Synthesis and biological evaluation of integrin antagonists containing trans- and cis-2,5-disubstituted THF rings

Article abstract of DOI:10.1002/(SICI)1521-3765(20000218)6:4<666::AID-CHEM666>3.0.CO;2-Z

The synthesis of a series of RGD mimetics is described. All compounds consist of a central 2,5-disubstituted tetrahydrofuran core, a variable linker to a guanidino group, and a β-amino alanine unit to mimic the carboxylic acid. Three types of linkers were

Full text of DOI:10.1002/(SICI)1521-3765(20000218)6:4<666::AID-CHEM666>3.0.CO;2-Z

FULL PAPER
Synthesis and Biological Evaluation of Integrin Antagonists Containing
trans- and cis-2,5-Disubstituted THF Rings
Frank Osterkamp,[a] Burkhard Ziemer,[a] Ulrich Koert,*[a] Matthias Wiesner,[b]
Peter Raddatz,[b] and Simon L. Goodman[b]
Abstract: The synthesis of a series of
RGD mimetics is described. All com-
pounds consist of a central 2,5-disubsti-
tuted tetrahydrofuran core, a variable
linker to a guanidino group, and a b-
amino alanine unit to mimic the carbox-
ylic acid. Three types of linkers were
investigated: a simple four-atom meth-
ylene chain (type A, compounds 14, 15,
16, and 17), a four-atom methylene
chain with an additional chiral center,
and a nitrogen substituent (type B,
compounds 38, 39, and 40), and an
amide linker of different length with an
additional chiral center (type C, com-
pounds 59, 60, 61, and 62). A variety of
compounds were tested as potential
integrin antagonists in a receptor bind-
ing assay (aIIbb3, avb3, and avb5). The
relative and absolute configuration of
the chiral centers at the THF ring had a
pronounced effect on the binding activ-
ity and selectivity. Compound 14 proved
to be a selective inhibitor of aIIbb3
(IC50 ˆ 20nm), whereas compound 40
exhibited high activity for binding of
aIIbb3 (IC50 ˆ 67nm) and avb3 (IC50 ˆ
52nm).
Keywords: b-turn ´ integrin antago-
nists ´ peptidomimetics ´ synthesis
design
interactions with the aIIbb3- and the avb3-type integrins
(Figure 1). Intensive efforts have been made to find selective
aIIbb3- and the avb3-type antagonists by structural variation of
the RGD motif.[4, 5]
Introduction
Cell-cell and cell-matrix adhesion processes are controlled by
four classes of cell-surface proteins: cadherins, selectins,
receptors of the immunoglobulin family, and integrins.[1] The
integrins are cell-surface receptors consisting of heterodimer-
ic glycoproteins (GPs) with different numbers and types of a
and b subunits. They bind to extracellular matrix adhesive
proteins such as fibrinogen, fibronectin, vitronectin, and
VCAM-1 (vascular cell adhesion molecule-1). Within the
integrin receptor family, the avb3-integrin and the aIIbb3-
integrin receptor (also called GPIIb/IIIa) have gained partic-
ular importance in medicinal chemistry. The avb3 integrin
binds the natural ligands fibrinogen and vitronectin and is
involved in many pathological processes such as angiogenesis,
platelet aggregation, and tumor growth.[2] avb3-Antagonists
are therefore promising drug candidates for different diseases
such as cancer and osteoporosis. The aIIbb3 integrin is involved
in blood platelet aggregation and its blocking has been
investigated in the context of thrombosis therapy.[3] The RGD
motif is common for the ligands found in the adhesive
O
O
N
H
O
H
H2N
N
OH
H
N
NH
N
O
H
G
D
R
Figure 1. The RGD motif which is essential for most binding sites of
naturally occurring integrin ligands.
Cyclic RGD peptides such as 2[6] or 3[7] were developed by
different groups (see Figure 2).[8, 9, 10] Their advantage is the
conformational constraint of the cyclic system, which allows a
Ph
O
N
N
H
O
O
H
N
O
O
H
N
O
N
H
O
O
O
N
H
O
H
H
[a] Prof. Dr. U. Koert, Dr. F. Osterkamp, Dr. B. Ziemer
Institut für Chemie der Humboldt-Universität zu Berlin
Hessische Strasse 1 ± 2, 10115 Berlin (Germany)
Fax : (‡ 49)30-2093-7266
H2N
N
H2N
N
OH
O
H
OH
H
O
N
N
NH
NH
N
N
H
H
E-mail: koert@lyapunov.chemie.hu-berlin.de
3: cyclo(-RGD-Mamb-P-)
2: cyclo(-RGDfV-)
Kessler and Merck KGaA[6]
[b] Dr. M. Wiesner, Dr. P. Raddatz, Dr. S. L. Goodman
Merck KGaA Preclinical Research
Dupont-Merck[7]
Frankfurter Strasse 250, 64271 Darmstadt (Germany)
Figure 2. Cyclic peptide integrin antagonists.
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666±683
good design of the bioactive conformation leading to high
selectivities for the different integrin receptors. However, as
with all peptide drugs, the potential immunogenicity and low
bioavailibility may cause problems.
Highly potent non-peptide integrin antagonists are pres-
ently being developed. Prominent examples are summarized
in Figure 3 (avb3-selective[11±16]) and Figure 4 (aIIbb3-selec-
core units in RGD mimics. The THF ring as the general
structure 13 (Figure 5) in our RGD mimics is located at the
conformationally sensitive glycine position of the original
RGD sequence. We anticipated that the variation of the
absolute and relative configuration at the stereogenic centers
C-2 and C-5 of the THF ring offers the opportunity to tune the
O
O
R
linker
HN
O
5
2
N
OH
HN
H
NH2
N
H
13
linker type
A
B
NHR
O
C
n = 0,1
N
n H
Figure 5. Potential integrin antagonists of type 13 with a 2,5-disubstituted
THF core unit, a variable linker to the guanidino function, and a constant
(S)-b-amino-alanine side chain.
Figure 3. Examples for non-peptide aVb3 antagonists.
O
O
OH
receptor activity and selectivity. Our simple initial hypothesis
was that trans THFs should lead to more extended conforma-
tions of the RGD mimics and therefore to compounds which
are more active towards the aIIbb3 integrin. Whereas by the
use of cis THFs preferably bent conformations of the RGD
mimics should be induced, hence some avb3 selectivity was
expected. This hypothesis was based on the results from the
cyclic RGD peptides in which very potent avb3-type antago-
nists display a ªglycine centered in a g-turnº conformation,
while the most active aIIbb3 inhibitors exhibit a ªturn ± ex-
tended-turnº conformation.[3] While the (S)-b-amino-alanine
side chain had been proven to be a useful aspartic acid
mimic,[11] we decided to work with this subunit and con-
centrate on target structures of type 13. Three types of
linkers between the THF unit and the guanidino function
were investigated: a simple four atom methylene chain (type
A), a four atom methylene chain with an additional chiral
center and a nitrogen substituent (type B), and an amide
linker of different length with an additional chiral center
(type C).
O
N
N
O
OH
N
N
O
N
H
H2N
O
H2N
O
NH
NH
9
8
active form of Sibrafiban
Roche[18]
active form of Gantofiban
Merck KGaA[17]
O
O
OH
O
H
N
O
OH
N
H
N
H
HN
O
H2N
NH2
NH
11
10
Fradafiban
Boehringer Ingelheim[19]
active form of Xemilofiban
Monsanto-Searle[20]
O
HN
OH
O
S
N
O
H
O
12
Tirofiban
Merck & Co.[21]
Results and Discussion
Figure 4. Examples for non-peptide aIIbb3 antagonists.
Synthesis: The synthesis of all four stereoisomers of the type
A linked target structures 14, 15, 16, and 17 (Figure 6) used
one common stereocenter from the chiral pool as starting
point for the THF-ring construction. The (S)-acetonide
bromide 20 is readily available from l-malic acid[24] and has
recently been used as a valuable building block for the
stereoselective synthesis of 2,5-disubstituted THFs.[25, 26] It was
converted into the corresponding organomagnesium com-
pound and allowed to react with the aldehyde 19,[27] which is
accessible by Swern oxidation[29] of the alcohol 18. Thus, the
secondary alcohol 21 was obtained in good yield as a 1:1
epimeric mixture.
tive[17±22]). The underlying design principles for all these
compounds are quite similar. They consist of a rigid pref-
erably achiral core unit which links a guanidine-type func-
tionality (or secondary amine functionality in 9) and a
carboxylic acid moiety. Efforts to use a carbohydrate frame-
work as central template led to a rather low receptor
affinity.[15]
In this paper we describe the synthesis and biological
evaluation of a series of tetrahydrofuran (THF)-based
integrin antagonists. The aim of our work was first of all to
investigate the potential of 2,5-disubstituted THFs[23] as chiral
Chem. Eur. J. 2000, 6, No. 4
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667

U. Koert et al.
FULL PAPER
of the epoxide by the OH group gave the THF alcohol
ent-23 (inversion at C2, retention at C5).[26] A one-step
procedure using 4 equiv NaH and 1.2 equiv tosylimidazole[28]
gave a higher yield than the three-step route via the
mesitylene sulfonate. However, the stereocontrol of the
tosylimidazole procedure was not complete. Due to the
formation of the secondary tosylate as a minor by-product,
only a 9:1 selectivity was achieved.
A two-step oxidation (Swern[29]‡NaClO2[30]) of the alcohol
23 led to the THF carboxylic acids 25 and 26 after chromato-
graphic separation of the trans and cis isomers (Scheme 3).
O
O
O
Z
O
Z
O
N
O
OH
N
OH
H
H
H
H
H
H
HN
N
N
HN
H
H
H2N
H2N
NH
15
NH
14
O
O
O
Z
O
Z
O
O
N
OH
N
OH
H
H
H
H
H
H
HN
N
N
HN
H
H
H2N
H2N
NH
NH
17
16
Figure 6. THF-based RGD mimetics 14, 15, 16, and 17 with type A linker.
Br
23
O
O
O
20
a
a,b
BnO
OH
BnO
H
HO
O
O
BnO
b
18
19
O
O
21
1:1 epimeric mixture
O
O
OH
OH
H
H
H
H
O
Z
BnO
BnO
Scheme 1. Preparation of the alcohol 21: a) (COCl)2, DMSO, Et3N,
CH2Cl2, 60 !08C, 30 min, 98%; b) Mg, THF, 08C, 20 min, 80%.
26
25
NBoc
NH2
H3N
OMe
Cl
N
BocHN
Two stereochemical complementary pathways for closing
the THF ring were established. After conversion of the
hydroxy function of 21 into a leaving group (tosylate or
mesylate), the cleavage of the acetonide provided the diols
22a and 22b, which reacted in an intramolecular Williamson
reaction to yield the THF alcohol 23 (retention at C2,
inversion at C5).[25] In the case of the mesylate 22b the
THF-ring closure occurred directly under the acidic condi-
tions of the acetonide cleavage (see Scheme 2). The second
H
27
28
O
O
c,d
e
O
H
N
H
OMe
Z
25
H
N
HO
H
29
O
O
f,g
O
N
OMe
14
H
H
H
N
BocN
H2N
Z
H
NBoc
30
a or b
c; d or e
21
O
O
j
h,i
O
N
OMe
26
H
H
H
N
HO
Z
H
31
O
O
O
X
OH OH
HO
24
BnO
BnO
k,l
O
N
H
OMe
15
H
H
22a X = p-TsO
22b X = MesO
N
BocN
H2N
Z
H
NBoc
32
Scheme 3. Synthesis of the RGD-mimetics 14 and 15: a) (COCl)2, DMSO,
Et3N, CH2Cl2, 60 !08C, 30 min; b) NaClO2, NaH2PO4, amylene, t-
BuOH, rt, 12 h, 77%; 40% of 25 and 21% of 26 after chromatography;
c) H2, 10% Pd/C, THF/MeOH/H2O 4:2:1, rt, 18 h; d) 27, BOP, EtN(iPr)2,
MeCN, rt, 16 h, 89% from 25; e) 28, PPh3, diisopropyl azodicarboxylate,
THF, rt, 16 h, 62%; f) LiOH, THF, H2O, rt, 20 min; g) TFA, CH2Cl2, rt, 2 h,
85% from 30; h) and i) see c) and d), 62% from 26; j) see e), 74%; k) and
l) see f) and g), 79% from 32. BOP ˆ 1-benzotriazol-1-yloxytris(dimethy-
lamino)phosphonium hexafluorophosphate, TFA ˆ trifluoroacetic acid.
O
O
OH
OH
H
H
H
H
BnO
BnO
23
ent-23
Scheme 2. Stereocomplementary routes to the THF alcohols 23 and ent-
23: a) i) p-TsCl, pyridine, CH2Cl2, rt, 2 h; ii) HOAc, H2O, rt, 13 h; iii) NaH,
THF/DMSO, 408C, 4 h, 63% from 21; b) i) MesCl, Et3N, CH2Cl2, 158C,
1 h; ii) 1n HCl, THF, rt, 2 h, 77% from 21; c) 1n HCl, THF, rt, 2 h, 90%;
d) i) mesitylenesulfonyl chloride, pyridine, CH2Cl2, 08C, 36 h; ii) K2CO3,
MeOH, rt, 2 h; iii) HOAc, CH2Cl2, rt, 2 h, 48%; e) NaH, tosylimidazole,
THF, rt, 45 min, 77%. p-Ts ˆ para-toluenesulfonyl, Mes ˆ methanesulfon-
yl, DMSO ˆ dimethyl sulfoxide.
The stereochemical assignment of the relative configuration
at the THF ring was possible by NMR spectroscopy. Evalua-
tion of the NOESY spectrum from 26 showed 2-H/5-H and
3-H/5-H cross peaks for the cis isomer (Figure 7), which were
absent in the case of the trans-isomer 25.
route started with the cleavage of the acetonide in 21 to
the corresponding triol. A subsequent stereocontrolled con-
version of the 1,2-diol group into an epoxide function
(21 !24) followed by an intramolecular 5-exo opening
Hydrolytic cleavage of the benzylether in 25 and coupling
(BOP/EtN(iPr)2)[31] of the resulting hydroxycarboxylic acid
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Chem. Eur. J. 2000, 6, No. 4

Integrin Antagonists
666±683
with the amine component 27
delivered the amide 29 in 89%
yield. The amine component is
available via Hofmann degra-
dation and esterfication of
H
HA
HB
H
HA
3
H
5'
HB
H
COOH
HB
R
H
3'
R
H
O
2'
CONHR'
3'
5
2
R
O
O
HA
5'
H
H
2'
CONHR'
HA
H
Z-protected
l-asparagine.[32]
17
16
3J2,3-H(B) = 9.0 Hz
3J2,3-H(A) = 4.5 Hz
Using the guanidine reagent
28 the introduction of the Boc-
protected guanidino group
(29 !30) was achieved by a
Mitsunobu reaction.[33] Hydro-
lysis of the methyl ester, N-Boc
Figure 8. Sterochemical assignment of the trans configuration of 16 and
the cis configuration of 17 from depicted NOESY data.
Figure 7. Sterochemical assign-
ment of the cis configuration of
26 from NMR data.
Three THF-RGD mimetics 38, 39, and 40 of type B linker
were accessible from the N-protected ornithine derivative 41
(Figure 9).
deprotection, and RP-HPLC purification gave the free trans-
THF guanidine carboxylic acid 14. Along the same route the
cis-THF guanidine carboxylic acid 15 was prepared from the
cis-THF carboxylic acid 26.
For the synthesis of the two other type-A linked stereo-
isomers 16 and 17, the separation of the trans and cis isomers
was performed in a later stage of the guanidine methyl esters
36 and 37 (Scheme 4). Thus, the THF alcohol ent-23 was
H
N
H
N
Z
O
Z
O
O
R
O
O
O
N
OH
N
OH
SO2Bu
H
H
H
H
H
H
HN
N
N
HN
H
H
H2N
H2N
NH
NH
39
38 R = SO2Bu
40 R = Z
O
O
O
Z
a,b
c,d
ent-23
O
O
N
OMe
Figure 9. THF-based RGD mimetics 38, 39, and 40 with type B linker.
OH
H
H
H
H
H
N
HO
BnO
H
33
34
O
O
Z
O
N
OMe
e
H
H
The acylation the bis-N-protected carboxylic acid 41 to the
ketone 42 required some effort. Acylation of the lithium salt
or the acid chloride failed.[34] The two N-protecting groups
(Boc and Z) with their free NH groups were not compatible
with these reaction conditions. A successful conversion of 41
to 42 was possible via the thiopyridine ester of 41.[35] Reaction
of the thiopyridine ester with the butenyl Grignard reagent in
THF at 788C afforded 27% of the desired product 42
(Scheme 2). The yield could be improved to 92% by trans-
metallation of the Grignard reagent with CuCN/2LiCl at
408C and subsequent addition of the thiopyridine ester.
Reduction of the ketone 42 with l-selectride gave the two
epimeric alcohols 43 and 44 in a 3:1 ratio. The stereochemical
assignment of compounds 43 and 44 was possible by NMR
studies of the corresponding oxazolidinones 45 and 46. In the
case of the cis oxazolidinone a preferred conformer 47
exhibits a J4,5 ˆ 7.7 Hz, while the preferred conformer of the
trans oxazolidinone 48 exhibits a J4,5 ˆ 5.3 Hz.[36]
H
BocN
H2N
N
H
35
NBoc
f
O
O
Z
O
O
Z
O
N
H
OMe
O
N
H
OMe
H
H
h
H
H
HN
N
N
HN
H
H2N
H
H2N
37
NH
36
NH
g
17
16
Scheme 4. Synthesis of the RGD-mimetics 16 and 17: a) (COCl)2, DMSO,
Et3N, CH2Cl2, 60 !08C, 30 min; b) NaClO2, NaH2PO4, amylene, t-
BuOH, rt, 12 h; 64%; c) H2, 10% Pd/C, THF/MeOH/H2O 4:2:1, rt, 18 h;
d) 27, BOP, EtN(iPr)2, MeCN, rt, 16 h, 75% from 34; e) 28, PPh3,
diisopropyl azodicarboxylate, THF, rt, 16 h, 78%; f) TFA, CH2Cl2, rt, 2 h,
HPLC separation of the trans and cis isomer; g) LiOH, THF, H2O, rt,
20 min, 10% from 35; h) LiOH, THF, H2O, rt, 2 h 6% from 35. BOP ˆ 1-
Benzotriazol-1-yloxytris(dimethylamino)phosphonium hexafluorophos-
phate, TFA ˆ trifluoroacetic acid.
In order to support this assignment, an X-ray crystal
structure analysis of the p-nitrobenzoate 49, a crystalline
derivative of the main reduction epimer 43, was done.
(Figure 10). The results from the NMR studies and from the
X-ray crystal structure analysis were consistent.
oxidized to the carboxylic acid 33, which was coupled with the
amine unit 27 to yield the amide 34. The latter was trans-
formed into the N-Boc-protected guanidine 35. After N-Boc
deprotection the trans-THF 36 and the cis-THF 37 were
separated by RP-HPLC. Hydrolysis of the methyl ester group
gave the final RGD-mimetics 16 and 17.
The stereochemical assignment of the relative configura-
tion in 16 and 17 was achieved by NMR spectroscopy. The
NOESY spectrum of 16 and 17 showed 2'-H/3'-H and 3'-H/5'-
H cross peaks for the trans-isomer 16 and 2'-H/5'-H and 3'-H/
5'-H cross peaks for the cis-isomer 17 (Figure 8).
The stereochemical outcome of the l-selectride reduction
deserves some comments. In related reductions of for
example the alanine-derived ketones the opposite selectivity
is observed.[37] An explanation for the non-Felkin ± Anh
selectivity observed in the reduction of 42 may be a chelating
effect of the N-Boc group.
The terminal alkene 43 was epoxidized with MCPBA to a
1:1 epimeric mixture of epoxy alcohols, which by treatment
with PPTS underwent an intramolecular epoxide opening to
give the THF alcohol 50 as a 1:1 mixture at C-2 (Scheme 6).
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U. Koert et al.
FULL PAPER
H
H
H
H
Z
N
OH
O
Z
Z
N
Z
N
O
Z
N
a
c,d
a,b
O
O
Boc
H
Boc
H
O
OH
OH
Boc
Boc
H
H
H
H
43
H
H
N
N
N
N
41
42
H
50
51
H
H
O
Z
N
N
b
H3N
OMe
SO2Bu
CF3CO2
Boc
H
OH
+
Boc
N
H
OH
N
N
52
O
H
Z
N
O
NBoc
SMe
43
44
O
e
N
H
OMe
Boc
H
H
H
BocHN
d
c
N
Z
N
SO2Bu
H
53
54
O
O
H
H
N
O
5
N
4
O
f,g
4
5
H
N
Boc
N
H
H
Boc
O
O
Z
N
O
N
O
46
45
H
O
O
N
H
OMe
SO2Bu
N
H
OMe
H
H
H
H
N
HN
HN
N
J4,5 = 7.7 Hz
δ5-H = 4.61
J4,5 = 5.3 Hz
δ5-H = 4.20
H
SO2Bu
H
BocHN
BocHN
56
55
NBoc
NBoc
10o
-110o
H
h
H
R
i
R
H
NH
NH
39
O
38
O
O
O
H
Scheme 6. Synthesis of the RGD-mimetics 38 and 39: a) MCPBA, CH2Cl2,
rt, 12 h; b) PPTS, CH2Cl2, rt, 12 h; 90% from 43; c) (COCl)2, DMSO, Et3N,
CH2Cl2, 60 !08C, 30 min; d) NaClO2, NaH2PO4, amylene, t-BuOH, rt,
12 h; 64% from 50; e) 52, HOBt, EDC, EtN(iPr)2, THF, rt, 16 h, 61%;
f) TFA, CH2Cl2, rt, 2 h; g) 54, HgCl2, Et3N, DMF, rt, 3 h, HPLC separation
of the cis and trans isomers, 38% of 55 and 13% of 56; h) i) LiOH, THF,
H2O, rt, 20 min; ii) TFA, CH2Cl2, rt, 2 h, 66%; i) see h, 43%. MCPBA ˆ
meta-chloroperoxybenzoic acid, PPTS ˆ pyridinium para-toluenesulfonate,
HOBt ˆ 1-Hydroxy-1H-benzotriazole, EDC ˆ N'-(3'-Dimethylaminoprop-
yl)-N-ethylcarbodiimide hydrochloride.
48
47
R = (CH2)2-NHBoc
Scheme 5. Acylation of 41 and stereoselective reduction of ketone 42:
a) i) 2-mercaptopyridine, N,N'-diisopropylcarbodiimide, CH2Cl2, 94%;
ˆ
i) 2.4 equiv CuCN Â 2LiCl, 2.4 equiv BrMgCH2CH2CH CH2, THF,
78 ! 58C, 30 min, 92%; b) l-selectride, THF,
100 ! 708C,
30 min; 46% of pure 43 after crystallisation; c) NaH, THF, rt, 18 h, 90%;
d) NaH, THF, rt, 18 h, chromatography, 15%. l-selectride ˆ Lithium-tri-
sec-butylborohydride.
In order to evaluate the effect of the butylsulfonyl group
versus the Z group on receptor binding the trans-THF RGD
mimetic[32] 40 containing a Z-group was synthesized analogous
to the route for compounds 38 and 39 (Scheme 7). In the case
H
Z
N
O
O
Z
a
O
51
N
H
OMe
Boc
H
H
H
N
N
H
57
H
Z
N
O
O
b,c
O
N
OMe
H
H
H
N
HN
Z
H
BocHN
58
NBoc
d,e
40
Scheme 7. Synthesis of the RGD-mimetic 40: a) 27, HOBt, EDC, Et-
N(iPr)2, THF, rt, 16 h, crystallization of the trans isomer, 37%; b) TFA,
CH2Cl2, rt, 2 h; c) 54, HgCl2, Et3N, DMF, rt, 3 h, 73% from 57; d) i) LiOH,
THF, H2O, rt, 20 min; ii) TFA, CH2Cl2, rt, 2 h, 46% from 58.
Figure 10. X-ray crystal structure of the p-nitrobenzoate 49.
Oxidation of 50 yielded the carboxylic acid 51. Coupling of 51
with the b-amino alanine derivative 52[32] resulted in the
amide 53. After Boc deprotection an primary amine was
obtained, which was allowed to react with the iso-thiourea
54[38] to produce after chromatographic (HPLC) diastereomer
separation the trans-THF compound 55 and the cis-THF
compound 56. Cleavage of the guanidine protecting groups
and hydrolysis of the methyl ester yielded the RGD-mimetics
38 and 39.
of 40, the isomerically pure trans-THF epimer could be
separated by crystallization after the coupling reaction of the
carboxylic acid 51 with amine component 27.
The stereochemical assignment of compounds 38, 39, and
40 was possible by NMR studies. The results from the
evaluation of the corresponding NOESY spectra are sum-
marized in Figure 11.
670
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Chem. Eur. J. 2000, 6, No. 4

Integrin Antagonists
666±683
membered ring 70, which occurred initially as major product,
could be suppressed to some extend by optimized reaction
conditions. Deprotection of the guanidino function and
hydrolysis of the methyl ester gave access to the RGD-
mimetic 61. Along the same routes the cis-THF derivative 66
was converted via the diamides 71 and 72 into the two cis-THF
RGD mimetics 60 and 62.
H
HA
3'
2'
CONR'
R
2'
R
O
O
5'
H
O
5'
HB
H NR'
H
H
H
Figure 11. Sterochemical assignment of the relative configuration at the
THF rings of 38, 39, and 40 from NOESY data.
O
O
Z
The third group of RGD mimetics (type C) with an amide
linker of different length and an additional chiral center was
addressed next. Four target structures 59, 60, 61, and 62 were
chosen (Figure 12).
O
c,d
a,b
O
N
OMe
N
59
61
H
H
H
H
H
H
BocHN
N
N
H
H
67
64
O
O
Z
g
O
e,f
O
O
O
O
Z
O
Z
N
OMe
N
H
H
O
O
BocHN
BocN
O
O
N
OH
N
OH
N
N
H
H
H
H
NH
H
H
H
H
N
HN
N
HN
68
H
H
H2N
H2N
NH
NH
60
59
O
O
OH
O
O
O
O
HN
N
HN
Boc
n
O
O
BocHN
O
O
N
OH
N
OH
N
NBoc
N
H
H
70
69a n = 1
69b n = 2
H
H
NBoc
H
H
H
H
N
H2N
HN
N
H2N
HN
Z
Z
H
H
NH
NH
62
61
O
O
O
j,k
n
Figure 12. THF-based RGD mimetics 59, 60, 61, and 62 with type C linker.
h,i
O
N
OMe
OMe
N
60
H
H
H
H
H
N
N
BocHN
Z
H
H
71
66
Starting point for the synthesis of the four type C linked
target structures were the N-Boc-protected THF amino acids
63 and 65 (Scheme 8).[34] The trans-THF configuration of 63
O
O
O
l,m
O
N
62
N
H
H
H
BocHN
BocN
Z
NH
72
O
O
O
Z
a
Scheme 9. Synthesis of the RGD-mimetics 59, 60, 61, and 62: a) TFA,
CH2Cl2, rt, 2 h; b) N-Boc-glycine, HOBt, EDC, EtN(iPr)2, THF, rt, 18 h,
94% from 64; c) i) TFA, CH2Cl2, rt, 2 h; ii) 54, HgCl2, Et3N, DMF, rt, 2.5 h,
93%; d) i) LiOH, THF, H2O, rt, 20 min; ii) TFA, CH2Cl2, rt, 2 h, 60%;
e) TFA, CH2Cl2, rt, 2 h; f) 69b, HOBt, EDC, EtN(iPr)2, THF, 08C !rt, 3 h,
rt, 3 h, 75% from 64; g) see d), 72%; h) and i): see a) and b), 81%; j) and k):
see c) and d), 67%; l) and m): see e) and f) 35% 72 and 29% 70; n) see d),
79%.
O
O
Boc
N
OH
Boc
N
H
N
OMe
H
H
H
H
H
H
N
H
64
63
O
O
O
Z
b
O
O
Boc
N
OH
Boc
N
H
N
H
OMe
H
H
H
H
H
N
H
66
65
Scheme 8. Synthesis of compounds 64 and 66: a) 27, HOBt, EDC,
EtN(iPr)2, THF, rt, 16 h, 81%; b) see a) 84%.
Biological evaluation: The RGD mimetics were tested for
their biological activity in a receptor binding assay.[41] All
three types of linkers led to receptor antagonists with
submicromolar activity on aIIbb3 or on avb3 (Table 1) integrin
receptor. The linker type and the relative configuration of the
THF ring had a pronounced effect on the receptor activity and
selectivity. All compounds were essentially inactive on avb5,
probably as a result of the b-amino alanine side chain which is
known to be specific for the b3-integrin.[11]
All four compounds with the flexible type A linker (14, 15,
16, and 17) showed a stronger binding with the aIIbb3 than with
the avb3-type receptor. Compound 14 exhibited a high activity
and selectivity for aIIbb3 (IC50 ˆ 20nm, IC50 (avb3) ˆ 3.5 mm)
and may be a good candidate for further delevopment. The
relative and absolute configuration of the THF ring in this
series has a remarkable influence on the binding to the aIIbb3
receptor: The trans compounds are more active than the cis
compounds, the most potent is the 2'S,5'S-stereoisomer 14.
The three compounds 38, 39, and 40 with type B linker were
found to be active in the nanomolar range for binding with the
and the cis-THF configuration of 65 have been established by
X-ray crystal structure analysis.[34] Coupling (HOBt/EDC) of
the Boc-protected THF amino acids with the amine compo-
nent 27 gave the two amides 64 and 66.
The trans-THF amide 64 was N-Boc deprotected and
allowed to react with N-Boc-glycine to yield the diamide 67
(Scheme 9). After conversion of the N-Boc group in 67 into a
guanidino function the completion of the carbon skeleton of
the RGD mimetic was obtained. All attempts to use building
block 69a for the combined introduction of the linker and the
guanidino function failed, as a result of the easy formation of
the five-membered creatinine-like heterocycle. Deprotection
of the guanidino function in 67 and hydrolysis of the methyl
ester provided the target compound 59. The tripeptide 68 with
an additional carbon atom in the linker chain was synthesized
from the N-Boc deprotected form of 64 by coupling with
building block 69b.[39] This time, the formation of the six-
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671

U. Koert et al.
FULL PAPER
Table 1. Effect of compounds (14 ± 17, 38 ± 40, and 59 ± 62) on ligand
interaction with integrins.[a]
Linker type
Compound
IC50 [mm]
avb3
IC50 [mm]
aIIbb3
IC50 [mm]
aVb5
A
A
A
A
B
B
B
C
C
C
C
14
15
16
17
38
39
40
59
60
61
62
2
3.5
1.8
7.1
0.02
0.39
0.21
2.7
> 10
> 10
8.8
5.9
> 10
> 10
> 10
> 10
> 10
> 10
> 10
> 10
1.8
0.20
0.41
0.052
4.8
0.24
1.82
0.067
0.32
> 10
0.29
> 10
6.4
> 10
0.71
> 10
0.003
0.32
GRGDSPK
6.0
> 10
[a] Biotinylated ligands vitronectin (avb3 and avb5) or fibrinogen (aIIbb3)
were allowed to bind to immobilized integrins in the presence of the
compounds 14 ± 17, 38 ± 40, and 59 ± 62. The concentration necessary for
half-maximum inhibition of ligand binding is shown. The peptide
GRGDSPK and compound 2 were included for reference. The sign > in-
dicates that the IC50 had not been reached at the maximum concentration
tested (10 mm).[41]
aIIbb3 and with the avb3 receptor. This time, the trans-THF
compound was more active than its cis counterpart at the
aIIbb3 and the avb3 integrin. The comparison between com-
pounds 38 and 40 allowed the evaluation of the N-substituent
of the b-amino alanine part: The benzyloxycarbonyl (Z)
group led to 3 ± 4 times stronger binding than the butylsul-
fonyl group. By comparison of 40 and 16 the beneficial effect
of the type B linker for avb3 binding can be clearly seen
(enhancement of avb3 binding by factor 140 versus 3 for aIIbb3
binding).
In the type C linker series the trans ± cis effect was most
pronounced: Both cis-compounds 60 and 62 showed no
activity. The central cis-THF amino acid in 60 and 62 was
recently recognized as b-turn mimic.[34] Analogy of the NMR
parameters in the THF part indicated that an energetically
favorable hydrogen bond also fixed 60 and 62 in a b-turn like
conformation. This b-turn like conformation leads to a
collapse of the RGD motif and a complete loss of binding.
The trans-THF compounds 59 and 61, which cannot adopt a b-
turn like conformation, showed activity for both receptors
with some selectivity in favor of the aIIbb3 receptor. The effect
of the linker length on receptor binding is seen in the
comparison between both compounds: In the avb3 case the
longer linker 61 resulted in a higher activity, whereas no
substantial effect of the linker length was found for the aIIbb3
receptor affinity.
Figure 13. Overlay of low energy conformations of THF-based RGD
mimetics, THF ring in green; top: 40 (yellow 83% and blue 15% populated
at 298 K); bottom: 62 (yellow 87% and blue 8% populated at 298 K).
of 62. Interestingly an anologous hydrogen-bonded motif of
39 was not observed either by molecular modeling nor by
NMR techniques. The benzyloxycarbonylamino substituent
adjacent to the THF in 40 (Figure 13, top) obviously forces the
guanidino side chain into a direction appropiate for avb3 (and
aIIbb3) binding far away from the carboxylic acid moiety.
Additionally performed molecular modeling studies on all
RGD mimics were of limited validity due to the inherent
flexibility of these compounds. Only in the case of 60 and 62
and the type B linker structures 38, 39, and 40 we were able to
locate pronounced minimum conformers. Representative
overlays of the calculated minimum conformers of 62 and 40
our most active compound on the avb3 integrin are displayed
in Figure 13.
Conclusion
The work presented here shows that 2,5-disubstituted tetra-
hydrofurans are well suited as a new core unit for RGD
mimetics. The activity and selectivity of the receptor binding
can be addressed by choosing the relative and absolute
configuration of the stereocenters at the THF ring and the
linker type. Synthetic routes to the different stereoisomers
The tight arrangement of the pharmacophoric groups in
Figure 13, bottom is presumably the reason for the inactivity
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Chem. Eur. J. 2000, 6, No. 4

Integrin Antagonists
666±683
4-H2), 2.44 (td, J ˆ 7.1, 1.4 Hz, 2H, 2-H2), 3.48 (t, J ˆ 6.0 Hz, 2H, 5-H2), 4.49
(s, 2H, CH2-Ph), 7.25 ± 7.38 (m, 5H, Ph), 9.74 (t, J ˆ 1.5 Hz, 1H, CHO);
13C NMR (75 MHz, CDCl3): d ˆ 18.9 (C-3), 29.0 (C-4), 43.5 (C-2), 69.7 (C-
5), 72.8 (CH2-Ph), 127.48, 127.54, 128.3, 138.4 (Ph), 202.4 (C-1).
were successfully established. In agreement with our initial
hypothesis all RGD mimics possessing a trans-THF unit were
considerably more active on the aIIbb3 integrin than their
comparable cis-THF counterparts. A good selectivity and
activity for aIIbb3 was observed for compound 14 with type A
linker. The use of cis-THF compounds did not automatically
generate avb3 activity or selectivity. Although our best RGD
mimic in terms of avb3 selectivity 39 (factor 4.4) was cis
configured, the trans-THF compound 40 was the best in terms
of avb3 activity. In order to achieve higher activity towards the
avb3 receptor the use of the type B linker seems to be more
important than the THF configuration. The b-turn imitating
cis-THF amino acid as central core (in 60 and 62) is not
suitable for integrin binding.
The present work focuses on selected stereoisomers for
each linker type. From the results obtained the investigation
of further stereoisomers are promising. In particular the type
B linker, where only two stereoisomers were tested, should be
explored in future work. General conclusions on structure ±
activity relationships can only be given after the biological
data of these compounds are available.
(2S,5RS)-9-Benzyloxy-1,2-O-isopropyliden-nonane-1,2,5-triol (21): After
Mg turnings (182 mg, 7.50 mmol) in THF (3 mL) were activated with some
drops of dibromoethane, a solution of bromide 20 (1.04 g, 5.00 mmol,
filtered through 5 g silica gel prior to use with PE/Et2O 5:1) in THF (5 mL)
was added dropwise in a manner that the internal temperature did not
exceed 408C. After additional stirring for 1 h at room temperature, the
Grignard solution was cooled to 08C and a solution of aldehyde 19 (460 mg,
2.39 mmol) in THF (5 mL) was added within 10 min. After 20 min at room
temperature, sat. aqueous NH4Cl (20 mL) was added, and the two-phase
system was stirred for additional 1 h. The layers were separated and the
aqueous layer was extracted with Et2O (3 Â 20 mL). The combined organic
layers were washed with sat. aqueous NaCl (30 mL) and dried with MgSO4.
Removal of the solvents in vacuo and purification by CC (30 g, PE/Et2O
1:1) afforded the epimeric alcohol 21 (620 mg, 80%) as a colorless oil. Rf ˆ
0.30 (PE/Et2O 1:2); IR (neat): nÄ ˆ 3445m (OH), 3030w (ArH), 2985m/
2935s/2860s (CH), 1455m, 1370s, 1255m, 1215m, 1155m, 1100s, 1060s,
1030m, 855w, 735m, 700m; 1H NMR (300 MHz, CDCl3): d ˆ 1.35, 1.41 (2s,
6H, 2CH3) superimposed by 1.35 ± 1.74 (m, 10H, 3-H2, 4-H2, 6-H2, 7-H2,
8-H2), 1.90 ± 2.69 (m, 1H, OH), 3.47 (t, J ˆ 6.4 Hz, 2H, 9-H2), superimposed
by 3.46 ± 3.66 (m, 2H, 1-HA, 5-H), 3.98 ± 4.13 (m, 2H, 1-HB, 2-H), 4.49 (s,
2H, CH2-Ph), 7.22 ± 7.35 (m, 5H, Ph); 13C NMR (75 MHz, CDCl3): d ˆ 22.3
(C-7), 25.6, 26.9 (2CH3), 29.6 (C-8), 29.5 and 30.0, 33.5 and 33.7, 37.1 and
37.2 [C-3, C-4, C-6 (two epimers each)], 69.4 (C-1), 70.2 (C-9), 71.1, 71.4 [C-
5 (two epimers)], 72.8 (CH2-Ph), 76.1 (C-2), 108.8 (Cq, ketal), 127.4, 127.5,
128.2, 138.4 (Ph); C19H30O4 (322.45): calcd C 70.78, H 9.38; found C 71.05,
H 9.09.
The new synthetic routes to THF-integrin antagonists
presented herein and the promising biological evaluation of
these new class of compounds should encourage further
efforts to develop prospective drug candidates for the therapy
of thrombosis, angiogenesis, and tumor metastasis.
(2S,5RS)-5-(4'-Benzyloxybutyl)-2-hydroxymethyl-tetrahydrofuran (23) via
tosylation: Pyridine (1.5 mL) and p-toluene sulfonyl chloride (750 mg,
3.93 mmol) were added at 08C to a solution of alcohol 21 (322 mg,
1.00 mmol) in CH2Cl2 (5 mL). After the solution was stirred for 4 h at room
temperature, water (5 mL) was added, and the stirring was continued until
excess p-toluene sulfonyl chloride was destroyed. The mixture was adjusted
to pH 2 with 1n aqueous HCl. After separation of the layers, the aqueous
layer was extracted with Et2O (2 Â 20 mL), and the combined organic
layers were washed with sat. aqueous NaHCO3 (10 mL) and sat. aqueous
NaCl (10 mL). Drying with MgSO4, removal of the solvents in vacuo, and
subsequent CC (20 g, PE/Et2O 1:1) yielded tosylate 22a (428 mg, 90%) as a
colorless oil. Rf ˆ 0.59 (PE/Et2O 1:1). Tosylate 22a (290 mg, 0.608 mmol)
was dissolved in HOAc (10 mL) and H2O (2 mL). After the solution was
stirred at room temperature for 13 h, the solvents were removed in vacuo at
room temperature. Toluene (10 mL) was added and subsequently removed
in vacuo (2Â). The obtained crude product was used without further
purification for the following cyclization step. Rf ˆ 0.07 (Et2O). After the
crude product was dissolved in THF (10 mL), NaH (95%, 100 mg,
3.96 mmol) and four drops of DMSO were added. The reaction mixture
was allowed to stir for 4 h at 408C. At 08C HOAc (8 mL) was added
carefully and the solvents were removed in vacuo. The crude product was
partitioned between H2O (10 mL) and Et2O (30 mL). The layers were
separated and the aqueous layer was extracted with Et2O (30 mL). The
organic layers were washed with sat. aqueous NaHCO3 (15 mL) and sat.
aqueous NaCl (10 mL). After drying with MgSO4 and removal of the
solvents under reduced pressure, purification with CC (15 g, Et2O) yielded
the title compounds as a colorless oil (125 mg, 78% based on tosylate 22a,
63% based on the alcohol 21). Rf ˆ 0.50 (Et2O); HPLC: tR ˆ 27.5 and
30.3 min (Si 60; 4% isopropyl alcohol in n-hexane); IR (neat): nÄ ˆ 3425m
(OH), 3030w (ArH), 2930/2860s (CH), 1455m, 1360w, 1100s, 1045m, 735m,
700m, 665m; 1H NMR (300 MHz, CDCl3): d ˆ 1.32 ± 1.75 and 1.80 ± 2.06 (m,
8H; m, 2H, 3-H2, 4-H2, 1'-H2, 2'-H2, 3'-H2), 2.59 (brs, 1H, OH), 3.40 ± 3.69
(m, 4H, 4'-H2, 1''-H2), 3.80 ± 4.13 (m, 2H, 2-H, 5-H), 4.49 (s, 2H, CH2-Ph),
7.23 ± 7.36 (m, 5H, Ph); 13C NMR (75 MHz, CDCl3): d ˆ 22.7 (C-3'), 29.6
(C-2'), 26.9 and 27.4, 31.1 and 31.8, 35.4 and 35.5 [C-3, C-4 and C-1' (two
epimers each)], 64.8, 65.0 [C-1'' (two epimers)], 70.0 (C-4'), 72.7 (CH2-Ph),
78.8 [C-2 (one epimer)], 79.1 [C-2 (one epimer), C-5 (one epimer)], 79.8
[C-5 (one epimer)], 127.3, 127.5, 128.2, 138.4 (Ph); C16H24O3 (264.36): calcd
C 72.69, H 9.15; found C 72.75, H 9.08.
Experimental Section
General: All b.p.ꢁs and m.p.ꢁs are uncorrected. IR: Bruker IFS 88. NMR:
Bruker AC-300, DPX-300, AMX-500, and AMX-600. For 1H NMR: CDCl3
as solvent dH ˆ 7.25, [D6]DMSO as solvent dH ˆ 2.50, [D4]MeOH as solvent
dH ˆ 4.78; for 13C NMR: CDCl3 as solvent dC ˆ 77.0, [D6]DMSO as solvent
dC ˆ 39.5, [D4]MeOH as solvent dC ˆ 49.0. Elemental analysis: CHN Rapid
(Heraeus), CHNS-932 Analysator (Leco). HRMS: Finnigan MAT 95. All
reactions were performed under an inert atmosphere of argon in oven- or
flame-dried glassware. Dry solvents: THF, Et2O, benzene, and toluene were
distilled from sodium benzophenone. All commercially available reagents
were used without purification unless otherwise noted. All reactions were
monitored by thin-layer chromatography (TLC) carried out on Merck
F-254 silica glass plates visualized with UV light and/or heat-gun treatment
with 5% phosphomolybdic acid in ethanol or 1.2% anisaldehyde in ethanol
and 2.20% H2SO4. Column chromatography (CC) was performed with
Merck silica gel 60 (70 ± 200 mesh and 230 ± 400 mesh). PE: light petroleum
ether, b.p. 40 ± 608C. MTBE: methyl tert-butyl ether, DIAD: diisopropyl
azodicarboxylate.
5-Benzyloxypentanal (19):
201 mmol) in CH2Cl2 (100 mL) was added dropwise over a period of
20 min at 608C to solution of oxalyl chloride (10.8 mL, 15.7 g,
A solution of DMSO (14.4 mL, 15.9 g,
a
124 mmol) in CH2Cl2 (400 mL). After the reaction mixture was stirred at
this temperature for 5 min, a solution of the alcohol 18 (20.0 g, 103 mmol)
in CH2Cl2 (100 mL) was added dropwise, and the reaction mixture was
stirred for an additional 15 min. NEt3 (60.0 mL, 43.8 g, 433 mmol) was
added and the solution was stirred for further 5 min at 608C. The reaction
mixture was allowed to warm to 08C within 30 min. The reaction was
quenched by the addition of sat. aqueous NaHCO3 (400 mL). After
separation of the layers, the aqueous layer was extracted with CH2Cl2 (2 Â
300 mL). The combined organic layers were washed with sat. aqueous NaCl
(300 mL) and dried with MgSO4. After removal of the solvent in vacuo and
azeotropical distillation with toluene (50 mL), the crude product was
purified by CC (100 g, PE/Et2O 1:1) to yield aldehyde 19 (19.5 g, 98%) as a
slightly yellow liquid. Rf ˆ 0.60 (PE/Et2O 1:1); IR (neat): nÄ ˆ 3030m (ArH),
ˆ
2940/2865s (CH), 2740w (CHO), 1725s (C O), 1455m, 1365w, 1205w, 1100s,
Preparation of THF derivative 23 via mesylation: A solution of alcohol 21
(17.6 g, 54.6 mmol) in CH2Cl2 (220 mL) was treated with NEt3 (30.3 mL,
740m, 700m; 1H NMR (300 MHz, CDCl3): d ˆ 1.58 ± 1.81 (m, 4H, 3-H2,
Chem. Eur. J. 2000, 6, No. 4
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673

U. Koert et al.
FULL PAPER
22.1 g, 218 mmol) at 408C and methanesulfonyl chloride (8.53 mL, 12.5 g,
109 mmol) was added dropwise within 10 min. The reaction mixture was
allowed to warm to 158C and was stirred for 1 h at this temperature. Sat.
aqueous NaHCO3 (200 mL) was added, the layers were separated, and the
aqueous layer was extracted with Et2O (200 mL). The combined organic
layers were washed with sat. aqueous NaCl (100 mL). After the organic
layer was dried with MgSO4, the solvent was removed in vacuo. Toluene
(50 mL) was added and subsequently removed in vacuo. The obtained
crude product 22b was used without further purification for the following
steps. Rf ˆ 0.47 (PE/Et2O 1:1). Crude mesylate 22b was dissolved in THF
(100 mL) and aqueous 1n HCl (120 mL). After the solution was stirred for
4 h at room temperature, the reaction mixture was extracted with EtOAc
(3 Â 100 mL). The organic layers were washed with sat. aqueous NaCl (2 Â
50 mL), and after separation dried with Na2SO4, the solvents were removed
in vacuo. CC (300 g, PE/Et2O 1:3) afforded THF alcohol 23 as a colorless
(11.1 g, 77% based on the alcohol 21).
cohol 23 (5.00 g, 18.9 mmol) was subjected to Swern-oxidation conditions
already described for the preparation of 19 with the following amounts of
reagents: oxalyl chloride (2.48 mL, 3.60 g, 28.4 mmol) in CH2Cl2 (100 mL),
DMSO (2.95 mL, 3.25 g, 41.6 mmol) in CH2Cl2 (10 mL) and NEt3 (11.9 mL,
8.61 g, 85.1 mmol). Without purification by CC we obtained the crude
aldehyde (5.10 g) as a slightly yellow oil. Rf ˆ 0.37 (PE/MTBE 1:1). This
product was subsequently further oxidized to the corresponding carboxylic
acid: The crude aldehyde was dissolved in a mixture of t-BuOH (24 mL)
und amylene (12 mL). At 08C a solution of NaClO2 (80%, 2.72 g,
24.1 mmol) and NaH2PO4 Â H2O (3.33 g, 24.1 mmol) in water (12 mL)
was added over a period of 20 min. The mixture was allowed to stir for 12 h
at room temperature. After removal of the organic solvents in vacuo, 0.4m
aqueous NaOH (40 mL) was added. The aqueous layer was extracted with
MTBE (2 Â 20 mL) before the aqueous layer was adjusted to pH 2 by the
addition of 2m aqueous HCl solution. The obtained suspension was
extracted with EtOAc (3 Â 30 mL) and the organic layers were washed with
sat. aqueous NaCl (2 Â 10 mL). The organic layers were dried with Na2SO4,
and the solvents removed in vacuo, and the epimers then purified by CC
(2  300 g, MTBE/CH2Cl2 1:1 ‡ 1% HOAc). Epimer 26 was separated
(1.09 g, 21% based on 23) from epimer 25 (2.10 g, 40% based on 23), which
solidified after several days of storage. In addition, an unseparated
epimeric mixture of 25/26 was obtained (860 mg, 16% based on 23). Thus,
the combined yield for the two-step oxidation 23 to 25/26 was 77%.
Epimeric mixture 25/26 as dicyclohexyl ammonium salt: C28H45NO4
(459.67) calcd C 73.16, H 9.86, N 3.05; found C 73.15, H 9.88, N 2.96.
(2R,5RS)-5-(4'-Benzyloxybutyl)-2-hydroxymethyl-tetrahydrofuran (ent-
23): A solution of alcohol 21 (1.12 g, 3.47 mmol) in THF (10 mL) and 1n
aqueous HCl (6 mL) was stirred for 2 h at room temperature. The reaction
mixture was then extracted with EtOAc (3 Â 15 mL), and the combined
organic layers were washed successively with sat. aqueous NaHCO3
(20 mL) and sat. aqueous NaCl (15 mL). After the organic phase was
dried with Na2SO4, the solvents were removed under reduced pressure. CC
(20 g, EtOAc) gave the triol (885 mg, 3.13 mmol, 90%) as a colorless oil.
Rf ˆ 0.25 (EtOAc); IR (neat): nÄ ˆ 3360brs (OH), 2935/2865s (CH), 1455m,
1365m, 1315w, 1275m, 1200w, 1100s, 1070s, 1030m, 735m, 715m, 700m;
1H NMR (300 MHz, CDCl3): d ˆ 1.35 ± 1.68 (m, 10H, 3-H2, 4-H2, 6-H2,
7-H2, 8-H2), 3.46 (t, J ˆ 6.4 Hz, 2H, 9-H2), superimposed by 3.34 ± 3.71 (m,
4H, 1-H2, 2-H, 5-H), 4.48 (s, 2H, CH2-Ph), 4.67 (brs, 3H, 3OH), 7.22 ± 7.42
(m, 5H, Ph); 13C NMR (75 MHz, CDCl3): d ˆ 22.3 (C-7), 29.5 (C-8), 28.8,
29.7, 32.8, 33.6, 36.9, 37.2 [C-3, C-4, C-6 (two epimers each)], 66.2, 66.6 [C-1
(two epimers)], 70.3 (C-9), 71.3, 71.7, 72.1, 72.4 [C-2, C-5 (two epimers
each)], 72.8 (CH2-Ph), 127.5, 127.6, 128.3, 138.3 (Ph).
THF carboxylic acid 25: Rf ˆ 0.45 (MTBE ‡ 1% HOAc); [a]D
ˆ
28.8,
101.7 (c ˆ 1.06,
[a]578 30.1, [a]546 34.7, [a]436 61.5, [a]365
ˆ
ˆ
ˆ
ˆ
CHCl3, Tˆ 208C); IR (neat): nÄ ˆ 2500 ± 3500brs (COOH), 3085/3060/
ˆ
3030m (ArH), 2940/2865s (CH), 2640w, 1745s (C O), 1495w, 1455m,
1360m, 1275m, 1205m, 1095s, 1030m, 740m, 700m, 665w; 1H NMR
(600 MHz, CDCl3): d ˆ 1.38 ± 1.72 (m, 7H, 4-HA, 1'-H2, 2'-H2, 3'-H2),
2.03 ± 2.11 (m, 2H, 3-HA, 4-HB), 2.08 (m, 1H, 3-HB), 3.48 (t, J ˆ 6.4 Hz, 2H,
4'-H2), 4.08 ± 4.17 (m, 1H, 5-H), 4.46 ± 4.56 (m, 1H, 2-H), superimposed by
4.50 (s, 2H, CH2-Ph), ca. 6.0 (brs, 1H, COOH), 7.26 ± 7.31 (m, 5H, Ph);
13C NMR (75 MHz, CDCl3): d ˆ 22.5 (C-2'), 29.5, 29.9, 30.9 (C-4, C-1',
C-3'), 34.9 (C-3), 70.0 (C-4'), 72.7 (CH2-Ph), 76.1 (C-2), 80.9 (C-5), 127.4,
127.5, 128.2, 138.3 (Ph), 177.4 (COOH).
Pyridine (3.5 mL, 3.4 g, 43 mmol) and mesitylene sulfonyl chloride
(358 mg, 1.64 mmol) were added sequentially at 08C to a solution of this
triol (420 mg, 1.49 mmol) in CH2Cl2 (10 mL). After the solution was stirred
for 36 h at 08C, water (10 mL) was added, and the stirring was continued
for additional 30 min. The layers were separated and the aqueous layer was
extracted with Et2O (3 Â 10 mL). The organic layers were washed
successively with 1n aqueous HCl (20 mL), sat. aqueous NaHCO3
(10 mL) and sat. aqueous NaCl (10 mL). Subsequent drying with Na2SO4
and removal of the solvents in vacuo yielded an oily residue which was
dissolved in MeOH (15 mL). After addition of solid K2CO3 (1.00 g,
7.24 mmol), the reaction mixture was stirred for 2 h. The solvent was
removed in vacuo at room temperature. The residual oil was dissolved in
Et2O (30 mL) and washed with water (2 Â 10 mL), and then with sat.
aqueous NaCl (20 mL). After removal of the solvent in vacuo, the residue
(crude epoxide 24) was dissolved in CH2Cl2 (10 mL) and treated with
HOAc (1 mL). The reaction mixture was again stirred for 2 h at room
temperature. After addition of water (5 mL), the layers were separated and
the aqueous layer was extracted with CH2Cl2 (2 Â 5 mL). The combined
organic layers were washed with sat. aqueous NaHCO3 (10 mL) and sat.
aqueous NaCl (10 mL), and dried with Na2SO4. Removal of the solvent in
vacuo and purification with CC (20 g, PE/Et2O 1:3) afforded alcohol ent-23
(188 mg, 48% based on the corresponding triol) as a colorless oil. This
epimeric mixture was almost identical to the enantiomeric mixture 23 in all
spectroscopic respects apart from optical rotation.
THF carboxylic acid 26: m.p. 508C; Rf ˆ 0.64 (MTBE ‡ 1% HOAc); [a]D
ˆ
28.1, [a]578
ˆ
29.3, [a]546
ˆ
33.2, [a]436
ˆ
55.6, [a]365
ˆ
85.1 (c ˆ
1.00, CHCl3, Tˆ 208C); IR (KBr): nÄ ˆ 2600 ± 3600brs (COOH), 2975m/
ˆ
2940s/2885s/2865s (CH), 1760s (C O), 1455m, 1365m, 1205s, 1185m, 1125s,
1105s, 1085s, 1070s, 1050m, 1030m, 845w, 830w, 750m, 700w; 1H NMR
(600 MHz, CDCl3): d ˆ 1.40 ± 1.60 (m, 4H, 4-HA, 1'-HA, 2'-H2), 1.66 (m, 2H,
3'-H2), 1.69 ± 1.77 (m, 1H, 1'-HB), 2.02 (dddd, J ˆ 13.3, 7.7, 5.7, 3.6 Hz, 1H,
4-HB), 2.19 (dddd, J ˆ 12.7, 8.4, 4.3, 4.3 Hz, 1H, 3-HA), 2.30 (dddd, J ˆ 13.0,
9.8, 9.1, 7.7 Hz, 1H, 3-HB), 3.48 (t, J ˆ 6.4 Hz, 2H, 4'-H2), 4.02 (m, 1H, 5-H),
4.45 (dd, J ˆ 9.0, 4.5 Hz, 1H, 2-H), 4.50 (s, 2H, CH2-Ph), 7.25 ± 7.30 (m, 5H,
Ph), 9.30 (brs, 1H, COOH); 13C NMR (75 MHz, CDCl3): d ˆ 22.9 (C-2'),
29.5, 30.2, 30.8 (C-4, C-1', C-3'), 35.1 (C-3), 70.0 (C-4'), 72.8 (CH2-Ph), 76.4
(C-2), 82.0 (C-5), 127.5, 127.6, 128.3, 138.4 (Ph), 176.4 (COOH). The cis vs.
trans assignment was done unambiguously by interpretation of 600 MHz
NOESY spectra of both epimers.
(2S,2'S,5'R)-3-[5'-(4''-Hydroxybutyl)-tetrahydrofuran-2'-carbamoyl]-2-
benzyloxycarbonylamino methyl propionate (29): A solution of carboxylic
acid 25 (1.57 g, 5.61 mmol) in THF (26 mL), MeOH (13 mL), and water
(6.5 mL) was hydrogenated under vigorous stirring for 18 h at atmospheric
pressure in the presence of Pd on charcoal (10%, 140 mg). The catalyst was
removed by filtration from a pad of Celite which was washed with MeOH
(50 mL). The solvents were removed in vacuo and residual water was
removed by azeotropic distillation with toluene (2 Â 10 mL). CC (30 g,
EtOAc) yielded the unprotected carboxylic acid (1.05 g, 95%) which was
directly used in the following peptide coupling. Rf ˆ 0.22 (MTBE ‡ 1%
HOAc). This hydroxy acid, amine hydrochloride 27 (1.70 g, 5.89 mmol),
and BOP (2.61 g, 5.89 mmol) were dissolved in acetonitrile (70 mL), and
treated with EtN(iPr)2 (2.04 mL, 1.52 g, 11.8 mmol) at room temperature.
After the solution was stirred for 16 h, the solvent was removed in vacuo,
and the residue was diluted with EtOAc (300 mL). This solution was
washed successively with 2n aqueous HCl (2 Â 50 mL), sat. aqueous
NaHCO3 (2 Â 50 mL), sat. aqueous NaCl (100 mL), and was dried with
Na2SO4. After removal of the solvent in vacuo, purification with CC [65 g,
EtOAc/CH2Cl2 1:1 (600 mL), then EtOAc/CH2Cl2 3:1 (600 mL)] gave
Preparation of THF alcohol ent-23 via epoxide formation by tosyl
imidazole: A solution of the triol prepared from 21 (2.75 g, 8.53 mmol) in
THF (30 mL) was treated with NaH (95%, 861 mg, 34.1 mmol). After the
visible gas evolution stopped, the solution was stirred for further 15 min at
room temperature and then cooled to 08C. p-Toluene sulfonyl imidazole
(2.28 g, 10.2 mmol) was added in one portion and the stirring was continued
for 45 min at room temperature. The reaction was quenched by careful
addition of sat. aqueous NH4Cl (20 mL). The reaction mixture was
extracted with MTBE (3 Â 25 mL) and the organic layers were washed
with sat. aqueous NaCl (20 mL). After the organic layers were dried with
Na2SO4, evaporation of the solvents and purification with CC (100 g,
MTBE/CH2Cl2 4:1) yielded alcohol ent-23 (1.73 g, 77%) as a colorless oil.
(2S,5R)-5-(4'-Benzyloxybutyl)-tetrahydrofuran-2-carboxylic acid (25) and
(2S,5S)-5-(4'-benzyloxybutyl)-tetrahydrofuran-2-carboxylic acid (26): Al-
674
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
0947-6539/00/0604-0674 $ 17.50+.50/0
Chem. Eur. J. 2000, 6, No. 4

Integrin Antagonists
666±683
amide 29 (2.11 g, 89% based on 25) as a colorless oil. Rf ˆ 0.33 (EtOAc);
HPLC: tR ˆ 50.4 min (Si 60, 1.5 mLmin 1; 15% isopropyl alcohol in n-
analogously to the amide 29 using the following amounts of substrate and
reagents: carboxylic acid 26 (980 mg, 3.50 mmol) and Pd/C (10%, 100 mg)
to yield the unprotected carboxylic acid (660 mg, quant.). Rf ˆ 0.24
(MTBE ‡ 1% HOAc). Amine hydrochloride 27 (1.11 g, 3.85 mmol),
BOP (1.70 g, 3.85 mmol), and EtN(iPr)2 (1.33 mL, 995 mg, 7.70 mmol) to
yield amide 31 (919 mg, 62% based on 26) as colorless oil. Rf ˆ 0.33
(EtOAc); HPLC: tR ˆ 44.5 min (Si 60, 1.5 mLmin 1; 15% isopropyl alcohol
hexane); [a]D ˆ ‡4.1, [a]578 ˆ ‡4.4, [a]546 ˆ ‡5.1, [a]436 ˆ ‡9.9, [a]365
ˆ
‡19.4 (c ˆ 1.05, CHCl3, Tˆ 208C); IR (neat): nÄ ˆ 3350brs (OH/NH),
ˆ
3065/3035w (ArH), 2940s/2865m (CH), 1725s (C O), 1660s (carbamate
ˆ
C O), 1530s, 1455m, 1440m, 1345m, 1265s, 1215s, 1070s, 1030m, 845w,
1
740m, 700m; H NMR (300 MHz, CDCl3): d ˆ 1.37 ± 2.09 (m, 10H, 3'-HA,
4'-H2, 1''-H2, 2''-H2, 3''-H2, OH), 2.31 (m, 1H, 3'-HB), AB signal (dA ˆ 3.55,
dB ˆ 3.80, JAB ˆ 13.9 Hz additionally split by JA ˆ 4.5, 4.5 Hz; JB ˆ 7.6,
6.4 Hz, 2H, 3-H2), 3.65 (t, J ˆ 6.2 Hz, 2H, 4''-H2), 3.76 (s, 3H, OCH3), 3.95
(m, 1H, 5'-H), 4.36 (t, J ˆ 7.2 Hz, 1H, 2'-H), 4.41 ± 4.54 (m, 1H, 2-H), 5.11
(s, 2H, CH2-Ph), 5.88 (brd, J ˆ 7.0 Hz, 1H, NHZ), 7.09 (brt, J ˆ 5.3 Hz, 1H,
N3H), 7.25 ± 7.45 (m, 5H, Ph); 13C NMR (75 MHz, CDCl3): d ˆ 22.3 (C-2''),
30.1 (C-3'), 31.2 (C-4'), 32.4, 34.9 (C-1'', C-3''), 40.4 (C-3), 52.8 (OCH3), 54.4
(C-2), 62.6 (C-4''), 67.1 (CH2-Ph), 77.9 (C-2'), 80.8 (C-5'), 128.1, 128.2, 128.5,
136.0 (Ph), 156.0 (Z-CO), 170.7 (CONH), 174.7 (COO); ESI-MS:
in n-hexane); [a]D ˆ ‡1.1, [a]578 ˆ ‡1.4, [a]546 ˆ ‡1.9, [a]436 ˆ ‡7.0, [a]365
ˆ
‡19.9 (c ˆ 0.80, CHCl3, Tˆ 208C); IR (neat): nÄ ˆ 3400brs (OH/NH), 3065/
ˆ
ˆ
3035w (ArH), 2940s/2865m (CH), 1725s (C O), 1660s (carbamate C O),
1530s, 1455m, 1440m, 1365m, 1345m, 1215s, 1180m, 1070s, 845s, 775w,740m,
700m, 665m; 1H NMR (300 MHz, CDCl3): d ˆ 1.32 ± 1.77 (m, 7H, 4'-HA, 1''-
H2, 2''-H2, 3''-H2), 1.84 ± 2.10 (m, 3H, 3'-HA, 4'-HB, OH), 2.15 ± 2.31 (m, 1H,
3'-HB), AB signal (dA ˆ 3.65, dB ˆ 3.91, JAB ˆ 14.0 Hz additionally split by
JA ˆ 4.8, 4.8 Hz; JB ˆ 7.0, 7.0 Hz, 2H, 3-H2), 3.64 (t, J ˆ 5.9 Hz, 2H, 4''-H2),
3.75 (s, 3H, OCH3), 3.97 (m, 1H, 5'-H), 4.29 (dd, J ˆ 8.7, 4.9 Hz, 1H, 2'-H),
4.44 (m, 1H, 2-H), 5.11 (s, 2H, CH2-Ph), 5.94 (brd, J ˆ 7.0 Hz, 1H, NHZ),
7.10 (brt, J ˆ 4.9 Hz, 1H, N3H), 7.28 ± 7.40 (m, 5H, Ph); 13C NMR (75 MHz,
CDCl3): d ˆ 22.3 (C-2''), 30.3, 30.4 (C-3', C-4'), 32.3, 35.1 (C-1'', C-3''), 40.2
(C-3), 52.8 (OCH3), 54.5 (C-2), 62.3 (C-4''), 67.1 (CH2Ph), 78.2 (C-2'), 81.5
(C-5'), 128.1, 128.2, 128.5, 136.0 (Ph), 156.0 (Z-CO), 170.7 (CONH), 174.5
‡
[C21H30N2O7‡H] calcd 423.21; found 423.14.
(2S,2'S,5'R)-3-(5'-{4''-[N1''',N2'''-Bis-(tert-butoxycarbonyl)-guanidino]-bu-
tyl}-tetrahydrofuran-2'-carbamoyl)-2-benzyloxycarbonylamino
methyl
propionate (30): Amide 29 (800 mg, 1.90 mmol), guanidine derivative 28
(983 mg, 3.79 mmol), and PPh3 (746 mg, 2.84 mmol) were dissolved in THF
(14 mL) and cooled to 08C. DIAD (0.74 mL, 0.77 g, 3.8 mmol) was added
dropwise. After 16 h at room temperature, water (10 drops) was added and
the solvent was removed in vacuo. Filtration (10 g, PE/MTBE 1:2) and
purification with CC (40 g, PE/MTBE 1:1) gave compound 30 (783 mg,
‡
(COO); ESI-MS: [C21H30N2O7‡Na] calcd 445.20; found 445.14.
(2S,2'S,5'S)-3-(5'-{4''-[N1''',N2'''-Bis-(tert-butoxycarbonyl)-guanidino]-bu-
tyl}-tetrahydrofuran-2'-carbamoyl)-2-benzyloxycarbonylamino
methyl
propionate (32): The guanidine derivative 32 was prepared as described
for 30 using the following amounts of substrate and reagents: amide 31
(600 mg, 1.42 mmol), guanidine derivative 28 (735 mg, 2.83 mmol), PPh3
(558 mg, 2.13 mmol), and DIAD (0.55 mL, 0.57 g, 2.8 mmol). Title com-
pound 32 (693 mg, 74%) was obtained as a colorless oil. Rf ˆ 0.38 (PE/
62%) as a colorless oil. Rf ˆ 0.38 (PE/MTBE 1:2); [a]D
ˆ
13.0, [a]578
44.8 (c ˆ 0.40, CHCl3, Tˆ
ˆ
13.8, [a]546 15.5, [a]436 27.5, [a]365
ˆ
ˆ
ˆ
208C); IR (neat): nÄ ˆ 3380m (NH), 2975m/2935m/2865w (CH), 1715s
ˆ
(C O), 1675m, 1645m, 1610s, 1515s, 1455m, 1435m, 1390m, 1370m, 1345m,
1
1280s, 1250s, 1150s, 1100s, 980w, 915w, 890w, 780w, 735m, 700w; H NMR
MTBE 1:2); [a]D
ˆ
3.1, [a]578
ˆ
3.3, [a]546
ˆ
3.5, [a]436
ˆ
4.5, [a]365
ˆ
(300 MHz, CDCl3): d ˆ 1.48, 1.52 (2s, 2tBu), 1.23 ± 1.70 (m, 7H; m, 2H, 3'-
HA, 4'-H2, 1''-H2, 2''-H2, 3''-H2), 2.22 ± 2.40 (m, 1H, 3'-HB), 3.48 ± 4.01 (m,
8H, 5'-H, 3-H2, 4''-H2, OCH3), 4.33 (brt, J ˆ 7.1 Hz, 1H, 2'-H), 4.40 ± 4.49
(m, 1H, 2-H), 5.10 (s, 2H, CH2-Ph), 5.98, 6.08 (2brd, J ˆ 7.5 Hz each, 1H,
NHZ rotamers), 7.10 (brs, 1H, N3H), 7.27 ± 7.40 (m, 5H, Ph), 9.29 (brs, 2H,
NH2); 13C NMR (75 MHz, CDCl3): d ˆ 23.0 (C-2''), 27.9, 28.1 [2C(CH3)3],
28.6, 30.0, 31.0 (C-4', C-1'', C-3''), 34.8 (C-3'), 40.2 (C-3), 44.3 (C-4''), 52.6
(OCH3), 54.4 (C-2), 66.9 (CH2-Ph), 77.8 (C-2'), 78.5, 83.4 [2C(CH3)3], 80.8
3.3 (c ˆ 0.85, CHCl3, Tˆ 208C); IR (neat): nÄ ˆ 3380m (NH), 2975m/
ˆ
2935m/2865w (CH), 1715s (C O), 1680m, 1640m, 1610s, 1515s, 1455m,
1440m, 1390m, 1370m, 1345w, 1280s, 1250s, 1210m, 1150s, 1105m, 980w,
1
890w, 780w, 735w, 700w, 665w; H NMR (300 MHz, CDCl3): d ˆ 1.48, 1.52
(2s, 18H, 2tBu), 1.21 ± 2.32 (m, 10H, 3'-H2, 4'-H2, 1''-H2, 2''-H2, 3''-H2),
3.52 ± 4.00 (m, 8H, 3-H2, 5'-H, 4''-H2, OCH3), 4.22 ± 4.33 (m, 1H, 2'-H),
4.39 ± 4.50 (m, 1H, 2-H), 5.11 (s, 2H, CH2-Ph), 5.82, 5.97 (2brd, J ˆ 7.5 Hz
each, 1H, NHZ rotamers), 7.02 (brs, N3H), 7.28 ± 7.40 (m, 5H, Ph), 9.29
(brs, 2H, NH2); 13C NMR (75 MHz, CDCl3): d ˆ 23.5 (C-2''), 28.0, 28.3
[2C(CH3)3], 28.5, 30.3, 30.6 (C-4', C-1'', C-3''), 35.2 (C-3'), 40.3 (C-3), 44.4
(C-4''), 52.8 (OCH3), 54.6 (C-2), 67.0 (CH2Ph), 78.0 (C-2'), 78.7, 83.6
ˆ
(C-5'), 127.9, 128.1, 128.4, 136.2 (Ph), 155.4 (C N), 156.6 (Z-CO), 160.5,
163.7 (2Boc-CO), 170.6 (CONH), 174.7 (COO); ESI-MS:
‡
[C32H49N5O10‡H] calcd 664.36; found 664.37.
ˆ
[2C(CH3)3], 81.4 (C-5'), 128.1, 128.2, 128.5 (Ph), 155.0 (C N), 170.7
(2S,2'S,5'R)-3-[5'-(4''-Guanidinobutyl)-tetrahydrofuran-2'-carbamoyl]-2-
(CONH), 174.5 (COO); the signals with low intensity (Z-CO, Boc-CO and
benzyloxycarbonylamino propionic acid (14, as trifluoroacetate):
A
‡
Arq) were not detected; ESI-MS: [C32H49N5O10‡H] calcd 664.36; found
solution of THF derivative 30 (90 mg, 0.14 mmol) in THF (3 mL) was
treated at room temperature with LiOH (1.0 mL of a 0.3m aqueous
solution, 0.30 mmol). After 20 min the reaction mixture was adjusted to
pH 3 by the addition of 5% aqueous citric acid. The solvent was removed in
vacuo and the aqueous layer was extracted with EtOAc (3 Â 10 mL). The
organic layers were washed with sat. aqueous NaCl (10 mL) and dried with
MgSO4. The solvent was removed under reduced pressure and the residue
was dissolved in CH2Cl2 (4 mL), and treated with TFA (1.5 mL). After the
solution was stirred for 2 h, the reaction mixture was codistilled with
toluene (2 Â 5 mL). The residue was purified by preparative HPLC [41 mm
ID, Rainin, RP 18, 40 mLmin 1, 77% (water‡ 0.2% TFA) and 23%
(acetonitrile ‡ 0.2% TFA)] to yield the trifluoracetate 14 (65 mg, 85%).
HPLC: tR ˆ 12.8 min (Rainin, RP 18, 1 mLmin 1, 20% to 60% B within
20 min, A: water ‡ 0.2% TFA; B: acetonitrile ‡ 0.2% TFA); 1H NMR
(600 MHz, CD3CN ‡ 10% D2O): d ˆ 1.24 ± 1.65 (m, 7H, 4'-HA, 1''-H2, 2''-
H2, 3''-H2), 1.72 ± 1.79 (m, 1H, 3'-HA), 1.83 ± 1.90 (m, 1H, 4'-HB), 2.21 (m,
1H, 3'-HB), 3.03 ± 3.08 (m, 2H, 4''-H2), AB signal (dA ˆ 3.48, dB ˆ 3.52,
JAB ˆ 13.8, additionally split by JA ˆ 5.1 Hz; JB ˆ 7.9 Hz, 2H, 3-H2), 3.94
(dddd, all Jvic ꢀ6.6 Hz, 1H, 5'-H), 4.22 ± 4.28 (m, 2H, 2-H, 2'-H), AB signal
(dA ˆ 5.02, dB ˆ 5.03, JAB ˆ 12.6 Hz, 2H, CH2-Ph), 7.26 ± 7.37 (m, 5H, Ph);
13C NMR (75 MHz, [D6]DMSO): d ˆ 23.5 (C-2''), 29.2, 31.1, 31.4, 35.2 (C-3',
C-4', C-1'', C-3''), 41.8 (C-4''), 54.7 (br, C-2), 67.3 (CH2-Ph), 78.4 (C-2'), 81.6
664.36.
(2S,2'S,5'S)-3-[5'-(4''-Guanidinobutyl)-tetrahydrofuran-2'-carbamoyl]-2-
benzyloxycarbonylamino propionic acid (15, as trifluoroacetate): The
preparation and purification was done as described for 14 starting from
THF derivative 32 (86 mg, 0.13 mmol). After lyophylization, trifluoroace-
tate 15 (58 mg, 79%) was obtained as a white solid. HPLC: tR ˆ 12.7 min
(Rainin, RP 18, 1 mLmin 1, 20% to 60% B within 20 min, A: water‡
1
0.2% TFA; B: acetonitrile ‡ 0.2% TFA); H NMR (600 MHz, CD3CN ‡
5% D2O): d ˆ 1.26 ± 1.63 (m, 7H, 4'-HA, 1''-H2, 2''-H2, 3''-H2), 1.86 ± 1.94
(m, 2H, 3'-HA, 4'-HB), 2.16 (m, 1H, 3'-HB), 3.08 (t, J ˆ 6.8 Hz, 2H, 4''-H2),
3.35 ± 3.65 (m, 2H, 3-H2)*, 3.90 (m, 1H, 5'-H), 4.22 (dd, J ˆ 8.7, 4.3 Hz, 1H,
2'-H), 4.29 (dd, J ˆ 7.5 and 2.5 Hz, 1H, 2-H), 5.05 (m, 2H, CH2-Ph), 7.26 ±
7.38 (m, 5H, Ph); *superimposed by HOD signal; 13C NMR (150 MHz,
CD3CN ‡ 33% D2O): d ˆ 22.8 (C-2''), 28.0, 30.0, 30.3, 34.4 (C-3', C-4',
C-1'', C-3''), 39.5 (C-3), 41.2 (C-4''), 53.9 (C-2), 67.4 (CH2-Ph), 77.7 (C-2'),
82.4 (C-5'), 127.8, 128.6, 129.0 (Ph), 176.7, 177.2 (CONH, COO); the signals
with low intensity (Z-CO, guanidine-C and Arq) were not detected; HRMS
‡
(FAB): [C21H32N5O6] calcd 450.2353; found 450.2358.
(2R,5RS)-5-(4'-Benzyloxybutyl)-tetrahydrofuran-2-carboxylic acid (33):
The two-step oxidation was performed analogous to the preparation of
the carboxylic acids 25/26 starting from the alcohol ent-23 (5.00 g,
18.9 mmol). The following amounts of reagents were used: oxalyl chloride
(3.30 mL, 4.80 g, 37.8 mmol) in CH2Cl2 (150 mL), DMSO (4.10 mL, 4.51 g,
57.0 mmol) in CH2Cl2 (20 mL), and NEt3 (15.7 mL, 11.4 g, 113 mmol).
Without purification by CC the corresponding crude aldehyde (5.03 g) was
obtained as yellow oil. Rf ˆ 0.37 (PE/MTBE 1:1). Subsequent Pinnick-
oxidation using t-BuOH (24 mL), amylene (12 mL), NaClO2 (80%, 2.72 g,
ˆ
(C-5'), 128.8, 129.4, 129.7, 137.5 (Ph), 157.5, 157.8 (C N, Z-CO), 176.3
(CONH, COO); the signal of C-3 at approx. d ˆ 40 was superimposed by
‡
the solvent signals; HRMS (FAB): [C21H32N5O6] calcd 450.2353; found
450.2347.
(2S,2'S,5'S)-3-[5'-(4''-Hydroxybutyl)-tetrahydrofuran-2'-carbamoyl]-2-ben-
zyloxycarbonylamino methyl propionate (31): The amide 31 was prepared
Chem. Eur. J. 2000, 6, No. 4
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
0947-6539/00/0604-0675 $ 17.50+.50/0
675

U. Koert et al.
FULL PAPER
24.1 mmol), and NaH2PO4 Â H2O (3.33 g, 24.1 mmol) in water (12 mL)
yielded after usual work-up a slightly yellow crude product. This was
further purified by means of the dicyclohexyl ammonium salt: The crude
carboxylic acid was dissolved in MTBE (100 mL) and treated with
dicyclohexyl amine (4.98 mL, 4.53 g, 25 mmol). After removal of the
solvent in vacuo, the remaining solid was recrystallized from MTBE/PE
2:1. The obtained ammonium salt was dissolved in MTBE (300 mL) and the
free acid was liberated by washing with 1n aqueous HCl (2 Â 100 mL).
After drying of the organic layer with Na2SO4 and removal of the solvent
the title compound (3.37 g, 64%) was obtained as an epimeric mixture.
Rf ˆ 0.40 ± 0.65 (MTBE ‡ 1% HOAc); IR (neat): nÄ ˆ 2500 ± 3500brs
tection and isomer separation could not be determined due to the presence
of excess buffer salt from HPLC. Only pure diastereomers were used for
subsequent ester hydrolysis, mixed fractions were not used further. HPLC:
tR ˆ 11.7 min (37) and 12.4 min (36) (Rainin, RP 18, 1.5 mLmin 1, 23% to
30% B within 15 min, A: water‡ 0.1% TFA ‡ 0.1% NEt3; B: acetonitrile ‡
0.1% TFA ‡ 0.1% NEt3). Each separated isomer was dissolved in THF
(5 mL) and treated with 0.3n aqueous LiOH (10 mL). After 2 h, the
reaction mixture was acidified with TFA. After concentration in vacuo to
about 6 mL, the crude material was purified by preparative HPLC [3 runs,
41 mm ID, Rainin, RP 18, 40 mLmin 1, 77% (water‡ 0.2% TFA) and
23% (acetonitrile ‡ 0.2% TFA)]. After lyophylization, the trifluoroace-
ˆ
(COOH), 3085/3060/3030m (ArH), 2940/2865s (CH), 1750brs (C O),
tate of 17 (28 mg, 6%) and 16 (42 mg, 10%) was obtained as a white solids.
1
1495w, 1455m, 1365m, 1280m, 1205m, 1100s, 1030w, 740m, 700m, 665w; 33
as dicyclohexyl ammonium salt: C28H45NO4 (459.67) calcd C 73.16, H 9.86,
N 3.05; found C 72.79, H 9.76, N 3.02; 1H and 13C NMR spectra of 33 were a
correct superimposition of the spectra for the separated epimers 25/26.
Trifluoroacetate of 16: HPLC: tR ˆ 12.8 min (Rainin, RP 18, 1 mLmin
,
20% to 60% B within 20 min, A: water‡ 0.2% TFA; B: acetonitrile
‡0.2% TFA); 1H NMR (600 MHz, CD3CN ‡ 10% D2O): d ˆ 1.32 ± 1.59
(m, 7H, 4'-HA, 1''-H2, 2''-H2, 3''-H2), 1.78 ± 1.87 (m, 1H, 3'-HA), 1.87 ± 1.94
(m, 1H, 4'-HB), 2.22 (m, 1H, 3'-HB), 3.04 ± 3.09 (m, 2H, 4''-H2), AB signal
(dA ˆ 3.41, dB ˆ 3.62, JAB ˆ 13.9 Hz, additionally split by JA ˆ 7.5 Hz, JB ˆ
4.6 Hz, 2H, 3-H2), 3.87 ± 3.97 (m, 1H, 5'-H), 4.23 ± 4.29 (m, 2H, 2-H, 2'-H),
AB signal (dA ˆ 5.03, dB ˆ 5.07, JAB ˆ 12.6 Hz, 2H, CH2-Ph), 7.31 ± 7.37 (m,
5H, Ph); 13C NMR (75 MHz, [D6]DMSO ‡ 2% D2O): d ˆ 23.0 (C-2''), 28.8
(C-3''), 30.2, 30.6 (C-3', C-4'), 34.9 (C-1''), 41.0 (C-4''), 53.9 (C-2), 66.1 (CH2-
Ph), 77.8 (C-2'), 80.4 (C-5'), 128.1, 128.4, 128.9, 137.2 (Ph), 156.6, 156.9
(2S,2'R,5'RS)-3-[5'-(4''-Hydroxybutyl)-tetrahydrofuran-2'-carbamoyl]-2-
benzyloxycarbonylamino methyl propionate (34): The amide 34 was
prepared as described for the amide 29 using the following amounts of
substrate and reagents: carboxylic acid 33 (1.93 g, 6.93 mmol) and Pd/C
(10%, 180 mg) to yield the unprotected carboxylic acid (1.21 g, 93%). Rf ˆ
0.12 ± 0.24 (MTBE ‡ 1% HOAc). Amine hydrochloride 27 (1.92 g,
6.64 mmol), BOP (2.95 g, 6.67 mmol), and NEt3 (1.97 mL, 1.43 g,
14.1 mmol) instead of EtN(iPr)2 yielded amide 34 (2.20 g, 5.21 mmol,
75% based on 33) as a colorless oil. Rf ˆ 0.33 (EtOAc); HPLC: tR ˆ 49.0
and 52.7 min (Si 60, 1.5 mLmin 1; 15% isopropyl alcohol in n-hexane); IR
(neat): nÄ ˆ 3360brm (OH/NH), 3065/3035w (ArH), 2940m/2865w (CH),
ˆ
(C N, Z-CO), 172.3, 174.2 (CONH, COO); the signal of C-3 at approx. d ˆ
‡
40 was superimposed by the solvent signals. HRMS (FAB): [C21H32N5O6]
calcd 450.2353; found 450.2353. Trifluoroacetate of 17: HPLC: tR ˆ
12.6 min (Rainin, RP 18, 1 mLmin 1, 20% to 60% B within 20 min, A:
water‡ 0.2% TFA; B: acetonitrile ‡ 0.2% TFA); 1H NMR (600 MHz,
CD3CN ‡ 5% D2O): d ˆ 1.26 ± 1.63 (m, 7H, 4'-HA, 1''-H2, 2''-H2, 3''-H2),
1.86 ± 1.97 (m, 2H, 3'-HA, 4'-HB), 2.16 (m, 1H, 3'-HB), 3.08 (t, J ˆ 7.1 Hz,
2H, 4''-H2), 3.41 (dd, J ˆ 14.0, 8.0 Hz, 1H, 3-HA), 3.71 (dd, J ˆ 14.0, 5.0 Hz,
1H, 3-HB), 3.90 (m, 1H, 5'-H), 4.23 (dd, J ˆ 8.8, 4.5 Hz, 1H, 2'-H), 4.32 (dd,
J ˆ 8.0, 5.1 Hz, 1H, 2-H), 5.05 (m, 2H, CH2-Ph), 7.28 ± 7.38 (m, 5H, Ph);
13C NMR (75 MHz, CD3CN ‡ 10% D2O): d ˆ 24.0 (C-2''), 29.0 (C-3''), 31.0,
31.1 (C-3', C-4'), 35.5 (C-1''), 40.6 (C-3), 42.0 (C-4''), 54.7 (C-2), 67.5 (CH2-
Ph), 78.7 (C-2'), 82.4 (C-5'), 128.7, 129.1, 129.5, 137.5 (Ph), 157.7 (Z-CO,
ˆ
ˆ
1720s (C O), 1660s (carbamate C O), 1530s, 1455m, 1440m, 1345w, 1300m,
1260m, 1215m, 1070s, 1055m, 700w, 645w; 1H NMR (300 MHz, CDCl3): d ˆ
1.37 ± 1.71, 1.80 ± 2.36 (m, 7H; m, 4H, 3'-H2, 4'-H2, 1''-H2, 2''-H2, 3''-H2,
OH), 3.48 ± 3.82 (m, 7H, 3-H2, 4''-H2, OCH3), 3.88 ± 4.01 (m, 1H, 5'-H),
4.26 ± 4.50 (m, 2H, 2-H, 2'-H), 5.11 (s, 2H, CH2-Ph), 6.02 [brd, J ˆ 7.7 Hz,
0.5H, NHZ (one epimer)], 6.06 [brd, J ˆ 7.5 Hz, 0.5H, NHZ (one epimer)],
7.12, 7.14 [2brs, 1H, N3H (two epimers)], 7.28 ± 7.42 (m, 5H, Ph); 13C NMR
(75 MHz, CDCl3): d ˆ 22.4 (C-2''), 30.0, 30.2, 30.6, 31.3, 32.2, 32.4, 34.9, 35.1
[C-3', C-4', C-1'', C-3'' (two epimers each)], 40.7 (C-3), 52.7 (OCH3), 54.5
(C-2), 62.2 and 62.5 (C-4''), 67.0 (CH2-Ph), 77.4 and 77.9 (C-2'), 80.8 and 81.5
(C-5'), 128.0, 128.1, 128.5, 136.1 (Ph), 156.2 (Z-CO), 170.7 (CONH), 174.8
‡
ˆ
C N), 173.3, 176.4 (CONH, COO); HRMS (FAB): [C21H32N5O6] calcd
450.2353; found 450.2351. The cis vs. trans assignment was done
unambiguously by interpretation of 600 MHz NOESY spectra of both
epimers.
‡
(COO); ESI-MS: [C21H30N2O7‡H] calcd 423.21; found 423.12.
(2S,2'R,5'RS)-3-(5'-{4''-[N1''',N2'''-Bis-(tert-butoxycarbonyl)-guanidino]-
butyl}-tetrahydrofuran-2'-carbamoyl)-2-benzyloxycarbonylamino methyl
propionate (35): The guanidine derivative 35 was prepared as described
for 30 using the following amounts of substrate and reagents: amide 34
(930 mg, 2.21 mmol), guanidine derivative 28 (1.15 g, 4.42 mmol), PPh3
(868 mg, 3.31 mmol), and DIAD (0.65 mL, 0.67 g, 4.4 mmol); title com-
pound 35 (1.14 g, 78%) was obtained as a colorless oil. Rf ˆ 0.38 (PE/
MTBE 1:2); IR (neat): nÄ ˆ 3390brs (NH/OH), 2980/2940 (CH), 1715s
(4S)-4-Benzyloxycarbonylamino-1-tert-butoxycarbonylamino-8-nonene-5-
one (42): A solution of 4-bromo-1-butene (7.34 g, 54.4 mmol) in Et2O
(65 mL) was added dropwise to Mg turnings (1.98 g, 81.6 mmol) covered
with Et2O (14 mL) in a manner that the reaction gently refluxed. After
cooling to room temperature, the reaction mixture was diluted with Et2O
(60 mL) and refluxed for 1 h. The Grignard solution was cooled to room
temperature again and transferred to a 250 mL dropping funnel via a
double ended needle. Ornithine derivative 41 (5.00 g, 13.6 mmol) was
dissolved in a 1 L three-necked flask in Et2O (280 mL), and cooled to
788C. n-BuLi (1.7m in hexanes, 16.0 mL, 27.2 mmol) was added dropwise
and a white precipitate soon formed. After 15 min at this temperature, the
reaction mixture was allowed to warm to 08C and the Grignard solution
was added within 1 h. The reaction mixture was stirred overnight at room
temperature. The reaction was quenched at 08C by careful addition of sat.
aqueous NH4Cl (120 mL). After separation of the layers, the aqueous layer
was extracted with MTBE (3 Â 150 mL). The combined organic extracts
were washed with sat. aqueous NaHCO3 (2 Â 100 mL) and sat. aqueous
NaCl (200 mL). After the organic phases were dried with Na2SO4, the
solvents were removed in vacuo. CC (50 g, PE/MTBE 2:1) and recrystal-
lization from MTBE (5 mL) yielded ketone 42 (730 mg, 13%) as a white
solid. M.p. 75 ± 768C (MTBE); Rf ˆ 0.48 (PE/MTBE 1:1); [a]D ˆ ‡40.1,
[a]578 ˆ ‡42.2, [a]546 ˆ ‡49.4, [a]436 ˆ ‡106.3, [a]365 ˆ ‡225.5 (c ˆ 0.98,
CHCl3, Tˆ 208C); IR (neat): nÄ ˆ 3355m (NH), 3065w (CH olef.), 3035w
ˆ
(C O), 1680m, 1640m, 1610s, 1515s, 1455m, 1440m, 1390m, 1370m, 1280s,
1250s, 1150s, 1100s, 980m, 885w, 850w, 780w, 745w, 700w; 1H NMR
(300 MHz, CDCl3): d ˆ 1.48, 1.52 (2s, 2tBu), 1.20 ± 1.77, 1.87 ± 2.40 (m, 7H;
m, 3H, 3'-H2, 4'-H2, 1''-H2, 2''-H2, 3''-H2), 3.52 ± 4.03 (m, 8H, 5'-H, 3-H2, 4''-
H2, OCH3), 4.27 ± 4.52 (m, 2H, 2-H, 2'-H), 5.11 (s, 2H, CH2-Ph), 5.93 ± 6.09
(m, 1H, NHZ), 7.05 (brs, 1H, N3H), 7.26 ± 7.38 (m, 5H, Ph), 9.28 (brs, 2H,
NH2); 13C NMR (75 MHz, CDCl3): d ˆ 23.1 and 23.4 (C-2''), 28.2, 28.5
[2C(CH3)3], 28.7, 30.0, 30.2, 30.6, 31.1 [C-4', C-1'', C-3'' (two epimers each)],
34.9 and 35.1 (C-3'), 40.6 (C-3), 44.3 (C-4''), 52.6 (OCH3), 54.7 (br, C-2), 67.0
(CH2-Ph), 78.0 (C-2'), 78.7, 83.5 [2C(CH3)3], 80.9 and 81.7 (C-5'), 128.0,
ˆ
128.1, 128.4, 136.1 (Ph), 155.0 (C N), 156.7 (Z-CO), 160.6, 163.8 (2Boc-
‡
CO), 170.6 (CONH), 174.7 (COO); ESI-MS: [C32H49N5O10‡H] calcd
664.36; found 664.37.
(2S,2'R,5'S)-3-[5'-(4''-Guanidinobutyl)-tetrahydrofuran-2'-carbamoyl]-2-
benzyloxycarbonylamino propionic acid (16, as trifluoroacetate) and
(2S,2'R,5'R)-3-[5'-(4''-guanidinobutyl)-tetrahydrofuran-2'-carbamoyl]-2-
benzyloxycarbonylamino propionic acid (17, as trifluoroacetate): A sol-
ution of 35 (515 mg, 0.776 mmol) in CH2Cl2 (20 mL) was treated with TFA
(6 mL) at room temperature. After the solution was stirred for 2 h, the
solvents were removed in vacuo, and the residue was azeotropically
distilled with toluene (20 mL). The crude guanidinium salt was divided in
ˆ
(ArH), 2960w/2930w (CH aliph.), 1715s (CO), 1680s (carbamate C O),
1525s, 1455w, 1390w, 1365m, 1350w, 1285m, 1235m, 1165m, 1060w, 695w;
1H NMR (300 MHz, CDCl3): d ˆ 1.34 (s, 9H, tBu), superimposed by 1.34 ±
1.52 (m, 3H, 2-H2, 3-HA), 1.74 ± 1.88 (m, 1H, 3-HB), 2.24 (ddd, all Jvic
ꢀ6.9 Hz, 2H, 7-H2), 2.35 ± 2.58 (m, 2H, 6-H2), 2.96 ± 3.12 (m, 2H, 1-H2),
4.20 ± 4.38 (m, 1H, 4-H), 4.68 (brs, 1H, BocNH), 4.84 ± 5.03 (m, 4H, 9-H2,
Ph-CH2), 5.56 ± 5.78 (m, 2H, 8-H, NH), 7.18 ± 7.30 (m, 5H, Ph); 13C NMR
(75 MHz, CDCl3): d ˆ 25.8 (C-2), 27.3 (C-7), 28.3 [C(CH3)3], 28.5 (C-3),
10 portions which were partially separated by preparative HPLC [41 mm
1
ID, 40 mLmin
,
74% (water‡ 0.2% TFA ‡ 0.2% NEt3) and 26%
(acetonitrile ‡ 0.2% TFA ‡ 0.2% NEt3)]. The yield of this Boc depro-
676
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
0947-6539/00/0604-0676 $ 17.50+.50/0
Chem. Eur. J. 2000, 6, No. 4

Integrin Antagonists
666±683
ˆ
38.7 (C-6), 39.8 (C-1), 59.2 (C-4), 66.8 (Ph-CH2), 79.0 [C(CH3)3], 115.5 (C-
138.1 (C-8), 156.1, 156.7 (Boc-, Z-C O); C22H34N2O5 (406.52): calcd C
65.00, H 8.43, N 6.89; found C 65.20, H 8.20, N 6.81.
ˆ
9), 127.9, 128.0, 128.4, 136.2 (Ph), 136.5 (C-8), 155.9 (Boc-, Z-C O), 208.2
(C-5).
(4S,5R)-5-(But-3'-ene-1'-yl)-4-(3''-tert-butoxycarbonylamino-prop-1''-yl)-
1,3-oxazolidin-2-one (45): A solution of alcohol 43 (150 mg, 0.369 mmol) in
THF (5 mL) was treated with NaH (95%, 14 mg, 0.58 mmol) at 08C. After
stirring for 18 h at room temperature, water (5 mL) was added. The mixture
was extracted with MTBE (3 Â 10 mL), and the organic layers were washed
with sat. aqueous NaCl (10 mL). After drying with Na2SO4 the solvents
were removed in vacuo. CC (20 g, MTBE) yielded compound 45 (100 mg,
Preparation of the ketone 42 via cuprate addition to 41 activated as
2-thiopyridine ester: Diisopropyl carbodiimide (4.05 mL, 3.48 g,
27.6 mmol) was added within 5 min at 08C to a solution of ornithine
derivative 41 (10.1 g, 27.6 mmol) and 2-mercapto pyridine (3.07 g,
27.6 mmol) in CH2Cl2 (30 mL). After additional 5 min, the ice bath was
removed and the reaction mixture was stirred for 4 h at room temperature.
The precipitated urea was removed by filtration after cooling to 08C and
washed with cool CH2Cl2 (10 mL). The filtrate was washed with 0.4m
aqueous NaOH (10 mL) and sat. aqueous NaCl (20 mL). After drying
with Na2SO4 and removal of the solvent in vacuo the corresponding
thioester (12.1 g, approx. 94%) was obtained as a yellow oil which
contained little diisopropyl urea. It was not possible to remove this
impurity by CC (300 g, PE/MTBE 1:3). Thus, this slightly impurified
materials was used for further transformations. Rf ˆ 0.52 (MTBE); 1H NMR
(300 MHz, CDCl3): d ˆ 1.38 (s, 9H, tBu), superimposed by 1.38 ± 1.78 (m,
3H, 3-HA, 4-H2), 1.82 ± 2.04 (m, 1H, 3-HB), 3.07 (m, 2H, 5-H2), 4.59 (m, 1H,
2-H), 4.74 (brs, 1H, NH), 5.12 (s, 2H, Ph-CH2), 6.02 (brs, 1H, NH), 7.20 ±
7.39 (m, 6H, Ph, 5'-H), 7.54 (d, J ˆ 7.8 Hz, 1H, 3'-H), 7.69 (t, J ˆ 7.6 Hz, 1H,
4'-H), 8.57 (m, 1H, 6'-H); 13C NMR (75 MHz, CDCl3): d ˆ 26.1 (C-4), 28.3
[C(CH3)3], 29.4 (C-3), 39.8 (C-5), 61.1 (C-2), 67.2 (Ph-CH2), 79.2 [C(CH3)3],
123.5 (C-5'), 128.0, 128.1, 128.4, 136.0 (Ph), 130.3 (C-3'), 137.1 (C-4'), 150.3
90%) as a slightly yellow oil. Rf ˆ 0.60 (EtOAc); [a]D
ˆ
10.3, [a]578
ˆ
11.1, [a]546 12.4, [a]436 22.8, [a]365
ˆ
ˆ
ˆ
38.1 (c ˆ 0.52, CHCl3, Tˆ
ˆ
208C); IR (neat): nÄ ˆ 3315m (NH), 2975m/2930m (CH), 1750s (C O),
ˆ
1700s (C O), 1640w, 1520m, 1455w, 1390m, 1365m, 1250m, 1170m, 1100w,
1040w, 915w; 1H NMR (300 MHz, CD3OD): d ˆ 1.42 (s, 9H, tBu),
superimposed by 1.38 ± 1.68 (m, 6H, 1'-H2, 1''-H2, 2''-H2), 2.08 ± 2.35 (m,
2H, 2'-H2), 3.06 (brt, J ˆ 5.6 Hz, 2H, 3''-H2), 3.79 (ddd, J ˆ 8.0, 8.0, 3.5 Hz,
1H, 4-H), 4.61 (ddd, J ˆ 9.8, 7.7, 4.0 Hz, 1H, 5-H)*, 5.01 (dm, J ˆ 10.2 Hz,
1H, 4'-HE), 5.07 (dq, J ˆ 17.1, 1.7 Hz, 1H, 4'-HZ), 5.85 (ddt, J ˆ 17.1, 10.2,
6.8 Hz, 1H, 3'-H); *two homonuclear decoupling experiments verified
J4,5 ˆ 7.7 Hz; 13C NMR (75 MHz, CD3OD): d ˆ 27.5, 28.3, 29.6, 31.2 (C-1',
C-2', C-1'', C-2''), 28.8 [C(CH3)3], 40.8 (C-3''), 56.4 (C-4), 79.9 [C(CH3)3],
81.1 (C-5), 116.0 (C-4'), 138.5 (C-3'), 158.5 (Boc-CO), 161.7 (CO).
(4S,5S)-5-(But-3'-ene-1'-yl)-4-(3''-tert-butoxycarbonylamino-prop-1''-yl)-
1,3-oxazolidin-2-one (46): A solution of alcohol 44 (ds ꢀ 3:1) in THF
(7 mL) was treated with NaH (95%, 30 mg, 1.25 mmol) at 08C. After 18 h
at room temperature the reaction was quenched by the addition of half sat.
aqueous NaCl (20 mL) at 08C. This mixture was extracted with EtOAc
(30 mL), the organic layers were washed with sat. aqueous NaCl (10 mL)
and dried with MgSO4. Removal of the solvents in vacuo and separation by
CC (20 g, MTBE) yielded compound 46 (32 mg, 15%) as a colorless oil.
ˆ
(C-6'), 151.0 (C-2'), 156.0 (Boc-, Z-C O), 198.4 (C-1). A solution of
4-bromo-1-butene (2.34 mL, 3.24 g, 24.0 mmol) in THF (14 mL) was added
dropwise to Mg turnings (0.73 g, 30 mmol) covered with THF (7 mL). The
solution of the bromide was added in a manner that the reaction mixture
gently refluxed and was refluxed for additional 1 h at the end of the
addition. A solution of dry LiCl (2.03 g, 48.0 mmol) and CuCN (2.12 g,
24.0 mmol) in THF (30 mL) was prepared at room temperature in a
separate flask. The cold grignard solution was added 408C within 10 min
to this greenish solution. After 15 min at this temperature, the reaction
mixture was cooled to 788C and and a solution of the thiopyridine ester
(4.60 g, 10.0 mmol) in THF (20 mL) was added dropwise within 10 min.
After 10 min the reaction mixture was allowed to warm to 58C within
30 min. The reaction was quenched by careful addition of sat. aqueous
NH4Cl (30 mL). The orange precipitate was removed by filtration through
a pad of Celite and was washed with MTBE (300 mL). The layers were
separated and the aqueous layer was extracted with MTBE (3 Â 30 mL).
The combined organic layers were washed with sat. aqueous NaCl (40 mL)
and dried with Na2SO4. The solvents were removed in vacuo and
recrystallization from MTBE (40 mL) yielded ketone 42 (3.72 g,
9.20 mmol, 92%).
Rf ˆ 0.32 (MTBE); [a]D
ˆ
50.3, [a]578
ˆ
52.6, [a]546
ˆ
61.4, [a]436
ˆ
105.2, [a]365
ˆ
163.8 (c ˆ 0.58, CHCl3, Tˆ 208C); IR (neat): nÄ ˆ
ˆ
ˆ
3315m (NH), 3080w, 2975/2935m (CH), 1750s (C O), 1710s (C O),
1520m, 1455m, 1390s, 1365m, 1250s, 1170s; 1H NMR (300 MHz, CD3OD):
d ˆ 1.42 (s, 9H, tBu), superimposed by 1.40 ± 1.60, 1.70 ± 1.80 (m, 4H; m,
2H, 1'-H2, 1''-H2, 2''-H2), 2.19 (m, 2H, 2'-H2), 3.04 (brt, J ˆ 6.0 Hz, 2H, 3''-
H2), 3.48 (brddd, all J ꢀ 5.5 Hz, 1H, 4-H), 4.20 (ddd, J ˆ 7.4, 5.3, 5.3 Hz,
1H, 5-H)*, 4.99 (dm, J ˆ 10.4 Hz, 1H, 4'-HE), 5.06 (dq, J ˆ 17.1, 1.7 Hz, 1H,
4'-HZ), 5.84 (ddt, J ˆ 17.0, 10.3, 6.6 Hz, 1H, 3'-H); *two homonuclear
decoupling experiments verified J4,5 ˆ 5.3 Hz; 13C NMR (75 MHz,
CD3OD): d ˆ 26.6, 30.1, 33.5, 35.2 (C-1', C-2', C-1'', C-2''), 28.8
[C(CH3)3], 40.8 (C-3''), 58.7 (C-4), 79.9 [C(CH3)3], 83.1 (C-5), 116.0 (C-
4'), 138.5 (C-3'), 158.6 (Boc-CO), 161.5 (CO).
(4S,5R)-4-Benzyloxycarbonylamino-1-tert-butoxycarbonylamino-8-non-
ene-5-yl-p-nitrobenzoate (49):
A solution of alcohol 43 (300 mg,
(4S,5R)-4-Benzyloxycarbonylamino-1-tert-butoxycarbonylamino-8-non-
ene-5-ol (43): Ketone 42 (1.59 g, 3.94 mmol) was dissolved in THF (40 mL)
and cooled to 1008C. l-Selectride (11.8 mL of a 1m solution in THF
precooled to 788C, 11.8 mmol) was added dropwise. This mixture was
allowed to warm to 708C within 1 h and the reaction was quenched by
careful addition of water (20 mL). At 08C 15% aqueous NaOH (10 mL)
and 30% aqueous H2O2 (3.0 mL) were added carefully. After 90 min at 08C
a mixture of sat. aqueous NaHCO3 (60 mL) and MTBE (60 mL) was added.
The aqueous layer was extracted with MTBE (3 Â 40 mL) and the
combined organic layers were washed with sat. aqueous NaCl (50 mL).
After drying with MgSO4 the solvents were removed in vacuo and the
residue was purified by CC (70 g, PE/MTBE 1:1). The title compound was
obtained as a diastereomeric mixture (1.30 g, 81%), ds ꢀ 3:1 according to
the 13C-NMR spectrum. The minor diastereomer could be removed by
fractional crystallization from MTBE. Isomerically pure alcohol 43
(742 mg, 46%) was obtained as white crystals. M.p. 1238C; Rf ˆ 0.22 (PE/
0.738 mmol) in CH2Cl2 (5 mL) and pyridine (1.0 mL) was treated with p-
nitro-benzoyl chloride (405 mg, 1.48 mmol) at 08C. After the addition of
catalytic amounts of DMAP the reaction mixture was allowed to stir for
18 h at room temperature. Water (10 mL) was added followed by extraction
with CH2Cl2 (3 Â 10 mL). The organic layers were washed with 0.5m
aqueous CuSO4 (2 Â 10 mL), half sat. aqueous NaCl (10 mL), and dried
with MgSO4. After removal of the solvent and CC (20 g, MTBE/PE 2:1)
the title compound (348 mg, 85%) was obtained as colorless crystals.
Crystals suitable for X-ray crystal structural analysis were obtained from a
solution of 49 in wet acetone. M.p. 112 ± 1148C (acetone/water); Rf ˆ 0.70
(MTBE/PE 1:1); [a]D
ˆ
3.5, [a]578
ˆ
4.3, [a]546
ˆ
5.0, [a]436
ˆ
7.8;
(c ˆ 0.46, CHCl3, Tˆ 208C); IR (KBr): nÄ ˆ 3370m (NH), 2930m (CH),
ˆ
ˆ
1720s (C O), 1690s (C O), 1610w, 1530m, 1455m, 1385m, 1350m, 1280s,
1170m, 1120m, 1105m, 1015w, 915w, 720w; 1H NMR (300 MHz, CDCl3):
d ˆ 1.42 (s, 9H, tBu), superimposed by 1.35 ± 1.84 (m, 6H, 2-H2, 3-H2, 6-H2),
2.00 ± 2.27 (m, 2H, 7-H2), 3.14 (brs, 2H, 1-H2), 4.03 (m, 1H, 4-H), 4.63 (m,
1H, 5-H), 4.92 ± 5.24 (m, 6H, 9-H2, CH2-Ph, 2NH), 5.78 (m, 1H, 8-H),
7.20 ± 7.42 (m, 5H, Ph), 8.03 ± 8.29 (m, 4H, Ar-NO2); 13C NMR (75 MHz,
CDCl3): d ˆ 27.0, 27.3, 29.1, 29.7 (C-2, C-3, C-6, C-7), 28.3 [C(CH3)3], 39.8
(C-1), 53.3 (C-4), 66.7 (CH2-Ph), 77.1 (C-5), 79.6 [C(CH3)3], 115.7 (C-9),
123.5, 127.9, 128.1, 128.5, 130.7, 135.4, 136.4 (Ar-NO2, Ph), 136.9 (C-8), 156.2
(Boc-CO), 164.3 (CO); C29H37N3O8 (555.62): calcd C 62.69, H 6.71, N 7.56;
found C 62.59, H 6.53, N 7.46.
MTBE 1:1); [a]D
ˆ
16.3, [a]578
ˆ
17.3, [a]546
ˆ
19.7, [a]436
ˆ
33.7,
[a]365
ˆ
51.9 (c ˆ 0.77, CHCl3, Tˆ 208C); IR (KBr): nÄ ˆ 3355/3330s (NH,
ˆ
OH), 2945m/2910w/2870w (CH), 1685s (C O), 1535s, 1365w, 1330m,
1285m, 1170m, 1055m, 1015w, 740w, 695m; 1H NMR (200 MHz, CDCl3):
d ˆ 1.39 (s, 9H, tBu), superimposed by 1.30 ± 1.60 (m, 6H, 2-H2, 3-H2, 6-H2),
1.95 ± 2.35 (m, 2H, 7-H2), 2.87 (brd, J ˆ 5.8 Hz, 1H, OH), 3.04 (brs, 2H,
1-H2), 3.60 (m, 2H, 4-H, 5-H), 4.68 (brt, J ˆ 5.5 Hz, 1H, BocNH), 4.90 ±
5.05 (m, 4H, 9-H2, Ph-CH2), 5.33 (brd, J ˆ 8.8 Hz, 1H, NHZ), 5.78 (m, 1H,
8-H), 7.28 (s, 5H, Ph); 13C NMR (50 MHz, CDCl3): d ˆ 26.1, 26.7 (C-2, C-7),
28.3 [C(CH3)3], 30.2, 32.3 (C-3, C-6), 40.2 (C-1), 55.5 (C-4), 66.7 (Ph-CH2),
73.8 (C-5), 79.1 [C(CH3)3], 115.0 (C-9), 127.98, 128.03, 128.4, 136.3 (Ph),
Crystal data of 49: 0.48  0.20  0.01 mm, monoclinic, P21, a ˆ 19.127 (8),
b ˆ 5.1311 (13), c ˆ 30.102 (11) pm, b ˆ 99.19 (5), Vˆ 2916.3 (18) 10 30 m3,
Z ˆ 4, 1calcd ˆ 1.265 Mgm 3, 2Vmax ˆ 48.008, MoKa, 71.073 pm, f-rotation,
Chem. Eur. J. 2000, 6, No. 4
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677

U. Koert et al.
FULL PAPER
180 K, reflections: measured 15328, independent 9090, LP-correction, no
absorption correction (m ˆ 0.087 mm 1), structure solution by direct
methods (SHELX-97) (Sheldrick 1997), structure refinement by full-
matrix least squares with 9090 F2 data, 698 free parameters, H atoms
geometrically generated and refined with the corresponding C atoms
(riding model), R1 ˆ 0.1224 [2925 reflections with I > 2 s(I)], wR2 ˆ 0.326
(all data), residual electron density: 0.473 to 0.499 Â 1030 em 3. Crystallo-
graphic data (excluding structure factors) for the structure reported in this
paper have been deposited with the Cambridge Crystallographic Data
Centre as supplementary publication no. CCDC-116712. Copies of the data
can be obtained free of charge on application to CCDC, 12 Union Road,
Cambridge CB21EZ, UK (fax: (‡44)1223-336-033; e-mail: deposit@ccdc.
cam.ac.uk).
(epimer B)], 4.47 [dd, J ˆ 7.9, 5.5 Hz, 2-H (epimer A)], 5.08 (brs, 2H, Ph-
CH2), 7.26 ± 7.39 (m, 5H, Ph); 13C NMR (75 MHz, CD3OD): d ˆ 27.5, 28.2,
29.7 (C-4, C-2', C-3'), 28.8 [C(CH3)3], 31.0 (C-3), 40.8 (C-4'), 55.5 (C-1'), 67.4
(Ph-CH2), 78.2, 78.5 [C-2 (two epimers)], 79.8 [C(CH3)3], 84.1, 84.6 [C-5
(two epimers)], 128.7, 128.9, 129.5, 138.5 (Ph), 176.6, 177.0 [COOH (two
epimers)]; C22H32N2O5 (436.50): calcd C 60.54, H 7.39, N 6.42; found C
60.11, H 7.45, N 6.15.
(2S,2'RS,5'R,1''S)-3-[5'-(1''-Benzyloxycarbonylamino-4''-tert-butoxycar-
bonyl-aminobutyl)-tetrahydrofuran-2'-carbamoyl]-2-butylsulfonylamino-
methyl propionate (53): EtN(iPr)2 (1.98 mL, 1.47 g, 11.3 mmol) and EDC
(728 mg, 3.80 mmol) were added subsequently to a solution of carboxylic
acid 51 (1.65 g, 3.78 mmol), trifluoroacetate 52 (1.73 g, 4.90 mmol), and
HOBt (868 mg, 5.70 mmol) in THF (15 mL). After the solution was stirred
at room temperature for 18 h, the solvent was removed in vacuo, and the
residue dissolved in EtOAc (50 mL). After successive washings with 5%
aqueous citric acid (2 Â 10 mL), sat. aqueous NaHCO3 (20 mL), and sat.
aqueous NaCl (20 mL) the organic layer was dried with Na2SO4. Removal
of the solvent in vacuo and CC (200 g, MTBE/PE 5:1) afforded amide 53
(1.51 g, 61%) as a white solid. M.p. 57 ± 588C; Rf ˆ 0.52 (MTBE); HPLC:
tR ˆ 13.7 min (Si 60; 1.5 mLmin 1, 10% isopropyl alcohol in n-hexane);
14.5 and 15.3 min (Rainin, RP 18, 1 mLmin 1, 40% to 80% B within
20 min, A: water‡ 0.2% TFA; B: acetonitrile ‡ 0.2% TFA); IR (KBr):
(2RS,5R,1'S)-5-(1'-Benzyloxycarbonylamino-4'-tert-butoxycarbonylami-
no-butyl)-2-hydroxymethylene-tetrahydrofuran (50):
A
solution of
MCPBA (60%, 1.06 g, 3.7 mmol) in CH2Cl2 (15 mL) was added within
10 min to a solution of alcohol 43 (715 mg, 1.76 mmol) in CH2Cl2 (15 mL).
After stirring at room temperature for 3.5 h the reaction mixture was
poored on sat. aqueous Na2SO3 (15 mL). The layers were separated and the
aqueous layer was extracted with CH2Cl2 (2 Â 20 mL). The combined
organic layers were washed with sat. aqueous NaHCO3 (15 mL) and sat.
aqueous NaCl (50 mL). The solvents were removed in vacuo after drying
with MgSO4 and the residual oil was dissolved in CH2Cl2 (10 mL) and
treated with PPTS (20 mg). After 12 h sat. aqueous NaHCO3 (15 mL) was
added. The layers were separated and the aqueous layer was extracted with
CH2Cl2 (2 Â 20 mL). The combined organic layers were washed with sat.
aqueous NaCl (30 mL). After the organic phase was dried with Na2SO4, the
solvent was removed in vacuo and the residue was purified by CC [50 g, PE/
MTBE 1:2 (400 mL), then MTBE]. Compound 50 (670 mg, 90%) was
obtained as a white foam. The diasteromeric ratio was approx. 1:1 as
ˆ
nÄ ˆ 3420brs (NH), 2960m/2875w (CH), 1685brs (C O), 1525w, 1455m,
1425s, 1365m, 1330m, 1250w, 1215m, 1150m, 1080w; 1H NMR (300 MHz,
CD3OD): d ˆ 0.95, 0.96 (2t, J ˆ 7.3 Hz each, 3H, CH3), 1.43 (s, 9H, tBu),
superimposed by 1.28 ± 1.97 (m, 9H, 2CH2CH2, 4'-HA), 1.88 ± 2.07 (m, 2H,
3'-HA, 4'-HB) 2.16 ± 2.36 (m, 1H, 3'-HB), 3.04 (m, 4H, 4''-H2, SO2CH2), 3.75
(s, 3H, OMe), superimposed by 3.26 ± 3.86 (m, 3H, 3-H2, 1''-H), 3.96 [ddd,
all Jvic ꢀ 6.0 Hz, 5'-H (one epimer)], 4.08 [ddd, all Jvic ˆ 6.5 Hz, 5'-H (one
epimer)], 4.21 ± 4.37 (m, 2H, 2-H, 2'-H), 5.03 ± 5.17 (m, 2H, PhCH2), 7.23 ±
7.43 (m, 5H, Ph); 13C NMR (75 MHz, CD3OD): d ˆ 14.0 (CH3), 22.5, 26.7,
27.7, 28.1, 29.7, 29.9, 30.9, 31.2 (2CH2CH2, C-3', C-4'), 28.8 [C(CH3)3], 41.2,
41.4, 42.0 (C-3, C-4''), 53.2 (OMe), 54.2 (SO2CH2), 55.2, 55.4 [C-1'' (two
epimers)], 56.6, 56.7 [C-2 (two epimers)], 67.4 (CH2-Ph), 79.8 [C-2',
C(CH3)3], 84.3, 84.8 [C-5' (two epimers)], 128.6, 128.7, 129.0, 129.5, 138.0
(Ph), 158.5, 159.1 (Z-CO, Boc-CO), 172.2 (CONH), 176.1, 176.5 [COO (two
epimers)]; C30H48N4O10S (656.79): calcd C 54.86, H 7.37, N 8.53, S 4.88;
determined by 13C NMR. M.p. 808C; Rf ˆ 0.30 (MTBE); [a]D
ˆ
15.6,
42.3 (c ˆ 1.48,
[a]578
ˆ
16.2, [a]546
ˆ
18.4, [a]436
ˆ
29.7, [a]365
ˆ
CHCl3, Tˆ 208C); IR (KBr): nÄ ˆ 3360m (NH, OH), 3035w (ArH),
ˆ
2960m/2940m/2875w (CH), 1685s (C O), 1530s, 1455w, 1365w, 1280m,
1240m, 1175m, 1085w, 1045m, 1020w, 695w; H NMR (300 MHz, CDCl3):
1
d ˆ 1.43 (s, 9H, tBu), superimposed by 1.20 ± 1.78, 1.80 ± 2.05 (m, 6H; m,
2H, 3-H2, 4-H2, 2'-H2, 3'-H2), 2.61 (brs, 1H, OH), 3.11 (m, 2H, 4'-H2), 3.45
(dd, J ˆ 11.7, 6.0 Hz, 1H, 1''-HA), 3.62 [dd, J ˆ 12.4, 3.2 Hz, ca. 0.5H, 1''-HB
(one epimer)], superimposed partially by 3.65 [dd, J ˆ 11.9, 3.2 Hz, 1''-HB
(one epimer)], superimposed by 3.62 ± 3.78 (m, 1H, 1'-H), 3.83 ± 4.07 (m,
2H, 2-H, 5-H), 4.70 (m, 1H, NH), 5.08 (s, 2H, Ph-CH2), superimposed by
5.02 ± 5.13 (m, 1H, NH), 7.26 ± 7.40 (m, 5H, Ph); 13C NMR (75 MHz,
CDCl3): d ˆ 26.6 (br), 26.8, 27.2, 27.9, 28.5 (C-3, C-4, C-2', C-3'), 28.3
[C(CH3)3], 40.2 (C-4'), 54.0, 54.3 [C-1' (two epimers)], 64.7, 64.9 [C-1'' (two
epimers)], 66.7 (Ph-CH2), 79.1 [C(CH3)3], 80.0, 81.7, 82.0 [C-2, C-5 (two
‡
found C 55.23, H 7.44, N 8.04, S 4.55; HRMS (FAB): [C30H48N4O10S‡H]
calcd 657.3169; found 657.337.
(2S,2'R,5'R,1''S)-3-[5'-(1''-Benzyloxycarbonylamino-4''-[N2''',N3'''-bis-
(tert-butoxycarbonyl)-guanidino]-butyl)-tetrahydrofuran-2'-carbamoyl]-2-
butylsulfonyl-amino-methyl propionate (55) and (2S,2'S,5'R,1''S)-3-[5'-(1''-
benzyloxy-carbonylamino-4''-[N2''',N3'''-bis-(tert-butoxycarbonyl)-guanidi-
no]-butyl)-tetrahydrofuran-2'-carbamoyl]-2-butylsulfonylamino
methyl
propionate (56): A solution of protected amine 53 (480 mg, 0.731 mmol)
in CH2Cl2 (15 mL) was treated with TFA (3 mL). After 4 h at room
temperature the solvents were removed under reduced pressure. Azeo-
tropic distillation with toluene (2 Â 5 mL) yielded a slightly brownish oil
which was used without further purification in the guanylation. This
residue, isothiourea 54 (233 mg, 0.800 mmol), and NEt3 (0.41 mL, 0.30 g,
2.9 mmol) were dissolved in DMF (7 mL). After addition of HgCl2 (228 mg,
0.840 mmol) the reaction mixture was stirred for 2.5 h at room temperature.
It was diluted with EtOAc (30 mL) and filtered with the aid of Celite. The
filtrate was washed with 5% aqueous citric acid (2 Â 7 mL), sat. aqueous
NaHCO3 (7 mL), sat. aqueous NaCl (7 mL). The organic phase was dried
with Na2SO4. Removal of the solvents in vacuo and subsequent CC (60 g,
MTBE) afforded the guanidine derivatives 55/56 (395 mg, 68% based on
53) as a colorless solid. This approx. 2:1 mixture of C-2'-epimers was
separated by preparative HPLC (6 runs, 21 mm ID, Rainin, Si 60,
21.6 mLmin 1, 15% isopropyl alcohol in n-hexane). In addition to the
diastereomerically pure 56 (220 mg, 0.275 mmol, 38%)* and 55 (75 mg,
0.094 mmol, 13%)* an epimeric mixture (50 mg, 0.063 mmol, 9%) was
obtained; *the cis vs. trans assignment was done unambiguously by
interpretation of 600 MHz NOESY spectra of both separated epimers after
transformation to 38 and 39 (see below). Analytical data of the epimeric
mixture: Rf ˆ 0.32 (MTBE); IR (KBr): nÄ ˆ 3335w (NH), 2960w (CH), 1720s
(CO), 1640s, 1530w, 1455w, 1415w, 1370m, 1330s, 1230w, 1135s, 1055w,
1025w; C36H58N6O12S (798.94): calcd C 54.12, H 7.32, N 10.52, S 4.01; found
C 54.01, H 7.61, N 9.99, S 3.57. Guanidine derivative 55: m.p. 67 ± 688C;
ˆ
epimers)], 128.0, 128.4, 136.4 (Ph), 156.0, 156.4, 156.5 [Boc-, Z-C O (two
epimers)]; C22H34N2O6 (422.52): calcd C 62.54, H 8.11, N 6.63; found C
62.32, H 8.21, N 6.49.
(2RS,5R,1'S)-5-(1'-Benzyloxycarbonylamino-4'-tert-butoxycarbonylami-
no-butyl)-tetrahydrofuran-2-carboxylic acid (51): Starting from the alcohol
50 (3.58 g, 8.47 mmol) this two-step oxidation was performed analogous to
the preparation of the carboxylic acids 25/26. The following amounts of
reagents were used: oxalyl chloride (1.45 mL, 2.14 g, 16.9 mmol) in CH2Cl2
(60 mL), DMSO (1.80 mL, 1.98 g, 25.4 mmol) in CH2Cl2 (10 mL), and NEt3
(14.1 mL, 10.3 g, 101 mmol). Without purification by CC the corresponding
crude aldehyde (3.65 g) was obtained as a yellow oil. Rf ˆ0.38 (MTBE).
Subsequent Pinnick-oxidation using t-BuOH (12 mL), amylene (6 mL),
NaClO2 (80%, 1.24 g, 11.0 mmol) and NaH2PO4 Â H2O (1.51 g, 11.0 mmol)
in water (6 mL) yielded a slightly yellow crude product after usual work-up.
This was further purified as the dicyclohexyl ammonium salt analogous to
the preparation of carboxylic acids 25/26 using dicyclohexyl amine
(2.49 mL, 2.27 g, 12.5 mmol). After liberation of the free acids with the
aid of 5% aqueous citric acid (2 Â 100 mL) instead of aqueous HCl, the
acid 51 (3.37 g, 64%) was obtained as an epimeric mixture. M.p. 69 ± 748C;
Rf ˆ 0.05 ± 0.24 (MTBE); IR (KBr): nÄ ˆ 3345brm (NH, COOH), 3035w
ˆ
(ArH), 2975m/2935m (CH), 1695s (C O), 1635m, 1530s, 1455m, 1390w,
1365m, 1340m, 1250m, 1170m, 1080m, 1015w, 740w, 700w; 1H NMR
(300 MHz, CD3OD): d ˆ 1.42 (s, 9H, tBu), superimposed by 1.27 ± 2.12 (m,
7H, 3-HA, 4-H2, 2'-H2, 3'-H2), 2.18 ± 2.36 (m, 1H, 3-HB), 2.99 ± 3.09 (m, 2H,
4'-H2), 3.54 ± 3.71 (m, 1H, 1'-H), 3.89 [dt, J ˆ 7.0, 7.0 Hz, 5-H (epimer A)],
4.04 [dt, J ˆ 6.8, 6.8 Hz, 5-H (epimer B)], 4.42 [dd, J ˆ 8.0, 5.9 Hz, 2-H
[a]D ˆ ‡12.6, [a]578 ˆ ‡13.5, [a]546 ˆ ‡15.7, [a]436 ˆ ‡29.2, [a]365 ˆ ‡52.0
1
(c ˆ 0.65, CHCl3, Tˆ 208C); HPLC: tR ˆ 15.6 min (Si 60; 1.5 mLmin
,
678
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
0947-6539/00/0604-0678 $ 17.50+.50/0
Chem. Eur. J. 2000, 6, No. 4

Integrin Antagonists
666±683
15% isopropyl alcohol in n-hexane); 1H NMR (300 MHz, CD3OD): d ˆ
0.95 (t, J ˆ 7.4 Hz, 3H, CH3), 1.46, 1.52 (2s, 18H, 2tBu), superimposed by
1.22 ± 1.90 (m, 9H, 2CH2CH2, 4'-HA), 1.90 ± 2.07 (m, 2H, 3'-HA, 4'-HB)
2.20 ± 2.36 (m, 1H, 3'-HB), 3.04 (t, J ˆ 7.9 Hz, 2H, SO2CH2), 3.25 ± 3.43 (m,
3H, 3-HA, 4''-H2), 3.75 (s, 3H, OMe), superimposed by 3.62 ± 3.79 (m, 2H,
3-HB, 1''-H), 4.09 (ddd, all Jvic ˆ 6.5 Hz, 1H, 5'-H), 4.23 (dd, J ˆ 8.3, 5.3 Hz,
1H, 2-H), 4.35 (dd, J ˆ 7.9, 6.0 Hz, 1H, 2'-H), 5.09 (s, 2H, Ph-CH2), 7.22 ±
7.40 (m, 5H, Ph); 13C NMR (75 MHz, CD3OD): d ˆ 14.0 (CH3), 22.5, 26.7,
26.9, 29.4 (2CH2CH2), 28.2 (C-4'), 28.3, 28.6 [2C(CH3)3], 30.9 (C-3'), 41.6,
41.9 (C-3, C-4''), 53.1 (OMe), 54.2 (SO2CH2), 55.1 (C-1''), 56.6 (C-2), 67.4
(CH2-Ph), 79.8, 84.2 [2C(CH3)3], 80.3 (C-2'), 84.4 (C-5'), 128.7, 128.9, 129.4,
1H, N4''H); the sample still contained 6 mass-% water which was explicit
substracted from the yield; due to recording the spectrum with presatura-
tion of the HOD signal the integral size of some exchangeable protons was
too small; 13C NMR (75 MHz, CD3CN): d ˆ 13.9 (CH3), 21.4 (CH2-CH3),
25.7 (C-3''), 26.3 (SO2CH2-CH2), 27.7 (C-4'), 29.0 (C-2''), 30.8 (C-3'), 42.0,
42.1 (C-3, C-4''), 53.6 (SO2CH2), 54.9 (C-1''), 56.4 (C-2), 67.2 (CH2-Ph), 79.6
ˆ
(C-2'), 84.1 (C-5'), 128.5, 128.9, 129.5, 138.1 (Ph), 158.1 (presumably C N),
175.0 (COO); some CO-signals were not detected. FAB-MS:
‡
[C25H41N6O8S] calcd 585.3; found 585.5.
(2S,2'R,5'R,1''S)-3-[5'-(1''-Benzyloxycarbonylamino-4''-tert-butoxycarbon-
yl-aminobutyl)-tetrahydrofuran-2'-carbamoyl]-2-benzyloxycarbonylami-
no-methyl propionate (57): The preparation was done analogous to the
amide 53 using the following amounts of substrate and reagents: carboxylic
acid 51 (535 mg, 1.23 mmol), amine hydrochloride 27 (391 mg, 1.35 mmol),
HOBt (282 mg, 1.84 mmol), EtN(iPr)2 (0.47 mL, 0.35 g, 2.7 mmol), and
EDC (236 mg, 1.23 mmol). CC (100 g, EtOAc/PE 1:1) yielded the product
(651 mg, 79%) as a mixture of C-2'-epimers. Crystallization from Et2O
(40 mL) afforded the pure trans-isomer 57 (302 mg, 0.450 mmol, 37%) as a
white solid. M.p. 1048C; Rf ˆ 0.74 (EtOAc); [a]D ˆ ‡10.4, [a]578 ˆ ‡11.3,
[a]546 ˆ ‡13.3, [a]436 ˆ ‡25.2, [a]365 ˆ ‡48.9 (c ˆ 0.89, CHCl3, Tˆ 208C);
ˆ
138.5 (Ph), 154.2 (C N), 157.6, 159.0 (Z-CO, Boc-CO), 164.6 (Boc-CO),
172.2 (CONH), 176.5 (COO). Guanidine derivative 56: m.p. 598C; [a]D
ˆ
‡6.9, [a]578 ˆ ‡7.2, [a]546 ˆ ‡8.1, [a]436 ˆ ‡16.7, [a]365 ˆ ‡30.4 (c ˆ 0.90,
1
CHCl3, Tˆ 208C); HPLC: tR ˆ 12.5 min (Si 60; 1.5 mLmin
,
15%
isopropyl alcohol in n-hexane); 1H NMR (300 MHz, CD3OD): d ˆ 0.94
(t, J ˆ 7.3 Hz, 3H, CH3), 1.47 and 1.53 (2s, 18H, 2tBu), superimposed by
1.21 ± 1.85 (m, 9H, 2CH2CH2, 4'-HA), 1.95 (m, 2H, 3'-HA, 4'-HB) 2.23 (m,
1H, 3'-HB), 3.04 (t, J ˆ 7.9 Hz, 2H, SO2CH2), 3.31 ± 3.61 (m, 4H, 3-H2, 4''-
H2), 3.74 (s, 3H, OMe), 3.75 ± 3.86 (m, 1H, 1''-H), 3.91 ± 4.02 (m, 1H, 5'-H),
4.20 ± 4.23 (m, 2H, 2-H, 2'-H), 5.05 ± 5.18 (m, 2H, Ph-CH2), 7.22 ± 7.42 (m,
5H, Ph); 13C NMR (75 MHz, CD3OD): d ˆ 14.0 (CH3), 22.5, 26.6, 27.0, 29.7
(2CH2CH2), 27.7 (C-4'), 28.3, 28.6 [2C(CH3)3], 31.2 (C-3'), 41.5, 41.9 (C-3,
C-4''), 53.2 (OMe), 54.2 (SO2CH2), 55.5 (C-1''), 56.5 (C-2), 67.4 (CH2-Ph),
79.8, 84.7 [2C(CH3)3], 80.3 (C-2'), 84.4 (C-5'), 128.5, 128.9, 129.5, 138.0
ˆ
IR (KBr): nÄ ˆ 3335brm (NH), 2950w/2935m (CH), 1705s (C O), 1685s
1
ˆ
(C O), 1530s, 1435m, 1365w, 1340w, 1250m, 1170w, 1070w, 700w; H NMR
(300 MHz, CD3OD): d ˆ 1.42 (s, 9H, tBu), superimposed by 1.24 ± 1.97 (m,
7H, 3'-HA, 4'-H2, 2''-H2, 3''-H2), 2.16 ± 2.33 (m, 1H, 3'-HB), 3.01 (brt, J ˆ
6.4 Hz, 2H, 4''-H2), 3.46 (dd, J ˆ 13.7, 7.4 Hz, 1H, 3-HA), 3.72 (s, 3H, OMe),
superimposed by 3.58 ± 3.75 (m, 2H, 3-HB, 1''-H), 3.98 (dt, J ˆ 6.5, 6.5 Hz,
1H, 5'-H), 4.31 (dd, J ˆ 7.5, 6.2 Hz, 1H, 2'-H), 4.38 (dd, J ˆ 7.3, 5.2 Hz, 1H,
2-H), 5.02 ± 5.15 (m, 4H, 2Ph-CH2), 7.23 ± 7.39 (m, 10H, 2Ph); 13C NMR
(75 MHz, CD3OD): d ˆ 27.6, 28.0, 29.3 (C-4', C-2'', C-3''), 28.8 [C(CH3)3],
31.0 (C-3'), 41.0 (C-3, C-4''), 53.0 (OMe), 55.0 (C-1''), 55.3 (C-2), 67.4, 67.8
(2CH2-Ph), 79.8 [C-2', C(CH3)3], 84.3 (C-5'), 128.7, 128.9, 129.0, 129.5,
138.0, 138.4 (2Ph), 158.4, 159.0 (2Z-CO, Boc-CO), 172.4 (CONH), 176.6
(COO); C34H46N4O10 (670.75): calcd C 60.88, H 6.91, N 8.35; found C 60.93,
H 7.00, N 8.18. Epimeric mixture (strongly enriched by the cis isomer):
1H NMR (300 MHz, CD3OD): d ˆ 1.41 (s, 9H, tBu), superimposed by
1.23 ± 1.95 (m, 7H, 3'-HA, 4'-H2, 2''-H2, 3''-H2), 2.11 ± 2.30 (m, 1H, 3'-HB),
2.90 ± 3.14 (m, 2H, 4''-H2), 3.40 ± 3.80 (m, 3H, 3-H2, 1''-H), 3.70 (s, 3H,
OMe), 3.85 ± 4.02 (m, 1H, 5'-H), 4.23 (m, 1H, 2'-H), 4.30 ± 4.44 (m, 1H,
2-H), 5.02 ± 5.17 (m, 4H, 2Ph-CH2), 7.20 ± 7.39 (m, 10H, 2Ph); 13C NMR
(75 MHz, CD3OD): d ˆ 27.7 (double intensity), 29.7, 31.4 (C-3', C-4', C-2'',
C-3''), 28.9 [C(CH3)3], 40.9 (C-3, C-4''), 53.1 (OMe), 55.3 (C-2, C-1''), 67.5,
67.9 (2CH2-Ph), 79.8 [C(CH3)3], 79.9 (C-2'), 84.9 (C-5'), 128.7, 128.9, 129.0,
129.1, 129.5, 138.1, 138.5 (2Ph), 158.4, 158.6 (2Z-CO, Boc-CO), 172.3
(CONH), 176.1 (COO).
ˆ
(Ph), 154.1 (C N), 158.0, 159.3 (Z-CO, Boc-CO), 164.5 (Boc-CO), 172.1
(CONH), 176.9 (COO).
(2S,2'R,5'R,1''S)-3-[5'-(1''-Benzyloxycarbonylamino-4''-guanidino-butyl)-
tetrahydrofuran-2'-carbamoyl]-2-butylsulfonylamino propionic acid (38, as
trifluoroacetate): The preparation was done as described for 14 starting
from THF derivative 55 (42 mg, 0.052 mmol). Purification by preparative
HPLC [3 runs, 21 mm ID, Rainin, RP 18, 21.6 mLmin 1, 70% (water‡
0.2% TFA) and 30% (acetonitrile ‡ 0.2% TFA)] yielded trifluoroacetate
38 (16 mg, 43%) as a colorless oil; HPLC: tR ˆ 6.7 min (MN, RP 18,
1 mLmin 1, 1% to 40% B within 20 min, A: water‡ 0.2% TFA; B:
acetonitrile ‡ 0.2% TFA); tR ˆ 17.3 min (MN, RP 18, 1 mLmin 1, 20% to
80% B within 20 min, A: water ‡ 0.2% TFA; B: acetonitrile ‡ 0.2% TFA);
1H NMR (600 MHz, CD3CN): d ˆ 0.91 (t, J ˆ 7.4 Hz, 3H, CH3), 1.40 (m,
3H, 2''-HA, CH2-CH3), 1.49 ± 1.60 (m, 1H, 3''-HA), 1.60 ± 1.78 (m, 5H, 4'-HA,
2''-HB, 3''-HB, SO2CH2-CH2), 1.89 ± 1.97 (m, 2H, 3'-HA, 4'-HB), 2.18 ± 2.29
(m, 1H, 3'-HB), 3.03 (t, J ˆ 6.4 Hz, 2H, SO2CH2), 3.06 ± 3.14, 3.12 ± 3.22
(2m, 1H each, 4''-H2), 3.39 (ddd, J ˆ 13.2, 6.6, 6.6 Hz, 1H, 3-HA), 3.59 ± 3.69
(m, 2H, 3-HB, 1''-H), 3.99 (m, 1H, 5'-H), 4.13 (m, 1H, 2-H), 4.34 (m, 1H, 2'-
H), 5.07 (s, 2H, PhCH2), 5.78 (d, J ˆ 9.7 Hz, 0.6H, NHZ), 6.02 (d, J ˆ
8.3 Hz, NHSO2), 6.36 (brs, 1.8H, 2NH2), 7.08 (brs, N4''H), 7.29 ± 7.38 (m,
5H, Ph), 7.40 (m, N3H); the sample still contained 13 mass-% water which
was explicit substracted from the yield; due to recording the spectrum with
presaturation of the HOD signal the integral size of some exchangeable
protons is too small; in addition a second conformer/epimer (approx.
10 mol-%) was detected, but these signals were not reported above;
13C NMR (75 MHz, CD3CN): d ˆ 14.0 (CH3), 22.2 (CH2-CH3), 25.4 (C-3''),
26.4 (SO2CH2-CH2), 28.5 (C-4'), 29.3 (C-2''), 30.7 (C-3'), 42.2 (C-3, C-4''),
53.8 (SO2CH2), 54.8 (C-1''), 56.0 (C-2), 67.2 (CH2-Ph), 79.6 (C-2'), 83.7 (C-
(2S,2'R,5'R,1''S)-3-[5'-(1''-Benzyloxycarbonylamino-4''-[N2''',N3'''-bis-(tert-
butoxycarbonyl)-guanidino]-butyl)-tetrahydrofuran-2'-carbamoyl]-2-ben-
zyloxy-carbonylamino methyl propionate (58): The preparation was done
analogous to the preparation of the guanidine derivatives 55/56 using the
following amounts of substrate and reagents: Boc-protected amine 57
(104 mg, 0.155 mmol), TFA (1 mL), then isothiourea 54 (48 mg, 0.17 mmol),
NEt3 (0.10 mL, 73 mg, 0.72 mmol) and HgCl2 (46 mg, 0.17 mmol). CC (15 g,
MTBE) yielded the guanidine derivative 58 (92 mg, 0.11 mmol, 73%) as a
colorless solid. M.p. 68 ± 698C; Rf ˆ 0.40 (MTBE); [a]D ˆ ‡16.9, [a]578
ˆ
ˆ
5'), 128.6, 129.0, 129.6 (Ph), 158.1 (presumably C N); the CO-signals as
well as the signal for Cq of Ph were not detected. FAB-MS: [C25H41N6O8S]
‡17.7, [a]546 ˆ ‡20.0, [a]436 ˆ ‡36.3, [a]365 ˆ ‡62.1 (c ˆ 0.70, CHCl3, Tˆ
‡
ˆ
208C); IR (KBr): nÄ ˆ 3335brm (NH), 2950w/2930w (CH), 1720s (C O),
calcd 585.3; found 585.4.
1640s, 1525m, 1455m, 1415m, 1370m, 1335m, 1230m, 1155m, 1135m, 1055m,
700w; 1H NMR (300 MHz, CDCl3): d ˆ 1.47, 1.49 (2s, 18H, 2tBu), 1.30 ±
2.08 (m, 7H, 3'-HA, 4'-H2, 2''-H2, 3''-H2), 2.22 ± 2.39 (m, 1H, 3'-HB), 3.27 ±
3.41, 3.44 ± 3.60, 3.61 ± 3.80 (3m, 1H, 2H, 2H, 3-H2, 1''-H, 4''-H2), 3.73 (s,
3H, OMe), 3.94 (ddd, all Jvic ꢀ 6.0 Hz, 1H, 5'-H), 4.34 (dd, J ˆ 6.9, 6.9 Hz,
1H, 2'-H), 4.44 (m, 1H, 2'-H), 5.09 (m, 4H, 2CH2-Ph), 5.53 (d, J ˆ 7.4 Hz,
1H, NHZ), 6.06 (d, J ˆ 7.2 Hz, 1H, NHZ), 7.15 (brs, 1H, N3H), 7.22 ± 7.30
(m, 10H, 2Ph), 8.34 (brs, 1H, N1'''H), 11.49 (s, 1H, NHBoc); 13C NMR
(75 MHz, CDCl3): d ˆ 25.9, 27.3, 27.6, 29.3 (C-3', C-4', C-2'', C-3''), 28.1
[C(CH3)3], 40.3, 40.8 (C-3, C-4''), 52.6 (OMe), 53.9, 54.5 (C-2, C-1''), 66.6,
66.9 (2CH2-Ph), 78.7, 79.1 [C-2', C(CH3)3], 82.9, 83.0 [C-5', C(CH3)3], 127.9,
(2S,2'S,5'R,1''S)-3-[5'-(1''-Benzyloxycarbonylamino-4''-guanidino-butyl)-
tetrahydrofuran-2'-carbamoyl]-2-butylsulfonylamino propionic acid (39, as
a trifluoroacetate): The preparation and purification was done as described
for 38 starting from THF derivative 56 (73 mg, 0.091 mmol) and afforded 39
(42 mg, 66%) as a colorless oil. HPLC: tR ˆ 16.7 min (Rainin, RP 18,
1 mLmin 1, 20% to 60% B within 30 min, A: water‡ 0.2% TFA; B:
acetonitrile ‡ 0.2% TFA); 1H NMR (600 MHz, CD3CN): d ˆ 0.89 (t, J ˆ
7.4 Hz, 3H, CH3), 1.32 ± 1.42 (m, 3H, 2''-HA, CH2-CH3), 1.49 ± 1.59 (m, 1H,
3''-HA), 1.59 ± 1.76 (m, 5H, 4'-HA, 2''-HB, 3''-HB, SO2CH2-CH2), 1.86 ± 1.93
(m, 2H, 3'-HA, 4'-HB) 2.19 (m, 1H, 3'-HB), 3.01 (t, J ˆ 8.0 Hz, 2H, SO2CH2),
3.06 ± 3.13, 3.11 ± 3.21 (2m, 1H each, 4''-H2), 3.48 (m, 2H, 3-H2), 3.69 (m,
1H, 1''-H), 3.92 (m, 1H, 5'-H), 4.13 (m, 1H, 2-H), 4.28 (m, 1H, 2'-H), AB
signal (dA ˆ 5.06, dB ˆ 5.09, JAB ˆ 12.6 Hz, 2H, Ph-CH2), 6.10 (d, J ˆ 9.2 Hz,
0.7H, NHZ), 6.17 (d, J ˆ 8.7 Hz, 0.7H, NHSO2), 6.47, 6.57 (2brs, 3H,
2NH2), 7.28 ± 7.37 (m, 5H, Ph), 7.39 (brt, J ˆ 5.9 Hz, 1H, N3H), 7.43 (brs,
ˆ
128.0, 128.4, 136.0, 136.4 (2Ph), 156.1, 156.3, 156.4 (2Z-CO, Boc-CO, C N),
163.3 (Boc-CO), 170.5 (CONH), 174.1 (COO); C40H56N6O12 (812.91): calcd
C 59.10, H 6.94, N 10.34; found C 58.86, H 7.47, N 10.11.
(2S,2'R,5'R,1''S)-3-[5'-(1''-Benzyloxycarbonylamino-4''-guanidino-butyl)-
tetrahydrofuran-2'-carbamoyl]-2-benzyloxycarbonylamino propionic acid
Chem. Eur. J. 2000, 6, No. 4
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
0947-6539/00/0604-0679 $ 17.50+.50/0
679

U. Koert et al.
FULL PAPER
(40, as trifluoroacetate): The preparation and purification was done as
described for 38. Starting from THF derivative 58 (35 mg, 0.043 mmol) 40
(14 mg, 46%) was obtained as a white solid after lyophylization. HPLC:
tR ˆ 19.5 min (Rainin, RP 18, 1 mLmin 1, 20% to 60% B within 30 min, A:
water‡ 0.2% TFA; B: acetonitrile ‡ 0.2% TFA); 1H NMR (300 MHz,
CD3CN): d ˆ 1.34 ± 1.76 (m, 5H, 2''-H2, 3''-H2, 4'-HA), 1.80 ± 1.92 (m, 2H, 3'-
HA, 4'-HB), 2.15 ± 2.27 (m, 1H, 3'-HB), 3.05 ± 3.17 (m, 2H, 4''-H2)*, 3.43
(ddd, J ˆ 13.4, 6.6, 6.6 Hz, 1H, 3-HA), 3.51 ± 3.69 (m, 2H, 3-HB, 1''-H),
3.85 ± 3.95 (m, 1H, 5'-H), 4.23 ± 4.33 (m, 2H, 2-H, 2'-H), 5.06 (s, 4H, 2Ph-
CH2), 5.83 (d, J ˆ 9.4 Hz, 1H, NHZ), 6.39 (d, J ˆ 7.5 Hz, 1H, NHZ), 6.63
(brs, 4H, 2NH2), 7.26 ± 7.42 (m, 11H, 2 Â Ph, NH), 7.60 (m, 1H, NH); the
sample still contained approx. 10 mass-% water which was explicit
substracted from the yield; *this signal was superimposed by the HOD
signal. 13C NMR (75 MHz, CD3CN): d ˆ 25.5, 28.4, 29.3, 30.6 (C-3', C-4',
C-2'', C-3''), 41.4, 42.0 (C-3, C-4''), 54.4 (C-2, C-1''), 66.9, 67.2 (2CH2-Ph),
(EtOAc); [a]D
ˆ
7.1, [a]578
ˆ
7.3, [a]546
ˆ
8.3, [a]436
ˆ
13.9, [a]365
ˆ
19.8 (c ˆ 1.02, CHCl3, Tˆ 208C); IR (KBr): nÄ ˆ 3400brs, 2980w (CH),
1720s (COOR), 1665s, 1525s, 1455w, 1400s, 1370m, 1250m, 1230m, 1170m,
1050w, 700w; H NMR (300 MHz, CDCl3): d ˆ 1.17 (d, J ˆ 6.8 Hz, 3H, 2''-
1
H3), 1.44 (s, 9H, tBu), 1.52 ± 1.67 (m, 1H, 4'-HA), 1.80 ± 2.02 (m, 2H, 3'-HA,
4'-HB), 2.31 (m, 1H, 3'-HB), 3.46 ± 3.60 (m, 1H, 3-HA), 3.52 ± 3.82 (m, 7H,
3-HB, 5'-H, 2'''-H2, OCH3), 4.07 (m, 1H, 1''-H), 4.37 (t, J ˆ 7.3 Hz, 1H, 2'-
H), 4.51 (m, 1H, 2-H), 5.12 (s, 2H, CH2-Ph), 5.30 (brs, NHBoc), 6.05 (brd,
J ˆ 7.2 Hz, 1H, NHZ), 6.44 (brd, J ˆ 8.5 Hz, 1H, N1''H), 7.22 (brs, 1H,
N3H), 7.28 ± 7.40 (m, 5H, Ph); 13C NMR (75 MHz, CDCl3): d ˆ 18.3 (C-2''),
28.2 [C(CH3)3], 28.6 (C-4'), 29.8 (C-3'), 41.0 (C-3), 44.5 (brC-2'''), 47.7 (C-
1''), 52.8 (OCH3), 54.2 (C-2), 67.1 (CH2-Ph), 78.3 (C-2'), 80.3 [C(CH3)3],
83.0 (C-5'), 127.9, 128.3, 128.5, 135.9 (Ph), 156.3 (Z-CO, Boc-CO), 169.3,
170.6 (2CONH), 173.9 (COO); C26H38N4O9 (550.60): calcd C 56.72, H 6.96,
N 10.18; found C 56.20, H 7.22, N 10.40.
ˆ
79.5 (C-2'), 83.6 (C-5'), 128.5, 128.9, 129.0, 129.5 (Ph), 157.9 and 158.4 (C N
{2'''-Guanidino-acetyl}-{(2'S,5'S,1''S)-5'-(1''-amino-ethyl)-tetrahydrofuran-
2'-carbonyl}-{(2S)-3-amino-2-benzyloxycarbonylamino propionic acid} (59,
as trifluoroacetate) via guanylation and deprotection: The guanylation was
done analogous to the guanidine derivatives 55/56 using the following
amounts of substrate and reagents: Boc-protected amine 67 (523 mg,
0.950 mmol), TFA (3 mL); then isothiourea 54 (296 mg, 1.02 mmol), NEt3
(0.40 mL, 0.29 g, 2.9 mmol), and HgCl2 (290 mg, 1.07 mmol). CC (2 Â 40 g,
EtOAc) gave the corresponding guanidine derivative (615 mg, 93% based
and Z-CO), 173.0 and 175.5; some CO-signals as well as the signal for Cq of
‡
Ph were not detected; HRMS (FAB): [C29H39N6O8] calcd 599.2829; found
599.2865.
(2S,2'S,5'S,1''S)-2-Benzyloxycarbonylamino-3-[5'-(1''-tert-butoxycarbonyl-
aminoethyl)-tetrahydrofuran-2'-carbamoyl] methyl propionate (64): The
preparation was done analogous to amide 53 using the following amounts
of substrate and reagents: carboxylic acid 63 (1.00 g, 3.86 mmol), amine
hydrochloride 27 (1.10 g, 4.24 mmol), HOBt (886 mg, 5.78 mmol), Et-
N(iPr)2 (0.74 mL, 0.55 g, 4.2 mmol), and EDC (799 mg, 4.17 mmol). The
amide 64 (1.54 g, 81%) was obtained as a white foam. M.p. 538C; Rf ˆ 0.44
on 67) as a white solid. M.p. 90 ± 928C; Rf ˆ 0.32 (EtOAc); [a]D
ˆ
6.4,
[a]578 6.6, [a]546 7.6, [a]436 12.7, [a]365
ˆ
ˆ
ˆ
ˆ
17.2 (c ˆ 0.86, CHCl3,
Tˆ 208C); IR (KBr): nÄ ˆ 3100 ± 3400s, 2980m (CH), 1725s (COOR), 1645s,
1620s, 1530m, 1400s, 1370m, 1310s, 1255m, 1230m, 1145s, 1100m, 1060w,
700w; 1H NMR (300 MHz, CDCl3): d ˆ 1.17 (d, J ˆ 6.8 Hz, 3H, 2''-H3), 1.47,
1.50 (2s, 18H, 2tBu), approx. 1.47 ± 1.73 (m, 1H, 4'-HA), 1.82 ± 2.00 (m, 2H,
3'-HA, 4'-HB), 2.19 ± 2.38 (m, 1H, 3'-HB), 3.50 ± 3.83 (m, 5H, 3-H2, OCH3),
3.89 (m, 1H, 5'-H), 3.98 ± 4.11 (m, 3H, 1''-H, 2'''-H2), 4.38 (t, J ˆ 7.2 Hz, 1H,
2'-H), 4.47 (m, 1H, 2-H), 5.11 (s, 2H, CH2-Ph), 5.92 (d, J ˆ 7.2 Hz, 1H,
NHZ), 6.61 (d, J ˆ 8.7 Hz, 1H, N1''H), 7.16 (m, 1H, N3H), 7.30 ± 7.38 (m, 5H,
Ph), 8.91 (m, 1H, N1''''H), 11.37 (s, 1H, NHBoc); 13C NMR (75 MHz,
CDCl3): d ˆ 18.2 (C-2''), 27.9, 28.1 [2C(CH3)3, C-4'], 30.0 (C-3'), 41.0 (C-3),
44.8 (C-2'''), 47.6 (C-1''), 52.8 (OCH3), 54.2 (C-2), 67.1 (CH2-Ph), 78.6, 82.8
[2C(CH3)3], 79.5 (C-2'), 83.5 (C-5'), 127.9, 128.2, 128.5, 135.9 (Ph), 152.7
(MTBE); [a]D
ˆ
11.5, [a]578
ˆ
12.2, [a]546
ˆ
13.7, [a]436
ˆ
22.2,
[a]365
ˆ
31.6 (c ˆ 0.96, CHCl3, Tˆ 208C); IR (KBr): nÄ ˆ 3385brs,
3120m, 2980m (CH), 1715brs (COOR), 1525s, 1455m, 1400s, 1365m,
1250m, 1170m, 1060m, 780w, 740w, 700w, 615w; 1H NMR (300 MHz,
CDCl3): d ˆ 1.18 (d, J ˆ 6.4 Hz, 3H, 2''-H3), 1.44 (s, 9H, tBu), 1.71 ± 1.78 (m,
1H, 4'-HA), 1.81 ± 1.89 (m, 2H, 3'-HA, 4'-HB), 2.24 ± 2.39 (m, 1H, 3'-HB),
3.50 ± 3.82 (m, 6H, 3-H2, 1''-H, OCH3), 3.82 ± 3.96 (m, 1H, 5'-H), 4.38 (t, J ˆ
6.9 Hz, 1H, 2'-H), 4.42 (m, 1H, 2-H), 4.64 (brs, 1H, NHBoc), 5.12 (s, 2H,
CH2-Ph), 5.80 (d, J ˆ 6.8 Hz, 1H, NHZ), 7.07 (brs, 1H, N3H), 7.28 ± 7.42 (m,
5H, Ph); 13C NMR (75 MHz, CDCl3): d ˆ 18.9 (C-2''), 28.2 (C-4'), 28.4
[C(CH3)3], 30.2 (C-3'), 40.8 (C-3), approx. 49 (br, low intensity, C-1''), 52.8
(OCH3), 54.4 (C-2), 67.1 (CH2-Ph), 78.7 (C-2'), 79.4 [C(CH3)3], 83.4 (C-5'),
128.1, 128.3, 128.5, 136.0 (Ph), 155.7 (Z-CO, Boc-CO), 170.6 (CONH),
174.0 (COO); C24H35N3O8 (493.55): calcd C 58.41, H 7.15, N 8.51; found C
58.49, H 6.84, N 8.17.
ˆ
(C N), 156.1 (Z-CO, Boc-CO), 162.9 (Boc-CO), 168.0, 170.5 (2CONH),
173.8 (COO); C32H48N6O11 (692.76): calcd C 55.48, H 6.98, N 12.13; found C
55.38, H 7.12, N 11.54. The deprotection was done analogous to amide 14
starting from the corresponding guanidine derivative (300 mg,
0.433 mmol). After purification by preparative HPLC (6 runs, 21 mm ID,
Rainin, RP 18, 21.6 mLmin 1, 20% to 40% B within 20 min A: water‡
0.2% TFA; B: acetonitrile ‡ 0.2% TFA) and lyophylization the trifluor-
acetate of 59 (155 mg, 60%) was obtained as a white solid. HPLC: tR ˆ
9.3 min (Rainin, RP 18, 1 mLmin 1, 20% to 60% B within 20 min, A:
water‡ 0.2% TFA; B: acetonitrile ‡ 0.2% TFA); IR (neat): nÄ ˆ 2800 ±
(2S,2'R,5'S,1''S)-2-Benzyloxycarbonylamino-3-[5'-(1''-tert-butoxycarbonyl-
aminoethyl)-tetrahydrofuran-2'-carbamoyl] methyl propionate (66): The
preparation was done analogous to the preparation of amide 53 using the
following amounts of substrate and reagents: carboxylic acid 65 (1.30 g,
5.00 mmol), amine hydrochloride 27 (1.59 g, 5.50 mmol), HOBt (1.15 g,
7.50 mmol), EtN(iPr)2 (0.96 mL, 0.71 g, 5.5 mmol), and EDC (1.01 g,
5.25 mmol) to yield amide 66 (2.07 g, 84%) as a white solid. M.p. 608C;
ˆ
ˆ
3700s (NH; COOH), 1660brs (C O, C N), 1535m, 1400m, 1205m,
1135m, 1070w, 725w, 700w; 1H NMR (300 MHz, CD3CN): d ˆ 1.06 (brd,
J ˆ 6.4 Hz, 3H, 2''-H3), 1.42 ± 1.60 (m, 1H, 4'-HA), 1.69 ± 1.89 (m, 2H, 3'-HA,
4'-HB), 2.09 ± 2.23 (m, 1H, 3'-HB), 3.40 ± 3.64 (m, 2H, 3-H2), 3.79 ± 3.99 (m,
4H, 5'-H, 1''-H, 2'''-H2), 4.20 ± 4.35 (m, 2H, 2-H, 2'-H), 5.01 (s, 2H, CH2-
Ph), 6.45 (d, J ˆ 7.5 Hz, 1H, NHZ), 6.71 (brs, 4H*, two exchangeable H's),
7.04 ± 7.33 (m, 7H, N1''H, N1''''H, Ph), 7.54 (brs, 1H, N3H), 9.30 (brs, 3H,
three exchangeable H's); *this integral size was too large because the
sample contained approx. 1 equiv water. 13C NMR (75 MHz, CD3CN): d ˆ
17.7 (C-2''), 28.9 (C-4'), 31.1 (C-3'), 40.9 (C-3), 45.0 (C-2'''), 49.3 (C-1''), 55.0
(C-2), 67.4 (CH2-Ph), 79.1 (C-2'), 83.6 (C-5'), 128.6, 128.9, 129.4, 137.6 (Ph),
Rf ˆ 0.44 (MTBE); [a]D ˆ ‡29.8, [a]578 ˆ ‡31.1, [a]546 ˆ ‡35.5, [a]436
ˆ
‡61.8, [a]365 ˆ ‡101.6 (c ˆ 1.03, CHCl3, Tˆ 208C); IR (KBr): nÄ ˆ
ˆ
3360brs, 2980m (CH), 1725/1695s (4 Â C O), 1535s, 1455m, 1400m,
1365m, 1340m, 1250m, 1210m, 1170m, 1085m, 1060m, 775w, 700w, 610w;
1H NMR (300 MHz, CDCl3): d ˆ 1.02 (d, J ˆ 5.4 Hz, 3H, 2''-H3), 1.41 (s,
9H, tBu), superimposed by 1.30 ± 1.55 (m, 1H, 4'-HA), 1.82 ± 1.95, 2.07 ± 2.25
(m, 1H; m, 1H, 3'-HA, 4'-HB), 2.27 ± 2.42 (m, 1H, 3'-HB), 3.48 ± 3.89 (m, 7H,
3-H2, 5'-H, 1''-H, OCH3), 4.38 (brd, J ˆ 8.0 Hz, 1H, 2'-H), 4.48 (brs, 1H,
2-H), 5.00 ± 5.19 (m, 3H, CH2-Ph, NHBoc), 6.61 (d, J ˆ 7.0 Hz, 1H, NHZ),
7.22 ± 7.42 (m, 5H, Ph), 8.66 (brs, 1H, N3H); 13C NMR (75 MHz, CDCl3):
d ˆ 17.2 (C-2''), 28.1 [C(CH3)3], 28.3 (C-4'), 31.1 (C-3'), 40.3 (C-3), 51.1 (C-
1''), 52.1 (OCH3), 55.0 (C-2), 66.5 (CH2-Ph), 78.7 (C-2'), 79.5 [C(CH3)3],
85.9 (C-5'), 127.7, 127.8, 128.1, 136.2 (Ph), 156.1, 156.8 (Z-CO, Boc-CO),
170.6 (CONH), 175.2 (COO); C24H35N3O8 (493.55): calcd C 58.41, H 7.15, N
8.51; found C 58.38, H 7.05, N 8.25.
ˆ
157.4, 158.7 (Z-CO, C N), 168.4, 172.9 (2CONH), 176.1 (COO); ESI-MS:
[C22H33N6O7] calcd 479.23; found 479.19.
‡
{3'''-[N2'''',N3''''-Bis-(tert-Butoxycarbonyl)-guanidino]-propionyl}-
{(2'S,5'S,1''S)-5'-(1''-aminoethyl)-tetrahydrofuran-2'-carbonyl}-{(2S)-3-
amino-2-benzyloxycarbonylamino methyl propionate} (68): A solution of
dipeptide 64 (305 mg, 0.608 mmol) in CH2Cl2 (5 mL) was treated with TFA
(0.5 mL). After 4 h at room temperature the solvents were removed in
vacuo and the residue was codistilled with toluene (2 Â 5 mL). Sat. aqueous
NaHCO3 (6 mL) was added and extraction with EtOAc (2 Â 15 mL)
followed. The organic layer was washed with sat. aqueous NaCl (10 mL)
and dried with Na2SO4. After removal of the solvent in vacuo, the free
amine (240 mg, approx. 0.61 mmol) remained as slightly brownish oil which
was used without further purification. The crude amine, carboxylic acid 69
{N-(tert-Butoxycarbonyl)-glycyl}-{(2'S,5'S,1''S)-5'-(1''-aminoethyl)-tetrahy-
drofuran-2'-carbonyl}-{(2S)-3-amino-2-benzyloxycarbonylamino
methyl
propionate (67): The preparation was done analogous to amide 53 using
the following amounts of substrate and reagents: crude deprotected amine
64 (422 mg, approx. 1.07 mmol), Boc-glycine (234 mg, 1.33 mmol), HOBt
(298 mg, 1.95 mmol), EDC (255 mg, 1.54 mmol), and EtN(iPr)2 (0.21 mL,
0.16 g, 1.2 mmol). After CC (50 g, EtOAc followed by acetone/CH2Cl2 1:1)
amide 67 (553 mg, 94%) was obtained as a white solid. M.p. 618C; Rf ˆ 0.06
680
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0947-6539/00/0604-0680 $ 17.50+.50/0
Chem. Eur. J. 2000, 6, No. 4

Integrin Antagonists
666±683
b (303 mg, 0.914 mmol) and HOBt (184 mg, 1.20 mmol) were dissolved in
THF (5 mL) and EDC (176 mg, 0.918 mmol) was added at 08C. The
reaction mixture was allowed to warm to room temperature within 3 h.
After additional 2 h EtN(iPr)2 (0.11 mL, 79 mg, 0.61 mmol) was added. The
solution was stirred for an additional hour and then the solvent was
removed in vacuo. The residue was dissolved in EtOAc (20 mL). After
successive washings with 5% aqueous citric acid (5 mL), sat. aqueous
NaHCO3 (5 mL), and sat. aqueous NaCl (10 mL) the organic layer was
dried with Na2SO4. Removal of the solvent in vacuo and CC (30 g, EtOAc)
afforded amide 68 (325 mg, 75% based on 64) as a white solid. M.p. 78 ±
(C-2''), 28.2 [C(CH3)3], 28.6 (C-4'), 30.7 (C-3'), 40.6 (C-3), 44.6 (brC-2'''),
50.0 (C-1''), 52.4 (OCH3), 54.7 (C-2), 66.8 (CH2-Ph), 78.8 (C-2'), 85.1 (C-5'),
128.0, 128.4, 136.4 (Ph), 156.5 (Z-CO, Boc-CO), 171.0 (2CONH), 174.4
(COO); the signal for [C(CH3)3] was not detected.
{2'''-Guanidino-acetyl}-{(2'R,5'S,1''S)-5'-(1''-aminoethyl)-tetrahydrofuran-
2'-carbonyl}-{(2S)-3-amino-2-benzyloxycarbonylamino propionic acid} (60,
as a trifluoroacetate) via guanylation and deprotection: The guanylation
was done as described for the guanidine derivatives 55/56 using the
following amounts of substrate and reagents: Boc-protected amine 71
(321 mg, 0.583 mmol), TFA (2 mL); then isothiourea 54 (182 mg,
0.627 mmol), NEt3 (0.25 mL, 0.18 g, 1.8 mmol), and HgCl2 (188 mg,
0.692 mmol). CC (30 g, EtOAc) gave the corresponding guanidine
derivative (350 mg, 87% based on 71) as a colorless solid. M.p. 86 ± 878C;
828C; Rf ˆ 0.24 (EtOAc); [a]D
ˆ
6.6, [a]578
ˆ
6.9, [a]546
ˆ
7.8, [a]436
ˆ
12.6, [a]365
ˆ
16.6 (c ˆ 1.07, CHCl3, Tˆ 208C); IR (KBr): nÄ ˆ 3100 ±
3400brs, 2980w (CH), 1725s (COOR), 1640s, 1530m, 1400s, 1365m,
1330m, 1255m, 1230m, 1155m, 1135m, 1090w, 1060w; 1H NMR
(300 MHz, CDCl3): d ˆ 1.17 (d, J ˆ 6.8 Hz, 3H, 2''-H3), 1.48, 1.49 (2s,
18H, 2tBu), approx. 1.52 ± 1.66 (m, 1H, 4'-HA), 1.82 ± 1.98 (m, 2H, 3'-HA, 4'-
HB), 2.23 ± 2.37 (m, 1H, 3'-HB), 2.48 (t, J ˆ 6.7 Hz, 2H, 2'''-H2), 3.52 ± 3.82
(m, 7H, 3-H2, 3'''-H2, OCH3), 3.88 (m, 1H, 5'-H), 4.00 ± 4.12 (m, 1H, 1''-H),
4.36 (t, J ˆ 7.2 Hz, 1H, 2'-H), 4.48 (brdd, J ˆ 10.9 and 7.2 Hz, 1H, 2-H), 5.11
(s, 2H, CH2-Ph), 5.93 (d, J ˆ 7.2 Hz, 1H, NHZ), 6.34 (d, J ˆ 8.3 Hz, 1H,
N1''H), 7.18 (m, 1H, N3H), 7.30 ± 7.38 (m, 5H, Ph), 8.72 (t, J ˆ 5.9 Hz, 1H,
N1''''H), 11.44 (s, 1H, NHBoc); 13C NMR (75 MHz, CDCl3): d ˆ 18.3 (C-
2''), 28.0, 28.2 [2C(CH3)3], 28.4 (C-4'), 30.1 (C-3'), 36.2, 36.8 (C-2''', C-3'''),
41.0 (C-3), 47.7 (C-1''), 52.8 (OCH3), 54.2 (C-2), 67.1 (CH2Ph), 78.4, 82.8
[2C(CH3)3], 79.3 (C-2'), 83.2 (C-5'), 128.0, 128.2, 128.5, 135.9 (Ph), 152.8
Rf ˆ 0.34 (EtOAc); [a]D ˆ ‡59.4, [a]578 ˆ ‡62.0, [a]546 ˆ ‡71.3, [a]436
ˆ
‡128.6, [a]365 ˆ ‡220.1 (c ˆ 0.96, CHCl3, Tˆ 208C); IR (KBr): nÄ ˆ
3100 ± 3400m, 2980w (CH), 1725s (COOR), 1645s, 1550m, 1400s, 1370m,
1310m, 1230m, 1145s, 1095w, 1060w; 1H NMR (300 MHz, CDCl3): d ˆ 1.08
(d, J ˆ 6.8 Hz, 3H, 2''-H3), 1.48, 1.50 (2s, 18H, 2tBu), superimposed by
1.45 ± 1.55 (m, 1H, 4'-HA), 1.88 ± 2.01 (m, 1H, 4'-HB), 2.04 ± 2.34 (m, 2H, 3'-
H2), 3.72 (s, 3H, OCH3), 4.00 (d, J ˆ 5.5 Hz, 2H, 2'''-H2), superimposed by
3.62 ± 4.07 (m, 4H, 3-H2, 5'-H, 1''-H), 4.34 (dd, J ˆ 8.3, 3.4 Hz, 1H, 2'-H),
4.49 (m, 1H, 2-H), 5.11 (s, 2H, CH2-Ph), 6.93 (d, J ˆ 7.4 Hz, 1H, NHZ),
7.25 ± 7.38 (m, 5H, Ph), 7.65 (d, J ˆ 9.2 Hz, 1H, N1''H), 8.48 (brt, J ˆ 5.9 Hz,
1H, N3H), 8.82 (brt, J ˆ 5.4 Hz, 1H, N2'''H), 11.30 (s, 1H, NHBoc);
13C NMR (75 MHz, CDCl3): d ˆ 17.1 (C-2''), 28.0, 28.2 [2C(CH3)3], 28.6 (C-
4'), 30.7 (C-3'), 40.6 (C-3), 45.3 (C-2'''), 50.1 (C-1''), 52.4 (OCH3), 54.9 (C-2),
66.8 (CH2-Ph), 78.9 (C-2'), 79.5, 83.6 [2C(CH3)3], 85.3 (C-5'), 127.9, 128.0,
ˆ
(C N), 156.3 (Z-CO, Boc-CO), 163.4 (Boc-CO), 170.5 (2CONH), 173.9
(COO); ESI-MS: [C33H50N6O11‡H] calcd 707.36; found 707.35.
‡
ˆ
{3'''-Guanidino-propionyl}-{(2'S,5'S,1''S)-5'-(1''-aminoethyl)-tetrahydrofur-
an-2'-carbonyl}-{(2S)-3-amino-2-benzyloxycarbonylamino propionic acid}
(61, as a trifluoroacetate): The preparation was done analogous to amide 14
starting from tripeptide 68 (95 mg, 0.13 mmol). After purification by
preparative HPLC (3 runs, 21 mm ID, Rainin, RP 18, 21.6 mLmin 1, 20%
to 40% B within 20 min A: water‡ 0.2% TFA; B: acetonitrile ‡ 0.2%
128.4, 136.5 (Ph), 152.6 (C N), 156.4, 156.5 (Z-CO, Boc-CO), 162.6 (Boc-
CO), 169.9, 170.9 (2CONH), 174.7 (COO); C32H48N6O11 (692.76): calcd C
55.48, H 6.98, N 12.13; found C 55.26, H 7.14, N 12.15. The deprotection was
done analogous to amide 14 starting from the corresponding guanidine
derivative (210 mg, 0.303 mmol). After purification by preparative HPLC
(5 runs, 21 mm ID, Rainin, RP 18, 21.6 mLmin 1, 20% to 40% B within
20 min A: water ‡ 0.2% TFA; B: acetonitrile ‡ 0.2% TFA) and lyophy-
lization trifluoracetate of 60 (121 mg, 67%) was obtained as a white solid.
HPLC: tR ˆ 10.9 min (Rainin, RP 18, 1 mLmin 1, 20% to 60% B within
20 min, A: water‡ 0.2% TFA; B: acetonitrile ‡ 0.2% TFA); IR (neat):
TFA) and lyophylization the trifluoracetate of 61 (59 mg, 72%) was
1
obtained as a white solid. HPLC: tR ˆ 9.2 min (Rainin, RP 18, 1 mLmin
,
20% to 60% B within 20 min, A: water‡ 0.2% TFA; B: acetonitrile ‡
ˆ
0.2% TFA); IR (neat): nÄ ˆ 2800 ± 3700s (NH, COOH), 1660brs (C O,
C N), 1535m, 1400m, 1205m, 1135m, 1070w, 720w, 700w; 1H NMR
nÄ ˆ 2800 ± 3700s (NH; COOH), 1665brs (C O, C N), 1550m, 1400m,
1345m, 1205s, 1135s, 1070m, 1030w, 720w, 700w; 1H NMR (300 MHz,
CD3CN): d ˆ 1.07 (d, J ˆ 6.4 Hz, 3H, 2''-H3), 1.39 ± 1.51 (m, 1H, 4'-HA),
1.82 ± 1.97 (m, 1H, 4'-HB), 1.99 ± 2.25 (m, 2H, 3'-H2), 3.49 ± 4.11 (m, 6H,
3-H2, 5'-H, 1''-H, 2'''-H2), 4.20 ± 4.37 (m, 1H, 2'-H), 4.38 ± 4.52 (m, 1H, 2-H),
5.06 (s, 2H, CH2-Ph), 6.83 (brs, 4H*, 4 exchangeable H's), 7.20 ± 7.46 (m,
6H, Ph, N1''''H), 7.58 (d, J ˆ 8.3 Hz, 1H, N1''H), 8.30 (brs, 1H, N3H), 8.73
(brs, 2H*, 1 exchangeable H); *these integrals sizes were too large because
the sample contained some water; 13C NMR (75 MHz, CD3CN): d ˆ 17.2
(C-2''), 28.8 (C-4'), 31.3 (C- 3'), 41.1 (C-3), 45.1 (C-2'''), 50.9 (C-1''), 55.0 (C-
2), 67.4 (CH2-Ph), 79.2 (C-2'), 85.6 (C-5'), 128.5, 128.9, 129.1, 137.6 (Ph),
ˆ
ˆ
ˆ
(600 MHz, CD3CN): d ˆ 1.08 (d, J ˆ 7.5 Hz, 3H, 2''-H3), 1.51 ± 1.60 (m,
1H, 4'-HA), 1.78 ± 1.88 (m, 2H, 3'-HA, 4'-HB), 2.16 ± 2.23 (m, 1H, 3'-HB),
2.38 ± 2.48 (m, 2H, 2'''-H2), 3.33 ± 3.45 (m, 2H, 3'''-H2), AB signal (dA ˆ 3.51,
dB ˆ 3.59, JAB ˆ 14.0 Hz, additionally split by JA ˆ 5.1, 5.1 Hz, JB ˆ 7.0,
7.0 Hz, 2H, 3-H2), 3.89 ± 3.97 (m, 2H, 5'-H, 1''-H), 4.25 (dt, J ˆ 7.2, 5.0 Hz,
1H, 2-H), 4.32 (dd, J ˆ 7.6, 7.6 Hz, 1H, 2'-H), 5.07 (s, 2H, CH2-Ph), 5.40
(brs, 2H*, NH/COOH), 6.65 (d, J ˆ 7.5 Hz, 1H, NHZ), 7.03 (brs, 4H*, NH/
COOH), 7.10 (d, J ˆ 8.0 Hz, 1H, N1''H), 7.30 ± 7.38 (m, 5H, Ph), 7.51 (t, J ˆ
6.0 Hz, 1H, N3H), 7.68 (t, J ˆ 5.8 Hz, 1H, N1''''H); *these integrals sizes
were slightly too large because the sample contained approx. 0.5 equiv
water; 13C NMR (75 MHz, CD3CN): d ˆ 18.0 (C-2''), 28.9 (C-4'), 31.1 (C-
3'), 36.2 (C-2'''), 38.7 (C-3'''), 40.8 (C-3), 49.0 (C-1''), 55.6 (C-2), 67.2 (CH2-
Ph), 79.4 (C-2'), 83.7 (C-5'), 128.9, 129.1, 129.5, 138.0 (Ph), 157.3, 159.0 (Z-
ˆ
157.5, 158.3 (Z-CO, C N), 169.3, 173.2 (2CONH), 176.3 (COO); ESI-MS:
[C22H33N6O7] calcd 479.23; found 479.19.
‡
{3'''-[N2'''',N3''''-Bis-(tert-butoxycarbonyl)-guanidino]-propionyl}-
ˆ
CO, C N), 172.1, 173.3 (2CONH), 175.4 (COO); HRMS (FAB):
[C22H33N6O7] calcd 493.2411; found 493.2411.
{(2'R,5'S,1''S)-5'-(1''-aminoethyl)-tetrahydrofuran-2'-carbonyl}-{(2S)-3-
amino-2-benzyloxycarbonylamino methyl propionate} (72): The Boc
deprotection was done analogous to the deprotection of 64 using protected
amine 66 (300 mg, 0.608 mmol) as starting material. The deprotected amine
(230 mg, approx. 0.58 mmol) remained as slightly brownish oil which was
used without further purification. The peptide coupling was performed
according to the procedure described for the preparation of 53 without
using Hünigꢁs base: carboxylic acid 69b (211 mg, 0.664 mmol), HOBt
(133 mg, 0.869 mmol), and EDC (123 mg, 0.642 mmol). After CC [25 g,
CH2Cl2/PE 1:1 (200 mL) followed by EtOAc] amide 72 (145 mg, 35%
based on 66) was obtained as a white solid. As a major severe side reaction,
acid 69b cyclized to a six-membered heterocycle 70 [60 mg, 29%; NMR,
IR, MS, Rf ˆ 0.58 (MTBE)]. Amide 72: m.p. 91 ± 938C; Rf ˆ 0.25 (EtOAc);
[a]D ˆ ‡44.8, [a]578 ˆ ‡47.1, [a]546 ˆ ‡53.6, [a]436 ˆ ‡95.9, [a]365 ˆ ‡161.8
(c ˆ 1.16, CHCl3, Tˆ 208C); IR (KBr): nÄ ˆ 3100 ± 3400m, 2980w (CH),
1725brs (COOR), 1640s, 1560m, 1400m, 1370m, 1330m, 1255w, 1230w,
1155m, 1060w; 1H NMR (300 MHz, CDCl3): d ˆ 1.07 (d, J ˆ 6.4 Hz, 3H, 2''-
H3), 1.48, 1.49 (2s, 18H, 2tBu), 1.45 ± 1.55 (m, 1H, 4'-HA), 1.85 ± 1.99 (m,
1H, 4'-HB), 2.09 ± 2.38 (m, 2H, 3'-H2), 2.49 (brs, 2H, 2'''-H2), 3.55 ± 3.81 (m,
7H, 3-HA, 5'-H, 3'''-H2, OCH3), 3.86 ± 4.08 (m, 2H, 3-HB, 1''-H), 4.33 (brd,
‡
{N-(tert-Butoxycarbonyl)-glycyl}-{(2'R,5'S,1''S)-5'-(1''-aminoethyl)-tetra-
hydrofuran-2-carbonyl}-{(2S)-3-amino-2-benzyloxycarbonylamino methyl
propionate} (71): The preparation was done as described for amide 53
using the following amounts of substrate and reagents: crude deprotected
amine 66 (310 mg, approx. 0.788 mmol), Boc-glycine (160 mg, 0.913 mmol),
HOBt (199 mg, 1.30 mmol), EDC (171 mg, 0.89 mmol), and EtN(iPr)2
(0.14 mL, 0.11 g, 0.81 mmol). After CC (50 g, EtOAc followed by
acetone/CH2Cl2 1:1) the amide 71 (350 mg, 81%) was obtained as a white
solid. M.p. 638C; Rf ˆ 0.06 (EtOAc); [a]D ˆ ‡71.3, [a]578 ˆ ‡75.2, [a]546
ˆ
‡85.6, [a]436 ˆ ‡151.5, [a]365 ˆ ‡253.4 (c ˆ 1.08, CHCl3, Tˆ 208C); IR
(KBr): nÄ ˆ 3315brs, 2980m (CH), 1720s (COOR), 1660s, 1530s, 1455w,
1395m, 1365m, 1250m, 1170m, 1075w, 740w, 700w; 1H NMR (300 MHz,
CDCl3): d ˆ 1.10 (d, J ˆ 6.8 Hz, 3H, 2''-H3), 1.44 (s, 9H, tBu), superimposed
by 1.40 ± 1.60 (m, 1H, 4'-HA), 1.87 ± 2.02 (m, 1H, 4'-HB), 2.13 ± 2.33 (m, 2H,
3'-H2), 3.54 ± 4.06 (m, 9H, 3-H2, 5'-H, 1''-H, 2'''-H2, OCH3), 4.32 (dd, J ˆ 7.9,
3.8 Hz, 1H, 2'-H), 4.51 (m, 1H, 2-H), 5.13 (s, 2H, CH2-Ph), 5.39 (brs, 1H,
NHBoc), 6.51 ± 6.68 (m, 1H, N1''H), 7.01 (d, J ˆ 7.2 Hz, 1H, NHZ), 7.28 ±
7.40 (m, 5H, Ph), 8.33 (brs, 1H, N3H); 13C NMR (75 MHz, CDCl3): d ˆ 17.2
Chem. Eur. J. 2000, 6, No. 4
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
0947-6539/00/0604-0681 $ 17.50+.50/0
681

U. Koert et al.
FULL PAPER
J ˆ 8.3 Hz, 1H, 2'-H), 4.47 (m, 1H, 2-H), 5.11 (s, 2H, CH2-Ph), 6.97 (brd,
J ˆ 9.0 Hz, 1H, N1''H), 7.17 (brd, J ˆ 7.5 Hz, 1H, NHZ), 7.26 ± 7.38 (m, 5H,
Ph), 8.59 (brt, J ˆ 7.5 Hz, 1H, N3H), 8.66 (brt, J ˆ 7.7 Hz, 1H, N1''''H), 11.44
(s, 1H, NHBoc); 13C NMR (75 MHz, CDCl3): d ˆ 17.0 (C-2''), 28.0, 28.3
[2C(CH3)3], 28.6 (C-4'), 30.8 (C-3'), 36.6, 36.7 (C-2''', C-3'''), 40.4 (C-3), 50.3
(C-1''), 52.3 (OCH3), 55.0 (C-2), 66.7 (CH2-Ph), 78.9 (C-2'), 79.5, 83.3
Diefenbach, S. L. Goodman, A. Jonczyk, H. Kessler, J. Am. Chem.
Soc. 1996, 118, 7461 ± 7472.
[7] A. C. Bach II, J. R. Espina, S. A. Jackson, P. F. W. Stouten, J. L. Duke,
S. A. Mousa, W. F. DeGrado, J. Am. Chem. Soc. 1996, 118, 293 ± 294.
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ˆ
[2C(CH3)3], 85.3 (C-5'), 128.0, 128.1, 128.4, 136.5 (Ph), 152.8 (C N), 156.5
(Z-CO, Boc-CO), 163.2 (Boc-CO), 171.0, 172.4 (2CONH), 174.7 (COO);
‡
ESI-MS: [C33H50N6O11‡H] calcd 707.36; found 707.35.
{3'''-Guanidino-propionyl}-{(2'R,5'S,1''S)-5'-(1''-aminoethyl)-tetrahydro-
furan-2'-carbonyl}-{(2S)-3-amino-2-benzyloxycarbonylamino
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acid} (62, as trifluoroacetate): The preparation was done analogous to
amide 14 starting from tripeptide 72 (115 mg, 0.16 mmol). After purifica-
1
tion by preparative HPLC (3 runs, 21 mm ID, Rainin, RP 18, 21.6 mLmin
,
20% to 40% B within 20 min A: water‡ 0.2% TFA; B: acetonitrile ‡
0.2% TFA) and lyophylization trifluoracetate of 62 (78 mg, 79%) was
obtained as a white solid. HPLC: tR ˆ 9.6 min (Rainin, RP 18, 1 mLmin,
20% to 60% B within 20 min, A: water‡ 0.2% TFA; B: acetonitrile ‡
0.2% TFA); 1H NMR (600 MHz, CD3CN): d ˆ 1.02 (d, J ˆ 6.8 Hz, 3H, 2''-
H3), 1.40 (dddd, all J ꢀ 10 Hz, 1H, 4'-HA), 1.90 ± 1.95 (m, 1H, 4'-HB), 2.08 ±
2.20 (m, 2H, 3'-H2), 2.38 ± 2.54 (m, 2H, 2'''-H2), 3.27 ± 3.36 (m, 1H, 3'''-HA),
3.38 ± 3.44 (m, 1H, 3'''-HB), 3.47 (ddd, J ˆ 14.0, 3.9 and 3.9 Hz, 2H, 3-HA),
3.70 (ddd, J ˆ 9.0, 9.0, 5.9 Hz, 5'-H), 3.86 ± 3.95 (m, 2H, 3-HB, 1''-H), 4.27
(dd, J ˆ 8.5, 2.4 Hz, 1H, 2'-H), 4.40 (m, 1H, 2-H), AB signal (dA ˆ 5.05,
dB ˆ 5.09, JAB ˆ 12.4 Hz, 2H, CH2-Ph), 5.67 (brs, 4H*, exchangeable H's),
6.70 (brs, 4H*, exchangeable H's), 7.12 ± 7.38 (m, 8H, N1''H, NHZ, N3'''-H,
Ph), 8.49 (brdd, J ˆ 7.3, 4.2, 1H, N3H); *these integrals sizes were too large
because the sample contained approx. 1.5 equiv water; in addition a second
conformer/rotamer (approx. 10 mol-%) was detected, but these signals
were not reported above. 13C NMR (75 MHz, CD3CN): d ˆ 16.9 (C-2''),
28.8 (C-4'), 31.3 (C-3'), 35.6 (C-2'''), 38.3 (C-3'''), 40.9 (C-3), 51.0 (C-1''), 55.2
(C-2), 67.2 (CH2-Ph), 79.2 (C-2'), 86.1 (C-5'), 128.6, 128.8, 129.0, 137.6 (Ph),
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ˆ
157.3, 158.2 (Z-CO, C N), 173.1, 173.6 (2CONH), 176.1 (COO); HRMS
‡
(FAB): [C22H33N6O7] calcd 493.2411; found 493.2415.
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Molecular modeling studies: All THF-RGD mimics were investigated by
the following molecular modeling method:[40] One hundred stable con-
formers were generated for each compound by 500 ps molecular dynamics
calculation at 900 K, subsequent annealing to 300 K, and energy minimi-
zation using the CFF91 forcefield of Discover (Molecular Simulation Inc.,
San Diego, CA). To avoid overestimation of the electrostatic effect, we
adopted a distance dependent dielectric constant 4 Â R and assumed that
the Asp and Arg surrogates were not charged. All molecular modeling was
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1
less than 8 kcalmol above the minimum conformer were used for the
calculation of the individual conformer population according to
a
Boltzmann distribution (Tˆ 298 K).
Â
Á
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Acknowledgment
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This work was supported by Merck KGaA, the Deutsche Forschungs-
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ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
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Received: May 4, 1999 [F 1767]
Chem. Eur. J. 2000, 6, No. 4
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0947-6539/00/0604-0683 $ 17.50+.50/0
683