Structure-based organic synthesis of unnatural aeruginosin hybrids as potent inhibitors of thrombin

Article abstract of DOI:10.1016/j.bmcl.2007.03.075

Based on X-ray crystallographic data of complexes of chlorodysinosin A with the enzyme thrombin, a series of analogs were synthesized varying the nature of the P₁, P₂, and P₃ pharmacophoric sites and the central octahydroindole carboxyamide core. In general, introduction of a hydrophobic substituent on the d-leucine amide residue dramatically improved the inhibition of the enzyme. This is rationalized based on a better fit of the P₃ subunit in the hydrophobic S₃ enzyme site. Single digit nanomolar inhibition expressed as IC₅₀ was observed for several analogs.

Full text of DOI:10.1016/j.bmcl.2007.03.075

Bioorganic & Medicinal Chemistry Letters 17 (2007) 3480–3485
Structure-based organic synthesis of unnatural aeruginosin
hybrids as potent inhibitors of thrombin
Stephen Hanessian,a,* Karolina Ersmark,a Xiaotian Wang,a Juan R. Del Valle,a,
Niklas Blomberg,b Yafeng Xuec and Ola Fjellstro¨md
aDepartment of Chemistry, Universite´ de Montre´al, PO Box 6128, Station, Centre-Ville, Montre´al, QC, Canada H3C 3J7
bAstraZeneca R&D Mo¨lndal, Global Compound Sciences, 431 83 Mo¨lndal, Sweden
cAstraZeneca R&D Mo¨lndal, Structural Chemistry Laboratory, 431 83 Mo¨lndal, Sweden
dAstraZeneca R&D Mo¨lndal, Medicinal Chemistry, 431 83 Mo¨lndal, Sweden
Received 16 February 2007; revised 21 March 2007; accepted 23 March 2007
Available online 27 March 2007
Abstract—Based on X-ray crystallographic data of complexes of chlorodysinosin A with the enzyme thrombin, a series of analogs
were synthesized varying the nature of the P1, P2, and P3 pharmacophoric sites and the central octahydroindole carboxyamide core.
In general, introduction of a hydrophobic substituent on the D-leucine amide residue dramatically improved the inhibition of the
enzyme. This is rationalized based on a better fit of the P3 subunit in the hydrophobic S3 enzyme site. Single digit nanomolar
inhibition expressed as IC50 was observed for several analogs.
Ó 2007 Elsevier Ltd. All rights reserved.
The 20-plus members of the aeruginosin family of
potent serine protease inhibitors represent a relatively
new class of so-called linear peptides encompassing a
6-mono- or 5,6-dihydroxy 2-octahydroindole carboxam-
ide core unit (Choi and OHChoi, respectively).1 They
originate from geographically distinct aquatic sources
that contain cyanobacterial organisms from which they
can be isolated and characterized.2 Reported outbreaks
of livestock poisoning from contaminated water supplies
harboring these cyan-colored algal blooms3 attracted
attention to the aeruginosins which were found to be
non-toxic. Their structural novelty and interesting
in vitro activity against serine proteases involved in the
blood coagulation cascade leading to thrombus forma-
tion instigated structural studies with these enzymes,
as well as efforts toward their total syntheses.1 To date,
seven members of the aeruginosin family have been syn-
thesized, with four of these involving revisions to the
originally proposed structures.1 Potent in vitro activities
of dysinosin A,4 oscillarin,5 and chlorodysinosin A6
against thrombin and other factors in the intrinsic or
extrinsic pathways to blood coagulation have been
observed (Fig. 1).7 Nearly all the aeruginosins contain
a Choi or OHChoi central core unit upon which are
appended pharmacophoric subunits that confer affinity
to the catalytic binding pocket of trypsin, thrombin,
and other serine proteases in this class (Fig. 2). Thus,
a basic P1 and hydrophobic P2, P3 main pharmaco-
H
O
HN
H
HO
HO
O
N
HO
H
O
N
HN
N
H
NH
R
Ph
O
O
NH
N
NH2
H2N
NH
O
H2N
OH
OMe
OSO3
Dysinosin A, R = H
Thrombin IC50 = 0.046 μM
FVIIa IC50 = 0.326 μM
Oscillarin
Thrombin IC50 = 0.028 μM
FVIIa IC50 = 3.9 μM
Keywords: Thrombin inhibition; Aeruginosin mimics; Chloroleucine.
*
Chlorodysinosin A, R= Cl
Thrombin IC50 = 0.0057 μM
FVIIa IC50 = 0.039 μM
Corresponding author. Tel.: +1 514 343 6738; fax: +1 514 343
5728; e-mail: Stephen.hanessian@umontreal.ca
Present address: Department of Chemistry and Biochemistry, New
Mexico State University, 1175 N. Horseshoe Drive, MSC 3C Las
Cruses, NM 88003, USA.
Figure 1. Structures and enzymatic activities of the natural aerugino-
sins chlorodysinosin A, dysinosin A, and oscillarin.
0960-894X/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2007.03.075

S. Hanessian et al. / Bioorg. Med. Chem. Lett. 17 (2007) 3480–3485
3481
effect, we embarked on the synthesis of hybrid aerugino-
sins by segment coupling of natural and unnatural phar-
macophoric units representing the P1 and P3 units
anchored upon the perhydroindole carboxylic acid core.
Variations in the P1 subunit consisted of the ‘natural’ 1-
amidino-D3 pyrroline and agmatine groups, and the
unnatural 4-amidinobenzylamino group.9 The P3 sub-
unit was varied to include D-leucine, D-3R-chloroleu-
cine, D-isoleucine, and D-cyclohexyl glycine. The
perhydroindole carboxylic acid core consisted of
5-mono- and 5,6-dihydroxy analogs, as well as the
unsubstituted ‘unnatural’ variant. Finally, the ‘acidic’
appendage was patterned after oscillarin5 containing a
D-phenyllactic acid end-group, in addition to simpler
motifs. This provided a representative set of natural
and unnatural hybrid aeruginosin-like molecules to
probe the importance of each unit and functional group
in conferring inhibitory activity against thrombin as a
principal enzyme. Most anticipated was to validate the
beneficial ‘chlorine effect’ in selected analogs.
S
2
R2
R3
H
P
2
O
N
S
1
H
HN
R1
R4
S
O
3
P
3
P
1
NH
R5
Figure 2. Binding mode of the aeruginosin family according to X-ray
co-crystal structures complexed with thrombin.2d,5,6,8
phoric subunits are strategically deployed for optimal
binding.
The most recent entry in the family of aeruginosins,
namely chlorodysinosin A, exhibited the highest
in vitro inhibitory activity against thrombin (Factor
IIA) and Factor VIIA (IC50 = 5.7 and 39 nM, respec-
tively).6 Even more remarkable was the dramatic effect
of a chlorine atom present in the (2S,3R)-3-chloroleu-
cine subunit, harboring the hydrophobic side-chain
compared to dysinosin A which lacks the chlorine in
the same amino acid unit (IC50 thrombin, 46 nM; Factor
VIIA, 326 nM).4 X-ray co-crystal structure data of
chlorodysinosin A (2GDE)6 (and dysinosin A),2d as well
as molecular modeling6, delineated the possible reasons
for this remarkable ‘chlorine effect’ especially that the
inhibitors (and amino acid residues in the enzyme) did
not undergo major positional or conformational
changes. We have ascribed this unexpected ‘chlorine ef-
fect’ to a more restricted v1 angle, possibly positioning
the chlorine atom in a spacially favorable orientation
in the S3 pocket with a better entropic gain and associ-
ated with loss of water molecules.6 To validate this
The Choi core structure 2 was prepared from the pro-
tected L-glutamic acid 1 via dianion alkylation and azo-
nia-Prins halocarbocyclization, as previously described
(Scheme 1).5,10 The corresponding unsubstituted core
structure 10 in Scheme 2 was obtained quantitatively
from commercially available L-Oic (2-octahydroindole
carboxylic acid) using TMSCl in MeOH. In order to in-
stall the diversity in the last step of the syntheses, differ-
ent routes were taken to the final aeruginosin hybrids 6,
8, 9, 12–14, 16–18, and 20–24 as shown in Schemes 1 and
2. Depending on which side-chain was varied, P1 or P3,
the C- and N-terminal segments were coupled to the
azabicyclic core structures in different orders. Standard
peptide coupling conditions were used utilizing PyBOP
H
H
H
H
H
H
O
O
a,b
c,d
e-g
CO2Me
CO2Me
N
N
N
N
HN
HN
AcO
RO
TBSO
HO
Cbz
Cbz
Cbz
H
H
Cl
O
2
NH
NH
5
3: R = TBS
4: R = MOM
NBoc
NH
NH
O
BocHN
H2N
ref 5
h,i
H
OH
NHBoc
CO2Me
H
H
6
O
j-l
MeO2C
CO2Me
O
1
N
HN R
HO
N
MOMO
H
O
NH
NH
O
O
OH
OMOM
7
8: R = -(CH2)2
N
NH
H N
2
9: R = -(CH2)4NHCNHNH2
Scheme 1. Synthesis of aeruginosin analogs comprising the L-Choi subunit (6, 8, and 9). Reagents and conditions: (a) NaOMe, MeOH; (b) MOMCl,
DIEA, CH2Cl2 (99%, 2 steps) or TBSOTf, NEt3, CH2Cl2 (85%, 2 steps); (c) LiOH, H2O/THF, quant; (d) N2,N3-diBoc-agmatine,12 PyBOP,
2,6-lutidine, CH2Cl2, 84%; (e) H2, Pd(OH)2/C, EtOAc, 95%; (f) 29, DEPBT, 2,6-lutidine, CH2Cl2, 37%; (g) wet TFA/CH2Cl2 3:7–1:1, 61%; (h) H2,
Pd/C, MeOH, 95%; (i) 26, DEPBT, 2,6-lutidine, CH2Cl2, 84%; (j) LiOH, H2O/THF, 95%; (k) 2-(N,N0-diBoc-N-amidino-D3-pyrrolino)ethylamine4 or
N2,N3-diBoc-agmatine,12 PyBOP, 2,6-lutidine, CH2Cl2; (l) concd HCl (aq)/THF 1:1 (8, 37%, 2 steps) or wet TFA/CH2Cl2 9:1 (9, 51%, 2 steps).

3482
S. Hanessian et al. / Bioorg. Med. Chem. Lett. 17 (2007) 3480–3485
H
H
H
H
H
H
H
O
O
O
a-d
e
f
CO2Me
N
H
N
N
N
HN
HN
HN
H
H
O
O
10
15
g,h
NH
NH
k,l
O
O
NCbz
NCbz
NH
H
H
H
O
O
HN
H2N
H2N
H
O
i,j
O
23
CO2H
O
19
m-o
N
N
HN
R
N
HN
p
H
H
O
O
H
H
H
H
R
O
O
NH
OMOM
NH
NH
OH
O
O
O
NH
N
HN
N
HN
OH
HN
O
O
NH
NH2
O
NH
NH
R
H2N
H2N
Cl
24
12: R = -(CH2)2
OH
11
N
16: R =
NH
20: R =
H N
2
21: R = -CH3
13: R = -(CH2)4NHCNHNH2
17: R =
18: R =
NH
22: R = -(CH2)2
14: R = -CH2
NH
2
Scheme 2. Synthesis of aeruginosin analogs comprising the L-Oic subunit (12–14, 16–18, and 20–24). Reagents and conditions: (a) Boc2O, NEt3,
MeOH, 96%; (b) LiOH, H2O/THF, 86%; (c) N-Cbz-4-amino-methylbenzamidine, PyBOP, 2,6-lutidine, DMF, 89%; (d) TFA/CH2Cl2 1:9, 99%; (e) N-
Boc-D-isoleucine, DEPBT, 2,6-lutidine, CH2Cl2, 62%; (f) H2, Pd/C, MeOH, 73%; (g) 26, DEPBT, 2,6-lutidine, CH2Cl2, 71%; (h) LiOH, H2O/THF,
98%; (i) 2-(N,N0-diBoc-N-amidino-D3-pyrrolino)ethylamine,4 N-Cbz -4-amino-methylbenzamidine or N2,N3-diBoc-agmatine,12 PyBOP, 2,6-lutidine,
CH2Cl2 or DMF; (j) concd HCl (aq)/THF 1:1 (12, 46%, 2 steps, 13, 72%, 2 steps) or H2, Pd/C, MeOH then concd HCl (aq)/THF 1:1 (14, 61%, 3
steps); (k) 27, 28, or 29, DEPBT, 2,6-lutidine, CH2Cl2; (l) H2, Pd/C, MeOH, then wet TFA/CH2Cl2 9:1 (16, 30%, 3 steps, 17, 35%, 3 steps, and 18,
65%, 3 steps); (m) TFA/CH2Cl2 1:9, 91%; (n) D-lactic acid, PyBOP, 2,6-lutidine, CH2Cl2/DMF, or acetylchloride or hydrocinnamoylchloride, NEt3,
CH2Cl2; (o) H2, Pd/C, MeOH (20, 77%, 21, 70%, 22, 53%, over 2 steps); (p) TFA/CH2Cl2 1:9, 95%.
R
O
or DEPBT as coupling reagents and 2,6-lutidine as base.
PyBOP was used in the couplings of the basic C-termi-
nal P1 groups, while DEPBT was employed to install
the N-terminal segments (Schemes 1 and 2). DEPBT
was previously successfully employed in the amide cou-
pling between the OHChoi nitrogen and the N-terminal
segment in the synthesis of the ‘natural’ chlorodysinosin
A.6 The N-terminal end groups in hybrids 20–22 were
incorporated in the last step before deprotection, either
via PyBOP coupling with D-lactic acid to get 20, or via
direct coupling with the acid chlorides to obtain 21
and 22 (Scheme 2). Finally, global deprotection using
acidic conditions or hydrogenation followed by treat-
ment with acid afforded the target hybrids 6, 8, 9,
12–14, 16–18, and 20–24. Treatment with TFA in
dichloromethane resulted in a cleaner reaction com-
pared to concd HCl in THF. However, the Choi- and
OHChoi-containing hybrids had to be treated with
10% aq NaOH prior to purification on RP-HPLC in
order to saponify any trifluoroacetylated Choi-hydroxyls.11
COOH
OMOM
a,b
COOH
N
H
OMOM
25
26: R = -CH2CH(CH3)2
27: R =
28: R =
29: R =
Cl
Scheme 3. Synthesis of the N-terminal segments 26–29. Reagents and
conditions: (a) O-Bn-D-Leu, O-Me-D-Ile or O-Me-D-Chg, EDC,
HOBt, NEt3, CH2Cl2 or CH2Cl2/DMF or (2S,3R)-3-chloroleucinol,
PyBOP, 2,6-lutidine, CH2Cl2; (b) H2, Pd/C, MeOH (26, 94%, 2 steps)
or LiOH, H2O/THF (27, 82%, 2 steps, 28, 80%, 2 steps) or 0.4 M
H5IO6/wet MeCN, cat. CrO3, 0 °C (29, 51%, 2 steps).
pared by deprotection of the precursor 30 using TFA in
dichloromethane (Scheme 4).
A proline-containing hybrid 32 analogous to the Oic-hy-
brid 17 was synthesized as a reference compound to fully
investigate the effect of the size of the P2 subunit. The
same synthetic route as to hybrid 17 was employed
(Scheme 5).
The N-terminal segments 26–28 were prepared from the
MOM-protected D-phenyllactic acid 25 essentially as
previously reported (Scheme 3).5 The route to the
3-chloroleucine N-terminal segments 29 was prepared
similarly as in the synthesis of chlorodysinosin A,6 with
oxidation to the carboxylic acid in the last step using
The aeruginosin hybrids 6, 8, 9, 12–14, 16–18, 20–24, 31,
and 32 were evaluated in enzymatic assays for their
inhibitory activity against thrombin. The results are pre-
sented as IC50 values in Table 1.14 Activities ranging
from low nanomolar to micromolar IC50 values were
obtained depending on the specific combination of
P1–P3 pharmacophoric subunits.15 In accordance with
13
H5IO6 and cat. CrO3 (Scheme 3).
In an effort to investigate the impact of the acidic sulfate
group in chlorodysinosin A the non-sulfated 31 was pre-

S. Hanessian et al. / Bioorg. Med. Chem. Lett. 17 (2007) 3480–3485
3483
H
H
thrombin inhibitor of the natural aeruginosins and
the aeruginosin-derived analogs reported to date
(IC50 = 0.0016 lM, Table 1). Hybrids 17 and 18 encom-
passing a D-isoleucine or D-cyclohexyl glycine in the P3
position demonstrated activities against thrombin in
the same low nanomolar range confirming a strong pref-
erence for b-branched P3 side-chains. Molecular dynam-
ics simulations indicate that this so-called ‘chlorine
effect’ primarily originates from a stabilization by the
b-substituent of the v1 angle in the bioactive conforma-
tion rather than from a general hydrophobic effect,
which is also reflected by the similar clogP values of
the hybrids with and without a b-chloro substituent
(cf. 9, clogP = 0.296 with 6, clogP = 0.359 and 14,
clogP = 3.91 with 16, clogP = 3.97).17 Moreover, the
bioactive conformation places the b-substituent in a
favorable position in the S3 subsite resulting in a release
of water and thus a gain in entropy as well as additional
hydrophobic interactions with the enzyme pocket.
According to the contour diagram in Figure 3 there
seems to be enough space in the S3 subsite to accommo-
date even larger b-substituents in aeruginosin hybrids.
Futhermore, D-phenylalanine appears to be preferred
over D-leucine in the P3 position. Compound 8, which
is the P3 D-leucine hybrid of the natural oscillarin, was
less potent than the D-phenylalanine-containing natural
product (IC50 = 0.22 and 0.028 lM against thrombin,
respectively).
MOMO
MOMO
O
N
HN
Cl
O
N
NBoc
NH
O
BocHN
OMe
30
OTBDPS
a
H
HO
HO
O
N
HN
H
Cl
O
N
NH
NH
O
H2N
OMe
31
OH
Scheme 4. Synthesis of non-sulfated chlorodysinosin A 31. Reagents:
(a) wet TFA/CH2Cl2 9:1, 95%.
O
N
a-d
HN
N-Boc-L-proline
O
NH
O
NH
H2N
OH
The oscillarin D-phenyllactic acid was chosen as a gen-
eral N-terminal appendage in this series of hybrids.
Oscillarin, which is lacking an N-terminal acidic group,
is one of the most active thrombin inhibitors of the nat-
ural aeruginosins (Fig. 1).5 The avoidance of an acidic
group was considered favorable both from synthetic
and ADME perspectives. It was also found that the gain
in activity due to an N-terminal acidic group appears to
be very modest. A comparison between the non-sulfated
chlorodysinosin A 31 and chlorodysinosin A shows only
a slight increase in activity against thrombin with a sul-
fate end group (IC50 = 0.0057 and 0.011 lM, respec-
tively). D-Phenyllactic acid was found to be superior to
other simpler N-terminal end groups (cf. compound 17
with 20–24, Table 1). The loss in inhibitory activity
was more pronounced when omitting the hydroxyl than
the terminal phenyl group, cf. 22 and 20. A complete
truncation of the N-terminal appendage resulted in
amine 24, which still demonstrated significant activity
against thrombin (IC50 = 0.101 lM, Table 1).
32
Scheme 5. Synthesis of L-proline-containing aeruginosin analog 32.
Reagents and conditions: (a) N-Cbz-4-amino-methylbenzamidine,
PyBOP, 2,6-lutidine, DMF, 93%; (b) TFA/CH2Cl2 1:9, quant.; (c)
27, DEPBT, 2,6-lutidine, CH2Cl2/DMF, 70%; (d) H2, Pd/C, MeOH,
then wet TFA/CH2Cl2 9:1 (82%, 2 steps).
previous observations,1 the shape and orientation of the
basic P1 side-chain was found to be of vital importance
for high inhibitory activity. In general, the 4-amidinob-
enzyl group was preferred in the P1 position over
agmatine and 1-amidino-D3 pyrroline (cf. 12, 13, and
14, Table 1).
The azabicyclic P2 subunit has mainly been suggested as
a device conferring the bioactive conformation in the
aeruginosin-like molecules. Apparently, the 6-hydroxyl
of Choi makes no difference for the inhibitory activity
when comparing to the unsubstituted Oic-hybrids (cf.
8 vs 12 and 13 vs 9, Table 1). In fact even slightly
improved activities were obtained without the 6-hydro-
xyl against thrombin. The activity of the proline hybrid
32 was noteworthy.16
The comparatively stronger inhibition of compound 6
than its des-chloro analog 9 suggests that the structure
of aeruginosin 205B should be revised, with the chloro
atom on the D-leucine residue, rather than on Choi.18
In conclusion, a series of unnatural aeruginosin hybrids
have been synthesized to map the structure–activity
relationships of the P1, P2, P3, and the N-terminal sub-
units against thrombin. A pronounced increase in
activity was found when incorporating a b-substituent
on the P3 side-chain, establishing the previously
acknowledged ‘chlorine effect’ of the D-3R-chloroleucine
in chlorodysinosin A.
Encouraged by the remarkable effect of a 3R-chloro sub-
stituent in the P3 side-chain (cf. 6 vs 9, Table 1) a series
of b-branched hybrids 16, 17, and 18 incorporating the
most potent 4-amidinobenzyl P1 group and the unsubsti-
tuted Oic P2 subunit were prepared and evaluated. To
the best of our knowledge the D-3R-chloroleucine
hybrid 16 identified in this small series is the most active

3484
S. Hanessian et al. / Bioorg. Med. Chem. Lett. 17 (2007) 3480–3485
Table 1. Inhibition of thrombin measured as IC50 values
H
H
R2
R3
O
R1
N
HN
O
R4
NH
R5
Compound
R1
R2
H
R3
R4
R5
IC50 (lM)
Thrombin
O
O
O
O
O
O
O
O
O
O
NH
N
N
8
OH
H
0.22
NH2
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
NH
12
H
H
H
H
H
H
H
0.12
NH2
NH
14
H
0.097
1.5
NH2
H
N
NH
NH
13
H
NH2
H
N
9
OH
OH
H
5.6
NH2
H
N
Cl
Cl
NH
NH2
6
0.31
NH
NH2
16
0.0016
0.0033
0.007
0.0034
0.101
0.786
0.053
0.334
0.171
0.011
NH
NH2
17
H
NH
NH2
32 L-proline
-(L-proline)
-(L-proline)
NH
NH2
18
24
21
20
22
23
31
H
H
NH
NH2
H
H
H
O
O
NH
NH2
H
H
NH
NH2
H
H
OH
O
NH
NH2
H
H
O
O
NH
H
H
O
NH2
Cl
NH
NH2
N
OH
OH
OH
OMe

S. Hanessian et al. / Bioorg. Med. Chem. Lett. 17 (2007) 3480–3485
3485
124, 13340, The herein reported dysinosin A-thrombin
X-ray crystal structure has to the best of our knowledge
not been deposited in the protein data bank (PDB).
Chlorodysinosin A.; Goetz, G. H.; Harrigan, G. G.;
Likos, J. J.; Kasten, T. P. Patent WO03/051831, 2003.
3. Carmichael, W. W. Sci. Am. 1994, 270, 78.
4. Hanessian, S.; Margarita, R.; Hall, A.; Johnstone, S.;
Tremblay, M.; Parlanti, L. J. Am. Chem. Soc. 2002, 124,
13342.
5. Hanessian, S.; Tremblay, M.; Petersen, J. F. W. J. Am.
Chem. Soc. 2004, 126, 6064.
6. Hanessian, S.; Del Valle, J. R.; Xue, Y.; Blomberg, N. J.
Am. Chem. Soc. 2006, 128, 10491.
7. For reviews on thrombin inhibitors, see Srivastava, S.;
Goswami, L. N.; Dikshit, D. K. Med. Res. Rev. 2005, 25,
66; Scarborough, R. M.; Pandey, A.; Zhang, X. Ann. Rep.
Med. Chem. 2005, 40, 85; Pfau, R. Curr. Opin. Drug
Discov. Devel. 2003, 6, 437; Leung, D.; Abbenante, G.;
Fairlie, D. P. J. Med. Chem. 2000, 43, 305; Babine, R. E.;
Bender, S. L. Chem. Rev. 1997, 97, 1359.
8. Rios Steiner, J. L.; Murakami, M.; Tulinsky, A. J. Am.
Chem. Soc. 1998, 120, 597.
Figure 3. Contour diagram of the S3 pocket and the P3 side-chains
from an overlay of the co-crystal structures of dysinosin A2d (green)
and chlorodysinosin A6 (2GDE, pink) with thrombin.
9. See for example Hanessian, S.; Balaux, E.; Musil, D.;
Olsson, L.-L.; Nilsson, I. Bioorg. Med. Chem. Lett. 2000,
10, 243.
10. Hanessian, S.; Tremblay, M.; Marzi, M.; Del Valle, J. R.
J. Org. Chem. 2005, 70, 5070.
Acknowledgments
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We thank NSERC and AstraZeneca for financial sup-
port. We also acknowledge the continued support from
AstraZeneca for biological testing, molecular modeling,
protein crystallography, and stimulating discussions
with Ingemar Nilsson, Ola Fjellstro¨m, Niklas Blomberg,
and Yafeng Xue. Karolina Ersmark is grateful for a
postdoctoral fellowship from IF’s Foundation for Phar-
maceutical Research (Stockholm, Sweden).
References and notes
15. Inhibition of trypsin was measured for 8 (IC50 = 0.36 lM),
12
(IC50 = 0.090 lM), and 16 (IC50 = 0.0063 lM).14
16. For other proline-based aeruginosin analogs, see Radau,
(IC50 = 0.37 lM),
13
(IC50 = 0.12 lM),
14
1. Ersmark, K.; Del Valle, J. R.; Hanessian, S. Angew. Chem.
Int. Ed., in press.
G.; Sturzebecher, J. Pharmazie 2002, 57, 729; Radau, G.;
2. See for example: Aeruginosin 298A (a) Murakami, M.;
Okita, H.; Matsuda, H.; Okino, T.; Yamaguchi, K.
Tetrahedron Lett. 1994, 35, 3129, Oscillarin; (b) Kon-
etschny-Rapp, S.; Krell, H.-W.; Martin, U. Patent WO96/
11941, 1996. Aeruginosins 205A and 205B; (c) Shin, H. J.;
Matsuda, H.; Murakami, M.; Yamaguchi, K. J. Org.
Chem. 1997, 62, 1810, Dysinosin A; (d) Carroll, A. R.;
Pierens, G. K.; Fechner, G.; de Almeida Leone, P.; Ngo,
A.; Simpson, M.; Hyde, E.; Hooper, J. N. A.; Bostrom,
S.-L.; Musil, D.; Quinn, R. J. J. Am. Chem. Soc. 2002,
¨
Rauh, D. Bioorg. Med. Chem. Lett. 2000, 10, 779; Radau,
G.; Gebel, J.; Rauh, D. Arch. Pharm. Pharm. Med. Chem.
2003, 336, 372.
17. ClogP values were obtained with the same value from
BioByte and ChemDraw.
18. Valls, N.; Vallribera, M.; Font-Bardia, M.; Solans, X.;
Bonjoch, J. Tetrahedron: Asymmetry 2003, 14, 1241; Valls,
´
N.; Borregan, M.; Bonjoch, J. Tetrahedron Lett. 2006, 47,
3701.