.64
132.64
127.55
127.55
126.15
126.15
125.87
125.87
127.42
127.42
132.08
132.08
127.87
127.87
125.76
125.76
142.04
142.01
127.42
127.42
134.89
134.89
126.09
126.09
132.64
132.64
127.56
127.56
126.16
126.16
125.88
125.88
127.42
127.42
132.08
132.08
127.89
127.89
125.77
125.77
142.01
142.03
127.42
127.42
134.88
134.90
126.09
126.09
132.64
132.64
127.55
127.55
126.15
126.15
125.87
125.87
127.42
127.42
132.08
132.08
127.87
127.87
125.76
125.76
141.98
142.01
127.42
127.42
Synthesis 2002, No. 14, 2023–2036 ISSN 0039-7881 © Thieme Stuttgart · New York

2032
V. Wehner et al.
PAPER
Table 6 13C NMR Data of Compounds 3a–h (125 MHz, DMSO-d6, ) (continued)
Compound Number
3aac
3abc
3ba
3ca
3da
3ea
3fa
3ga
3ha
3bb
3cb
3db
3eb
3fb
3gb
3hb
Diastereomeric Ratioa,b (1.0/1.0)
(1.0/1.0)
(1.2/1.0)
(1.0/1.0)
(1.0/1.0)
(1.1/1.0)
(1.1/1.0)
(1.0/1.0)
C-23
128.06
128.06
129.18
129.21
165.34
165.38
139.46
139.35
128.03
128.03
129.21
129.21
165.37
165.39
142.30
142.41
127.99
127.99
129.33
129.37
165.37
165.43
140.26
140.43
126.09
126.09
124.81
124.84
148.77
128.03
128.03
129.24
129.24
165.35
165.38
140.38
140.52
126.17
126.17
128.64
128.66
139.28
128.03
128.03
129.24
129.26
165.36
165.39
135.11
135.24
127.56
127.56
113.49
113.52
158.00
128.03
128.03
129.26
129.24
165.41
165.38
135.90
135.76
110.49
110.49
148.47
148.43
147.55
128.05
128.05
129.20
129.23
165.34
165.38
136.25
136.37
115.07
115.08
142.89
142.91
142.11
128.03
128.03
129.25
129.25
165.36
165.40
137.23
137.36
106.98
106.98
145.84
145.85
147.03
24
25
26
27
128.34 (8 Hz) 128.33
128.34 (8 Hz) 128.33
114.80 (21 Hz) 128.05
114.78 (21 Hz) 128.05
28
29
160.99 (242
Hz)
131.17
131.17
-
161.01 (242
Hz)
148.77
-
139.28
-
158.02
-
147.53
-
142.13
147.06
30
-
-
-
-
-
-
-
-
-
-
116.57
116.59
119.26
119.26
-
107.79
107.82
119.55
119.57
-
31
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
C(CH3)3
34.05
34.05
31.12
31.12
-
C(CH3)3
-
-
-
-
-
-
-
-
CH2CH(CH3)2
CH2CH(CH3)2
CH2CH(CH3)2
29-OCH3
28-OCH3
OCH2CH2O
44.23
44.23
29.50
29.53
22.18
22.18
-
-
-
-
-
-
-
-
-
54.96
54.99
-
55.48
55.53
55.33
55.27
-
-
-
-
-
-
64.00
Synthesis 2002, No. 14, 2023–2036 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Aromatic -Amino Acids as Asp–Phg Mimics in LDV derived VLA-4 Antagonist
2033
Table 6 13C NMR Data of Compounds 3a–h (125 MHz, DMSO-d6, ) (continued)
Compound Number
3aac
3abc
3ba
3ca
3da
3ea
3fa
3ga
3ha
3hb
3bb
3cb
3db
3eb
3fb
3gb
Diastereomeric Ratioa,b (1.0/1.0)
(1.0/1.0)
(1.2/1.0)
(1.0/1.0)
(1.0/1.0)
(1.1/1.0)
(1.1/1.0)
(1.0/1.0)
64.03
63.90
63.93
-
OCH2CH2O
-
-
-
-
-
-
-
-
-
-
-
-
-
OCH2O
100.71
100.72
a Determined by 13C NMR (125 MHz, DMSO-d6).
b Main diastereomer = a, minor diastereomer = b (e.g. 3aa, 3ab).
c Coupling constants shown for C27-C29 in 3aa, 3ab refer to JC
.
F
was washed with H2O and dried over Na2SO4. After filtration, the
solvent was removed in vacuo. The -amino acid esters were char-
acterized by 1H NMR and MS (2a g) or MS (2h) (Table 3) and di-
rectly used for the synthesis of the VLA-4 antagonists 3a h.
Melting points were determined on a Büchi capillary melting point
apparatus and are uncorrected. 1H NMR spectra were recorded on a
Varian Gemini 200 (200 MHz) or a Bruker DRX 500 (500 MHz)
spectrometer. 13C spectra were recorded on a Bruker DRX 500 (125
MHz). The assignment of 1H and 13C chemical shifts in 3aa hb is
based on the analysis of 2D-NMR experiments (DQF-COSY,
HMQC and HMBC), values in ppm relative to TMS are given.
DQF-COSY experiments were performed with a spectral width of
10 ppm. Spectra were recorded with 512 increments in t1 and 2048
complex data points in t2, with 8 transients averaged for each t1 val-
ue. For the HMQC spectra, 512 increments (8 scans) with 2048
complex data points in t2 were collected using a sweep width of 10
ppm in the proton and 160 ppm in the carbon dimension. The
HMBC spectra were acquired with a sweep width of 10 ppm in the
proton and 200 ppm in the carbon dimension. A total of 48 tran-
sients were averaged for each of 512 increments in t1, and 2048
complex points in t2 were recorded. A delay of 70 msec was used
for the development of long range correlations. Low-mass spectra
were recorded with positive electrospray ionization (+ESI): VG
BIO-Q or dissociation chemical ionization (DCI): Kratos MS80 or
VG Trio 2000. High-resolution spectra were recorded on a VG ZAB
SEQ (+FAB). Optical rotations were determined on a Perkin-Elmer
241 polarimeter. The specific rotation has not been corrected. Pre-
parative HPLC separations were performed using a Hibar column
(LiChrosper 100 RP-18e, 5 m, cat. 1.50004,708, r.t. 250–25, Mer-
ck, Germany). As eluent H2O–CH3CN with 0.1% CF3CO2H was
used. Determination of the enantiomeric purity of S9059 was per-
formed by HPLC on a Chiral Pack AD column using heptane–
EtOH–i-PrOH, 5:1:1 + 0.1% diethylamine and 0.1% CF3CO2H as
eluent. The 3-amino-3-(4-chlorophenyl) propionic acid was pur-
chased from Maybridge.
[4-(4-Cyano-phenyl)-4-methyl-3-naphthalene-2-ylmethyl-2,5-
dioxo-imidazolidin-1-yl]-acetic Acid Methyl Ester (6)
To a soln of 5 (125 g, 435 mmol) and milled K2CO3 (66.1 g, 480
mmol) in N-methyl-2-pyrrolidone (1 L), 2-bromo-methylnaphtha-
lene (96.4 g, 435 mmol) was added and the reaction mixture stirred
at 60 °C for 8 h. After standing overnight, the mixture was filtered
over charcoal, H2O (2 L) was added and the product extracted with
CH2Cl2 (2 500 mL). The combined organic phases were washed
with sat. NaCl soln (2 250 mL) and dried over Na2SO4. After fil-
tration, the solvent was removed in vacuo and the remaining oil was
crystallized from i-PrOH. Compound 6 (98.5 g, 53%) was isolated
as a colorless solid, Fp 104 106 °C and directly transformed to 7.
{4-[4-(N-Hydroxycarbamimidoyl)-phenyl]-4-methyl-3-naph-
thalen-2-ylmethyl-2,5-dioxo- imidazolidin-1-yl}-acetic Acid
Methyl Ester (7)
Under a nitrogen atm, a soln of 6 (160 g, 374 mmol), hydroxy-
lamine-hydrochloride (52.4 g, 748 mmol) and Et3N (103.3 mL, 748
mmol) in EtOH (1600 mL) was heated unter reflux for 3 h. EtOH
(1200 mL) was partly removed in vacuo, ice H2O (800 mL) was
added and the soln extracted with EtOAc (3 300 mL). The com-
bined organic phases were washed with ice H2O (2 200 mL) and
dried over Na2SO4. After filtration the solvent was removed in vac-
uo and the residue stirred with MTBE (400 mL). After filtration, 7
(181.2 g, 105%) was isolated as a colorless solid (containing traces
of MTBE) which was used without further purification.
1H NMR (200 MHz, CDCl3): = 1.62 (s, 3 H, CH3), 3.80 (s, 3 H,
OCH3), 4.05 (A of AB, J = 15.0 Hz, 1 H, CHHA), 4.40 (s, 2 H,
CH2CO2CH3), 4.78 (br s, 2 H, NH2), 5.05 (B of AB, J = 15.0 Hz, 1
H, CHHB), 7.85 7.15 (m, 12 H, ArH, OH).
-Amino Acid Ethylesters 2a h;8 General Procedure
A mixture of the substituted benzaldehyde 1a,c h (0.10 mol), am-
monium acetate (15.4 g 0.20 mol) and malonic acid (10.4 g 0.10
mmol) in EtOH (25 mL) were heated under reflux for 6 h. After
cooling to r.t., the -amino acid was isolated by filtration, washed
with EtOH and dried over P2O5.
ESI-MS: m/z (%) = 461.3 (100) [M + H]+.
[4-(4-Carbamimidoyl-phenyl)-4-methyl-3-naphthalen-2-ylme-
thyl-2,5-dioxo-imidazolidin-1-yl]-acetic Acid (8)
For the preparation of the ethyl ester the -amino acid was added to
a sat. soln of HCl in EtOH at 0 °C, stirred at r.t. for 1 h and then un-
der reflux (see Table 1). The solvent was removed in vacuo and the
residue washed with Et2O, filtered and dried in vacuo.
Under a nitrogen atmosphere 5% Pd/C (24 g, 58.2% H2O, Engel-
hard) was added to a soln of 7 (220 g, 478 mmol) in HOAc (1 L) and
the mixture hydrogenated under an 105 Pa H2 atm at 50 °C for 10 h.
The catalyst was filtered, the solvent removed in vacuo and the res-
idue stirred with MTBE (400 mL). After filtration, [4-(4-carbamim-
idoyl-phenyl)-4-methyl-3-naphthalen-2-ylmethyl-2,5-dioxo-imi-
dazolidin-1-yl]- acetic acid methylester (185 g, 77%) was isolated
In the cases were the -amino acid ethylesters were isolated as the
free base (see Table 1), the solvent was removed and the residue
distributed between H2O and EtOAc. The two phases were neutral-
ized with NaHCO3 under stirring and separated. The organic phase
Synthesis 2002, No. 14, 2023–2036 ISSN 0039-7881 © Thieme Stuttgart · New York

2034
V. Wehner et al.
PAPER
as a colorless solid, characterized by MS and directly transformed
to 8.
ESI-MS: m/z (%) = 445.3 [M + H]+.
mixture stirred for 1 h at this temperature. A soln of 9 (20 g, 75.7
mmol) in anhyd THF (100 mL) was added dropwise over 1 h at
–70 °C and the mixture was stirred for 2 h at –70 °C. The reaction
mixture was quenched with citric acid (150 mL, 5% in H2O),
warmed up to r.t. and stirred at r.t. for 1 h. EtOAc (500 mL) was
added, the phases separated and the H2O phase was extracted with
EtOAc (200 mL). The combined organic phases were washed with
sat. NaHCO3 soln (300 mL) and dried over Na2SO4. After filtration,
the solvent was removed in vacuo and the residue purified by chro-
matography over silicagel (35–70 m) using heptane EtOAc as
eluent to yield 10 (34.7 g, 97%) as an yellow oil.
1H NMR (300 MHz, DMSO-d6): = 1.09 (d, J = 6.0 Hz, 3 H, Me),
1.22 (s, 6 H,t-Bu), 2.53 (A of ABX, J = 6.8, 10.5 Hz, 1 H, HA), 2.66
(B of ABX, J = 3.8, 10.5 Hz, 1 H, HB), 3.60, 3.66 (AB system,
J = 11.3, 2 H, NCH2), 3.72 (s, 3 H, OCH3), 3.78 (s, 3 H, OCH3), 4.02
(q, J = 6.0 Hz, 1 H, CH), 4.12 (X of ABX, J = 3.8, 6.8 Hz, 1 H, HX),
6.83–6.95 (m, 3 H, ArH), 7.12–7.48 (m, 10 H, ArH) (only 1 dia-
stereomer detectable).
The solid (140 g, 278 mmol) was heated in concd HCl (2 L) under
reflux for 8 h. The mixture was concentrated in vacuo and the resi-
due distributed between H2O (1 L) and EtOAc (1 L). The pH was
adjusted to 4–5 by adding concd NaOH. After 30–45 min the car-
boxylic acid 9 crystallized. The compound was isolated by filtration
and washed with H2O (100 mL) and EtOAc (100 mL). The residue
was dissolved in concd HCl (1 L), filtered over charcoal, the soln
concentrated in vacuo and the residue distributed between H2O
EtOAc, 1:1 (800 mL). The pH was adjusted to 4 and 8 precipitated
as a colorless crystalline solid (70.5 g, 59%, Fp 258–260 °C) which
was isolated by filtration.
1H NMR (200 MHz, DMSO-d6): = 1.68 (s, 3 H, CH3), 4.05–3.85
(AB, 2 H, CH2CO2CH3), 4.06 (A of AB, J = 16.0 Hz, 1 H, CHHA),
4.85 (B of AB, J = 16.0 Hz, 1 H, CHHB), 7.30–7.94 (m, 11 H, ArH),
+
9.03 (br s, 2 H, NH2), 11.75 (br s, 2 H, NH2 ).
DCI-MS: m/z (%) = 276.4 (10) [M + H]+, 360.3 (22), 265.3 (100),
212.3 (53), 105.1 (52).
MS (FAB): m/z (%) = 431.2 (100) [M + H]+, 386.2 (13).
VLA-4 Antagonists 3a–h; General Procedure
(3S)-Amino-3-(3,4-dimethoxy-phenyl)-propionic Acid t-Butyl
Ester (11)
A soln of 10 (34 g, 71.75 mmol) in MeOH (300 mL) was hydroge-
nated over 10% Pd/C (12 g) for 3 h. The catalyst was filtered and
the soln concentrated in vacuo to yield 11 (18.5 g, 92%) as a yellow
oil.
To a soln of the hydantoin derivative 8 (861 mg, 2.00 mmol), the
-amino acid 2a h (2.00 mmol), HOBt (270 mg, 2.00 mmol) in
DMF (20 mL), N-ethyl morpholine (0.26 mL 2.00 mmol) and DCC
(440 mg, 2.14 mmol) were added. The mixture was stirred 1 h at
0 °C and 4 h at r.t. After standing overnight, dicyclohexylurea was
filtered off and the filtrate concentrated in vacuo. The residue was
dissolved in pentanol, washed with sat. NaHCO3 soln and sat. NaCl
soln. The organic phase was dried over Na2SO4. After filtration the
solvent was removed in vacuo and the residue triturated with Et2O.
After filtration the crude product was dissolved in MeOH (30 mL),
1 N LiOH soln (10 mL) was added at 0 °C and the mixture stirred
for 4 h at r.t. After standing overnight at 4 °C, CF3CO2H was added
to neutralize the reaction mixture. The mixture was filtered, the fil-
trate concentrated in vacuo, the residue triturated with H2O, isolated
by filtration and purified over sephadex LH20 using 10% HOAc in
H2O. The fractions containing the product were combined, the soln
concentrated in vacuo and the products 3a h isolated after lyo-
philization as colorless amorphous solids (yields see Table 2, spec-
troscopic data see Table 4, Table 5 and Table 6).
[ ]D27 +8.0 (c 1, MeOH).
1H NMR (300 MHz, DMSO-d6): = 1.34 (s, 9 H, t-Bu), 1.95 (s, 2
H, NH2), 2.43 (A of ABX, J = 6.0, 11.3 Hz, 1 H, HA), 2.50 (B of
ABX, J = 6.8, 11.3 Hz, 1 H, HB), 3.72 (s, 3 H, OCH3), 3.75 (s, 3 H,
OCH3), 4.10 (X of ABX, J = 6.0, 6.8 Hz, 1 H, HX), 6.84 (s, 2 H,
ArH), 6.98 (s, 1 H, ArH).
DCI-MS: m/z (%) = 282.4 (35) [M + H]+, 265.3 (100), 224.3 (12),
180.3 (18), 166.2 (93).
1-(4-Hydroxymethyl-phenyl)-3-phenyl-urea (12)
4-Nitrobenzyl alcohol (30.6 g, 200 mmol) was hydrogenated over
10% Pd/C (1 g, 50% H2O) in MTBE (500 mL). After the absorption
of hydrogen was complete, the catalyst was filtered. Phenyl isocy-
anate (24 g, 200 mmol) was added to the filtrate at 15 °C with stir-
ring in the course of 30 min. The precipitated solid was filtered with
suction and washed with MTBE. Yield: (43 g, 89%).
1H NMR (200 MHz, DMSO-d6): = 4.43 (s, 2 H, CH2), 5.05 (br s,
1 H, OH), 6.95 (t, J = 7.5 Hz, 1 H, ArH), 7.16–7.50 (m, 8 H, ArH),
8.60 (s, 1 H, NH), 8.63 (s, 1 H, NH)
3-(3,4-Dimethoxy-phenyl)-acrylic Acid t-Butyl Ester (9)
To a suspension of 3-(3,4-dimethoxy-phenyl)-acrylic acid (40 g,
192 mmol) in anhyd CH2Cl2 (400 mL), oxalic acid chloride (24.7
mL, 288 mmol) was added tropwise and the mixture stirred for 3 h
at r.t. and a clear soln was formed. t-BuOH (300 mL) was added and
the reaction mixture, after standing overnight at r.t., concentrated in
vacuo. The residue was dissolved in EtOAc (450 mL) and the or-
ganic phase washed with sat. NaHCO3 soln (3 250 mL). The phas-
es were separated and the organic phase dried over Na2SO4. After
filtration, the solvent was removed in vacuo and the residue purified
by chromatography over silica gel (35–70 m) using heptane–
EtOAc (4:1) as solvent. The product fractions were combined to
yield 9 (39.44 g, 78%) as an oil.
1H NMR (300 MHz, DMSO-d6): = 1.50 (s, 9 H, t-Bu), 3.79 (s, 3
H, OCH3),3.81 (s, 3 H,OCH3), 6.44 (d, J = 15.0 Hz, 1 H, CH), 6.97
(d, J = 8.3 Hz, 1 H, ArH), 7.20 (dd, J = 0.8 Hz, J = 8.3 Hz, 1 H,
ArH), 7.32 (d, J = 0.8 Hz, 1 H, ArH), 7.48 (d, J = 15.0 Hz, 1 H,
CH).
DCI-MS: m/z (%) = 242.9 (60) [M + H]+, 226.8 (32), 123.0 (52),
119.0 (100), 106.1 (38), 94.1 (53), 93.0 (95), 91.0 (40), 61.1 (41).
1-(4-Chloromethyl-phenyl)-3-phenyl-urea (13)
Thionyl chloride (42 g, 354 mmol) was added dropwise at 30 °C to
a suspension of 12 (42.8 g, 177 mmol) in CH2Cl2 (500 mL). The
mixture was subsequently stirred at 40 °C for 1 h. After completion
of the evolution of gas, the mixture was allowed to cool to r.t. The
precipitated product was filtered with suction and washed with
CH2Cl2. Yield: (44.26 g, 96%) which was used in the next step after
characterization by NMR spectroscopy.
1H NMR (200 MHz, DMSO-d6): = 4.72 (s, 2 H, CH2), 6.97 (t,
J = 7.5 Hz,1 H, ArH), 7.23–7.50 (m, 8 H, ArH), 8.70 (s, 1 H, NH),
8.78 (s, 1 H, NH).
(3S)-[(R)-Benzyl-1-phenyl-ethyl)-amino]-3-(3,4-dimethoxy-
phenyl)-propionic Acid t-Butyl Ester (10)
To a soln of (R)-Benzyl-1-phenyl-ethylamine (17.6 g, 83.2 mmol)
in anhyd THF (300 mL), BuLi (32.6 mL, 2.5 M in hexane, 81.4
mmol) were added over 1 h at –70 °C under an argon atm and the
1-Amino-cyclohexanecarboxylic Acid Methyl Ester (14)
Thionyl chloride (51 mL) was added in portions at –5 °C to 1-ami-
nocyclohexane-1-carboxylic acid (50 g, 350 mmol) in MeOH (1.25
Synthesis 2002, No. 14, 2023–2036 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Aromatic -Amino Acids as Asp–Phg Mimics in LDV derived VLA-4 Antagonist
2035
L). The reaction mixture was subsequently stirred at r.t. for 5 h and
allowed to stand overnight at r.t. MeOH was removed in vacuo, the
residue was mixed with H2O, and the aq soln was adjusted to pH 9
using sat. Na2CO3 soln and extracted with CH2Cl2 (2 350 mL).
The phases were separated, the organic phase was dried over
Na2SO4 and, after filtration, the solvent was removed in vacuo.
Yield: (36.35 g, 66%).
1H NMR (200 MHz, DMSO-d6): = 1.20–1.85 (m, 12 H, cycl H,
NH2), 3.60 (s, 3 H, OCH3)
DCI-MS: m/z (%) = 158.3 (100) [M + H]+, 98.2 (56).
(3S)-(3,4-Dimethoxy-phenyl)-3-[(2S)-{2,4-dioxo-1-[4-(3-phenyl-
ureido)-benzyl]-1,3-diaza-spiro[4.5]dec-3-yl}-4-methyl-pen-
tanoylamino]-propionic Acid S9059
TOTU (972 mg, 2.96 mmol) and DIPEA (478 L, 2.81 mmol) were
added successively with ice-cooling to a soln of 17 (1.50 g, 2.96
mmol) and 11 (833 mg, 2.96 mmol) in anhyd DMF (20 mL). After
1 h at r.t., the solvent was removed in vacuo, the residue was dis-
solved in EtOAc (100 mL) and the EtOAc soln was successively
with an aq KHSO4/K2SO4 soln (50 mL), a sat. NaHCO3 soln (50
mL) and a sat. NaCl soln (50 mL). After separation of the phases
and drying of the organic phase over Na2SO4 and filtering, the sol-
vent was removed in vacuo and the residue was chromatographed
on silica gel (35–70 m) using EtOAc–heptane, (1:1). After concen-
trating the product fractions, the residue was dissolved in CF3CO2H
(20 mL) and stirred for 30 min. at r.t. The mixture was concentrated
in vacuo, the residue was dissolved in CH3CN–H2O (200 mL) and
freeze dried. Yield (1.17 g, 55%); ee 95.2% (HPLC).
1-[3-(1-t-Butoxycarbonyl-3-methyl-butyl)-ureido]-cyclohex-
anecarboxylic Acid Methyl Ester (15)
A soln of 14 (28 g,179 mmol) was added to a soln of L-leucine t-
butyl ester isocyanate (38 g,179 mmol)15 in anhyd DMF (300 mL).
After stirring at r.t. for 2 h, the reaction mixture was allowed to
stand overnight. The solvent was removed in vacuo, the residue was
treated with heptane (400 mL) and the mixture was stirred at r.t. for
2 h. The precipitate was filtered with suction and washed with hep-
tane. Yield: (45.94 g, 69%).
1H NMR (200 MHz, DMSO-d6): = 0.87 (d, J = 7.5 Hz, 3 H, CH3),
0.93 (d, J = 7.5 Hz, 3 H, CH3),1.40 (s, 9 H, t-Bu), 1.13–1.99 (m, 13
H, cycl H, CH2, CH), 3.53 (s, 3 H, OCH3), 3.98 (dt, J = 6.5, 9.0 Hz,
1 H, NCH), 6.11 (d, J = 9.0 Hz, 1 H, NH), 6.31 (s,1 H, NH).
HRMS: m/z calcd for C39H47N5O8 [M + H]+, 714.3499; found,
714.3497.
1H NMR (500 MHz, DMSO-d6): = 0.90 (d, J = 6.6 Hz, 6 H, 2
CH3), 1.12–1.84 (m, 10 H,cycl H), 1.42 (m, 1 H, CH), 2.26, 1.80 (m,
2 H, CH2), 2.70 (m, 2 H, CH2CO2H), 3.72 (s, 3 H, OCH3), 3.74 (s,
3 H, OCH3), 4.41, 4.50 (d, J = 16.4 Hz, 2 H, NCH2), 4.54 (dd,
J = 4.6, 12.1 Hz, 1 H, NCHCO), 5.17 (m, 1 H, NCH), 6.81 (dd,
J = 2.0, 8.4 Hz, 1 H, ArH), 6.89 (d, J = 8.4 Hz, 1 H, ArH), 6.92 (d,
J = 2.0 Hz, 1 H, ArH), 6.96 (m, 1 H, ArH), 7.20 (d, J = 8.6 Hz, 2 H,
ArH), 7.27 (m, 2 H, ArH), 7.39 (d, J = 8.6 Hz, 2 H, ArH), 7.44 (m,
2 H, ArH), 8.30 (d, J = 8.0 Hz, 1 H, NH), 8.64 (s, 1 H, NH), 8.66 (s,
1 H, NH), 12.3 (br s, 1 H, CO2H).
DCI-MS: m/z (%) = 371.4 (100) [M + H]+, 315.3 (31).
(2S)-(2,4-Dioxo-1,3-diaza-spiro[4.5]dec-3-yl)-4-methyl-pen-
tanoic Acid (16)
15 (11.4 g, 30.8 mmol) was heated at 60 °C for 8 h in 6 N HCl (200
mL), the mixture was allowed to stand at r.t. overnight and then ex-
tracted with Et2O (400 mL). The combined extracts were concen-
trated in vacuo, the residue was dissolved in CH3CN–H2O (500
mL), and freeze-dried. Yield: (8.28 g, 95%).
13C NMR (125 MHz, DMSO-d6): = 20.62 (CH3), 23.20 (CH3),
20.86, 20.92, 23.74, 31.42, 31.54 (5 cycl C), 25.10 (CH), 35.99
(CH2), 40.60 (CH2CO2H), 40.86 (NCH2), 49.36 (NCH), 51.97
(NCHCO), 55.34 (OMe), 55.50 (OMe), 62.15 (cycl C), 110,41,
111.61, 118.13, 118.13, 118.13, 121,76, 127.44, 128.73 (12 ArC),
132.00 (ArCCH2), 134.73 (ArCHNH), 138.52 (HNCAr), 139.66
(ArCNH), 147.77 (ArC–OCH3), 148.52 (ArC–OCH3), 152.49 (NH-
CONH), 155.20 (NCON), 167.55 (CONH), 171.81 (CO2H), 175.57
(NCO).
[ ]D23 –47.8 (c 1, DMF).
1H NMR (200 MHz, DMSO-d6): = 0.86 (d, J = 6,5 Hz, 3 H, CH3),
0.92 (d, J = 6.5 Hz, 3 H, CH3), 1.16–1.84 (m, 12 H, cycl H, CH2),
2.00–2.19 (m, 1 H, CH), 4.48 (dd, J = 4.5 Hz, 11.0 Hz, 1 H, NCH),
8.67 (s,1 H, NH), 12.93 (br s, 1 H, COOH).
DCI-MS: m/z (%) = 283.5 (52) [M + H]+, 169.2 (100), 117.2 (42).
Acknowledgments
We thank Dr. Mark Broenstrup for performing HRMS analyses and
Martina Vogel, Dieter Hill, Peter Pokorny, Dirk Timme, Norbert
Laub, Ulrich Nickel and Juergen Michalowsky for skillful technical
assistance.
(2S)-{2,4-Dioxo-1-[4-(3-phenyl-ureido)-benzyl]-1,3-diaza-
spiro[4.5]dec-3-yl}-4-methyl- pentanoic Acid 17
A soln of BuLi (21 mL, 2.5 M in hexane) was added at –76 °C under
argon to a soln of 16 (7.4 g, 26.24 mmol) in anhyd THF (150 mL).
After stirring at –76 °C for 30 min, the reaction mixture was al-
lowed to warm to 0 °C and 13 (6.82 g, 26.24 mmol) was added in
portions. After stirring at 0 °C for 30 min, the mixture was adjusted
to pH 1 by addition of 1 N HCl, diluted with H2O (100 mL) and ex-
tracted with EtOAc (100 mL). After separating the phases, the or-
ganic phase was dried over Na2SO4 and, after filtration, the solvent
was removed in vacuo. The residue thus obtained was purified by
preparative HPLC. Yield: (2.18 g, 16%).
References
(1) (a) Hintermann, T.; Seebach, D. Chimia 1997, 50, 244.
(b) Seebach, D.; Albert, M.; Arvidsson, P. I.; Rueping, M.;
Schreiber, J. V. Chimia 2001, 55, 345. (c) Frackenpohl, J.;
Arvidsson, P. I.; Schreiber, J. V.; Seebach, D.
ChemBioChem 2001, 2, 445.
(2) Gademann, K.; Ernst, M.; Hoyer, D.; Seebach, D. Angew.
Chem.´Int. Ed. 1999, 111, 1223; Angew. Chem. 1999, 111,
1302.
(3) Gademann, K.; Kimmerlin, T.; Hoyer, D.; Seebach, D. J.
Med. Chem. 2001, 44, 2460.
(4) Gademann, K.; Seebach, D. Helv. Chim. Acta 2001, 84,
2924.
[ ]D23 –30.8 (c 1, DMF).
1H NMR (200 MHz, DMSO-d6): = 0.89 (d, J = 6.0 Hz, 3 H, CH3),
0.91 (d, J = 6.0 Hz, 3 H, CH3), 1.03–1.97 (m, 12 H, cycl H, CH2),
2.03–2.22 (m, 1 H, CH), 4.47 (s, 2 H, NCH2), 4.58 (dd, J = 4.0, 10.5
Hz, 1 H, NCH), 6.95 (t, 1 H, J = 7.0 Hz, ArH), 7.17–7.50 (m, 8 H,
Ar-H), 8.65 (s, 2 H, 2 NH), 13.00 (br s, 1 H, COOH).
ESI-MS: m/z (%) = 507.3 (100) [M + H]+, 285.9 (14), 114.4 (23),
93.9 (28).
(5) Stilz, H. U.; Guba, W.; Jablonka, B.; Just, M.; Klingler, O.;
König, W.; Wehner, V.; Zoller, G. J. Med. Chem. 2001, 44,
1158; and literature cited therein.
(6) Tilley, J. W.; Sidduri, A. Drugs Future 2001, 26, 985.
Synthesis 2002, No. 14, 2023–2036 ISSN 0039-7881 © Thieme Stuttgart · New York

2036
V. Wehner et al.
PAPER
(10) Soloshonok, V. A.; Fokina, N. A.; Rybakova, A. V.;
Shishkina, I. P.; Golushko, S. V.; Sorochinsky, A. E.;
Kukhar, V. P. Tetrahedron: Asymmetry 1995, 6, 1601.
(11) (a) Davis, S. G.; Ichihara, O. Tetrahedron: Asymmetry 1991,
2, 183. (b) Davis, S. G.; Garrido, N. M.; Ichihara, O.;
Walters, I. A. J. Chem. Soc., Chem. Commun. 1993, 1153.
(12) (a) Guichard, G.; Abele, S.; Seebach, D. Helv. Chim. Acta
1998, 81, 187. (b) Podlech, J.; Seebach, D. Liebigs Ann.
Chem. 1995, 1217. (c) Matthews, J. L.; Braun, C.;
(7) (a) Holland, G. W.; Kassir, J. M.; Scott, I. L. TBC3486:
Novel highly potent and selective VLA-4 antagonist; 219th
ACS Natl Meeting, ACS: Washington DC, 2000.
(b) Kassir, J. M.; Scott, I. L.; Biediger, R. J. Novel NN
disubstituted amides that are highly potent VLA-4
antagonist; 219th ACS Natl Meeting, ACS: Washington
DC, 2000. (c) Scott, I. L.; Raju, B. G.; Ren, K. Novel urea
derivatives that are highly potent VLA-4 antagonist; 219th
ACS Natl Meeting, ACS: Washington DC, 2000.
(8) (a) Radionow, W. M.; Postovskaja, E. A. J. Am. Chem. Soc.
1929, 51, 847. (b) Radionow, W. M. J. Am. Chem. Soc.
1929, 51, 847.
Guibourdenche, C.; Overhand, M.; Seebach, D. In
Enantioselective Synthesis of -Amino Acids; Wiley-VCH:
New York, 1997, 105.
(9) (a) Secor, H. V.; Edwards, W. B. J. Org. Chem. 1979, 44,
3136. (b) Furukawa, M.; Okawara, T.; Noguchi, Y.;
Terawaki, Y. Chem. Pharm. Bull. 1978, 26, 260. (c) Bovy,
R. P.; Rico, J. G. Tetrahedron Lett. 1993, 34, 8015.
(d) Robinson, A. J.; Wyatt, P. B. Tetrahedron 1993, 49,
11329.
(13) Juaristi, E. M.; Seebach, D. In Enantioselective Synthesis of
-Amino Acids; Wiley-VCH: New York, 1997, 261.
(14) Abele, S.; Seebach, D. Eur. J. Org. Chem. 2000, 1.
(15) Nowick, J. S.; Holmes, D. L.; Noronha, G.; Smith, E. M.;
Nguyen, T. M.; Huang, S.-L. J. Org. Chem. 1996, 61, 3929.
Synthesis 2002, No. 14, 2023–2036 ISSN 0039-7881 © Thieme Stuttgart · New York